Design Of H_∞ Controller For Hydraulic Actuator Of Heavy-load Legged Robot Joint

Heavy-load legged robot with the ability of autonomous walking has draw significant attention with the promotion of robotics technology,computer intelligent control technology and signal detection and processing techniques in recent years.The performance of driving system for the heavy-load legged robot determines the its capability with load,endurance and the speed and the accuracy of dynamic response.So it has fatal significance for the heavy-load legged robot to researching the driving system with the characteristics of higher power-to-mass ratio,faster dynamic response and high energy efficiency.This paper aimed at the driving system for the heavy-load legged robot joint,a new direct drive volume control electro-hydraulic servo system was investigated.The driving system used the twin pump to control the differential and non-asymmetric hydraulic cylinder.The non-asymmetric hydraulic cylinder was of the similar motion characteristics either it moves forward or back.Based on the new direct drive volume control electro-hydraulic servo system, the work on control was presented.Firstly the principle of the driving system for the heavy-load legged robot joint was analyzed.System math model was built and simulation model was built based on Matlab/Simulink.Analyzed the influence which caused by the change of viscous friction coefficient and equivalent load.Based on the speed regulating system math model,its scale was reduced. Basedon the math model of system,the extendedH_∞ control was investigated. A loop transforming technique was introduced to solve the singularH_∞ control problem which caused by the integrator block of system math model. The appropriateweighting functions was selected. The extendedH_∞ controller was designed by the Matlab/Robust Toolbox.The PID controller was designed so that we can compared the performance of the PID controller with the extendedH_∞ controller.The performance of PID controller andH_∞ controller was analyzed by the software of Matlab/Simulink.To test the real performance of extendedH_∞ controller and PID controller, a software control scaffold was set up by using the XPC target module of Matlab. The chirp signal was input to the system and the system response signal wascompensated by the ramp signal.The open loop transfer functions of the driving system for the heavy-load legged robot joint was obtained based on system identification and the parameters of weight function was adjusted.The extendedH_∞ controller and the PID controller were re-designed for the hydraulic diving experimental system.Based on the experimental system of the driving system forthe heavy-load legged robot joint,The performance of PID controller andH_∞ controller was tested.