A unique, robust, robotic transtibial prosthesis with regenerative kinetics was successfully built and a 6-month human subject trial was conducted on one male below-the-knee amputee under linear walking conditions. This paper presents the quasistatic system modeling, DC motor and transmission modeling and analyses, design methodology, and model verification. It also outlines an approach to the design and development of a robotic transtibial prosthesis. The test data will show that the true power and energy requirement predicted in the modeling and analyses is in good agreement with the measured data, verifying that the approach satisfactorily captures the physical system. The modeling and analyses in this paper describes a process to determine an optimal combination of motors, springs, gearboxes, and rotary to linear transmissions to significantly minimize the power and energy consumption. This kinetic minimization allows the downsizing of the actuation system and the battery required for daily use to a self-portable level.

PurposeThe purpose of this paper is to describe a project which seeks to develop a new generation of powered prostheses based on lightweight, uniquely tuned, energy‐storing elastic elements in series with optimal actuator systems that will significantly reduce the peak power requirement of the motor and the total system energy requirement while providing the amputee 100 percent of required “push‐off” power and ankle sagittal plane range‐of‐motion comparable to able‐bodied gait.Design/methodology/approachThis paper presents the design, power, and energy‐efficiency analyses, and the results of a five‐month trial with one trans‐tibial amputee subject as part of the first phase of the Spring Ankle with Regenerative Kinetics project.FindingsThe data show that by leveraging uniquely tuned springs and transmission mechanisms, motor power is easily amplified more than four fold and the electric energy requirement is cut in half compared with traditional approaches.Originality/valueThis paper describes an energy efficient, powered transtibial prosthesis currently unavailable commercially. Motor power and energy requirements are reduced with use of a unique design that employs regenerative kinetics.

Even today’s most sophisticated microprocessor controlled ankle-foot prosthetic devices are passive. They lack internal elements that actively generate power, which is required during the “push-off” phase of normal able-bodied walking gait. Consequently, lower limb amputees expend 20–30% more metabolic power to walk at the same speed as able-bodied individuals. Key challenges in the development of an active ankle-foot prosthetic device are the lack of high power and energy densities in current actuator technology. Human gait requires 250W of peak power and 36 Joules of energy per step (80kg subject at 0.8Hz walking rate). Even a highly efficient motor such as the RE75 by Maxon Precision Motors, Inc. rated for 250W continuous power with an appropriate gearbox would weigh 6.6 Kg. This paper presents the first phase of the Spring Ankle with Regenerative Kinetics (SPARKy 1), a multi-phased project funded by the US Army Military Amputee Research Program, which seeks to develop a new generation of powered prosthetic devices based on the Robotic Tendon actuator, that significantly minimizes the peak power requirement of an electric motor and total system energy requirement while providing the amputee enhanced ankle motion and “push-off” power. This paper will present data to show the kinetic advantages of the Robotic Tendon and the electro-mechanical design and analysis of SPARKy 1 that will provide its users with 100% of required “push-off” power and ankle sagittal plane range of motion comparable to able-bodied gait.

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