1

Control Systems Engineering

Introduction

IESL-Part III

2013

2

What is a Control System?Why need Control?

What is the subject about?

3

History of Control Engineering * Greece (BC) – Float regulator mechanism* Holland (16th Century)– Temperature regulator

* Watt’s Flyball Governor (18th century)

4

Water-level float regulator

History of Control Engineering

5

Applications of Control

System Engineering

6

Example of Control Systems

7

Control System Concepts• A system is a collection of components which

are co-ordinated together to perform a function.

• Systems interact with their environment across a separating boundary.

• The interaction is defined in terms of variables.– system inputs– system outputs– environmental disturbances

8

System

Disturbance Inputs

System Outputs

Subsystem

Environment

Control Inputs

9

System Variables• The system’s boundary depends upon the

defined objective function of the system.• The system’s function is expressed in terms of

measured output variables.• The system’s operation is manipulated

through the control input variables.• The system’s operation is also affected in an

uncontrolled manner through the disturbance input variables.

10

Car and Driver Example• Objective function: to control the direction

and speed of the car.• Outputs: actual direction and speed of the car• Control inputs: road markings and speed signs• Disturbances: road surface and grade, wind,

obstacles.• Possible subsystems: the car alone, power

steering system, braking system, . . .

11

Antenna Positioning Control System

• Original system: the antenna withelectric motor drive systems.

• Control objective: to point theantenna in a desired reference direction.

• Control inputs: drive motor voltages.• Outputs: the elevation and azimuth of the

antenna.• Disturbances: wind, rain, snow.

12

Studying Part III Control Engineering

• Objective function:

• Outputs:

• Control inputs:

• Disturbances:

• Subsystems:

13

• Objective function:

• Outputs:

• Control inputs:

• Disturbances:

• Subsystems:

Traffic Control Lights

14

Control System Design Objectives

• Primary Objectives:1. Dynamic stability2. Accuracy3. Speed of response

• Addition Considerations:4. Robustness (insensitivity to parameter variation)5. Cost of control6. System reliability

15

Response of a position control system showing effect of high and low controller gain on the output response

16

Response of a position control system

17

Video Segments

Master-Slave of Humanoid Robot

Laser cutting robot

Brain control hand Inverted Pendulum

Balancing Robot

18

Types of Control system Configurations

Multivariable Control System

Open-Loop Control Systems utilize a controller or control actuator to obtain the desired response.

Closed-Loop Control Systems utilizes feedback to compare the actual output to the desired output response.

19

Open loop Control

Close loop control

20

Close loop control system

21

Control System Components• System or process (to be controlled)• Actuators (converts the control signal to a power

signal)• Sensors (provides measurement of the system

output)• Reference input (represents the desired output)• Error detection (forms the control error)• Controller (operates on the control error to form

the control signal, sometimes called compensators)

22

Feedback

• Feedback is a key tool that can be used to modify the behavior of a system.

• This behavior altering effect of feedback is a key mechanism that control engineers exploit deliberately to achieve the objective of acting on a system to ensure that the desired performance specifications are achieved.

23

Examples of Control SystemsShip Autopilot Control System

• Actual heading is measured by a gyro-compass (or magnetic compass), compared with desired value. Error are send to autopilot (Course-keeping system)

• Actual rudder angle is sensed, and autopilot controls the ship course by steering-gear.

24

Examples of Control SystemsRoom Temperature Control System

• Proportional mode: Better accuracy, complex

• On/Off control mode: Thermostatic control, simple, low accuracy

25

Examples of Control SystemsAircraft Elevator Control System

• Hydraulic servomechanisms have a good power/weight ratio, and are ideal for applications that require large forces to be produced by small and light devices.

26

Summary

We have introduced:• Why do we need Control?• What is a Control System?• What are the main performance we care

for a control system?• Feedback is very important.

27

Summary The central problem in control is

to find a technically feasible way to act on a given process so that the process behaves, as closely as possible, to some desired behavior. Furthermore, this approximate behavior should be achieved in the face of uncertainty of the process and in the presence of uncontrollable external disturbances acting on the process.

28

What is a Control System?Why need Control?

What is the subject about?

Did you get answers to following?......

29