A light-weight active orthosis for hip movement assistance

• Development of a novel light-weight wearable powered bilateral pelvis orthosis.
• Design of a novel compact, light-weight series-elastic actuator (SEA).
• SEA closed-loop torque control bandwidth equal to 15 Hz.
• SEA output impedance ranges from 1 to 35 N m /rad in human gait frequency spectrum.
• The overall system usability was proved by tests with a healthy subject.

In the last decades, wearable powered orthoses have been developed with the aim of augmenting or assisting motor activities. In particular, among many applications, wearable powered orthoses have been also introduced in the state of the art with the goal of providing lower-limb movement assistance in locomotion-related tasks (e.g.: walking, ascending/descending stairs) in scenarios of activities of daily living. In this paper we present a light-weight active orthosis endowed with two series elastic actuators for hip flexion–extension assistance. Along with the description of its mechatronic modules, we report the experimental characterization of the performance of the actuation and control system, as well as the usability test carried out with a healthy subject. Results showed a suitable dynamic behavior of the actuation unit: the closed-loop torque control bandwidth is about 15 Hz and the output impedance ranges from about 1 N m/rad to 35 N m/rad in the frequency spectrum between 0.2 and 3.2 Hz. Results from the tests with the healthy subject proved the overall system usability: the subject could walk with the device without being hindered and while he received a smooth assistive flexion–extension torque profile on both hip articulations.