The Stable Motion Control Study On Quadruped Robot Based On The Flexible Joint With Actively Variable Stiffness

The quadruped robot based on flexible joint is got more and more attention in the field of quadruped robot research,because of its great advantages in buffering external shocks and energy consumption optimization in the process of motion.Aiming at some problem of quadruped robot based on flexible joint with fixed stiffness in the process of motion,this paper makes a research on the stable motion control about quadruped robot based on the flexible joint with actively variable stiffness.The adverse effect on the stable motion of the quadruped robot due to the existence of flexibility can be eliminated through the control strategy of this paper,simultaneously,the control strategy can also make the quadruped robot based on the flexible joint with actively variable stiffness has a better energy consumption compared with the quadruped robot based on flexible joint with fixed stiffness.Firstly,this paper establishes a simplified model of quadruped robot based on the flexible joint with actively variable stiffness,through the researches of kinematics analysis of quadruped robot?the method of parameter calibration of flexible joint with actively variable stiffness ? the method of dynamic identification about output torque estimate function based on the flexible joint with actively variable stiffness,lay the foundation for the stable motion control about quadruped robot based on the flexible joint with actively variable stiffness.Then,aiming at the problem of the oscillation which exists in the quadruped robot based on the flexible joint with actively variable stiffness motion of the swing phase,firstly,this paper make a analysis of the causes of oscillation in the motion.On the basis of a clear cause for the oscillation,this paper plans the control method of the flexible joint with actively variable stiffness,and makes a research on the generating method of foot trajectory of swing phase of quadruped robot.Finally,this paper analyze the stable control strategy of quadruped robot crawling on the uneven terrain and diagonal gait on a flat road which bases on adjusting the joint stiffness.In order to prevent the quadruped robot from producing the undesirable f uselage angle,the displacement offset of the foot ends of quadruped robot is controlled by adjusting the joint active variable stiffness coefficient,when the quantity of landing foot of quadruped robot changes in the crawl gait or the quadruped robot is in the process of stable motion.Through the analysis of energy storage of the flexible joints in the diagonal gait of quadruped robot,the target stiffness of joints is derived.So as to control the attitude angles of the body,adjustment strategy of body attitude angle based on adjusting the force of foot in the diagonal gait of quadruped robot is presented,the extra angle caused by the displacement offset of the foot ends is compensated in the process of control.To Applied the energy storage of the flexible joints into the movement which is beneficial to the stable motion or desired trajectory,the characteristics of releasing energy of joint flexible parts are analyzed by the means of numerical analysis under different joint stiffness in this paper.