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MECHATRONICS
U5MEA22
Prepared by
Mr. S Riyaz Ahammed & Mr. Hushein
Assistant Professor, Mechanical Department
VelTech Dr.RR & Dr.SR Technical University
Unit 1
Mechatronics: Mechatronics basically refers to mechanical electrical
systems and is centered on mechanics, electronics,
computing and control which, combined, make
possible the generation of simpler, more economical,
reliable and versatile systems.
•The term "mechatronics" was first assigned by
Mr.Tetsuro Mori, a senior engineer of the Japanese
company Yaskawa, in 1969.
• Mechatronics is the combination of mechanical,
electronic, computer,control engineering's and system
engineering to design and manufacture useful products.
Key Elements
Measurement system
Control Systems
Control Systems are mainly of Two Types
• Open Loop Control Systems
• Closed Loop control Systems
•An open-loop controller, also called a non-feedback
controller.
• Basic difference between two types of systems is
closed loop systems have feed back which makes them
to be good precise control systems or automated
systems.
•PID controller, a commonly used closed-loop controller
Water Level Controller
• Controlled variable- water level in tank
• Reference value- initial setting of float, lever
position
• Comparison element- Lever
• Error signal- Difference between the actual
and initial settings of lever
position
• Control unit- Pivoted lever
• Correction unit- Flap opening or closing water
supply
• Process- water level in the tank
Shaft speed control systems
Description
• Potentiometer is used to set the voltage to be
supplied to the power amplifier.
• Differential amplifier is used to amplify and
compare the feed back value and reference
value.
• Amplified error signal is fed to the motor to
adjust the speed of rotating shaft.
• Tachometer is used to measure the speed of
rotating shaft and speed is fed to amplifier.
Washing Machine control
• Example of an event based sequential control
system is washing machine. Each event of
washing machine may consist of number of
sub events or steps. For example pre wash
cycle, rinse cycle, main cycle, spinning cycle.
• Following figures represent the various events
of washing machine system.
•During Pre wash cycle operation, the inlet valve is
opened when the machine is switched ON and the
valve is closed when the required level of water is filled
in the drum.
Main wash cycle is then started by micro processor by
operating the inlet valve to allow the water in to the
drum.
Water level sensor senses the water level in the drum
and it closes the inlet valve after reaching certain level,
Micro processor switches ON the heating coil in the
drum.
AUTOMATIC CAMERA
• Basic elements of control systems used in
automatic camera are body, lenses and flash.
• Depending up on mode selected, the required
combination of aperture and shutter speed
and focus are automatically taken care by the
camera.
• A typical camera system comprises drives and
sensors, interfaces for lenses, flash and the
user.
• Micro processor systems for lenses, user and
flash are incorporated for controlling various
operations. Micro processor takes input from
range sensor and sends output to lens.
• Position is fed back to micro processor and it
modifies the same.
• Light sensor gives input to micro processor,
When photographer selects shutter controller,
shutter opens up for photograph to be taken.
Engine Management System
• System consists of sensors for supplying, after
suitable signal conditioning, the input signals
to micro controller, and its providing output
signals via drivers to actuate actuators.
• Engine speed sensor is an inductive sensor
and consists of a coil for which inductance
changes as the teeth of the sensor wheel pass
it and so gives oscillating output.
• Temperature sensor is usually a thermistor.
• Mass air flow sensor may be a hot wire sensor,
as air passes over heated wire it will be
cooled, the amount of cooling will depend on
the mass rate of flow.
• Oxygen sensor is generally closed end tube
made of zirconium oxide with porous
platinum electrodes on inner and outer
surfaces.
• Following figure represents an engine
management system
Unit 2
MICROPROCESOR
IN
MECHATRONICS
MICROPROCESSOR
• A microprocessor incorporates the functions
of a computer's central processing unit (CPU)
on a single integrated circuit (IC),or at most a
few integrated circuits. Microprocessor is a
multipurpose, programmable device that
accepts digital data as input, processes it
according to instructions stored in its memory,
and provides results as output
8085 ARCHITECTURE
INPUT AND OUTPUT PERIPHERAL
CIRCUITS
• A peripheral is a device that is connected to a
host computer, but not part of it. It expands the host's
capabilities but does not form part of the
core computer architecture. It is often, but not always,
partially or completely dependent on the host.
• There are three different types of peripherals:
• Input, used to interact with, or send data to the
computer (mouse, keyboards, etc.)
• Output, which provides output to the user from the
computer (monitors, printers, etc.)
• Storage, which stores data processed by the computer
(hard drives, flash drives, etc.)
COMMUNICATIONS-INPUT,OUTPUT
AND MEMORY WITH TIMING
DIAGRAM
• Input/output (I/O) scheduling is the method
that computer operating systems use to
decide which order block I/O operations will
be submitted to storage volumes. I/O
Scheduling is sometimes called 'disk
scheduling'.
PURPOSE
• I/O schedulers can have many purposes depending on
the goal of the I/O scheduler. Some common ones are:
• To minimize time wasted by hard disk seeks
• To prioritize a certain processes' I/O requests
• To give a share of the disk bandwidth to each running
process
• To guarantee that certain requests will be issued before
a particular deadline
A/D CONVERTER
• An analog-to-digital
converter (abbreviated ADC, A/D or A to D) is
a device that converts a continuous physical
quantity (usually voltage) to a digital number
that represents the quantity's amplitude.
• The conversion involves quantization of the
input, so it necessarily introduces a small
amount of error. Instead of doing a single
conversion, an ADC often performs the
conversions ("samples" the input) periodically.
The result is a sequence of digital values that
have converted a continuous-time and
continuous-amplitude analog signal to
a discrete-time and discrete-amplitude digital
signal.
• An ADC may also provide an isolated measurement such as
an electronic device that converts an input
analog voltage or current to a digital number proportional
to the magnitude of the voltage or current. However, some
non-electronic or only partially electronic devices, such
as rotary encoders, can also be considered ADCs. The digital
output may use different coding schemes. Typically the
digital output will be a two's complement binary number
that is proportional to the input, but there are other
possibilities. An encoder, for example, might output a Gray
code.
• The inverse operation is performed by a digital-to-analog
converter (DAC).
ELECTRICAL SYMBOL
• The key parameters to test a SAR ADC are
following:
• DC Offset Error
• DC Gain Error
• Signal to Noise Ratio (SNR)
• Total Harmonic Distortion (THD)
• Integral Non Linearity (INL)
• Differential Non Linearity (DNL)
• Spurious Free Dynamic Range
• Power Dissipation
D/A CONVERTER
• a digital-to-analog converter (DAC or D-to-A)
is a device that converts a digital (usually
binary) code to an analog
signal (current, voltage, or electric charge).
An analog-to-digital converter (ADC) performs
the reverse operation. Signals are easily stored
and transmitted in digital form, but a DAC is
needed for the signal to be recognized by
human senses or other non-digital systems.
• A common use of digital-to-analog converters
is generation of audio signals from digital
information in music players. Digital video
signals are converted to analog
in televisions and mobile phones to display
colors and shades. Digital-to-analog
conversion can degrade a signal, so conversion
details are normally chosen so that the errors
are negligible.
• Due to cost and the need for
matched components, DACs are almost
exclusively manufactured on integrated
circuits (ICs). There are many
DACarchitectures which have different
advantages and disadvantages. The suitability
of a particular DAC for an application is
determined by a variety of measurements
including speed and resolution.
RECENT DEVELOPMENTS IN MICROPROCESSORS AND
CONTROLLERS
•
The recent development In microprocessor technology makes
Implementation of advanced control strategies feasible at the
generating level. A self-tuning (ST) proportional-plus-lntegral-plusderivative (PID) digital automatic voltage regulator (DAVR) for a large
synchronous machine is proposed and the influence of this regulator
on the generator dynamic and transient stability is investigated. The
algorithm for this regulator combines a least-square estimator with a
digital PID control algorithm. The parameters of the PID control
algorithm are computed and updated according to the estimated
model. The dynamic performance of the machine when equipped
with a digital PID governor is also presented. A comparison of the
computer results as obtained from the simulation study are
compared with the available experimental results.
Unit 3
ELECTRICAL DRIVES
AND
CONTROLLERS
Electromagnetic principles
• "When a conductor is exposed to a changing magnetic field, an
electric current will flow in the conductor."
• This principle is the basis for the generation of electricity. In a
typical large-scale operating electrical generator, an armature coil (a
coil of wire of many turns) is wrapped around a soft iron armature
and forced to spin in a powerful electromagnetic field. The spinning
is achieved by forcing high-pressure steam (in a thermal generator),
fast-flowing water (in a hydro generator), or wind (in a wind
generator) across a turbine (similar to a propeller blade) attached to
the end of the armature. As the armature spins, an electric current
is induced (forced) to flow in the armature coil where it is extracted
and sent to the electricity grid that supplies electricity across a
broad area (the province of Ontario and beyond, for example). It is
the direction of flow of this induced current that is addressed by
Lenz's law.
SOLENOIDS
• In physics, the term refers specifically to a
long, thin loop of wire, often wrapped around
a metallic core, which produces a
uniform magnetic field in a volume of space
(where some experiment might be carried
out) when an electric current is passed
through it. Solenoids are important because
they can create controlled magnetic fields and
can be used as electromagnets.
• In engineering, the term may also refer to a
variety of transducer devices that
convert energy into linear motion. The term is
also often used to refer to asolenoid valve, which
is an integrated device containing an
electromechanical solenoid which actuates either
a pneumatic or hydraulic valve, or a solenoid
switch, which is a specific type of relay that
internally uses an electromechanical solenoid to
operate an electrical switch; for example,
an automobile starter solenoid, or a linear
solenoid, which is an electromechanical solenoid.
SOLENOID
RELAYS
• A relay is an electrically operated switch. Many relays
use an electromagnet to operate a switching
mechanism mechanically, but other operating
principles are also used. Relays are used where it is
necessary to control a circuit by a low-power signal
(with complete electrical isolation between control and
controlled circuits), or where several circuits must be
controlled by one signal. The first relays were used in
long distance telegraph circuits, repeating the signal
coming in from one circuit and re-transmitting it to
another. Relays were used extensively in telephone
exchanges and early computers to perform logical
operations.
ELECTROMECHANICAL RELAY
• A type of relay that can handle the high power
required to directly control an electric motor
or other loads is called a contactor. Solid-state
relays control power circuits with no moving
parts, instead using a semiconductor device to
perform switching. Relays with calibrated
operating characteristics and sometimes
multiple operating coils are used to protect
electrical circuits from overload or faults; in
modern electric power systems these
functions are performed by digital instruments
still called "protective relays".
STEPPER MOTORS
• A stepper motor (or step motor) is a brushless
DC electric motor that divides a full rotation
into a number of equal steps. The motor's
position can then be commanded to move
and hold at one of these steps without any
feedback sensor (an open-loop controller), as
long as the motor is carefully sized to the
application.
TYPES OF STEPPER MOTORS
• There are four main types of stepper motors:[1]
• Permanent magnet stepper (can be subdivided
into 'tin-can' and 'hybrid', tin-can being a cheaper
product, and hybrid with higher quality bearings,
smaller step angle, higher power density)
• Hybrid synchronous stepper
• Variable reluctance stepper
• Lavet type stepping motor
SERVO MOTORS
• A servomotor is a rotary actuator that allows for precise
control of angular position, velocity and acceleration. It
consists of a suitable motor coupled to a sensor for position
feedback. It also requires a relatively sophisticated
controller, often a dedicated module designed specifically
for use with servomotors.
• Servomotors are not a different class of motor, on the basis
of fundamental operating principle, but
uses servomechanism to achieve closed loop control with a
generic open loop motor.
• Servomotors are used in applications such
as robotics, CNC machinery or automated manufacturing.
PROGRAMMABLE LOGIC CONTROLLER
• A Programmable Logic
Controller, PLC or Programmable Controller is
a digital computer used
for automation of electromechanical processes,
such as control of machinery on factory assembly
lines, amusement rides, or light fixtures. The
abbreviation "PLC" and the term "Programmable
Logic Controller" are registered trademarks of
the Allen-Bradley Company (Rockwell
Automation).
• PLCs are used in many industries and machines.
Unlike general-purpose computers, the PLC is
designed for multiple inputs and output
arrangements, extended temperature ranges,
immunity to electrical noise, and resistance to
vibration and impact. Programs to control
machine operation are typically stored in batterybacked-up or non-volatile memory. A PLC is an
example of a hard real time system since output
results must be produced in response to input
conditions within a limited time, otherwise
unintended operation will result.
MEMORY- INPUT , OUTPUT MODULES
• In computer architecture, the combination of
the CPU and main memory (i.e. memory that the CPU
can read and write to directly, with
individual instructions) is considered the brain of a
computer, and from that point of view any transfer of
information from or to that combination, for example
to or from a disk drive, is considered I/O. The CPU and
its supporting circuitry providememory-mapped
I/O that is used in low-level computer programming,
such as the implementation of device drivers. An I/O
algorithm is one designed to exploit locality and
perform efficiently when data reside on secondary
storage, such as a disk drive.
TIMERS- INTERNAL RELAYS
• A timer is a clock that controls the sequence
of an event while counting in fixed intervals of
time
• A timer is a specialised type of clock for
measuring time intervals
Counters – shift registers
• In digital circuits a shift register is a cascade of
flip-flops , sharing the same clock, in which
the output of each flip flop is connected to the
data input of next flip flop in the chain
resulting in the circuit that shifts by one
position the bit array stored in it,shifting in the
data present at its input and shifting out the
last bit in the array, at each transition of clock
input.
Counter- timing
PLC- USING LADDER DIAGRAM
A ladder diagram represents a program in
“LADDER LOGIC”
A ladder logic is a method of drawing electrical
logic schematics.
PLC WITH LADDER LOGIC
PLC - APPLICATIONS
Unit 4
Limit Switch
• A limit switch is an electromechanical device
that consists of an actuator mechanically
linked to a set of contacts.
• When an object comes into contact with the
actuator, the device operates the contacts to
make or break an electrical connection.
• It can determine the presence or absence of
an object. It was first used to define the limit
of travel of an object; hence the name "Limit
Switch."
Basic Components
• Actuator: The portion of the switch that comes in
contact with the object being sensed.
• Head: It houses the mechanism that translates
actuator movement into contact movement.
When the actuator is moved as intended, the
mechanism operates the switch contacts.
• Contact Block: It houses the electrical contact
elements of the switch. It typically contains either
two or four contact pairs.
Basic Components (contd.)
• Terminal Block: The terminal block contains the
screw terminations. This is where the electrical
(wire) connection between the switch and the
rest of the control circuit is made.
• Switch Body: The switch body houses the contact
block in a plug-in switch. It and terminal block in
the nonplug-in switch.
• Base: The base houses the terminal block in a
plug-in switch. Nonplug-in switches do not have a
separate base.
Type-1 Nonplug-in Housing
• They are box
shaped with a
separate cover.
• Seals between the
head, body, and
cover are
maintained by an
O-ring and a flat
gasket.
Type-2 Plug-in Housing
• Developed to ease
replacement of the switch
if needed.
• Plug-in housing splits in
half to allow access to the
terminal block for wiring.
• A set of stabs in the
switch body “plugs” into
sockets in the base to
make electrical
connections between the
contact block and the
terminal block.
Encoders
• What is an encoder?
An encoder is a sensor for converting rotary motion or position
to a series of electronic pulses
• Advantages
Simplicity of construction (low cost)
High sensitivity (depending upon the supply voltage)
•
Disadvantages
It includes the familiar drawbacks related to contacting
and communicating devices like friction, wear, brush
bounce due to vibration, signal glitches and metal
oxidation due to electrical arcing.
The types of encoders
• Absolute encoders
• Absolute encoders have a unique code that can be
detected for each angular position
• Absolute encoders are much more complex and expensive
than incremental encoders
The types of encoders
• Incremental encoders
• Pulses from LEDS are counted to provide rotary position
• Two detectors are used to determine direction (quadrature)
• Index pulse used to denote start point
• Otherwise pulses are not unique
Temperature Sensor
• Temperature sensors appear in building, chemical
process plants, engines, appliances, computers, and
many other devices that require temperature
monitoring
• Many physical phenomena depend on temperature,
so we can often measure temperature indirectly by
measuring pressure, volume, electrical resistance,
and strain
Temperature Sensor
• Bimetallic Strip
L  L 0[1   (T - T0)]
Metal A
δ
• Application
– Thermostat (makes or
breaks electrical
connection with
deflection)
Metal B
Temperature Sensor
• Resistance temperature
device.
R  R 0[1   (T - T0)]
R  R0 e
1 1 

 T T0 
 
Position Sensors
Position Sensors is a device that provides the position
measurement of a component. A position sensor can
be:
1.Linear
2.Angular
3.Multi-axis
Some of the well-known position sensors are:
Linear Variable Differential Transformer (LVDT)
Hall Effect Sensor
Proximity Sensor
LDVT-Configuration
• An alternating current is driven
through the primary, causing a
voltage to be induced in each
secondary proportional to its
mutual inductance with the
primary. The frequency is usually
in the range 1 to 10 kHz.
Hall Effect Sensor
•
•
•
The Hall effect was discovered by Edwin Hall in
1879; “electron” was not experimentally
discovered; had to wait until quantum mechanics
came
Development of semiconductor compounds
in 1950's led to first useful Hall effect magnetic
instrument
In the 1960's, first combinations of Hall elements
and integrated amplifiers
–
–
Resulted to classic digital output Hall switch
In 1965, first low-cost solid state sensor
Theory of the “Hall Effect”
Hall effect principle, no
magnetic field
Hall effect principle,
magnetic field present
Potential Difference
(voltage) across output:
V=I*B
Basic Hall Effect Sensor
• Hall element is the basic
magnetic field sensor
• Differential Amplifier
amplifies the potential difference
(Hall voltage)
• Regulator holds current value
so that the output of the sensor
only reflects the intensity of the
magnetic field
• Types
1. Unipolar
2.Latching
3.Bipolar
Proximity Sensor
• A proximity sensor is a sensor able to detect
the presence of nearby objects without any
physical contact.
• These sensors use mutual inductance
between a known inductor and a conductive
material
• Commonly referred to as “eddy current”
probes
• Mutual inductance is a function of the
distance between the inductor and the
material
How “Eddy Currents” Work
• An inductive coil is placed near a
conductive surface
• An AC voltage (typically around
2Mhz) is applied to the coil
• Mutual inductance begins to
occur
• The coil generates a magnetic
field
• Circular or “Eddy Currents” begin
to flow in the conductive material
• These currents resemble an eddy
in a stream of water
How “Eddy Currents” Work
• The Eddy Currents
generate their own
magnetic field
• These fields have
interaction with the coil
through mutual
inductance
• This leads to a
measurable result
What can be measured?
• Electrical conductivity and magnetic
permeability of the target material
• The amount of material cutting through the
coils of the magnetic field
• The condition of the material(whether it
contains cracks or defects
• Lift-Off
Pressure Sensor
•
Two Main Types of Pressure Sensors
Capacitive Sensors
– Work based on measurement of
capacitance from two parallel plates.
– C = εA/d , A = area of plates d =
distance between.
– This implies that the response of a
capacitive sensor is inherently nonlinear. Worsened by diaphragm
deflection.
– Must use external processor to
compensate for non-linearity
Pressure Sensor
Piezoresistive Sensors
•
•
•
•
Work based on the piezoresistive
properties of silicon and other
materials.
Piezoresistivity is a response to stress.
Some piezoresistive materials are Si,
Ge, metals.
In semiconductors, piezoresistivity is
caused by 2 factors: geometry
deformation and resistivity changes.
Pressure Sensing
• Pressure is sensed by mechanical
elements such as plates, shells, and tubes
that are designed and constructed to
deflect when pressure is applied.
• This is the basic mechanism converting displacement
pressure to physical movement.
• Next, this movement must be transduced
to obtain an electrical or other output.
• Finally, signal conditioning may be
electric
needed, depending on the type of sensor
and the application. Figure 8 illustrates
the three functional blocks.
Pressure
Sensing
Element
Transduction
element
Signal
Conditioner
V or I output
Sensing Elements
• The main types of sensing
elements are Bourdon
tubes, diaphragms,
capsules, and bellows
• All except diaphragms
provide a fairly large
displacement that is useful
in mechanical gauges and
for electrical sensors that
require a significant
movement
Potentiometric Pressure Sensors
• Potentiometric pressure sensors
use a Bourdon tube, capsule, or
bellows to drive a wiper arm on a
resistive element.
• For reliable operation the wiper
must bear on the element with
some force, which leads to
repeatability and hysteresis
errors.
• These devices are very low cost,
however, and are used in lowperformance applications such as
dashboard oil pressure gauges
Inductive Pressure Sensors
• Several configurations based on
varying inductance or inductive
coupling are used in pressure
sensors. They all require AC
excitation of the coil(s) and, if a DC
output is desired, subsequent
demodulation and filtering. The
LVDT types have a fairly low
frequency response due to the
necessity of driving the moving core
of the differential transformer
• The LVDT uses the moving core to
vary the inductive coupling
between the transformer primary
and secondary.
Capacitive Pressure Sensors.
• Capacitive pressure sensors typically use a thin diaphragm as
one plate of a capacitor.
• Applied pressure causes the diaphragm to deflect and the
capacitance to change.
• This change may or may not be linear and is typically on the
order of several picofarads out of a total capacitance of 50100 pF.
• The change in capacitance may be used to control the
frequency of an oscillator or to vary the coupling of an AC
signal through a network.
• The electronics for signal conditioning should be located close
to the sensing element to prevent errors due to stray
capacitance.
INTRODUCTION OF TRANSDUCERS
• A transducer is a device that convert one form of energy
to other form. It converts the measurand to a usable
electrical signal.
• In other word it is a device that is capable of converting
the physical quantity into a proportional electrical
quantity such as voltage or current.
Pressure
Voltage
BLOCK DIAGRAM OF TRANSDUCERS
• Transducer contains two parts that are closely related to
each other i.e. the sensing element and transduction
element.
• The sensing element is called as the sensor. It is device
producing measurable response to change in physical
conditions.
• The transduction element convert the sensor output to
suitable electrical form.
CHARACTERISTICS OF TRANSDUCERS
1.
2.
3.
4.
5.
6.
7.
8.
Ruggedness
Linearity
Repeatability
Accuracy
High stability and reliability
Speed of response
Sensitivity
Small size
TRANSDUCERS SELECTION FACTORS
1.
2.
3.
4.
5.
6.
Operating Principle: The transducer are many times selected
on the basis of operating principle used by them. The operating
principle used may be resistive, inductive, capacitive ,
optoelectronic, piezo electric etc.
Sensitivity: The transducer must be sensitive enough to
produce detectable output.
Operating Range: The transducer should maintain the range
requirement and have a good resolution over the entire range.
Accuracy: High accuracy is assured.
Cross sensitivity: It has to be taken into account when
measuring mechanical quantities. There are situation where the
actual quantity is being measured is in one plane and the
transducer is subjected to variation in another plan.
Errors: The transducer should maintain the expected inputoutput relationship as described by the transfer function so as
to avoid errors.
Contd.
7.
Transient and frequency response : The transducer should meet
the desired time domain specification like peak overshoot, rise
time, setting time and small dynamic error.
8. Loading Effects: The transducer should have a high input
impedance and low output impedance to avoid loading effects.
9. Environmental Compatibility: It should be assured that the
transducer selected to work under specified environmental
conditions maintains its input- output relationship and does not
break down.
10. Insensitivity to unwanted signals: The transducer should be
minimally sensitive to unwanted signals and highly sensitive to
desired signals.
CLASSIFICATION OF TRANSDUCERS
The transducers can be classified as:
I.
II.
III.
IV.
V.
Active and passive transducers.
Analog and digital transducers.
On the basis of transduction principle used.
Primary and secondary transducer
Transducers and inverse transducers.
Unit 5
Stages in designing Mechatronics
Systems
Traditional and Mechatronics
Design
• system is partitioned into individual
homogenous subsystems according to the
disciplines,
• homogenous subsystems are designed by
specialists from a design team,
• each homogenous subsystem is designed
by traditional way,
• each product function is from the most
part realized by only one homogenous
subsystem,
• ¾ interactions are minimized, emphasis is
mainly laid on common interfaces of the
subsystems.
• more functions,
• higher efficiency and
reliability,
• lower demands on energy,
• minimal size and weight,
• lower cost.
Engine Management Systems
1.Throttle position
sensor
2.EGO sensor
3.MAP Sensor
4.Temperature
sensor
5.Speed/Timing
Sensor
6.EGR diagnostic
switch
7.EGR valve position sensor
Sensors and actuators in EMS
Pick and Place Robot
• The robot has three axis about which motion can occur.
• The following movements are required for this robot.
1. clockwise and anticlockwise rotation of the robot unit on its base.
2. Linear movement of the arm horizontally i.e., extension or
contraction of arm.
3. Up and down movement of the arm and
4. Open and close movement of the gripper.
• The foresaid movements can be obtained by pneumatic cylinder
which is operated by solenoid valves with limit switches.
• Limits switches are used to indicate when a motion is completed.
• The clockwise rotation of the robot unit on its base can be obtained
from a piston and cylinder arrangement during pistons forward
movement
• v Similarly counter clockwise rotation can be obtained during
backward
• movement of the piston in cylinder.
Control circuit diagram of the pick
and place robot
Automatic car parking system
• Consider an automatic car park system with barriers operated by coin
inserts.
• The system uses a PLC for its operation.
• There are two barriers used namely in barrier and out barrier. In barrier is
used to open when the correct money is inserted while out barrier open
when the car is detected in front of it.
• It shows a schematic arrangement of an automatic car park barrier. It
consists of a barrier which is pivoted at one end, two Solenoid valves A and
B and a piston cylinder arrangement
• A connecting rod connects piston and barrier as shown in fig below
Solenoid valves are used to control the movement of the piston.
• Solenoid A is used to move the piston upward inturn barrier whereas
solenoid B is used to move the piston downward.
• Limit switches are used to
detect the foremost position
of the barrier. When current
flows through solenoid A, the,
piston in the cylinder moves
upward and causes the barrier
to rotate about its pivot and
raises to let a car through
THANK YOU