Considerations on PID controller operation: Application to a continuous stirred tank reactor

This paper analyzes optimal controller settings for controllers with One-Degree-of-Freedom (1-DOF) Proportional-Integral-Derivative (PID) structure. The analysis is conducted from the point of view of the operating mode (either servo or regulation mode) of the control loop and tuning mode of the controller. Performance of the optimal tuning settings (ISE-like) can be degraded when the operating mode is different from the select one for tuning. An index for measuring the overall Performance Degradation is proposed and from the minimum of this, tradeoff tuning settings are given. The proposed procedure is applied to control a Continuous Stirred Tank Reactor (CSTR), which is a non-linear system.