8/11/2019 Bsc-Electrical-Level 03- Semester 01-2009-2010- EE
3220 Control Theory
1/4
University of Moratuwa
085
Faculty of
Engineering
Department of Electrical Engineering
B.Sc.
Engineering
Level 3 - Semester 1 Examination
EE 3220 CONTROL THEORY
Time Allowed:
2 Hours
February
2010
ADDITIONAL MATERIALS:
None
INSTRUCTIONS TO CANDIDATES:
This paper contains 3 questions on 4 pages
This examination accounts for 70 of the module assessment. The
marks assigned for each
question there of are indicated in square brackets. The total
maximum mark attainable is 70.
This is a closed book examination.
Answer all 3 questions.
Assume reasonable values for any data not given in or with the
examination paper. Clearly
state such assumptions made on the script.
If you have any doubts as to the interpretation of the wording
of a question, make your own
decision, but clearly state it on the script.
All examinations are conducted under the rules
&
regulations of the university.
8/11/2019 Bsc-Electrical-Level 03- Semester 01-2009-2010- EE
3220 Control Theory
3/4
Tm ktiaand between back emf and rotor speed is eb = kbW m where
ktl kb are
torque constant and back emf constant, respectively [04]
b Obtain the transfer function of the motor to be used for shaft
position control
through armature voltage control. Assume no-load conditions
[041
c Explain why the initial conditions are usually ignored when
taking the Laplace
transform of the differential equations in part-(b) [02]
d Give a fully labelled complete motor block diagram
representation
[04]
e How do you modify the equations in part-(a) when the motor
shaft is loaded with a
mechanical load with a constant load torque of T and load
inertia i Viscous-friction
coefficient of load is
B [04 ]
f
If position control of the loaded motor is to be implemented
using conventional
error feedback control system architecture, give a fully
labelled block diagram of the
control system [02]
g f the same motor is to be used for a speed control
application, obtain a suitable
transfer function for the motor. Clearly define the input and
the output [04]
h Attitude control of an airplane is realized by controlling the
positions if its control
surfaces, namely, ailerons, rudder, and elevators. The
underlining DC motor is to be
used to control one of such control surfaces of an airplane.
Neglecting the armature
inductance, a 2
nd
order approximation is made to the 3
rd
order system. Control system
is to be implemented using proportional controller and
conventional error feedback
control architecture. Forward path transfer function is
4500K
Gs
=
s s
+ 361.2
where Kis the adjustable control gain. Assume an unity
feedback
H s
=
I
control
system.
(i)
(iv)
Obtain the characteristic equation of the control system and its
roots in
terms of K [04]
Sketch the root locus for this contro 1 system [04]
What can be said about the system response when 1)
K
