A new variable structure sliding mode control strategy for fts in diamond-cutting microstructured surfaces

There was a serious cutting force disturbance in diamond-cutting microstructured surfaces with fast tool servo (FTS) resulting from their discontinuous profile. Although variable structure sliding mode control (VSSMC) strategy with exponential approaching law for FTS can suppress cutting force disturbance to a certain extent in machining process, high machined surface quality was hardly obtained because of the disadvantage of the exponential approaching law. A new VSSMC strategy with a combined approaching law for FTS was presented in this paper. A series of validating experiments were performed in unload and cutting situation respectively. The experimental results showed that the VSSMC with combined approaching law had an obvious advantage in FTS tracking performance over that with exponential approaching law. The system steady-state error was decreased from ±2 to ±0.5 %, and the system rise time was reduced from 2 to 0.8 ms. Measured results of the square-pit microstructured surfaces fabricated by two different strategies showed that a decrease of 10–30 % in the machined surface roughness and an improvement of more than 10 % in the profile accuracy were accomplished by the proposed strategy.