DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERINGeie.uonbi.ac.ke/sites/default/files/cae/engineering/eie... ·  · 2015-06-29DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING

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UNIVERSITY OF NAIROBI

DEPARTMENT OF ELECTRICAL AND INFORMATION

ENGINEERING

DESIGN OF A PWM BASED DC MOTOR CONTROL FOR ELECTRIC

VEHICLE USING A MICROCONTROLLER

PROJECT INDEX: PRJ 82

BY

TOWETT FESTUS KIPNGENO

REGISTRATION NO. : F17/30740/2010

SUPERVISOR: MR. OMBURA

EXAMINER: PROF. MANGOLI

Project report submitted in partial fulfillment of the requirement for the award of the degree of:

Bachelor of Science in Electrical and Electronic Engineering of the University of Nairobi.

Submitted on: 24th day of April, 2015

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DEDICATION To my family, for believing in me.

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DECLARATION OF ORIGINALITY

FACULTY/ SCHOOL/ INSTITUTE: Engineering

DEPARTMENT: Electrical and Information Engineering

COURSE NAME: Bachelor of Science in Electrical & Electronic Engineering

TITLE OF NAME OF STUDENT: Towett Festus Kipngeno

REGISTRATION NUMBER: F17/30740/2010

COLLEGE: Architecture and Engineering

WORK: DESIGN OF A PWM BASED DC MOTOR CONTROL FOR ELECTRIC VEHICLE

USING A MICROCONTROLLER

1) I understand what plagiarism is and I am aware of the university policy in this regard.

2) I declare that this final year project report is my original work and has not been

submitted elsewhere for examination, award of a degree or publication. Where other

people’s work or my own work has been used, this has properly been acknowledged

and referenced in accordance with the University of Nairobi’s requirements.

3) I have not sought or used the services of any professional agencies to produce this work.

4) I have not allowed, and shall not allow anyone to copy my work with the intention of

passing it off as his/her own work.

5) I understand that any false claim in respect of this work shall result in disciplinary

action, in accordance with University anti-plagiarism policy.

Signature: ………………………………………………………………………………………

Date: ……………………………………………………………………………………………

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ACKNOWLEDGEMENT

This is an honor for me to thank those who have helped to make this report possible.

First of all I would like to pay my deepest gratitude to my supervisor, Mr. Ombura for

giving me the opportunity to work on this project under his supervision. His support,

guidance and encouragement from the initial stage to the end has enabled me to

understand the concept behind this thesis work. I also express my gratitude to all the

faculty members and lab technologist for their guidance and support. Finally, all the

thanks to Almighty GOD that I have come to this far.

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Table of Contents

DEDICATION ......................................................................................................................................................... ii

DECLARATION OF ORIGINALITY .............................................................................................................. iii

ACKNOWLEDGEMENT ....................................................................................................................................iv

TABLE OF FIGURES ......................................................................................................................................... vii

ABSTRACT .............................................................................................................................................................. 1

1 INTRODUCTION.......................................................................................................................................... 2

1.1 APPLICATION OF ELECTRIC TRACTION ................................................................................. 3

1.1.1 ELECTRIC TRAIN ........................................................................................................................ 3

1.1.2 ELECTRIC MOTORCYCLES ..................................................................................................... 3

1.1.3 ELECTRIC ELEVATOR .............................................................................................................. 4

1.2 PROBLEM STATEMENT .................................................................................................................. 4

1.3 ADVANTAGES OF ELECTRIC TRACTION ................................................................................. 5

1.4 DISADVANTAGES OF ELECTRIC VEHICLES ........................................................................... 6

1.5 OBJECTIVE ............................................................................................................................................. 7

2 LITERATURE REVIEW ............................................................................................................................. 8

2.1 CLASSIFICATION OF ELECTRIC VEHICLE ............................................................................... 8

2.1.1 Hybrid drive ................................................................................................................................. 8

2.1.2 ELECTRIC DRIVE (EV) .......................................................................................................... 12

2.2 DIRECT CURRENT MOTOR ......................................................................................................... 15

2.2.1 CLASSIFICATION OF A DC MOTORS ............................................................................... 16

2.2.2 CLASSIFICATION ON BASIS OF EXCITATION WINDING ....................................... 16

3 DESIGN ........................................................................................................................................................ 24

3.1 HARDWARE DEVELOPMENT .................................................................................................... 24

3.1.1 H-BRIDGE ................................................................................................................................... 25

3.1.2 CONTROL SYSTEM ................................................................................................................. 32

3.1.3 MICROCONTROLLER ............................................................................................................. 35

3.1.4 LCD DISPLAY UNIT ................................................................................................................. 36

3.1.5 INPUT UNIT ............................................................................................................................... 37

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3.1.6 DC MOTOR.................................................................................................................................. 37

3.1.7 POWER SUPPLY ....................................................................................................................... 38

3.1.8 CIRCUIT PROTECTION ......................................................................................................... 39

3.2 SOFTWARE DESIGN ....................................................................................................................... 40

4 RESULTS ..................................................................................................................................................... 44

4.1 SIMULATION ..................................................................................................................................... 44

4.1.1 CIRCUIT DIAGRAM ................................................................................................................. 44

4.1.2 CIRCUIT DESCRIPTION ........................................................................................................ 45

4.2 SIMULATION RESULTS ................................................................................................................. 46

4.2.1 POWER SUPPLY OUTPUT.................................................................................................... 46

4.2.2 MICROCONTROLLER OUTPUTS ....................................................................................... 46

4.2.3 LCD DISPLAY ............................................................................................................................. 47

4.2.4 H-BRIDGE OUTPUTS.............................................................................................................. 48

4.3 EXPERIMENTAL RESULT ............................................................................................................ 50

4.3.1 MICROCONTROLLER OUTPUT WHEN IN FORWARD MODE .............................. 51

4.3.2 OUTPUT WHEN THE CAR IS MOVING FORWARD ................................................... 52

4.3.3 OUTPUT WHEN REVERSE DRIVING ............................................................................... 53

5 CONCLUSION ............................................................................................................................................ 54

REFERENCES ..................................................................................................................................................... 55

APPENDIX ............................................................................................................................................................ 57

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TABLE OF FIGURES Figure 2.1 classification of hybrid electric vehicles .............................................................................................. 10

Figure 2.2primary electric vehicle power train ..................................................................................................... 12

Figure 2.3 conceptual illustration of general ev configuration ...................................................................... 13

Figure 2.4 possible ev configurations ......................................................................................................................... 15

Figure 2.5 types of dc motors ......................................................................................................................................... 17

Figure 2.6 permanent magnet dc motor and curves ............................................................................................ 18

Figure 2.7 shunt wound dc motor and curve ........................................................................................................... 19

Figure 2.8 series dc motor ............................................................................................................................................... 21

Figure 3.1 block diagram ................................................................................................................................................. 25

Figure 3.2 h-bridge ............................................................................................................................................................. 25

Figure 3.3 h-bridge switch configuration ................................................................................................................. 26

Figure 3.4 regenerative braking ................................................................................................................................... 27

Figure 3.5 ir2110 connection ......................................................................................................................................... 30

Figure 3.6 series gate resistance vs. Amplitude of negative voltage spike and turn-off time ............. 32

Figure 3.7 pwm signal ....................................................................................................................................................... 34

Figure 3.8 examples of pwm signal.............................................................................................................................. 35

Figure 3.9 16x2 lcd display .............................................................................................................................................. 37

Figure 3.10 voltage regulator circuit ........................................................................................................................ 39

Figure 3.11 flow chart ....................................................................................................................................................... 42

Figure 4.1 circuit diagram .............................................................................................................................................. 44

Figure 4.2 voltage regulator output ........................................................................................................................... 46

Figure 4.3 forward drive microcontroller output ................................................................................................. 46

Figure 4.4 forward driving lcd display ....................................................................................................................... 47

Figure 4.5 reverse driving lcd display ......................................................................................................................... 47

Figure 4.6 regenerative braking lcd display ............................................................................................................ 48

Figure 4.7 h-bridge output forward mode................................................................................................................ 48

Figure 4.8 h-bridge output reverse mode ................................................................................................................. 49

Figure 4.9 breadboard constructed circuit .............................................................................................................. 50

Figure 4.10 pwm signal generated by microcontroller ...................................................................................... 51

Figure 4.11 h-bridge output using oscilloscope ..................................................................................................... 52

Figure 4.12 lcd and leds output ..................................................................................................................................... 52

Figure 4.13 h-bridge output reverse driving ........................................................................................................... 53

Figure 4.14 lcd and led output ....................................................................................................................................... 53

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ABSTRACT

The aim of this project is to design and implement a power controller based on a

microcontroller to be used in controlling a DC motor driving an electric vehicle. The

ease of control and excellent performance of the DC motors will ensure that it is widely

used in many applications. This project is mainly concerned on DC motor speed control

system by using microcontroller PIC 16F877A. Pulse Width Modulation (PWM)

technique is used where its signal is generated in microcontroller. The program for

PWM generation is written in C Language using MIKROC software. It is programmed

into the microcontroller using Pickit 2. Then the microcontroller is installed into the

motor control circuit. The Microcontroller acts as the motor speed controller in this

project. Based on the result, the readings are quite reliable. Through the project, it can

be concluded that microcontroller PIC 16F877A can control motor speed at desired

speed efficiently by using Pulse Width Modulation signal.

Keywords: DC motor, Microcontroller, Pulse Width Modulation.

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1 INTRODUCTION Electro mobility has always been an issue that has helped drive the development of

vehicles. It did become less important for a while because the oil fields did not appear

to be drying up, but now electro mobility is becoming increasingly significant as people

become aware of the depletion of oil reserves and the need for of global environmental

and climate protection.

The present discussion on the CO2 emissions of passenger cars gives a new stimulus to

electric traction drives. At least for city travel the fuel consumption and consequently

the CO2 emissions can be reduced by applying a concept containing electric traction. By

electric traction is meant locomotion in which the driving (or tractive) force is obtained

from electric motors. It is used in electric trains, tramcars, trolley buses and diesel-

electric vehicles etc. [1]

The development of internal combustion engine vehicles, especially automobiles, is one

of the greatest achievements of modern technology. Automobiles have made great

contributions to the growth of modern society by satisfying many of its needs for

mobility in everyday life. The rapid development of the automotive industry, unlike that

of any other industry, has prompted the progress of human society from a primitive one

to a highly developed industrial society. However, the large number of automobiles in

use around the world has caused and continues to cause serious problems for the

environment and human life. Air pollution, global warming, and the rapid depletion of

the Earth’s petroleum resources are now problems of paramount concern.

At present, all vehicles rely on the combustion of hydrocarbon fuels to derive the

energy necessary for their propulsion. Combustion is a reaction between the fuel and

the air that releases heat and combustion products. The heat is converted to mechanical

power by an engine and the combustion products are released into the atmosphere [2].

A hydrocarbon is a chemical compound with molecules made up of carbon and

hydrogen atoms. Ideally, the combustion of a hydrocarbon yields only carbon dioxide

and water, which do not harm the environment. But the combustion of hydrocarbon

fuel in combustion engines is never ideal. Besides carbon dioxide and water, the

combustion products contain a certain amount of nitrogen oxides (NO), carbon

monoxides (CO), and unburned hydrocarbons (HC), all of which are toxic to human

health.

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1.1 APPLICATION OF ELECTRIC TRACTION

Over the years study and research of electric traction have intensified and its

application be used in many different ways such as electric vehicle, electric train,

electric motorcycles and electric traction elevators.

1.1.1 ELECTRIC TRAIN

The railway as a means of transport is a very old idea. At its beginnings, it was mainly

utilized in the central European mines with different means of traction being applied.

But it did not come into general use until the invention of the steam engine. Since the

18th century it has developed faster and faster until in the 21st century it has become

the most efficient means of transport for medium distances thanks to the development

of High Speed. Railway electrification as a means of traction emerged at the end of the

nineteenth century, although experiments in electric rail have been traced back to the

mid-nineteenth century [3].

An electric locomotive is a locomotive powered by electricity from overhead lines, a

third rail or an on-board energy storage device (such as a chemical battery or fuel cell).

Electrically propelled locomotives with on-board fuelled prime movers, such as diesel

engines or gas turbines, are classed as diesel-electric or gas turbine electric locomotives

because the electric generator/motor combination only serves as a power transmission

system. Electricity is used to eliminate smoke and take advantage of the high efficiency

of electric motors; however, the cost of railway electrification means that usually only

heavily-used lines can be electrified.

Electric locomotives benefit from the high efficiency of electric motors, often above

90% [4]. Additional efficiency can be gained from regenerative braking, which allows

kinetic energy to be recovered during braking to put some power back on the line.

Newer electric locomotives use AC motor-inverter drive systems that provide for

regenerative braking.

1.1.2 ELECTRIC MOTORCYCLES

Electric motorcycles, though still in their infancy, are starting to gain a foothold in the

marketplace. Most electric motorcycles and scooters today are powered by

rechargeable lithium ion batteries, though some early models used nickel-metal

hydride batteries. As technology improves and costs of battery starts to come down it is

most likely that more and more of electric motorcycle will be manufactured.

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As it stands now, the biggest hurdle for electric motorcycles is range. Since batteries

cannot store as much energy as a tank of gas. Anything over 130 miles (210 km) on a

single charge is considered an exceptionally long range [5]. As a result, while electric

machines excel as daily commuters traveling a fixed distance round trip, on the open

road riders experience inhibiting range anxiety. Also electric power trades off range

against speed. For instance the current longest range electric scooter, the ZEV 10 LRC,

travels 220 km (140 mi) at 89 km/h (55 mph), but according to the manufacturer the

range drops to about 129 km (80 mi) at 112 km/h (70 mph) [6].

However, Electric scooters and motorcycles need virtually no maintenance and therefor

charge up and maintenance costs should also be lower.

1.1.3 ELECTRIC ELEVATOR

An elevator is essentially a platform that is either pulled or pushed up by a mechanical

means to efficiently move people or goods between floors of a building or other

structure. Elevators are generally powered by electric motors that either drive traction

cables or counterweight systems like a hoist, or pump hydraulic fluid to raise a

cylindrical piston like a jack [7].

In the past, elevator drive mechanisms were powered by steam and water hydraulic

pistons or by hand. In a "traction" elevator, cars are pulled up by means of rolling steel

ropes over a deeply grooved pulley, commonly called a sheave in the industry. The

weight of the car is balanced by a counterweight. Sometimes two elevators are built so

that their cars always move synchronously in opposite directions, and are each other's

counterweight [7].

The technology used in new installations depends on a variety of factors. Hydraulic

elevators are cheaper, but installing cylinders greater than a certain length becomes

impractical for very-high lift hoist ways. For buildings of much over seven stories,

traction elevators must be employed instead. Hydraulic elevators are usually slower

than traction elevators.

1.2 PROBLEM STATEMENT

Electric vehicles are significantly more expensive than conventional internal

combustion engine vehicles and hybrid electric vehicles due to the additional cost of

their lithium-ion battery pack [8]. However, battery prices are coming down with mass

production and are expected to drop further. Another challenge of internal combustion

engines vehicles is the level they produce air pollution emissions, due to incomplete

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combustion of carbonaceous fuel. The main derivatives of the process are carbon

dioxide CO2, water and some soot — also called particulate matter (PM). The effects of

inhaling particulate matter have been studied in humans and animals and include

asthma, lung cancer, cardiovascular issues, and premature death [9]. There are,

however, some additional products of the combustion process that include nitrogen

oxides and sulfur and some un-combusted hydrocarbons, depending on the operating

conditions and the fuel-air ratio.

Electric vehicles provide for less dependence on foreign oil, which for our country

Kenya and other emerging countries is cause for concern about vulnerability to oil price

volatility and supply disruption [10]. Also for many developing countries, and

particularly those in Africa, high oil prices have an adverse impact on their balance of

payments, hindering their economic growth.

An important goal for electric vehicles is overcoming the disparity between their costs

of development, production, and operation, with respect to those of equivalent internal

combustion engine vehicles. The up-front purchase price of electric cars is significantly

higher than conventional internal combustion engine cars, even after

considering government incentives for plug-in electric vehicles available in several

countries. The primary reason is the high cost of car batteries. The high purchase price

is hindering the mass transition from gasoline vehicle to electric vehicle [10].

While there is some technical superiority of electric propulsion compared with

conventional technology, one should be aware that, in many countries, the effect of

electrification of vehicles' fleet emissions will predominantly be due to regulation

rather than technology. Several governments have established policies and economic

incentives to overcome existing barriers, promote the sales of electric Vehicle, and fund

further development of electric vehicles, batteries and components. Several national

and local governments have established tax credits, subsidies, and other incentives to

reduce the net purchase price of electric cars.

1.3 ADVANTAGES OF ELECTRIC TRACTION

Electric drive motors run quieter than internal-combustion engines. The noise

emissions from electric vehicles is very low. At high speeds, the rolling noise

from the tires is the loudest sound.

Electric vehicles produce no harmful emissions of greenhouse gases while

driving. If the high-voltage battery is charged from renewable energy sources, an

electric vehicle can be run CO2-free.

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In the near future, if particularly badly congested town centers are turned into

zero-emissions zones, we will only be able to drive through them with high-

voltage vehicles.

The electric drive motor is very robust and requires little maintenance. It is only

subject to minor mechanical wear.

Electric drive motors have a high degree of efficiency of up to 96% compared

with internal-combustion engines that have an efficiency of 35–40%.

Electric drive motors have excellent torque and output characteristics. They

develop maximum torque from standstill. This allows an electric vehicle to

accelerate considerably faster than a vehicle with an internal combustion engine

producing the same output.

The drive train design is simpler because vehicle components like the

transmission, clutch, mufflers, particulate filters, fuel tank, starter, alternator and

spark plugs are not required.

When the vehicle is braked, the motor can also be used as an alternator that

produces electricity and charges the battery (regenerative braking).

The high-voltage battery can be charged at home, in a car park and by using any

accessible sockets. The blue charging connector on the vehicle and on public

charging stations has been standardized across Germany and is used by all

manufacturers.

The energy is only supplied when the user needs it. Compared with conventional

vehicles, the electric drive motor never runs when the vehicle stops at a red light.

The electric drive motor is highly efficient particularly in lines and bumper-to-

bumper traffic.

Apart from the reduction gearbox on the electric drive motor, the electric vehicle

does not require any lubricating oil.

1.4 DISADVANTAGES OF ELECTRIC VEHICLES

Electric vehicles have a limited range due to battery size and construction.

Charging a high voltage battery can take a long time, depending on the battery

charge and power source.

The network of electric charging stations is sparse.

If the destination is beyond the range of the electric vehicle, the driver will need

to plan the journey. “Where he/ she can charge the electric vehicle on the road?”

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1.5 OBJECTIVE

The Objectives of this project is to design and implement a PWM based DC motor

control for electric vehicle that has the following properties;

Operates using 12V 7ah battery.

Can be used to drive an electric vehicle while minimizing the overall cost of

production.

Reduction of circuit’s complexity by using microcontroller to PWM signal.

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2 LITERATURE REVIEW

The topic of “electro-mobility” basically refers to all vehicles that are driven by means

of electrical energy. This includes both battery-powered vehicles and hybrid vehicles

(full hybrid vehicles) or vehicles with a fuel cell.

2.1 CLASSIFICATION OF ELECTRIC VEHICLE

Electric vehicles are categorized primarily according to concept and their names

indicate how the electrical energy is supplied.

Hybrid drive

Electric drive

2.1.1 Hybrid drive

Basically, any vehicle power train is required to;

1. Develop sufficient power to meet the demands of vehicle performance.

2. Carry sufficient energy onboard to support vehicle driving in the given range.

3. Demonstrate high efficiency.

4. Emit few environmental pollutants.

Broadly, a vehicle may have more than one energy source and energy converter (power

source), such as a gasoline (or diesel) heat engine system, hydrogen–fuel cell–electric

motor system, chemical battery–electric motor system, etc. A vehicle that has two or

more energy sources and energy converters is called a hybrid vehicle [2].

Hybrids share an overlapping set of technologies to make their systems work. Their

basic goal is to maximize the use of the electric portion of the drivetrain because

electric motors are more efficient and produce no emissions. Hybrids have been called a

“bridge” toward pure electric vehicles. In other words, they are a compromise, so

another qualifier is they can be considered good, better, and best compromises.

All gas-electric hybrids utilize some size of battery pack and electric motor. Engineers

have come up with various ways to keep the battery charged short of plugging the car

in. An exception is the plug-in hybrid which can partially recharge on the road, but

needs to be plugged in because its battery is too large for the car to efficiently recharge

it on the go [11].

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The smaller batteries in regular “full” or “mild” hybrids – or even “micro hybrids” – are

replenished through a couple of ways. One is by the motor/generator which alternately

helps propel the car, or upon deceleration, generates power back to the pack. This is

what “regenerative braking” involves. The motor essentially reverses and works to

create energy when the car is slowing down. It thus converts kinetic energy and is an

elegant solution [1]. Another way is by allowing the engine to turn the motor/generator

in certain portions of the drive cycle where it can most efficiently do so. Of course this

would be impossible without fairly advanced computer controls which monitor these

and a few other tricks. Other tricks include “stop-start” technology, also known as “idle-

off,” which shuts down the engine when the car comes to a stop, and these come in a

variety of types.

Another thing enabled by hybridization is reduction of the engine displacement and

often number of cylinders. Because the electric motor shares the load, a gasoline engine

can be optimally sized for fuel efficiency and clean burning. Most full hybrids also

incorporate the Atkinson Cycle. This shortens the intake and compression stroke of a

four-cycle engine to increase efficiency at the expense of some horsepower and torque.

Again, with the addition of electric motor to fill in the gaps, the driver does not perceive

an underpowered vehicle.

Hybrids also tend to use an efficient variation of the automatic transmission called a

continuously variable transmission (CVT). This changes the drive ratios more steadily

allowing the engine to run in its most fuel-efficient rpm range. Some hybrids however

may have a regular automatic transmission.

2.1.1.1 ARCHITECTURES OF HYBRID ELECTRIC DRIVE TRAINS

The architecture of a hybrid vehicle is loosely defined as the connection between the

components that define the energy flow routes and control ports. Traditionally, HEVs

were classified into two basic types: series and parallel. It is interesting to note that, in

2000, some newly introduced HEVs could not be classified into these kinds. Therefore,

HEVs are now classified into four kinds: series hybrid, parallel hybrid, series–parallel

hybrid, and complex hybrid, which are functionally shown in below [2].

2.1.1.1.1 Series Hybrid Electric Drive Trains

A series hybrid drive train is a drive train where two power sources feed a single

power-plant (electric motor) that propels the vehicle. Only the electric motor drives the

drivetrain, and a smaller internal combustion engine works as a generator to power the

electric motor or to recharge the batteries.

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In other words, the gas engine never mechanically turns the drive wheels [2] [11]. They

also usually have a larger battery pack than parallel hybrids, making them more

expensive. Once the batteries are low, the small combustion engine can generate power

at its optimum settings at all times, making them more efficient in extensive city

driving.

2.1.1.1.2 Parallel Hybrid Electric Drive Trains

In parallel mode, both the gas engine and electric motor contribute to driving the

wheels. A parallel hybrid drive train is a drive train in which the engine supplies its

power mechanically to the wheels like in a conventional internal combustion engine-

powered vehicle. It is assisted by an electric motor that is mechanically coupled to the

transmission [2]. The internal combustion engine of many parallel hybrids can also act

as a generator for supplemental recharging. Currently, commercialized parallel hybrids

use a full size combustion engine with a single, small (<20 kW) electric motor and small

Figure 2.1 Classification of hybrid electric vehicles

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battery pack as the electric motor is designed to supplement the main engine, not to be

the sole source of motive power from launch.

2.1.1.2 TYPES BY DEGREE OF HYBRIDIZATION

Hybrids can basically be divided into three main types depending on the degree of

hybridization. These are:

Full hybrids

Mild hybrids

Plug-in hybrids.

2.1.1.2.1 Full hybrids (HEV)

Sometimes also called a strong hybrid, is a vehicle that can run on just the engine, just

the batteries, or a combination of both. Ford's hybrid system, Toyota's Hybrid Synergy

Drive and General Motors/Chrysler's Two-Mode Hybrid technologies are full hybrid,

these cars can be moved forward on battery power alone. A large, high-capacity battery

pack is needed for battery-only operation. These vehicles have a split power path

allowing greater flexibility in the drivetrain by interconverting mechanical and

electrical power, at some cost in complexity [11] [12].

2.1.1.2.2 Mild hybrids

Mild hybrid, is a vehicle that cannot be driven solely on its electric motor, because the

electric motor does not have enough power to propel the vehicle on its own. Mild

hybrids only include some of the features found in hybrid technology, and usually

achieve limited fuel consumption savings. A mild hybrid is essentially a conventional

vehicle with oversize starter motor, allowing the engine to be turned off whenever the

car is coasting, braking, or stopped, yet restart quickly and cleanly. The motor is often

mounted between the engine and transmission, taking the place of the torque

converter, and is used to supply additional propulsion energy when accelerating.

Accessories can continue to run on electrical power while the gasoline engine is off, and

as in other hybrid designs, the motor is used for regenerative braking to recapture

energy. As compared to full hybrids, mild hybrids have smaller batteries and a smaller,

weaker motor/generator, which allows manufacturers to reduce cost and weight [11]

[12].

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2.1.1.2.3 Plug-in hybrids

A plug-in hybrid electric vehicle (PHEV), also known as a plug-in hybrid, is a hybrid

electric vehicle with rechargeable batteries that can be restored to full charge by

connecting a plug to an external electric power source. A PHEV shares the

characteristics of both a conventional hybrid electric vehicle, having an electric motor

and an internal combustion engine; and of an all-electric vehicle, also having a plug to

connect to the electrical grid. PHEVs have a much larger all-electric range as compared

to conventional gasoline-electric hybrids, and also eliminate the "range anxiety"

associated with all-electric vehicles, because the combustion engine works as a backup

when the batteries are depleted [12] [11].

Since it is both an electric vehicle (EV) for short distance travel and a conventional

hybrid vehicle (HV) for longer distances, the plug-in hybrid vehicle (PHV) integrates the

merits of both an electric and a hybrid vehicle.

2.1.2 ELECTRIC DRIVE (EV)

Previously, the EV was mainly converted from the existing internal combustion engine

vehicle by replacing the internal combustion engine and fuel tank with an electric

motor drive and battery pack while retaining all the other components, as shown in

Figure 2.2 below.

Figure 2.2 Primary electric vehicle power train

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Drawbacks such as its heavy weight, lower flexibility, and performance degradation

have caused the use of this type of EV to fade out. In its place, the modern EV is built

based on original body and frame designs. This satisfies the structure requirements

unique to EVs and makes use of the greater flexibility of electric propulsion. A modern

electric drive train is conceptually illustrated in Figure 2.3. The drive train consists of

three major subsystems: electric motor propulsion, energy source, and auxiliary. The

electric propulsion subsystem is comprised of a vehicle controller, power electronic

converter, electric motor, mechanical transmission, and driving wheels. The energy

source subsystem involves the energy source, the energy management unit, and the

energy refueling unit.

The auxiliary subsystem consists of the power steering unit, the hotel climate control

unit, and the auxiliary supply unit. Based on the control inputs from the accelerator and

brake pedals, the vehicle controller provides proper control signals to the electronic

power converter, which functions to regulate the power flow between the electric

motor and energy source. The backward power flow is due to the regenerative braking

of the EV and this regenerated energy can be restored to the energy source, provided

the energy source is receptive. Most EV batteries as well as ultra-capacitors and

Figure 2.3 Conceptual illustration of general EV configuration

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flywheels readily possess the ability to accept regenerated energy. The energy

management unit cooperates with the vehicle controller to control the regenerative

braking and its energy recovery. It also works with the energy refueling unit to control

the refueling unit, and to monitor the usability of the energy source. The auxiliary

power supply provides the necessary power at different voltage levels for all the EV

auxiliaries, especially the hotel climate control and power steering units.

There are a variety of possible EV configurations due to the variations in electric

propulsion characteristics and energy sources, as shown in Figure 2.4.

a. Figure 2.4(a) shows the configuration of the first alternative, in which an electric

propulsion replaces the IC engine of a conventional vehicle drive train. It consists

of an electric motor, a clutch, a gearbox, and a differential. The clutch and

gearbox may be replaced by automatic transmission. The clutch is used to

connect or disconnect the power of the electric motor from the driven wheels.

The gearbox provides a set of gear ratios to modify the speed-power (torque)

profile to match the load requirement. The differential is a mechanical device

(usually a set of planetary gears), which enables the wheels of both sides to be

driven at different speeds when the vehicle runs along a curved path.

b. With an electric motor that has constant power in a long speed range, a fixed

gearing can replace the multispeed gearbox and reduce the need for a clutch. This

configuration not only reduces the size and weight of the mechanical

transmission, but also simplifies the drive train control because gear shifting is

not needed.

c. Similar to the drive train in (b), the electric motor, the fixed gearing, and the

differential can be further integrated into a single assembly while both axles

point at both driving wheels. The whole drive train is further simplified and

compacted.

d. In Figure 2.4(d), the mechanical differential is replaced by using two traction

motors. Each of them drives one side wheel and operates at a different speed

when the vehicle is running along a curved path.

e. In order to further simplify the drive train, the traction motor can be placed

inside a wheel. This arrangement is the so-called in-wheel drive. A thin planetary

gear set may be used to reduce the motor speed and enhance the motor torque.

The thin planetary gear set offers the advantage of a high-speed reduction ratio

as well as an inline arrangement of the input and output shaft.

f. By fully abandoning any mechanical gearing between the electric motor and the

driving wheel, the out-rotor of a low-speed electric motor in the in-wheel drive

can be directly connected to the driving wheel. The speed control of the electric

15

motor is equivalent to the control of the wheel speed and hence the vehicle

speed. However, this arrangement requires the electric motor to have a higher

torque to start and accelerate the vehicle.

2.2 DIRECT CURRENT MOTOR

Direct-current machines were the first electrical machines invented, a simple DC motor

drove an electric locomotive in Edinburgh in 1839, and although it took another 40

years before the DC motor became widespread. The ability to control the speed with

great accuracy is an attractive feature of the DC motor.

A DC motor relies on the fact that like magnet poles repel and unlike magnetic poles

attract each other. A coil of wire with a current running through it generates an

electromagnetic field aligned with the center of the coil. By switching the current on or

off in a coil its magnetic field can be switched on or off or by switching the direction of

the current in the coil the direction of the generated magnetic field can be switched

180°. A simple DC motor typically has a stationary set of magnets in the stator and an

Figure 2.4 Possible EV configurations

16

armature with a series of two or more windings of wire wrapped in insulated stack

slots around iron pole pieces (called stack teeth) with the ends of the wires terminating

on a commutator. The armature includes the mounting bearings that keep it in the

center of the motor and the power shaft of the motor and the commutator connections.

The winding in the armature continues to loop all the way around the armature and

uses either single or parallel conductors (wires), and can circle several times around

the stack teeth. The total amount of current sent to the coil, the coil's size and what it's

wrapped around dictate the strength of the electromagnetic field created. The sequence

of turning a particular coil on or off dictates what direction the effective

electromagnetic fields are pointed. By turning on and off coils in sequence a rotating

magnetic field can be created. These rotating magnetic fields interact with the magnetic

fields of the magnets (permanent or electromagnets) in the stationary part of the motor

(stator) to create a force on the armature which causes it to rotate. In some DC motor

designs the stator fields use electromagnets to create their magnetic fields which allow

greater control over the motor. At high power levels, DC motors are almost always

cooled using forced air [1].

2.2.1 CLASSIFICATION OF A DC MOTORS

DC motors can be divided into two general categories;

2.2.1.1 Brush-type DC Motors:

They have a mechanical brush pair on the motor frame and makes contact with a commutator ring assembly on the rotor in order to communicate current, i.e. to switch current from one winding to another, as a function of rotor position so that the magnetic fields of the rotor & stator are always at a 90 degrees angle relative to each other.

2.2.1.2 Brushless DC Motors:

They are an inside-out version of the brush-type DC motors, i.e. the rotor has the permanent magnets and the stator has the winding. Hence, magnetic fields of the rotor & stator must be perpendicular to each other at all rotor positions. Communication is done by solid-state power transistors based on a rotor position sensor, hence it is considered a servo motor.

2.2.2 CLASSIFICATION ON BASIS OF EXCITATION WINDING

Further classification of dc motors is on the basis of their excitation winding. Field winding may be connected to armature winding (in series or parallel) or it may be separately excited [13]. Figure 2.5 below shows the various types available;

17

2.2.2.1 Separately Excited DC Motor

As the name suggests, in case of a separately excited DC motor the supply is given

separately to the field and armature windings. The main distinguishing fact in these

types of dc motor is that, the armature current does not flow through the field windings,

as the field winding is energized from a separate external source of dc current as shown

in the figure beside. From the torque equation of dc motor we know Tg = Ka φ Ia So the

torque in this case can be varied by varying field flux φ, independent of the armature

current Ia.

2.2.2.2 Permanent Magnet DC Motor

The permanent magnet DC motor consists of an armature winding as in case of a usual

motor, but does not necessarily contain the field windings. The construction of these

types of DC motor are such that, radially magnetized permanent magnets are mounted

on the inner periphery of the stator core to produce the field flux. The rotor on the

Figure 2.5 types of Dc motors

18

other hand has a conventional dc armature with commutator segments and brushes.

The diagrammatic representation of a permanent magnet dc motor is given below.

The torque equation of dc motor suggests Tg = Ka φ Ia. Here φ is always constant, as

permanent magnets of required flux density are chosen at the time of construction and

can’t be changed thereafter.

For a permanent magnet dc motor Tg = Ka1Ia

Where Ka1 = Ka.φ which is another constant. In this case the torque of DC Motor can

only be changed by controlling armature supply.

2.2.2.3 Self-Excited DC Motor

In case of self-excited dc motor, the field winding is connected either in series or in

parallel or partly in series, partly in parallel to the armature winding, and on this basis

its further classified as:-

1. Shunt wound DC motor.

2. Series wound DC motor.

3. Compound wound DC motor

2.2.2.3.1 Parallel (Shunt) Wound DC Motors

A shunt wound DC motor has the armature and field windings connected in parallel.

Figure 2.7 shows a shunt wound DC motor, with an associated speed/torque curve.

Figure 2.6 permanent magnet DC motor and Curves

19

This type of DC motor is probably the most widely used motor in industrial

applications. As indicated in the figure, this type of motor requires two power supplies-

one for the armature and one for the field winding. To understand the characteristic of

these types of DC motor, let's consider the basic voltage equation given by,

[Where E, Eb, Ia, Ra are the supply voltage, back emf, armature current and armature

resistance respectively]

[Since back emf increases with flux φ and angular speed ω]

Now substituting Eb from equation (2) to equation (1) we get,

The torque equation of a dc motor resembles,

This is similar to the equation of a straight line, and we can graphically representing the

torque speed characteristic of a shunt wound self-excited dc motor as

The shunt wound dc motor is a constant speed motor, as the speed does not vary here

with the variation of mechanical load on the output.

Figure 2.7 shunt wound DC motor and curve

20

With constant armature voltage and field winding excitation, this type of motor offers

relatively flat speed/torque characteristics. The starting torque developed can be 250-

300% of the full load torque rating for a short period of time. Speed regulation (speed

fluctuation due to load) is acceptable in many cases between 5-10% of maximum speed,

when operated from a DC drive. Regulation of this amount would be typical when

operated from a drive controller, open loop (no electronic feedback device connected to

the motor shaft).

Because of the need for two power sources, the shunt wound DC motor offers the use of

simplified control for reversing requirements. Direction of any shunt wound motor can

be changed by simply reversing the direction of current flow, in either the armature or

shunt field winding. The capability of armature or field reversal is standard on many DC

drive modules. (In many cases, the reversing of flux and direction is accomplished in the

field winding control. The field winding consumes less than one tenth of the current

compared with the armature circuit. Smaller components and less stress on circuitry is

the result when "field reversal" is used for DC motor control.)

2.2.2.3.2 Series Wound DC Motors

A series wound DC motor has the armature and field windings connected in a series

circuit. Figure below shows a series wound DC motor, with an associated speed/torque

curve.

Now to determine the torque speed characteristic of these types of DC motor, let's get

to the torque speed equation.

From the circuit diagram we can see that the voltage equation gets modified to

Whereas back emf remains Eb = kaφω

Neglecting saturation we get,

[Since field current = armature current]

From equation (5) & (6)

21

From this equation we obtain the torque speed characteristic as shown in Figure 2.8. In

a series wound dc motor, the speed varies with load. And operation wise this is its main

difference from a shunt wound dc motor. The starting torque developed can be as high

as 500% of the full load rating. The high starting torque is a result of the fact that the

field winding is operated below the saturation point. An increase in load will cause a

corresponding increase in both the armature and field winding current, which means

that both armature and field winding flux increase together. As you recall, the torque

developed in a DC motor is the result of the interaction of armature and field winding

fluxes. Torque in a DC motor increases as the square of the current value.

A series wound DC motor will generate a larger torque increase compared with a shunt

wound DC motor for given increase in current. Conversely, the speed regulation of a

series wound DC motor is poorer than that of a shunt wound motor. As stated above,

when the load increases, so does the armature and field winding current. When the load

is reduced, so is the current, which causes a corresponding decrease in flux density. As a

reminder of DC motor basics, when the field flux is reduced once the motor is running, a

decrease in "hold-back" electromotive force (EMF) occurs. Therefore, when the load is

reduced, speed increases. If the load were completely removed, the speed of the motor

would increase to infinity-basically until the motor destroys itself. As a safety

precaution, series wound DC motors should always be connected to a load.

2.2.2.3.3 Compound Wound DC Motors

A compound wound DC motor is basically a combination of shunt wound and series

wound configurations. This type of motor offers the high starting torque of a series

wound motor. In addition, it offers constant speed regulation (speed stability) under a

given load. This type of motor is used whenever speed regulation cannot be obtained

Figure 2.8 series DC motor

22

from either a series or shunt wound motor. The torque and speed characteristics are

the result of placing a portion of the field winding circuit in series with the armature

circuit. This additional armature winding circuit is not to be confused with the

commutating winding or inter-poles. The commutation windings also have a few turns,

but have the duty of neutralizing armature reaction.

When a load is applied, there is a corresponding increase in current through the series

winding, which also increases the field flux. This in turn increases the torque output of

the motor. The excitation of compound wound dc motor can be of two types depending

on the nature of compounding.

2.2.2.3.3.1 Cumulative Compound DC Motor

When the shunt field flux assists the main field flux, produced by the main field

connected in series to the armature winding then it’s called cumulative compound dc

motor.

2.2.2.3.3.2 Differential Compound DC Motor

In case of a differentially compounded self-excited dc motor i.e. differential compound

dc motor, the arrangement of shunt and series winding is such that the field flux

produced by the shunt field winding diminishes the effect of flux by the main series

field winding.

The net flux produced in this case is lesser than the original flux and hence does not find

much of a practical application. Both the cumulative compound and differential

compound dc motor can either be of short shunt or long shunt type depending on the

nature of arrangement.

2.2.2.3.3.3 Short Shunt DC Motor

If the shunt field winding is only parallel to the armature winding and not the series

field winding then it’s known as short shunt dc motor or more specifically short shunt

type compound wound dc motor.

23

2.2.2.3.3.4 Long Shunt DC Motor

If the shunt field winding is parallel to both the armature winding and the series field

winding then it’s known as long shunt type compounded wound dc motor or simply

long shunt dc motor.

24

3 DESIGN

In this paper we are concern majorly on controlling DC Motors for electric Vehicle. DC

motor is an electric motor that runs on direct current (DC) electricity. The DC motors

will be used to providing the motive power for the electric vehicles and operate directly

from rechargeable battery of 12V 7AH battery hence allow regenerative braking to be

implemented.

While designing a DC motor control for electric vehicle can be complex, it does become

easier when broken down into its component steps. The following sections detail each

component within the project, as well as how each section is constructed and interacts

with other blocks.

The two stages of this work are the hardware development and software development.

The first stage i.e. the hardware development, has the following sections;

1. H-bridge 2. Display Unit (LCD) 3. Input Unit 4. Motor controller circuit, this includes the circuit for the PIC16F877A

microcontroller and the H-bridge. 5. DC-motor and Mechanical Vehicle Parts (Wheels and Gears) 6. Dc Power Supply and charging unit

The second stage i.e. the software development, has two parts which are;

1) To develop embedded system software using the MikroC PRO for PIC16F877A

microcontroller.

2) Simulating the control system using Proteus software.

3.1 HARDWARE DEVELOPMENT

The block diagram of the system is shown in Figure 3.1

25

3.1.1 H-BRIDGE

An H-Bridge or full bridge converter is a switching configuration composed of four

switches in this case MOSFETs in an arrangement that resembles an H and enables a

voltage to be applied across a load in either direction [14]. These circuits are often used

in robotics and other applications to allow DC motors to run forwards and backwards.

Figure 3.2 h-bridge

Figure 3.1 block diagram

26

By controlling which switches are closed at any given moment, the voltage across the

motor can be either positive, negative, or zero. As shown in Figure 3.2 . A solid state H-

bridge is built using four switches. When switch Q1 and Q4 are closed and switches Q2

and Q3 are open (according to Figure 3.3 a) a positive voltage will be applied across the

motor. During forward free driving Q4 is kept on so when the PWM signal is off,

current can continue to flow around the bottom loop through Q3's intrinsic diode as

shown in Figure 3.3Figure 3.3b.By closing Q2 and Q3 switches and opening Q1 and Q4

switches (according to Figure 3.3c) a reverse voltage will be applied to the load allowing

reverse operation of the motor. Also during reverse free driving Q3 is kept on so when

the PWM signal is off, current can continue to flow around the bottom loop through

Q4's intrinsic diode as shown in Figure 3.3d. Using nomenclature above switches Q1

and Q2 should never be closed at the same time as this will cause a shot circuit on

between the power supply and ground, potentially damaging the devices or draining

the power supply. The same applies to switches Q3 and Q4. This condition is known as

shoot-through.

Figure 3.3 h-bridge switch configuration

For regeneration, when the motor is going backwards for example, the motor (which

is now acting as a generator) is forcing current right through its armature, through

27

Q2's diode, through the battery (thereby charging it up) and back through Q3's

diode. Regenerative braking is shown in Figure 3.4 below.

Figure 3.4 regenerative braking

TABLE 1 below outlines the positions. Note that shoot-through switch positions are

omitted. The switches used to implement an H-Bridge can be mechanical built from

solid state transistors. Selection of the proper switches varies greatly.

TABLE 1 H-BRIDGE SWITCHES CONFIGURATION

S1 S2 S3 S4 OPERATION PERFORMED

1 0 0 1 Forward Drive

0 1 1 0 Reverse Drive

0 0 0 0 Free Running

1 0 1 0 Brakes

0 1 0 1 Brakes

28

3.1.1.1 CHOICE OF SWITCHING TRANSISTOR

While designing this circuit, a choice had to be made between the two main types of

switches used in power electronics. One is the power MOSFET which is much like a

standard MOSFET but designed to handle relatively large voltages and currents. The

other is the insulated gate bipolar transistor (IGBT) [15]. Each has its advantages, and

there is a high degree of overlap in the specifications of the two. IGBTs tend to be used

in very high voltage applications, nearly always above 200V, and generally above 600W.

They do not have the high frequency switching capability of MOSFETs, and tend to be

used at frequencies lower than 29 kHz. They can handle high currents, are able to

output greater than 5kW, and have very good thermal operating ability, being able to

operate properly above 100 Celsius. One of the major disadvantages of IGBTs is their

unavoidable current tail when they turn off. Essentially, when the IGBT turns off, the

current of the gate transistor cannot dissipate immediately, which causes a loss of

power each time this occurs. This tail is due to the very design of the IGBT and cannot

be remedied. IGBTs also have no body diode, which can be good or bad depending on

the application.

Power MOSFETS have a much higher switching frequency capability than do IGBTs, and

can be switched at frequencies higher than 200 kHz. They do not have as much

capability for high voltage and high current applications, and tend to be used at voltages

lower than 250V and less than 500W [1]. MOSFETs do not have current tail power

losses, which makes them more efficient than IGBTs. Both MOSFETs and IGBTs have

power losses due to the ramp up and ramp down of the voltage when turning on and off

(dV/dt losses). Unlike IGBTs, MOSFETs have body diode. Generally, IGBTs are the sure

bet for high voltage, low frequency (>1000V, <20 kHz) uses and MOSFETs are ideal for

low voltage, high frequency applications (<250V, >200 kHz). In between these two

extremes is a large grey area. In this area, other considerations such as power, percent

duty cycle, availability and cost tend to be the deciding factors. Since this project is

about design of a 12V, DC motor control to be used in electric vehicle MOSFET is the

ideal choice. Also MOSFET being a voltage controlled device, it can be driven directly

from CMOS or TTL logic and the same gate signal can be applied to diagonally opposite

switches since the gate drive current required is very low.

3.1.1.2 ENHANCED N-CHANNEL VS ENHANCED P-CHANNEL MOSFETS

The use of P-Channel MOSFETs on the high side and N-Channel MOSFETs on the low

side is easier, but using all N-Channel MOSFETs and a FET driver, lower “on” resistance

can be obtained resulting in reduced power loss. This requires a more complex circuit

29

since the gate of the high side Mosfet must be driven positive with respect to Vs bus

voltage to turn on Mosfet [15].

3.1.1.3 MOSFETs CHARACTERISTIC

In this project enhanced n-channel Mosfet was chosen for both high side and low side

switches of the H-bridge. For the Mosfet to carry drain current Id (on state) a channel

between the drain and source must be created [1]. This occurs when drain to source

Vgs voltage exceeds the device threshold (Vgs>Vth). Once the channel is induced the

Mosfet can operate in either triode region (drain current proportional to channel

resistance) or the saturation region (constant drain current). The gate to drain voltage

Vgs determines whether the induced channel enters pitch-off or remains in triode

region. When used as a switching device only triode and cut-off region are utilized. The

device will operate at cut-off (off state) when gate to source voltage Vgs is less than

threshold voltage Vth (Vgs<Vth) [1].

a. Triode region; Vds<Vgs-Vth b. Saturation region; Vds>Vgs-Vth c. Cut-off region; Vgs<Vth

3.1.1.4 MOSFET DRIVER

As stated in the previous section, it is beneficial to use N-channel MOSFETs as the high

side switches as well as the low side switches because they have a lower ‘ON’ resistance

and therefore less power loss. However, to do so, the drain of the high side device is

connected to 12V DC power. This is a problem because the 12V is the highest voltage in

the system and in order for the switch to be turned on the voltage at the gate terminal

must be 10V higher than the drain terminal voltage [15]. Therefore, to drive MOSFETs

in the H-Bridge MOSFET driver IC is used with a bootstrap capacitor specifically

designed for driving a half-bridge. After considering various IC options, the ideal choice

was the IR2110, which is rated at 600V, with a gate driving current of 2A and a gate

driving voltage of 10-20V. The turn on and turn off times are 120ns and 94ns

respectively [16].

The MOSFET driver operates from a signal input given from the microcontroller and

takes its power from the battery voltage supply that the system uses. The driver is

capable of operating both the high side and low side devices, but in order to get the

extra 10V for the high side device, an external bootstrap capacitor is charged through a

diode from the 12V power supply when the device is off. Because the power for the

30

driver is supplied from the low voltage source, the power consumed to drive the gate is

small. When the driver is given the signal to turn on the high side device, the gate of the

MOSFET has an extra boost in charge from the bootstrap capacitor, surpassing the

needed 10V to activate the device and turning the switch on [17].

FIGURE 3.5 IR2110 CONNECTION

3.1.1.4.1 BOOTSTRAP CAPACITOR

As shown in FIGURE 3.5, the bootstrap diode and capacitor are the only external

components strictly required for operation in a standard PWM application. Local

decoupling capacitors on the VCC (and digital) supply are useful in practice to

compensate for the inductance of the supply lines. The voltage seen by the bootstrap

capacitor is the VCC supply only. Its capacitance is determined by the following

constraints:

(i) Gate voltage required to enhance MGT

(ii) IQBS - quiescent current for the high-side driver circuitry

(iii) Currents within the level shifter of the control IC

(iv) MGT gate-source forward leakage current

(v) Bootstrap capacitor leakage current

Factor 5 is only relevant if the bootstrap capacitor is an electrolytic capacitor, and can

be ignored if other types of capacitor are used. Therefore it was ignored since only

31

nonelectrolyte capacitors were used. The minimum bootstrap capacitor value was

calculated from the following equation [17]:

𝐶 ≥ 2[2𝑄𝑔+

𝐼𝑞𝑏𝑠

𝑓+𝑄𝑙𝑠+

𝐼𝑐𝑏𝑠(𝑙𝑒𝑎𝑘)

𝑓]

𝑉𝑐𝑐−𝑉𝑓−𝑉𝑙𝑠−𝑉𝑚𝑖𝑛

Where:

Qg = Gate charge of high-side FET=16nC f= frequency of operation=5000Hz ICbs (leak) = bootstrap capacitor leakage current=0A Iqbs (max) = Maximum VBS quiescent current=230µA VCC = Logic section voltage source=12V Vf = Forward voltage drop across the bootstrap diode=1.4V VLS = Voltage drop across the low-side FET or load=1.8V VMin = Minimum voltage between VB and VS=0V Qls = level shift charge required per cycle (typically 5nC for 500 V/600 V MGDs and 20nC for 1200 V MGDs)

The values substituted into this equation were found either in driver datasheet for

IR2110 IC or IRF540 MOSFET datasheet. Using these numbers minimum bootstrap

capacitance value was calculated in the equation below:

𝑐 ≥2[(2∗16∗10−9)+

230∗10−6

5000+(5∗10−9)]

12−1.4−1.8

𝑐 ≥ 18𝑛𝐹

The capacitor value obtained from the above equation is the absolute minimum

required, however due to nature the bootstrap circuit operation, a low value of

capacitor can lead to overcharging which could in turn damage the IC. Therefore to

minimize the risk of overcharging and further reduce ripple on the Vds voltage the

capacitor value obtained is multiplied by a factor of 5 to get a capacitor value of 90nF

where by 100nF is selected.

3.1.1.4.2 BOOTSTRAP DIODE

The bootstrap diode must be able to block the full voltage seen in the specific circuit

and is about equal to the voltage across the power rail. The current rating of the diode is

the product of gate charge times switching frequency. The high temperature reverse

leakage characteristic of this diode can be an important parameter in those applications

where the capacitor has to hold the charge for a prolonged period of time. For the same

reason it is important that this diode have an ultra-fast recovery to reduce the amount

of charge that is fed back from the bootstrap capacitor into the supply [17]. In order to

32

improve decoupling a decoupling capacitors has to be connected directly across the VCC

and COM pins as shown in FIGURE 3.5.

3.1.1.4.3 GATE RESISTOR

Driving MOS-gated power transistors directly from the driver can result in

unnecessarily high switching speeds. Increasing the value of the series gate resistor,

results in a rapid decrease of the amplitude of the negative spike, while the turn-off

time is a linear function of the series gate resistance. Selecting a resistor value just right

from the “knee” in Figure 3.6 provides a good trade-off between the spike amplitude

and the turn-off speed the di/dt losses may have to be reduced by reducing the

switching speed by means of the gate resistor [17]. A graph of the negative spike and

the turn-off time versus series gate resistance is shown in Figure 3.6. The layout should

also minimize the stray inductance in the charge/discharge loops of the gate drive to

reduce oscillations and to improve switching speed and noise immunity, particularly

the “dV/dt induced turn-on”. For this design resistor values of 20 ohms was chosen.

Figure 3.6 series gate resistance vs. Amplitude of negative voltage spike and turn-off time

3.1.2 CONTROL SYSTEM

Control theory is an interdisciplinary branch of engineering and mathematics that deals

with the behavior of dynamical systems .The desired output of a system is called the

reference. When one or more output variables of a system need to follow a certain

33

reference over time, a controller manipulates the inputs to a system to obtain the

desired effect on the output of the system [18].

If we consider an automobile cruise control, it is design to maintain the speed of the

vehicle at a constant speed set by the driver. In this case the system is the vehicle. The

vehicle speed is the output and the control is the vehicle throttle which influences the

engine torque output. One way to implement cruise control is by locking the throttle at

the desired speed but when encounter a hill the vehicle will slow down going up and

accelerate going down. In fact, any parameter different than what was assumed at

design time will translate into a proportional error in the output velocity, including

exact mass of the vehicle, wind resistance, and tire pressure [18] .This type of controller

is called an open-loop controller because there is no direct connection between the

output of the system (the engine torque) and the actual conditions encountered mean

the system does not and cannot compensate for unexpected forces. For the purpose of

keeping the cost of the project at minimum this is the type which is going to be

implemented in this design. Although, there is another type known as closed loop

control system.

For a closed-loop control system, a sensor will monitor the vehicle speed and feedback

the data to its computer and continuously adjusting its control input or the throttle as

desired to ensure the control error to a minimum therefore maintaining the desired

speed of the vehicle [18]. Feedback on how the system is actually performing allows the

controller (vehicle's on board computer) to dynamically compensate for disturbances

to the system, such as changes in slope of the ground or wind speed. An ideal feedback

control system cancels out all errors, effectively mitigating the effects of any forces that

may or may not arise during operation and producing a response in the system that

perfectly matches the user's wishes.

3.1.2.1 PULSE WIDTH MODULATION (PWM)

From research, I have found several ways to control the motor speed using electronic

devices. There is voltage speed control, field speed control (I field), resistance speed

control and PWM technique. These control method have their benefit and

disadvantages respectively which is more focus to efficiency element. In this project

only PWM technique will be consider and be implemented.

Pulse Width Modulation (PWM) uses digital signals to control power applications, as

well as being fairly easy to convert back to analog with a minimum of hardware. Analog

systems, such as linear power supplies, tend to generate a lot of heat since they are

34

basically variable resistors carrying a lot of current. Digital systems don't generally

generate as much heat. Almost all the heat generated by a switching device is during the

transition (which is done quickly), while the device is neither on nor off, but in between.

This is because power follows the following formula:

P = E I, or Watts = Voltage X Current

If either voltage or current is near zero then power will be near zero. PWM takes full

advantage of this fact. Pulse-width modulation uses a square wave whose pulse width is

modulated resulting in the variation of the average value of the waveform [19]. An

example of pwm signal is shown in Figure 3.7.

The average of voltage that supply to DC motor is given by,

𝑉𝑎𝑣𝑒 =𝑡𝑜𝑛

𝑇∗ 𝑉𝑖𝑛

Where Vave = average voltage supply to DC motor

ton = time ON of switches

T = period of PWM

ton /T = DC, duty cycle

One of the parameters of any square wave is duty cycle. The ratio of on to off time is

called as duty cycle. Most square waves are 50%, this is the norm when discussing

them, but they don't have to be symmetrical. The ON time can be varied completely

between signal being off to being fully on, 0% to 100%, and all ranges between.

Examples of a 10%, 50%, and 90% duty cycle are shown in Figure 3.8.

PWM is an effective method for adjusting the amount of power delivered to the load.

PWM technique allows smooth speed variation without reducing the starting torque

and eliminates harmonics. In PWM method, operating power to the motors is turned on

and off to modulate the current to the motor. The duty cycle determines the speed of

Figure 3.7 PWM signal

35

the motor. The desired speed can be obtained by changing the duty cycle. The Pulse-

Width Modulation (PWM) in microcontroller is used to control duty cycle of DC motor

drive. Since the frequency is held constant while the on-off time is varied, the duty cycle

of PWM is determined by the pulse width. Thus the power increases with increase of

duty cycle in PWM.

3.1.3 MICROCONTROLLER

A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a

single integrated circuit containing a processor core, memory, and programmable

input/output peripherals. Program memory in the form of NOR flash or OTP ROM is

also often included on chip, as well as a typically small amount of RAM. Microcontrollers

are designed for embedded applications. Microcontrollers are used in automatically

controlled products and devices, such as automobile engine control systems,

implantable medical devices, remote controls, office machines, appliances, power

tools, and other systems. The Microcontroller used in this design is PIC16F877A.

3.1.3.1 REASONS FOR CHOOSING PIC MICROCONTROLLER (PIC16F877A)

3.1.3.1.1 INTERNAL ARCHITECTURE

PIC16F877a has Harvard architecture. Harvard architecture is a newer concept than

von Neumann [20]. It rose out of the need to speed up the work of a microcontroller. In

Harvard architecture data bus and address bus are separate. Thus a greater flow of data

is possible through the central processing unit and of course a greater speed of work.

Separating a program from data memory makes it further possible for instructions not

to have to be 8-bits instructions which allows for all instructions to be one word

instructions.

Figure 3.8 examples of PWM signal

36

3.1.3.1.2 INSTRUCTION SET

It is also typical for Harvard architecture to have fewer instructions than von-

Neumann's, and to have instructions usually executed in one cycle. Microcontrollers

with Harvard architecture are also called "RISC microcontrollers" [21]. Stands for

Reduced Instruction Set Computer. Microcontrollers with von-Neumann's architecture

are called 'CISC microcontrollers', which stands for Complex Instruction Set Computer.

PIC16F877A is a RISC microcontroller that means it has a reduced set of instructions;

more precisely 35 instructions. Advantages of RISC is that the microcontroller is fast

and it’s easy to learn programming language needed to program it and the user only

sees the final results [22].

3.1.3.1.3 COST

PIC16F877A is an 8 bit microcontroller classified under medium range

microcontrollers which makes it very cost competitive with other similar products in

the market and hence its pocket friendly. Due to its low cost the overall cost of the

inverter ends up being low and market competitive given that the microcontroller is the

most expensive chip in the design.

3.1.3.1.4 AVAILABILITY IN THE MARKET

Since in our country we don’t have a plant to fabricate microchips it is very important

to choose a chip which readily available in the local market to avoid incurring extra cost

of shipping. PIC16F877A was available in the local stores hence the reason to using it.

PIC16F877a perfectly fits many uses, from automotive industries and controlling home

appliances to industrial instruments, remote sensors, electrical door locks and safety

devices. It is also ideal for smart cards as well as for battery-supplied devices because of

its low power consumption [22].

3.1.4 LCD DISPLAY UNIT

A suitable display unit is required to display the gear engaged which selects the mode of

operation of the driving motor and also show the speed at which the vehicle is moving.

A 16x2 Liquid Crystal Display is a low power, low cost, basic electronic display. A 16x2

LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely,

Command and Data. The command register stores the command instructions given to

the LCD. A command is an instruction given to LCD to do a predefined task like

initializing it, clearing its screen, setting the cursor position, controlling display etc. The

data register stores the data to be displayed on the LCD. The data is the ASCII value of

37

the character (measured distance) to be displayed on the LCD [23]. The Figure 3.9

below shows LCD screen chosen for this project.

Figure 3.9 16X2 LCD display

3.1.5 INPUT UNIT

In order to be able to select different types of operation a suitable input was to be

selected capable of communicating with the microcontroller and relaying the command

from operator efficiently and fast. Several factors were considered such as the size,

weight and mode of interconnection either wireless or wired. An ideal and user friendly

would have been the wireless mode of connection but given the complicity of the circuit

needed and the cost of implementation 4 way DIP switch was selected instead. 2

switches was programmed to emulate function of gears in a vehicle while the third

switch be the brake paddle and the fourth accelerating paddle.

3.1.6 DC MOTOR

There are several types of DC motors that are available their advantages, disadvantages,

and other basic information are listed below in Table 2 [1]. In this design DC geared

motor operating at rated voltage 12V and no load speed of 200rpm was selected to be

used due to its low cost and small size and also availability in the market.

38

Table 2 Advantages and disadvantages of various types of DC motor

TYPE ADVANTAGES DISADVANTAGES

DC Geared Motor Very precise speed and position control. High Torque at low speed.

Low speed. Mechanical wear and require regular servicing

DC Motor w/field coil Wide range of speeds and torques. More powerful than permanent magnet motors

Require more current than permanent magnet motors, since field coil must be energized. Generally heavier than permanent magnet motors. More difficult to obtain.

DC permanent magnet motor

Small, compact, and easy to find. Very inexpensive

Generally small. Cannot vary magnetic field strength.

Gasoline (small two stroke) Very high power/weight ratio. Provide Extremely high torque. No batteries required.

Expensive, loud, difficult to mount, very high vibration.

3.1.7 POWER SUPPLY

Signal generation begins with the power supply for the microcontroller. As a battery’s

stored energy depletes, its voltage is reduced. Several of the amplifiers in the control

signal generation circuits rely on the rail voltages to charge and discharge capacitors

which cause a controlled oscillation Generally speaking, the correct voltage supply is of

utmost importance for the proper functioning of the microcontroller system.

For a proper function of this circuit design, it is necessary to provide 2 stable power

rails source of supply. One to power low voltage components of 5V and another 12V to

drive high voltage electronics such as IR2112 Mosfet driver and the DC motor.

According to technical specifications by the manufacturer of PIC microcontroller,

supply voltage should move between 2.0V to 5.0V in all versions [21]. The solution

comes in the form of a linear voltage regulator. There are other types of voltage

regulation, mainly switching regulators, but their benefits are of little use in powering

39

chips. Switching regulators are more efficient than linear regulators and they have the

ability to boost voltages, but the supply voltage is well-defined and the op-amps require

very little power relative to what a lead acid battery can provide. Thus, the simplest

solution to the source of supply is using the voltage stabilizer LM7805 which gives

stable +5V on its output [24]. Its connection as per datasheet is shown in Figure 3.10

below.

Figure 3.10 Voltage regulator circuit

3.1.8 CIRCUIT PROTECTION

MOSFETs turn OFF more slowly than they turn ON. If you attempt to turn on a high side

MOSFET at the same time you're turning OFF a low-side MOSFET (or vice versa), you

will wind up having both of them turned on at the same time, causing the dreaded

"shoot-through" condition, which will lead to damage of the components [17]. For this

reason one of the major factor in inverter device is its ability to protect itself from

surges that could damage the circuitry. The IR2110 used in this design does not have

built-in optoisolators hence it does not provide for "dead time" which is much needed

in order to avoid short circuiting of the rail voltage. Another protection of the circuit

needed is MOSFET gate protection, which employed a resistor between “gate” and

“source”. It prevents accidental turn on of the MOSFET by external noise usually at

startup when the gate is floating. The MOSFET may sometimes turn on with a floating

gate because of the internal drain to gate "Miller" capacitance. A gate to source resistor

acts as a pull-down to ensure a low level for the MOSFET.

The principle of operation is that when the parasitic capacitance of the circuit comes

into play. The resistor creates an RC circuit complete with its time constant. And this RC

40

delays the time the circuit switches ON just enough to allow the complementary part of

the bridge circuit to switch OFF. Typical values of this resistor a 1 kΩ, 10 kΩ, or 100 kΩ

depending on the rail voltage of the h bridge. Some of the factors which need to be

considered when selecting the value of resistor are;

1. The resistance needs to be low enough so that the gate is discharged in time, and

can be held in the low state despite capacitive coupling from startup transients.

The gate of a FET has very high resistance and mostly looks capacitive. Even a

large resistor can eventually discharge the gate capacitance. The limiting factor

there is how fast the device might be turned off and then back on again. Usually

this isn't the issue though. Keeping the gate low despite startup transients is

much harder to judge since it's almost impossible to know where these

transients may be coming from and how strongly they will couple onto the gate

node.

2. On the other end, pull-down resistor should not draw significant current that

would otherwise go to driving the gate high quickly or at all.

3.2 SOFTWARE DESIGN

The program design for this project was done in C language using MikroC compiler. It is

easy to develop and implement PIC microcontroller like the one used in this design PIC

16F877A program in C language due to its flexibility, easiness of Programming and

debugging. After writing the program code it was burned to the microcontroller using

the Pickit 2 programmer.

The flow chart of the program is shown in Figure 3.11 below. The code execution starts

by initializing ports, LCD module and setting all analogue channels off. Next, variables

used in codding are defined and interrupt function called. By using interrupt function to

monitor the input from the 4 channel DIP switch the microcontroller is able to respond

to user command without affecting the normal execution of the program.

Main function which defines the start of execution code is now called and pulse width

modulation modules of the microcontroller initialized. If input issued by the driver

changes the code executes a switch function where the command is compared among

41

YES NO

YES

NO

YES

NO

NO

YES

START

INITIALIZE LCD MODULE INITIALIZE MICROCONTROLLER PORTS INITIALIZE PWM1 & PWM2 MODULES

DEFINE VARIABLES

START EXECUTING INTERRUPT FUNCTION

IF INPUT ≠ OLD INPUT?

SWITCH INPUT = 48?

START PWM1 STOP PWM2 SET RC1 BIT TO HIGH SET RC2 BIT TO LOW PRINT MOTOR STATUS TO LCD

IF RBO BIT = 0?

INCREASE DUTY CYCLE PRINT SPEED

SWITCH INPUT = 80?

C1

C2

C3

42

YES

YES

NO

START PWM2 STOP PWM1 SET RC2 BIT TO HIGH SET RC1 BIT TO LOW PRINT MOTOR STATUS TO LCD

IF RBO BIT = 0?

INCREASE DUTY CYCLE PRINT SPEED

C1

C2 C3

DEFAULT STOP PWM2 STOP PWM1 SET RC2 BIT TO LOW SET RC1 BIT TO LOW PRINT MOTOR STATUS TO LCD

STOP

OLD INPUT = INPUT

Figure 3.11 flow chart

43

different cases and if any one of them matches the input condition the code sequence in

it is executed hence driving the car either forward or reverse or regenerative braking.

The interrupt function takes advantage of provided RB0 external interrupt and port B

<4-7> pins interrupt capabilities. If the status of those pins change at any given time the

interrupt function will update the input variable therefor making the program able to

respond to the new command from the driver immediately. LEDs with different colors

are connected to port E which has three pins. These LEDs are used to indicate the status

of the car green when the car is engaged in forward drive, yellow when the car is

reversing and red when it’s braking.

44

4 RESULTS

4.1 SIMULATION

4.1.1 CIRCUIT DIAGRAM

Figure 4.1 circuit diagram

45

4.1.2 CIRCUIT DESCRIPTION

Simulation of the PWM DC motor control circuit was carried out using Proteus

simulation software version 8.1 .Various blocks of the circuit were interconnected and

virtual instruments of the simulator used to observe and analyze results. Compiled hex

file from mikroc pro was attached to the properties of the microcontroller.

Pins 13 and 14 of the microcontroller are connected to 8MHz quartz crystal. A stable 5

volts to power the microcontroller was provided from the output of 7805 IC voltage

regulator. The LEDs connected in pin 8, 9 and 10 color green, blue and red respectively

will light green to indicate that the car is moving forward, blue when the car is

reversing and red when braking. Also, another green led was connected to the power

supply to show when the power is switched on and go off when the power is

disconnected.

Pins 37, 38, 39 and 40 of microcontroller was programmed as input ports and 4 way dip

switch connected. When pin 40 is in logic low the car will be engaged in forward drive

and it can be accelerated by setting pin 37 low or decelerated by setting pin 38 low.

Likewise, reverse driving can be engaged by setting pin 39 to logic low. During forward

driving pin 16 and 18 will output low state which will in turn switch off transistor Q2

and Q4 pin 23 will be high to switch on transistor Q4 and pin 17 will output a pulse

width modulated signal at a frequency of 5 kHz to drive transistor Q1. To reverse the

car pin 23 and 17 will be off, pin 18 will be on and pin 16 will output a pulse width

modulated signal of 5 kHz this way current will flow in opposite direction.

During simulation IR2112 IC is used instead of IR2110 but there function are similar

and they do operate the same way. Pins 10 and pin 12 receive logic inputs from the

microcontroller to drive high side and low side Mosfet respectively. Signal from pin 12

is passed to pin 1 just as it is without being stepped up and from pin 1 is connected to

low side Mosfet gate through a gate resistor. That from pin 10 is used to charge and

discharge bootstrap capacitor which in turn provides the much needed high voltage to

drive high side Mosfet through gate resistor.

In order to observe regenerative braking led was connected between 12V power rail of

H-bridge and battery with its cathode connected to positive terminal of the battery. This

is made possible by use of relay which is controlled by pin 25 of the microcontroller to

bypass the led during motoring state and connect to led during regenerative state.

When the performance of the circuit was analyzed for different conditions. The circuit

was able to drive the car up to maximum speed.

46

4.2 SIMULATION RESULTS

The working model of the proposed PWM based DC motor control for electric vehicle

using a microcontroller was successfully designed, simulated and implemented on a

breadboard.

4.2.1 POWER SUPPLY OUTPUT

Using proteus virtual voltmeter the supply voltage which is very important for

successful implementation of this project was tested and analyzed. The circuit was

found to generate a stable 5V dc supply from input voltage of 12V from battery.

Figure 4.2 voltage regulator output

4.2.2 MICROCONTROLLER OUTPUTS

.

Figure 4.3 forward drive microcontroller output

47

Using virtual oscilloscope of the proteus the outputs of microcontroller was observed as

the forward drive mode was engaged. The results was as shown in Figure 4.3 above.

Channel A which is of color yellow was connected to pin 17 which is generating a PWM

signal of 5 kHz and its duty cycle was observed to be varying as the speed increases.

Channel B and channel C are off and Chanel D which is connected to pin 23 supposed to

switch on transistor Q4 is on as expected

4.2.3 LCD DISPLAY

The LCD display results was taken for different driving mode and speed as shown in

figures below captured from the screen display when simulation was paused. Also LED

indicators were captured showing the driver which mode is engaged.

Figure 4.4 forward driving LCD display

Figure 4.5 reverse driving LCD display

48

Figure 4.6 regenerative braking LCD display

4.2.4 H-BRIDGE OUTPUTS

The output of the H-bridge was measured and captured for the different driving mode

using virtual digital oscilloscope as shown in figures below

4.2.4.1 FORWARD MODE

Figure 4.7 H-bridge output forward mode

49

4.2.4.2 REVERSE MODE

Figure 4.8 H-bridge output reverse mode

50

4.3 EXPERIMENTAL RESULT

After simulation and determination of specifications of the overall design, a prototype

was built of the final circuit as shown below Figure 4.9. First a preliminary prototype

was constructed on a breadboard to test the components before being soldered

permanent on a PCB. MOSFETs are attached to heat-sinks due to their nature of

generating heat especially at high switching frequency. When testing on breadboard the

motor had not been mounted on the car and hence regenerative braking could not be

observed since it had no momentum to keep it rotating when the supply is cut off

Figure 4.9 breadboard constructed circuit

After carefully wiring the circuit, checking component polarities and layout of the

various segments of the construction were separately tested for their workability. The

output of the microcontroller was observed using laboratory oscilloscope before

connecting the circuit to ensure that control signals were being generated as required.

51

The output of the voltage regulator was measured using laboratory digital multi-meter

and it was found to output constant 5V dc as needed. Next the H-bridge output was

tested using laboratory oscilloscope and the results captured. The resistors and

capacitors were tested to verify their value before the start of construction. After caring

out all the necessary testing, the project was found to be working well and suitable for

driving an electric car.

The performance of the module was analyzed for different conditions. The dc motor

was able to rotate to a speed of up to 200 RPM and perfectly controlled by

microcontroller to rotate in either direction at specified speed.

4.3.1 MICROCONTROLLER OUTPUT WHEN IN FORWARD MODE

The Figure 4.10 below shows the microcontroller pin output as displayed by laboratory

oscilloscope when the prototype was used to drive the car forward.

Figure 4.10 PWM signal generated by microcontroller

52

4.3.2 OUTPUT WHEN THE CAR IS MOVING FORWARD

Figure 4.11 H-bridge output using oscilloscope

Figure 4.12 LCD and LEDs output

53

4.3.3 OUTPUT WHEN REVERSE DRIVING

Figure 4.13 H-bridge output reverse driving

Figure 4.14 LCD and LED output

54

5 CONCLUSION

Applications of high performance DC motor drives in area such as electric elevators,

electric vehicle, electric trains and electric motorcycles require direction and speed

control to perform tasks. DC motors have direction and a speed control capability,

which means that speed and direction of rotation can be changed at any time to meet

new condition.

The aim of this work which is to design a PWM based DC motor control for electric

vehicle using a microcontroller to control the direction and speed of a vehicle has been

achieved. By reversing the polarity of DC motor contacts, the direction of a DC motor

can be reversed. Also varying the PWM signal from microcontroller to the motor driver,

motor speed can be controlled.

In conclusion, the overall aim of this project was met, a fully functional electric vehicle

with regenerative braking was built. The vehicle was further made user friendly by in

cooperating LCD display which shows the driver the speed at which he or she is driving

at and also the gear engaged. Ultimately the limiting factor was time. Anyone continuing

this project in the future should think about reworking the circuitry so that available

power stored in the battery can be displayed and warnings can be issued to the driver

whenever this power is too law, by doing so the driver will be able to plan for his or her

journey in advance.

55

REFERENCES

[1] A. T. B.L Theraja, ELECTRICAL TECHNOLOGY, New Delhi: S. chand and company

Ltd, 2005.

[2] Mehrdad Ehsani,Yimin Gao,Sebastien E. Gay, Ali Emadi, Modern Electric,Hybrid

Electric and Fuel Cell Vehicles, United States of America: CRC Press LLC, 2005.

[3] wikipedia, "Railway_electric_traction," [Online]. Available:

http://en.wikipedia.org/wiki/Railway_electric_traction. [Accessed Feb 2015].

[4] s. freg, "Railway electrification system and engineering," White Word Publications,

2012.

[5] E. Schaal, "electric-motorcycles-with-over-130-miles-of-range," 2014. [Online].

Available: http://wallstcheatsheet.com/automobiles/5-electric-motorcycles-with-

over-130-miles-of-range.html/?a=viewall. [Accessed Feb 2015].

[6] ZEV, "ZEV LRC," [Online]. Available: http://zelectricvehicle.com/22.html.

[Accessed Feb 2015].

[7] wikipedia, "Elevator," [Online]. Available: http://en.wikipedia.org/wiki/Elevator.

[Accessed Feb 2015].

[8] N. R. Council, "Transitions to Alternative Transportation Technologies-Plug-in

Hybrid Electric Vehicles," The National Academies Press, 2010.

[9] wikipedia, "Internal_combustion_engine," [Online]. Available:

http://en.wikipedia.org/wiki/Internal_combustion_engine. [Accessed 9 Feb 2015].

[10] wikipedia, "Electric_car," [Online]. Available:

http://en.wikipedia.org/wiki/Electric_car. [Accessed Feb 2015].

[11] jeff cobb, "hybrid cars," [Online]. Available: http://www.hybridcars.com/the-

three-main-types-of-hybrids-explained/. [Accessed Feb 2015].

[12] wikipedia, "Hybrid electric vehicle," [Online]. Available:

http://en.wikipedia.org/wiki/Hybrid_electric_vehicle. [Accessed Feb 2015].

[13] "Electrical 4you," [Online]. Available: http://electrical4u.com/types-of-dc-motor-

separately-excited-shunt-series-compound-dc-motor/. [Accessed feb 2015].

[14] I. F. C. a. H. F. Leung, "PWM Techniques," A Pure Sine Wave Inverter.

[15] M. H. Rashid, Power Electronics Circuits, Devices and Applications, Prentice-Hall of

India.

[16] Texas instruments, "IR2110".datasheet.

[17] International rectifier, "Application note AN-978".HV Floating MOS-gate driver ICs.

56

[18] N. S. Nise, control system engineering, 2015.

[19] D. S. C. Hsiung, "The Use of PIC Microcontrollers in Multiple DC Motors Control

Applications," Journal of Industrial Technology, vol. 23, 2007.

[20] M. Verle, PIC Microcontrollers - Programming in C, mikroElektronika, 2009.

[21] microchip, "PIC16F87XA".datasheet.

[22] M. Verle, PIC Microcontrollers - Programming in C, mikroElektronika; 1st edition ,

2009.

[23] HITACHI, "LM016L," datasheet, 2015.

[24] Texas Instrument, "LM78XX".datasheet.

57

APPENDIX

PROGRAM CODE

// LCD module connections

sbit LCD_RS at RD2_bit;

sbit LCD_EN at RD3_bit;

sbit LCD_D4 at RD4_bit;

sbit LCD_D5 at RD5_bit;

sbit LCD_D6 at RD6_bit;

sbit LCD_D7 at RD7_bit;

sbit LCD_RS_Direction at TRISD2_bit;

sbit LCD_EN_Direction at TRISD3_bit;

sbit LCD_D4_Direction at TRISD4_bit;

sbit LCD_D5_Direction at TRISD5_bit;

sbit LCD_D6_Direction at TRISD6_bit;

sbit LCD_D7_Direction at TRISD7_bit;

// End LCD module connections

// VARIABLE DEFINITION

short int input, old_input;

signed int SPEED1=0, A;

unsigned int duty_cycle, B ;

char txt1[] = "FORWARD DRIVING";

char txt2[] = "REVERSE DRIVING";

char txt5[] = "BRAKE.SPEED=";

char txt6[] = "REGENERATIVE";

char txt8[] = "SPEED=";

char txt9[] = "RPM";

char SPEED[7];

char *txt10;

// INTERRUPT FUNCTION

void interrupt () {

if (INTCON.RBIF == 1) {

input = PORTB>>5 ; // read portB shifted left 5 bits

INTCON.RBIF = 0; // Clear interrupt flag

} //end intcon.RBIF if

} //end Interrupt

58

// MAIN FUNCTION

void main(){

ADCON1 = 0; // Configure AN pins as digital I/O

OPTION_REG.B7=0; // ENABLE WEAK PULL-UP RESISTOR OF PORT B

TRISB = 0b11110000; // CONFIGURE PORT B INPUT AND OUTPUT PINS

TRISC = 0; // CONFIGURE PORT C PINS AS OUTPUT

TRISD = 0; // CONFIGURE PORT D PINS AS OUTPUT

TRISE = 0; // CONFIGURE PORT E PINS AS OUTPUT

PORTB = 0; // INITIALIZE PORT B

PORTC = 0b01000000; // INITIALIZE PORT C & SWITCH OFF RELAY

PORTD = 0; // INITIALIZE PORT D

PORTE = 0; // INITIALIZE PORT E

INTCON.RBIF = 0; // Clear interrupt flag prior to enable

INTCON.RBIE = 1; // enable on change interrupts

INTCON.GIE = 1; // enable Global interrupts

PWM1_start(); //START PWM1

PWM2_start(); //START PWM2

PWM1_Init(5000); // Initialize PWM1 module at 5KHz

PWM2_Init(5000); // Initialize PWM2 module at 5KHz

Lcd_Init(); // Initialize LCD

Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off

duty_cycle = 0;

while (1) {

if ((input != old_input )||(RB4_bit == 0)){

switch (input) {

case 3:

RC6_BIT = 1; // SWITCH OFF RELAY

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Out(1, 1, txt1); // Write message text on LCD

Lcd_Out(2, 1, txt8); // Write message text on LCD

RE1_bit = 0; // SWITCH OF REVERSE INDICATOR

RE2_bit = 0; // SWITCH OF BRAKE INDICATOR

RE0_bit = 1; // INDICATE THAT THE FORWARD GEAR IS ENGAGED

RC3_bit = 0; // SWITCH OFF Q2

PWM2_Stop(); // SWITCH OFF Q3

RC1_bit = 0; // FORCE Q3 TO 0

if (SPEED1 < 0) { // CHECK IF THE CAR IS MOVING FORWARD

59

SPEED1 = 0; // IF NOT RESET THE SPEED TO ZERO

duty_cycle = 0; // RESET DUTY CYCLE TOO

}

delay_us(100); // WAIT FOR THE TRANSISTORS TO RESPOND

RC4_bit = 1; // SWITCH ON Q4

PWM1_start(); //START PWM1 TO DRIVE Q1 PIN

if (RB4_bit == 0) { // CHECK FOR THE ACCELERATOR PADDLE

for ( B = duty_cycle ; B < 100; B += 1) {

duty_cycle += 1;

PWM1_Set_Duty( duty_cycle*2.55); // Set current duty for PWM1

SPEED1 += 2;

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,9,txt10);

Lcd_Out(2,14,txt9);

delay_us(60);

if (SPEED1 == 200){

Lcd_Out(2,1,"MAXI SPEED 200 ");

while (RB4_BIT == 0){}

}

if ( RB4_bit == 1){

B = 101;

}

}

} else {

PWM1_Set_Duty( duty_cycle*2.55); // Set current duty for PWM1

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,9,txt10);

Lcd_Out(2,14,txt9);

}

break;

case 5:

RC6_BIT = 1; // SWITCH OFF RELAY

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Out(1, 1, txt2); // Write message text on LCD

Lcd_Out(2, 1, txt8); // Write message text on LCD

60

RE0_bit = 0; // SWITCH OFF FORWARD INDICATOR

RE2_bit = 0; // SWITCH OFF BRAKE INDICATOR

RE1_bit = 1; // SWITCH ON REVERSE INDICATOR

RC4_bit = 0;

PWM1_Stop();

RC2_bit = 0;

if (SPEED1 > 0) {

SPEED1 = 0;

duty_cycle = 0;

}

delay_us(100);

RC3_bit = 1;

PWM2_start(); //START PWM2

if (RB4_bit == 0) {

for ( B = duty_cycle ; B < 100; B += 1) {

duty_cycle += 1;

PWM2_Set_Duty( duty_cycle*2.55); // Set current duty for PWM1

SPEED1 -= 2;

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,9,txt10);

Lcd_Out(2,14,txt9);

delay_us(60);

if (SPEED1 == -200){

Lcd_Out(2,1,"MAXI SPEED -200 ");

while (RB4_BIT == 0){}

}

if (RB4_bit == 1){

B = 101;

}

}

} else {

PWM2_Set_Duty( duty_cycle*2.55); // Set current duty for PWM1

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,9,txt10);

Lcd_Out(2,14,txt9);

}

61

break;

default:

PWM1_Stop();

PWM2_Stop();

RC1_bit = 0;

RC2_bit = 0;

RC3_bit = 0;

RC4_bit = 0;

RE0_bit = 0; // SWITCH OFF FORWARD INDICATOR

RE1_bit = 0; // SWITCH 0FF REVERSE INDICATOR

RE2_bit = 1; // SWITCH ON BRAKE INDICATOR

if (SPEED1 > 0) {

RC6_BIT = 0; // SWITCH ON RELAY

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Out(1, 1, txt6); // Write message text on LCD

Lcd_Out(2, 1, txt5); // Write message text on LCD

A = SPEED1;

while (A>0) {

SPEED1 -= 2;

duty_cycle -= 1;

A-= 2;

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,13,txt10);

//delay_us(6);

if (RB5_bit == 1){

A = -10;

}

}

RC6_BIT = 1; // SWITCH OFF RELAY

}else if (SPEED1 < 0) {

RC6_BIT = 0; // SWITCH ON RELAY

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Out(1, 1, txt6); // Write message text on LCD

Lcd_Out(2, 1, txt5); // Write message text on LCD

A = SPEED1;

while( A<=-2 ) {

SPEED1 += 2;

62

duty_cycle -= 1;

A+= 2;

if (A >= 0){

SPEED1 = 0;

}

IntToStr(SPEED1, SPEED);

txt10 = Ltrim(SPEED);

Lcd_Out(2,13,txt10);

//delay_us(6);

if (RB5_bit == 1){

A = 10;

}

}

RC6_BIT = 1; // SWITCH OFF RELAY

} else {

RC6_BIT = 1; // SWITCH OFF RELAY

Lcd_Cmd(_LCD_CLEAR); // Clear display

Lcd_Out(1, 1, txt6); // Write message text on LCD

Lcd_Out(2, 1, txt5); // Write message text on LCD

Lcd_Out(2,13,"0 ");

}

break;

}

old_input = input;

}

}

}

63

LIST OF MATERIALS

Design Title

Author

Revision

Design Created Sunday, March 22, 2015

Design Last Modified Wednesday, April 22, 2015

Total Parts In Design 57

Category Quantity References Value rating Unit Cost

Capacitors 2 C1,C2 22pF 50V 10.00

Capacitors 2 C3,C4 1uF 50V 10.00

Capacitors 2 C5,C6 100nF 50V 10.00

Capacitors 2 C7,C8 0.1uF 50V 10.00

Resistors 1 R1 10k 2-Jan 5.00

Resistors 4 R2,R3,R4,R5 100 2-Jan 5.00

Resistors 4 R6,R7,R8,R9 100k 2-Jan 5.00

Resistors 2 R10,R17 330 5.00

Resistors 3 R14,R15,R16 330 2-Jan 5.00

Resistors 1 R18 10k 5.00

Resistors 2 R19,R20 4.7k 5.00

Integrated Circuits 1 U1 PIC16F877A 600.00

Integrated Circuits 2 U2,U3 IR2112 200.00

Integrated Circuits 1 U4 7805 25.00

Transistors 4 Q1,Q2,Q3,Q4 IRF540 100V 100.00

Transistors 2 Q5,Q6 BC547 5.00

Diodes 6 D1,D2,D3,D4,D5,D61N4002 1A 40.00

Diodes 1 D7 LED-GREEN 20mA 10.00

Diodes 1 D8 LED-BLUE 20mA 10.00

Diodes 1 D9 LED-RED 20mA 10.00

Diodes 1 D10 1N4148 40.00

Diodes 1 D11 LED-yellow 10.00

Diodes 1 D12 LED-yello 10.00

Miscellaneous 3 BATT,MOTOR,SPEEDCONN-SIL3 10.00

Miscellaneous 1 BATTERY 12V 2000.00

Miscellaneous 1 DC MOTOR 12V 200RPM 1600.00

Miscellaneous 1 LCD1 LM016L 400.00

Miscellaneous 1 PUSH CONN-DIL8 10.00

Miscellaneous 1 RL1 G5CLE-1-DC5 5.00

Miscellaneous 1 RV1 1k 2-Jan 25.00

Miscellaneous 1 X1 CRYSTAL 50.00

electric vehicle

towett festus

Bill Of Materials