Motor Control - VE2013

Efficient Motor Control Solutions: High Performance Servo Control Reference Designs and Systems Applications

Andrei Cozma, Analog Devices

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Today’s Agenda

Motor control applications and target markets

Motor control strategies

Feedback sensors and circuits

Isolation

ADI high performance servo control FMC board

Using the ADI high performance servo FMC board with Xilinx® FPGAs and Simulink® from Mathworks

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Objectives

Provide insight into the operation of electric motor drive systems and show where ADI technology adds value to the system

Understand motor control strategies and the challenges of designing efficient motor control applications

Show how some ADI motor control solutions can be used with Xilinx FPGAs

Show how some ADI motor control solutions can be used with Simulink from MathWorks®

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Motor Control Applications and Target Markets Section 1

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Electric Motor Applications

Electric motors are used in a wide range of applications Industrial

Medical

Transportation

Automotive

Integrated applications

Communications

Household appliances

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Electric Motor Drives

Motor Drive A system that varies the motor electrical input power to

control the shaft torque, speed, or position.

Types of Drives Application specific drive—designed to run a specific

motor in a specific application (e.g., variable speed pump drive).

Standard drive—designed as a general-purpose motor speed controller capable of running a variety of motors within a given power range.

Servo drive—designed to deliver accurate and high dynamic control of position, speed, or torque down to zero speed. Typically used in automation applications.

High performance servos—designed to deliver best in class accuracy and connectivity. Typically used in CNC and pick and place machines.

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Market Sub Segments in Motor Control Partners and Systems Value from ADI

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High End Servos/CNC

ADI + FPGA Vendors Xilinx

Focus ADI Parts:

Isolation (Gate Drivers/Discrete) AD740x + AMP

RDC + SAR ADC Transceivers

Power Accelerometers/Sensors

Servos and Premium Drives

ADI Has Complete Signal Chain + Select Partners

Focus ADI Parts: ASSPs/SHARC/BF

Isolation (Gate Drivers/Discrete) AD740x + AMP

RDC + SAR ADC Transceivers

Power Accelerometers/Sensors

Standard and Midrange Motor Drives

ADI Has Complete Signal Chain + Select Partners

Focus ADI Parts: ASSPs/BF

Isolation (Gate Drivers/Discrete) AD740x + AMPs RDC + SAR ADC

Transceivers Power

Applications Specific Motor Control

ADI Has Part of Signal

Chain + Select Partners

Focus ADI Parts: ASSPs / ADuC Family

Isolation (Gate Drivers/Discrete) AMPs

SAR ADC Transceivers

Power

Highest Value for High Performance

FPGA and AFE

Market Trends

Save Energy Drive for performance and quality in motor control

More than 40% of global energy consumed by motors

The requirement for higher system efficiency means there is a need to move from standard induction machines to permanent magnet motors

Shift from analog to digital control—focus on highest possible efficiency

Impact of Trends Increases need for new performing technologies on:

converters, amplifiers, processors, isolation, power, interfaces

The need for higher controller performance makes room for new technologies like FPGAs and other advanced controllers to be used in motor control systems

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Motor Control Strategies Section 2

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Brushed DC Motor Control

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Vary the dc supply, and the motor speed will follow the applied voltage

Pulse width modulation Constant amplitude voltage pulses of varying

widths are provided to the motor: the wider the pulse, the more energy transferred to the motor

The frequency of the pulses is high enough that the motor’s inductance averages them, and it runs smooth

A single transistor and diode can control the speed of a dc motor The motor speed (voltage) is proportional to the

transistor ON duty cycle Positive torque only—passive braking

An H-bridge power circuit enables four quadrant control Forward and reverse motion and braking Complementary PWM signals applied to the high

and low side switches in the bridge

A

B C

BLDCCONTROLLER

+

-

HALL

A

HALL

B

HALL

C

Brushless DC Motor Control

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Brushless dc motors windings generate a trapezoidal back EMF synchronized to the position of the rotor magnet.

Hall effect sensors detect the rotor magnet position and provide signals indicating the “flat top” portion for each winding’s back EMF.

Six switching segments can be identified.

Star Connection Control For any one segment, two windings will be in the

“flat top” portion of the back EMF and a third winding will be switching between a positive and negative output.

Electronic control leaves one winding open circuit, connects one winding to the lower dc rail, and controls the voltage applied to the third winding using PWM.

The fill factor of the applied PWM controls the speed of the motor.

A

B C

BLDCCONTROLLER

+

-

HAL

L A

HAL

L B

HAL

L C

Brushless DC Motor Control

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Delta Connection Control For any one segment, two windings are connected

to the positive voltage supply and a third winding is connected to the negative voltage supply.

The fill factor of the applied PWM controls the speed of the motor.

Sensorless control can be achieved by detecting the zero crossings of the BEMF for each phase

Sensorless control benefits Lower system cost Increased reliability

Sensorless control drawbacks BEMF zero crossings can’t be reliably

detected at low motor speeds

AC Motor Control

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Volts per Hertz Control Variable frequency drive for applications like

fans and pumps Fair speed and torque control at a

reasonable cost

Sensorless Vector Control Does not require a speed or position

transducer Better speed regulation and the ability to

produce high starting torque

Flux Vector Control More precise speed and torque control, with

dynamic response Retains the Volts/Hertz core and adds

additional blocks around the core

Field Oriented Control Best speed and torque control available for ac

motors The machine flux and torque are controlled

independently

U

V

W

AC MOTORCONTROLLER

+

-

Ia Ib

Spee

d

Field Oriented Control (FOC)

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Separates and independently controls the motor flux and torque

Applies equally well to dc motors and ac motors and is the reason “dc like” performance can be demonstrated using field oriented control on ac drives

TorqueController

PI

FluxController

PI

Inverse Park

Transform

d,q → α,β

Space Vector PWM

3 Phase Inverter

Forward Clarke

Transform

a,b → α,β

Forward Park

Transform

α,β → d,q

Vsq

Vsd

Vsα

Vsβ

Vsa PWM

Vsb PWM

Vsc PWM

AC Motor

isa

isb

isα

isβ

isd

isq

Vsq

Vsd

VsqRef

VsdRef

_+

+_

VDC

Rotor Flux Angle θ

Feedback Sensors and Circuits Section 3

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Current and Voltage Sensing

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Shunt Resistor Linear, wide BW, zero offset Power loss at high currents and

no isolation Current Transformer Isolating AC only with poor linearity at low current

Hall Effect Current Sensor Isolating, dc operation and less expensive

than CT Nonlinearity and zero offset

Nulling Hall Effect Sensor Isolating, dc operation and better linearity

than HE sensor More expensive and zero offset Voltage isolation Used to remove CM signal from dc bus,

motor voltage, and current shunt voltages

Isolating

Shaft Position and Speed Sensing Devices

Speed AC and DC tachometers are permanent

magnet generators that produce a voltage proportional to speed.

The ac tachometer output frequency is also proportional to speed.

Commutation (Rotor Angle) Brushless dc motors require low

resolution feedback derived from the motor magnets using Hall effect sensors.

A Hall effect based magnetic encoder generates a pulse train for speed and incremental position.

Precision Shaft Angle Optical encoders with precision pattern

printed on a glass disk provide very high resolution shaft position and speed data.

Resolvers generate sine/cosine relative to position. They are the analog counterpart of the rotary encoder.

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Sensorless Control

Eliminate mechanical speed/position sensors by calculating feedback signal from other information Often used for rotor position estimation in PMSM and BLDC motors Very useful in estimating rotor flux position in ACIM FOC control In some cases, can provide better results than real sensors

Techniques BEMF detection to estimate rotor position in BLDC motor control Rotor angle detection based on motor model using measured phases currents

and voltages

Problems Variation of motor/model parameters over time, temperature Usually need special handling of low speed/zero speed and/or start-up

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Isolation Section 4

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Safety and Functional Isolation

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Functional isolation protects electronic control circuits from damaging voltages Isolate high voltage output from control circuits

connected to Power_GND Safety isolation protects the user from dangerous

voltages Protects user and electronic circuits International standard apply Typically requires double insulation barrier: single

device with two insulating layers OR two single insulating layer devices in path to EARTH

Isolation options Isolate power circuits from the control and user I/O

circuits Common in “noisy” high power systems Required when there is high BW communications

between control and communications process Isolate power and control circuits from user I/O

circuits Common in low power systems Simplifies signal isolation when there is limited

communications between control and user

Motor Control Signal Isolation—Isolated Power Circuit Feedback isolation Measure winding current using

isolating ADC Isolated RS-485 position data from

encoder ASIC

Inverter drive isolation Isolated high- and low-side gate

drivers

DC bus signal isolation Serial I2C ADC for analog signal

isolation Digital isolation of hardware trip

signals

Field Bus isolation Isolate CAN outputs from field bus

network

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ADI High Performance Servo Control FMC Solution Section 5

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FPGAs in Motor Control

FPGAs are becoming more popular for motor control Wide integration capabilities Higher performance, reduced latency Cost reduction

FPGAs are used in a large number of industry fields for efficient motor control Industrial servos and drives Manufacturing, assembly, and automation Medical diagnostic Surgical assist robotics Video surveillance and machine vision Power efficient drives for transportation

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ADI FMC High Performance Servo Solution

Purpose Provide an efficient motor control solution for different types of

electric motors Address power and isolation challenges encountered in motor

control application Provide accurate measurement of motor feedback signals FPGA interfacing capability

Added Value Complete control solution showing how to integrate hardware for: Power Isolation Measurement Control

Increased control flexibility due to FPGA interfacing capabilities Increased versatility to be able to control different types of

motors Example reference designs showing how to use the control

solution with Xilinx FPGAs and Simulink

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ADI FMC High Performance Servo Solution

Drive Board Drives BLDC / PMSM / Brushed DC / Stepper motors Drives motors up to 48V at 18A Integrated over current protection Current measurement using isolated ADCs Bus voltage, phase currents and total current analog

feedback signals PGAs to maximize the current measurement input rage BEMF zero cross detection for sensorless control of

PMSM or BLDC motors

Controller Board Compatible with all Xilinx FPGA platforms with FMC

LPC or HPC connectors 2 x Gbit Ethernet PHYs for high speed industrial

communication Hall + Differential Hall + Encoder + Resolver interfaces Current and voltage measurement using isolated ADCs Xilinx XADC interface Fully isolated control and feedback signals

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ADI FMC Controller Board Block Diagram

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ADI Low Voltage Drive Board Block Diagram

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Key Parts Features That Improve System Performance Efficient Motor Control Prerequisites High quality power sources Reliable power, control, and feedback signals isolation Accurate currents and voltages measurements High speed interfaces for control signals to allow fast controller response

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Measurement AD7401A 5 kV rms, isolated 2nd order Sigma-Delta modulator

AD8207 Zero drift, high voltage, bidirectional difference amplifier

AD8137 Low cost, low power differential ADC driver

Power ADuM5000 isoPower® integrated isolated dc-to-dc converter

ADP1614 1000 mA, 2.5 MHz buck-boost dc-to-dc converter

ADP1621 Low quiescent current, CMOS linear regulator

Isolation ADuM7640 Triple channel digital isolator

Voltage Translation ADG3308 8-channel bidirectional level translator

AD7400A/7401A: 5 kV rms, Isolated 2nd Order Sigma-Delta Modulator Features High performance isolated ADC 16-bit NMC ±2 LSB (typ) INL with 16-bit resolution 1.5 mV/°C (typ) offset drift

±250 mV differential analog input −40°C to +125°C operating temperature

range 5 kV rms, isolation rating (per UL 1577) Maximum continuous working voltages 565 V pk-pk: ac voltage bipolar waveform 891 V pk-pk: ac voltage unipolar

waveform (CSA/VDE) 891 V: dc (CSA/VDE)

Ideal for motor control and dc-to-ac inverters Shunt resistor current feedback sensing Isolated voltage measurement

External clocked version simplifies synchronization

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Product Data Rate Clock SNR ENOB INL Package AD7400A 10 MHz Internal 80 dB 12.5 ±2 LSB SOIC-16

Gull Wing-8 AD7401A 20 MHz External 83 dB 13.3 ±1.5 LSB SOIC-16

AD8207: Zero-Drift, High Voltage, Bidirectional Difference Amplifier Features Ideal for current shunt applications EMI filters included 1 μV/°C maximum input offset drift High common-mode voltage range −4 V to +65 V operating (5 V supply) −4 V to +35 V operating (3.3 V supply) −25 V to +75 V survival

Gain = 20 V/V 3.3 V to 5.5 V supply range Wide operating temperature range: −40°C to

+125°C Bidirectional current monitoring <500 nV/°C typical offset drift <10 ppm/°C typical gain drift >90 dB CMRR dc to 10 kHz Qualified for automotive applications

Applications High-side current sensing in Motor control Solenoid control Engine management Electric power steering Suspension control Vehicle dynamic control DC-to-DC converters

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ADuM5000: Isolated DC-to-DC Converter

Features isoPower® integrated isolated dc-to-dc

converter Regulated 3.3 V or 5 V output Up to 500 mW output power 16-lead SOIC package with >8 mm

creepage High temperature operation 105°C maximum

High common-mode transient immunity >25 kV/μs

Thermal overload protection Safety and regulatory approvals UL recognition 2500 V rms for 1 minute per UL 1577 CSA component accept notice #5A

(pending)

Applications RS-232/RS-422/RS-485 transceivers Industrial field bus isolation Power supply startups and gate drives Isolated sensor interfaces Industrial PLCs

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ADP1614: 650 kHz/1.3 MHz, 4 A, Step-Up, PWM, DC-to-DC Switching Converter Features Adjustable and fixed current-limit options: Adjustable up to 4 A Fixed 3 A 2.5 V to 5.5 V input voltage range 650 kHz or 1.3 MHz fixed frequency option Adjustable output voltage, up to 20 V Adjustable soft start Undervoltage lockout Thermal shutdown 3 mm × 3 mm, 10-lead LFCSP Supported by ADIsimPower design tool

Applications TFT LCD bias supplies Portable applications Industrial/instrumentation equipment

Design tools ADIsimPower - DC-DC Power

Management design tool

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ADuM7640: 1 kV RMS Six-Channel Digital Isolator Features Small 20-lead QSOP 1000 V rms isolation rating Safety and regulatory approvals (pending): UL recognition (pending) 1000 V rms for

1 minute per UL 1577 Low power operation 3.3 V operation 1.6 mA per channel maximum at 0 Mbps

to 1 Mbps 7.8 mA per channel maximum at 25Mbps

5 V operation 2.2mA per channel maximum at 0 Mbps

to 1 Mbps 11.2mA per channel maximum at 25Mbps

Bidirectional communication Up to 25 Mbps data rate (NRZ)

3 V / 5 V level translation High temperature operation: 105°C High common-mode transient immunity:

>15 kV/μs

Applications General-purpose, multichannel isolation SPI interface/data converter isolation RS-232/RS-422/RS-485 transceivers Industrial field bus isolation

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ADG3308: Low Voltage, 1.15 V to 5.5 V, 8-Channel Bidirectional Logic Level Translator Features Bidirectional logic level translation Operates from 1.15 V to 5.5 V Low quiescent current < 1 μA No direction pin

Applications Low voltage ASIC level translation Smart card readers Cell phones and cell phone cradles Portable communication devices Telecommunications equipment Network switches and routers Storage systems (SAN/NAS) Computing/server applications GPS Portable POS systems Low cost serial interfaces

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Using the ADI High Performance Servo FMC Platform with Xilinx FPGAs and Simulink Section 6

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ADI High Performance Servo Development Platform Target FPGA Platforms Xilinx Virtex FPGA platforms Xilinx Kintex FPGA platforms Xilinx Zynq FPGA platforms

Control Algorithms Simulink models for controller ready for code

generation using HDL Coder™ from MathWorks and Xilinx System Generator

Reference design showing BLDC motor speed control

Reference design showing BLDC motor speed and torque control

Simulation and Monitoring Controller simulation and tuning in Simulink ChipScope™ interface for internal signals

monitoring

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Motor Control Reference Design FPGA Blocks

Motor Controller generated from Simulink 6 State Motor Driver SINC3 Filters for current and voltage

measurement

BEMF position detector Hall position detector ChipScope blocks

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Speed Control Reference Designs

Speed Control Reference Design Target motor: BLDC Speed control using Hall sensors Sensorless speed control using

BEMF Simulink controller model ChipScope interface for internal

signals monitoring

Implementation Flow

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BLDCPID Controller

6 State Motor Driver

Speed Computation

PWM

PositionSpeed

Reference Speed

+

-

Design and Tune the

Motor Controller in

Simulink using the

Xilinx Blockset

Generate the HDL Netlist for the

Simulink Motor Controller using

Xilinx System Generator

Integrate the

Motor Controller HDL Netlist in the

Speed Control Reference Design

Simulink Speed Controller

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Speed Computation

PID Controller

Edge Detection

Simulink Speed Controller

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Speed Computation

PID Controller

Edge Detection

Simulink Speed Controller

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Motor Control Reference Designs

Speed and Torque Control Reference Design Target motor: BLDC Speed and torque control Simulink controller model ChipScope interface for

internal signals monitoring

Implementation Flow

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BLDCPI Speed Controller

6 State Motor Driver

Speed Computation

Current Reference

PositionSpeed

SpeedReference

+

-PID Current Controller

PWM

Current Computation

Total Current Measurement

Total Current

+ -

Design and Tune the

Motor Controller in

Simulink using

Simulink Native Blocks

Generate the HDL Netlist for the

Simulink Motor Controller using

Xilinx System Generator

Integrate the

Motor Controller HDL Netlist in the

Speed and Torque Control Reference Design

Generate the HDL code for the

Motor Controller using

HDL Coder

Replace in the Simulink model the Motor Controller

with Xilinx Black Boxes

containing the HDL generated by

HDL Coder

Simulink Speed and Torque Controller

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Simulink Speed and Torque Controller

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Speed Computation

PI Speed Controller Current Computation

PID Torque Controller

Simulink Speed and Torque Controller

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Simulink Speed and Torque Controller

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Conclusions

The ADI high performance servo development platform showcases a full motor control solution that shows how to integrate all the necessary hardware components for efficient motor control in one system

The FPGA interfacing capabilities provide a high degree of flexibility in developing high performance motor control algorithms

By using the MathWorks simulation and development tools, high performance control algorithms can be developed and simulated on the PC and transferred directly into the FPGA

The ADI motor control reference designs provide a starting point for developing enhanced motor control algorithms using MathWorks and Xilinx FPGAs

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