Lower Extremity Exoskeleton for Stair Climbing Augmentation

This paper presents a light-weight lower extremity exoskeleton and its associated control method to augment the locomotion for climbing stairs. A compact slider crank mechanism is designed for the knee joint to offer the required torque. A spring based quasi-passive hip joint is adopted to compensate gravity force of lifting leg. A hybrid assistive control strategy is proposed to ensure the requirement and coordination of different gait phases for the exoskeleton. In standing phase, a direct gravity balancing method is used to support the body and payload. In swing phase, a force tracking control method is utilized to enhance leg mobility. Stair climbing tests show that the gravity compensation method and force-tracking controller enhance the stair climbing mobility, and demonstrate the feasibility of the designed exoskeleton and the proposed hybrid control strategy.