Chapter 1 – Overview of Control System

Eddy Irwan Shah Bin SaadonDept. of Electrical EngineeringPPD, UTHMeddy@uthm.edu.my019-7017679

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Outline: Introduction Control System Concept Type of Control System Control System Classification Control System Design

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1. Intro – Objective

After completing this chapter, student will be able to :

Define the basic features and configurations of control systems

Describe the open/closed-loop control system Learn control system applications Describe a general process for designing a

control system

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2. Control System Concept

What is Control System? A system that provides an output or

response for a given input

Can you give an example?

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2.1 What is System?

Definition: A combination of components or subsystems that act together and perform a certain objectives.

Systems interact with their environment across a separating boundary.

The interaction is defined in terms of variables. System inputs System outputs Environmental disturbance

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Block Diagram

ElectricalHydraulic Pneumatic Mechanical

2.2 Control System Component

Definition:

An interconnection of COMPONENTS forming a system

configuration that will provide a desired system

response

Mathematical Model

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2.3 General Block Diagram of Control System

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2.4 Terms of block diagram

Input: desired response Output: actual response Controlled variable: The quantity or condition that is measured and

controlled (normally in the output) Manipulated Variable: The quantity or condition that is varied by the

controller to adjust the controlled variable. Disturbance: Signal that affect the value of the output. Controller: Measuring the controlled variable and applying the

manipulated variable to correct deviation of the measured value (output) from a desired value (input).

Summing Junction/Point: to represent addition / subtraction of signals: Incoming signal lines either a “+” (addition) or “-” (subtraction) sign. Output signal is shown with an outgoing arrow.

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3. Type of Control System

The control system can be described into two configuration:

OPEN LOOP and CLOSED-LOOP

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Open loop system

AMPLIFIER

Power Supply High

power

+V

-V

0V

Input signal

Low power

MOTOR

GEARS

O

Output response

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Closed-loop system

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Advantage and Disadvantage of Open Loop System

Advantages Disadvantages1. Stability not a major

problem2. Cheaper than closed

loop system3. Can be used even if

output cannot be measured

4. Easier to maintain

1. Changes in system or disturbance cause errors

2. No longer accurate when the system is disturb. Needs calibration to maintain accuracy (Periodic calibration is required)

3. Low bandwidth – slow response

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Advantage and Disadvantage of Closed Loop System

Advantages Disadvantages1. Reduced sensitivity to disturbances

inputs and parameter changes.2. Can stabilize an open-loop unstable

plant.3. Can change system dynamics speed

of response, accuracy, reduce effects of nonlinearities

4. Highly accurate due to corrective actions

5. High bandwidth – fast response

1. More complex (Increased complexity and cost)

2. Risk of instability (stability is major problem)

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Feedback and its effect

Feedback system is a system that maintains a relationship between the output and some reference input by comparing them and using the difference as a means of control.

Feedback is used to reduce the error between reference and the system output.

The feedback has effects on performance characteristics as Stability overall gain noise (external disturbance).

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Feedback and its effect (cont)

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

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4. Control System Classification

Single input single output (SISO) Multiple input multiple output (MIMO) Linear Non-linear Time-variant Time-invariant Analog Digital Process Control Sequential Control

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5. Control System Design

6 Steps

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Summary of today’s lesson?

You have learn: The definition of control system. The components of control system. Block diagram. Type of control system. How to design a control system.

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Activity # 1 (1 hour)

1. Form a group of 5 persons.2. Select one sector from the list on the next slide.3. According to the design steps, describe the system

operation.4. You are not designing the system but you are doing

‘reverse engineering’.5. Explain you work in 10 minutes presentation on the

next class.6. A tutorial class next Friday is for a discussion for this

activity.7. This activity carries 5% of your total marks.

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