歩行訓練器のための疑似歩行動作－回転運動変換機構の設計

Abstract

In general rehabilitation, the walking stick, parallel bars, and walker are used as walking training devices. Users of these devices bear their weight with the hands or legs, and doing so is painful in some cases. In recent years, population aging has progressed rapidly and a labor shortage in the welfare field has become a serious problem. Against this background, it is necessary to develop a walking training device that can motivate patients to train without assistance from a care worker. In this research, we designed and developed a walker equipped with an assist mechanism that translates simulated walking motion into rotational wheel motion. Using the walker, the patient is supported by a saddle, so the hands and legs are relieved of pain due to supporting body weight. The motion transformer is designed using a planar 6-link mechanism, which transforms oscillating motion to rotational motion. Joint angular displacements were measured with a wearable device. Results showed that general walking trajectories can be obtained. This mechanism is designed such that the pedal follows the foot motion in walking by comparing the coupler curve of the mechanism with the trajectory of an ankle joint in a walking motion. We manufactured four types of walkers for testing. Type I uses a motion transformer consisting of only revolute pairs. Type II uses a motion transformer consisting of revolute pairs and a prismatic pair (sliding joint). Type II-ankle free uses a Type II motion transformer from which two links were removed in order to allow free rotational motion of the ankle joint. Lastly, the Type III walker has an axle in the front in order to facilitate riding from the rear and to allow free rotational motion of the ankle joint. Pedaling force was measured and compared among the four types. It was found that free ankle joint movement was effective in decreasing the pedaling force. The results indicate that the motion transformer could be driven with a small force and with a simulated walking motion as the input. However, the angle between the direction of foot velocity and the direction of pedaling force was approximately π/2, and so driving the device using a pedaling motion could produce a sensation different from that of a normal walking motion. Eliminating discomfort during operation is left as a future task.