Analysis Of Slope Walking And Turning Of Quadruped Robots Based On Leg Length Adjustment

Quadruped robots walking in rough terrains have the shortcomings of insufficient stability and flexibility which hinder the application in real life.When a quadruped robot moves on the slope,it needs to adjust its centroid to improve stability.When it do turning,it's necessary to avoid complex foot trajectory planning in order to improve motion coordination.Therefore,higher requirement for the structure design,motion planning and foot trajectory of the quadruped robot are put forward.In this paper,our research include the structure design,motion analysis,centroid adjustment on the slope,turning method and foot trajectory planning of the quadruped robot.The details are as follows:(1)A quadruped robot model with variable leg length is designed.The shank of the robot is a hydraulic cylinder,and by changing the length of the piston rod of the hydraulic cylinder to change the length of the shank;Then,the forward kinematics and inverse kinematics of the quadruped robot model are analyzed,and the formula for the joint angle is derived;Finally,the displacement function of driving each joint hydraulic cylinder is deduced according to the joint angle.(2)The stability of the quadruped robot moving on the slope is analyzed,and a new method is proposed to adjust the centroid.The method is increasing the length of the hind legs and reducing the length of the front legs,and then using the ADAMS and MATLAB simulation to verify the validity of the method.(3)This paper also analyzes the turning motion of the quadruped robot,and proposes a new method of turning.That is shortening the leg length of the same side and keeping the leg length of the other side no change.Then the motion trajectory and the force of the foot are analyzed through the coordinated simulation.(4)In this paper,a low impact foot trajectory curve is designed.The x and y curve functions of the foot trajectories are obtained by solving the constants in the sine function.And it is converted to adapt to the method of adjusting the centroid on the slope and the method of turning.The simulation results verify the rationality of the foot trajectory.