This set of Control Systems Multiple Choice Questions & Answers (MCQs) focuses on “Compensation Techniques”.

1. The open loop control transfer function of a unity feedback system is given by :

G(s) =K/(s+2)(s+4)(s^2+6s+25)

Which is the value of K which causes sustained oscillations in the closed loop system?

a) 590

b) 790

c) 990

d) 1190

2. The characteristic equation of the control system is s^{5}+15s^{4}+85s^{3}+225s^{2}+274s+120=0 . What are the number of roots of the equation which lie to the left of the line s+1 = 0?

a) 2

b) 3

c) 4

d) 5

3. Assertion (A): The closed loop stability can be determined from the poles of an open loop system and the polar plot of the frequency response.

Reason (R): Unstable system has right half poles.

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true and R is not correct Explanation of A

c) A is True and R is false

d) A is False and R is true

4. The characteristic equation of a system is 2s^{5}+s^{4}+4s^{3}+2s^{2}+2s+1=0 . Which one of the following is correct?

a) Stable

b) Marginally stable

c) Unstable

d) Oscillatory

5. Which of the following may result in instability problem?

a) Large error

b) High selectivity

c) High gain

d) Noise

6. How many roots with positive real parts do the equation s^{3}+s^{2}-s+1=0 have?

a) 0

b) 1

c) 2

d) 3

7. The characteristic equation of a control system is given by s^{5}+s^{4}+2s^{3}+2s^{2}+4s+6=0. The number of the roots of the equation which lie on the right half of s-plane:

a) 0

b) 1

c) 2

d) 3

8. For what values of K does the polynomial s^{4}+8s^{3}+24s^{2}+32s+K=0 have roots with zero real parts?

a) 10

b) 20

c) 40

d) 80

9. Phase margin is always positive for stable feedback system?

a) True

b) False

10. In closed loop control system, what is the sensitivity of the gain of the overall system, M to the variation in G?

a) 1/1+GH

b) 1/1+G

c) G/1GH

d) G/1+G