Research on the cable-pulley underactuated lower limb exoskeleton

A wide variety of lower limb exoskeletons have been applied in the fields of load-carrying augmentation, walking assistance, and rehabilitation training. The traditional exoskeleton based on fully actuated joints can provide powerful assistance for human motion, while it is bulky requiring a large energy consumption, which limits its application. The passive and quasi-passive exoskeletons are weak in the load-carrying condition due to the lack of active actuators. The traditional underactuated exoskeleton with only one joint actuated generally has limited power assistance. As for soft exoskeleton, uncomfortable feeling resulting from the pressure generated by cable tension on muscles are unavoidable. To compensate these drawbacks, this paper presents a lower limb exoskeleton based on the cable-pulley underactuated principle. By studying the synergies of torque and power assistance at the joints and designing the control strategy, a single cable will be able to drive the hip joint and the knee joint simultaneously, which can reduce the number of actuators. Considering the human-exoskeleton interactive dynamics, a biological method is utilized to evaluate the performance of the exoskeleton. Finally, the contrast simulation results demonstrate that the exoskeleton proposed in this paper can effectively provide power augmentation in load-carrying walking without interfering the human motion and the control strategy is feasible.