Research On Obstacle Avoidance Path Planning Of 6-DOF Manipulator

At present,the use of robots is gradually penetrating into all aspects of industrial production,science and technology,military,medical and people's daily life.However,most of the robot products used in industrial production are still in the first or second generation,not only the automation level is not high,but also the accuracy is relatively low,and there are some security risks.With the in-depth research and application of robot vision,the path planning technology is becoming more and more important.Based on the six degree of freedom manipulator,this thesis analyzes the robot kinematics knowledge,collision detection technology,path planning algorithm,and designs a set of path planning scheme with superior performance.The main work of this paper is as follows:(1)The kinematics modeling of manipulator is studied.The improved D-H parameter method is used to establish the mechanical arm model,and the forward kinematics and inverse kinematics equations of the mechanical arm are analyzed and derived.In view of the existence of multiple inverse kinematics solutions,a group of relative optimal solutions are selected based on the principle of minimizing the sum of the changes of each joint angle.Taking the six-axis manipulator of IRB1410 as an example,the model of the manipulator is established by using the robotics toolbox in MATLAB simulation software,and the correctness of the forward and inverse kinematics solution equation is verified.Finally,the workspace of the manipulator is solved by Monte Carlo method.(2)A collision detection method using envelope box is designed.According to the characteristics of the body structure of the manipulator,the connecting rod is enveloped by a cylinder,and according to the specific shape of the obstacle,it is enveloped by a cylinder or a sphere.In order to further simplify the calculation process,the link of the manipulator is abstracted as a line segment,and its radius is superimposed on the geometry surrounding the obstacle.Collision detection is transformed into judging whether simple geometry intersects in space.(3)The path search algorithm is studied and improved.The principle of RRT algorithm and improved RRT connect algorithm and RRT*algorithm are analyzed.In order to compare their characteristics,these three algorithms are used for path planning simulation.In this thesis,based on the RRT*algorithm,the target gravity is added to expand the random tree towards the target point.In order to avoid local optimization,the idea of adaptive variable step size is added.In case of collision,the random sampling strategy is still used to expand,otherwise the target gravity strategy is used to expand the random tree.This method optimizes the time and length of the path,and the path search will not fall into the local optimum.(4)A set of obstacle avoidance path planning scheme for a 6-DOF manipulator is designed.In the MATLAB software,RRT*algorithm,RRT-connect algorithm and the improved RRT*algorithm are used in the path planning experiment of the manipulator.Finally,the simulation experiment is done in a computer simulation software robot studio,which is specially designed for ABB Robot,to verify the effectiveness and feasibility of the planned path.The experimental results show that the improved RRT*algorithm not only overcomes the high randomness of the basic RRT algorithm and RRT connect algorithm,but also improves the disadvantages of the RRT*algorithm,which has the advantages of time and path.