CONTROL SYSTEM QUESTION FOR EEE&EE for PRATICE BY C KARAN SIR (PROF. GEC )

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      CONTROL SYSTEM     

EEE&EE CONTROL SYSTEM QUESTION FOR PRATICE BY C KARAN SIR (PROF. GEC )

 MCQ ON CONTROL SYSTEMS

1.In an open loop control system
(a)Output is independent of control input                 (b) Output is dependent on control input
(c) Only system parameters have effect on the control output     (d) None of the above
Ans: a
2.For open control system which of the following statements is incorrect ?
(a)Less expensive
(b) Recalibration is not required for maintaining the required quality of the output
(c) Construction is simple and maintenance easy
(dErrors are caused by disturbances
Ans: b
3. A control system in which the control action is somehow dependent on the output is known as
(a)Closed loop system
(b)Semiclosed loop system
(c) Open system
(d)None of the above
Ans: a
4.In closed loop control system, with positive value of feedback gain the overall gain of the system will
(a)decrease
(b)increase
(c)be unaffected
(d)any of the above
Ans: a
5.Which of the following is an open loop control system ?
(a)Field controlled D.C. motor
(b) Ward leonard control
(c)Metadyne
(d)Stroboscope
Ans: a
6. Which of the following statements is not necessarily correct for open control system ?
(a)Input command is the sole factor responsible for providing the control action
(b)Presence of non-linearities causes malfunctioning
(c)Less expensive
(d) Generally free from problems of non-linearities
Ans: b
7.In open loop system
(a) the control action depends on the size of the system
(b) the control action depends on system variables
(c)the control action depends on the input signal
(d)the control action is independent of the output
Ans: d
8 .has tendency to oscillate.
(a) Open loop system
(b)Closed loop system
(c)Both (a) and (b)
(d)Neither (a) nor (b)
Ans: b
9.A good control system has all the following features except
(a) good stability
(b) slow response
(c)good accuracy
(d)sufficient power handling capacity
Ans: b
10. A car is rtyining at a constant speed of 50 km/h, which of the following is the feedback element for the driver ?
(a) Clutch
(b) Eyes
(c)Needle of the speedometer
(d) Steering wheel
(e)None of the above
Ans: c

11)Which among the following represents an illustration of closed loop system?

a. Automatic washing machine
b. Automatic electric iron
c. Bread toaster
d. Electric hand drier

12)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

13)Which terminology deals with the excitation or stimulus applied to the system from an external source for the generation of an output?

a. Input signal
b. Output signal
c. Error signal
d. Feedback signal

14)Which among the following is a unique model of a system?

a. Transfer function

b. State variable

c. Both a and b

d. None of the above

st15)What should be the nature of bandwidth for a good control syem?

a. Large
b. Small
c. Medium
d. All of the above

16)Which among the following controls the speed of D.C. motor?

a. Galvanometer
b. Gauss meter
c. Potentiometer
d. Tachometer

17)Which system exhibits the initiation of corrective action only after the output gets affected?

a. Feed forward
b. Feedback
c. Both a and b
d. None of the above

18)A good control system should be sensitive to __________

a. Internal disturbances
b. Environmental parameters
c. Parametric variations
d. Input signals (except noise)

19)What is the value of steady state error in closed loop control systems?

a. Zero
b. Unity
c. Infinity
d. Unpredictable

20.Into which energy signal does the position sensor convert the measured position of servomotor in servomechanisms?

a. Mechanical
b. Electrical
c. Thermal
d. Light

21)Which among the following represents an illustration of closed loop system?

a. Automatic washing machine
b. Automatic electric iron
c. Bread toaster
d. Electric hand drier

Ans b

22)Which notation represents the feedback path in closed loop system representation?

a. b(t)
b. c(t)
c. e(t)
d. r(t)

23)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

24)Which terminology deals with the excitation or stimulus applied to the system from an external source for the generation of an output?

a. Input signal
b. Output signal
c. Error signal
d. Feedback signal

ANS FROM 11-31 MCQ
11-b
12-d
13-a
14-a
15-a
16-c
17-b
18-d
19-a
20-b
21-b
22-a
23-d
24-a
25-a
26-c
27-b
28-c
29-b
30-a

31-b

                                                                            TWO MARKS

1.What is meant by a system?

    It is an arrangement of physical components related in such a manner as to form an entire unit.

2.What is a command input?

    It is the excitation applied to a control system from an external source. It is also a motivating

input signal to the system, which is independent of the output of the system.

3. Define output.

    It is the actual response obtained from a control system, which must be maintained at a

prescribed value.

4.What is an actuating signal?

    It is the difference between the reference input and feedback signal. It is also called a actuating

signal.

5. Define plant.

   It is the process/body/ machine, of which a particular quantity or condition is to be controlled.

6. List the two types of control systems?

   The two types of control system are, open loop systems and closed loop system.

7.What is an open loop system?

   The control system in which the output has no effect upon the input quantity, is known as open

loop control system.

8.What is meant by a controller?

   It is the component required to generate the appropriate control signal applied to the plant.

9. Define manually controlled systems?

    Systems that involve continuous manual control by a human operator are called manually

controlled system.

10.For what purpose feedback element is used?

     It is the component required to generate the appropriate control signal applied to the plant.

12. What is feedback?

     The feedback is a control action, in which the output is sampled and a proportional signal is

given to input for automatic correction of any changes in desired output.

13. Give the types of feedback?

     Negative feedback  Positive feedback.

14. When will feedback exist in a system?

     Feedback is said to exist in a system, when a closed sequence, of cause and effect relations exist between system available.

15.Define transfer function

     Transfer function of a given system is defined as the ratio of the laplace transform of output

variable to laplace transform of input variables at zero input conditions.

16.Define order of the system.

    The highest power of the complex variables in the denominator of the transfer function

determines the order of the system.

17.Define linear system.

     A system is said to be linear if it obeys the principle of superposition and homogeneity. The

principle of superposition states that the responseof the system to a weighted sum of the

responses of the system to each individual input signals.

18.Give the important characteristics of open loop control system.

     Their ability to perform accurately is determined by their calibration, which implies to establish

the input-output relation to obtain a desired system accuracy.

19.When will the system is said to be linear?

     The system is said to be linear, if it satisfies the following two properties: •

Adaptive property that is for any x and y belonging to the domain of the function f,

we have F(x+y) = f(x) +f(y) •

Homogeneous property that is for any x belonging to the domain of the function f and for any scalar constant

We have F(x) =af(x)

These two properties together constitute a principle of superposition

20. Define differential equations.

     The basic models of dynamic physical systems are differential equations.

21. List the steps involved in obtaining the transfer function.

     To write the differential equations governing the system.

     To laplace transform the equations i.e. to replace the terms involving d/dt by s, and integral of dt by 1/s.

     To obtain the ratio of transformed output to the input variables.

22. Give the properties of transfer functions.

    The properties of transfer function are as follows:

The transfer function of a system is the laplace transform of its impulse response. i.e. if

the input to a system with transfer function P(s) is an impulse and all initial conditions are

zero, the transform of the output is P(s).

The roots of the denominator are the system poles and the roots of the numerator are

system zeros. The system stability can be described in terms of the location of the roots

of the transfer function.

23. Give the advantages of transfer function.

     It helps in the stability analysis of the system.

     It helps in determining the important information about the system Poles, zeros,

characteristic equation etc. •Once transfer function is known, output response for any type of reference input can be calculated.

The system differential equation can be easily obtained by replacing variable ‘s’ by d/dt.

24. Give the disadvantages of transfer function.

      The disadvantages of transfer function approach are:

      •Only applicable to linear time invariant systems.

      •It does not provide any information concerning the physical structure of the system. From

 transfer function, physical nature of the system, whether it is electrical, mechanical, thermal or hydraulic cannot be judged.

      •Effects arising due to initial conditions are totally neglected. Hence initial conditions loose importance.

25. What is the other name for closed loop control system?

     The other name for closed loop control system is feedback control system.

26. Give the important features of feedback.

      •Reduced effects of non-linearities and distortion.

      •Increased accuracy.

      •Reduced sensitivity of the ratio of the output to input to variations in system

characteristics.

     •Tendency toward oscillation or instability.

27. What are the basic elements used for modeling mechanical translational system?

     The model of mechanical translational system can be obtained by using three basic elements

mass spring and dashpot.

28. What is translational system?

     Consider a mechanical system in which motion is taking place along a straight line. Such systems are of translational type. These systems are characterized by displacement, linear velocity and linear acceleration.

29. Define torque.

     This is the motion about a fixed axis. In such systems, the force gets replaced by a moment about the fixed axis. I.e. {force x distance from fixed axis} which is called torque.

30. Define friction.

    Whenever there is a motion, there exists a friction. Friction may be between moving element and fixed support or between two moving surfaces. Friction is also non-linear in nature.

31. Name the two types of electrical analogous for mechanical system.

   The two types of analogies for mechanical system are force-voltage analogy and force-current

analogy.

32. What are analogous systems?

     Systems whose differential equations are identical form are called analogous systems.

32. Give two types of variables in physical system.

    The two variables in physical systems are through variables and across variable. Through variables refer to a point, the across variable is measured between two points.

34. Give the other names for force voltage analogy, force current analogy.

    The other names for force voltage analogy and force

current analogy are Force voltage analogy- Loop analysis. Force current analogy- nodal analysis.

35. What is block diagram?

     A block diagram of a system is a pictorial representation of the functions performed by each

component of the system and shows the flow of signa ls.

36. What are the basic components of block diagram?

     The basic components of block diagram are block, branch point, summing point, arrows.

     The connection between the blocks is shown by lines called branches.

     The signal can travel along the direction of arrow only.

37. What is the need for block diagram reduction?

    Block diagrams of some of the control systems turn out to be complex. Such that the evaluation of their performance requires simplification(or red

uction) of block diagrams which is carried out by block diagram rearrangements.

38. List the advantages of block diagram.

    •Individual as well as overall performance of the system can be studied by using transfer functions shown in the block diagram.  Overall closed loop transfer function can be easily calculated by using block diagram rules.

    •The function of individual elements can be visualized from the block diagram.

     •Very simple to construct the block diagram for complicated systems.

39. List the disadvantages of block diagram.

    •Source of energy is generally not shown in the block diagram. So block diagram for given system is not unique.

    •Block diagram does not include any information about physical construction of the system.

    •Block diagram reduction technique is time consuming process for complicated systems(higher order systems).

40. List the steps to reduce the block diagram.

     •Reduce the series blocks.

     •Reduce the parallel blocks.

     •Reduce minor feedback loops.

     •As for as possible shift summing point to the left and take-off point to the right.

     •Repeat the above steps till canonical form is obtained.

41. What is signal flow graph?

     The graphical representation of the variables of a set of linear algebraic equations representing

the system is called signal flow graph.

42. Give the properties of signal flow graph?

     •The signal in the system flows along the branches and along the arrows associated with the branches.

     •The value of variable represented by any node is an algebraic sum of all the signals entering at the node.

     •The signals gets multiplied by the branch gain or branch transmittance when it travels along it.

    •Applicable only to linear time invariant systems.

43. What are the standard test signals employed for time domain studies?

     The standard test signals employed for time domain studies are 1. step signal, ramp signal,

parabolic signal, impulse signal.

44.What do you mean by a node in signal flow graph?

     It represents a system variable, which is equal to the sum of all incoming signals at the node,

outgoing signals from the node do not affect the value of the node variable.

                                                                LONG QUESTIONS

(1)  Derive the expressions and draw the response of first order system for unit step input.

(2)  Draw the response of second order system for critically damped case and when input is unit

step.

(3)  Measurements conducted on a Servomechanism show the system response to be c(t)=1+0.2e 60t -1.2 e -10t , when subjected to a unit step. Obtain an expression for closed loop transfer function.

(4)  Compare and Contrast Open loop and Closed loop Control Systems.

(5)  Explain the terminologies associated with Signal Flow Graphs with a suitable example