Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III Year CONTROL SYSTEMS Previous Question Paper (August - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain the difference between open loop and closed loop system.
Answer
An open-loop control system is one in which the control action is independent of the output. It does not have feedback, making it simple and inexpensive but sensitive to external disturbances and parameter variations. Calibration is essential for accuracy.
A closed-loop control system (or feedback control system) is one in which the control action is dependent on the output. It uses a feedback element to compare the actual output with the desired input (reference), generating an error signal that the controller minimizes. This provides greater accuracy, stability, and robustness against disturbances, though it is more complex and costly to design.
Define transfer function and derive an expression for the transfer function of a closed loop system with a unity feedback.
Answer
The transfer function of a linear time-invariant (LTI) system is defined as the ratio of the Laplace transform of the output to the Laplace transform of the input, assuming all initial conditions are zero.
For a closed-loop system with a forward path gain
The output is related to the error by:
Substituting
The transfer function
Determine transfer function X(s)/f(s) for a given mechanical system shown below.
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What is the effect of feedback?
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An experiment conducted on a servo mechanism shows the error response to be e(t) = 1.4 e-4t sin(2.86t + 43°). Where the input is a sudden unit displacement. Determine the natural frequency, damping ratio and damped angular frequency of the system.
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Construct Routh Array and determine the stability of the system whose characteristic equation is S6 + 2S5 + 8S4 + 12S3 + 20S2 + 16S + 16 = 0. Also determine the number of roots lying on right half of s-Plane, left half of s-plane and on imaginary axis.
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What is break away and break in points? A unity feedback system has an open loop transfer function U(s). Find its break away and break in points.
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Plot the bode diagram for the following Transfer function and obtain the gain and phase crossover frequencies.
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Define gain margin and phase margin.
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Explain relation between time and frequency response analysis.
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What is compensation? What are the different types of compensators? Explain in brief.
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Obtain the state transition matrix for the state model whose matrix A is given.
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Consider the system = AX + Bu, Y = CX. Test for controllability and observability.
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