WALJAT COLLEGES OF APPLIED SCIENCES In academic partnership with BIRLA INSTITUTE OF TECHNOLOGY Question Bank Course: Biotechnology Session: 005-006 Subject: BT6008 Process Measurement and Control Semester: VI The General Control System 1. What do you understand by a control system? Explain with help of some suitable examples.. Compare open loop and close loop control systems, and quote a few examples (at least five) of practical importance of each group. 3. What are manually-controlled and automatic-controlled control systems? Explain with suitable example. 4. Differentiate between: a. Linear and Non-linear Control System b. Analog and Digital Control System c. Lumped Parameter and Distributed Parameter System Transfer Function 5. Define transfer function and mention its properties. 6. The transfer function of a system is given by G ( s) = s K ( s + 8) ( s + 4)( s + 5)( s + 13s + 4) Determine the poles and zeros and show the pole-zero configurations in s-plane. 7. The impulse response of a system is given by: g ( t) = L 1 (1 cost) Determine the transfer function of the system. 8. A force F when applied to a mass of M result in a displacement of X, obtain the transfer function relating the force applied and the mass displacement. 9. A series circuit consisting of a resistance R and the inductance of L is connected to a d.c. supply of E volts. Determine the transfer function relating the current flowing in the circuit and the input voltage. Prepared by Mohammad Mohtaram 1
10. Show that the transfer function of a thermometer is given by ( ) ( ) = 1 s ( τ s + 1), where Y s X mc τ = ha, the time constant of the system, Y(s), the output response, X(s), the input response, m, the mass of mercury in bulb, C, the heat capacity of mercury, A, the surface area of bulb for heat transfer, h, the film coefficient of heat transfer. 11. Derive the expression for transfer function of two types (armature control and field control) of DC servomotors. Discuss their distinguishing features and applications. 1. Find the transfer functions for the networks shown in Fig. (1), assuming V 1 as input and V as output. C R 1 R R 1 V R 1 V V 1 C R 3 1 V (a) (b) R L C 1 C V V 1 1 C V R V R 1 (d) Fig.(1) (c) 13. Find the expression of voltage transfer ratio for the network shown in Fig.(). C 1 C V in (t) R 1 R V out (t) Fig.() 14. Obtain the transfer function for the mechanical systems shown in Fig.(3). B K M F(t) Fig.(3) x Prepared by Mohammad Mohtaram
15. Obtain the transfer function for the mechanical systems shown in Fig.(4). f x(output) K 1 M 1 M K F(t)(applied force) f 1 (a) f J 1 K 1 J T(applied torque) (b) Fig.(4) θ(output) f 16. Find the expression of voltage transfer ratio for the network shown in Fig.(5). R R V in (t) C C V out (t) Fig.(5) 17. The pole-zero configuration of a transfer function is given below Fig.(6).The value of the transfer function at s = 1 is found to be 10. Determine the transfer function and gain factor K. +jw -4-3 - 0 +σ Fig.(6) -jw Prepared by Mohammad Mohtaram 3
18. Derive the transfer function ( s) ( ) H Q s of a liquid level system shown in Fig.(7). q(t) h(t) R Fig.(7) Liquid level system q 0 (t) 19. Plot poles and zeros in the s-plane of the following function and predict the nature of system response. F ( s) = s ( s +1 )( s + ) 0. What is the difference between interacting and non interacting systems? 1. Show that the overall transfer function of non interacting 1 st order systems is the product of individual transfer functions.. What is the effect of interaction on the transient response of a system? Process Characteristics 3. Discuss the following types of process characteristics a) Process Equation b) Process Load c) Process Lag d) Self-regulation 4. Enumerate the various types of Controls in process industry. 5. Differentiate between discontinuous controller mode and continuous controller mode controls. 6. What do you mean by controller tuning? 7. What do you mean by time constant of a system? What is its significance? 8. What is Distance-Velocity Lag? Prepared by Mohammad Mohtaram 4
Concept of Feedback and Feed forward Control System 9. What are feed back and feed forward control systems? Differentiate between them. 30. What are the main components of a closed loop control system? Explain each in detail. 31. Discuss the effect of feedback on:- i. Stability ii. Gain iii. Bandwidth iv. Noise v. Sensitivity 3. Draw the block diagram for the control system generated when a human being steers an automobile. 33. Draw the block diagram for the control system generated when a human being control the speed of an automobile. 34. Draw the block diagram for the control system when the flow of traffic is controlled a. by a policeman. b. by glowing sequence of lights. Process Measurements 35. What are contact type and radiation type instruments used for temperature measurement? 36. What are resistance thermometers? Describe the construction and working of an RTD. 37. Write short notes on: a. bimetallic thermometers b. quartz crystal thermometers 38. Describe the construction and working of a thermistor. What are the main characteristics of a thermistor? 39. Differentiate between thermocouples and thermopiles. 40. Discuss the instrumentation, advantages and disadvantages of the optical pyrometers. 41. Discuss the working of radiation pyrometers. 4. Describe the construction and working of various elastic elements used for pressure measurement. 43. Describe the construction and working of following electrical pressure transducers. 44. Name three devices used for measurement of temperature electrically. Give their principle of operation, working, merits, and limitations. 45. Explain with neat diagrams the method you would adapt to measure level of a liquid. What are the precautions you would take for accuracy? Prepared by Mohammad Mohtaram 5
46. Describe the following methods of measurement of low pressure (vacuum) with neat sketches. a. Thermocouple Vacuum Gauge b. Ionization Type Vacuum Gauge c. Pirani Gauge 47. Describe the construction and working of the following methods of measurement of temperature. a. Thermistor b. RTD c. Thermocouple d. IC sensors: i. LM 335 IC package ii. LM 34 IC package iii. AD 59 IC package Describe their advantages and limitations. 48. Describe the method of measurement of differential pressure using an inductive transducer. 49. Describe the construction and working of the following methods of measurement of pressure using electrical transducer as secondary transducer. Also mention their merits and demerits. a. Resistive transducer b. Inductive transducer c. Linear Variable Differential transformer (LVDT) d. Photo-electric transducer e. Oscillation transducer f. Potentiometeric Pressure Transducer g. Strain Gauge Transducer h. Variable Reluctance Sensor i. Variable capacitance Transducer j. Force-Balance Pressure Transducer k. Piezoelectric Pressure Transducer l. Vibrating Element Pressure Sensor 50. Draw neat sketch and describe the construction of a capacitive transducer for measurement of liquid level. 51. Enumerate the various methods of measurement of level of liquids. Explain any one of them in detail. Mention their merits and demerits. Prepared by Mohammad Mohtaram 6
5. Describe the construction and working of the following transducers used for the measurement of flow. Also mention their merits and demerits. a. Turbine flow meters b. Electromagnetic flow meter c. Hot wire Anemometer d. Ultrasonic flow meter e. Flow measuring meter using thermistor 53. Write short notes on the following transducers used for the measurement of liquid levels. a. Resistive method b. Inductive methods c. Float method d. Force-Balance Diaphragm system e. Bubbler or Purge system f. Capacitive methods: i.variable area method ii.capacitive Voltage Divider method iii.variable Dielectric Constant Method g. Ultrasonic method h. Nuclear method or Gamma Rays method 54. Define ph value of a solution and describe glass electrode used for measuring ph value of a solution. 55. Describe the methods for viscosity and density measurement in process industry. 56. Describe the methods of power measurement in Electrical circuits. 57. What is rotational speed? Enumerate various electrical methods used for the measurement of rotational speed. Explain any one of them in detail. Mention their merits and demerits. 58. Describe the working and construction of the following transducers used for the measurement of rotational speed. a. DC Tachometer Generator b. AC Tachometer Generator c. Drag Cup Rotor AC Tachogenerator Mention their merits and demerits too. 59. A variable reluctance type Tachometer has 600 teeth. The counter records 3600 counts per second. Determine the speed in rpm. Prepared by Mohammad Mohtaram 7
60. Describe the working and construction of the following digital transducers used for the measurement of rotational speed. a. Photo-electric Tachometer b. Toothed rotor variable reluctance Tachometer Final Control Element 61. What is the role of final control element in controlling a process? 6. Discuss the main characteristics of a control valve. 63. Define three parts of final control operation. 64. Explain how control valve sizing techniques allow selection of the proper size of control valve. 65. Discuss the following types of control valve a. Sliding stem valve b. Rotary valves 66. Discuss the following types of control valve a. Gate valve b. Pinch valve c. Diaphragm valve d. Electronic solenoid operated valve e. Digital valve 67. Discuss the following types of control with suitable diagram in detail a. Two position control b. Multi-position control c. Proportional control d. Proportional plus Integral (PI) control e. Proportional plus Derivative (PD) control f. Proportional Integral Derivative (PID) control 68. Discuss with the help of a suitable diagram: a. Pneumatic controller b. Hydraulic controller Prepared by Mohammad Mohtaram 8
Servomotor Technology in Control 69. Give the basic requirement of a servomotor. Examine the characteristic features of ac and dc servomotors. 70. Find the transfer function of an armature controlled dc motor. 71. Find the transfer function of a field controlled dc motor. 7. Find the transfer function of an ac servo motor. Control System Dynamics 73. What are the various standard forcing functions in control engineering? Explain. 74. What is unit impulse response? Find it for a prototype 1 st order system. 75. Show that the impulse response of a system is equal to Inverse Laplace Transform of its transfer function. 76. What is unit step response? Explain. 77. Find the step response of non interacting 1 st order systems. 78. What do you mean by transient and steady state response? Explain. 79. Discuss the transient responses of the tank when the water present inside is heated. 80. Find the sinusoidal response of 1 st order system in terms of cosine wave and find the phase difference between input and output. 81. A thermometer having a time constant of 1 minute is initially at 50 0 C. It is immersed in a bath at 100 0 C at t = 0. Determine the temperature reading at t = 1. minute. 8. A thermometer requires 1 minute to indicate 98% of the response to a step input. Assuming the thermometer to be a first order system, find the time constant. If the thermometer is placed in a bath, the temperature of which is changing linearly at a rate of 10 0 / min., how much error does the thermometer show? 83. A thermometer having 1 st order dynamics with a time constant of 1 minute is placed in temperature bath at 100 0 F. After thermometer reaches steady state, it is suddenly placed in a bath at 110 0 F at t = 0 and left there for 1 minute, after which it is immediately returned to the bath at 100 0 F. a. Draw a sketch showing the variation of the thermometer reading with time. b. Calculate the thermometer reading at t = 0.5 minute and at t =.0 minute. 84. Repeat problem 81 if the thermometer is in the 110 0 F for only 10 seconds. Prepared by Mohammad Mohtaram 9
85. A process of unknown transfer function is subjected to a unit impulse input. The output of the process is measured accurately and is found to be represented by the function y(t) = t e -t. Determine the unit step response of this process. 86. Consider the unit step response of unity feedback control system whose open loop transfer 1 function isg ( s) =. Obtain the rise time, peak time, maximum overshoot and settling s s + 1 ( ) time. 87. The transfer function of a system is given by G ( s) = s K ( s + 8) ( s + 4)( s + 5)( s + 13s + 4) Determine the poles and zeros and show the pole-zero configurations in s-plane. 88. The impulse response of a system is given by g( t) = l 1 (1 cos t) Determine the transfer function of the system. 89. A force F when applied to a mass of M result in a displacement of X, obtain the transfer function relating the force applied and the mass displacement. 90. A series circuit consisting of a resistance R and the inductance of L is connected to a d.c. supply of E volts. Determine the transfer function relating the current flowing in the circuit and the input voltage. C( s) ωn 91. Consider the closed loop control system given by =. Determine the R( s) s + ξω s + ω value of ξ and ω n so that the system responds to a step input with approximately 5% overshoot and with a settling time of seconds. (Use % criterion). 9. Obtain the unit impulse response and the unit step response of a unity feedback system whose s + 1 open loop transfer function isg( s) =. s 93. Consider the unity feedback control system with the closed loop transfer function: Ks + b G( s) =. Determine the open loop transfer function G(s). Show that the steady ( s + as + b) a K state error in the unit ramp response is given by ess = 1 = K v b 94. A closed-loop control system when subjected to a unit step input has an expression for the time response given by c 3t 1t ( t) = 0.5 + 1.5e 1.75e. Determine the overall transfer function of the system. Prepared by Mohammad Mohtaram 10 n n
95. A unity feed-back control system has its open-loop transfer function given by G (s) = (4s+1) / 4s. Determine an expression for the time response when the system is subjected to (a) Unit impulse input function and (b) Unit step input function. 96. The open loop transfer function of a unity feedback control system is given by : G ( s) = s 3 K + β s ( s + ) + 4s + 1 Determine the value of K and βsuch that the closed loop unit step response has ω n =3 rad/sec and ζ=0.. Y ( s) 97. Consider the system shown in Fig.(7). Show that the transfer function has a zero in the X ( s) right half s-plane. Then obtain y(t) when x(t) is unit step. Plot y(t) versus t. X(s) 6 s + + Y(s) 4 s + 1 Fig.(7) - Test for Unstable System 98. Consider the unity feedback control system with the following open loop transfer function: 10 G ( s) =. Is this system stable? s( s 1)( s + 3) 99. A unity negative feedback control system has an open loop transfer function consisting of two poles, two zeros and a variable gain K. The zeros are located at - and -1; and the poles at 0.1 and 1. Using Routh criterion, determine the range of values of K for which the closed loop system has 0, 1 or poles in the right half of s-plane. 100. Check whether the following polynomial is Hurwitz or not 5 4 3 P ( s) = s + 3s + 3s + 4s + s + 1 101. Find the limits of k so that the polynomial 3 P ( s) = s + 14s + 56s + k, may be Hurwitz. 10. Check whether the 4 th order system described by the following characteristic equation is stable or not s 4 + 8s 3 + 18s + 16s + 5 = 0 Prepared by Mohammad Mohtaram 11
103. By means of Routh criterion, determine the stability of the systems represented by the following characteristic equations. For systems found to be unstable, determine the number of roots of the characteristic equation in the right half s-plane. a) s 4 + s 3 + 8s + 4s + 3 = 0 b) s 4 + 8s 3 + s + 4s + = 0 c) s 5 + s 4 + 3s 3 + 9s + 16s + 10 = 0 d) s 6 + 3s 5 + 5s 4 + 9s 3 + 8s + 6s + 4 = 0 Advanced Control System 104. Explain with the help of some basic examples the multi variable control problems. 105. Discuss with the help of block diagram: a. cascade control b. ratio control 106. What is an Adaptive Controller? Discussed a generalized mechanism for an Adaptive Controller with the help of a block diagram. 107. Give a scheme of feed forward control. 108. Discuss with the help of block diagram: a. model reference adaptive control b. model identification adaptive control 109. Explain override control with the help of an example. Application of Computer 110. Explain how computer supervisory process-control operations are used in an analog processcontrol loop. 111. What is the difference between computer supervisory control and direct digital control? 11. What are programmable logic controllers? How it is helpful in process industry? 113. Give a brief idea of predictive control. 114. With the help of a suitable block diagram explain Predictive Control. 115. Give a brief introduction of Model Predictive Control. 116. What are the advantages and disadvantages of Model Predictive Control? 117. With the help of a suitable block diagram explain Fuzzy Logic Controller. Prepared by Mohammad Mohtaram 1
Control of Heat Exchanger, Distillation Column, Bioreactor 118. Find the transfer function of a heat exchanger. 119. Write short notes on the following: a) distillation column control b) bioreactor control Prepared by Mohammad Mohtaram 13