Research On Trajectory Planning And Grinding Force Control Of Robotic Belt Grinding System

Through the robot belt grinding system,it is not only necessary to generate an efficient grinding trajectory,but also to ensure the dimensional accuracy and surface quality of the workpiece.Therefore,it is very important to study all aspects of the robot belt grinding system.In this thesis,aiming at the robot belt grinding system,the robot belt grinding trajectory planning and optimization,trajectory compensation,grinding constant force control are studied.At the same time,the feasibility of the algorithm is realized and verified by building the corresponding experimental platform.To generate the grinding trajectory of the robot for the workpiece with complex curved surface,the grinding trajectory planning and optimization algorithm are studied.The data of the surface to be machined is extracted from the 3D model of the workpiece.The curve interpolation method is optimized,and the tool points of the grinding tool path are generated by this method,which avoids the over cutting phenomenon of the workpiece.An algorithm of generating cutter path based on iso-parametric method and iso-scallop method is proposed to avoid the intersection and boundary problems between cutter paths.The coordinate system of the cutter position is constructed,and the corresponding robot grinding trajectory is generated by using the cutter position information.Aiming at the possible problems such as too large variation of robot joint angle and grinding collision,a grinding trajectory optimization algorithm based on recursive method is proposed.In the interest of reducing the grinding trajectory deviation caused by robot absolute positioning accuracy,the robot grinding trajectory compensation algorithm is studied.Based on the improved robot structure model,a six degree of freedom robot error model based on mapping relation is constructed,and the spatial similarity between robot position and position error is analyzed according to the error model.Considering the spatial similarity of the robot workspace,a grinding path compensation algorithm based on the common Kriging space interpolation method is proposed,and the semi-variogram function is used to reduce the computation of the algorithm.The corresponding simulation experiments are carried out by using MATLAB software,and the feasibility of the grinding path compensation algorithm isproved in the theoretical simulation level.For improving the machining quality of robot sand belt grinding,the constant force control algorithm is studied for the six DOF robot sand belt grinding platform with end clamped workpiece.The contact force between the robot end workpiece and the belt wheel is analyzed,and the relationship between the grinding normal force and the tangential force is simplified and verified.Through the simplified relationship and the force mapping relationship between the grinding force and the sensor coordinate system,the relationship between the received force and the grinding contact force on the one-dimensional sensor is established.The relationship between deformation and grinding depth is discussed,and the dynamic model of robot belt grinding based on deformation is established.Considering the nonlinearity and uncertainty of sand belt grinding force,a grinding force control algorithm based on adaptive sliding mode iterative algorithm is proposed,and the stability of the algorithm is proved.In order to verify the effectiveness of the algorithms,the corresponding experimental platforms are built,and three kinds of experiments are designed around the corresponding algorithms.The results of simulation and grinding experiments show that the trajectory planning and optimization algorithm can generate efficient and collision free grinding optimization trajectory,the compensation algorithm can reduce the grinding trajectory deviation and improve the dimensional accuracy of workpiece,the constant grinding force control algorithm can control the grinding force within a certain range and improve the surface quality of workpiece,thus proving the feasibility of the corresponding algorithms.