Software Engineering/Mechatronics 3DX4
Slides 1: Introduction
Dr. Ryan Leduc
Department of Computing and Software
McMaster University
Material based on lecture notes by P. Taylor and M. Lawford, and Control Systems Engineering by N. Nise.
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Overview
◮ What is a control system?
◮ Example control systems
◮ Terminology , Response characteristics, & Systemconfigurations
◮ Analysis and Design Objectives
◮ The Control Systems Design Process
◮ Case Study: Antenna Azimuth Control
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What is a Control System?
◮ In its simplest form a control system provides an output(response) for a given input (stimulus)
Figure 1.1: Simplified description of a control system
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Why do We Need Control Systems?
◮ Power amplification (e.g. power steering)
◮ Remote control (e.g. Telerobotic surgery, bomb disposalrobot, etc.)
◮ Convenience of input (e.g. Convert thermostat slider positionto room temperature)
◮ Compensation for disturbances
◮ Improve system speed, accuracy, repeatability, performance,etc., etc.
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Example Control Systems I
Figure 1.3
Rover was built to work incontaminated areas at ThreeMile Island in Middleton, PA,where a nuclear accidentoccurred in 1979. The remotecontrolled robots long arm canbe seen at the front of thevehicle.
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Example Control Systems II
Figure 1.4
(a) Video laser disc player.
(b) Objective lens reading pitson a laser disc.
(c) Optical path for playbackshowing tracking mirrorrotated by a controlsystem to keep the laserbeam positioned on thepits.
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Example Control Systems III
Figure 1.7
Computer hard disk drive,showing disks and read/writehead.
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System Configurations
Figure 1.6
Block diagrams ofcontrol systems:
(a) Open-loop system.
(b) Closed-loopsystem.
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Transient and Steady State Response
Figure 1.5: Elevator input and output
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Transient Response Tradeoffs
Figure 1.10
Response of a positioncontrol system showingeffect of high and lowcontroller gain on theoutput response.
Percent overshoot =a
b× 100%
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Stability
Total response = Natural response + Forced Response
◮ Natural Response (aka homogeneous solution): Evolution ofsystem due to initial conditions.
◮ Forced Response (aka particular solution): Evolution ofsystem due to input.
◮ Generally a system is stable if the natural response eventuallygoes to zero or at worst oscillates with some fixed amplitude.
◮ In an unstable system the natural response grows withoutbound, swamping the forced response and system is no longercontrolled.
ie a bounded input does not create a bounded output.
◮ In general, a control system must be stable to be useful.
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Control Objectives
1. Stabilize the system.
2. Produce the desired transient response.
3. Decrease/eliminate steady state error.
4. Make system robust to withstand disturbances and variationsin parameters.
5. Achieve optimal performance.
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Case study: Antenna Azimuth Position Control
Figure 1.8
The search for extraterrestriallife is being carried out withradio antennas like the onepictured here. A radio antennais an example of a system withposition controls.
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Azimuth Position Control System for Antenna
Figure 1.9
(a) Systemconcept
(b) Detailedlayout
(c) Schematic
(d) Functionalblock diagram
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How do You Design a Control System?
Figure 1.11: The control system design process
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Test Waveforms
◮ Test signals used toverify design.
◮ Table 1.1 shows thestandard test signalsused.
Table 1.1: Test waveforms used in control systemsc©2006-2012 R.J. Leduc 16