JNTU
JNTU B.Tech III CONTROL SYSTEMS ENGINEERING Previous Question Paper (November/December - 2017 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
PART - A
Explain about various types of control systems with examples briefly.
Answer
Control systems are broadly classified into two categories based on the presence of feedback:
- Open-Loop Control Systems: The control action is independent of the output. There is no feedback mechanism to correct errors. Example: An electric toaster or a washing machine that operates on a fixed timer.
- Closed-Loop Control Systems: The control action depends on the output. A feedback path compares the actual output with the desired input to minimize error. Example: An air conditioner with a thermostat or a cruise control system in a car.
Briefly explain about the characteristics of feed-back signal.
Answer
The feedback signal in a control system is a portion of the output signal that is returned to the input to be compared with the reference signal. Its primary characteristics are as follows:
- Comparison: The feedback signal is subtracted from (negative feedback) or added to (positive feedback) the reference input to generate an error signal, which drives the system.
- Stability and Sensitivity: Negative feedback typically reduces the system's sensitivity to parameter variations and external disturbances, while improving overall system stability.
- Bandwidth and Accuracy: Feedback allows for the adjustment of system bandwidth and significantly improves steady-state accuracy by minimizing the error between the desired output and the actual output.
Why test signals are needed? Explain various test signals used in feed-back control systems.
Answer
Sign in to view the complete answer paper.
Define time constant and explain its importance.
Answer
Sign in to view the complete answer paper.
Explain the concept of stability of a control system with an example.
Answer
Sign in to view the complete answer paper.
Distinguish between qualitative stability and conditional stability of a control system.
Answer
Sign in to view the complete answer paper.
What is compensation? Explain different types of compensators.
Answer
Sign in to view the complete answer paper.
Define gain margin and phase margin in frequency domain stability analysis.
Answer
Sign in to view the complete answer paper.
Discuss the significance of state Space Analysis.
Answer
Sign in to view the complete answer paper.
Define state variables.
Answer
Sign in to view the complete answer paper.
PART - B
Explain the operation of ordinary traffic signal, which control automobile traffic at roadway intersections. Why are they open loop control systems? How can traffic be controlled more effectively?
Answer
Sign in to view the complete answer paper.
For the system represented in figure 1, obtain transfer function C/R1, C/R2.
Answer
Sign in to view the complete answer paper.
Derive the transfer function of the following electrical network Vo(s)/Vi(s) figure 2.
Answer
Sign in to view the complete answer paper.
For a signal flow graph in figure 3, determine the overall gain by masons gain formula.
Answer
Sign in to view the complete answer paper.
A unity feedback system is characterized by an open-loop transfer function G(s)= K/s(s+5). Determine the gain K so that the system will have a damping ratio of 0.5. For this value of K determine settling time, peak overshoot and time to peak overshoot for a unit-step input.
Answer
Sign in to view the complete answer paper.
The open-loop transfer function of a servo system with unity feedback is G(s)=10/s(0.1s+1). Evaluate the static error constants (Kp, Kv, Ka) for the system. Obtain the steady-state error of the system when subjected to an input given by the polynomial r(t)=a0+a1t+a2t^2/2.
Answer
Sign in to view the complete answer paper.
A unity feedback system has forward transfer function G(s) = 20/(s+1). Determine and compare the response of the open and closed loop systems for unit step input. Suppose now that parameter variation occurring during operating conditions causes G(s) to modify to G'(s)=20/(s+0.4). What will be the effect on unit-step response of open and closed loop systems? Comment upon the sensitivity of the two systems to parameter variations.
Answer
Sign in to view the complete answer paper.
The response of a system subjected to a unit step input is c(t) = 1 + 0.2e^(-60t) - 1.2e^(-10t). Obtain the expression for the closed loop transfer function of the system. Also determine the undamped natural frequency and damping ratio of the system.
Answer
Sign in to view the complete answer paper.
Apply R-H criterion to determine stability of the system with the following characteristic equation 2s^4 + 10s^3 + 5s^2 + 5s + 10 = 0. Find the number roots with positive real parts, if any.
Answer
Sign in to view the complete answer paper.
Explain the limitations of Routh’s stability criteria.
Answer
Sign in to view the complete answer paper.
Plot the root locus for the system with G(s)H(s) = K(s+1)(s+3) / s^3. Sketch the root locus and determine the range of K for which the system is stable.
Answer
Sign in to view the complete answer paper.
Sketch the Bode plots for a system G(s) = 15(s+5) / s(s^2+16s+100). Hence determine the stability of the system.
Answer
Sign in to view the complete answer paper.
Explain the effect of addition of a pole at the origin on the polar plot of a given system.
Answer
Sign in to view the complete answer paper.
Sketch the polar plot and hence find the frequency at which the plot intersects the positive imaginary axis for the system G(s) = 0.1 / s(1+s)(1+0.1s). Also find the corresponding magnitude.
Answer
Sign in to view the complete answer paper.
Obtain the state variable representation of an armature controlled D.C Servomotor.
Answer
Sign in to view the complete answer paper.
Derive the state models for the system described by the differential equation in phase variable form. d3y/dt3 + 4d2y/dt2 + 5dy/dt + 2y = 2d2u/dt2 + 6du/dt + 5u.
Answer
Sign in to view the complete answer paper.
Obtain the solution of a system whose state model is given by X' = AX(t) + BU(t); X(0) = X0 and hence define state Transition matrix.
Answer
Sign in to view the complete answer paper.
Obtain the state model of the system shown in figure 4. Consider the state variables as i1, i2 and v.
Answer
Sign in to view the complete answer paper.