l1 - introduction to control

8/12/2019 L1 - Introduction to Control

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UWE Bristol

Control Systems EngineeringUFMEUY-20-3Aerospace Systems, Avionics and Control

UFMFB7-30-2

ControlUFMFV7-15-2

Lecture 1: Introduction to Control


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Teaching

Course structure:

1 hour lecture + 2 hour tutorial per week

Two modules, co-taught (assessments are different)

14 weeks control 6 weeks sensors and actuators

Delivered by Ben, Neil and Sabir

Tutorials: 1stSemester: Classroom examples/problems

Tutorial Sheets on Blackboard (and solutions)

2ndSemester: Laboratory (Simulink, DC motor control

+ sensors and actuators)


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Assessment

1 courseworklaboratory 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


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Todays Lecture

Introduction to Control

Examples

Control Basics Open- and Closed-loop control

Control System Design Steps

Example Models


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What is a control system?

Common example in the human body:

temperature control

Body

Action

External temperature

Sun, Illness, etc.

Body temperature

Sweat/shiver


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Applications in:

Physiology

Economics

Many fields of engineering:

Hydraulics

Electronics

Mechanics Etc.


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Simple Examples

Car speed

Room fan

Throttle EngineDesired speed Actual speed

Vehicle

Actual coolingSwitch Wall fanDesired

cooling

Electrical

power

System or Plant

Controller


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Examples

Control systems are required in complex

machines, devices

Aircraft control systems

Anti-lock braking systems

Manufacturing processes


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Examples

Inverted Pendulum

Demo

Videos

http://tinyurl.com/uwetriple

http://tinyurl.com/uweballrobot

http://tinyurl.com/uwebigdog

http://tinyurl.com/uwekestrel
http://tinyurl.com/uwetriplehttp://tinyurl.com/uweballrobothttp://tinyurl.com/uwebigdoghttp://tinyurl.com/uwekestrelhttp://tinyurl.com/uwekestrelhttp://tinyurl.com/uwebigdoghttp://tinyurl.com/uweballrobothttp://tinyurl.com/uwetriple


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Open and Closed Loop Control

Open Loop

Turntable example

DC Amplifier

Battery

Speed

settingDC motor

Speed

Turntable

Amplifier DC motor Turntable

Control Device Actuator Process

Desired speed

(voltage)

Actual speed


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Closed Loop


DC Amplifier

Battery

Speed

settingDC motor

Speed

Turntable

+

Tachometer

Amplifier DC motor Turntable

Control Device Actuator ProcessDesired speed

(voltage) Actual speed+

Tachometer

Sensor

Error

Measured speed

(voltage)


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Cruise control example

Closed loop

Output compared to the input

Error is used to drive the system

Throttle EngineDesiredspeed

Actual

speed

Speed sensor

Error

Feedback

+

Vehicle


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Oven example

Closed loop

Output compared to the input

Error is used to drive the system

SwitchHeating

elementDesired

temperature

Actualtemperature

Temperature

sensor

Error

Feedback

+

Electrical

power


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Components in a Closed Loop System

Normally depicted in a block diagram

Plantprovides the system output

Controllertakes the control input and provides a control output

Sensortakes 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

Controller Plantdemandoutput

Sensor

error

feedback

+


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Control System Design

Understand the general schemes that can

be used to control a system.

Understand the system youre trying to

control. You need topredict how a system

behavesmathematical techniques that

involve differential equation solution


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Control System Design Steps

1. System analysisestablish requirements (talk

to users)

2. Formal specification of required system

performance3. System modellingsystem must be accurately

modelled before controller design can

commence. Usually a differential equation

(some quantity that changes w.r.t. time)

4. Control algorithm developmentthe controller

is developed using the model and standard

control theory to meet the specifications.


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System Modelling

Dynamic behaviour of the system

Linear or non-linear fashion

System dynamicshow its outputchanges in response to a particular input


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Example

Furnace

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

FurnaceFuel flow

rate (kg/s)

Temp (deg C)

F


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Example models

Liquid level tank

RC circuit

Car suspension


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Example 1: Liquid Level

Flow inFlow out = rate of accumulation

of liquid in the tank

Qin

Qout

h

C/S area = A

assume Qout= kh

(k is a constant)


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Example 1: Liquid Level

Flow inFlow out = rate of accumulation

of liquid in the tank

Qin

Qout

h

C/S area = A

assume Qout= kh

(k is a constant)

khdt

dh

AQ

dt

dhAkhQ

dt

dhAQQ

in

in

outin

First order differential equation


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Example 2: RC circuit

Differential equation that related Voutto Vin

R

CVin Vout


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Example 2: RC circuit

Differential equation that related Voutto Vin

R

CVin Vout

dt

dVCRVV

Rdt

dV

CiRVV

out

outin

outoutin

dtdvCi :currentCapacitor


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Example 3: Car Suspension

Mass/spring/damper system

m

Fin

k D

xout


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Example 3: Car Suspension

Mass/spring/damper system

m

Fin

k D

xoutkxF

dtdxDDvF

dt

xdMmaF

:Spring

:Damping

:Inertia2

2

inout

inout

Fkx

dt

dxD

dt

xdm

Fdt

dxDkx

dt

xdm

2

2

2

2

:LawSecondsNewton'Applying


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Todays 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

l1 - introduction to control

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