Design and Control of an Active-passive Lower Limb Exoskeleton for Squat Support

In industrial assembly occasions, workers often need to hold heavy tools or maintain a half-squat posture to complete complex assembly tasks, which can lead to health problems and affect assembly efficiency. However, using only a single active or passive assisted exoskeleton is difficult to meet the requirements of assisting workers walking and providing squat support at the same time. In response to this problem, an active-passive lower limb exoskeleton based on a toothed ratchet is designed innovatively in this paper, and the corresponding active-passive state switching control strategy is proposed. The exoskeleton has two states. When in the active state, the motor is enabled, which can further provide walking assistance to the wearer. When in the passive state, the motor is disabled and the toothed ratchet mechanism provides an auxiliary support for semi-squatting. Collaborative experiments were conducted to verify the effectiveness of the active-passive state switching control strategy. And the muscular activity was evaluated in static squatting tasks. Results show that the EMG signal of muscles monitored during the squat decreased by 47% to 76% after wearing the exoskeleton.