ExoBoot, a Soft Inflatable Robotic Boot to Assist Ankle During Walking: Design, Characterization and Preliminary Tests

In this paper, we present the design and characterization of the ExoBoot, a soft inflatable robotic boot for assisting ankle plantarflexion during walking. The ExoBoot integrates a soft textile-based actuator and an IMU sensor into a textile boot, making it low-profile and lightweight. The inflatable actuator generates assistive plantarflexion torque when pressurized by bending on top of the boot. We characterize the torque generated by the ExoBoot at various pressures and ankle angles, achieving a maximum torque of 39 Nm at 483 kPa (70 psi) and 60 degrees ankle angle. In order to evaluate the performance of the ExoBoot during walking, a pilot study with one healthy subject was conducted. Actuation is triggered by an open loop pressure controller, based on the ankle angular velocity measured by an IMU, using high flow rate solenoid valves. At the peak of active assistance, pressure in the actuator reaches 75% of the supply pressure, and maximum torque applied on the ankle is estimated to be 23 Nm. These results demonstrate potential for the ExoBoot to reduce the metabolic cost of walking.