Research On Gait Planning And Impedance Control Of The Planar Hydraulic Biped Robot

Legged robot has its own characteristics of discontinuity with ground when walking which reduces its demands for the environment.Therefore it fits exploration,disaster etc.dangerous activities.Particularly,biped robot has a higher flexibility than quadruped and hexapod robots for its small supporting area,which unfortunately make it tumble easily.For realization of the gait planning and impedance control of the biped robot,this paper has carried out the following research.This paper introduces the planar hydraulic biped robot,describing its mechanical structure and driving system and analyzing its motion characteristics.The forward kinematics and inverse kinematics of the planner biped robot are derived and the decoupling of the kinematics is analyzed.Furthermore,we analyzed the link mechanism on each joints,deriving and fitting the polynomial about the displacement of hydraulic cylinders and joint angles.This paper proposes a dynamic gait planning method based on linear inverted pendulum model.The trajectory of COM(center of mass)of the robot is derived.What influence the parameters including step-size,height of COM and the initial velocity of COM of the walking biped robot have on the trajectory of the COM is analyzed.A mobile ZMP theory and double-support time is introduced to the gait planning.This paper implements the dynamic gait planning including starting,walking and stopping.This paper researches the impedance control of the biped robot.The impedance model of both the single joint and the leg are built.The realization of the impedance control of the biped robot is derived subsequently.A impedance control method without force sensor equipped on the end of the leg is proposed.A simulation of the biped robot is built in Adams and a walking episode including starting,walking and stopping is implemented.A position servo based impedance control single joint experiment is carried out which indicate a good compliant characteristics of the joint.Another set of experiments involves the performance of the proposed impedance controller of the hydraulic legged robot,demonstrating a desired compliant performance and reduction of the impact force.