Fractional order control to the electro-hydraulic system in insulator fatigue test device

In this paper, a special composite hydraulic cylinder, which includes two pistons and three working chambers, is proposed for driving the insulator fatigue test device. In this force loading system, a servo valve and a proportional pressure valve are used to control the composite hydraulic cylinder to generate alternating force and fixed force respectively. Furthermore, the models of the electro-hydraulic system are built and its dynamic characteristic is analyzed based on the models. Considering the uncertainty of the model parameters, the fractional order proportional-integral-derivative controller is adopted to control the two valves. The Oustaloup method is used to discrete the fractional order controller and the iteration feedback tuning method is presented to tune the controller parameters. The tuning process which is independent on the system model can be done on the close loop system. Simulation and experimental results have shown that the fractional order controller is effective.