Tuning of pid controller
- 1. TUNING OF PID CONTROLLER Submitted by: SUBHANKAR SAU 1401216049 EEE Department Guided by:- Prof. P.K. Panigrahi(H.O.D) Prof. Siddheswar Kar Prof. Debasis Choudhury Prof. Sarat ku. Mishra
- 2. CONTENTS:- INTRODUCTION PID CONTROLLER TUNNING PROCESS DIFFERENT TUNING METHODS ZIEGLER-NICOLAS TUNNING METHOD CONCLUSION
- 3. I N T R O D U C T I O N : - The Controller: It decides the control variable in order to bring the process variable as close as to the set point. PID controller: It continuously calculates an error value e(t) as the difference between a desired set point and a measured process variable and applies a correction based on proportional ,integral and derivative terms which give their to controller types.
- 4. PID Controller:- Proportional Term(P): It is a constant directly related to the amount of the error. If you have large error ,the term gives you a large output, and if you have a small error, it will give you a small output. In simple term affects the speed to reach your target. Integral Term(I): It is constant related to integration(summation) of errors over time. If your error is increasing, this term gives you a large output. However if the error is decreasing, the I term give you a small output. Thus it is used to fine tune your results i.e. when you almost reach your goal, the P term can not serve you any more. Derivative Term(D): It is constant related to the rate of change of errors with time. i.e you have a highly dynamic systems like a multi-coptor, the D-term will give you higher output to catch up with the changes.
- 5. NEED OF PID CONTROLLER:- PARAMETER RISE TIME OVERSHOO T SETTLING TIME STEADY- STATE ERROR STABILITY Kp Decrease Increase Small Change Decrease Degrade Ki Decrease Increase Increase Eliminate Degrade Kd Minor Change Decrease Decrease No Effect Improve if Kd Small
- 7. TUNING PROCEDURES OF PID CONTROLLER:- 1) After nulling all the parameters ,increase the P term so that the output reaches the target in shortest possible time. 2) If your output starts oscillating ,it means you have too much P. lower your P term until the oscillation disappears. You will end up slightly higher or lower than your target. 3) Now increase I term slightly until your errors goes away. Note that usual I values are very small and they are dependent on the update rate of your PID loop. If you feel your output is oscillating lower your I term. 4) Now for highly dynamic system we need to adjust the D term also. 5) If your system starts oscillating with high frequency and small transition it means we have too much D term which is amplifying the noise. If it has too much noise its better to keep the D parameter to zero. 6) At last watch your limits . If you are changing the previous parameters without any noticeable change in the output This Completes the tuning procedure of the PID Controller.
- 9. TUNNING PROCESSES:- METHODS ADVANTAGES DISADVANTAGES Manual Tuning No Math Required, Online Requires Experienced Personnel Ziegler-Nichols Proven Method, Online Process Upset, Some Trial –and- Error, Very Aggressive Tuning Cohen-Coon Good Process Models Some Math; Offline; Only good for First- Order Process Software Tools Consistent Tuning; Online or Offline Some Cost Or Training Involved
- 10. ZIEGLER-NICHOLUS METHOD (OpenloopMethod):- It is done in manual mode. It is way of relating the process parameters(i.e Controller gain & Reset time). It has been developed for use on delay-followed by first-order-lag-processes. Once the value of process parameters are obtained the PID parameters can be calculated from the below table.
- 11. Process parameter(Delay time, Process gain PROCESS REACTION CURVE - SIMPLE
- 12. ZIEGLER-NICHOLUS METHOD (CloseloopMethod):-continue In controller automatic mode(operating condition), PV approximate to set point, change the %PB of controller to maximum, Integral time maximum and Derivative time minimum, then decrease %PB and take load step(change set-point or process loads) for monitor PV responding until PV occur slight oscillation. Record %PB of Oscillate condition(Ultimate controller gain ,Kcu) and Band width( ultimate period ,Pu).
- 13. ZIEGLER-NICHOLUS METHOD (closeloopMethod):-continue Then we roughly tune the initial value as the below table; Where Kc= Controller gain %PB= 1/Kc x 100(%) %PB=% Proportional Band Ti= Integral Time or Reset time (Sec./Repeat) Td= Derivative time or rate (Sec.)
- 14. CONCLUSION:- P Controller mitigates error but initiates offset. I Controller mitigates offset but initiates overshoot. D Controller mitigates overshoot for optimization.