ME-314- Control Engineering - Week 01
- 1. ME-314 Control Engineering Dr. Bilal A. Siddiqui Mechanical Engineering DHA Suffa University and Brian Douglas
- 2. About the Course • This course teaches the basics of system modeling and control system design – Basic Concepts – Mathematical modeling of physical systems – System response to common inputs – Stability concepts – Control systems design • Root locus design • Frequency response design • State space design and Brian Douglas
- 3. Books and References • Katsuhiko Ogata-Modern Control Engineering-Prentice Hall (2001) • Farid Golnaraghi, Benjamin C. Kuo-Automatic Control Systems-Wiley (2009) • Norman S. Nise-Control Systems Engineering, 6th Edition-John Wiley (2010) • Richard C. Dorf, Robert H. Bishop - Modern Control Systems-PRENTICE HALL (2010) • Fracis Raven – Automatic Control Engineering – McGraw Hill (1961) • Brian Douglas - The Fundamentals of Control Theory – Online (current) • Brian Douglas lectures of control systems https://www.youtube.com/user/ControlLecture and Brian Douglas
- 4. Introduction System – Interconnected parts that form a larger more complex whole. It does “something”: basically we want to control that something. Control System – Another system (interconnected components) which is designed to change the behavior or performance of the system we want to “control”. It is confusing to refer to both “the system” and “control system”, so we generally call “the system” as “plant” or “process” and Brian Douglas
- 5. Introduction Multivariable Control System Open-Loop Control Systems utilize a controller or control actuator to obtain the desired response. Closed-Loop Control Systems utilizes feedback to compare the actual output to the desired output response.
- 6. The Control Problem • Any system has at least three parts: Inputs, Outputs, the system itself. The problem is one of these three is unknown. – System Identification: – Simulation Problem – Control System Design
- 7. Nomenclature of Control Systems
- 8. Disturbances • Sometimes, uncontrolled inputs (called disturbances) also affect the plant/process. • There is no way to correct output in open loop • Control system is ‘robust’ if it can mitigate them
- 9. Noise • All sensors are also affected by measurement noise (remember ME-313 Meas. & Instr). • Output in this case is not disturbed in the open loop • Control system is ‘robust’ if it can mitigate noise sensor noise
- 10. Plant / Model Mismatch • We can seldom mathematically model systems accurately • This means the plant will behave differently from predictions based on its “model” • Controller applies inputs based on the plant model model model
- 11. Advantages of Feedback • There is no need to use feedback (close loop) control and we can use open loop control, if – The model is perfectly accurate – There is no measurement noise – There is no disturbance • But none of the above is possible practically. • Therefore, feedback is the only available mechanism to achieve desired performance. • Closed-loop systems have greater accuracy than open-loop systems. • Less sensitive to noise, disturbances, & changes in environment. • Transient response and steady-state error can be controlled more conveniently and with greater flexibility • Some plants/processes are unstable or not stable to the degree we want • Control systems can make unstable systems stable
- 12. Disadvantages • Sometimes, the plant itself may be stable, but an aggressive control system can make it unstable. • Closed-loop systems are more complex and expensive than open-loop systems. – Modern digital control systems contain a lot of subsystems: microcontrollers, analog-digital converters, actuators etc. – Sensors and actuators can be very expensive • Therefore, – Must consider the trade-off between simplicity and low cost of an open-loop system vs accuracy and higher cost of a closed-loop system – Control system must be carefully tuned • Plant degrades over time, so control system needs to be recalibrated periodically.
- 13. System Response • Take the example of a building elevator (Nise) – 4th floor button is pressed on the 1st floor – Elevator rises with a speed and floor-leveling accuracy designed for passenger comfort. – Push of 4th -floor button is an input that represents our desired output Norman S. Nise-Control Systems Engineering, 6th Edition-John Wiley (2010)
- 14. Transient and Steady State Response • Two major measures of performance are – transient response – steady-state error • Passenger comfort and passenger patience are dependent upon the transient response. • If this response is too fast, passenger comfort is sacrificed; if too slow, passenger patience is sacrificed. • Steady-state error : passenger safety and convenience would be sacrificed if the elevator did not properly level. Norman S. Nise-Control Systems Engineering, 6th Edition-John Wiley (2010)
- 15. Stability • Transient and steady response are useless if the plant is unstable • Two types of stability: static and dynamic • Static: tendency to come back to equilibrium point • Dynamic: each oscillation has smaller amplitude than previous • Control systems must be designed to be stable.
- 16. Control System Design Cycle (Dorf)
- 17. Case Study: Antenna Position Control • Extraterrestrial life is being searched with help of huge antennas. We want to make a control system which automatically points the antenna in the direction (azimuth) we want. (Nise)
- 18. Layout of Antenna Azimuth Control • Azimuth angle can be measured by a simple n-turn potentiometer (how?) • Another potentiometer can be used to give the desired angle (how?) • Gearbox can be used to amplify the torque (how?) • Differential amplifier can be used as a comparator. • Motor is used as actuator. • Where is the controller?
- 19. Schematic of Antenna Azimuth Control
- 20. Block Diagram of Antenna Azimuth Control
- 21. Response of Antenna Azimuth Control System • Look at affect of controller (power amplifier) gain
- 22. Another Look at the Design Process
- 23. History (Dorf) Watt’s Flyball Governor (18th century) Greece (BC) – Float regulator mechanism Holland (16th Century)– Temperature regulator Heron of Greece’s water clock (3rd century BC)
- 25. History 18th Century James Watt’s centrifugal governor for the speed control of a steam engine. 1920s Minorsky worked on automatic controllers for steering ships. 1930s Nyquist developed a method for analyzing the stability of controlled systems 1940s Frequency response methods made it possible to design linear closed-loop control systems 1950s Root-locus method due to Evans was fully developed 1960s State space methods, optimal control, adaptive control and 1980s Learning controls are begun to investigated and developed. Present and on-going research fields. Recent application of modern control theory includes such non-engineering systems such as biological, biomedical, economic and socio-economic systems ???????????????????????????????????
- 26. (a) Automobile steering control system. (b) The driver uses the difference between the actual and the desired direction of travel to generate a controlled adjustment of the steering wheel. (c) Typical direction- of-travel response. Examples of Modern Control Systems
- 27. Examples of Modern Control Systems
- 28. Examples of Modern Control Systems
- 29. Examples of Modern Control Systems
- 30. Examples of Modern Control Systems
- 31. Examples of Modern Control Systems
- 32. The Future of Control Systems
- 33. The Future of Control Systems
- 34. Design Example
- 35. Design Example
- 36. Design Example
- 37. Design Example
- 40. Design Example
- 41. Design Example