Abstract:

Aiming at that the cutting force disturbance is easy to be induced when diamond turning micro-structured surfaces because of the mutational cutting depth, a variable-structure sliding-mode control algorithm is proposed to solve the problem. A fast tool servo for micro-structured surface machining is developed, and the corresponding dynamic model is established. A continuous time domain based variable-structure sliding-mode controller is designed. It is robust against changes of system parameters in the cutting process and disturbances of cutting forces. It is also quick to track the command position accurately. So it is adapt to turning process without overshoot. Comparison step response test is conducted between conventional PID and variable-structure sliding-mode algorithm. The result shows that the variable-structure sliding-mode controller has less overshoot than the PID controller, and the steady-state error is less than 20 nm. At last, the effectiveness of this controller is further verified by machining test of micro Fresnel lens as the example of micro-structured surfaces.

Key words: ultra-precision , machining,  , fast , tool , servo,  , variable-structure , slidingmode , control,  , micro-structured , surface