Mechatronics Basic Introduction

Mechatronics is as old as the history of modern engineering practice, But at the same time it is as new as few decades.

• The word ‘mechatronics’was introduced in Japan in 1969, spread through Europe in seventies and soon after commonly used in United States.

The development of mechatronics has gone through three stages:

The first stage corresponds to the years around the introduction of

word mechatronics.

During this stage, technologies used in mechatronics systems developed rather independently of each other and individually.

With start of eighties a synergic integration of different technologies started taking place.

A notable example is opto-electronics, an integration of optics and electronics.

The concept of hardware/software co-design also started in this

year.

The third stage, which is considered as start of ‘Mechatronics Age’, starts with the early nineties.

The most notable aspect of this stage are more and more integration of different engineering disciplinesand increased use of computational intelligencein the mechatronics products and systems.

Another important development in the third stage is the

concept of ‘micromechatronis’, i.e., start of miniaturization the components such as microactuators and microsensors.

Mechatronics is therefore not a new branch of engineering, but a newly developed concept that underlines the necessity for integration and intensive interaction between different branches of engineering. The core disciplines of the mechatronics are undoubtedly set by the name, i.e, mechanics

and electronics.

Definition•Now we can give a more formal description for mechatronics:

Mechatronics describes a multi-disciplinary engineering activity,

which has been practiced for a number of years.

It integrates the classical fields of mechanical engineering, electronics engineering and computer science/information

technology at the design stage of a product or a system.

• ‘Mecha 'should be understood as the widest aspects of mechanical engineering,

• whilst'tronics'should be understood to embrace

all aspects of microelectronics, electromechanics (modern electrical drives-motion control), control theory, computer science/engineering and information technology.

A key factor in the mechatronics philosophy is the integration of microelectronics and information technology into mechanical systems, so as to obtain the best possible solution.

Design of such products and processes, therefore, has to be the outcome of a multi-disciplinary activity rather than an interdisciplinary one.

Hence mechatronics challenges the traditional engineering thinking, because the way it is operating, is crossing the boundaries between the traditional engineering disciplines.

DISPLACEMENT,AND

POSITION SENSORS

Displacement MeasurementMeasurement of displacement is the basis of measuring: Position Velocity Acceleration Stress Force Pressure Proximity Thickness

Displacement Sensors types

• Potentiometers displacement sensors

• Inductive displacement sensors

• Capacitive displacement sensors

• Eddy current displacement sensors

• Piezoelectric displacement sensors

• Ultrasonic displacement sensors

• Magnetostrictive displacement sensors

• Optical encoder displacement sensors

• Strain Gages displacement sensors

Resistive displacement sensors: An electrically conductivewiper that slides against a fixed resistive element. To measure displacement, a potentiometer is typicallywired in a voltage divider configuration.

A known voltage is applied to the resistor ends. The contactis attached to the moving object of interest

The output voltage at the contact is proportional to thedisplacement. Resistive displacement sensors

Potentiometer types :•Turn counting dial potentiometer

•Linear motion

•Multi turn Potentiometer

Resistive displacement sensors

Inductive displacement sensorsThe coil acts as a source of magnetomotive force that drives theflux through the magnetic circuit and the air gap. The presence ofthe air gap causes a large increase in circuit reluctance and acorresponding decrease in the flux. Hence, a small variation in theair gap results in a measurable change in inductance.

Single-Coil Linear Variable-Reluctance Sensor

Inductive displacement sensors

Linear Variable Differential Transformer (LVDT)

Motion of a magnetic core changes the mutual inductance of two secondary coils relative to a primary coil Primary coil voltage: VSsin(wt)Secondary coil induced emf:V1=k1sin(wt) and V2=k2sin(wt)k1 and k2 depend on the amount of coupling between the primary and the secondary coils, which is proportional to the position of the coil.

When the coil is in the central position, k1=k2; VOUT=V1-V2=0When the coil is is displaced x units, k1 not equal to k2 ; VOUT=(k1-k2)sin(wt)Positive or negative displacements are determined from the phaseof VOUT.

Linear Variable Differential Transformer (LVDT)

UNIT-II

Unit-IV

Programmable Logic

Controllers

A PLC system: CPU module (left) and an I/O rack (right) (Allen Bradley PLC-5)

(Courtesy of Allen-Bradley)

A small PLC (Allen Bradley MicroLogix 1000)(Courtesy of Allen-Bradley).

Types of switches

A Relay

A counter

Counter timing diagram (the countvalue is 5)

A timer

Timer timing diagram (the timingvalue is 5)

Ladder diagram for the circuit

Wiring diagram

Programmable logic controller system structure

I/O modules (Courtesy of Allen-Bradley)

Power input connections: (a) AC, (b) DC, and (c) TTL

Power output connections: (a) AC, (b) DC, and (c) TTL

Human interface terminal (Courtesy of Allen-Bradley)

PC-based programming software

Some relay diagram symbols

A ladder diagram

PLC wiring diagram

PLC scan

Basic logic

And logic

OR logic

Combine AND and OR logic

Example

Cell layout

Program

Wiring diagram

EXPLANATION OF THE PROGRAM

Rung 1. If a part arrives and no part is stopped, trigger the barcode reader.Rung 2. If it is a right part, activate the stopper.Rung 3. If the stopper is up, the machine is not busy and the robot is not busy; load thepart onto the machine.Rung 4. If the task is completed and the robot is not busy, unload the machine.

Data types

Operators

A up-counter functional block