Introduction

iaa.ncku.edu.tw

Introduction

Text Book:

1. Feedback Control of Dynamic Systems (5th Ed)

Franklin, Powell and Emami-Naeini, Addison

Wesley

2002.

2. Modern Control Systems (10th Ed)

Dorf and Bishop, Addison Wesley

1998.

3. http://wwwcontrol.eng.cam.ac.uk/extras/Virtual_Library/Cont

rol_VL.html

4. http://en.wikipedia.org/wiki/Control_system


Introduction to Control Engineering

1.1 General system

A system is a collection of components which interact with each other

and with the environment (by information or energy links) from which

the system is separated by a notational boundary.

element

system

environment

Information link

system

boundary

Information link through

system boundary


• Process: the device, plant, or system under control.

• Sensor: a device to measure signal of interest

• Actuator: a device to amplify the control signal and to drive the plant.

1.2 Concept of control theory

• Control system

A control system is a system capable of monitoring and regulating the

operation of a process or a plant. The study of control system is

essentially a study of an important aspect of systems engineering and

its applications.

• Problem formulation

Determine a control law to stabilize the system and to achieve

asymptotic tracking and disturbance rejection.


Structure of a Feedback Control System

Disturbances &

uncertainties

Reference

signal

Reference

sensor

+

_

Controller

& actuator

Control

input

Plant

Output

Output

sensor


Watt’s Flyball Governor


(a) The F-18 aircraft, one

of the first production

military fighters to use

“fly-by-wire”

technology, and

(b) (b) the X-45 (UCAV)

unmanned aerial

vehicle. (Photographs

courtesy of

NASADryden Flight

Research Center.)


Radio

receiver

Missile

Amplifier

Actuating

signal

Control surface

motor drive

Missile

airframe

Missile

flight

path

Rate

gyro

Inner feedback

loop

Closed-loop control

system

Missile-tracking

radar

Command I/P

Radio

command

link

Computer

noise

disturbance I/P

Reference I/P

Target-tracking

radar


• Open-loop control

An open-loop control is applied to achieve desired system response

using a controller or an actuator without feedback.

• Closed-loop/feedback control

A closed-loop control is used to achieve desired system response using

a controller with the output measurement as a feedback signal. The use

of feedback enables us to improve system performance at the cost of

introducing the measurement noise and stability problem.

• Automation

The control of industrial process (manufacturing, production, etc.) by

automatic rather than manual means is called automation.

• Robust control

The system can be controlled by the controller in a desired manner, in

spite of the allowable disturbances and changes in the system

parameters.

• Intelligent control system

The system has capabilities of planing, scheduling, adaptation, and

learning.


History of Automatic Control

B.C.

•300 : water-level float regulator

A.D.

•1770s (Feedback control)

•1769 Jams Watt : steam engine (flyball governor)

•1868 J.C. Maxwell : stability analysis of dynamic system,

Cambridge University.

•1877 E.J. Routh : stability of high order system

•1907 A.M. Lyapunov : stability of equation of motion

(state space form Poincare’ 1892)

•1913 H. Ford : automation

•1927 H.W. Bode : feedback amplifier analysis (frequency

domain approach)


History of Automatic Control (Cont.)

• 1932 H. Nyquist: stability criterion for frequency domain approach

• 1936 Callender : PID controller

• 1948 W.R. Evens : the root locus approach

• 1949 frequency domain design criterion for SISO filter with

optimal statistical characteristics

• 1950s (Optimal control)

• 1952 MIT: NC machine

• 1954 robotic control

• 1956 Bellman : dynamic programming (USA)

• 1960 Kalman : MIMO problem

controllability & observability

• 1961 Kalman & Bucy : Kalman-Bucy filter


History of Automatic Control (Cont.)

• 1963 Pontryagin : maximum principle, time-optimal controller and

optimal controls for linear systems with a quadratic

cost function

• 1964 Kalman : design procedure for linear optimal control problem

with quadratic performance criterion(a feedback control

law could be obtained directly from the problem

specifications by the algebraic Riccati equation)

• 1964 Luenberger : state observer

• 1967 Wonham : relationship between the controllibility and pole

(eigenvalue) assignment by state feedback

• 1970s (Frequency domain design method for MIMO systems)

• 1969 Rosenbrock : inverse Nyquist array method

• 1970 MacFarlane : Characteristic locus method


History of Automatic Control (Cont.)

• 1976 Youla : stable factorization technique

• 1978 Doyle : robustness properties of LQR may be destroyed when an

observer is included in the feedback design

• 1983 Zames & Francis : H-infinity control theory

• 1984 Barmish : robust stability with structure physical parameter

perturbations

• 1986 M. Athans : LQG/LTR design method

• 1990s (Intelligent control)

• 1990 Astrom : Expert control

fuzzy control (Zadeh 1964)

neural networks

discrete event dynamic system control


Control engineering practice

• Control engineering is concerned with the analysis and design of goaloriented

(task-oriented) systems. Control systems are used to achieve 1)

increased productivity and 2) improved performance.

• Main tasks of control engineering

Modelling, Analysis, Design and Development.

• Population of control engineers

USA : 150,000 Europe : 150,000

Japan: 150,000 China : 200,000

• The future evolution of control system

(Fig. 1.3: Dorf and Bishop 8thEd Fig. 1.18)


Examples of control system

desired

behavior

comparison

decision

action

Process

measured

behavior

NT$/US$

desired

Chanceller

economy

NT$/US$

observed

desired

speed

governor

steam

engine

measured

speed

desired

aircraft

heading

movement

of control

surface

automatic

aircraft

pilot

measured

aircraft

deading


Variety of control engineering topics

Control Theory

and Its

Applications

Modelling & Identification

System identification

Bound graph method

Petri nets model

Linear Systems

Linear system theory

MIMO system

Robust Control

H-infinity control

LQG/LTR control

Real Time Control

Digital control system

Digital signal processing

Transputer/DSP-based

parallel processing

Applications

Flight control

Spacecraft control

Structure control

Process control

Nonlinear System Control

Variable structure control

Adaptive control

Intelligent Control

Expert system

Fuzzy control

Neural networks

Scheduling & optimisation

techniques

Filter Theory

Target Tracking

GPS

self-tuning control

Automation

Mobile control

Arm control

Manufacturing system control

Robotic control


Control system design

Engineering design is the main task of the engineer.

Specifications

The closed-loop control system performance specifications include:

1) good regulation against disturbance,

2) desirable responses to commands,

3) realistic actuator signal,

4) low sensitivity, and

5) robustness

The design is to achieve appropriate design specifications and rests on

four characteristics: complexity, tradeoffs, gaps and risk.


Design process

Establish control

goals

Select sensors

and actuators

Construct the

system model

Identify the

variable

to control and the

manipulating

variables

Determine the

performance

specifications

Simulation study

and validation

Select a controller

and adjust the

controller

parameters


Journals

AIAA Journal of Guidance, Control, and Dynamics.

Automatica.

Control Engineering Practice.

IEEE Control Systems Magazine.

IEEE Transactions on Automatic Control.

IEEE Transactions on Control Systems Technology.

International Journal of Control.

International Journal of Robust and Nonlinear Control.

Journal of Dynamic Systems, Measurement and Control.

Journal of Process Control.

Mechatronics.

SIAM Journal on Control and Optimization.

Systems and Control Letters.

Transactions of the Institute of Measurement and Control.

International Journal of Bifurcation and Chaos .

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