Contro lsystem
- 2. Contents Open Loop Control Systems Closed Loop Control Systems
- 3. What is “controlling”? To cause a machine or process to function in a predetermined manner. To energize or de-energize an output To set a data table bits to on or off a machine, by a user program.
- 4. What is a Control System? A control system is a system of devices or set of devices, that manages, commands, directs or regulates the behaviour of other device or system to achieve desire results. A control system is a system, which controls other system. ProcessInput Output
- 5. Control System Open Loop Control System Close Loop Control System
- 6. Open Loop Control System Controller Process
- 7. A control system in which the output has no effect on the control action. Do not provide feedback of the actual state of the system. There is no comparing of output with the input for control purposes. The action is totally independent of output of the system.
- 8. Applications of Open Loop Control System Electric Hand Drier Automatic Washing Machine Bread Toaster Automatic Tea/Coffee Maker Timer Based Clothes Drier Light Switch Volume on Stereo System
- 9. Advantages Simple in construction and design. Economical. Easy to maintain. Generally stable. Convenient to use as output is difficult to measure.
- 10. Disadvantages Open loop control systems are inaccurate. These are not reliable. Any change in output cannot be corrected automatically. These are slow
- 11. Closed Loop Control System Controller Process Output Command Signal, Setpoint Measurement + - Error
- 12. Control system in which the output has an effect on the input quantity. A closed loop system is called a feedback control system. It provides feedback of the actual state and compare it to the desired state of the system. The input quantity will be adjusted based on the output generated to produce the desired output response.
- 13. Applications of Closed Loop Control System Automatic Electric Iron Servo Voltage Stabilizer Water Level Controller Missile Launched & Auto Tracked by Radar An Air Conditioner Cooling System in Car
- 14. Advantages This system is more reliable A number of variables can be handled simultaneously. Closed loop control systems are more accurate even in the presence of non-linearity. Highly accurate as any error arising is corrected due to presence of feedback signal. Bandwidth range is large. Facilitates automation. The sensitivity of system may be made small to make system more stable. This system is less affected by noise.
- 15. Disadvantages They are costlier. They are complicated to design. Required more maintenance. Feedback leads to oscillatory response. Overall gain is reduced due to presence of feedback. Stability is the major problem and more care is needed to design a stable closed loop system.
- 16. Requirement Of Good Control System Accuracy: error detector should be present in control system to increase accuracy Sensitivity : It should be sensitive to input signal only Noise : control system should be able tor reduce noise effect for better performance Stability: system must be able to remove offset Bandwidth: bandwidth should be large as possible for frequency response Speed : This is the time taken by control system to achieve its stable
- 17. Open Loop vs. Closed Loop Open loop control system Closed loop control system 1 The feedback element is absent The feedback element is always present 2 An error detector is not present An error detector is always present 3 It is stable one. It may become unstable 4 Easy to construct Complicated construction 5 It is an economical It is costly 6 Small bandwidth Large bandwidth 7 It is inaccurate It is accurate 8 Less maintenance More maintenance