In this paper, the tree structure genetic programming algorithm has been used to find the nonlinear model for the electro-hydraulic actuator. For this kind of electro-hydraulic actuator, some behaviors of the system are known but still the relation of these sub-functions–whole system- is not known due to high nonlinearities and compact model. | Journal of Automation and Control Engineering Vol. 3, No. 6, December 2015 System Identification Using Genetic Programming for Electro-Hydraulic Actuator Hamid Bamshad, Minsu Jegal, and Hyun Seok Yang Mechanical Department, Yonsei University, Seoul, South Korea Email: {hamidbamshad, jglupin,hsyang}@ Abstract—Hydraulic actuators have wide ranges of application in modern industry. Designing a robust controller for this kind of actuator is always a significant concern among engineers. Recently the new kind of compact electro-Hydraulic actuator developed which although it has many benefits. It associated with some problems as unknown highly nonlinear parameters. First step to design controller is a system identification. There are many algorithms and techniques to find an accurate model for the system. In this paper, the tree structure genetic programming algorithm has been used to find the nonlinear model for the electro-hydraulic actuator. For this kind of electro-hydraulic actuator, some behaviors of the system are known but still the relation of these sub-functions–whole system- is not known due to high nonlinearities and compact model. So, based on the abilities of genetic programming, this theory was selected for system identification. This system is considered as a multi-input, single-output system. There are some significant considerations for genetic operations such as selection, crossover, and mutation. The fitness function is defined based on the error between the model output and experimental data. After many runs and generations, the model for the system has been found which is well-matched with real data. model which is obtained by system identification. Moreover, system identification for complex systemalways associates with some difficulties [2] Hydraulic actuator is considered as a system with high level of nonlinearities, uncertainties, and time varying characteristics which cause some difficulties for system identification.[1] System
