Adaptive control of the WEDM process using a self-tuning fuzzy logic algorithm with grey prediction

摘要

A control system to improve the efficiency of machining a workpiece with varying thickness in the wire electrical discharge machining (WEDM) process is proposed. The abnormal ratio R{sub}(ab) defined by the proportion of abnormal sparks in a sampling period is taken as the controlled variable. It is allowed to reduce temporarily as the cutting thickness is changing. A gain self-tuning fuzzy control algorithm is used so that the transient situation as the cutting thickness is suddenly increasing can be suppressed immediately, and a stable performance can be achieved. In addition, the grey predictor is adopted to compensate the time-delayed R{sub}(ab) caused by the low-pass filter data processing. Experiments reveal that there is a slight variance in the optimal reference of R{sub}(ab) when the cutting thickness is larger than 20 mm, and its value is set to 55% in these cases. Three cases were tested: the constant machining parameters, the constant R{sub}(ab) and the proposed adaptive R{sub}(ab). The results show that the cutting speed can be obviously improved by the proposed control strategy.