Automatic Control Systems PDF

Automatic Control Systems IE454 – Industrial Robots Lecture # 2 Dr. Majed Moosa Adapted from Emam Fathy 1  What is Control System? A system that Controlling the operation of another system. A system that can regulate itself and another syst...

Automatic Control Systems IE454 – Industrial Robots Lecture # 2 Dr. Majed Moosa Adapted from Emam Fathy 1  What is Control System? A system that Controlling the operation of another system. A system that can regulate itself and another system. A control System is a device, or set of devices to manage, command, direct or regulate the behaviour of other device(s) or system(s). 2  Definitions System – An interconnection of elements and devices for a desired purpose. Control System – An interconnection of components forming a system configuration that will provide a desired response. Process – The device, plant, or system under control. The input and output relationship represents the cause-and-effect relationship of the process. Input Process Output 3 Definitions Controlled Variable– It is the quantity or condition that is measured and Controlled. Normally controlled variable is the output of the control system. Manipulated Variable– It is the quantity of the condition that is varied by the controller so as to affect the value of controlled variable. Control – Control means measuring the value of controlled variable of the system and applying the manipulated variable to the system to correct or limit the deviation of the measured value from a desired value. 4  Examples lCar cruise control http://auto.howstuffworks.com/cruise-control3.htm Cables Electronically- controlled Vacuum actuator  Other examples Anti-lock braking system (ABS) – Major components of the typical ABS system four speed sensors (one at each wheel) electronic control unit (ABS computer) a hydraulic control unit http://www.samarins.com/glossary/abs.html  Other examples Vehicle suspension system – a system that will absorb the energy of the vertically accelerated wheel, allowing the frame and body to ride undisturbed while the wheels follow bumps in the road http://auto.howstuffworks.com/car-suspension.htm  Types of Control System Natural Control System – Universe – Human Body Manmade Control System – Vehicles – Aeroplanes 9  Types of Control System Manual Control Systems – Room Temperature regulation Via Electric Fan – Water Level Control Automatic Control System – Room Temperature regulation Via A.C – Human Body Temperature Control 10  Type of systems Control system configuration can be categorized into two: 1)Open-Loop Input Output Control System 2)Closed-Loop Input Output Control System  Types of Control System Open-Loop Control Systems Open-Loop Control Systems utilize a controller or control actuator to obtain the desired response. Output has no effect on the control action. In other words output is neither measured nor fed back. Input Output Controller Process Examples:- Washing Machine, Toaster, Electric Fan 12  Types of Control System Open-Loop Control Systems Since in open loop control systems reference input is not compared with measured output, for each reference input there is fixed operating condition. Therefore, the accuracy of the system depends on calibration. The performance of open loop system is severely affected by the presence of disturbances, or variation in operating/ environmental conditions. 13  Type of systems Open-loop system A generic open-loop system  Type of systems Open-loop system Advantage of Open-loop system Simple Cheap  Type of systems Open-loop system Disadvantage of Open-loop system Sensitive to Inability to correct disturbance for disturbance Solution Use closed-loop system  Types of Control System Closed-Loop Control Systems Closed-Loop Control Systems utilizes feedback to compare the actual output to the desired output response. Input Output Comparator Controller Process Measurement Examples:- Refrigerator, Iron 17  Types of Control System Feedback Control System A system that maintains a prescribed relationship between the output and some reference input by comparing them and using the difference (i.e. error) as a means of control is called a feedback control system. Input +- error Output Controller Process Feedback Feedback can be positive or negative. 18  Type of systems Closed-loop system A generic closed-loop system  Type of systems Closed-loop system Advantage of Closed-loop system Less sensitive to Transient response noise, disturbances and steady-state error and changes in can be controlled environment easily Transient response and steady-state error can be controlled by redesigning the controller. The process of redesigning is called compensating the system and the resulting hardware is a compensator  Type of systems Closed-loop system Disadvantage of Closed-loop system More complex More expensive  Type of systems Open loop vs. Closed-loop system How do we choose OL or CL? – Criticality of application The need to monitor output The need to control the output The need for reduced error or zero error Cost / budget Safety  Types of Control System Multivariable Control System Temp Outputs Humidity Comparator Controller Process Pressure Measurements 23  Types of Control System Servo System A Servo System (or servomechanism) is a feedback control system in which the output is some mechanical position, velocity or acceleration. Antenna Positioning System Modular Servo System (MS150) 24  Classification of Control Systems Control Systems Natural Man-made Manual Automatic Open-loop Closed-loop Non-linear linear Non-linear linear Time variant Time invariant Time variant Time invariant 32 Examples of Control Systems Water-level float regulator 33 Examples of Control Systems 34 Examples of Modern Control Systems 35 Examples of Modern Control Systems 36 End Of Lec 2 37