Controllers ppt

In this side basic of Controller

1. Controllers Het Shah-190280109124 Kirtan Vora-190280109154 Keval Savsaviya-190280109123 L.D. College of engineering ahmedabad

2. Definition A devics or instruments used for achieving this is called as a controller In most Industrical process, it is necessary to control typical process variables such as temperature, Pressure, etc. at the referencs value called set points. Function To compare this value with a ref. set points value Calculate the error between the ref. set points and actual value Receives a signal corresponding to the quantity to be controlled To produce a control output signal proportional to the error in order to minimize the error

3. Block diagram

4. Classification of Controllers

5. Advantages They are Compact Fast in their resonse High reliability High accuracy Low installation cost Easy interfacing with computer, Data processing and data acquisition systems Disadvantages These are susceptible to fire risks

6. Analog Controllers All the analog electronic controller use a high gain OP-AMP as the building block The types of analog controllers includes P, I, D, as the basic ones. In addition we have PI, PID, PD controllers which are obtained by combining the basic types of controllers.

7. Proportional(P) Controller Concept In the P-type controller the output power is directly proportional to control error. The higher the proportion gain, the less the output power at the same control error. Circuit diagram Fig. shows the proportional controller which is an inverting amplifier using OP-AMP. Output voltage equ . where, = Output voltage = Input voltage  

8. Circuit diagram

9. As the gain is a constant, we can say that output voltage is proportional to the input voltage. Hence the name proportional controller. The gain of the amplifier is known as the proportional gain. The value of gain of the controller is modified by changing the values of Rf and Ri. The input voltage (Vi) to the controller is the error signal.

10. Advantages The main advantages of the P controllers is its fast speed of response. The change in output takes as soon as error is produced. Disadvantages Due to fast action sometimes the system can not come to steady state at all. That means the value of the parameter being controlled will keep fluctuating above and below its desired value

11. PI Controller Concept This is a combination of P an I controllers In this controller both P and I actions are combined together to obtain the advantages of both I and I controllers.

12. PI Controller The (P+I) controller is shown in fig. which is the practical inverting integrator circuit. and in fig. provide the proportional action whereas C and provide the integral action. The proportional gain is equal to and the integral action time is Corresponding to the negative step change in the controller input, a proportional positive step output change is observed, due to the proportional action. The integral action then causes the controller output to increase gradually The PI controllers are very popularly used in the speed control application of DC and AC motors.  

13. Circuit diagram

14. Advantages PI control provides zero control error and is insensitive to interference of the measurement channel. Disadvantages The main disadvantages of the PI controller is its below speed of response.

15. PID Controller Concept In a PID controller the output power is proportional to the sum of three coefficients: Proportional, Integral and differential. The PID controller is used in inertial systems with relatively low noise level of the measuring channel.

16. PID Controller The circuit diagram od a PID is shown in fig. Resistors and provide the P control. and provide the I control. Whereas and introduce the D control. The proportional gain is and integra time constant is differentitor time decided by The process of proper adjument of the three parameters The controller optimization is to be done by taking into account the parameters of the systems being controlled. PID controllers are used in various feedback controlled industrial systems.  

17. Circuit diagram

18. Advantages Fast response No overshoot or undershoot if properly optimized Ensure stable operation of the system being controlled Disadvantages Controller optimization needs to be done as per the system parameters Optimization process is little tricky Application Temperature control Pressure control Other industrial process

19. Temperature Control Using PID-Controller Circuit diagram Shows a control scheme for an automatic control of temp. using PID controller.

20. A thermocouple is used as temp. transducer. It produce a dc voltage to the actual temp. inside the oven. The feedback voltage from thermocouple is applied at the input of error amplifier, in series opposition with the set points voltage set by a potentiometer. The set points voltage represents the desired value of temp. The feedback voltages gets subtracted from the set points voltage and the difference between them which represents the error is applied to the error amplifier. The PID controller works on this amplified error voltage and produces a control voltage at this output. This voltage is applied to the pulse generator. The control voltage will change the firing angle of SCRs in this thyristor power circuit in such a way that the temp. error is reduced and the actual oven temp.is adjusted and maintained at the desired temp. leval