120 + Interview Questions in Time Response Analysis in Control Systems Page 3 InterviewSolution

101.	A__________ translates signals from the controller into the motor voltage and current signals.(a) Servo motor(b) Servo amplifier(c) AC motor(d) DC motorThis question was posed to me in an interview for internship.The query is from Robotic Control System in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The CORRECT ANSWER is (b) Servo amplifier For explanation I would SAY: A servo amplifier monitors the feedback signal from the servomechanism and continually adjusts for deviation from expected BEHAVIOUR and translates signals from the controller into the motor voltage and current signals.

Discussion

102.	Which among the following are the interconnected units of state diagram representation?(a) Scalars(b) Adders(c) Integrator(d) All of the mentionedI had been asked this question during an internship interview.The above asked question is from State Variable Analysis topic in division Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Correct option is (d) All of the mentioned For explanation: Scalars, adders and INTEGRATOR are the INTERCONNECTED UNITS of state diagram REPRESENTATION and this representation helps in determination of the state of the control SYSTEM.

Discussion

103.	Classification of Robot is based on:(a) Geometry and geometric classification(b) Left right classification(c) Based on control system(d) All of the mentionedThe question was asked in final exam.Enquiry is from Robotic Control System topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right choice is (d) All of the mentioned The BEST I can EXPLAIN: Robots can be classified on the BASIS of the movement their STRUCTURE and geometry as HUMANOID robots and gantry robots.

Discussion

104.	The compensator Gc(s) =5(1+0.3s)/(1+0.1s) would provide a maximum phase shift of:(a) 20°(b) 45°(c) 30°(d) 60°I had been asked this question by my school teacher while I was bunking the class.Question is from Performance Indices in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Correct option is (c) 30° The EXPLANATION: Maximum PHASE SHIFT sin^^(-1)⁡ [(1-α)/(1+α)] and sin^^(-1)⁡[1/2] = 30°.

Discussion

105.	A system has a complex conjugate root pair of multiplicity two or more in its characteristic equation. The impulse response of the system will be:(a) A sinusoidal oscillation which decays exponentially; the system is therefore stable(b) A sinusoidal oscillation with a time multiplier ; the system is therefore unstable(c) A sinusoidal oscillation which rises exponentially ; the system is therefore unstable(d) A dc term harmonic oscillation the system therefore becomes limiting stableThe question was asked by my college professor while I was bunking the class.Origin of the question is Time Response of Second Order Systems topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The correct answer is (c) A sinusoidal oscillation which rises exponentially ; the SYSTEM is therefore UNSTABLE For explanation: POLES are the roots of the DENOMINATOR of the TRANSFER function and on imaginary axis makes the system stable but multiple poles makes the system unstable.

Discussion

106.	Which one of the following is an advantage of a PD controller in terms of damping and natural frequency?(a) G remains fixed but natural frequency increases(b) G remains fixed but natural frequency decreases(c) Natural frequency fixed but G increases(d) Natural frequency fixed but G decreasesThe question was asked in unit test.I need to ask this question from Design Considerations for Higher-Order Systems in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right choice is (c) NATURAL frequency FIXED but G increases To explain: COMPARING with the characteristic equation natural frequency remains fixed but the value of G that increases hence the transient response is improved.

Discussion

107.	The input signals to control systems are not known fully ahead of time, the characteristics of control system which suddenly strain a control system are:(a) Sudden shock(b) Sudden change(c) Constant velocity and acceleration(d) All of the mentionedI got this question during an interview.This interesting question is from Standard Test Signals topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The correct choice is (d) All of the mentioned To explain I would SAY: System DYNAMIC behavior for ANALYSIS and design is THEREFORE judged and COMPARED under standard test signals.

Discussion

108.	The standard second order system to a unit step input shows the 0.36 as the first peak undershoot, hence its second overshoot is:(a) 0.135(b) 0.216(c) 0.1296(d) 0.116This question was addressed to me during an online interview.My question is based upon Time Response of Second Order Systems topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The CORRECT option is (b) 0.216 For explanation I WOULD say: Overshoot and undershoot are calculated from the FORMULA of peak time as odd peaks denote the overshoot and even DENOTES the under shoot.

Discussion

109.	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 valueThis question was posed to me by my college director while I was bunking the class.This is a very interesting question from The Approximation of Higher-Order Systems by Lower-Order in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The CORRECT ANSWER is (c) Only one of the static error co-efficient has a finite non-zero value Easy explanation: Closed loop SYSTEM has one of the static error CONSTANT for any input that can be POSITION, velocity or acceleration error constant.

Discussion

110.	Hierarchicallevel control involves :(a) Level 1: Actuator control controls individual robot actuators(b) Level 2: Path control coordinates robot path movement(c) Level 3: Main control high level instruction interpreter(d) All of the mentionedThe question was posed to me in an interview for internship.Asked question is from Robotic Control System in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right option is (d) All of the mentioned Explanation: Hierarchy refers to the system where some form of levels are used as higher to LOWER or vice versa and this level CONTROL mainly involves ACTUATOR control, PATH control and MAIN control for various functioning of the parts of the robot.

Discussion

111.	The basic components of robot are:(a) The mechanical linkage(b) Sensors and controllers(c) User interface and power conversion unit(d) All of the mentionedThis question was posed to me by my school teacher while I was bunking the class.Asked question is from Robotic Control System in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right choice is (d) All of the mentioned The best I can explain: The basic components of robot are the MECHANICAL linkage, sensors and controllers, USER INTERFACE and power conversion UNIT.

Discussion

112.	Which of the following can be measured by the use of a tacho-generator?(a) Acceleration(b) Speed(c) Speed and acceleration(d) DisplacementThis question was posed to me during an interview.Origin of the question is Effect of Adding a Zero to a System topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right choice is (b) Speed For EXPLANATION: TACHO GENERATOR is used to measure the velocity or RELATIVE velocity of the SYSTEM.

Discussion

113.	Consider a system with transfer function G(s) = s+6/Ks^2+s+6. Its damping ratio will be 0.5 when the values of k is:(a) 2/6(b) 3(c) 1/6(d) 6The question was posed to me in my homework.This interesting question is from Time Response of Second Order Systems topic in division Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» CORRECT OPTION is (C) 1/6 To ELABORATE: s+6/K[s^2+s/K+6/K] COMPARING with s^2+2Gw+w^2 w= √6/K 2Gw=1/K 20.5√6/K =1/K K=1/6.

Discussion

114.	The system in originally critically damped if the gain is doubled the system will be :(a) Remains same(b) Overdamped(c) Under damped(d) UndampedI got this question in quiz.This interesting question is from Time Response of Second Order Systems in division Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» CORRECT OPTION is (C) Under damped For explanation: HENCE DUE to this G lies between 0 and 1.

Discussion

115.	Assertion (A): A PI controller increases the order of the system by units but decreases the steady state error.Reason (R): A PI controller introduces a pole at either the origin or at a desired points on the negative real axis.(a) Both assertion and reason are true and R is correct explanation of A(b) Both A and R true but R is not correct explanation of A(c) A is true but R is false(d) A is False but R is trueThe question was posed to me during an interview.My question is based upon Effect of Adding a Zero to a System in portion Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Right choice is (a) Both ASSERTION and reason are true and R is correct explanation of A Explanation: I is proportional +integral CONTROLLER. Thus integral controller add a pole either at origin or at the desired point on the negative real axis, so ORDER of the system GETS increased but it REDUCES the steady state error of the offset error.

Discussion

116.	If the performance index of a phase lead compensator is (s+a)/ (s+b) and that of a lag compensator is (s+p)/(s+q), then which one of the following sets of conditions must be satisfied?(a) a>b and pb and p
Answer» Correct option is (d) aq For explanation I would say: In PHASE LEAD compensator, zero is nearer to origin. In phase LAG compensator, POLE is nearer to origin.

Discussion

117.	Damping factor specifies:(a) Peak overshot to step input.(b) Steady state error(c) Damping ratio(d) Natural frequencyThis question was addressed to me by my college professor while I was bunking the class.My question comes from Effect of Adding a Zero to a System and Design Specifications of Second-order Systems in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The CORRECT choice is (a) Peak overshot to step input. The EXPLANATION: MAXIMUM peak OVERSHOOT is the maximum peak of the transient response at the resonant frequency and is so CALCULATED as to determine the value of damping factor.

Discussion

118.	Assertion (A): The zeroes on the real axis near the origin are generally avoided in design.Reason (R): In a sluggish system introduction of zeroes can improve the transient response(a) Both A and R are true and R is correct explanation of A(b) BothA and R are true but R is not correct explanation of A(c) A is true but R is false(d) A is false but R is trueThe question was asked during an interview.I need to ask this question from Effect of Adding a Zero to a System and Design Specifications of Second-order Systems topic in section Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» Correct OPTION is (b) BothA and R are true but R is not correct EXPLANATION of A Easy explanation: ZERO is defined as the root of the numerator of the transfer function and zero is to introduce a pronounced peak to the system’s RESPONSE whereby the peak overshoot may increase appreciably.

Discussion

119.	Ramp input :(a) Denotes constant velocity(b) Value increases linearly with time(c) It denotes constant velocity and varies linearly with time(d) It varies exponentially with timeI got this question in a job interview.My doubt stems from Standard Test Signals topic in chapter Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The correct ANSWER is (c) It DENOTES constant VELOCITY and varies LINEARLY with time To explain: Ramp signal denotes constant velocity and also basic definition states that its VALUE increases linearly with time.

Discussion

120.	The nature of transient response is revealed by ______________(a) Sine wave(b) Cos wave(c) Tan wave(d) Test signalsThis question was posed to me in final exam.This intriguing question originated from Standard Test Signals in section Time Response Analysis, Design Specifications and Performance Indices of Control Systems
Answer» The correct ANSWER is (d) Test signals To explain I would say: The nature is dependent on SYSTEM POLES not on the DYNAMIC inputs.

Discussion

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If the performance index of a phase lead compensator is (s+a)/ (s+b) and that of a lag compensator is (s+p)/(s+q), then which one of the following sets of conditions must be satisfied?(a) a>b and pb and p