Research On Obstacle Avoidance Path Planning Of Auxiliary Robot For Machine Tools

With the development of robot technology and the proposal of "Made in China 2025" policy,manufacturing by robot-assisted CNC(computer numerical control)machine tools instead of human-assisted ones has shown great advantages,which makes industrial robots gradually become an important part of intelligent manufacturing field.However,the types of current auxiliary robots for CNC machine tools are mainly fixed ones,with only a single task and limited working space.Although problems mentioned above can be avoided by adopting an auxiliary robot with mobile manipulator structure for machine tools,such industrial robots are seldom applied.The reason is that the obstacle avoidance path planning of mobile manipulator has always been a key and difficult problem to address.Therefore,in this article,the auxiliary robot with mobile manipulator structure for CNC machine tools is taken as the research object and the obstacle avoidance path planning algorithm of it is mainly studied based on the CNC workshop environment.The main research contents are as follows:The structural scheme of the machine tool auxiliary robot is given,and its structural parameters are obtained.Firstly,the kinematics models of the two subsystems which are machine-assisted robot arm and the mobile platform are established respectively.Then the overall kinematics model of the auxiliary robot is analyzed,and the pose expression of the auxiliary robot in the WCS(world coordinate system)is obtained.The collision detection technology in the working process of the machine tool auxiliary robot is researched.According to the characteristics of the CNC workshop,the bounding box tree envelope model of the auxiliary robot and the CNC lathe is established,and the collision determination algorithm is obtained.The method is accurate and efficient,and lays the foundation for collision detection in subsequent path planning.The position of the mobile platform of the auxiliary robot for machine tools has a certain impact on whether the manipulator can complete tasks as well as the quality of tasks completed.Therefore,this article first solves the feasible region when the auxiliary robot for machine tools completes the tasks of work piece measurement,tool change and operating CNC panel.Plan the path of the manipulator subsystem by using RRT* algorithm and design the cost function of RRT* algorithm by taking the joint rotation angle of the manipulator as the motion evaluation index.With the optimization goal of minimum total displacement of the joint angle of the manipulator when it has completed three tasks,optimize the optimal position point in the feasible region of the mobile platform by combining with genetic algorithm.Furthermore,plan the path of the mobile platform subsystem according to the obtained optimal position point,and improve the algorithm based on the basic RRT(Rapidly-exploring Random Trees)algorithm so as to make it conform to the motion constraints of the mobile platform.Based on the GUIDE development environment of MATLAB software,complete the development of offline programming software for obstacle avoidance path planning of the auxiliary robot for CNC machine tools,and conduct simulation experiment through the auxiliary robot simulation system built by cooperating with the Recur Dyn software.Through the analysis of the experimental results,the feasibility and effectiveness of the obstacle avoidance path planning algorithm for the auxiliary robot in the CNC workshop environment are both verified.