contlkhati-1

7/29/2019 contlKhati-1

1/72

1389

...

-


2/72

Introduction


3/72

Control

The word control is usually taken to mean :

- regulate,- direct,

- command .

3


4/72

Control system

A control system is an arrangement of

physical components connected or related

in such a manner as to command, direct, orregulate itself or another system.

4


5/72

5


6/72

Input

The input is the excitation or command

applied to a control system.

Typically from external energy source,

usually in order to produce a specified

response from the control system.

6


7/72

Output

The output is the actual response obtained

from a control system.

It may or may not be equal to specified

response implied by the input.

7


8/72

In Summary

Input - Excitation applied to a control systemfrom an external source.

Output - The response obtained from a system

Feedback - The output of a system that isreturned to modify the input.

Error - The difference between the reference

input and the output.

8


9/72

Disturbance in a feedback control

system

Disturbance signalis an unwanted extraneous

inputsignal that affects the systems outputsignal.

Feedback control can completely or partially

eliminate the effect of disturbance signal.

9


10/72

Negative Feedback Control System

CONTROLLER

CONTROLLED

DEVICE

FEEDBACK

ELEMENT

+ ++

-

10


11/72

Terms and Concepts

11


12/72

Control system

A control system is an interconnection of

components forming a system configuration that

will provide a desired system response.

12


13/72

Two Types of Control Systems

Open Loop

No feedback

Difficult to controloutput with accuracy

Closed Loop

Must have feedback

Must have sensor on output

Almost always negative

feedback

13


14/72

Open-loop control

An open-loop control system utilizes an actuating

device to control the process directly without using

feedback.

Must be closely monitored.

A common example of an open-loop control systemis an electric toaster in the kitchen.

14


15/72

15


16/72

16


17/72

17


18/72

Closed-loop control

A closed-loop control system uses a measurement of

the output and feedback of this signal to compare itwith the desired output.

Continually adjusts the process.

18


19/72

19


20/72

20


21/72

A person steering an automobile by

looking at the autos location on theroad and making the appropriate

adjustments.

21


22/72

22


23/72

Manual control system

Goal: Regulate the level of fluid by adjusting the output valve.

The input is a reference level of fluid and is memorized by operator.

The sensor is visual.Operator compares the actual level with the desired level and opens or

closes the valve ( actuator).

23


24/72

The level of fluid in a tank control.

24


25/72

The roles of feedback

Reduce error (eliminating the error)

Reduce sensitivity or Enhance robustness

Disturbance rejection or elimination

Improve dynamic performance or adjust thetransient response (such as reduce time

constant)

Benefits:

25


26/72

Major Types of Feedback Used

Position Feedback

Used when the output is a linear distance orangular measurement.

Rate & Acceleration Feedback Feeds back rate of motion or rate of change of

motion (acceleration)

Motion smoothing

Uses a electrical/mechanical device call anaccelerometer

26


27/72

Control systems are divided into two

classes:

a) If the aim is to maintain a physical variable at some fixed valuewhen there are disturbances, this is aregulator.

Example: speed-control system

b) The second class is the servomechanism.This is a controlsystem in which a physical variable is required to follow (track)

some desired time function.Example: an automatic aircraft landing system, or a robot armdesigned to follow a required path in space.


28/72

Multivariable control system

28


29/72

29


30/72

A robot is a computer-controlled

machine.

Industrial robotics is a particular

field of automation in which therobot is designed to substitute

for human labor.

The Honda P3 humanoid robot.

30


31/72

Automation- The control of a process by automaticmeans.

Closed-loop feedback control system-

A system that uses a measurement of the output andcompares it with the desired output.

31


32/72

Design-The process of conceiving or inventing the

forms, parts, and details of a system to achieve aspecified purpose.

Feedback signal -A measure of the output of thesystem used for feedback to control the system.

Multivariable control system -A system with morethan one input variable or more than one outputvariable.

32


33/72

Negative feedback -The output signal is fed back sothat it subtracts from the input signal. Negativefeedback initiates to maintain or regulate physiological functionswithin a set and narrow range.

Open-loop control system -A system that utilizes adevice to control the process without usingfeedback.

Optimization -The adjustment of the parameters toachieve the most favorable or advantageous design.

33


34/72

Positive feedback-The output signal is fed back so that

it adds to the input signal. Positive feedback mechanisms aredesigned to accelerate or enhance the output created by a stimulus thathas already been activated. In positive feedback systems the presence of aproduct (or signal) results in an increase in the production (amplification)

of that product (or signal).

Process-The device, plant, or system under control.

Productivity -The ratio of physical output to physicalinput of an industrial process.

34


35/72

Synthesis -The combining of separate elements or

devices to form a coherent whole.

System -An interconnection of elements and devices

for a desired purpose.

35


36/72

The Control System Design Process


37/72

Design is the process of conceiving or inventing

the forms, parts, and details of a system to

achieve a specified purpose.

Engineering design

37


38/72

Engineering design

Trade-off

The result of making a judgment about how to

compromise between conflicting criteria.

38


39/72

Control system engineers are concerned with

understanding and controlling segments of their

environment, often called systems, to provideuseful economic products.

39


40/72

Goals

Twin goals ofunderstanding and controlling are

complementary because effective systems

control requires that the systems beunderstood and modeled.

40


41/72

Control engineering

Control engineering is based on the

foundations of feedback theory and linear

system analysis, and it integrates the

concepts of network theory andcommunication theory.

41


42/72

Given a process, how to design a feedback

control system?

Three steps:

Modeling. Obtain mathematical description of the systems.

Analysis. Analyze the properties of the system.

Design. Given a plant, design a controller based on performance

specifications.

The course spans each of these steps in that sequence.

42


43/72

The basis for analysis of a system is the

foundation provided by linear system theory,

which assumes a cause-effect relationship for

the components of a system.

43


44/72

The design of control systems is a specific example ofengineering design.

The goal of control engineering design is to obtain the

configuration, specifications, and identification of the keyparameters of a proposed system to meet an actual need.

44


45/72

The design process consists of seven main building blocks, which

are arrange into three groups:

1. Establishment of goals and variables to be controlled, anddefinition of specifications against which to measure performance

2. System definition and modeling

3. Control system design and integrated system simulation and

analysis

45


46/72

46


47/72

Design 1

47


48/72

Design 2

48


49/72

Design 3

49


50/72

50


51/72

Design examples


52/72

Rotating disk speed control

52


53/72

Step 1. Control goal

Design a system that will held a rotating disk at a

constant speed. Ensure that the actual speed ofrotation is within a specified percentage of

desired speed.

53


54/72

Step 2. Variable to be controlled

Speed of rotation disc

54


55/72

Step 3. Control design specification

Design a system that will ensure that

the actual speed of rotation is within a

specified percentage of desired speed.

55

Step 4 Preliminary system configuration


56/72


56



57/72

p y y g

57


58/72

With precision components, we could expect

to reduce the error of the feedback system to

one-hundredth of error of the open-loop system.

58


59/72

Insulin delivery system


60/72

The blood glucose and insulin concentrations for a healthy person.

60


61/72

Step 1. Control goal

Design a system to regulate the blood sugar

concentration of a diabetic by controlleddispensing of insulin.

61


62/72

Step 2. Variable to be controlled

Blood glucose concentration

62


63/72

Step 3. Control design specification

Provide a blood glucose level for the diabetic

that closely approximates the glucose level of

a healthy person.

63

Step 4 Preliminary system configurations


64/72

Step 4 Preliminary system configurations

64


65/72

A drug-delivery system implanted in the body

uses an open-loop system, since miniaturized

glucose sensors are not yet available.

65


66/72

66

E 1: Controlling the position of a

missile launcher from a remotelocation

C t lli th iti f i il l h f


67/72

Controlling the position of a missile launcher from a

remote location

The input is the desired angular position of themissile launcher,

The control system consists:

of potentiometer,

power amplifier,

motor,

gearing between the motor and the missile launcher,

missile launcher.

67


68/72

A position open loop control

The input is the desired angular position of the missile launcher,

and the control system consists of potentiometer, power amplifier,motor, gearing between the motor and missile launcher, and missile

launcher.

68


69/72

A position closed loop control

Should an error exists, it is amplified and applied to a

motor drive which adjusts the output-shaft position until itagrees with the input-shaft position, and the error is zero.

69


70/72

Applications


71/72

Applications

Control engineering is not limited to any engineering

discipline but is equally applicable to:

aeronautical,chemical,

mechanical,

computer science and engineering ,

civil engineering,

electrical engineering.

71


72/72

Prerequisite by topics

Knowledge and proficiency in Matlab

Concept and solution of linear ordinary

differential equations

Laplace transform and its applications

Poles, zeros, transfer functions, frequency

response, Bode plots

Vectors and matrices

Complex numbers

contlkhati-1

Documents