The Open University of Sri Lanka

Diploma in Technology - Level 04

Academic Year – 2011/12

MEX 4243 CONTROL SYSTEMS ENGINEERING - TMA 3

(1) Answer all questions.

(2) Write your registration number clearly on your answer script.

(3) Send your answer scripts under registered cover to the address given below or put it into

the assignment box available at the Department of Mechanical Engineering (Block 17),

Nawala.

THE COURSE CO-ORDINATOR IN MEX4243

DEPARTMENT OF MECHANICAL ENGINEERING

THE OPEN UNIVERSITY OF SRI LANKA

P.O. BOX 21, NAWALA

NUGEGODA.

(4) Last date of submission 23rd May 2013

(5) No late submissions will be accepted.

Question 01

Sketch the Nyquist plot and determine stability of the open-loop transfer function of unity

feedback control system. Use MATAB to plot the Nyquist plot and verify the answer.

𝐺(𝑠)𝐻(𝑠) =𝐾(𝑠 − 3)2

(𝑠 + 1)2

Question 02

Sketch the Nichols Chart and determine the Main Margin and Phase Margin of unity feedback

control system. Use MATAB to plot the Nichols Chart and verify the answer.

𝐺(𝑠) =3(𝑠 + 2)2

𝑠2(𝑠2 + 10𝑠 + 100)

Question 03

The forward path transfer function of a unity negative feedback control system is given by

𝐺(𝑠) =𝐾

𝑠(𝑠 + 3)(𝑠 + 10)

The system has to satisfy the following specifications:

Phase margin≥30°

Gain Margin ≥20dB and

Design a suitable Lead Compensator.

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