A novel fuzzy controller is proposed here to improve the positioning precision of servo system of CNC lathes. To utilize the high-accuracy potential of the VUD fuzzy controller, a grating-ruler was used as a sensor to measure the displacement of work pieces. Designing the VUD fuzzy controller involved five steps, i.e., setting up universes of discourse and parameters, selecting membership functions, designing a differential circuit, constructing a base of fuzzy rules, and defining a set of contraction-expansion factors. The method of lookup table was applied to construct the base of fuzzy rule...
