Grinding Path Planning Of Free-form Surface Robot Based On Tool Contact State

Grinding is one of the important processes to improve the surface quality of workpieces.At present,the grinding of complex curved workpieces mainly relies on the experience of manual grinding,which is difficult to ensure the stability of the surface quality of the curved workpieces;while the grinding based on multi-axis CNC machine tools,due to the degree of freedom or tooling limitations,affects the accessibility of free-form surface grinding.and accuracy consistency.Industrial robots are being used more and more in the field of surface grinding because of their flexible degrees of freedom and maneuverability.However,there are still problems such as poor adaptability of the curvature of the trajectory and difficult to control the uniformity of the surface contour quality of the workpiece in robotic grinding of free-form surfaces.In this paper,based on the analysis of tool-workpiece contact state,considering the curvature change of the free-form surface,a grinding path with curvature adaptability is planned,and the tool tip velocity planning problem is discussed.The full text mainly includes the following contents:(1)Establish a material removal model based on the Preston equation.The amount of material removed from the surface of the grinding workpiece is related to factors such as contact stress and grinding line speed.Based on the ANSYS environment,the contact model between the grinding tool and the surface workpiece is established,the stress distribution in the contact area is analyzed,and the general law of the stress distribution is obtained.Based on this,the material removal model is established,which lays the foundation for the subsequent grinding trajectory planning.(2)Plan the grinding motion trajectory according to the material removal model.First,the NURBS(non-uniform rational B-spline)surface is used to represent the surface contour of the workpiece,and the surface curvature data of the workpiece is calculated;then,the residual height between the grinding tracks is constrained according to the material removal model,and the corresponding line spacing between track points is calculated.In order to avoid the problem of undercutting or overcutting in the large curvature area,by improving the traditional equal-chord-height error algorithm,increasing the grinding control points,and constraining the grinding step size accordingly,the grinding trajectory with curvature adaptiveness is finally obtained.(3)Robot kinematics analysis and end tool speed planning.Analyze the kinematics of the robot,compare and study three typical trajectory interpolation speed planning methods,analyze the position accuracy and motion curve smoothness corresponding to the three planning methods,and reveal the effect of different speed planning methods on the tool end motion stability and positioning accuracy.It can provide a basis for the research of grinding trajectory interpolation.(4)Build a simulation experiment platform and analyze and verify.On the ER-factory simulation platform of Efort,combined with MATLAB for secondary development,a grinding trajectory generation system based on the method in this paper was established,and the grinding point and grinding trajectory were calculated.According to the robot kinematics model,the grinding point information is converted into the robot joint displacement data,and imported into the ER-factory software for simulation verification.Comparing and analyzing the experimental data,the results show that,compared with the isoparametric method,the surface residual height obtained by the method in this paper is more uniform.