Friction compensation using a double pulse method for a high-speed high-precision table

Abstract

Friction error in reverse motion is one of the principal factors influencing the contour accuracy of high-speed and high-precision computer numerical control (CNC) machine tools, on which closed-loop control is used. On the basis of transient response analysis of servo systems which a conventional proportion–integration–differentiation control strategy are used, the reason for quadrant protrusions occurring in circular motion for worktables is discovered, and the characteristics of the friction error during the feed process such as emergence time, duration, and magnitude of the error due to friction can be predicted correctly. A new approach of compensating for friction error using double compensation pulses is proposed in this article. The first compensation pulse made the worktable escape from the dead zone at the best times, and the second one made the worktable approach to the ideal feed path along the guide as fast as possible. Parameters of compensation pulses such as magnitudes, widths, and starting time are determined by simple mathematic calculation. Results of simulations and experiments show that the method using double pulses proposed in this article can effectively compensate for the friction error in circular motions for a high-speed and high-precision table.