OPTIMIZATION OF FEEDBACK GAINS FOR A HYDRAULIC SERVO SYSTEM BY GENETIC ALGORITHMS

The optimal values of the five feedback gains of a double-loop control ler for the speed control of an overcentred variable-displacement hydr aulic motor are experimentally determined by using genetic algorithms. The reciprocal of the criterion of integration of time multiplied by absolute error is proposed as the fitness function that evaluates the performance of the control. The appropriate specification of the genet ic algorithms and the search range of each control gain for the speed control system are presented. It is found that the near-optimal values of the feedback gains can be obtained within ten generations, which c orresponds to about 100 experiments. The optimal gains are also obtain ed when the inertia or the supply pressure is varied. Optimized feedba ck gains are confirmed by plotting the fitness function in a given gai n space. The fitness distribution indicates that finding the optimal f eedback gains by manual tuning is an extremely time-consuming task, an d that the genetic algorithm is an efficient scheme economizing time a nd labour, in optimizing feedback gains for hydraulic servo systems.