© 2013 – University of the West of England
02/12/2013
UWE Bristol
Industrial Control UFMF6W-20-2
Control Systems Engineering UFMEUY-20-3
Lecture 1: Introduction to Control
Teaching • Course structure: – 1 hour lecture + 2 hour tutorial per week – Two modules, co-taught (assessments are different) – 14 weeks control (Ben Drew & Neil Larsen) – 6 weeks sensors and actuators (Sabir Ghauri)
• Tutorials: – 1st Semester: Classroom examples/problems – Tutorial Sheets on Blackboard (and solutions) – 2nd Semester: Laboratory (Simulink, DC motor control + sensors and actuators)
• Lecture videos
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© 2013 – University of the West of England
02/12/2013
Assessment • 1 coursework – laboratory report (40%) – Group report
• Exam after Easter Break (60%) • Reading list: – The Art of Control Engineering , Ken Dutton, Steve Thompson, Bill Barraclough – Control Engineering , W. Bolton – Control Systems Engineering , N.S. Nise – Aircraft Control and Simulation, B.L. Stevens & F.L. Lewis
Aims and Objectives • Control – System modelling – Transfer functions – System performance – System frequency response – System identification – Controller design
• Sensors and Actuators
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© 2013 – University of the West of England
02/12/2013
Today’s Lecture • Introduction to Control • Examples • Control Basics • Open- and Closed-loop control • Control System Design Steps • Example Models
Introduction to Control • What is a control system? • Common example in the human body: temperature control External temperature Sun, Illness, etc.
Body temperature !"#$
Sweat/shiver
&'(")
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© 2013 – University of the West of England
02/12/2013
Introduction to Control • Applications in: – Physiology – Economics – Many fields of engineering: • Hydraulics • Electronics • Mechanics • Etc.
Simple Examples • Car speed Desired speed
*+,"-./
0)12)/
• Room fan Desired cooling
4526'+
3/+2'./
Actual speed
System or Plant Electrical power
78.. 98)
Actual cooling
Controller
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© 2013 – University of the West of England
02/12/2013
Examples • Control systems are required in complex machines, devices – Aircraft control systems – Anti-lock braking systems – Manufacturing processes
Examples • Inverted Pendulum – Demo
• Videos – http://tinyurl.com/uwetriple – http://tinyurl.com/uweballrobot – http://tinyurl.com/uwebigdog – http://tinyurl.com/uwekestrel
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© 2013 – University of the West of England
02/12/2013
Control Basics • What is common for all these systems? • A physical quantity has to be maintained at a fixed value (or series of values) • What information is necessary? – What the system needs to do – How well is the system is doing – What control action keeps maintains the action
Open and Closed Loop Control • Open Loop – Turntable example Battery
Speed Turntable
Speed setting
Desired speed (voltage)
DC motor
:; &<=.2>/,
;")6,". :/A2'/
&'6?86",
B,"'/CC
&<=.2>/,
:; <"6",
*?,)68@./
Actual speed
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© 2013 – University of the West of England
02/12/2013
Open and Closed Loop Control • Closed Loop Battery
Speed Turntable
+
Speed setting
DC motor
:; &<=.2>/,
–
Tachometer Desired speed (voltage) +
Error –
;")6,". :/A2'/
&'6?86",
B,"'/CC
&<=.2>/,
:; <"6",
*?,)68@./
Actual speed
4/)C",
Measured speed (voltage)
*8'+"
Open and Closed Loop Control • Cruise control example – Closed loop Desired + Error speed – Feedback
*+,"-./
0)12)/
3/+2'./
Actual speed
4=//# C/)C",
– Output compared to the input – Error is used to drive the system
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© 2013 – University of the West of England
02/12/2013
Open and Closed Loop Control • Oven example – Closed loop Error + Desired temperature –
Feedback
Electrical power
4526'+
D/8()1 /./
Actual temperature
*/<=/,86?,/ C/)C",
– Output compared to the input – Error is used to drive the system
Open and Closed Loop Control • Components in a Closed Loop System demand
error
+ –
;")6,"../,
B.8)6
output
4/)C",
feedback – Normally depicted in a block diagram – Plant provides the system output – Controller takes the control input and provides a control output – Sensor takes the output and feeds it to the subtractor (or comparator) that compares the demand (the setpoint value) with the output of the sensor to produce an error – All connected by arrows, which represent signals
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© 2013 – University of the West of England
02/12/2013
Control System Design • Understand the general schemes that can be used to control a system. • Understand the system you’re trying to control. You need to predict how a system behaves – mathematical techniques that involve differential equation solution
Control System Design Steps 1. System analysis – establish requirements (talk to users) 2. Formal specification of required system performance 3. System modelling – system must be accurately modelled before controller design can commence. Usually a differential equation (some quantity that changes w.r.t. time) 4. Control algorithm development – the controller is developed using the model and standard control theory to meet the specifications.
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© 2013 – University of the West of England
02/12/2013
System Modelling • Dynamic behaviour of the system • Linear or non-linear fashion • System dynamics – how its output changes in response to a particular input
Example • Furnace F Fuel flow rate (kg/s)
!
E?,)8'/
Temp (deg C)
• The temperature of the furnace does not change instantaneously for changes in fuel rate • Differential equation describes the influence of time on the input response • Differential equations are derived from first principles
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© 2013 – University of the West of England
02/12/2013
Example models • Liquid level tank • RC circuit • Car suspension
Example 1: Liquid Level • Flow in – Flow out = rate of accumulation of liquid in the tank
C/S area = A
Qin
assume Qout= kh (k is a constant)
h Qout
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© 2013 – University of the West of England
02/12/2013
Example 1: Liquid Level • Flow in – Flow out = rate of accumulation of liquid in the tank Qin ! Qout = A C/S area = A
Qin
Qin ! kh = A
assume Qout= kh (k is a constant)
Qin
h Qout
=
A
dh dt
+
dh
dt dh dt kh
First order differential equation
Example 2: RC circuit • Differential equation that related Vout to Vin R Vin
C
Vout
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© 2013 – University of the West of England
02/12/2013
Example 2: RC circuit • Differential equation that related Vout to Vin R C
Vin
Vout
V in
! V out = iR = C
V in
= V out + CR
dV out
Capacitor current :
i
=
C
dv dt
R
dt
dV out dt
Example 3: Car Suspension • Mass/spring/damper system
Fin
m k
xout
D
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© 2013 – University of the West of England
02/12/2013
Example 3: Car Suspension • Mass/spring/damper system 2
Inertia : F Fin
m
ma
=
Damping : F Spring : F
xout
=
=
=
M
Dv
d x 2
dt =
D
dt
kx
Applying Newton' s Second Law : 2
k
dx
D
m
d xout 2
dt
=
!kx ! D
2
m
d xout 2
dt
+ D
dx dt
+
dx dt
kx
+ F in
= F in
Today’s lecture • Control is an intrinsic part of humans and a vital part of many engineering systems • In order to control a system, we need to know the system/plant itself and control methods • Description of a system to be controlled – system model is a starting point of the control system design •
Tutorial sheet 1:
On blackboard. Determining differential equations for systems
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