NONCIRCULAR CUTTING ON A LATHE USING TOOL POSITION AND DIFFERENTIAL MOTOR CURRENT

In this paper, noncircular cutting on a lathe (NCL) using the signals of tool position and differential motor current is developed. First, a neural-network is used to learn a weighted combination of tool positi on and differential motor current of a voice coil servomotor system (V CSS). The differential motor current is achieved from the difference b etween motor current under real cutting and that under air cutting. Th en a nonlinear inverse control based on the learned model is,designed to obtain an acceptable cutting error. Although the nonlinear inverse control is accomplished from the consideration of tool position under real cutting, its performance cannot be ensured as the NCL is subjecte d to the uncertainties (e.g. noise, different cutting conditions, agin g of system components). Under these circumstances, a fuzzy sliding-mo de control is then synthesized with the previous nonlinear inverse con trol to reduce the cutting error. The experimental results of NCL usin g the proposed control including profile error of finished workpiece a nd surface roughness of finished workpiece, are better than those with out the consideration of motor current. (C) 1998 Elsevier Science Ltd. All rights reserved.