Planning And Parameters Control Of Cycloid Toolpath Guided By Hilbert Curves For Surface Polishing

In robotic polishing process,reasonable toolpath planning and process parameter control are the keys to ensure the quality of workpiece surface.At present,most of the offline programming software follow the toolpath strategy in CAD/CAM system to plan the polishing toolpath.Due to the single movement direction of the generated toolpath,it is easy to leave obvious polishing texture on the surface of the workpiece,which has a certain impact on the surface quality.Compared with unidireactional polishing toolpath,multi-directional polishing toolpath removes materials from the same area in multiple directions,which can avoid the obvious unidireactional toolpath texture and obtain better surface quality.However,multi-directional polishing toolpath will form the more complex toolpath overlap on the workpiece surface,and the curvature change of the workpiece surface will also affect the uniformity of the polishing contact pressure distribution,which leads to the complexity of the polishing material removal model.The ideal automatic polishing strategy is to plan the multi-directional toolpath to cover the workpiece surface evenly,and achieve the uniform removal of the workpiece surface materials through parameter control.This is the key problem that needs to be solved urgently in the current automatic polishing process.In order to solve the above problems,this paper proposes a polishing toolpath model combining Hilbert curve and cycloid,and an algorithm to optimize multi-parameter combination and feed speed of complex toolpath,so as to realize the multi-directional toolpath planning and the control of material removal uniformity distribution for surface polishing.The main work is as follows:(1)Aiming at the problem that the form of polishing toolpath planning is single in offline programming software,a cycloid polishing toolpath model along a new Hilbert curve is proposed,which improves the multi-directivity of the polishing toolpath.Combined with the material removal depth model of polishing,the constraint conditions and adjustment strategies of each parameter of the toolpath are analyzed to ensure the toolpath coverage uniformity of the processing area.(2)In order to improve the uniformity of complex polishing toolpath coverage on freeform surface and the efficiency of multi-parameter combination optimization,a multi-parameter combination optimization model of polishing toolpath is proposed.Firstly,the artificial neural network model is used to fit the material removal depth model of polishing,and then the trained artificial neural network model is used as the objective function of the genetic algorithm to optimize the complex toolpath multi-parameter combination.(3)In order to solve the influence of curvature of freeform surface on material removal uniformity in polishing,an algorithm is proposed to automatically optimize the feed speed of polishing toolpath.Based on the closed-loop feedback theory of automatic control,the material removal amount on the workpiece surface calculated by the polishing material removal depth model is used to evaluate each toolpath point in the polishing toolpath,and the feed speed is continuously adjusted with a small step distance.(4)The actual robot polishing experiment is designed to analyze the polishing effect of various polishing toolpaths on freeform surface.And the feasibility of the multi-directional toolpath and its optimization algorithm are verified by analyzing the surface polishing effect and surface roughness parameters of the polished workpiece.