Experimental Identification of Rigid Body Inertia Properties Using Low-Frequency Unbalance Excitation

2009 ◽  
Author(s):  
Robert Kloepper ◽  
Hiraku Sakamoto ◽  
Masaaki Okuma
Keyword(s):  
Rigid Body ◽  
Low Frequency ◽  
Experimental Identification ◽  
Inertia Properties ◽  
Body Inertia

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

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 Experimental Determination of Rigid Body Properties: An Evaluation on the Use of Piezoelectric or MEMS Tri-Axial Accelerometers

2018 ◽  
Vol 148 ◽  
pp. 01003 ◽  
Author(s):  
António Urgueira ◽  
Nuno Venâncio ◽  
Pedro Riscado ◽  
Raquel Almeida ◽  
Tiago Silva
Keyword(s):  
Rigid Body ◽  
Experimental Determination ◽  
Low Cost ◽  
Low Frequency ◽  
The Body ◽  
Identification Algorithm ◽  
Inertia Properties ◽  
Areas Of Interest ◽  
New Sensors

The development of new sensors that are available at more accessible prices may lead to the spread of their use on common studies in structural dynamics. One of areas of interest is the experimental determination of rigid body properties that are mandatory when the vibration response is to be calculated at low frequency ranges. In this work, a comparison of the experimental determination of rigid body properties is carried out to evaluate the performance of the commonly used tri-axial piezoelectric accelerometers and their equivalent MEMS sensors. Although their prices are quite different, both sensors can measure the inertia restraint line that is related to the inertia properties of the tested object. An identification algorithm is applied to the frequency response functions obtained by using both sensors, leading to the estimation of the body mass value, as well as the three coordinates of the centre of mass and the six elements of the inertia tensor. An experimental example supports the use of the referred low-cost sensors.

Finite Element Incremental Approach and Exact Rigid Body Inertia

1995 ◽  
Author(s):  
A. A. Shabana
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Shape Function ◽  
Rigid Bodies ◽  
Shape Functions ◽  
Mass Moment ◽  
Nodal Coordinates ◽  
Inertia Properties ◽  
Element Shape ◽  
Body Inertia

Abstract 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 because the physical nodal coordinates can not be used to describe large rotations in the case of beams and plates. 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. A simple rigid body rotation, however, can cause a significant error if the element shape function and the nodal coordinates are used to evaluate the inertia properties of bodies that undergo large rigid body rotations. 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 that lack a physical meaning. Linearization of the nodal coordinate vector can lead to different results when different methods are used to define the rigid body inertia. For example, the calculation of the mass moment of inertia using position coordinates only leads to results which are different from those obtained using energy expressions or the laws of motion.

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