| High precision optical elements have been widely used in national optical engineering,military defense,aerospace and other fields,showing great application potential.The polishing process equipment of high-precision optical elements will directly affect the accuracy and production cycle of the elements.As a new polishing technology with great potential,the robot-assisted bonnet polishing system,which combines bonnet polishing with industrial robot can not only meet the requirements of high precision and high efficiency polishing of optical elements,but also reduce the equipment cost of bonnet polishing,so as to further expand the application scope of this method.However,the stiffness of the robot based machining system is not enough,and it is easy to produce vibration,which is a common problem to be solved.Based on the above analysis,this paper takes the robot-assisted bonnet polishing system as the research object.Aiming at the problems of low system stiffness and vibration in polishing process,the paper focuses on the optimization of static and dynamic performance of the robot to improve the polishing effect of bonnet polishing.The research contents of this paper are as follows:（1）The robot-assisted bonnet polishing system was taken as the research object,and the forward and inverse kinematics modeling of robot was carried out based on Denavit-hartenberg（D-H）method.Then,the Jacobian matrix of robot was deduced by differential transformation method and the calculation results were verified.Finally,the static stiffness model of robot was established according to the static stiffness theory of robot.（2）The traditional static stiffness model of the robot was combined with the force analysis at the end of the robot during the polishing process,an evaluation model of the working stiffness of robot was proposed to realize the quantitative evaluation of the working stiffness performance of robot-assisted bonnet polishing system in the polishing process.Finally,the static simulation and experimental verification were carried out.（3）By analyzing the influence of the working stiffness of the robot-assisted bonnet polishing system on the polishing effect,the feasibility of optimizing the posture to improve the stiffness performance and polishing effect of the robot was revealed.And then,the static performance of robot bonnet polishing system was optimized by maximizing the evaluation index of robot working stiffness.Finally,the effectiveness of the optimization method was verified by experiment.（4）The self-excited vibration of the robot-assisted bonnet polishing system was analyzed by modal analysis method,and the modal parameters of the system were obtained.Then the forced vibration of the robot system was analyzed by dynamic modeling method,and the steady-state response curve of the polishing force of the system was obtained.Combined with the analysis results of the two kinds of vibration,aiming at the vibration generated in the working frequency band near the natural frequency of the robot system,a vibration suppression method based on wave spring-rubber damping bonnet tool was proposed to optimize the dynamic performance of the system.Finally,the effectiveness of vibration suppression and polishing effect improvement of the method was verified through the experiments of fixed-point polishing and whole surface polishing of the robot in the optimal static performance posture. |
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