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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 (Autumn) Examinations 2009/
Module Title: Electrical Control Engineering
Module Code: ELEC 7003
School: Electrical and Electronic Engineering
Programme Title: Bachelor of Engineering in Electrical Engineering-Award
Programme Code: EELEC_7_Y
External Examiner(s): Mr. G. Beecher, Dr. M. Duffy.
Internal Examiner(s): Mr. P.F.O’Murchu.
Instructions: Answer any three questions
Duration: 2 Hours
Sitting: Autumn 2010
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the
correct examination paper.
If in doubt please contact an Invigilator.
Q1.
The plots shown in Fig. 1a and Fig. 1b below are the output responses from two separate systems, a
first order and a second order respectively, which have been subjected to a unit step input in each
case.
(i) Evaluate the transfer function of each of the individual systems. 12marks
(ii) Produce a pole-zero diagram for each of the systems 3marks
(iii) Evaluate each of the system responses in the time domain using the inversion tables.
5marks
Time Response
Time
Voltage
0.00 0.0 5.5 11.0 16.5 22.0 27.5 33.
1.
3.
5.
7.
9.
10.
0
0.
0.
0.
0.
1
1.
1.
1.
0 1 2 3 4 5 6
Fig. 1a
Fig. 1b
Q4.
The simplified model of the d.c. motor considers only the mechanical time constant as the electrical
time constant is normally much shorter.
The input to the d.c. motor is electrical d. c. supply voltage and the output is shaft speed.
Simplified Model of D.C. Motor
Given that; T Kt Ia , where T is the mechanical torque produced, and Vb Kb , where Vb is the
back e.m.f. generated in the armature.
(a) Produce the block diagram consisting of the system transfer functions in the Laplace domain
8marks
(b) Evaluate the complete system transfer function which relates output speed to input voltage, and
verify that the following equation is the correct representation.
12marks
t b
t
i sJR BR KK
K
V s
s
Vi Vb
R
J
B
Ia f
I
