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Matlab programme -PID TUNING

Ultimate cycle methodStep-1After the process has reached steady state (at least approximately), eliminate the integral and derivative action by setting Td to zero and Ti  to the largest possible value. Step -2 Set   Kp  equal to a small value (e.g., 0.5). Step -3 Introduce a small, momentary set-point change so that the controlled variable moves away from the set point. Gradually increase Kp  in small increments until continuous cycle occurs. The term continuous cycling refers to a sustained oscillation with constant amplitude. The numerical value of Kp  that produces continuous cycling (for proportional-only control) is called the ultimate gain   Kcu. The period of corresponding sustained oscillation is referred to as ultimate period,  Tu. Step-4Calculate the PID controller settings using Ziegler-Nichols (Z-N) tuning relations in Table 1  Table 1 Controller setting based on the continuous cycling method Ziegler-Nichols (Z-N)Kp Ti Td P   0.5Kcu--PI   0.45KcuTu/1.2-PID   0.6KcuTu/2Tu/8 

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