Download Introduction to Mechatronics

ElectroMechanical Systems
Engr.Talha Ahmed Khan
Introduction
• In 1969 a senior engineer of Japanese company
YASAKAWA first coined the word electromechanical as
a combination of mechanisms and electronics.
• Now a days electrical and elctronic fields are
developing very rapidly like electrical machines,
integrated circuits, microprocessors, microcontrollers,
digital control systems, data communication networks
and so forth.
• Electromechanical is the synergetic integration of
mechanical engineering with electronics and intelligent
computer control in designing, manufacturing process
and production.
Roles Of Various Engineering
Disciplines in Mechatronics
Mechanical Systems
• They are classified as rigid, deformable or fluid in
nature.
• Mechanical systems like hydraulic, pneumatic,
rotational or translational. Thermal, fluid etc are
used in mechatronic applications.
• These systems are interfaced with computers
through sensors, actuators and electronic
systems, control valves, gears, cylinders, chains,
etc are the mechanical components used.
Electrical Systems
• These systems are concerned with the
behavior of three fundamental quantitiescharge, current and voltage.
• Electrical systems are integral part of electromechanical systems.
• Generators,Transformers,relays,circuit
breakers,switches and so on.
Electronic Systems
• In electromechanical systems, electronic
devices are used to design the following
electronic circuits.
• Analog:Circuits designed using
passive(resistors, capacitors and inductors)
and active(diodes,transistors and integrated
circuits) components.
• Digital:Combinational and sequential
circuits(flip-flops, counters etc…)
Instrumentation and Control System
• Instrumentation system covers various
transducers, signal conditioning elements and
output devices such as analog meters, display
devices, recorders and printers.
• Data acquisition system or data loggers are
used for data collecting, processing and
storing.
• Control system is that means by which any
quantity of interest in a machine, mechanism
or equipment is maintained or altered in
accordance with a desired manner.
• It deals with time, frequency domain analysis
and stability of systems.
• It involves control system components such as
stepper motors, synchros, servo motors,
servomechanisms actuators and so forth.
Mechatronic Design Elements
• In mechatronic systems, a sensor in an element,
which accepts the physical quantities(process
variables) from mechanical processes (dynamic
system) and convert them into signal that can be
processed by the system.
• A transducer is defined as a device that converts
physical quantities into an output usually a
voltage.
• The output of sensory system is applied to signal
conditioning elements which are also called as
signal processors.
Fig:1.2 Block diagram of general
mechatronic(electro-mechanical)
design elements
• Usually the output of a transducer is an analog signal
(voltage or current) that is continuous and time
varying. The output of transducers are not in the
desired form as we would like to process them.The
signals may
• Be too small (in the range of millivolts)
• Be too noisy ( due to electromagnetic interference)
• Contain dc offset
• Not be compatible with next stages(like indicating
instruments, display devices, controlling elements, etc)
• Contain a wrong information (due to poor
designing and wrong installation of
transducers)
• The above stated problems can be recovered .
• Most commonly used signal conditioning
process is amplification using amplifier in
which the signal magnitude is increased.
• Other signal conditioning elements are adder,
integrator, subtractor, differentiator and
comparators.
• Actuators are parts of the physical process
being monitored and controlled.
• In any physical process there is motion or
some sort of action.
• This motion or action can be applied to the
mechanical process through actuators.
• They take low power signals and produce high
output signals.
• Stepper motor, solenoids and so on
• Programmable Logic Controllers (PLCs) are
industrial devices used for interfacing and
controlling analog and digital devices.
• The PLCs are programmed with ladder logic,
which is a graphical method of laying out the
connectivity and logic between system inputs
and outputs.
SCOPE OF MECHATRONICS
• Better design of products: Computer aided
designing (CAD) involves the use of computers
to assist in designing of an individual part,
machine tool and product.
• Better Process Planning: It helps to develop
more logical and consistent process plans
which results in lower manufacturing costs
and higher product quality.
• Reliable and Quality Oriented Manufacturing:
Because of computer-integrated
manufacturing (CIM), the reliable and high
quality oriented products can be
manufactured.
• Intelligent Process Control: Due to
developments in digital computer systems,
their use in process control has extensively
increased.
General Parameters For Designing An
Intelligent Mechatronic System
• Analyse product design and development
specifications.
• Select process variables, set points, processes,
etc
• Design proper analog and digital circuits.
• Select mechanical components and devices.
• Design proper mechanical system like
hydraulic, pneumatic, etc
• Select sensors, actuators and control
components.
• Design accurate and precise control system for
various process variables.
• Develop necessary computer software and
database.
• Integrate the above-stated parameters
effectively.
• Monitor the performance of designed system.
Applications Of Mechatronics(ElectroMechanical)
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In automatic washing machines, dish washers.
In CD players, VCRs, camcorders.
In document scanners, MI equipments
In integrated circuits (Ics) manufacturing systems
In robotics used in welding
In fax and photocopier machines.
Laser Printers
Flexible manufacturing systems
In air conditioners, elevator controls
In automobiles
Transducers
• Transducers(sensors) are linked with
instrumentation systems. In most of the
applications and automation systems, it is
desirable to convert the physical quantities or
non-electrical quantities like temperature,
pressure, velocity, liquid level etc
• Transducer is defined as a device which
converts one form of energy into another.
Classification Of Transducers
• On the basis of the method used for
transduction: In this type of classification the
transducers are classified on the basis of
principle of transduction.e.g: resistive,
capacitive, inductive and so forth.
Active and Passive Transducers
• Active transducers are defined as those
transducers which do not require any external or
auxiliary power source to generate the equivalent
output e.g : voltage or current.
• They are self generating transducers for example,
a piezoelectric crystal transducer, being an active
transducer, converts pressure into emf.
• Passive transducers are defines as those hat
require external or auxiliary power.
• They are externally powered transducers for
example a potentiometer.
Analog and Digital Transducers
• An analog transducer converts the input
physical quantity into analog output, which is
a continuous function of time e.g. a
thermocouple.
• A digital transducer converts the input
physical quantity into digital form, in the form
of pulses having logic 0 and logic 1.
Transducers and Inverse Transducers
• A transducer is a device which converts the
physical quantities into electrical signals (by
electrical means).
• An inverse transducer is a device which
converts the electrical quantities (signals) into
non-electrical quantities.
Primary and Secondary Transducers
Selection Parameters of Transducers
• Physical quantity which is to be measured should be
considered first. That is, first consider the input
quantity which is to be applied at the input of the
transducer.
• Determine type and range of the measurand. The
range of the input quantity and the transducer should
be compatible to provide good resolution.
• Linearity: A transducer should provide linear
characteristics between the input(physical parameter)
and the output (resulting electrical signal)
• Stability: Under operating or working conditions, the
transducer should provide high degree of stability.
PERFORMANCE CHARACTERISTICS
• Accuracy – the degree of exactness (closeness) of
measurement compared to the expected (desired) value.
• Resolution – the smallest change in a measurement variable to
which an instrument will respond.
• Precision – a measure of consistency or repeatability of
measurement, i.e successive reading do not differ.
• Sensitivity – ratio of change in the output (response) of
instrument to a change of input or measured variable.
• Expected value – the design value or the most probable value
that expect to obtain.
• Error – the deviation of the true value from the desired value.
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• Ruggedness: A transducer should have the
ability to withstand against shocks and
vibrations. It should also tolerate the
overloading problems.
• Loading Effect: It should be minimum. A
transducer should not produce any loading
effect on the preceding stages.
Resistive Transducers
Translatory (linear) Potentiometer
Rotational Potentiometer
Mathematical Analysis Linear
(Translational) Potentiometer
Inductive Transducers
Q- Calculate the inductance of a coil having 9
turns. The diameter of each turn is 2.5 cm and
the length of the coil is 2cm(the distance
between first and last turn is 2cm).Assume air
core inside the coil.
Linear Variable Differential
Transformer (LVDT)
Applications of LVDT
• It is used as a secondary transducer for the
measurement of force, pressure and liquid.
• Level indicators.
Rotary Variable Differential
Transformer
Comparison of LVDT and RVDT
Capacitive Transducers