Research On Motion Stability Of Quadruped Robot Based On Nonlinear Programming

Among mobile robots,legged robots have better adaptability and motion flexibility in the face of unknown terrain environments.In the case of legged robots,the quadruped has less structural redundancy and control factors compared to multi-legged robots.Therefore,quadruped robots have become the focus of research.The motion performance of a robot determines whether it can better cope with the challenges of various terrain environments,which plays a decisive role in realizing engineering applications.To make the quadruped robot show better motion stability and terrain adaptability,this topic investigates the motion planning and control algorithm of the quadruped robot in a senseless state,and discusses the quadruped robot motion model,stability motion planning,stability motion,and overall planning control under multiple spaces,and simulation analysis,including the following:(1)The motion model of the quadruped robot is designed,and its structure and motion parameters are described;The relationship between the position of the foot end and the angle of the single leg joint is deduced;Subsequently,the motion characteristics and stability of the quadruped robot are analyzed,and the Euler equations of the quadruped robot motion model are derived,which provide the theoretical basis for the following motion planning.(2)Firstly,a quadratic programming solution method is proposed to solve the desired landing point of each swing leg online by adding the motion reachability constraint;secondly,the solved landing point position is taken as the optimization input of the body trajectory and based on the stability criterion of ZMP(zero moment point),the equation and inequality constraint is introduced,and the walking and diagonal gait trajectories are planned online by minimizing the acceleration term of the Co M(center of mass)as the optimization solution objective.The trajectory of the body is planned online by minimizing the acceleration term of the Co M as the optimization objective.Finally,the planned motion trajectory is analyzed and verified,and the optimized improvement method of the body trajectory is proposed to further improve the stability of the quadruped robot motion and motion-following ability.(3)To adapt to the uneven terrain,firstly,the motion stability of the robot under multiple spaces is analyzed,and the continuity constraint and the Co M position constraint are introduced based on the sequential quadratic programming solver to plan the robot’s body motion trajectory under multiple spaces;Secondly,to simultaneously adjust the body posture to adapt to the terrain environment,the obtained foot-end touchdown position information was used to fit a spatial plane using the least squares method,and the fitted plane was used to derive the desired posture angle of the robot adapted to the current terrain.Finally,the entire gait planning of the quadruped robot uses a CPG(central pattern generator)with Bézier curves to generate foot-end swing phase trajectories,and PD feedback control is used to regulate the robot to achieve specific movements.(4)The combined simulation environment is built by MATLAB and ADAMS for virtual simulation experimental tests.The experiments include quadruped robot walking,motion planning under diagonal gait,motion planning under multi-space,motion planning after optimization and improvement,and motion planning method for uneven road surfaces.The simulation results show that the changing trend of the desired and actual value is consistent,and the robot can maintain stable and reliable motion.It shows the rationality and effectiveness of the motion planning control method proposed in this paper.