JHT-EXO: A Soft Ankle Exosuit for Assisting Walking in Patients with Post-Stroke Foot Inversion

Stroke often leads to foot inversion, seriously affecting the patients' walking ability. In this paper, a lightweight, soft exosuit, JHT-EXO, is proposed for correcting foot inversion to help patients' gait rehabilitation. JHT-EXO mainly consists of two cable driving modules, two foot feedback modules, and a control module, with a total weight of no more than 2.5 kg. The cable driving module can pre-tighten the cable with a designed constant torque spring to prevent the cable from falling off. When the motor is not energized, it can still assist the person in stabilizing the walking gait and reducing power consumption. Customized foot pressure sensors recognize human gait, and IMUs on the feet measure the ankle angle used by the controller to change the output force of the exosuit. The constant torque spring was calibrated and tested, and the experimental results showed that the average output force of the constant torque spring was 20.0 N, with a maximum error of 5.6% compared to the theoretically calculated results. The ground walking test of the exosuit was performed by three subjects in three conditions: wearing the exosuit powered up, wearing the exosuit unpowered, and not wearing the exosuit. The test results showed that JHT-EXO could effectively reduce the ankle inversion angle by $22.11^\circ$ compared to not wearing the exosuit. JHT-EXO is feasible in preventing foot drop and stabilizing flip, and its high mobility and portability show potential for gait rehabilitation of foot inversion patients.