Hybrid reluctance-actuated Stewart platform for high-precision position control

This paper presents a Stewart platform with hybrid reluctance-actuated struts to achieve six-degrees-of-freedom motion capability. Tailored hybrid reluctance actuators (HRAs) are integrated into a novel strut design to achieve axial force transmission to the Stewart platform’s end effector via flexure-based joints. Each actuator has a motion range of ± 1 mm, leading to a platform workspace of ± 1.34 mm along the vertical z-axis and ± 1.1 mm in x- and y-direction. The rotational range amounts to ± 0.66 ∘ / 0.78 ∘ for tip/tilt motion. By implementation of a MIMO decoupling approach using canonical polyadic decomposition (CPD), position control bandwidths of up to 30 Hz are reached in the task space. The platform achieves millimeter stroke with sub-micrometer translational resolution (45 nm RMS), sub-microradian angular resolution (300 nrad RMS) and a bidirectional repeatability (1 σ ) of 0.15–0.32 µm and 3.5–4.8 µrad. The overall positioning accuracy (RMSE), quantified against external interferometric measurements, amounts to 1-2.3 µm in translation and 11–15 µrad in rotation. • Stewart platform with hybrid reluctance-actuated struts achieving 6 DOF motion capability. • Novel strut design enables axial force transmission to the end effector. • Implemented joint space PI position control reaching up to 30 Hz closed-loop bandwidth. • MIMO decoupling via canonical polyadic decomposition (CPD). • Positioning resolution of 45 nm in translational DOFs and 300 nrad in rotational DOFs.