Research On Path Planning And Turning Gait Of Hydraulic Quadruped Robot

Hydraulic quadruped robot is famous for its wide range of motion,adaptability to complex terrain and excellent power-weight ratio.In order to improve the motion flexibility of hydraulic quadruped robot in an environment with obstacle,this article was studied the structural model,forward and inverse kinematics and dynamics,path planning algorithms,turning motion realization method and foot trajectory of the quadruped robot.By analyzing the structural composition of the hydraulic quadruped robot,a simplified 3D simplified model and a D-H parameter model are created to analyze the functional relationship between the position and attitude of the robot body,the displacement and torque of each driving joint,and the functional relationship between the foot trajectory.By means of the given robot structural performance parameters,the limit position of each leg joint of the quadruped robot is calculated,and the single-leg working space is potted.Taking the right front leg of a quadruped robot as an example,the Lagrange’s dynamic equation is established to provide a theoretical basis for subsequent turning motion planning and motion simulation.By analyzing the problems of slow convergence speed,low search efficiency and easy access to obtain local optimum in the Ant Colony Optimization（ACO）,the state transition strategy is changed and the roulette wheel method is introduced to guide the initial population to select the path.The performance of the improved ACO in planning the path is simulated and analyzed in Matlab.Aiming at the problems of poor practicability of road conditions and poor smoothness of road bending in the path,the Genetic Algorithm（GA）is proposed to optimize the optimal solution set obtained by the improved ACO.The probability selection strategy of the ACO ensures that the algorithm can find the optimal solution to the problem and act as the initial population of the GA;in the later stage,the GA is used to optimize and improve the quality of the local optimal solution obtained by the ACO to avoid falling into the local optimal solution.excellent.Finally,through the Matlab simulation results,it can be seen that the path planned by the GA-ACO algorithm is obvious improved compared to the improved ACO in terms of optimal length,the number of convergence iterations and the path stability.By analyzing the turning motion of the existing quadruped robot,a turning method based on the step size difference of the foot trajectory of the left and right legs of the quadruped robot are selected,that is,by adjusting the step size of the foot trajectory of the robot,the differential motion of the legs on both sides of the robot is formed,so as to realize the robot turning motion.According to the turning requirements of quadruped robot,an octagonal polynomial foot trajectory curve with stable motion and smooth trajectory is designed.The factors affecting the stability and the conditions for stable movement of the quadruped robot in the process of turning movement are analyzed.By calculating the pressure center coordinate system of the quadruped robot on the support surface,it can be seen that the influence of its own mass,the height of the center of gravity and the external force on the motion stability of the robot can be seen.Then,the shortest distance between the projection point of the center of gravity of the quadruped robot on the foot support surface and the polygon boundary formed by the foot supports point is used to determine the stability of the quadruped robot in the process of turning movement.Using Adams and Matlab cosimulation and hydraulic experimental platform,the changes of pitch angle,roll angle and yaw angle of the fuselage during turning movement are analyzed,and the effectiveness of the turning strategy is verified.