Anna University Coimbatore 2008 B.E Electrical and Electronics Engineering Control system unit 1 - Question Paper
Wednesday, 16 January 2013 02:20Web
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PI controller
PD controller
PID controller
71.What is proportional controller?
It is device that produces a control signal which is proportional to the input fault signal.
72.What is PI controller?
It is device that produces a control signal consisting of 2 terms –one proportional to fault signal and the other proportional to the integral of fault signal.
72. What is PD controller
PD controller is a proportional plus derivative controller which produces
an output signal consisting of 2 time -one proportional to fault singal
and other proportional to the derivative of the signal.
73 What is the significance of integral controller and derivative
controller in aPID controller.
The proportional controller stabilizes the gain but produces a steady state fault. The integral control decreases or eliminates the steady state fault.
74.Why derivative controller is not used in control systems.
The derivative controller produces a control action based on the rate of change of fault signal and it does not produce corrective measures for any constant fault.
75.Define Steady state fault.
The steady state fault is described as the value of fault as time tends to infinity.
76.What is the drawback of static coefficients.
The main draw back of static coefficient is that it does not show the variation of fault with time and input should be standard input.
77. What is step signal.
The step signal is a signal whose value modifications from zero to A at t= 0 and remains constant at A for t>0.
78. What is ramp signal
The ramp signal is a signal whose value increases linearly with time from an initial value of zero at t=0.the ramp signal resembles a constant velocity.
79.What is a parabolic signal.
The parabolic signal is a signal whose value varies as a square of time from an initial value of zero at t=0.This parabolic signal represents constant acceleration input to the signal.
80.What are the 3 constants associated with a steady state fault.
Positional fault constant
Velocity fault constant
Acceleration fault constant
81.What are the main advantages of generalized fault co-efficients.
i) Steady state is function of time.
ii) Steady state can be determined from any kind of input
82. elaborate the effects of adding a zero to a system.
Adding a zero to a system outcomes in pronounced early peak to system response thereby the peak overshoot increases appreciably.
83. State-Magnitude criterion.
The magnitude criterion states that s=sa will be a point on root locus if for that value of s , | D(s) | = |G(s)H(s) | =1
84.State – Angle criterion.
The Angle criterion states that s=sa will be a point on root locus for that value of s, , ?D(s) = ?G(s)H(s) =odd multiple of 180°
85. What is a dominant pole
The dominant pole is a pair of complex conjucate pair which decides the transient response of the system.
86.What is stepper motor?
A stepper motor is a device which transforms electrical pulses into equal increments of rotary shaft motion called steps.
87.What is servomotor?
The motors used in automatic control systems or in servomechanism are called servomotors. They are used to convert electrical signal into angular motion.
88.Name the test signals used in control system
the commonly used test input signals in control system are impulse step ramp acceleration and sinusoidal signals.
89.Define BIBO stability.
A linear relaxed system is stated to have BIBIO stability if every bounded input outcomes in a bounded output.
90.What is the necessary condition for stability.
The necessary condition for stability is that all the coefficients of the characteristic polynomial be positive.
91.What is the necessary and sufficient condition for stability.
The necessary and sufficient condition for stability is that all of the elements in the 1st column of the routh array should be positive.
92.What is quadrantal symmetry?
The symmetry of roots with respect to both real and imaginary axis called quadrantal symmetry.
93.What is limitedly stable system?
For a bounded input signal if the output has constant amplitude oscilllations Then the system may be stable or unstable under a few limited constraints such a system is called limitedly stable system.
94.What is synchro?
A synchro is a device used to convert an angular motion to an electrical signal or viceversa.
95.What is steady state error?
The steady state fault is the value of fault signal e(t) when t tends to infinity.
96.What are static fault constants.
The Kp Kv and Ka are called static fault constants.
97.What is the disadvantage in proportional controller?
The disadvantage in proportional controller is that it produces a constant steady state fault.
98.What is the effect of PD controller on system performance?
The effect of PD controller is to increase the damping ratio of the system and so the peak overshoot is decreased.
99.Why derivative controller is not used in control system?
The derivative controller produces a control action based on rare of change of fault signal and it does not produce corrective measures for any constant fault. Hence derivative controller is not used in control system
100.What is the effect of PI controller on the system performance.
The PI controller increases the order of the system by one, which outcomes in reducing the steady state fault .But the system becomes less stable than the original system.
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