Control system
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This document discusses different types of control systems, including open loop and closed loop systems. It describes open loop systems as having output that does not affect input quantity and lacks feedback, while closed loop systems have output that affects input and uses feedback to automatically correct variations in output. The document also covers servomotors, including AC and DC servomotors, and synchros which can be used to control angular position remotely or correct changes in position. Signal flow graphs are introduced as an alternative to block diagrams to represent systems.
Control system
- 1. CONTROL SYSTEMS Presented by P GODIESWARI M K GAYATHRI V GULSHAN R HARINI
- 2. system Number of element or components are connected in a sequence to perform the specific function Control system ➢ Output quantity is control by varying the input quantity ➢ A control system consisting of interconnected components is designed to achieve a desired purpose TYPE OF CONTRL SYSTEM ➢ Open loop system ➢ Closed loop system
- 3. Open loop system Output has no effect upon input quantity Not automatically correct the variation in its output Output not feedback to input for correction •Input •R(t) •Plant •Or system •Output •C(t)
- 4. Closed loop system ➢ Output has effect upon input quantity ➢ Automatically correct the variation in its output ➢ Output feedback to input for correction ➢ It is also called as automatic control system
- 5. Advantage ▪ Simple ▪ Economical ▪ Easy to construct ▪ stable open loop system
- 6. Disadvantage ▪ Inaccurate ▪ Unreliable ▪ Change in output due to external disturbances are not corrected automatically Open loop system
- 7. Advantage ▪ Accurate even the presence of nonlinearities ▪ sensitivity ▪ Stable ▪ Less affected by noise Closed loop system
- 8. Disadvantage ▪ complex ▪ costlier ▪ Reduce the gain of system more care to design a stable closed loop system Closed loop system
- 12. SERVOMOTORS
- 13. SERVOMOTORS ▪ WHAT IS SERVO MOTOR ? ▪ It is a special type of motor. ▪ Automatically operated up to certain limit for a given command. ▪ It uses error sensing feedback to correct the performance.
- 14. TYPES OF SERVO MOTORS AC SERVOMOTORS DC SERVOMOTORS AC SERVOMOTORS ❑ Induction motor with low (X/R) ratio. ❑ Consists of two main parts as follows, STATOR ❑ Two windings displaced by 90 degree. ▪ Reference winding constant AC supply. ▪ Control winding control voltage from servo amplifier.
- 15. ROTOR ✓ It is classified into two types as follows SQUIRREL CAGE ROTOR ✓ Use of aluminium reduces weight. ✓ Low inertia. ✓ Air gap is small. ✓ High resistance. DRAG CUP ROTOR ✓ Two air gaps. ✓ Used in low power applications. ✓ Made up of aluminium.
- 16. WORKING ▪ The voltage applied to stator creates RMF which makes rotor shaft to rotate. ▪ Torque-Speed characteristics. ✓ Linear for low (X/R) ratio. ✓ Non-linear for high (X/R) ratio. ▪ Linear characteristics depends on control voltage. ▪ It is operated in low speed range.
- 17. AC SERVO MOTOR FEATURES o Small (X/R) ratio & high efficiency. o Smooth, Less weight & low cost. o Robust construction & noise free working. APPLICATIONS OF AC SERVO MOTORS o Recorders,Computers and Robotics. DC SERVOMOTORS o It is classified as , o Electromagnetic field motor. o Permanent motor.
- 18. ELETROMAGNETIC FIELD MOTORS FIELD CONTROLLED MOTORS:- ▪ Field winding control signal. ▪ Armature winding constant current. FEATURES ▪ Large time constant. ▪ Open loop system. ▪ Preferred for smaller rate motors.
- 19. ARMATURE CONTROLLED DC SERVO MOTORS ▪ Armature winding control signal. ▪ Field winding constant current source. FEATURES ▪ Small time constant. ▪ Closed loop system. ▪ Preferred for large rate motors.
- 20. PERMANENT MAGNET MOTORS ▪ Field winding Permanent magnet. ▪ Armature winding voltage. FEATURES ▪ No field supply is required. ▪ Highly efficient. ▪ Less affected by temperature rise. ▪ Less heating.
- 21. SYNCHROS
- 22. Synchros Synchros is a name for a family of inductive devices which works on the principle of a rotating transformer. They can be used in following two ways 1. To control the angular position of load from a remote place. 2. For automatic correction of changes due to disturbance in the angular position of the load.
- 23. Synchro Transmitter ❑ When the rotor is excited by ac voltage, the rotor current flows, and a magnetic field is produced. ❑ The rotor magnetic field induces an emf in the stator coils by transformer action.
- 24. ❖ The input to the synchro transmitter is the angular position of its rotor shaft. ❖ By measuring and identifying the set of voltages at the stator terminal
- 25. Synchro control Transformer ➢The generated emf of the synchro is applied as input to the stator coils of control transformer. ➢ This emf can be measured used to drive a motor so that the position of the load is corrected.
- 26. Synchro as Error Detector ▪ The synchro error detector is formed by interconnection of a synchro transmitter and synchro control transformer. ▪ Initially the shafts of transmitter and control transformer are assumed to be in aligned position.
- 27. Synchro control transformer ▪ The null position of a control transformer in a servo system is that position of its rotor for which the output voltage on the rotor winding is zero
- 29. Signal Flow Graphs ▪ Alternative to block diagram; ▪ Consists only branches (systems), and nodes (signals)
- 30. How to convert a B.D to SFG
- 31. Mason’s Rule
- 32. Mason’s Rule - explained
- 33. Mason’s Rule - explained
- 34. Mason’s Rule - explained
- 35. Properties of signal flow graph ▪ Applicable to linear systems only. ▪ Algebraic equations in the form of cause and effect relationship. ▪ Node represents the variable or signal. ▪ Branch indicates functional dependence.
- 36. THANK YOU