chapter 1 introduction - jordan university of science...
TRANSCRIPT
Control and Automa-on
Chapter 1: Introduc1on
Reading Material: Chapter 1 in Dorf
Why to study “Control and Automa1on”?
• Essen1al for students pursuing degrees in many engineering disciplines (mechanical, electrical, structural, aerospace, biomedical, or chemical).
• Applica1ons include aircraG, robots, civil engineering structures, process control, …., etc.
• Has played a vital role in the advance of engineering and science.
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What is “Control”?
• System (plant, process): An interconnec1on of elements and devices for a desired purpose. (A System is anything with inputs and outputs)
• Control: Make the system behave as we desire. – The most common source of Control is Human.
• Control System: An interconnec1on of components forming a system configura1on that will provide a desired response.
• Imagine “control systems” around you!
o Room temperature control o Car driving o Voice volume control o Balance of bank account
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Process Input Output
What is “Automa1c Control”?
“Automa1on = Automa1c Control”
• In this class we focus on Automa'c Control.
• Not manual!
• Why do we need automa1c control?
o Convenient (room temperature, laundry machine)
o Dangerous (hot/cold places, space, bomb removal)
o Impossible for human (nanometer scale precision posi1oning, work inside the small space that human cannot enter, huge antennas control, elevator)
o It exists in nature. (human body temperature control)
o High efficiency (engine control)
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Example: laundry machine
A laundry machine washes clothes, by se]ng a program.
A laundry machine does not measure how clean the clothes become. Control without measuring devices (sensors) are called open-‐loop control.
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Laundry Machine
Program se]ng (Input)
Washed clothes (Output)
Open-‐loop Control Systems
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Controller Actuator Process Input Output
(Desired output)
An open-‐loop control system: u1lizes an actua1ng device to control the process directly without using feedback.
The Actuator is the mechanism by which the controller affects the input to the system.
Examples of Open-‐loop Control Systems
• Laundry Machine
• A Pop-‐up Toaster • Irriga1on Systems
• Conveyer belts
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Open-‐loop Control Systems
Advantages: • Simple construc1on and ease of maintenance. • There is no stability concern. • Convenient when output is hard to measure or measuring the
output precisely is economically not feasible. (For example, in the washer system, it would be quite expensive to provide a device to measure the quality of the washer's output, cleanliness of the clothes).
Disadvantages: • Disturbances and changes in calibra1on cause errors, and the
output may be different from what is desired. • Recalibra1on is necessary from 1me to 1me.
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Closed-‐loop Control System In this approach, an output variable to be controlled is measured, compared with the desired value and the error between the two is used to adjust the actual value. This means that the control ac1on is somehow dependent on the output.
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Feedback
Controller Actuator Process
Sensor
Desired output response
Actual output Error
_
Nega1ve feedback control system The Sensor is the mechanism by which the controller detects the outputs of the plant.
Closed-‐loop Control System Example 1: autopilot mechanism
Its purpose is to maintain a specified airplane heading, despite atmospheric changes. It performs this task by con1nuously measuring the actual airplane heading, and automa1cally adjus1ng the airplane control surfaces (rudder, ailerons, etc.) so as to bring the actual airplane heading into correspondence with the specified heading.
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Closed-‐loop Control System Example 2: Manual fluid level regula1on
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Closed-‐loop Control System Example 3: Car steering control system
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Closed-‐loop Control System Example 4: Antenna Azimuth
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Basic elements of control loop
The role of the controller is to make the output following the reference in a “sa1sfactory” manner even under disturbances.
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Noise
Feedback
Controller Actuator Process
Sensor
Desired output response
Actual output Error
_ +
+
Disturbance
Advantages of closed loop control systems: • Ability to reject external disturbances • Improve measurement noise aoenua1on.
Mul1variable Control System
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Mul1-‐loop Control System
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Feedback
Controller 1 Actuator Process
Sensor 1
Desired output response
Actual output
_
Sensor 2 Feedback
Loop 1
_ Controller 2
Loop 2
See Figure 1.5 in the textbook
History of Automa1c Control
• Egyp1an Water Clocks (1200BC)
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Ctesibius(220-‐285 BC)
History of Automa1c Control
• In 1769, Wao’s steam engine and flyballgovernor
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History of Automa1c Control
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See table 1.1 on page 31 of the textbook
Feedback
Controller Actuator Process
Sensor
Desired output response
Actual output Error
_
Course goals
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Mathema-cal model
Modeling
Controller Design
Implementa-on
Analysis
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Control System Design
Design Example: Rota1ng disk
22 Open-‐loop control system
The goal is to design a system for rota1ng disk speed control that will ensure that the actual speed of rota1on is within a specified percentage of the desired speed.
Design Example: Rota1ng disk
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Closed-‐loop control system
Design Example: Insulin delivery • Control goal: Design a system to regulate the blood sugar
concentra1on of a diabe1c by controlled dispensing of insulin.
• Variable to be controlled: Blood glucose concentra1on. • Control design specifica1on: Provide a blood glucose level for
the diabe1c that closely approximates (tracks) the glucose level of a healthy person.
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Design Example: Insulin delivery
25 (a) Open-‐loop (b) closed-‐loop control system