Page 1 :
Process Dynamics and Control, Subject Code:7CH03, Department of Chemical Engineering, Anuradha Engineering College, , Chikhli, Wednesday, August 19, 2015, 1, Prepared by M.A.Quazi
Page 2 :
Lecture 4, Contents:, Controllers, Advantage and disadvantage of Pneumatic and Electronic Controllers, Controller Actions, Electronic Circuit Implementation, Electronic Controller Actions, Proportional controller or P controller, Proportional Derivative controller or PD controller, Proportional Integral controller or PI controller, Proportional Integral Derivative controller or PID controller, Wednesday, August 19, 2015, 2, Prepared by M.A.Quazi
Page 3 :
Objectives, To understand the Mechanism of P and PD controllers ., Wednesday, August 19, 2015, 3, Prepared by M.A.Quazi
Page 4 :
Review
Page 5 :
Components of Block Diagram:, , Process, Measuring Element, Comparator, Controller, Final control element
Page 6 :
Controllers, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 6, The function of controller is to receive the actuating signal (error ‘e’) and minimize it giving a output signal (P) to final control element. , Depending on the output signal to final control element (Control Valve) from controller, Controllers are classified in mainly two way,, Pneumatic Controller in which output signal to Final Control Element (Control Valve) is given in form of air pressure , Electronic Controller in which output signal to Final Control Element (Control Valve) is given in form of Electronic signals (Analog or Digital)
Page 7 :
Advantage and disadvantage of Pneumatic and Electronic Controllers, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 7, Transmission Lag: Pneumatic Controller has response time in order of minutes where as in Electronic Controllers it is negligible., Safety: In Electronic Controller there is danger of short circuit during operation and hence cause risk of fire so can not be used in industries like Petro-Chemical., Ambient Temperature: At low temperature pneumatic lines can get clogged were as Electronic controller are better in such cases., Compatibility: Measuring element produces electrical output so Electronic Controller has advantage of compatibility with electrical sensing devices where as pneumatic controller needs a converter.
Page 8 :
Advantage and disadvantage of Pneumatic and Electronic Controllers. (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 8, Maintenance: Pneumatic controller Electronic controller are rugged and free of maintenance where as Electronic controller require greater maintenance., Cost and Size: Electronic controller are less costly and compact compare to pneumatic controller., Reliability: Electronic Controller are more reliable than pneumatic controllers., Calibration: Electronic controllers are not required to be calibrated as often as the pneumatic controllers.
Page 9 :
Controller Actions, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 9, The basic control actions which are used by controller (realized through electronic or pneumatic means) are shown below., Controller (Pneumatic or Electronics), Proportional (P), Proportional-derivative, (PD), Proportional-integral, (PI), Proportional-Integral-derivative, (PID)
Page 11 :
Electronic Circuit Implementation (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 11, e, C, eo, R, Differentiator, K, e, eo, KC, Multiplier
Page 12 :
Electronic Controller Actions, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 12, Proportional Controller: , The relationship between input to proportional controller and its output is given by,, , That is,, , Where, KC is called as Controller gain. Taking Laplace transform and rearranging, we get.
Page 13 :
Electronic Proportional Controller (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 13, The error is to be multiplied by KC to produce output. The value of KC can be change by using circuit as shown below., KC, R, -B, C
Page 14 :
Electronic Proportional derivative Controller, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 14, The output of a proportional derivative controller is proportional not only to error but also to time derivative of error. That is,, and, , That is,, , Taking Laplace transforms and rearranging we get,
Page 15 :
Electronic Proportional derivative Controller (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 15, The error signal is generated using the comparator circuit. The signal is fed to a Pot set KC. The signal is split. One part is fed to the summer while the other is fed to differentiator followed by Pot (This Pot controls τD), and then fed to summer to generate P. The circuit is shown below., KC, τD, R, -B, P
Page 16 :
Electronic Proportional Integral Controller, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 16, The output of a proportional integral controller is proportional not only to error but also to time integral of error. That is,, and, , That is,, , Taking Laplace transforms and rearranging we get,
Page 17 :
Electronic Proportional Integral Controller (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 17, The error signal is generated using the comparator circuit. The signal is fed to a Pot set KC. The signal is split. One part is fed to the summer while the other is fed to Integrator followed by Pot (This Pot controls1/τI), and then fed to summer to generate P. The circuit is shown below., KC, R, -B, P, 1/τI
Page 18 :
Electronic Proportional Integral Derivative Controller, Wednesday, August 19, 2015, Prepared by M.A.Quazi, 18, The output of a proportional integral derivative controller is proportional not only to error but also to time integral of error and also to time derivative of the error. That is,, , and, , That is,, , Taking Laplace transforms and rearranging we get,
Page 19 :
Electronic Proportional Integral Derivative Controller (Part 2), Wednesday, August 19, 2015, Prepared by M.A.Quazi, 19, To generate this action there is need of integrator and differentiator. The error signal is generated using comparator. A Pot is used to generate Kc. The Pot in the integrator steam provides τI and while that in differentiator stream provides τD. This shown below., KC, τD, R, -B, P, 1, τI
Page 20 :
Wednesday, August 19, 2015, Prepared by M.A.Quazi, 20, Discussion
