PE-3032 Introduction to Control Systems Engineering

Professor Charlton S. InaoControl System Engineering/MechatronicsDefence Engineering University College

2012 Bishoftu, Ethiopia

Introduction to control systems, open and closed loop control, control building blocks and transfer functions, Laplace transformation, mathematical model of physical systems, servomechanism, characteristics, and performance of feedback control systems, transient response analysis of zeros, first and second order systems stability analysis in feedback controls, Root locus and frequency response method, Nyquist/Bode diagrams, lead-lag PID compensators. Introduction to digital control, state space analysis and control systems hardware considerations.

CO1 Ability to apply various mathematical principles (from

calculus and linear algebra) to solve control system problems.

CO2 Ability to obtain mathematical models for such mechanical,

electrical and electromechanical systems. CO3

Ability to derive equivalent differential equation, transfer function and state space model for a given system.

CO4 The ability to perform system’s time and frequency-domain

analysis with response to test inputs. Analysis includes the determination of the system stability.

At the end of the whole course, the student is expected to develop the following:

Mid-Term : 30% Final Examination : 50% Lab Assessment : 10% Assignments : 10%

Total Mark : 100%

Textbook Ogata K. (2002). Modern Control Engineering (3rd Ed), Prentice

Hall.

References1. W. Bolton , Control Engineering ,3rd Edition, 2005, Longman

Publication 2. Benjamin C. Kuo and Farid Golnaraghi, “Automatic Control

Systems”, John Wiley, 2003 3. Norman S. Nise, Benjamin Cummings, “Control Systems

Engineering”, 4th edition, 2004 4. Richard C. Dorf and Robert H. Bishop, “Modern Control

Systems”, Addison Wesley, 7th Edition, 1995

Lecturer

Prof. Charlton S. InaoBS. Mech .Eng (Philippines, M.Eng (Germany),

AdvancedProduct Design and Development Study major in Automation – -

Germany Advanced Plant Process and Control and Mechatronics - Japan

Advanced Research and Experimental Design, Six Sigma and Taguchi Method Studies, Laser Printer Control and Design

- IBM- Lexmark, Kentucky, USA

Week Course Content

1-2 Introduction to Control Systems

3-4 The Basics of Control Theory

5-6 Mathematical Model of Systems

7-8 System Response and Stability

10-12 The Root Locus Method

13-14 Frequency Response Method

15 PID Controllers

16-17 State Space Analysis and Digital Control

Basic Concepts Classification of systems and signals Classification of control systems Control System Application examples Exercises

System A collection of components which are coordinated

together to perform a function. Dynamic System

A system with a memory. For example, the input value at time t will influence

the output at future instant. A system interact with their environment through a

controlled boundary.

The interaction is defined in terms of variables.i. System inputii. System outputiii. Environmental disturbances

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 control input variables.

The system’s operation is also affected in an uncontrolled manner through disturbance input variables.

Control is the process of causing a system variable to conform to some desired value.

Manual control Automatic control (involving machines only).

A control system is an interconnection of components forming a system configuration that will provide a desired system response.

Control System

Output

Signal

Input Signa

l

Energy

Source

Control is a process of causing a system variable such as temperature or position to conform to some desired value or trajectory, called reference value or trajectory.

For example, driving a car implies controlling the vehicle to follow the desired path to arrive safely at a planned destination.i. If you are driving the car yourself, you are performing manual

control of the car.

ii. If you use design a machine, or use a computer to do it, then you have built an automatic control system.

Transient response: Gradual change of output from initial to the desired

condition Steady-state response:

Approximation to the desired response For example, consider an elevator rising from

ground to the 4th floor.

Component or process to be controlled can be represented by a block diagram.

The input-output relationship represents the cause and effect of the process.

Control systems can be classified into two categories:i. Open-loop control systemii. Closed-loop feedback control system

Process Output

Input

An open-loop control system utilizes an actuating device to control the process directly without using feedback.

A closed-loop feedback control system uses a measurement of the output and feedback of the output signal to compare it with the desired output or reference.

Actuating Device Process Output

Desired Output

Response

Desired Output

Response

Measurement

Output

Controller

ProcessComparison

Single Input Single Output (SISO) System

In an open loop control system, the input to the plant does not in any way depend on the current and past values of the output of the plant.

Relatively simple and consequently low cost with generally good reliability.

An open-loop control system is one in which the control action is independent of the output.

Motor low pass filter Inertia supported between two bearings Heater /boiler Cooking Oven Water valve system in a pool or sink

The biggest problem with the open loop control systems is that they rely totally in calibration, and ca not effectively deal with exogenous disturbances.

They can not effectively deal with changes in the process.

Can not deal with uncertainty. Can not stabilize an unstable system. Often in accurate since there is no

correction for error.

Closed loop control system make the control system robust to uncertainty and disturbances.

It senses the output of the system and adjust the control input using feedback rules, which are based on how the system output deviates from the system behaves.

The feedback helps compensate for the differences, if the system behaves slightly differently than the model.

Relatively accurate in matching the actual to the required values.

More complex, and more expensive, grater chance of breakdown due to number of components.

Feedback is that property of a closed-loop system which permits the output (or some other controlled variable) to be compared with the input to the system (or an input to some other internally situated component or subsystem) so that the appropriate control action may be formed as some function of the output and input

Comparison element Control element Correction Element Process element Measurement element

A closed-loop control system is one in which the control action is somehow dependent on the output.

Guided missiles automatic gain control in radio receivers satellite tracking antenna Etc.

Open-Loop Control System

Missile Launcher System

Closed-Loop Feedback Control System

Missile Launcher System

Desired Output

Response

Measurement

Output Variabl

es

Controller

Process

Multi Input Multi Output (MIMO) System

i. Power Amplification (Gain) Positioning of a large radar antenna by low-power

rotation of a knob

ii. Remote Control Robotic arm used to pick up radioactive materials

iii. Convenience of Input Form Changing room temperature by thermostat position

iv. Compensation for Disturbances Controlling antenna position in the presence of large

wind disturbance torque

i. Ancient Greece (1 to 300 BC) Water float regulation, water clock, automatic oil lamp

ii. Cornellis Drebbel (17th century) Temperature control

iii. James Watt (18th century) Flyball governor

iv. Late 19th to mid 20th century Modern control theory

The Vetruvian Man

i. Pancreas Regulates blood glucose level

ii. Adrenaline Automatically generated to increase the heart rate and

oxygen in times of flightiii. Eye

Follow moving objectiv. Hand

Pick up an object and place it at a predetermined location

v. Temperature Regulated temperature of 36°C to 37°C

Figure shows a schematic diagram of temperature control of an electric furnace. The temperature in the electric furnace is measured by a thermometer, which is analog device. The analog temperature is converted to a digital temperature by an A/D converter. The digital temperature is fed to a controller through an interface. This digital temperature is compared with the programmed input temperature, and if there is any error , the controller sends out a signal to the heater, through an interface, amplifier and relay to bring the furnace temperature to a desired value.

Car and Driver

Objective: To control direction and speed of car Outputs: Actual direction and speed of car Control inputs: Road markings and speed signs Disturbances: Road surface and grade, wind, obstacles Possible subsystems: The car alone, power steering

system, breaking system

Functional block diagram:

Time response:

Measurement, visual and tactile

Measurement, visual and tactile

Steering Mechanism

Steering Mechanism Automobil

eAutomobil

eDriverDriver

Desired

course of

travel

Actual course

of travel

Error+

-

Consider using a radar to measure distance and velocity to autonomously maintain distance between vehicles.

Automotive: Engine regulation, active suspension, anti-lock breaking system (ABS)

Steering of missiles, planes, aircraft and ships at sear.

Control used to regulate level, pressure and pressure of refinery vessel.

For steel rolling mills, the position of rolls is controlled by the thickness of the steel coming off the finishing line.

Coordinated control system for a boiler-generator.

Consider a three-axis control system for inspecting individual semiconducting wafers with a highly sensitive camera

i. CD Players The position of the laser spot in relation to the

microscopic pits in a CD is controlled.

ii. Air-Conditioning System Uses thermostat and controls room temperature.

i. System, plant or process To be controlled

ii. Actuators Converts the control signal to a power signal

iii. Sensors Provides measurement of the system output

iv. Reference input Represents the desired output

SensorSensor

Actuator

Actuator

ProcessProcessController

Controller

++

Set-point or

Reference input

Actual Outpu

t

ErrorControll

ed Signal

Disturbance

Manipulated

Variable

Feedback Signal

+

-

++

If the performance does not meet specifications, then iterate the configuration and actuator

Application: CD player, computer disk drive Requirement: Constant speed of rotation Open loop control system:

Block diagram representation:

Closed-loop control system:

Block diagram representation:

Goal of the system: Position the reader head in order to read data stored on a track.

Variables to control: Position of the reader head

Specification:

i. Speed of disk: 1800 rpm to 7200 rpm

ii. Distance head-disk: Less than 100nm

iii. Position accuracy: 1 µm

iv. Move the head from track ‘a’ to track ‘b’ within 50ms

System Configuration:

Control System Application Examples

PROBLEM: Describe the block diagram of a person playing a video game. Suppose that the input device is a joystick and the game is being played on a desktop computer.

Consider the inverted pendulum shown in Figure El. 13. Sketch the block diagram of a feedback control.

Unmanned aerial vehicles (UAVs) are being developed to operate in the air autonomously for long periods of time By autonomous, we mean that there is no interaction with human ground controllers. Sketch a block diagram of an autonomous UAV that is tasked for crop monitoring using aerial photography.The UAV must photograph and transmit the entire land area by flying a pre-specified trajectory as accurately as possible.

Future advanced commercial aircraft will be Enabled.This will allow the aircraft to take advantageof continuing improvements in computer power andnetwork growth. Aircraft can continuously communicatetheir location, speed, and critical health parametersto ground controllers, and gather and transmitlocal meteorological data. Sketch a block diagramshowing how the meteorological data from multipleaircraft can be transmitted to the ground, combinedusing ground-based powerful networked computersto create an accurate weather situational awareness,and then transmitted back to the aircraft for optimalrouting.

Describe the block diagram of the speed control system of a motorcycle with a human driver.

Modern automated highways are being implemented around the world. Consider two highway lanes merging into a single lane. Describe a feedback control System carried on the automobile trailing the lead automobile that ensures that the vehicles merge with a prescribed gap between the two vehicles.

Problem:

SOLUTION :

Chapter 1i. Nise N.S. (2004). Control System Engineering (4th

Ed), John Wiley & Sons.ii. Dorf R.C., Bishop R.H. (2001). Modern Control

Systems (9th Ed), Prentice Hall.