Research engineers at Vrije Universiteit Brussel have developed a new powered transtibial prosthesis that mimics natural ankle movement and uses energy in an efficient way. Instead of using powerful motors that start and stop with every step, the system continuously runs a little electrical motor that keeps stretching a rubber band, which is in turn used by the foot as a source of motive power.
By lowering the overall energy requirement of prostheses, smaller batteries can be used, bringing the overall weight of the device down. Moreover, smaller, quieter, more efficient motors can also simplify design and implementation.
From a white paper released by the research team:
From biomechanical
data analysis [14], it is known that an intact ankle joint produces energy during walking. To imitate this, an external power source is needed. The main objective of this research is to retrieve as much energy as possible from the gait and to implement an electric actuator with minimized power consumption. The idea behind the AMP-Foot 2.0 is to use a spring, called the plantar flexion (PF) spring, to accumulate energy from the dorsiflexion phase of stance while the actuator is injecting energy into another spring, called the push-off (PO) spring, during the complete stance phase. By using a locking system, the energy stored in the PO spring, before heel off (HO) occurs, is kept into the system and released for push-off. This way it is possible to reduce the actuator’s power and thus its size while providing the full torque needed for propulsion during walking.
White paper on the AMP-Foot 2.0: Mimicking Intact Ankle Behavior with a Powered Transtibial Prosthesis
