Research On Posture Balance Control Of The Quadruped Robot With Compliant Trunk

Quadruped robot has promising applications,which has been applied in military operation,outdoor detection,safety inspection,etc.Recently,many scholars are beginning to focus on the structure of spine.They have designed multiple spines of different structures and functions,in order to increase the walking speed,the energy efficiency and realizing dynamically stable gait such as trot gait.This article has designed a small quadruped robot with compliant trunk,and the three-DOF trunk is comprised of a yaw joint,a roll joint and a pitch joint.This article details the ZMP(zero)theory,proposes three models for quadruped robots,i.e.the rigid model,the multi-mass-point model and the single-mass-point model,and the ZMP solution for each model.Trot gait is very popular with regard to dynamical gait in quadrupeds.This article introduces two regular trot gaits,i.e.the generalized trot gait and the intermittent trot gait,and proposes the corresponding posture balance control strategy,which can be generally summarized into four steps,that is followed with establishing the single-mass-point model,designing ZMP trajectory,deducing COG trajectory based on ZMP equations,and planning COG position with side-swaying of the yaw joint.Different strategies are applied for this two trot gaits.Firstly,according to the strategy for the generalized trot gait,with a set of approximation calculations,the ZMP can be marked as the projection of COG on the ground.Then based on the principle of keeping ZMP within support polygon,the optimal solution of the yaw joint swaying function can be acquired which is formed as ?yaw(t)=Asin(?I+?/2).With regard to the scheme for the intermittent trot gait,the ZMP should be positioned in the diagonal line of support polygon,and then the COG trajectory can be derived from differential equation of the single-mass-point ZMP model.In the last,the swaying angular of yaw joint can be inversely deduced from the COG position.The abrupt position change of COG can be dealt with four-leg support phase.Virtual prototype model of the quadruped robot with compliant trunk is constructed by using ADAMS.For simulation experiments of postural balance control in the generalized trot gait,the illustrative example is set in T=1s and H=113mm.After applied with optimal swaying function of yaw joint,the path deviation can be descended from 36.97mm to 5.38mm and also the oscillation of the robot can be reduced from 46.06mm to 4.32mm,which implies that the degree of deduction is more than 80%.In the contrast,According to simulation experiments in the intermittent trot gait,the illustrative example is set in T=1.3s and H=113mm.After applied with optimal swaying function of yaw joint,the path deviation can be descended from 92.07mm to 24.68mm and also the oscillation of the robot can be reduced from 62.26mm to 8.61mm,which implies that the degree of deduction is more than 80%.These results validate the applied postural balance control strategies.