Abstract: 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.

Key words: Fast tool servo, Micro-structured surface, Ultra-precision diamond machining, Variable-structure sliding-motled control