Theory And Experimental Research On Stable Gait Of Quadruped Robot Based On Impedance Control

Existing transportation vehicles gradually show disadvantages when working on irregular terrain with the exploration of unknown environment. Researchers thus focus on the designing and manufacturing of this kind of robots resembling quadrupeds, which are capable of moving in natural environment. The research of quadruped robots has become a focus field, due to their excellence in moving on rough and soft ground comparing with wheeled vehicles. This paper focuses on the research of factors which affect walking stability of quadruped robot, including analysis of robot kinematics and stability, gait planning and contact force control.Analysis of robot kinematics is of vital importance to gait planning, motion parameter modification and walking control. In addition, robot control system requires satisfying online performance. Establishment of simple but effective kinematic model has great meaning in robot motion control. Thus, the thesis first analyses the kinematics of quadruped robot. In the meantime, the thesis estimates walking stability of quadruped robot in two aspects, which are COG(Center of Gravity) stability and body balance respectively. Equation of COP(Center of Pressure) coordinates, mechanical model of quadruped robot and an index to quantify robot stability are obtained in the thesis.Quadruped robots, as a bionic machine, should fit in with general laws of quadrupeds' motion. Through proper gait planning, the robot's moving ability and balance control ability can be improved. The thesis plans gait of quadruped robot with the goal of steadily walking, and simulates situations when the robot walks on plain and hard terrain with two different gaits. Moreover, differences on stability margin and movement compliance of the two gaits are compared.Beside stability margin, robot walking stability is related to contact force between robot foot and the environment. Besides, pure position control is not enough in compliance control. Hence it is necessary to study force control method when the robot is walking or running. This thesis uses impedance control method to control contact force of quadruped robot foot with the environment, and analyses the procedure under simulation study. An online and feasible controller is designed, which is robust to variable environment stiffness and sensor noise.The thesis also establishes experiment platform, including control system configuration and programming. The gait planned previously is proved effective and the control method feasible through experiment.