Cork Institute of Technology
Bachelor of Engineering (Honours) in Mechanical Engineering – Award
(Bachelor of Engineering in Mechanical Engineering – Award)
(NFQ – Level 8)
Summer 2005
Systems Engineering and Control
(Time: 3 Hours)
Answer any FIVE Questions Examiners: Prof. J. Monaghan
ALL questions carry equal marks. Mr. J. Hegarty
Dr. M. J. O’Mahony
1. Construct the Bode Diagram for the control system with the following open loop transfer
function:
100(0.1 1)
() () (1)(0.011)
D
s
T
se
GsHs
ss s
−
+
=
+
+
(i) Assuming initially TD=0; determine the gain margin and phase margin for the system.
(8 marks)
Comment on its stability and what value of damping ratio would you expect to obtain?
(4 marks)
(ii) Determine the limiting value of dead time TD so that the system remains stable. Discuss
how dead time effects arise in practice. (8 marks)
2. (a) State and discuss the Nyquist Stability Criterion. (6 marks)
(b) Plot the Nyquist Contour for the system with the following open loop transfer function;
123
() () (1)(1)(1)
K
GsHs
Ts T s Ts
=
+
++
Comment on the stability of the system. (8 marks)
If T1 = 1, T2 = 0.5 and T3 = 0.2 determine the value of K that;
i. will give a gain margin of 8 dB. (6 marks)
