Safe and compliant guidance in robot-assisted gait rehabilitation using Proxy-based Sliding Mode Control

Research in robot-assisted gait rehabilitation has seen significant improvements in human-robot interaction, thanks to high performance actuator technologies and dedicated control strategies. In this context we propose a combination of lightweight, intrinsically compliant, high power actuators (pleated pneumatic artificial muscles, PPAMs) with safe and adaptable guidance along a trajectory by means of proxy-based sliding mode control (PSMC). Treadmill walking experiments performed by a healthy subject wearing a powered knee exoskeleton indicate two main challenges: synchronizing the compliant device and the subject, and tuning the control parameters in view of safe guidance. The exoskeleton is able to compliantly guide the test person´s knee along various target trajectories, while ensuring a smooth response to large perturbations.