Foot-ground Contact Contour Curve Design Method of Close-chain Multi-legged Mobile System

Abstract：A foot-ground contact contour curve design method of close-chain multi-legged mobile system is proposed, which is used to compensate the vertical displacement fluctuation caused by the unadjustable leg -end trajectories of the close-chain mechanical legs, and to increase the walking speed and driving efficiency.Firstly, the movement characteristics of the crank driven mobile system is analyzed, and the functional relationship between the maximal effective step frequency and the vertical displacement fluctuation of the body is revealed.The vertical movement fluctuation of the body is identified as a key limitation of the walking speed.Secondly, the mathematical model of the mechanical leg is established and the kinematics is analyzed by solving the vector loop equations.The virtual fixed ground is built in the body reference frame, and with the rotary of the crank, the ground lines cluster in the lower leg reference frame is obtained based on the reversal method.The foot-ground contact contour curve is obtained by solving the envelope formed by the ground line cluster.Thirdly, the quadruped unit and the multi-legged mobile system is designed.The virtual prototype of the mobile system is built in ADAMS, and the vertical displacement fluctuation, the maximal speed and the power consumption are measured from the simulation results.Lastly, an experimental prototype is fabricated and tested.The flat ground walking speed experiment and the slope ground loaded experiment verify the effectiveness of the proposed foot -ground contact contour curve design method to increase the walking speed and driving efficiency.