Implementation of a Control Algorithm for a Hip Exosuit to Enhance Human Locomotion in Walking and Running

In the last two decades, the interest towards exoskeletons as devices to help restore a motor functionality and to enhance the human performance has largely grown. Among them, soft exoskeletons, or “exosuits”, are becoming popular thanks to their lightweight structure and their potential use in activities of daily living. Exosuits for lower limbs have been created to assist multiple movements with promising results, but only few devices have been designed for running. The main limitation of such devices is the necessity to reverse the motor direction of rotation to alternately support the proper leg, which is not achievable at high human cadences because the motor would work against its own inertia. Therefore, we propose a new design for a hip exosuit for both walking and running assistance based on a Cardan Gear mechanism: the rotation of the motor is converted into a linear, alternated motion of an actuator that preserves a limited amount of cable to provide to the user, hence the motor can continuously spin in one direction. A single motor drives both legs (underactuated exosuit) and assists them during hip extension. This preliminary version of the exosuit is intended for off-board testing purposes and relies on basic biomechanic principles, avoiding the use of complex machine learning processes. Three Inertial Measurement Units (IMUs) are used to acquire the relevant gait parameters and to detect the actual locomotion mode in real-time to create the proper reference position command for the motor. Experiments have been conducted to test the ability of the device to follow the user’s motion, showing optimal outcomes at every human cadence, and the algorithm for locomotion mode detection reported an overall accuracy higher than 98%. These promising results push us towards the further development of the device, with subject-specific profiles of assistance and with the ultimate purpose to reduce the user’s effort in walking and running.