Control Systems: Part2 Objective Questions

Control Systems: Part2 Objective Questions

1. The system represented by the input-output relationship y(t)= ^5t∫_-∞ x(τ)dτ, t>0 is

    A. Linear and casual

    B. Linear but not casual

    C. Casual but not linear

    D. Neither linear nor casual

Ans: B

2. For the system 2/(s+1), the approximate time taken for a step response to

 reach 98% of its final value is

    A. 1s

    B. 2s

    C. 4s

    D. 8s

Ans: C

3. Given the finite length input x[n] and the corresponding finite length output y[n] 

of an LTI system as shown below, the impulse response h[n] of the system is         

    A.h[n]={1,0,0,1}

    B.h[n]={1,0,1}

    C.h[n]={1,1,1,1}

    D.h[n]={1,1,1}

Ans:C

4. The frequency response of G(s)=1/[s(s+1)(s+2)] plotted in the complex 

G(jω) plane (for 0< ω<∞) is....Options A, B, C, D are given below

  A.                                                                                                          

                                         

   

Ans:A

5. The system x=Ax+Bu with

 A=

                                         

B=  

   

is


   A. stable and controllable

   B. stable but uncontrollable

   C. unstable but controllable

   D. unstable and uncontrollable

Ans: C

6. The characteristic equation of a closed-loop system is a

(s+1)(s+3)+k(s+2)=0,k>0. Which of the following statements is true?

    A. Its roots are always real

    B. It cannot have a breakaway point in the range -1<Re[s]<0

    C. Two of its roots tend to infinity along the asymptotes Re[s]=-1

    D. It may have complex roots in the right half plane

Ans:C

7. The frequency response of a linear system G(jω) is provided in the tabular form 

below 

|G(jω)|	1.3	1.2	1.0	0.8	0.5	0.3
∠G(jω)	-130°	-140°	-150°	-160°	-180°	-200°

  A. 6dB and 30°

  B.  6dB and -30°

  C. -6dB and 30°

  D. -6dB and -30°

8. An openloop system represented by the transfer function 

G(s) = [(s+1)/(s+2)(s+3)] is

   A. stable and of the minimum phase type

   B. stable and of the non-minimum phase type

   C. unstable and of the minimum phase type

   D. stable and of the non-minimum phase type

Ans:D

9. The open loop transfer function G(s) of a unity feedback control system is given as, 

G(s)=[ k(s+2/3) / s²(s+2) ]  From the root locus, it can be inferred that when k tends 

to positive infinity.

  A.   three roots with nearly equal real parts exist on the left half of the s-plane

  B.   one real root is found on the right half of the s-plane

  C.   the root loci cross the jω axis for a finite value of k; k not equal to 0

  D.   three real roots are found on the right half of the s-plane

Ans:A

10. The response h(t) of a linear time invariant system to an impulse δ(t), under

 initially relaxed condition is h(t) = e^-t+e^-2t. The response of this system for a unit 

step input u(t) is

      A.   u(t)+e^-t+e^-2t

      B.   (e^-t+e^-2t) u(t)

      C.   (1.5-e^-t-0.5e^-2t) u(t)

      D.   e^-tδ(t)+e^-2tu(t)

Ans:C