# Digital Control Engineering 2nd June2012 AP9223

M.E. DEGREE EXAMINATION, JUNE 2012.
Second semester
Applied Electronics
AP9223/248206/AP 923/10244 AE 203—DIGITAL CONTROL ENGINEERING
(Regulation 2009)

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PART A— (10 × 2 = 20 marks)

1. What is the effect of a derivative controller on peak overshoot of a second order undamped system?
2. List the advantages of PID controller.
3. What is alaising?
4. State the effects of adding zeros to a system.
5. List any two properties of z-transform.
6. Define state variable.
7. Draw the basic structure of digital control system.
8. What is peak overshoot?
9. List some applications of digital control system.
10. What is data acquisition?

PART B— (5 × 16 = 80 marks)

11. (a) Discuss with block diagram PI, PD and PID controllers on transient response of a second order system.
Or
(b)(i) Consider the system with G(s) = 10-4 /(s2-1.21) and H(s) = 1. Design a proportional plus derivative controller Gc(s)=kp(I+kds) such that the damping ration is 0.7 and the undamped natural frequency is 0.5 rad/sec for the closed loop system. (12)
(ii) Explain the need for controllers. (4)

12. (a) (i) Describe the operation of zero-order and first-order hold with necessary expression. (8)
(ii) Draw the diagram of sampler and Zero-order hold and drive the transfer function.(8)
Or
(b) (i) Explain the factors limiting the choice of sampling rate. (6)
(ii) Define sampling theorem. Explain the frequency domain considerations in sampling and reconstruction. (10)

13. (a) Obtaining the state variable model for the transfer function using first comparison and second Also draw the state diagram.
G(s) = (s+3)/(s3+9s2+24s+20)
Or
(b)(i) Explain the procedure, necessary conditions and sufficient conditions for Jury’s stability test. (8)
(ii) Determine the pulse transfer function of linear discrete-time system in z-domain.(8)

14. (a) The closed loop transfer function of a unity feedback digital control system is Y(z)/R(z) = (z+0.5)/3(z2-z+0.5); T= 1 sec.
Find the open loop transfer function Gh0G(z). Construct the Bode the Bode diagram for GhoG(w) on w-plane.
Determine gain margin, phase margin, resonant peak and bandwidth of the system.
Or
(b) Write short notes on:
(i) Discrete integrator (8)
(ii) Discrete differentiator. (8)

15. (a) With neat block diagram explain the interfacing of stepping motor drive circuits with microcontroller.
Or
(b)(i) Derive the expression for PID control algorithm. (8)
(ii) Explain the interface for temperature feedback with microprocessor. (8)