PALExo: A Parallel Actuated Lower Limb Exoskeleton for High-Load Carrying

Abstract

The exoskeleton robots to assist load-carrying have received much attention in recent years. However, their load capacity and comfort are still insufficient. In this paper, we have developed a novel parallel actuated lower limb exoskeleton(PALExo), that addresses these problems. The novelty is that each limb of the exoskeleton is a 2-SPU underactuated parallel mechanism. Owing to the innovative series elastic module (SEM) with multi-segment stiffness, PALExo is compliant and comfortable for the wearer. The high load characteristic of the parallel structure increases the exoskeleton load capacity, and it can accommodate wearers of different heights without manual adjustment. A dynamic model of the exoskeleton was established, and in order to increase the robustness of the system, we designed a force control method based on sliding mode control and disturbance observer. Finally, the rationality and load-bearing effect of the exoskeleton were verified through a series of experiments including swing following, squatting and walking with loads.

Keywords

• Lower limb exoskeleton
• parallel structure
• sliding mode control
• disturbance observer