The Quadruped Robot Locomotion Control In Trotting Gait Based On Foothold Force Feedback

Quadruped robots can across the rough terrain steadily in high speed.Achieving the steady locomotion control is the precondition of these functions.In this paper we propose a control strategy for the quadruped robot in trotting gait based on contact force feedback.The passage decomposes the robot into a planar seven-link closed kinematic chain and a linear inverted pendulum through motion decomposition,which simplifies the robot model.The quadruped robot can achieve steady locomotion by force distribution of the supporting feet and the foothold of the swing feet.Firstly,this passage analysis the characteristic of the robot trotting gait detailedly and there are only two feet touch the floor during the robot locomotion without flying period.Thus the passage proposes that the quadruped robot can be decomposed into a planar seven-link closed kinematic chain in the direction of supporting line and a linear inverted pendulum in normal direction of supporting line.Secondly,according to the planar seven-link,configuration of hierarchical control is proposed.The controlling force of the robot body can be decomposed into the desired contact force of the supporting feet by force distribution which is described and deduced detailedly in the passage.The controllers of the body and the single leg are designed to achieve the 5 degree of freedoms of the robot controllable which are the robot height,3 postures and the velocity in supporting line.The another degree of freedom,the velocity in normal direction of supporting line can be controlled by the foothold of the swing feet proposed in the passage according to the linear inverted pendulum.Besides,the passage analyses the stability of the switch control.At last,the motion of the planar seven-link and the linear inverted pendulum compose the motion of the quadruped robot by composition theorem.The simulation model designed in the RecurDyn tests the availability of the control strategy by forward movement,sideways movement and turning movement.Then experiments are carried out which achieves the steadily step,forward and turning locomotion.The results verify that the quadruped robot can achieves steady locomotion with the control strategy proposed in this passage.