微结构功能表面的金刚石超精密加工技术是近年来国外兴起的一项新技术,国内在这一研究领域处于起步阶段。并且由于受加工设备所限,使得该技术在国内的开展显得异常艰难,为了克服这一困难,自行设计带有快速伺服刀架(Fasttoolservo,FTS)的超精密加工机床,提出按照自适应指数趋近律来设计滑动模态控制律,并将滑膜变结构控制策略引入FTS的控制中,同时,将FTS的PID控制策略和滑膜变结构控制策略进行试验对比,试验结果显示,在滑模变结构控制策略下,FTS的响应时间与PID控制相近,但滑模变结构控制算法下几乎无超调,稳态精度高,正弦跟踪控制效果优于常规PID控制算法;最后,根据滑膜变结构控制策略对菲涅尔微结构表面进行金刚石超精密车削加工试验,成功地加工出半径5mm,浮雕深度10μm,表面粗糙度约35nm的菲涅尔微结构。
The ultra-precision diamond machining of micro-structured surface is a new research interest arising in recent years abroad, however, it is just in its infancy for Chinese researchers in this field. Moreover, because of the limitations of advanced machine tools, it is extremely difficult to carry out such studies. In order to solve this problem, an ultra-precision machine tool with fast tool servo (FTS) is designed. Additionally, variable-structure sliding-mode control (VSSMC) strategy designed according to adaptive index reaching law is applied to the control of FTS, and a comparison test under different control strategies is conducted. The experimental results that it is found that the response time for both VSSMC and PID is similar, but for VSSMC, there is almost no overshoot and the sine tracking result is more effective than PID control algorithm. At last, the experiment on ultra-precision diamond turning of Fresnel micro-structured surface is performed by using VSSMC, and a Fresnel micro-structure with a radius of 5 mm, relief depth of 10 μm and surface roughness of 35 nm is successfully machined.