Advances in Powered Ankle-Foot Prostheses

Abstract

We present a review of recent developments in powered ankle-foot prostheses (PAFPs), with emphasis on actuation, high- and low-level control strategies, and pneumatic, hydraulic, and electromechanical actuators. A high-level control strategy based on finite-state machines, combined with low-level control that drives the ankle torque, is the most common control strategy. On the other hand, brushless direct-current motors along with an energy storage and release mechanism are commonly used to reduce the overall size of the actuators and increase PAFP autonomy. Most designs have been evaluated experimentally, showing acceptable results in walking velocity and gait symmetry. Future research must focus on reducing weight, increasing energy efficiency, improving gait phase classification and/or intent of motion-prediction algorithms, updating low-level control of torque and position, and developing the ability of the patient to walk on sloped surfaces and negotiate stairs.

Using a microprocessor knee (C-Leg) with appropriate foot transitioned individuals with dysvascular transfemoral amputations to higher performance levels: a longitudinal randomized clinical trial

“…Furthermore, the combination of vascular disease and aging also results in poor physical strength and balance, impaired neuromuscular coordination, and increased risk for falls. Consequently, it is of prime importance to prescribe an optimal/reliable prosthesis to maximize ambulation safety and restore the ability of older vascular amputees to independently perform physical tasks of daily living [7][8][9][10].…”

Toward the Development of User-Centered Neurointegrated Lower Limb Prostheses

“…Finally, at the low-level, the device is actively controlled by following the received input. At this level, there is a direct tracking of the references used at higher levels (e.g., position or torque) [95]. Proportional integral (PI) and proportional integral derivative (PID) systems are commonly used [95] to change emulated stiffness and damping values of the prosthetic joints to create desired joint behavior.…”

The Effects of Slope-Adaptive Prosthetic Ankle-Feet on Sloped Gait Performance and Quality in Unilateral Transtibial Prosthesis Users: A Scoping Review

“…The commercially available prosthetic feet that are most commonly prescribed do not permit automatic sagittal plane adjustment of the ankle angle and/or impedance while walking on slopes as they are passive nonarticulated, solid designs or include ankle articulations with fixed rotational resistance that return to a neutral orientation when unloaded. 9 A lack of controlled dorsiflexion range has been suggested as the cause of instability in prosthesis users when walking up slopes. 4,10 These limitations of commercial prosthetic feet can lead to compensatory gait patterns when walking on slopes, including increased knee flexion of the sound side 11 and residual limb 12 in early stance, decreased or absent hip extension of the sound side halfway through the gait cycle, 10 increased prosthetic side peak hip power, 12 and decreased walking speed.…”

“…To that end, when the biological ankle is lost due to transtibial amputation, that individual loses a crucial component of the volitional control necessary to adapt to sloped walking. The commercially available prosthetic feet that are most commonly prescribed do not permit automatic sagittal plane adjustment of the ankle angle and/or impedance while walking on slopes as they are passive nonarticulated, solid designs or include ankle articulations with fixed rotational resistance that return to a neutral orientation when unloaded 9 . A lack of controlled dorsiflexion range has been suggested as the cause of instability in prosthesis users when walking up slopes 4,10 .…”