Research On Obstacle Trajectory And Posture Planning Of 6-DOF Articulated Robot

A new generation of industrial robots usually efficiently operates in a dynamic environment.It is a key technology to handily avoid obstacles in trajectory planning and motion control.The trajectory planning aims to provide the desired input for robot motion control.A good planning can significantly improve the operating efficiency and smooth operation of robots,and reduce energy consumption.In this paper,the problem of space obstacle avoidance for a 6-DOF articulated robot designed by Yaskawa Shougang is focused on,and a multi-attribute cooperative trajectory optimization method is proposed based on the geometric obstacle avoidance method.The optimization objectives include the path length of the mission space,the total execution time,and the smoothness of the joint space trajectory.The constraints include obstacle avoidance,positions of the value point and velocity,acceleration,and jerk of each joint with upper bounds.The main research contents in this paper include:(1)Kinematics and dynamics models for the 6-DOF articulated robot are established.The closed solutions of the forward and inverse kinematics models of the Motoman MH50-35 robot are derived based on the D-H method.According to Matlab/RTB,a robot simulation model is established to verify several positions and postures.The kinematics equations are deduced based on the vector construction method,whereas the analytical solution of the inverse dynamics model for the joint space is derived based on Euler-Lagrangian equation.The numerical calculation and analysis of the parameters such as heavy torque,Coriolis matrix,and inertial matrix are performed to investigate the effect of such parameters on the driving torque of each joint.(2)The trajectory planning for the articulated robot is investigated.Linear and arc interpolation methods are investigated in the trajectory planning of the mission space.The uniform five B-spline curves are applied to the trajectory planning of the joint space.The explicit forms of five uniform B-spline curves are deduced,and the results obtained by non-uniform five B-spline curves is used to verify those obtained by uniform five B-spline curves.(3)The gesture interpolation algorithm based on the quaternion spherical meaning is deduced.The deficiencies of Euler angle interpolation and general rotation transformation interpolation are analyzed in the gesture interpolation.According to these deficiencies,the gesture interpolation method based on the quaternion spherical meaning is investigated.First,Two gestures and three gesture interpolation methods are elaborated.Then,it is extended to n gestures interpolation.Finally,the Euler method and SLERP interpolation are applied to verify this interpolation method based on Matlab/RTB.(4)A multi-attribute collaborative trajectory optimization method for the articulated robot including obstacle avoidance is proposed.First,the optimal path considering obstacle avoidance is obtained by the optimization in the mission space.After interpolating,the optimal path is converted to the joint space by the inverse kinematics equation.Finally,taking the smoothness of the trajectory and the shortest execution time as the objectives,the time series is optimized in the joint space by the genetic algorithm,then the optimal obstacle avoidance trajectory is obtained.