Research On Motion Planning Of Six-axis Industrial Robot

Six-axis industrial robot is widely used in modern manufacturing industry,and it is a typical representative of industrial robot.Six-axis industrial robot is time-consuming to teach and unable to deal with the change of work scene,in order to solve these problems and enable six-axis robot to achieve autonomous planning in complex environment,motion planning of IRB 120 robot is studied in this paper.The work mainly includes kinematics,trajectory planning,collision detection and obstacle avoidance path planning.Firstly,kinematics of the robot is solved.D-H method is used to establish the kinematics model of the robot.The forward kinematics solution of the robot is obtained by homogeneous transformation.According to the structure characteristics of the robot,and based on algebraic method,the inverse kinematics of the robot is transformed from end point to wrist center.The approach of position and orientation separation is adopted to avoid inverse operation of the fourth-order matrices,and the inverse kinematics analytical solutions of the robot are obtained efficiently.Secondly,trajectory planning of the robot is studied.The quintic polynomial is used to complete point-to-point planning and multiple-points planning of the robot in joint space.The S-curve acceleration and deceleration algorithm is used to realize position interpolation of straight line,arc and mixed-curve as well as orientation interpolation in Cartesian space separately,in this way,trajectory planning of the robot in Cartesian space is completed.Then,collision detection of the robot is analyzed.In order to improve detection efficiency as well as ensure detection accuracy,the hierarchical bounding box method is used to simplify geometric model of the robot and obstacles.Based on the simplified models,collision avoidance conditions between the robot and obstacles are analyzed.Finally,obstacle avoidance path planning of the robot is studied.In this paper,an improved Rapidly-exploring Random Tree(RRT)algorithm is proposed.Expansion efficiency of the algorithm is greatly improved by introducing target-bias strategy and adding gravity component.Length of the path is shortened and smoothness of the path is improved through path optimization process.Based on the improved RRT algorithm,and considering collision avoidance between the robot and obstacles,path planning in Cartesian space is completed.Combined with trajectory planning,motion planning in task space is finally realized.