Position-dependent friction compensation for ballscrew tables

This paper describes a compensation scheme for positional-dependent friction in ballscrew-type X-Y tables. Based on the observations of the experimental data the friction of the ball-screw table exhibits periodical behaviour with varying amplitudes upon different velocities. The friction profile function f_x(x) can be determined by measuring the static friction in each position. The parameter of amplitude for scaling the friction profile is calculated in real time for friction compensation. This formulation is then applied to the friction observer developed by Hassig and Friedland (1991). The convergence of the modified friction compensator is proved and the simulation results demonstrate the ability of the proposed method