J-Exo: An exoskeleton with telescoping linear actuators to help older people climb stairs and squat

This paper presents a novel lower limb exoskeleton, J-Exo, to help older people climb stairs and squat. Inspired by canes for the elderly, the leg actuators of this exoskeleton use a linear telescoping mechanism that can accommodate wearers of different heights. It avoids the articulated exoskeleton's inability to align with the user's anatomical joints accurately. The J-Exo supports the person through a crotch strap, which requires less motor performance. In addition, a low-cost flexible gait detection insole was designed. The insole consists of duct tape and a soft rubber tube. The pressure of the tube can detect the phase of the gait. A practical torque control strategy is proposed for this exoskeleton. The motor compensates for the leg actuator's weight, friction, and inertia forces during the swing phase. During the stance phase, the compensation is accompanied by applying a force proportional to the plantar pressure. Six subjects performed stair climbing, squatting, and endurance time experiments to validate the effectiveness of the exoskeleton. The results showed that subjects wearing the exoskeleton had reduced muscle activity in the stair climbing and squatting experiments. In the endurance experiment, the exoskeleton extended the subjects’ endurance time by a factor of 7.11. The J-Exo shows great potential for helping older adults reduce their physical load and increase their endurance.