Robot-based Complex Mold Surface Bonnet Polishing Technology Research

Complex curved surface parts are widely used in aerospace,optical,automotive and other fields,and many ultra-precision finishing technologies have emerged to realize automated polishing of complex curved parts,and bonnet polishing is one of the important technologies.In order to further improve the applicability of bonnet polishing technology to complex curved surfaces,this paper conducts research on polishing of complex curved surfaces based on robotic composite bonnet polishing technology,aiming to achieve lowcost,high-efficiency and high-quality polishing of complex curved workpieces.The specific research contents include the following aspects:(1)A robotic bonnet polishing system is designed and built.Firstly,we analyze the requirements of the polishing system and derive the design index of the polishing system by combining the characteristics of bonnet polishing and robotic polishing technology;Secondly,according to the design index,the structure of each part of the polishing system are selected and the structure is designed;In addition,the improved D-H parameter method is used to parameterize the polishing system;Finally,we carry out the forward and reverse kinematic solution and workspace analysis of the polishing system,and conduct the theoretical derivation of the poses of its key points to link the components in the polishing system,so that the components in the polishing system are connected.(2)Reconstruction and analysis of workpieces with unknown CAD information and extraction of their surface target points.Firstly,a laser scanner is used to collect the surface point cloud data of such workpieces,reconstruct the workpiece model and perform error analysis on the results;Secondly,geometric feature analysis is performed on complex surfaces to assist in determining the relevant polishing parameters and bonnet head design dimensions;Finally,the surface information is converted into line information and further converted into point information which is easy to operate in the polishing system.The target point information on the workpiece surface is extracted,processed and visualized by Matlab.(3)The kinematic planning simulation of the polishing system is performed in the ROS environment.Firstly,the URDF model file of the polishing system is written to complete the modeling of the polishing system in ROS;Secondly,the required files for motion planning are configured using Move It Setup Assistant;Finally,the Cartesian space motion planning is carried out by calling the relevant APIs programmatically,and a polishing method based on biased trajectory points is proposed to avoid the problem of missed polishing in the contact center region during bonnet polishing and to improve the global irregularity of polishing inclination angle.(4)The polishing experiments of complex curved workpieces are carried out.Firstly,the experimental conditions are elaborated,the polishing system is calibrated and the bonnet polishing tools are prepared;Secondly,according to the polishing object and experimental conditions,the process flow is formulated and the polishing process parameters are determined;In addition,pre-experiments are conducted for different processes,the bias trajectory points of the respective processes are calculated indirectly and the polishing experiments are conducted;Finally,the three-dimensional morphological analysis of the workpiece surface before and after polishing is conducted,and the surface roughness value is reduced from the surface roughness value decrease from 0.72 μm to 0.04 μm,which verified the feasibility of this polishing system and the effectiveness of the polishing method.