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 quantities-charge, current and voltage. Electrical systems are integral part of electro-mechanical 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(Electro-Mechanical) 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.

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 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