Disadvantages of the PID algorithm

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The PID algorithm has many advantages and is suitable for most industrial processes. However, for processes with high capacitance or integration, no matter which tuning method is used (self-tuning, internal model control, fuzzy control, or other artificial intelligence-based tuning methods), even if the PID parameters are theoretically optimal, the PID control algorithm has significant drawbacks: 1. Slow resistance to disturbances and large fluctuations ； 2. The rising speed should not be too fast, otherwise overshoot will occur ； 3. Long tuning time ； 4. After the controller output saturates, it takes a very long time to return to normal control ； 5. The control accuracy is not high at steady state; the controlled variable oscillates at a certain frequency, with the amplitude varying sometimes high and sometimes low ； 6. Poor adaptability: control performance deteriorates, or even worsens, when operating conditions and set values change. The chemical industry features many processes with high capacitance (such as sensor plate temperature) and integral processes (such as tower liquid level and tank pressure). Properly addressing the control issues of these processes greatly contributes to improving the degree of automation in chemical plants. Sometimes, in the face of severe disturbances, PID automatic control is not as fast as the manual adjustments made by experienced operators. I hope everyone can discuss how such control problems are addressed in chemical processing processes.