A Gaze-Driven Robotic System for Post-Stroke Active Ankle Rehabilitation Training

Abstract

Lower-limb rehabilitation benefits from an input channel that conveys intent cleanly while actuation remains predictable and safety-bounded. We present a clinic-friendly, binocular gaze-driven paradigm that maps quadrant fixations to discrete commands for a two-degree-of-freedom ankle robot (dorsiflexion/plantarflexion and internal/external axial rotation), while inversion/eversion can be left compliant or mechanically constrained as needed. Pupil centers from a near-infrared tracker are mapped to a unit-normalized screen plane using low-order regression with ArUco-guided homography and rapid affine correction. A conservative dwell/occupancy rule triggers jerk-limited trajectories executed under cascaded position–velocity–current control with software rate/torque limits and watchdog supervision. In 20 healthy adults (1,600 trials), selection accuracy reached 99.94% with a 157.6 ms median end-to-end delay (gaze onset to motor onset). A head-tremor stress test produced no wrong-quadrant decisions and withheld decisions at the highest severity when the occupancy criterion was not met. Under passive drives, tracking was sub-degree (RMSE ≤ 0.224◦) with smooth profiles and torques within software limits. Human factors outcomes were favorable, including a pilot post-stroke cohort, with high usability, low workload, and minimal visual fatigue (∆VAS 0.14/0.21). These results support gaze as a practical, hands-free primary control channel for seated ankle training in clinical workflows.