We report on our design and initial evaluation of a prototype robotic prosthetic leg (RPL) with a powered non-back drivable knee and a hydro-pneumatic passive-resistive ankle. Our design is intended to increase health providers' opportunities when offering their patients greater options, expanding the accessibility of advanced technology to those with lower functional levels while decreasing the overall costs of care.&nbsp; Additionally, this device is intended to improve stance stability, increase balance confidence, and reduce the contralateral limb's ground-reaction stresses.&nbsp; The prototype was developed utilizing commercial off-the-shelf (COTS) material and was tested on a single healthy subject without amputation to validate the design. The prototype functioned correctly and demonstrated the viability of the engineering features introduced with this device.&nbsp; This device provides powered knee motion in ambulation, decreased ankle joint stiffness in stance, improved stability on-ramps, and an optimized ankle joint-axis alignment to enhance symmetry and efficiency.&nbsp; The protoyppe was assessed while the subject performed multiple 10-meter walk test (10MWT) and six-minute walk test (6MWT) on level-ground, inclines, and declines.&nbsp; We will report walking velocity, the frequency of steps, cadence, falls, stumbles, toe-drags, battery consumption, and estimated and measured torque of the knee.The investigator (a healthy subject without amputation, 160 cm tall, 61 kg) applied the RPL to himself with a custom-made bent-knee adaptive socket.&nbsp; A force plate was used to tune the prosthetic leg alignment optimally.&nbsp; The investigator demonstrated the capabilities of the RPL with various cadences and velocities on level-ground and on-ramps. The knee unit was powered by a brushless DC motor with a Hall sensor and a two-channel optical incremental encoder.&nbsp; The ankle incorporated three passive hydro-pneumatic dampers, which provide independent tunable plantar flexion resistance and dorsiflexion assistance.&nbsp; Initial bench alignment was set at 8 degrees of external rotation (yaw) and 8 degrees of eversion (lateral pitch) of the ankle-axis.&nbsp; This ankle design utilized a distal commercial prosthetic rotatable pyramid adapter, which allows for the attachment of several commercially available feet and facilitates the prosthetic foot's external rotation in the transverse plane&nbsp;(independent of ankle and knee rotations) to match the biological limb alignment.The results of this assessment demonstrated that the RPL is safe for use on a healthy, non-amputee subject.&nbsp; It is feasible for future testing on pesons with limb loss.&nbsp; Future work will explore this technology against currently available commercial products to catalog performances for patients and providers to make informed healthcare decisions about the rehabilitation options.&nbsp; Additionally, future kinematic and kinetic testing of this device on persons with limb-loss will further optimize the RPL performance parameters.&nbsp; Future development will include a non-tethered (embedded) controller and batteries with a more advanced control scheme.

Design, Prototyping, and Testing of a Robotic Prosthetic Leg Preliminary Results

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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