S²-RTPIC: A State-Switching Remote Therapist Patient Interaction Control for Telerehabilitation

The telerehabilitation robotic system has been envisioned as an alternative to conventional hospital-centered therapy because of convenient training and offering equal opportunity to access medical resources for patients in different areas. However, due to the internet communication latency, how to realize safe, stable, and biomechanics-perceptible remote therapist–patient interaction (RTPI) remains a significant challenge for the therapist-in-the-loop telerehabilitation (TILT) system. To address this issue, a novel position-position/stiffness (P-PK) telerehabilitation architecture was proposed in this article, which exchanges the position information of the therapist and patients and feeds back the reference stiffness of the patient's affected limb to the therapist's side. Furthermore, a novel state-switching RTPI control (S<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RTPIC) scheme is first presented for this P-PK architecture to induce the active participation of the patients during the online TILT training by the variable stiffness voluntary control and their biomechanical states could be synchronously perceived by the therapists over distances for teleassessments. The stability and transparency criteria of the S<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RTPIC scheme under asymmetric time delay conditions were comprehensively analyzed and theoretically proved. Experimental results showed the proposed S<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RTPIC scheme can provide safe RTPI training with effective biomechanical perceptions and participation-inducing training assistance to facilitate teleassessment and telerehabilitation.