Design and control of a lower limb exoskeleton for robot-assisted gait training

Abstract

Robot-assisted rehabilitation of gait still faces many challenges, one of which is improving physical human-robot interaction. The use of pleated pneumatic artificial muscles to power a step rehabilitation robot has the potential to meet this challenge. This paper reports on the development of a gait rehabilitation exoskeleton with a knee joint powered by pleated pneumatic artificial muscles. It is intended as a platform for the evaluation of design and control concepts in view of improved physical human-robot interaction. The design was focused on the optimal dimensioning of the actuator configuration. Safety being the most important prerequisite, a proxy-based sliding mode controller (PSMC) was implemented as it combines accurate tracking during normal operation with a smooth, slow and safe recovery from large position errors. Treadmill walking experiments of a healthy subject wearing the powered exoskeleton show the potential of PSMC as a safe robot-in-charge control strategy for robot-assisted gait training.

Keywords:

• robot-assisted gait rehabilitation
• powered exoskeleton
• compliant actuator
• proxy-based sliding mode control

Acknowledgements

This research is funded by a Ph.D grant of the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen). It is supported by a Concerted Research Action, ‘ALTACRO, Automated Locomotion Training using an Actuated Compliant Robotic Orthosis’, funded by the Research Council of Vrije Universiteit Brussel - VUB.