Effects of Independent Links of the Lower Leg on the Ankle Joint in Walking Assistance

There is an urgent need for a gait assisting device that simultaneously compensates for the loss of gait function reducing ankle plantarflexion torque and limited dorsiflexion range of motion (ROM). In this work, a walking assistance is proposed by using a device with an independent link attached on the ankle joint. We investigated the effect of the independent link on ankle joint torque and the assisted motion range via analysis. The results of the analysis revealed that the proposed device could assist patients with limited ankle dorsiflexion ROM and low plantarflexion strength simultaneously. For patients with mild dorsiflexion ROM limitation of the ankle joint (7° or more), it was found that walking within the limited ROM is possible and that a large assisting torque is possible by front side link assistance. The ankle torque load can be reduced by 60% under the conditions of this work. For patients with severe ankle dorsiflexion ROM limitation (2° or more, 6° or less), it was found that walking within the ROM was possible and that torque assistance is possible by back side link assistance. The ankle joint torque load can be reduced by 30% under the proposed conditions in this work.