Force reconstruction using the sum of weighted accelerations technique -- Max-Flat procedure

Abstract

Thomas G. Came, Randy L. Mayas and Vesta I. Bateman .... _ i_ _ :!_ Sandia NationalLaboratories _. .... Albuquerque, NewMexico87185, USA ' _ i_ _ / ABSTRACT important design consideration. This would include payloador satelliteloads duringrocket launches[3]. Force reconstruction is a procedure in which the externally applied force is inferred from measured An applicationthat will be discussed as part of this structuralresponse ratherthan directlymeasured. In paper is the impact into a rigid barrier of a weapon a recently developed technique, the response system with an energy-absorbing nose. The nose acceleration time-histories are multiplied by scalar had been designed to absorb the energy of impact weights and summed to produce the reconstructed and to mitigate the shock to the interiorcomponents. force. This reconstruction is called the Sum of To evaluate the crush capabilityof the nose, impact Weighted Accelerations Technique (SWAT). One tests were performed, and the measured forcestep in the application of this technique is the displacement curve was compared to the design calculationof the appropriatescalar weights. In this objective. Figure 1 shows the weapon mass-mockup paper a new methodof estimatingthe weights, using with the energy absorbing nose hung from its launch measured frequency response function data, is rail and fixture. The mass-mockup was designed to developed and contrasted with the traditional SWAT have the same mass, center-of-mass, and momentmethod of inverting the mode-shape matrix. The of-inertia as the real weapon. Both axial and diagonal techniqueuses frequency responsefunctiondata, but impact tests of the nose were plannedso the mockis not based on deconvolution, up needed to possess the correct rigid-bodyinertiaas well as mass. Figure2 showsthe plasticdeformation This work was supported by the U. S. Department of '_ _,. Energy under contract No. DE-AC04-94AL85000. _,t _ ]L. __ c_ .Olr. _P_[J'i ;_; '} :" "H]_; D0/CUt_.Ft'4T J:_i.JIYLI,_ITF._ DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer er, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Minimal-Sensing, Passive Force Identification Techniques for a Composite Structural Missile Component

“…Equations (2) and (3) are used to indirectly estimate the forces acting on a structure in the frequency domain, but many other methods estimate the forces in the time domain [3][4][5][6][7]. This paper indirectly estimates forces in the frequency domain because of the ease of implementation of Eqs (2) and (3) and the wealth of reference material from previous investigations of indirect force estimation in the frequency domain [8][9][10][11][12][13][14].…”

Comparison of Inverse Structural Filter (ISF) and Sum of Weighted Accelerations (SWAT) Time Domain Force Identification Methods

“…The Sum of Weighted Accelerations Technique (SWAT) was presented by Carne et al [14], although the method had been developed previously by Gregory, Priddy and Smallwood [15,16]. It has been successfully applied to a number of systems [17][18][19].…”

“…In some cases the free, unforced response, which is a linear combination of the elastic mode shapes, can be used to generate an adequate spatial filter (i.e. the SWAT-TEEM algorithm [14,19]). One limitation of the SWAT algorithm is that it determines the equivalent forces and moments that, if applied at the center of mass, would cause the same acceleration of the center of mass, and does not identify the spatial distribution of the applied forces.…”

An Iterative Approach to Road/Profile Identification Utilizing Wavelet Parameterization

“…Furthermore, Steltzner and Kammer have developed an approach using a non-causal filtering technique [4]. Another interesting approach to the present study, is given [5]; the Sum of Weighted Accelerations Technique (SWAT). This method has the drawback of only identifying the applied loading in the center of mass of the structure.…”