The Motion Coordination And Control Of The Canine-mimic Quadruped Robot With Compliant Spine

The quadruped mammal is the best blueprint for the research of the quadruped robot.Their flexible,compliant,stable gait motion not only benefits from the coordination motion of four legs,the spine also plays an important role in the gait motion.Adding the spine element is the important measure to further improve the flexibility and stability of the quadruped robot.However,adding the spine no doubt makes the robot system more complex.The robot system has the features of high dimensionality,variable topology,and strong nonlinearity and so on.Therefore,the motion coordination mechanism and control of the spine and the legs become one of the difficulties for the research of the quadruped robot.In order to reveal the motion coordination feature of the spinal joints and four legs and its effects on the motion performance,this paper regards the quadruped robot with compliant spine as the study object and concentrates on two problems of the motion coordination features and control to conduct the research.The main research thoughts and contents include the following points:(1)Put forward the hybrid dynamics model that is able to uniformly explain the quadruped motion with spinal joints,based on the analyses for the coordination features of canine.Firstly,start from the kinematic characteristics of the canine.The motion model with two spinal joints is obtained through the ayalyses for the coordination features of segment motion.Then,start from the dynamics model.The motion model is simplified based on the model of spring loaded inverted pendulum.According to the timing sequence feature of gait motion,the continuous dynamics equations are established,and the event judgement function and state updating function are defined.These make up the hybrid dynamics model for the quadruped motion with spinal joints.Finally,by the Poincare map and hybrid optimizing for the fixed point,the dynamics characteristic at the trotting gait is computed and analyzed,which indicates that the hybrid model has the bionic meaning for explaining the quadruped trotting motion with spinal joints.(2)Reveal the coordination feature of the spinal joints and four legs and its effects on the ground reaction force and motion stability.Firstly,regard the velocity as the operating variable.The uniformity of the motion coordination of the spinal joints at different velocities is analyzed.The presented motion coordination is similar to the motion of the spinal joints of canine.Then,through the stiffness analysis of the spinal joints and legs,the coordinated oscillation characteristic of the spinal joints and four legs is revealed.Finally,the compliant effect of the spine on the ground reaction force are explained by the comparison analyses between the quadruped robot with spine and rigid torso.The proposing hybrid control method based on the coordinated constrain indicates the effects of the motion coordination on the motion stability.(3)Propose the compliant control method of the quadruped robot with spine based on the thought of achieving motion coordination by the method of force synergy according to the shown coordinated oscillation characteristic in dynamics analyses achieving the trotting gait that possesses the coordination between spine and four limbs.Firstly,establish the virtual simulation environment for the quadruped robot and concentrate on studying the control characteristic of the control method.The improving effect of the coordination between the spine and four limbs on the motion compliance and stability is proven by the comparison research with the quadruped robot with rigid body.Then,the motion platform of the quadruped robot with spine is set up.The research of experiment not only verify the feasibility of the control method,but also further verify the effect of the coordination between the spine and four limbs on the motion compliance by the comparative experiment of different control methods.This doctoral dissertation reveals the motion coordination feature of the spinal joints and four legs and its effects on the motion compliance and stability through several aspects of research including the canine motion,dynamics model,motion simulation of virtual model and gait experiment.The research result is able to supply the theoretical direction and feasible control method for the extended application of the compliant spine in the quadruped robot,which has important theoretical significance and practical value.