Compensation of friction error for X-Y table

To reduce contour error due to friction of computer numerical control (CNC) machine tools, the reason that quadrant protrusions in circular motion of X-Y table occurs and the method for error compensation are investigated by simulations and experiments. The mechanism of emergence of friction error can be revealed by performance analysis of transient response of the servo system. A new approach for compensation of friction error with double compensation pulses is proposed. The parameters of compensation pulses such as magnitudes, widths and time of starting are determined mathematically. The input commands with compensation pulse makes the worktable escape from dead region at the best time, and the worktable approaches to ideal feed path along the guide as rapidly as possible. The simulation and experiment show that the magnitude of protrusions due to friction are reduced from 15 μm to 2 μm to achieve the desired situation effectively.