A Soft Inflatable Wearable Robot for Hip Abductor Assistance: Design and Preliminary Assessment

In this paper, we present the design, characterization and preliminary testing of a soft inflatable wearable device that can apply assistance in parallel with a wearer's abductor muscles. The device is composed of a three-piece textile suit with and integrated textile-based inflatable hip abduction actuator (HAA) that can produce an assistive torque about the hip in the frontal plane when pressurized. We characterize the torque output of the device at multiple hip obliquity angles and pressures using an instrumented mannequin, and show that the device achieves a maximum torque of similar to 14 Nm at 345 kPa. A proof of concept, single subject test was performed to evaluate the ability of the wearable device to assist hip abduction during single leg stance by monitoring abductor muscle activity. At the high assistance (similar to 14% of biological hip moment), the device reduced the measured muscle activity in gluteus medius (30%), gluteus maximus (43%) and tensor fasciae latae (37%) compared to a condition without assistance during single leg stance. These results demonstrate potential for the soft inflatable wearable device to provide assistive hip abduction torque during walking in order to improve reduced lateral stability caused by muscle weakness.