To solve the problem of processing quality degradation due to vibration in the robot bonnet polishing system (RBPS), the vibration generation mechanism of the polishing system is revealed based on the modal analysis and dynamic modeling of the RBPS. The modal analysis results showed that the operating frequency of the system is near the natural frequency, which makes the system susceptible to resonance. On the other hand, the forced vibration caused by the polishing force leads to high vibration at the end of the robot during the polishing process. In order to suppress the vibration generated by the polishing system and optimize the dynamic characteristics of the polishing system, a vibration suppression method to increase the damping ratio of the system was proposed. The experiments of SiC fixed point polishing were performed using both vibration suppression bonnet and original bonnet. The surfaces RMS and PV of the parts polished by the vibration suppression bonnet were generally better than those of the original bonnet. The vibration suppression bonnet has improved the convergence ratio of RMS and PV by 42.59% and 19.56% respectively over the original bonnet in the whole surface polishing experiments. The PSD analysis illustrated that the vibration suppression bonnet can better suppress the intermediate frequency errors. The effectiveness of the method in suppressing vibration and improving machining quality is demonstrated.

针对六自由度串联式关节机器人气囊抛光系统因刚度不足引起的加工振动以及引入中频误差的问题,以IRB 6700机器人作为研究对象,基于Ansys Workbench建立模态分析模型,并结合实验分析机器人气囊抛光系统工况频带内动态特性,实验与仿真结果共同表明,机器人气囊抛光系统在工况频带至少存在5阶模态,且共振时机器人末端抖动幅值为mm级,机器人加工严重受限.同时针对机器人气囊抛光系统先进光学元件抛光工艺应用,设计一种阻尼抑振气囊工具头,与普通气囊工具头进行定点抛光与整面抛光对比实验.结果表明:抑振气囊头定点抛光斑粗糙度与频谱幅值普遍低于普通气囊工具头,引入的中频误差较一般气囊工具头低40％,抛光优化效果显著.

In order to further improve the static stiffness of the hydrostatic bearing with the membrane-type restrictor, in this study, a static characteristics model of the pre-pressure single-action membrane-type restrictor (PSMR) is derived, and the criteria for achieving the optimum stiffness of the restrictor are summarized. A PSMR design method following the criteria of optimal stiffness is proposed. Then, the effect of design parameters on the performance of the restrictor is accurately evaluated by numerical simulation and orthogonal experiment with the grinder oil pad, as an example. Finally, the performance of the PSMR is compared with that of the traditional restrictors, and the main source of design error of the membrane-type restrictor is discussed. The results show that the effect of the design error of the membrane structure on the performance of the restrictor is reduced to some extent by the parallel oil circuit of the PSMR. In addition, the membrane-type restrictor designed according to the method of this paper theoretically has better static stiffness than the single-action membrane-type restrictor without pre-pressure, with an average improvement of about 14.14%.

The development of high-reliability, high-precision large-scale CNC ultra-precision grinding machines is essential for the efficient processing and manufacturing of large-diameter optical components. In this paper, we studied the reliability and the precision-maintenance of the ultra-precision grinding machine tool experimentally. First, the subsystems with poor performance were identified based on former operating data, which turned out to be the hydrostatic spindle subsystem and the feed subsystem. Then, we set up specific experimental platforms for these two subsystems to study the thermal deformation and thermal characteristics. The temperature difference between the inflow and outflow oils of the hydrostatic systems is used as the key parameter to model the accuracy evolution. Our results may provide a method to reveal the relationship between the thermal characteristics and the operating parameters of the subsystems, and therefore compensate the thermal error of the whole ultra-precision grinding machine.

Hydrostatic guideways are widely applied in ultra-precision machine tools, and motion errors undermine the machining accuracy. Among all the influence factors, the thermal effect distributes most to motion errors. Based on the kinematic theory and the finite element method, a 3-degrees-of-freedom quasi-static kinematics model for motion errors containing the thermal effect was established. In this model, the initial state of the closed rail as a "black box" is regarded, and a self-consistent setting method for the initial state of the guide rails is proposed. Experiments were carried out to verify the thermal motion errors simulated by the finite element method and our kinematics model. The deviation of the measured thermal vertical straightness error from the theoretical value is less than 1 μm, which ensured the effectiveness of the model we developed.