A novel ball-screw-driven rigid-flexible coupling stage with active disturbance rejection control to compensate for friction dead zone

The conventional ball-screw-driven high-speed precision motion stage, which is often referred to as rigid stage, usually employs mechanical bearings to achieve superior stiffness and rapid response. Despite these advantages, a high-stiffness design of the rigid stage can limit the positioning precision owing to the friction dead zone. In this study, we propose a ball-screw driven rigid-flexible coupling (RFC) stage to compensate for the friction dead zone through flexure hinges. The frequency response functions indicate that friction is converted into elastic deformation of the flexure hinges. In addition, active disturbance rejection control (ADRC) is implemented to cancel the flexure hinge vibration and maximize the RFC stage performance. Preliminary simulation results confirmed the effectiveness of the proposed mechanical control scheme. This effectiveness was further demonstrated through three comparative experiments. First, in five repeated long-stroke point-to-point motion experiments, the RFC stage with ADRC exhibited excellent consistency in both transient and steady-state responses, achieving a positioning precision of +/- 0.1 mu m. Second, the RFC stage with ADRC was able to track a ladder-like step reference with fast transients and positioning precision of +/- 0.1 mu m. Finally, in a sinusoidal tracking experiment, the maximum and root-mean-square tracking errors of the RFC stage with ADRC were reduced by 88.85% and 43.32%, respectively, compared to the rigid stage with PID control.