A Nonlinear PID Controller Based on an Adaptive Genetic Algorithm

The precision of temperature control is a very important factor to fermentation process. However, because the serious integral and time delay exists in the controlled object, the conventional control algorithm could hardly obtain satisfactory quality. Thus, a nonlinear PID controller is designed based on the nonlinear relationship between PID control parameters and error signals. Furthermore, an adaptive genetic algorithm is proposed in this paper in order to overcome the disadvantages in classical genetic algorithm, such as slow early convergence, local optimum, etc. The new adaptive algorithm adjusts the probabilities of crossover and mutation by construct function of the changes of fitness value. Simulation results show that the nonlinear PID controller with the GA for tuning the parameter is very effective. It has good dynamic and static response and strong robustness.