The Walk-Run Ankle is a powered prosthesis for foot replacement designed bySpringactive (US). The design was made to investigate on powered amputee walking and running. During an intership M. Grimmer developed a controller for the powered ankle that is able to change gait independent from speed depending on user intention. In first tests the system was able to mimic human ankle angle and ankle torque patterns for speeds up to 2.6 m/s. In comparison to ESAR (energy storage and return) feet the Walk-Run Ankle is able to mimic healthy subject Range of Motion (RoM) and power requirements for ankle push off. To achieve this the DC motor patterns were optimized to benefit as much as possible from the elastic function of the spring. As spring stiffness was not optimal for 4.0 m/s running tests showed increased differences compared to healthy reference subject data at this speed. Results on the ankle are used to influence the design of a ruggedized powered ankle that also has running capability. The new and improved design is being updated by Springactive to include weight reducing titanium springs that have a longer life, higher efficiency bearings that increase system efficiency, and embedded electronics.

Involved People: Martin Grimmer, André Seyfarth

• M Grimmer, M Holgate, J Ward, A Boehler, A Seyfarth. Feasibility study of transtibial amputee walking using a powered prosthetic foot. International Conference on Rehabilitation Robotics (ICORR), London, 2017, 1118-1123.
• M Grimmer, M Holgate, R Holgate, A Boehler, J Ward, K Hollander, T Sugar, A Seyfarth. A powered prosthetic ankle joint for walking and running. Biomedical engineering online 15 (3), 141, 2016.
• M Windrich, M Grimmer, O Christ, S Rinderknecht, P Beckerle. Active lower limb prosthetics: a systematic review of design issues and solutions. Biomedical engineering online 15 (3), 140, 2016.
• Grimmer, M. and Seyfarth, A. (2015) Walking and running with a powered ankle prosthesis. Dynamic Walking Conference, Columbus, OH, (US), 07/2015.
• Grimmer, M. (2015) Powered Lower Limb Prostheses - Angetriebene Prothesen für die untere Extremität. Phd thesis, Technische Universität Darmstadt, URL: http://tuprints.ulb.tu-darmstadt.de/4382.
• Ward, J., Schroeder, K., Vehon, D., Holgate, R., Boehler., A. and Grimmer, M. (2015). A rugged microprocessor controlled ankle-foot prosthesis for running. In 39th Annual Meeting of the American Society of Biomechanics (ASB), Columbus, OH, (US), 08/2015.
• Ward, J., Schroeder, K., Vehon, D., Holgate, R., Boehler., A. and Grimmer, M. (2014). A microprocessor controlled ankle-foot prosthesis that supports full powered running. In American Orthotic & Prosthetic Association (AOPA), Las Vegas, NV, (US), 09/2014.