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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 disciplines
and increased use of computational intelligence
in 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 Measurement
Measurement 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 conductive
wiper that slides against a fixed resistive element.
To measure displacement, a potentiometer is typically
wired in a voltage divider configuration.
A known voltage is applied to the resistor ends. The contact
is attached to the moving object of interest
The output voltage at the contact is proportional to the
displacement. Resistive displacement sensors
Potentiometer types :
•Turn counting dial potentiometer
•Linear motion
•Multi turn Potentiometer
Resistive displacement sensors
Inductive displacement sensors
The coil acts as a source of magnetomotive force that drives the
flux through the magnetic circuit and the air gap. The presence of
the air gap causes a large increase in circuit reluctance and a
corresponding decrease in the flux. Hence, a small variation in the
air 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=0
When 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 phase
of 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 count
value is 5)
A timer
Timer timing diagram (the timing
value 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 the
part 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