Post on 17-Mar-2016
description
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 mechatronicswas 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, mechanicsand electronics.
DefinitionNow 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,ANDPOSITION 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-IVProgrammable LogicControllers
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