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Control System

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Control System

shape Introduction

What is a Control System? A Control System primarily manages, commands, directs, or regulates the behavior of other devices or systems using control loops and provides desired response. A control system can range from a home heating controller to large Industrial control systems which are used for controlling processes or machines. A control system is a flow, which provides the desired response by controlling the output.

shape Quiz

Q1. ______ has some roots with real parts equal to zero but none with positive real parts.
    A. Marginally stable B. Absolutely stable C. Absolutely unstable D. Stable Answer: A

Q2. In a hybrid feedback control system carrier signals are
    A. d.c. only B. a.c. only C. both d.c. and a.c. D. none of these Answer: A

Q3. In a system non-linearity may be introduced due to
    A. backlash in gears B. end positions in detectors C. saturation effects in amplifiers D. any of the above Answer: D

Q4. A system has the transfer function [latex]\frac {(1-s)}{(1+s)}[/latex]. It is known as a
    A. 1 B. –0 C. –1 D. None of these Answer: A

Q5. Tow blocks having respective functions as [latex]G_{1}[/latex] and [latex]G_{2}[/latex]are connected in series cascade. Their resultant will be
    A. [latex]{G}_{1}[/latex], [latex]{G}_{2}[/latex] B. [latex]{G}_{1}[/latex], [latex]{G}_{2}[/latex] C. [latex]\frac { {G}_{1} }{ {G}_{2} }[/latex] D. [latex]\frac { {G}_{2} }{ {G}_{1} }[/latex] Answer: A

Q6. The Laplace Transform of unit step function and ramp functions respectively are
    A. [latex]\frac {1}{{s}^{2}} ,\frac {1}{s}[/latex] B. [latex]\frac {1}{s} ,\frac {1}{{s}^{2}} [/latex] C. [latex]\frac {1}{s} ,\frac {1}{{s}^{3}} [/latex] D. [latex]\frac {1}{s}^{3} ,\frac {1}{s} [/latex] Answer:

Q7. If a conventional servomotor is used for servo
    A. the applied voltages are always to be balanced B. the rotor resistance is low C. the rotor resistance is high D. the rotor's diameter is large Answer: B

Q8. Which one of the following statements regarding state space method is NOT TRUE?
    A. It gives compact and convenient form. B. It reduces complexity. C. Direct programming is possible on analog computer. D. None of these Answer: B

Q9. In pneumatic systems, electrical resistance is analogous to a
    A. restriction to flow B. volume of air C. filled helical tube D. none of these Answer: A

Q10. The transfer function of a system is used to determine
    A. the output for a given input B. the type of system C. the input for given output D. the steady state gain Answer: A
Q11. Human system can be considered as a
    A. open-loop system B. closed-loop system with single feedback C. closed-loop system with single feedback D. none of these Answer: C

Q12. The transfer function technique is considered inadequate with systems having
    A. stability problems B. multiple input disturbances C. complexities and non-linearities D. all of the above Answer: D

Q13. The function u (t – [latex]t^{0}[/latex]) = 1 t>t0, 0 1<t0 defines
    A. unit step function B. unit ramp function C. unit impulse function D. none of these Answer: A

Q14. Damping due to back emf is observed in
    A. armature controlled d.c. motor B. field controlled d.c. motor C. a.c. servomotor D. none of these Answer: A

Q15. A system has the transfer function [latex]\frac {(1–s)}{(1+s)}[/latex]. What is its gain at 1 rad/sec?
    A. low-pass system B. high-pass system C. all-pass system D. none of these Answer: B

Q16. Given that D = rotor diameter and L = axial length, a high performance ac servo-motor is characterized by
    A. large D, large L B. large D, small L C. small D, large L D. small D, large L Answer: D

Q17. For the minimum phase system to be stable
    A. phase margin should be negative and gain margin positive B. phase margin should be positive and gain margin negative C. both gain margin and phase margin should be positive D. both gain margin and phase margin should be negative Answer:

Q18. Proportional band of a controller is defined as the range of
    A. measured variables from set value B. measured variables through which the air output changes from maximum to minimum C. air output as measured variable varies from maximum to minimum D. none of these Answer: C

Q19. The sensitivity of a closed loop control system to variations in gain and load disturbance depends upon
    A. loop gain B. frequency C. forward gain D. all of these Answer: B

Q20. An AC servomotor (2-phase induction motor) has a rotor with
    A. high resistance winding B. very small diameter to reduce inertia C. very small axial length to reduce inertia D. both (a) and (b) Answer: D
Q21. 5 percent-proportional band means control output
    A. change by 5 percent B. change from maximum to minimum for 5 percent change in measured variable C. changes by 95 percent D. none of these Answer: B

Q22. Laplace Transform of the functions [latex]{e}^{-1}[/latex] and [latex]{e}^{-2t}[/latex]are
    A. [latex]\frac {1}{S-1}[/latex] + [latex]\frac {1}{(S+2}[/latex] B. [latex]\frac {1}{S+1}[/latex] + [latex]\frac {1}{(S-2}[/latex] C. [latex]\frac {1}{S-1}[/latex] + [latex]\frac {1}{(S-2}[/latex] D. None of these Answer: A

Q23. In pneumatic systems, electrical capacitance is analogous to
    A. restriction to flow B. volume of air C. filled helical tube D. none of these Answer: B

Q24. Backlash in a stable control system can cause
    A. overdamping B. low-level oscillations C. underdamping D. poor stability at reduced values of open-loop gain Answer: B

Q25. In force-current analogy, displacement is analogous to
    A. magnetic flux linkage B. capacitance C. voltage D. inductance Answer: A

Q26. A transfer function of con trol system does not have pole-zero cancellation. Which one of the following statements is true?
    A. System is neither controllable nor observable B. System is completely controllable & observable C. System is observable but uncontrollable D. System is controllable but unobservable Answer: B

Q27. The transfer function Y(s)/U(s) of a system described by the state equations dx/dt=-2x+2u and y(t) = 0.5x is:
    A. [latex]\frac {0.5}{S-2}[/latex] B. [latex]\frac {1}{(S-2}[/latex] C. [latex]\frac {0.5}{S+2}[/latex] D. [latex]\frac {1}{(S-2}[/latex] Answer: D

Q28. In closed loop control system in which positive value of feedback then gain the overall gain of the system will
    A. Decrease B. Increase C. be unaffected D. None of these Answer: A

Q29. The analysis of multiple input multiple output is con veniently studied by
    A. State space analysis B. Root locus approach C. Characteristic equation approach D. Nicholas chart. Answer: A

Q30. The output of a feedback control system must be a function of
    A. Reference and output B. Reference and input C. Input and feedback signal D. Output and feedback signal Answer: A
Q31. Zero initial condition for a system means?
    A. Input reference signal is zero B. Zero stored energy C. Initial movement of moving parts D. System is at rest and no energy is stored in any of its components. Answer: D

Q32. Transfer function of a system is used to calculate which of the following?
    A. The order of the system B. The time constant C. The output for any given input D. The steady state gain. Answer: C

Q33. The transient response, with feedback system
    A. Rises slowly B. Rises quickly C. Decays slowly D. Decays quickly Answer: D

Q34. Which of the following statements is correct for any closed loop system?
    A. All the co-efficient can have zero value B. All the co-efficient are always non-zero C. Only one of the static error co-efficient has a finite non-zero value D. Only two of the static error co-efficient has a finite non-zero value. Answer: C

Q35. Which among the following is not an advantage of an open loop system?
    A. Simplicity in construction & design B. Easy maintenance C. rare problems of stability D. Requirement of system recalibration from time to time Answer: D

Q36. How is an output represented in the control systems?
    A. r(t) B. c(t) C. x(t) D. y(t) Answer: B

Q37. The output signal is fed back at the input side from the______ point
    A. Summing B. Differential C. Take-off D. All of the above Answer: C

Q38. In a signal flow graph, nodes are represented by small _____
    A. Circles B. Squares C. Arrows D. Pointers Answer: A

Q39. In second order system, which among the following remains independent of gain (k)?
    A. Open loop poles B. closed loop poles C. Both a and b D. None of the above Answer: A

Q40. In a parallel combination, the direction of flow of signals through blocks in parallel must resemble to the main_______
    A. Forward B. Feedback C. Opposite D. Diagonal Answer: A
Q41. Where are the dummy nodes added in the branch with unity gain?
    A. At input & output nodes B. Between chain nodes C. Both a & b D. None of the above Answer: A

Q42. Which among the following are solely responsible in determining the speed of response of control system?
    A. Poles B. Zeros C. Speed of input D. All of the above Answer: A

Q43. State space analysis is applicable even if the initial conditions are _____
    A. Zero B. Non-zero C. Equal D. Not equal Answer: B

Q44. What is the value of steady state error in closed loop control systems?
    A. Zero B. Unity C. Infinity D. Unpredictable Answer: A

Q45. Laplace transform of an impulse response is regarded as _____ function of the system
    A. Analytic B. Parabolic C. Transfer D. Hypothetical Answer: C

Q46. For the elimination of feedback loops, the derivation based on transfer function of ______ loop is use(d)
    A. Open B. Closed C. Both a & b D. None of the above Answer: B

Q47. In block diagram representation, what do the lines connecting the blocks, known as?
    A. Branches B. Nodes C. Datums D. Sources Answer: A

Q48. For which systems are the signal flow graphs applicable?
    A. Causal B. Invertible C. linear time invariant system D. Dynamic Answer: C

Q49. Type 0 systems are unsuitable ______
    A. For ramp inputs B. If input is parabolic in nature. C. Both a & b D. None of the above Answer: C

Q50. A good control system should be sensitive to ______
    A. Internal disturbances B. Environmental parameters C. Parametric variations D. Input signals (except noise) Answer: D
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