Control of low velocity friction and gear backlash in a machine tool feed drive system

Precision-controlled mechanisms are commonly used in machining applications where the feed rates are low, direction reversals are necessary to obtain the desired work piece profile and precision requirements are in the order of micrometers or sub-micrometers. Under these conditions, friction and gea r backlash effects contribute significantly to the dynamics of the system. This study investigated the use of neural network models to compensate for these effects. The approach was to switch between two controllers: (i) a pr oportional-plus-derivative controller together with a feedforward friction compensator when the transmission gears were engaged; and (ii) a feedforwar d backlash controller when the transmission gears were disengaged. The cont rol scheme was experimentally verified using a retrofitted geared head engi ne lathe. The results obtained were compared to those obtained with a compe nsation method found in the literature. (C) 1998 Elsevier Science Ltd. All rights reserved.