Biomechanical Design and Prototyping of a Powered Ankle-Foot Prosthesis (original) (raw)
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Conceptual Design of a Powered Ankle-foot Prosthesis for Walking with Inversion and Eversion
Procedia Technology, 2014
Human ankle is a series of joints that are highly integrated [1], , where tolecular joint (permits dorsiflexion-planter flexion) and subtalar joint (permits inversion-eversion) play vital roles.A conceptual design of an ankle joint is presented here to facilitate the terrain adaptability maintaining natural gait patterns and stability for person with single limb transtibial amputation. The design consists of physiological ankle movements during walking on flat surface as well as uneven terrain. The ankle joint (spherical joint) permits planter flexiondorsiflexion by the control of passive actuators (springs) and active actuator (motor). It further allows movement in the frontal plane inward/outward about an imaginary centre line of body in order to adapt the roughness of surface. The kinematic behavior of the prosthesis is analyzed. Foot portion of the ankle prosthesis are conceptualize as composite structure to minimize ground contact shock. A 3D prototype is created to represent the conceptual design, which successfully demonstrated the ankles rotational motion.
Simulation of a Low Cost Powered Ankle-Foot Prosthesis during Stair Ascent and Descent Gaits
International Journal of Science and Research (IJSR), 2016
Human ankle is a synovial hinge joint where the tibia and fibula bones of leg meet the talus bone of the foot. The joint allows the dorsiflexion and plantar flexion movement of the foot during various stances of walking, running, climbing etc. Transtibial prosthesis helps to regain the function of lost foot. The advancement in transtibial prosthesis using myoelectric driven powered ankle foot prosthesis helped to achieve the most natural gaits in walking, climbing, and running etc. through nerve signals from the brain by nerve rewiring surgery which is very costly in INDIA. Most transtibial amputee cannot afford such advance technology in prosthesis to fulfill the loss caused, therefore, these amputee use conventional prosthetic leg that has no motion in ankle joints. In this paper, a design of an ankle foot device is presented to assist transtibial amputees during stair ascent and descent gaits. The device permits the dorsiflexion and plantarflexion movement of the prosthetic ankle during stair ambulation mimicking the gait pattern of normal human ankle. The dorsiflexion and plantarflexion movement is controlled by an actuator using PID. A 3D model, control scheme, and analysis of prosthetic device are presented in this paper. The objective of this paper is to present an easily affordable prosthetic device that is capable of assisting transtibial amputee during stair ambulation.
Journal of NeuroEngineering and Rehabilitation, 2013
Background: People with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. Methods: We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height-and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Results: Use of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Conclusions: Use of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.
Concept Through Preliminary Bench Testing of a Powered Lower Limb Prosthetic Device
Journal of Mechanisms and Robotics, 2010
This paper outlines the design and testing of a powered ankle prosthesis, which utilizes a four-bar mechanism in conjunction with a spring and motor that mimics nonamputee (normal) ankle moments. This approach would enable transtibial (below the knee) amputees to walk at a normal speed with minimal energy input. The design takes into account the energy supplied by the wearer required to achieve many of the desired characteristics of a normal gait. A proof-of-concept prototype prosthesis was designed, optimized, fabricated, and tested with the purpose of demonstrating its ability to match crucial ankle moments during the stance phase of gait. Testing of this prosthesis proved crucial in determining the prosthesis’ capabilities and in evaluating this approach.
Parameter estimation for a prosthetic ankle
Annals of Biomedical Engineering, 1995
The mechanical parameters of a model of an energy storage and return ankle prosthesis are estimated for normal level walking by means of an optimization procedure. The walking cycle is divided into six fields, such that the power does not change sign within each field; the transition between successive fields occurs at zero power. The optimal spring stiffness as a function of time, is found by optimizing a quadratic cost function to minimize the difference between the estimated ankle moments and the moments in normal walking. The optimization is subjected to four continuous constraints within each field and to two continuity constraints for the transitions between successive fields. The time-varying spring stiffness and the implications of additional external energy are discussed and are presented as recommendations for the designer.
Control of a Powered Ankle–Foot Prosthesis Based on a Neuromuscular Model
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2010
Control schemes for powered ankle-foot prostheses rely upon fixed torque-ankle state relationships obtained from measurements of intact humans walking at target speeds and across known terrains. Although effective at their intended gait speed and terrain, these controllers do not allow for adaptation to environmental disturbances such as speed transients and terrain variation. Here we present an adaptive muscle-reflex controller, based on simulation studies, that utilizes an ankle plantar flexor comprising a Hill-type muscle with a positive force feedback reflex. The model's parameters were fitted to match the human ankle's torque-angle profile as obtained from level-ground walking measurements of a weight and height-matched intact subject walking at 1 m/s. Using this single parameter set, clinical trials were conducted with a transtibial amputee walking on level ground, ramp ascent, and ramp descent conditions. During these trials, an adaptation of prosthetic ankle work was observed in response to ground slope variation, in a manner comparable to intact subjects, without the difficulties of explicit terrain sensing. Specifically, the energy provided by the prosthesis was directly correlated to the ground slope angle. This study highlights the importance of neuromuscular controllers for enhancing the adaptiveness of powered prosthetic devices across varied terrain surfaces.
Advances in Powered Ankle-Foot Prostheses
Critical Reviews in Biomedical Engineering, 2018
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.
A low-power ankle-foot prosthesis for push-off enhancement
Wearable Technologies
Passive ankle-foot prostheses are light-weighted and reliable, but they cannot generate net positive power, which is essential in restoring the natural gait pattern of amputees. Recent robotic prostheses addressed the problem by actively controlling the storage and release of energy generated during the stance phase through the mechanical deformation of elastic elements housed in the device. This study proposes an innovative low-power active prosthetic module that fits on off-the-shelf passive ankle-foot energy-storage-and-release (ESAR) prostheses. The module is placed parallel to the ESAR foot, actively augmenting the energy stored in the foot and controlling the energy return for an enhanced push-off. The parallel elastic actuation takes advantage of the amputee’s natural loading action on the foot’s elastic structure, retaining its deformation. The actuation unit is designed to additionally deform the foot and command the return of the total stored energy. The control strategy o...
Analyzing and considering inertial effects in powered lower limb prosthetic design
2015
Powered lower limb prostheses are designed to restore the biomechanical functionality of missing parts of their users' bodies. However, they do not yet meet the versatility and efficiency of the biological counterpart. A crucial open issue is how the prosthetic system and its actuator should be designed to achieve an energy efficient operation. This paper proposes a novel methodology for the design and optimization of elastically actuated lower limb prostheses. In contrast to other studies, actuator inertia is considered in this paper. Further, the approach considers the inertial parameters of the prosthesis after initial design to revise the requirements and redesign the system. The design procedure is described and presented for the example of a powered prosthetic knee. In this, considering actuator inertia enables to find optimal stiffness values for walking that are not to be found with common methods and altered optimal values for other gait types. Further, the consideration of the inertial properties of the pre-designed prosthesis in a gait simulation lead to distinctly lower requirements for peak power. For walking those are decreased by about 10% while in running a reduction of over 30% is observed. Analyzing those results, the potential of considering actuator and prosthetic inertia in design and thus the benefits due to the presented method are pointed out.
A powered prosthetic ankle joint for walking and running
BioMedical Engineering OnLine, 2016
Background The current standard for prosthetic ankle joints are passive SACH (solid ankle cushioned heel) or carbon fiber ESAR (energy storage and return) feet. In contrast to the stiff SACH feet, ESAR feet are able to store energy during the stance phase and release it later during push-off [1, 2]. Through this they are able to mimic the function of the Achilles tendon [3]. In contrast to human muscles, carbon feet are not able to create net positive work for ankle plantar-or dorsiflexion. Thus, actuation systems are required to achieve able-bodied ankle behavior. Different approaches with pneumatics [4] and electric motors [5-11] have been developed in recent years. In order to support amputees in common daily life activities like walking on flat terrain [10], stairs [12] or slopes [13],