An improved hybrid suppression method for extraneous force of high-frequency electro-hydraulic loading system

Addressing the load simulating issue of the helicopter manipulation booster under high-frequency dynamic load to be superimposed on large static load, this paper has developed an electro-hydraulic loading system for this type of the load. The mathematical model of the electro-hydraulic loading system is firstly established. Then, a hybrid suppression scheme is proposed to eliminate the extraneous force. A constant compensating network is designed to decrease the extraneous force at first and then the double-loop cascade composition control strategy is applied to improve the tracking performance and furthermore to suppress the disturbance. The inner-loop controller is expected to make the plant track a nominal model approximately; and the outer-loop controller is expected to realize the desired force tracking performance. The disturbance observer based approach is adopted in inner-loop controller. The low pass filter Q(s) is designed by H_∞ mixed sensitivity optimization method. The simulation results show that the extraneous force is effectively suppressed using the proposed hybrid scheme, and meanwhile the robustness of the system can be also guaranteed.