Research On The Motion Control Of Quadruped Robot With Active-Passive Variable Stiffness Flexible Joints

The quadruped robot has flexible form of motion and excellent ground adaptability,which has been a hot spot for robotics in recent years and has a broad application prospect.Due to the unknown and complex working environment,the traditional rigid quadruped robot performs poorly increasingly in buffering the impact force by ground and improving the energy utilization.The quadruped bionic-robot prototype with apVSJ(Active and Passive Variable Stiffness Joint),and the motion control strategy of adaptive stable walking of quadruped robot was studied aiming at improving the adaptive ability in unknown and complex environment.The main research contents and innovations in this paper are as follows:1.The model building of quadruped robot.The single leg with apVSJ was simplified and assumed,then the mathematical model is analyzed,and the dynamic equation of single leg was established by Lagrange method.The mathematical model of electric driving unit composed of DC servo motor,harmonic reducer,apVSJ and load was also established,and the output characteristics of the electric driving unit were analyzed by MATLAB.2.The study of motion control strategy.The trot gait is selected as the motion gait of the quadruped robot through the analysis of the gait of quadruped creatures in the nature.Referring to Raibert's control decoupling thought,a motion control strategy of quadruped robot moving in unknown and complex environment was designed,which adopts two independent motion control strategies of land phase and leap phase.The feasibility of the motion control strategy of the quadruped robot was verified by the joint simulation of Simulink-ADAMS.3.The building and experiment of the quadruped robot prototype.Firstly,the structure and working principle of apVSJ and the whole structure design of the prototype were studied.Then the experiment of apVSJ joint compliance and the quadruped prototype were carried out.The experimental results were analyzed in detail,which verified the variable stiffness and flexible output of apVSJ and the linear walking stability of the prototype.And the shortcomings of the design of the prototype and control strategy are corrected by analyzing the problems in the experiment.