AUTOTUNING OF MULTILOOP PROPORTIONAL INTEGRAL CONTROLLERS USING RELAY FEEDBACK

In this paper, a simple method for autotuning multiloop PI controllers for multivariable systems is presented. The procedure is a combination of sequential loop closing and relay tuning often used for tuning single-loop PI/PID controllers. The proposed design offers three major advantages. Firstly, overall closed loop stability is guaranteed; secondly, very little knowledge of the process is required; thirdly, it is an autotuning procedure. Set point and load disturbance responses are improved by introducing set point weighting factors. Some simulation and comparative results are shown for distillation column models commonly used to demonstrate multiloop designs.