Indirect Measurement of the Inertia Properties of a Knee Prosthesis Through a Simple Frequency-Domain Technique

2009 ◽  
Vol 3 (4) ◽  
Author(s):  
Emiliano Mucchi ◽  
Giuliamarta Bottoni ◽  
Raffaele Di Gregorio
Keyword(s):  
Medical Devices ◽  
Frequency Response Function ◽  
Knee Prosthesis ◽  
Indirect Measurement ◽  
Measurement Sensitivity ◽  
Fast Evaluation ◽  
Transfemoral Amputees ◽  
Inertia Properties ◽  
Inertia Forces ◽  
Body Inertia

The dynamic study of humans carrying prostheses requires the rigid-body inertia properties of the prostheses. Since such properties are difficult to evaluate, in general, roughly estimated values of these quantities are used. These approximations may yield significant errors in the evaluation of some dynamic quantities (i.e., the inertia forces due to the prosthesis). This work is addressed to assess an experimental technique, based on frequency response function measurements, that indirectly measures the inertia properties of prostheses for transfemoral amputees. First, a specifically designed specimen and, then, a real prosthesis are tested for assessing the proposed technique. The results are that the measurement sensitivity is 0.002 kg m2 for inertia-tensor entries and 3 mm for center-of-gravity coordinates. Thus, the proposed technique is effective for a precise and fast evaluation of the inertia properties of medical devices such as prostheses.

Rigid Body Inertia Properties

2021 ◽  
Vol 63 (9) ◽  
pp. 1483-1489
Author(s):  
T. B. Goldvarg ◽  
V. N. Shapovalov
Keyword(s):  
Rigid Body ◽  
Inertia Properties ◽  
Body Inertia

Impact of stance phase microprocessor-controlled knee prosthesis on ramp negotiation and community walking function in K2 level transfemoral amputees

2012 ◽  
Vol 36 (1) ◽  
pp. 95-104 ◽  
Author(s):  
Judith M Burnfield ◽  
Valerie J Eberly ◽  
JoAnne K Gronely ◽  
Jacquelin Perry ◽  
William Jared Yule ◽  
...  
Keyword(s):  
Stance Phase ◽  
Knee Prosthesis ◽  
Timed Up And Go ◽  
Safety Function ◽  
Peak Knee ◽  
Transfemoral Amputees ◽  
Single Limb Support ◽  
Improved Function ◽  
And Function ◽  
Prosthetic Knees

Background: Microprocessor controlled prosthetic knees (MPK) offer opportunities for improved walking stability and function, but some devices’ swing phase features may exceed needs of users with invariable cadence. One MPK offers computerized control of only stance (C-Leg Compact). Objective: To assess Medicare Functional Classification Level K2 walkers’ ramp negotiation performance, function and balance while using a non-MPK (NMPK) compared to the C-Leg Compact. Study Design: Crossover. Methods: Gait while ascending and descending a ramp (stride characteristics, kinematics, electromyography) and function were assessed in participant’s existing NMPK and again in the C-Leg Compact following accommodation. Results: Ramp ascent and descent were markedly faster in the C-Leg Compact compared to the NMPK ( p ≤ 0.006), owing to increases in stride length ( p ≤ 0.020) and cadence ( p ≤ 0.020). Residual limb peak knee flexion and ankle dorsiflexion were significantly greater (12.9° and 4.9° more, respectively) during single limb support while using the C-Leg Compact to descend ramps. Electromyography (mean, peak) did not differ significantly between prosthesis. Function improved in the C-Leg Compact as evidenced by a significantly faster Timed Up and Go and higher functional questionnaire scores. Conclusions: Transfemoral K2 walkers exhibited significantly improved function and balance while using the stance-phase only MPK compared to their traditional NMPK. Clinical relevance Instability, reduced function and falls are common in deconditioned transfemoral amputees. Selection and use of prosthetic componentry that promotes greater stability in more challenging environments is essential to improve the safety, function, quality of life and independence of individuals functioning at the K2 walking level.

Finite Element Incremental Approach and Exact Rigid Body Inertia

1996 ◽  
Vol 118 (2) ◽  
pp. 171-178 ◽  
Author(s):  
A. A. Shabana
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Rigid Bodies ◽  
Simple Expression ◽  
Shape Functions ◽  
Large Rotation ◽  
Nodal Coordinates ◽  
Inertia Properties ◽  
Element Shape ◽  
Body Inertia

In the dynamics of multibody systems that consist of interconnected rigid and deformable bodies, it is desirable to have a formulation that preserves the exactness of the rigid body inertia. As demonstrated in this paper, the incremental finite element approach, which is often used to solve large rotation problems, does not lead to the exact inertia of simple structures when they rotate as rigid bodies. Nonetheless, the exact inertia properties, such as the mass moments of inertia and the moments of mass, of the rigid bodies can be obtained using the finite element shape functions that describe large rigid body translations by introducing an intermediate element coordinate system. The results of application of the parallel axis theorem can be obtained using the finite element shape functions by simply changing the element nodal coordinates. As demonstrated in this investigation, the exact rigid body inertia properties in case of rigid body rotations can be obtained using the shape function if the nodal coordinates are defined using trigonometric functions. The analysis presented in this paper also demonstrates that a simple expression for the kinetic energy can be obtained for flexible bodies that undergo large displacements without the need for interpolation of large rotation coordinates.

scholarly journals Interactions Between Transfemoral Amputees and a Powered Knee Prosthesis During Load Carriage

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Andrea Brandt ◽  
Yue Wen ◽  
Ming Liu ◽  
Jonathan Stallings ◽  
He Helen Huang
Keyword(s):  
Knee Prosthesis ◽  
Load Carriage ◽  
Transfemoral Amputees

Absolute Nodal Coordinate Formulation

1997 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Hussien A. Hussien ◽  
José L. Escalona
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Rigid Bodies ◽  
Rotation Vector ◽  
Finite Rotations ◽  
Large Rotation ◽  
Finite Element Procedure ◽  
Floating Frame ◽  
Inertia Forces ◽  
Body Inertia

Abstract There are three basic finite element formulations, which are used in multibody dynamics. These are the floating frame reference approach, the incremental method and the large rotation vector approach. In the floating frame of reference and incremental formulations, the slopes are assumed small in order to define infinitesimal rotations that can be treated and transformed as vectors. This description, however, limits the use of some important elements such as beams and plates in a wide range of large displacement applications. As demonstrated in some recent publications, if infinitesimal rotations are used as nodal coordinates, the use of the finite element incremental formulation in the large reference displacement analysis does not lead to exact modeling of the rigid body inertia when the structures rotate as rigid bodies. In this paper, a new and simple finite element procedure that employs the mathematical definition of the slope and uses it to define the element coordinates instead of the infinitesimal and finite rotations is developed for large rotation and deformation problems. By using this description and by defining the element coordinates in the global system, not only the need for performing coordinate transformation is avoided, but also a simple expression for the inertia forces is obtained. Furthermore, the resulting mass matrix is constant and it is the same matrix that appears in linear structural dynamics. It is demonstrated in this paper, that this coordinate description leads to exact modeling of the rigid body inertia when the structure rotate as rigid bodies. Nonetheless, the stiffness matrix becomes nonlinear function of time even in the case of small displacements. The method presented in this paper differs from previous large rotation vector formulations in the sense that the inertia forces, the kinetic energy, and the strain energy are not expressed in terms of any orientation coordinates, and therefore, the method does not require interpolation of finite rotations. While the use of the formulation is demonstrated using a simple planar beam element, the generalization of the method to other element types and to the three dimensional case is straightforward. Using the finite element procedure presented in this paper, beams and plates can be treated as isoparametric elements.

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