1,267 research outputs found
Potential Optimal Gait Performance of Mauch S-N-S Prosthetic Knee Configurations as Predicted by Dynamic Modeling
Patients with prosthetic legs routinely suffer from abnormal gait patterns which can cause health issues and eventually lower the quality of their lives. Despite the half-century advance in the technology of prosthetic knees, from the purely mechanical to microprocessor controlled systems, patient testing suggests that very little progress has been made in the quality of the kinetics and kinematics of amputee gait. Moreover, the cost of microprocessor controlled prosthetic knees may be 10 times more than the purely mechanical knees. While prosthetic knees have become more complex and expensive, it is not proven that the prosthetic knee is a central factor limiting amputee patient gait. The goal of this project is to determine the degree to which the Mauch S-N-S prosthetic knee limits the ability of a subject to achieve a close to normal gait pattern. In this research, we developed dynamic models of the Mauch S-N-S prosthetic knee based on gait-like motion tests of a Mauch knee cylinder and used the dynamic models in computational simulations to determine the best achievable gait, on the basis of obtaining near-to-normal gait kinematics and kinetics. Idealized assumptions were made for patient performance capability and characteristics of the other prosthetic leg components, to obtain the desired focus on knee capabilities and limitations. The results indicate that even with this relatively old technology prosthetic knee, subjects have the potential to walk much more normally than the patient-test data indicates. An extension of the study showed the significant interaction of the prosthetic knee and ankle with respect to achieving optimal gait. The methodology of this study can be applied to evaluation other knees, prosthetic components and prosthetic systems combining these component
Potential Optimal Gait Performance of Mauch S-N-S Prosthetic Knee Configurations as Predicted by Dynamic Modeling
Patients with prosthetic legs routinely suffer from abnormal gait patterns which can cause health issues and eventually lower the quality of their lives. Despite the half-century advance in the technology of prosthetic knees, from the purely mechanical to microprocessor controlled systems, patient testing suggests that very little progress has been made in the quality of the kinetics and kinematics of amputee gait. Moreover, the cost of microprocessor controlled prosthetic knees may be 10 times more than the purely mechanical knees. While prosthetic knees have become more complex and expensive, it is not proven that the prosthetic knee is a central factor limiting amputee patient gait. The goal of this project is to determine the degree to which the Mauch S-N-S prosthetic knee limits the ability of a subject to achieve a close to normal gait pattern. In this research, we developed dynamic models of the Mauch S-N-S prosthetic knee based on gait-like motion tests of a Mauch knee cylinder and used the dynamic models in computational simulations to determine the best achievable gait, on the basis of obtaining near-to-normal gait kinematics and kinetics. Idealized assumptions were made for patient performance capability and characteristics of the other prosthetic leg components, to obtain the desired focus on knee capabilities and limitations. The results indicate that even with this relatively old technology prosthetic knee, subjects have the potential to walk much more normally than the patient-test data indicates. An extension of the study showed the significant interaction of the prosthetic knee and ankle with respect to achieving optimal gait. The methodology of this study can be applied to evaluation other knees, prosthetic components and prosthetic systems combining these component
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A Generalized Method for Predictive Simulation-Based Lower Limb Prosthesis Design
Lower limb prostheses are designed to replace the functions and form of the missing biological anatomy. These functions are hypothesized to improve user outcome measures which are negatively affected by receiving an amputation – such as metabolic cost of transport, preferred walking speed, and perceived discomfort during walking. However, the effect of these design functions on the targeted outcome measures is highly variable, suggesting that these relationships are not fully understood. Biomechanics simulation and modeling tools are increasingly capable of analyzing the effects of a design on the resulting user gait. In this work, prothesis-aided gait is optimized in simulation to reduce both muscle effort and peak loads on the residual limb using a generalized prosthesis model. Compared to a traditional revolute powered ankle joint model, a two degree-of freedom generalized model reduced muscle activations by 50% and peak loads by 15%. Simulated prosthesis behaviors corresponding to the optimal gait patterns were translated into a two degree-of-freedom ankle-foot prosthesis design with powered bidirectional linear translation and plantarflexion. The prototype is capable of delivering up to 171 N-m of plantarflexion torque and 499 N of translation force, with 15° dorsi-/35° plantarflexion and 10 cm translation range of motion. The mass and height of the ankle-foot are 2.29 kg and 19.5 cm, respectively. The mass of the entire system including the wearable offboard system is 8.58 kg. This platform is designed to emulate the behavior of the simulated prosthesis, as well as be configurable to emulate alternate behaviors obtained from simulations with different optimization objectives. The prototype is controlled to replicate simulated walking patterns using a high level finite state controller, mid-level stiffness controller, and low level load controller. Closed loop load control has bandwidth of 15 Hz in translation and 7.2 Hz in flexion. Load tracking during walking with a single able-bodied human subject ranges from 93 to 159 N in translation and 4.6 to 21.3 N-m in flexion. The contribution of this work is to provide a framework for predictive simulation-based prosthesis design, evidence of its practical implementation, and the experimental tools to validate future predictive simulation studies
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A Lower Limb Prosthesis with Active Alignment for Reduced Limb Loading
Over the past decade, the growing field of robotics has created new possibilities in lower limb prostheses. The focus of these new prostheses has been replicating the dynamics of the lost limb in order to restore gait of individuals with lower limb amputations to healthy norms. This places demanding loads on the residual limb. Compensation by the rest of body is high, causes overloading of intact joints and can lead to deterioration of mobility and overall health. Abnormalities remain present in the person’s gait, stemming from the loading of soft tissue and the altered anatomy of the affected limb. In this dissertation, an experimental prosthesis is developed with systematic, simulation based techniques. Kinematics and kinetics of the prosthesis design are altered in order to actively realign the limb in relation to the center of pressure during stance, allowing positive power to be generated by the prosthesis while actively reducing the magnitude of the sagittal moment transferred to the residual limb. Initial findings show that during walking with the experimental device compared to a daily use prosthesis, peak pressures on the residual limb are lowered by over 10% while maintaining walking speed
A review of energy storing prosthetic feet and computer aided structural optimization of a below-knee prosthesis
Because people with physical disabilities have shown an interest in participation in sports, a new class of prosthetic feet known as energy storing prosthetic feet has been developed. These new developments in prosthetic foot design utilize energy storage and return to improve ambulation. This thesis reviews the design, materials, advantages and disadvantages of various energy storing prosthetic feet. Research studies, comparing gait in below-knee amputees using different prosthetic designs, can be applied to the design of prosthetic feet that are lighter, stronger and more reliable. Comparisions among these feet are reviewed in the context of functional capability and patient satisfaction. This study indicates a significant improvement in the amputees overall function with the use of energy storing prosthetic feet compared to the conventional feet.
In this thesis, a model of a below-knee prosthesis is constructed and its response to two different loading conditions studied by finite element stress analysis using the Computer Aided Engineering package of IDEAS. The main criterion in the design of a prosthesis is a balance between minimizing stress and weight, for a required level of functional capability. The effect of different geometry, material properties and loading conditions on minimizing the weight of the prosthesis and on stress distribution within the prosthesis is determined. An optimal prosthesis with minimum weight is designed for use by geriatric amputees
Design and Analysis of Novel Actuation Mechanism with Controllable Stiffness
Actuators intended for human–machine interaction systems are usually designed to be mechanically compliant. Conventional actuators are not suitable for this purpose due to typically high stiffness. Advanced powered prosthetic and orthotic devices can vary their stiffness during a motion cycle and are power-efficient. This paper proposes a novel actuator design that modulates stiffness by means of a flexible beam. A motorized drive system varies the active length of the cantilever beam, thus achieving stiffness modulation. New large deflection formulation for cantilever beams with rolling contact constraints is used to determine the moment produced by the actuator. To validate the proposed solution method, an experiment was performed to measure large static deformations of a cantilever beam with the same boundary conditions as in the actuator design. The experiments indicate excellent agreement between measured and calculated contact forces between beam and roller, from which the actuator moment is determined
The Effects of the Inertial Properties of Above-Knee Prostheses on Optimal Stiffness, Damping, and Engagement Parameters of Passive Prosthetic Knees
Our research aims to design low-cost, high-performance, passive prosthetic knees for developing countries. In this study, we determine optimal stiffness, damping, and engagement parameters for a low-cost, passive prosthetic knee that consists of simple mechanical elements and may enable users to walk with the normative kinematics of able-bodied humans. Knee joint power was analyzed to divide gait into energy-based phases and select mechanical components for each phase. The behavior of each component was described with a polynomial function, and the coefficients and polynomial order of each function were optimized to reproduce the knee moments required for normative kinematics of able-bodied humans. Sensitivity of coefficients to prosthesis mass was also investigated. The knee moments required for prosthesis users to walk with able-bodied normative kinematics were accurately reproduced with a mechanical system consisting of a linear spring, two constant-friction dampers, and three clutches (R[superscript 2]=0.90 for a typical prosthetic leg). Alterations in upper leg, lower leg, and foot mass had a large influence on optimal coefficients, changing damping coefficients by up to 180%. Critical results are reported through parametric illustrations that can be used by designers of prostheses to select optimal components for a prosthetic knee based on the inertial properties of the amputee and his or her prosthetic leg
Design and Prototyping of a Shape-changing Rigid-body Human Foot in Gait
Traditional ankle-foot prostheses often replicate the physiological change in shape of the foot during gait via compliant mechanisms. In comparison, rigid-body feet tend to be simplistic and largely incapable of accurately representing the geometry of the human foot. Multi-segment rigid-body devices offer certain advantages over compliant mechanisms which may be desirable in the design of ankle-foot devices, including the ability to withstand greater loading, the ability to achieve more drastic shape-change, and the ability to be synthesized from their kinematics, allowing for realistic functionality without prior accounting of the complex internal kinetics of the foot. This work focuses on applying methodology of shape-changing kinematic synthesis to design and prototype a multi-segment rigid-body foot device capable of matching the dynamic change in shape of a human foot in gait. Included are discussions of an actuation strategy, mechanical design considerations, limitations, and potential prosthetic design implications of such a foot
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Design and Additive Fabrication of Foot and Ankle-Foot Orthoses
Foot and ankle-foot orthoses are prescribed in order to promote mobility through supporting
and/or realigning the lower leg and alleviating pain in the foot in different parts of the gait
cycle. This paper will outline new approaches to the design and manufacture of personalised
foot and ankle-foot orthoses (FO and AFO) using additive fabrication technology. The
research is addressing the need for specific software design tools for orthosis design which
enable their properties to be locally tailored within a mass customisation framework.
Structure/material testing to support that activity is also being undertaken and will be
described.Mechanical Engineerin
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