面向高陡度保形光学元件的机器人轮带加工技术 (特邀)

Objective High-steepness conformal optics can significantly improve the aerodynamic performance of high-speed vehicles and enhance the environmental adaptability of optical systems, which have a wide range of applications in aerospace and optical engineering. The surface quality and manufacturing efficiency of high-steepness conformal optics have a direct impact on their performance, service life and cost. In the processing of high-steepness conformal optics, the unconventional surface structure with high steepness and large depth-to-diameter ratio, as well as the high cost, processing interference, path limitation, tool wear, low efficiency, loss of precision, and a series of bottlenecks caused by micrometer-level machining accuracy, have seriously restricted their practical applications and engineering needs. With the features of high flexibility, low cost, wide range of motion, and high versatility, robotic machining technology is receiving more and more attention in the manufacturing of complex surfaces. Therefore, a 6-degree-of-freedom robot-based wheel belt machining device is developed by combining the characteristics of high-steepness conformal optics, and this study conducts the research around kinematics, machining quality, process methods and deterministic material removal methods. Methods Firstly, the kinematic analysis of the robot in the machining of high-steepness conformal optics is carried out by combining its multi-degree-of-freedom characteristics. Based on the established coordinate system (Fig.2) and kinematic transfer chain (Fig.3), the machining trajectory and tool position equations for machining the inner and outer surfaces of high steepness conformal optics are derived, and the method of avoiding the “singularity” of the robot in machining is introduced. Secondly, the effects of robotic kinematic control parameters for acceleration (AC) and smoothness (SM) on vibration characteristics (Fig.6) and machining quality are investigated through experiments. Subsequently, a process study is carried out to investigate the performance of three types of abrasive belts with different machining times. Finally, a material removal function that takes into account tool wear is established, and experiments on the iterative machining of high-steepness conformal optics from large to small grain abrasive belts are carried out in a robotic machining device using robotic kinematics control parameters at AC=3 and SM=3. Results and Discussions The equations of machining trajectory and machining tool posture in the processing of internal and external surfaces of high-steepness conformal optics are obtained by deduction (Fig.4), and the method of avoiding the appearance of robot kinematic “singularity” in the machining kinematics is also put forward. The machined surface quality when AC=3 and SM=3 is significantly better than that when AC=0 and SM=0 (Fig.7). The experiments confirm that with the increase of wear time, the material removal ability of the robotic wheel belt processing device and processing surface quality significantly reduce (Fig.8), the larger the abrasive belt particle size of its material removal ability is stronger but the poorer the surface quality of its processing (Fig.9), the abrasive belt of the abrasive grain size of the larger the wear phenomenon is less likely to occur (Fig.10). Conclusions Selecting higher AC and SM robotic kinematic control parameters can effectively reduce the mechanical vibration generated by the robot during machining. In the actual processing should be used in turn from the large grain size to small grain size abrasive belt iterative processing technology. The material removal function considering tool wear is established, and the processing of high-steepness conformal optics is realized by the iterative machining process from large to small grain abrasive belts on the robotic wheel and belt machining device, and the Ra value of surface roughness based on the profilometer detection could reach 58.8 nm.