Optimization of double loop control parameters for a variable displacement hydraulic motor by genetic algorithms

Abstract

The optimization of control gains for hydraulic servo systems is very difficult because of the high nonlinearities and uncertainties in the systems. In this paper, genetic algorithm is adopted to optimize the feedback gains for an over-centered variable displacement hydraulic motor (VDHM). The reciprocal of the ITAE criterion is proposed as the fitness function that evaluates the control performance. The appropriate specification of the genetic 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 10 generations, which corresponds to about 100 experiments. The optimal gains are also obtained when the inertia or the supply pressure is varied. Optimized feedback gains are confirmed by plotting the fitness function in a given gain space and it was verified that the genetic algorithm is an efficient scheme in optimizing feedback gains for hydraulic servo systems.