Investigation into Energy Efficiency and Regeneration in an Electric Prosthetic Knee

Powered lower limb prosthesis are facing energy and efficiency challenges. This article presents an investigation into reducing the energy losses and increasing the efficiencies of energy regeneration for a powered prosthetic knee during level ground walking. The results showed that the regeneration and overall system efficiencies would dramatically increase if the negative mechanical load in the braking quadrants are within the regenerative zone of the motor. This approach reduced the energy losses in the stance and swing phases and increased the possibility of harvesting more negative mechanical energy during level ground walking

Towards a Smart Semi-Active Prosthetic Leg: Preliminary Assessment and Testing

This paper presents a development of a semi-active prosthetic knee, which can work in both active and passive modes based on the energy required during the gait cycle of various activities of daily livings (ADLs). The prosthetic limb is equipped with various sensors to measure the kinematic and kinetic parameters of both prosthetic limbs. This prosthetic knee is designed to be back-drivable in passive mode to provide a potential use in energy regeneration when there negative energy across the knee joint. Preliminary test has been performed on transfemoral amputee in passive mode to provide some insight to the amputee/prosthesis interaction and performance with the designed prosthetic knee

A novel hydraulic energy-storage-and-return prosthetic ankle : design, modelling and simulation

In an intact ankle, tendons crossing the joint store energy during the stance phase of walkingprior to push-off and release it during push-off, providing forward propulsion. Most prostheticfeet currently on the market – both conventional and energy storage and return (ESR) feet –fail to replicate this energy-recycling behaviour. Specifically, they cannot plantarflex beyondtheir neutral ankle angle (i.e. a 90° angle between the foot and shank) while generating theplantarflexion moment required for normal push-off. This results in a metabolic cost ofwalking for lower-limb amputees higher than for anatomically intact subjects, combined witha reduced walking speed.Various research prototypes have been developed that mimic the energy storage and returnseen in anatomically intact subjects. Many are unpowered clutch-and-spring devices thatcannot provide biomimetic control of prosthetic ankle torque. Adding a battery and electricmotor(s) may provide both the necessary push-off power and biomimetic ankle torque, butadd to the size, weight and cost of the prosthesis. Miniature hydraulics is commonly used incommercial prostheses, not for energy storage purposes, but rather for damping and terrainadaptation. There are a few examples of research prototypes that use a hydraulic accumulatorto store and return energy, but these turn out to be highly inefficient because they useproportional valves to control joint torque. Nevertheless, hydraulic actuation is ideally suitedfor miniaturisation and energy transfer between joints via pipes.Therefore, the primary aim of this PhD was to design a novel prosthetic ankle based on simpleminiature hydraulics, including an accumulator for energy storage and return, to imitate thebehaviour of an intact ankle. The design comprises a prosthetic ankle joint driving two cams,which in turn drive two miniature hydraulic rams. The “stance cam-ram system” captures theeccentric (negative) work done from foot flat until maximum dorsiflexion, by pumping oil intothe accumulator, while the “push-off system” does concentric (positive) work to power pushoff through fluid flowing from the accumulator to the ram. By using cams with specific profiles,the new hydraulic ankle mimics intact ankle torque. Energy transfer between the knee andthe ankle joints via pipes is also envisioned.A comprehensive mathematical model of the system was defined, including all significantsources of energy loss, and used to create a MATLAB simulation model to simulate theoperation of the new device over the whole gait cycle. A MATLAB design program was alsoimplemented, which uses the simulation model to specify key components of the new designto minimise energy losses while keeping the device size acceptably small.The model’s performance was assessed to provide justification for physical prototyping infuture work. Simulation results show that the new device almost perfectly replicates thetorque of an intact ankle during the working phases of the two cam-ram systems. Specifically,78% of the total eccentric work done by the prosthetic ankle over the gait cycle is returnedas concentric work, 14% is stored and carried forward for future gait cycles, and 8.21% is lost.A design sensitivity study revealed that it may be possible to reduce the energy lost to 5.83%of the total eccentric work. Finally, it has been shown that the main components of the system– cams, rams, and accumulator - could be physically realistic, matching the size and mass ofthe missing anatomy

The control of recycling energy strorage capacity for WalkMECHadapt

In this study, we present the implementation of the controller for adapting the energy storage capacity of the WalkMECH according to the different walking speeds and gait characteristics of an amputee. Since the main aim is to keep the design both mechanically and metabolically energy-efficient, the actuation system is designed based on the minimal actuation principle. The overall system, called WalkMECHadapt, is evaluated with the experimental test set-up with a healthy subject. Test results show that the system is working sufficiently for adapting the energy storage capacity of the WalkMECHadapt thanks to the simple nature of the controller architecture

The control of recycling energy strorage capacity for WalkMECHadapt

In this study, we present the implementation of the controller for adapting the energy storage capacity of the WalkMECH according to the different walking speeds and gait characteristics of an amputee. Since the main aim is to keep the design both mechanically and metabolically energy-efficient, the actuation system is designed based on the minimal actuation principle. The overall system, called WalkMECHadapt, is evaluated with the experimental test set-up with a healthy subject. Test results show that the system is working sufficiently for adapting the energy storage capacity of the WalkMECHadapt thanks to the simple nature of the controller architecture