Research On Structure Design And Foot Trajectory Planning Of Imitating Cheetah Quadruped Robots

The research of running quadruped robots has become one of the hotspots in quadruped robot research areas in recent years.Rigid quadruped robots have the disadvantage of slow running speed,inadequacy of movement stability and coordination.The flexible design of the leg structure and spine structure of quadruped robot can improve its movement performance.In this paper,imitating animal cheetah,the flexible structure design and foot trajectory planning for running quadruped robots are studied.The main contents are as follows:(1)Based on the analysis of the skeletal-muscle structure of the cheetah hind limb,the leg structure with cushion performance for quadruped robots is designed.Based on the analysis of the structure of the cheetah spine and its morphological changes during running,a simple spine structure with capable of up and down bending is designed.Adopting hydraulic cylinders as the drive mechanism,the quadruped robot with cushion leg structure and flexible spine is designed.(2)The kinematics and dynamics of the imitating cheetah quadruped robot are analyzed,and the expression of the joint angle is deduced.According to the arrangement position of hydraulic cylinder and the relationship between the hydraulic cylinder and other components,the relationship between the length of hip joint and knee joint hydraulic cylinder and the joint angle is obtained.(3)Based on the analysis of the retraction and backswing of the foot trajectory,when the cheetah runs,two kinds of foot trajectory are proposed:one is the improved ellipse foot trajectory,and the other is the modified cycloid foot trajectory.Based on the movement characteristics of the bound gait,two kinds of foot trajectories function expression are given detailedly.(4)Two kinds of designed foot trajectory are applied to the imitating cheetah quadruped robot,and simulation analysis is carried out.The simulation results show that the two kinds of foot trajectory can make the quadruped robot realize stable movement in the bound gait.Through comparative analysis,the modified cycloid foot trajectory is more suitable for running movement.