Strategic Research Program 17 (VUB Funding)

Detailed description of the novel device:

The device mainly distinguishes itself from commercial prostheses thanks to its new type of actuation providing a compact and energy efficient solution to the challenge of ankle-foot actuation. This new actuation method consists of using springs, a servo motor and a locking mechanism, coupled with a sensory network providing intelligence to the robotic device. The AMPfoot 4.0 design is also based on previous research conducted on the AMP-Foot 2. However, it is important to note that in contrast with its preceding designs, the AMP-Foot 4.0 does not provide active propulsion at push-off.

During walking, the AMP-Foot 4.0 working principle is divided into two main logic sequences, i.e. the stance and the swing phase. These two phases are detected by analyzing gyroscope and acceleration measurements from an Inertial Measurement Unit chip. During the stance phase, the ankle performs a dorsi-flexing movement while a plantar-flexing torque is applied at the ankle. The person's gravitational potential energy is stored into elastic potential energy by means of the used spring. It is this spring that provides the plantar-flexing torque required at the ankle as reaction to the movement of the user. Due to the use of a locking system, the prosthesis can adapt its so-called zero torque rest point depending on the slope or stride length of the user. This provides adaptability and therefore greater comfort compared to prostheses with a fixed zero torque rest point. During the swing phase, the locking mechanism unlocks to free the ankle movement. Parallel springs external to the stance system are then activated to reset the foot to its initial position. From that moment, the device is ready for a new step.

Inclusion criteria

• Unilateral transfemoral amputees
• Unilateral transtibial amputees
• Able-bodied individuals

Exclusion criteria

• Children
• Functional k-level lower than 4 (Amputee has the ability for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress or energy levels)