Basics of Control System

Multiple choice questions:

1. A control system in which control action is somehow dependent on output is known as

1. open loop system.

2. closed loop system.

3. semiclosed loop system.

4. none of these.

2. Which of the following increases with the feedback?

1. System stability.

2. Sensitivity.

3. Gain.

4. Effects of disturbing signal.

3. In case of an open loop control system which of following statement is true?

1. Output is dependent of control input.

2. Output is independent of control input.

3. Only system parameters have effect on control output.

4. None of these.

4. Which of the following is an open loop control system?

1. Ward Leonard control.

2. Field controlled dc motor.

3. Metadyne.

4. Stroboscope.

5. Mass in force-voltage analogy is analogous to

1. inductance.

2. charge.

3. current.

4. resistance.

6. Phase margin is used to specify which of the following ?

1. Frequency response.

2. Absolute stability.

3. Relative stability.

4. Time response.

7. Routh Herwitz criterion provides

1. roots in right half of s plane.

2. roots in left half of s plane.

3. roots in right half of s plane and roots on imaginary axis.

4. roots in left half of s plane and roots on imaginary axis.

8. _______________________________ has the tendency to oscillate.

1. Closed loop system.

2. Open loop system.

3. Both A and B.

4. Semiclosed loop system.

9. Steady state stability limit is

1. equal to transient stability limit.

2. greater than transient stability limit.

3. lesser than transient stability limit.

4. none of these.

10. The steady-state stability limit of a synchronous generator can be increased by

1. an increase in the excitation of the M/C.

2. an increase in its reactance.

3. a decrease in the moment of inertia of the machine.

4. an increase in the moment of inertia of the machine.

11. Transfer function of a zero-order-hold system is

1. ( 1 / s )( 1 + e-st ).

2. ( 1 / s )( 1 - e-st ).

3. 1 – ( 1 /s )e-st.

4. 1 + ( 1 / s )e-st.

12. A system is denoted as dy / dt + 2y = 4tu ( t ), the ramp component in the forced response

will

1. tu ( t ).

2. 2tu ( t ).

3. 3tu ( t ).

4. 4tu ( t ).

13. The steady state error of a stable type 0 unity feedback system, for a unit step function is

1. 0.

2. 1 / ( 1 + Kp ).

3. infinity.

4. 1 / Kp.

14. The no. of roots of s3 + 5s2 + 7s + 3 = 0, in the right half of the s-plane is

1. 0.

2. 1.

3. 2.

4. 3.

15. Sinusoidal oscillators are

1. stable.

2. unstable.

3. marginally stable.

4. conditionally stable.

16. Consider the following statements regarding time domain analysis of a control system 1. Integral control can convert a second order system into a third order system. 2. Derivative control improves system's transient performance. 3. Integral control does not improve system's steady state performance

1. 1 and 2 are correct.

2. 1 and 3 are correct.

3. 2 and 3 are correct.

4. 1, 2 and 3 are correct.

17. If the gain of the open loop system is doubled, the gain margin

1. is not affected.

2. gets doubled.

3. becomes half.

4. becomes one-fourth.

18. Phase margin of a system is used to specify

1. absolute stability.

2. relative stability.

3. time response.

4. none of these.

19. A linear discrete-time system has the following characteristic equation, z3 – 0.81 z = 0, so

The system is

1. marginally stable.

2. stable.

3. unstable.

4. none of these.

20. For making an unstable system stable

1. gain of the system should be decreased.

2. gain of the system should be increased.

3. no. of zero to the loop transfer functions should be decreased.

4. no. of zero to the loop transfer functions should be increased.