Development of a motorless walking assistive device for foot flexions with instant torque output in gait cycle

With its low birthrate, Japan currently faces an aging issue. As the senior population gradually increases, applying moderate daily exercise has been widely accepted as a key to ease the incidence of life-related diseases, such as cerebrovascular disease that leads to severe aftermath by causing unhealthy gait posture. An already productized active assistive device named RE-Gait^® uses a motor and pressure sensors to detect the force varying from forefoot to heel in walking, thereby aiding both plantarflexion and dorsiflexion for people who are unable to freely control their lower limbs. Corresponding torque output depending on individual physical conditions can be customized from physiotherapist’s site. By contrast, considering a larger torque production with short delay time and less weight, replacing the motor with springs is appropriate. Furthermore, given that the target user includes senior and able-bodied people who possess muscle functionalities, the proposed device reduces the amount of time spent on learning to maneuver the battery-powered type and allows them to walk freely with less concerns on adjusting parameters and battery level. Therefore, the full mechanical types appear to be appropriate. By implementing the ratchet–pawl combination, the necessary energy source used for driving the assistance can be obtained from the body weight. With the pair of mechanical pressure sensors that can store and release the body weight energy, assistance on the foot can be enhanced at each anticipated stage. Four sets of experiments, including Motion Capture to verify the ankle angle variation and electromyography (EMG) to muscle activities, are used to verify the effectiveness of the mechanical walking assistive device. Results show that the device effectively offers assistance to both plantarflexion and dorsiflexion. Comparison with and without attaching the device and trajectories from Motion Capture are all increased. Furthermore, compared with the percentage of maximum voluntary contraction (%MVC) for muscle acquired by EMG, the muscle activities clearly decline. The device effectively provide assistance to foot flexions.