Simple and robust feedforward compensation of quadrant glitches using a compliant joint

Quadrant glitches commonly occur when rolling/sliding bearings are used in precision motion stages. Compensating them accurately using feedforward control is challenging due to the need for complex friction models, and the variability of on-machine friction dynamics. This paper shows that quadrant glitches can be accurately and robustly compensated with simple friction models by attaching the bearing to the moving table using a joint that is very compliant in the motion direction. Design of a prototype joint that achieves high compliance by combining a positive-stiffness flexure with negative-stiffness permanent magnets is presented. Large reductions in quadrant glitches are demonstrated in experiments.