scholarly journals A reduced order computational model of a semi-active variable-stiffness foot prosthesis

2020 ◽  
Author(s):  
Michael McGeehan ◽  
Peter Adamczyk ◽  
Kieran Nichols ◽  
Michael Hahn
Keyword(s):  
Body Weight ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Performance Standard ◽  
Design Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Lumped Parameter ◽  
Contact Models

INTRODUCTION: Passive energy storage and return (ESR) feet are the current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. METHODS: The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. RESULTS: Stiffness of the model matched that of the physical VSF (R2: 0.98, RMSE: 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched well under optimized parameter conditions (R2: 0.98, RMSE: 5.3% body weight,) and unoptimized parameter conditions (R2: 0.90, mean RMSE: 13% body weight). Anterior-posterior center of pressure matched well with R2 > 0.94 and RMSE < 9.5% foot length in all conditions. CONCLUSIONS: The ESR properties of the VSF were accurately simulated under benchtop testing and dynamic gait conditions. These methods may be useful for predicting GRFR arising from gait with novel prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals A Reduced-Order Computational Model of a Semi-Active Variable-Stiffness Foot Prosthesis

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Michael A. McGeehan ◽  
Peter G. Adamczyk ◽  
Kieran M. Nichols ◽  
Michael E. Hahn
Keyword(s):  
Body Weight ◽  
Mean Squared Error ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Performance Standard ◽  
Design Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Lumped Parameter

Abstract Passive energy storage and return (ESR) feet are current performance standard in lower limb prostheses. A recently developed semi-active variable-stiffness foot (VSF) prosthesis balances the simplicity of a passive ESR device with the adaptability of a powered design. The purpose of this study was to model and simulate the ESR properties of the VSF prosthesis. The ESR properties of the VSF were modeled as a lumped parameter overhung beam. The overhung length is variable, allowing the model to exhibit variable ESR stiffness. Foot-ground contact was modeled using sphere-to-plane contact models. Contact parameters were optimized to represent the geometry and dynamics of the VSF and its foam base. Static compression tests and gait were simulated. Simulation outcomes were compared to corresponding experimental data. Stiffness of the model matched that of the physical VSF (R2: 0.98, root-mean-squared error (RMSE): 1.37 N/mm). Model-predicted resultant ground reaction force (GRFR) matched well under optimized parameter conditions (R2: 0.98, RMSE: 5.3% body weight,) and unoptimized parameter conditions (R2: 0.90, mean RMSE: 13% body weight). Anterior–posterior center of pressure matched well with R2 > 0.94 and RMSE < 9.5% foot length in all conditions. The ESR properties of the VSF were accurately simulated under benchtop testing and dynamic gait conditions. These methods may be useful for predicting GRFR arising from gait with novel prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals A computational gait model with a below-knee amputation and a semi-active variable-stiffness foot prosthesis

2021 ◽  
Author(s):  
Michael McGeehan
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Contact Forces ◽  
Prosthesis Design ◽  
Limb Loss ◽  
Design Parameters ◽  
Knee Amputation ◽  
Musculoskeletal Models

Introduction: Simulations based on computational musculoskeletal models are powerful tools for evaluating the effects of potential biomechanical interventions, such as implementing a novel prosthesis. However, the utility of simulations to evaluate the effects of varied prosthesis design parameters on gait mechanics has not been fully realized due to lack of a readily-available limb loss-specific gait model and methods for efficiently modeling the energy storage and return dynamics of passive foot prostheses. The purpose of this study was to develop and validate a forward simulation-capable gait model with lower limb loss and a semi-active variable-stiffness foot (VSF) prosthesis. Methods: A seven-segment 28-DoF gait model was developed and forward kinematics simulations, in which experimentally-observed joint kinematics were applied and the resulting contact forces under the prosthesis evolved accordingly, were computed for four subjects with unilateral below-knee amputation walking with a VSF. Results: Model-predicted resultant ground reaction force (GRFR) matched well under trial-specific optimized parameter conditions (mean R2: 0.97, RMSE: 7.7% body weight (BW)) and unoptimized (subject-specific, but not trial-specific) parameter conditions (mean R2: 0.93, RMSE: 12% BW). Simulated anterior-posterior center of pressure demonstrated a mean R2 = 0.64 and RMSE = 14% foot length. Simulated kinematics remained consistent with input data (0.23 deg RMSE, R2 > 0.99) for all conditions. Conclusions: These methods may be useful for simulating gait among individuals with lower limb loss and predicting GRFR arising from gait with novel VSF prostheses. Such data are useful to optimize prosthesis design parameters on a user-specific basis.

scholarly journals A Computational Gait Model with a Below-Knee Amputation and a Semi-Active Variable-Stiffness Foot Prosthesis

2021 ◽  
Author(s):  
Michael McGeehan ◽  
Peter Adamczyk ◽  
Kieran Nichols ◽  
Michael E. Hahn
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Variable Stiffness ◽  
Contact Forces ◽  
Prosthesis Design ◽  
Limb Loss ◽  
Design Parameters ◽  
Knee Amputation ◽  
Musculoskeletal Models

Abstract Introduction: Simulations based on computational musculoskeletal models are powerful tools for evaluating effects of potential biomechanical interventions, such as implementing a novel prosthesis. However, the utility of simulations to evaluate effects of prosthesis design parameters on gait mechanics has not been fully realized due to lack of a readily-available limb loss-specific gait model and methods for efficiently modeling the energy storage and return dynamics of passive foot prostheses. The purpose of this study was to develop and validate a forward simulation-capable gait model with lower limb loss and a semi-active variable-stiffness foot (VSF) prosthesis. Methods: A seven-segment 28-DoF gait model was developed and forward kinematics simulations, in which experimentally-observed joint kinematics were applied and resulting foot contact forces evolved accordingly, were computed for four subjects with unilateral below-knee amputation walking with a VSF. Results: Model-predicted resultant ground reaction force (GRFR) matched well under trial-specific optimized parameter conditions (mean R2: 0.97, RMSE: 7.7% body weight (BW)) and unoptimized (subject-specific, not trial-specific) parameter conditions (mean R2: 0.93, RMSE: 12% BW). Simulated anterior-posterior center of pressure demonstrated mean R2 = 0.64 and RMSE = 14% foot length. Simulated kinematics remained consistent with input data (0.23 deg RMSE, R2 > 0.99) for all conditions. Conclusions: These methods may be useful for simulating gait of individuals with lower limb loss and predicting GRFR with novel VSF prostheses. Such data are useful to optimize user-specific prosthesis design parameters.

Numerical analysis of mechanical properties of 3D printed aluminium components with variable core infill values

2020 ◽  
Vol 1 (103) ◽  
pp. 16-24
Author(s):  
P. Baras ◽  
J. Sawicki
Keyword(s):  
Numerical Analysis ◽  
Mechanical Strength ◽  
Reference Model ◽  
Reaction Force ◽  
Solid Material ◽  
Solid Core ◽  
Compression Tests ◽  
Element Analysis ◽  
Static Compression ◽  
3D Printed

Purpose: The purpose of this paper is to present numerical modelling results for 3D-printed aluminium components with different variable core infill values. Information published in this paper will guide engineers when designing the components with core infill regions. Design/methodology/approach: During this study 3 different core types (Gyroid, Schwarz P and Schwarz D) and different combinations of their parameters were examined numerically, using FEM by means of the software ANSYS Workbench 2019 R2. Influence of core type as well as its parameters on 3D printed components strength was studied. The “best” core type with the “best” combination of parameters was chosen. Findings: Results obtained from the numerical static compression tests distinctly showed that component strength is highly influenced by the type infill choice selected. Specifically, infill parameters and the coefficient (force reaction/volumetric percentage solid material) were investigated. Resulting total reaction force and percentage of solid material in the component were compared to the fully solid reference model. Research limitations/implications: Based on the Finite Element Analysis carried out in this work, it was found that results highlighted the optimal infill condition defined as the lowest amount of material theoretically used, whilst assuring sufficient mechanical strength. The best results were obtained by Schwarz D core type samples. Practical implications: In the case of the aviation or automotive industry, very high strength of manufactured elements along with a simultaneous reduction of their wight is extremely important. As the viability of additively manufactured parts continues to increase, traditionally manufactured components are continually being replaced with 3D-printed components. The parts produced by additive manufacturing do not have the solid core, they are rather filled with specific geometrical patterns. The reason of such operation is to save the material and, in this way, also weight. Originality/value: The conducted numerical analysis allowed to determine the most favourable parameters for optimal core infill configurations for aluminium 3D printed parts, taking into account the lowest amount of material theoretically used, whilst assuring sufficient mechanical strength.

CLINICAL GAIT ANALYSIS OF SUBJECTS WITH TRANS-FEMORAL AMPUTATION USING POLYCENTRIC FOUR-BAR LINKAGE PROSTHETIC KNEE JOINT

2020 ◽  
Vol 20 (05) ◽  
pp. 2050021
Author(s):  
RAJESH KUMAR MOHANTY ◽  
STHIRPRANJYAN BISWAL ◽  
PABITRA KUMAR SAHOO ◽  
SAKTI PRASAD DAS ◽  
R. C. MOHANTY ◽  
...  
Keyword(s):  
Body Weight ◽  
Gait Analysis ◽  
Reaction Force ◽  
Vertical Component ◽  
Normal Subjects ◽  
Design Parameters ◽  
Gait Performance ◽  
Prosthetic Knee ◽  
Significant Difference ◽  
Four Bar Linkage

Background: Adequate research is not reported so far to underline the influence of commonly used polycentric knee joints on gait performance of subjects with trans-femoral amputation. Objective: The intent of this investigation is to analyze prosthetic gait of unilateral traumatic trans-femoral amputees with polycentric four-bar linkage knee and compare it with normal subjects for evaluating any asymmetry in gait performance. Methods: Objective three-dimensional gait analysis of 15 subjects [mean (age): 36.4 (10.7) years] were performed in gait lab through force plate and optoelectronic devices to measure temporal-spatial parameters, kinematic and kinetic performances. Gait patterns of amputees were compared with those of 15 individuals with normal gait to analyze distinct functionalities of existing polycentric knee. Results: Asymmetry in gait was observed between amputees and normal subjects for all variables concerned ([Formula: see text]). Amputee gait was with significantly lesser velocity, cadence with shorter step and stride length. There was significantly less hip, knee and pelvic motions, however, pelvic obliquity and rotation did not show significant difference from the normal subjects. The vertical component of the ground reaction force differed significantly between prosthetic and intact limb [49.7 (8.5)% and 90.4 (7.4)% body weight] and also from normal subjects [107.5 (2.4)% body weight] during stance ([Formula: see text]). Interpretation and Conclusion: This difference may be attributed to nonproportionate loading of limbs and mechanical adaptations for counteracting deficiencies of prosthetic side. This study will help to explain gait asymmetry in trans-femoral amputees and to identify underlying mechanisms to enhance the quality of the existing design of prosthetic knee through optimizing design parameters and utilizing appropriate materials.

scholarly journals Investigation and Statistical Modeling of the Mechanical Properties of Additively Manufactured Lattices

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3962
Author(s):  
Derek G. Spear ◽  
Anthony N. Palazotto
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Design Parameters ◽  
Statistical Experimental Design ◽  
Lattice Structures ◽  
Compression Tests ◽  
Static Compression ◽  
Interaction Terms ◽  
Cell Densities ◽  
The Impact

This paper describes the background, test methodology, and experimental results associated with the testing and analysis of quasi-static compression testing of additively manufactured open-cell lattice structures. The study aims to examine the effect of lattice topology, cell size, cell density, and surface thickness on the mechanical properties of lattice structures. Three lattice designs were chosen, the Diamond, I-WP, and Primitive Triply Periodic Minimal Surfaces (TPMSs). Uniaxial compression tests were conducted for every combination of the three lattice designs, three cell sizes, three cell densities, and three surface thicknesses. In order to perform an efficient experiment and gain the most information possible, a four-factor statistical experimental design was planned and followed throughout testing. A full four-factor statistical model was produced, along with a reduced interactions model, separating the model by the significance of each factor and interaction terms. The impact of each factor was analyzed and interpreted from the resulting data, and then conclusions were made about the effects of the design parameters on the resultant mechanical performance.

scholarly journals Development of a Subject-Specific Foot-Ground Contact Model for Walking

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Jennifer N. Jackson ◽  
Chris J. Hass ◽  
Benjamin J. Fregly
Keyword(s):  
Center Of Pressure ◽  
Reaction Force ◽  
Walking Ability ◽  
Vertical Force ◽  
Ground Contact ◽  
Contact Pattern ◽  
Flexion Extension ◽  
Subject Specific ◽  
Contact Models ◽  
Force Components

Computational walking simulations could facilitate the development of improved treatments for clinical conditions affecting walking ability. Since an effective treatment is likely to change a patient's foot-ground contact pattern and timing, such simulations should ideally utilize deformable foot-ground contact models tailored to the patient's foot anatomy and footwear. However, no study has reported a deformable modeling approach that can reproduce all six ground reaction quantities (expressed as three reaction force components, two center of pressure (CoP) coordinates, and a free reaction moment) for an individual subject during walking. This study proposes such an approach for use in predictive optimizations of walking. To minimize complexity, we modeled each foot as two rigid segments—a hindfoot (HF) segment and a forefoot (FF) segment—connected by a pin joint representing the toes flexion–extension axis. Ground reaction forces (GRFs) and moments acting on each segment were generated by a grid of linear springs with nonlinear damping and Coulomb friction spread across the bottom of each segment. The stiffness and damping of each spring and common friction parameter values for all springs were calibrated for both feet simultaneously via a novel three-stage optimization process that used motion capture and ground reaction data collected from a single walking trial. The sequential three-stage process involved matching (1) the vertical force component, (2) all three force components, and finally (3) all six ground reaction quantities. The calibrated model was tested using four additional walking trials excluded from calibration. With only small changes in input kinematics, the calibrated model reproduced all six ground reaction quantities closely (root mean square (RMS) errors less than 13 N for all three forces, 25 mm for anterior–posterior (AP) CoP, 8 mm for medial–lateral (ML) CoP, and 2 N·m for the free moment) for both feet in all walking trials. The largest errors in AP CoP occurred at the beginning and end of stance phase when the vertical ground reaction force (vGRF) was small. Subject-specific deformable foot-ground contact models created using this approach should enable changes in foot-ground contact pattern to be predicted accurately by gait optimization studies, which may lead to improvements in personalized rehabilitation medicine.

The Effect of Magnetic Field on Magnetorheological Composites - Artificial Neural Network Based Modelling and Experiments

2015 ◽  
Vol 816 ◽  
pp. 327-336 ◽  
Author(s):  
Mateusz Kukla ◽  
Paweł Tarkowski ◽  
Jan Górecki ◽  
Ireneusz Malujda ◽  
Krzysztof Talaśka
Keyword(s):  
Neural Network ◽  
Magnetic Field ◽  
Mechanical Properties ◽  
Magnetic Flux ◽  
Design Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Magnetorheological Elastomers ◽  
Magnetic Strength ◽  
Set Up

Looking for new applications of the available materials, such as magnetorheological elastomers (MERs) is an important element of machine design process. To this end it is necessary to determine their fundamental mechanical properties, including Young’s modulus and shear modulus. These properties are determined experimentally by testing the material in compression, tension and shear. In the case of the analysed group of materials the above-mentioned constants depend, inter alia, on the parameters of magnetic field acting on them. Therefore, it is necessary to determine the character and the extent of variation of the mechanical properties as a function of the physical constants characterising the active magnetic field, namely magnetic flux and magnetic intensity (field strength).This paper presents the results of static compression tests carried out on magnetorheological elastomers. The parameters measured during the static compression test were force and displacement at a pre-set magnetic flux. The maximum strength of the induced magnetic field was limited by the design parameters of the test set-up. In order to determine the behaviour of the material at greater values of magnetic strength and flux the properties of a real material were modelled with a neural network. The simulation was carried out using a simple, one-layer neural network. The chosen network training approach was error backpropagation. This approach enables approximation and predicting of changes of the properties of the tested material. The output results will enable deriving an analytical model of the tested MREs.

The Effect of Work Boots on Knee Mechanics and the Center of Pressure at the Knee During Static Kneeling

2015 ◽  
Vol 31 (5) ◽  
pp. 363-369 ◽  
Author(s):  
Liana Tennant ◽  
David Kingston ◽  
Helen Chong ◽  
Stacey Acker
Keyword(s):  
Body Weight ◽  
Knee Joint ◽  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Force Plate ◽  
Knee Mechanics ◽  
Increased Risk ◽  
3D Motion Capture ◽  
Anterior Posterior

Occupational kneeling is associated with an increased risk for the development of knee osteoarthritis. Previous work studying occupational kneeling has neglected to account for the fact that in many industrial settings, workers are required to wear steeltoe work boots. Thus, the purpose of this study was to evaluate the effect of work boot wear on the center of pressure location of the ground reaction force, knee joint angle, and magnitude of the ground reaction force in a kneeling posture. Fifteen healthy males were fit with 3D motion capture markers and knelt statically over a force plate embedded in the floor. Using the tibial tuberosity as the point of reference, the center of pressure in shod condition was shifted significantly medially (on average 0.009 m [P = .005]) compared with the barefoot condition. The knee was significantly less internally rotated (shod: –12.5° vs. barefoot: –17.4° [P = .009]) and the anterior/posterior shear force was significantly greater in the shod condition (shod: 6.0% body weight vs. barefoot: 1.5% body weight [P = .002]). Therefore, wearing work boots alters the kneeling posture compared with barefoot kneeling, potentially loading different surfaces of the knee, as well as altering knee joint moments.

scholarly journals The Design and Simulation of a 16-Sensors Plantar Pressure Insole Layout for Different Applications: From Sports to Clinics, a Pilot Study

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1450
Author(s):  
Alfredo Ciniglio ◽  
Annamaria Guiotto ◽  
Fabiola Spolaor ◽  
Zimi Sawacha
Keyword(s):  
Pressure Distribution ◽  
Plantar Pressure ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Weight Lifting ◽  
Lower Limbs ◽  
Plantar Pressure Distribution ◽  
Drop Landing ◽  
Mean Pressure ◽  
Footwear Design

The quantification of plantar pressure distribution is widely done in the diagnosis of lower limbs deformities, gait analysis, footwear design, and sport applications. To date, a number of pressure insole layouts have been proposed, with different configurations according to their applications. The goal of this study is to assess the validity of a 16-sensors (1.5 × 1.5 cm) pressure insole to detect plantar pressure distribution during different tasks in the clinic and sport domains. The data of 39 healthy adults, acquired with a Pedar-X® system (Novel GmbH, Munich, Germany) during walking, weight lifting, and drop landing, were used to simulate the insole. The sensors were distributed by considering the location of the peak pressure on all trials: 4 on the hindfoot, 3 on the midfoot, and 9 on the forefoot. The following variables were computed with both systems and compared by estimating the Root Mean Square Error (RMSE): Peak/Mean Pressure, Ground Reaction Force (GRF), Center of Pressure (COP), the distance between COP and the origin, the Contact Area. The lowest (0.61%) and highest (82.4%) RMSE values were detected during gait on the medial-lateral COP and the GRF, respectively. This approach could be used for testing different layouts on various applications prior to production.

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