PI controller tuning for multivariable processes using genetic algorithms

The paper presents an auto tuning method for the design of multi loop PI controllers, based on genetic algorithms. The powerful capabilities of genetic algorithms in locating the optimal (or near optimal) solution to a given optimisation problem are exploited by optimising the parameters of the PI controllers over specified performance objectives. Conventional tuning rules such as those proposed by J.G. Ziegler and N.B. Nichols (1942) are not used in this method, thus giving the designer the freedom to explicitly specify the required performance objectives for a given problem in terms of time domain bounds on the closed loop responses. Each set of controller parameters is directly evaluated by simulating the closed loop system and comparing the resulting responses with the desired responses using a specially formulated objective function, thus making the method applicable to virtually all classes of multivariable processes. Simulation results are presented to illustrate the effectiveness of the proposed method.