Lec01: Objectives
At the end of the lecture, I should be able to:
• Understand the purpose of control engineering
• Describe the basic of control system.
• Differentiate between open loop and closed loop control
system.
• Discuss the elements of control system.
FAQs
 What is Control?
 What is Control System?
 What is the purpose of a Control System?
Control Terminology
Control is a process of
causing a system
variable to conform or to
follow the desired value
or path, known as the
reference value.
Eg:
• Traffic controller
• Temperature controller
• Blood pressure
Control Terminology
A control system is an interconnection of
components forming a system configuration that
will provide a desired system response.
Input, u
'System'
or 'Plant'
Output y
Purpose of Control System
 Power amplification
 Remote control
 Convenience of inputs form
 Compensation of disturbance
Type of Control System
Open-loop control
F
ad
m̂
Model Est. mass
1
m
F
a
1
m
a
Physical mass plant
Open-loop Control
ad
F
m̂
1
m
a
Control system
Feedforward control system takes the desired output,
combines it with knowledge about system (in this example.
an estimate of mass) to generate control effort (here a
force)
Open-loop Control
ad
m̂
m
a
mˆ
 1 then a  ad
• If
m
•Accuracy depends on how good m̂ is
•Doesn’t account for unmodelled effects such as
other forces act, e.g. friction, Windage losses,
etc.
Closed-loop Control
Desired
output
+ Error Plant
-
Actuation effort
Idea: use difference
between actual output
(error) and desired
output ‘drive’ the plant.
Actual output
Sensor
Closed-loop Control
Actuator: generates K Newtons
for every m/s2 error in acceleration
Error signal
ad
F
e
+
_
Force applied to mass
K
1
a
m
Sensed
acceleration
Closed-loop Control
m
1
a
 ad
1 m / K m
Larger K, the better the approximation
of first term to m.
Element of Control System
Summing
Junction
Input
d
Controller
Actuator
Error
Signal
Feedback
Sensor
System
Output