Control System Engineering by Engr Mark Joseph
- 1. CONTROL SYSTEMS ENGINEERING MODULE 1 ENGR. MARK JOSEPH B. ENOJAS
- 2. CONTROL SYSTEM Consists of subsystems and processes (plants) assembled for the purpose of obtaining a desired output with desired performance, given a specified input
- 3. EXAMPLES a. Early elevators were controlled by hand ropes or an elevator operator. Here, a rope is cut to demonstrate the safety brake, an innovation in early elevators; b. Modern Duo-lift elevators make their way up the Grande Arche in Paris, driven by one motor, with each car counterbalancing the other. Today, elevators are fully automatic, using control systems to regulate position and velocity.
- 4. MEASURES OF PERFORMANCE 1. Transient response 2. Steady state error
- 5. ADVANTAGES OF CONTROL SYSTEMS Power amplification Remote control Convenience of input form Compensation for disturbances
- 6. EXAMPLES Control systems are also useful in remote or dangerous locations. Rover was built to work in contaminated areas at Three Mile Island in Middleton, PA, where a nuclear accident occurred in 1979. The remote controlled robot’s long arm can be seen at the front of the vehicle. Control systems can also be used to provide convenience by changing the form of the input.
- 7. A BRIEF HISTORY Liquid level control – 300 B.C. Steam pressure and temperature control – 1681 by Denis Papin by a safety valve. Speed Control – 1745 by Edmund Lee in a windmill. Stability, stabilization, and steering – 1868 by James Clerk Maxwell, the stability criterion in third-order systems, 1874 by Edward John Routh, stability criterion in fifth-order systems. Twentieth-century developments Automatic steering wheel in 1922 used by Sperry Gyroscope Company Proportional-integral-derivative (PID) control by Nicholas Minorsky Feedback amplifiers by Bell Laboratories in early 1930s.
- 8. APPLICATIONS Guidance Navigation Ammunition Spacecraft Planes Ships at sea Manufacturing System automation
- 9. SYSTEM CONFIGURATION 1. Open loop 2. Closed loop
- 10. OPEN LOOP SYSTEMS Input transducer – converts the form of input to that used by the controller. Controller – drives a process or a plant. Input – reference Output – controlled variable Disturbances – undesired signals
- 11. DISADVANTAGES OF OPEN LOOP SYSTEM Cannot compensate for any disturbance that add to the controller’s driving signal. Do not correct disturbance and simply commanded by the input.
- 12. CLOSED-LOOP (FEEDBACK CONTROL) SYSTEM Input transducer – converts the form of input to the form used by the controller. Output transducer or sensor – measures the output response and converts it into the form used by the controller. Ex. Potentiometer (input transducer) and Thermistor,(output transducer) Actuating signal – difference between the input transducer and the output signal Unity gain – if there is no difference between the input and output signal. Error – common term for actuating signal.
- 13. ADVANTAGES OF CLOSED LOOP Compensates for disturbances by measuring the output response, feeding that measurement back through a feedback path, and comparing that response to the input at the summing junction. Greater accuracy than open-loop systems Less sensitive to noise, disturbances, and changes in the environment. Transient response and steady-state error can be controlled more conveniently and with greater flexibility often by a simple adjustment of gain (amplification) in the loop and sometimes by redesigning the controller.
- 14. DISADVANTAGE OF CLOSED LOOP SYSTEMS More complex and expensive than open-loop systems
- 15. ANALYSIS AND DESIGN OBJECTIVES Analysis is the process by which a system’s performance is determined. Ex. Evaluation of transient response and steady-state error to determine if they meet the desired specifications. Design is the process by which a system’s performance is created or changed. Ex. If a system’s transient response and steady-state error are analyzed and found not to meet the specifications, then we change parameters or add additional components to meet the specifications. A control system is dynamic: It responds to an input by undergoing a transient response before reaching a steady-state response that generally resembles the input.
- 16. MAJOR OBJECTIVES OF SYSTEMS ANALYSIS AND DESIGN Transient response Steady-state response Stability Total response=Natural response + Forced response Natural response describes the way the system dissipates or acquires energy. dependent only on the system, not the input. Forced response is dependent on the input.
- 17. NATURAL RESPONSE REQUIREMENTS 1. Eventually approach zero, thus leaving only the forced response 2. Oscillate. Instability happens when the natural response is so much greater than the forced response that the system is no longer controlled.
- 18. EXAMPLE: ANTENNA AZIMUTH POSITION CONTROL The purpose of this system is to have the azimuth angle output of the antenna, 𝜃0 𝑡 , follow the input angle of the potentiometer, 𝜃𝑖 𝑡 .
- 19. EXAMPLE: ANTENNA AZIMUTH POSITION CONTROL If the gain is increased, then for a given actuating signal, the motor will be driven harder. However, the motor will still stop when the actuating signal reaches zero, that is, when the output matches the input. The difference in the response, however, will be in the transients. Since the motor is driven harder, it turns faster toward its final position. Because of the increased speed, increased momentum could cause the motor to overshoot the final value and be forced by the system to return to the commanded position. Thus, the possibility exists for a transient response that consists of damped oscillations (that is, a sinusoidal response whose amplitude diminishes with time) about the steady-state value if the gain is high.
- 20. THE DESIGN PROCESS 1. Transform Requirements Into a Physical System 2. Draw a Functional Block Diagram 3. Create a Schematic 4. Develop a Mathematical Model (Block Diagram) 5. Reduce the Block Diagram 6. Analyze and Design
- 21. TEST WAVEFORMS USED IN CONTROL SYSTEMS Impulse - infinite at t . 0 and zero elsewhere. The area under the unit impulse is 1. Step input - a constant command, such as position, velocity, or acceleration. Typically, the step input command is of the same form as the output. Ramp input - represents a linearly increasing command. Sinusoidal inputs - used to test a physical system to arrive at a mathematical model.