| In recent years,the performance and service life of products are more and more important with the development of manufacturing.The grinding quality of freeform surface partsplays critical roles in most productsfor the performance,stability and service life.To freeform surface grinding,the domestic mainly depends on the traditional manual operation for the moment.Manual grinding couldn’t guarantee the flexibility and consistency of surface removal machining in the grinding process.And it is not only low efficiency and high scrap rate but difficult to improve the grinding quality.With the rapid development of industrial robot,many scholars have been applying industrial robot to the freeform surface grinding and been doing a lot of research to solve some disadvantages instead of manual grinding.In this paper,the robotic automatic grinding platform based on the compliance controlwas built and the processing technology study and experimental proof were performed with the automatic grinding of aviation blade as the main research subject.The main researches are as follows:(1)The robotic automatic grinding platformwas built for freeform surface.The robot automatic grinding platform consists of industrial robot,robot controller,computer,six dimension force/torque sensor and abrasive belt grinding machine.(2)The grinding model was established and analyzed.The material removal model was builtbased on Preston equation and performed the theory study.The influence relationship between the material removal and processing parameters(such as grinding force,grinding speed,dwell time etc)was discussed.The simulation analysis of model was performed by means of MATLAB software and ANSYS software.And by comparing two analysis results,the compared result showed the consistency of the established model.(3)The compliance control of grinding was studied and realized.According to the grinding force measured on-line by sensor,the appropriate force control strategy wasstudied to control the robotic position and posture for adjusting the contact between workpiece and abrasive belt and realize the active control grinding force to keep the constant grinding force(called active compliance control).According to the curvature change of freeform workpiece,the reasonable divided area and machining step feed were used to adapt to the ever-changing curvature of freeform surface to realize passive compliance in the automatic grinding process.(4)Path planning and off-line programming was realized.The grinding area was reasonably divided according to the geometric profile characteristics of aviation blade.The constant cross section method(the cross section intersects the machined freeform surface to gain a path line)was used to generate grinding path and a series of grinding position vector points were gained on the discrete surface.The organization model and motion model of robotic automatic grinding platform were built and the reverse calculation of vector points was performed according to the derivation of transformation matrix.The end effector movement position and posture as NC code was output and off-line programming program was accomplished to control the robot motion.(5)The grinding experiments of freeform surface were accomplished.The grinding experiments were carried out with robotic automatic grinding platform and experiments data were collected and analyzed.The results show that robotic automatic grinding for freeform surfaces based on compliance control was feasible and effective. |
