An Exoskeleton 'Teacher-Student' Gait Rehabilitation Control System Using Real-Time Joint Posture Acquisition: A Feasibility Study.

Recovering the ability to walk following the events of a stroke is important for community participation. For patients that are unable to weight bear, rehabilitation is difficult, for both themselves and for therapists that must manipulate their lower limbs. Exoskeletons can reduce the reliance on a patient's capability and reduce the exertion that therapists must provide to deliver manual rehabilitation. Providing intuitive methods of control is important to ensure that users have the inputs they need. We have implemented a simple joint acquisition system to be used in a 'teacher-student' paradigm, that can attach to a therapist's leg (teacher) to measure their hip and knee posture to then control the equivalent joints of an exoskeleton worn by a patient (student). This would provide a therapist with direct control of their patient's leg, which they can manipulate under supervision, to guide a patient through trajectories they would otherwise provide manual support to achieve. The feasibility of the system is demonstrated with one subject as the teacher and the exoskeleton (without a user) as the student. Using motion capture we assess the reference tracking error and the phase delay in the system through single leg standing gait using three different gains. With high proportional gain the mean (SD) phase delay was 11.1 (0.7) ms and 8.4 (4.9) ms for the hip and knee, respectively. Using the same gain the joints were tracked through normal gait ROM with a mean (SD) error of 7.7 (6.1) degrees and 7.6 (5.4) degrees for the hip and knee, respectively. This early-stage feasibility study demonstrated that a low cost 'teacher-student' control system could control a lower limb exoskeleton.