| In recent years, the legged robot which as a new type of high-tech product has beenplaying an increasingly important role in the field of military action, disaster relief andpolar exploration, and its research work has got wide attention at home and abroad. Withthe advantages of compact structure, large carrying capacity, good control performanceand big power-to-weight ratio, quadruped robot which drove by hydraulic power hasbecoming an important research direction. Due to the time-varying and nonlinearcharacteristics have great influence on the performance of hydraulic drive unit, it isdifficult to get good performance of quadruped robot. In order to get a deeper research, itis necessary to build a load simulation test bed with excellent performance. In this paper,aimed at the phenomenon of redundant force generation when the position disturbancedeliver to the load simulation system, how to restrain the redundant force and improve thesimulation accuracy are learned in this paper. This research can lay a foundation for thedesign of hydraulic drive unit and the study of control strategy.The specific research work are as followed:(1)The working principle of the load simulation test bed with displacement-forcedual channel is introduced. The mathematical model of system was derived by the methodof mechanism modeling and the influence factors to the output force of load simulationsystem are explored. Based on the simulation software AMESim and MATLAB/Simulink,the joint simulation model is built.(2)The working principle of speed synchronization control method is analyzed andthe expression of corresponding compensation link is derived. Through the simulation andexperimental research, the mathematical model and joint simulation model of loadsimulation system are verified.(3)The factors which result in the bad effect for restraining redundant force withspeed synchronization control method are analyzed. The reason is that the compensationlink, which is based on the linear mathematical model and ignore the influence oftime-varying characteristics, can not reflect the operating characteristics of actual drive unit accurately. In order to solve this problem, the pressure-flow nonlinear factors of servovalve are introduced into compensation control, then the parameter self-tuning method forrestraining redundant force is presented, and the nonlinear mathematical model ofcompensation link is built. Through the simulation and experimental research, it is provedthat the parameter self-tuning method can restrain redundant force effectively.(4)For the situation of position disturbance between position channel and forcechannel, from the view of improving the robustness of load simulation system, fuzzy PIDcontrol algorithm is introduced into the forward channel of load simulation system.Combined with the parameter self-tuning compensation control, this method is researchedthrough simulation analysis and experimental verification. The results show that thecombination of fuzzy PID control and parameter self-tuning compensation control canimprove the robustness of load simulation system, and optimize the restraining effect ofredundant force. |
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