Mechanical System Simulations for Seismic Signature Modeling

In this paper we present seismic signature simulations using ground vibration inputs from highfidelity 3-D mechanical system models. Results for an M1A1 and T72 are discussed. By analyzing the simulated seismic signature data in conjunction with the spectral features associated with the vibrations of specific vehicle sprung and un-sprung components we are able to make unambiguous associations of seismic signal features with suspension elements, offering valuable insight into target classification. The development of a utility (“Tankmod”) to streamline creation of DADS tracked vehicle dynamic models for generating seismic signals was reported in 2000. A model of an M1A1 tank created using Tankmod was described. During the past year, two new models were created: a T72 tank and a BMP-2 armored personnel carrier. In addition, an improved vehicle speed/steer controller was developed. The new controller maintains realistic vehicle behavior by properly limiting drive sprocket torques and sprocket rotation for skid steering. Model inputs used in seismic signature modeling are in the form of time series of ground reaction force and absolute position for each track block. Seismic signatures are given for an M1A1 vehicle operating over a 230 m x 280 m terrain grid with vertical relief. To emphasize the signature aspects of the results, we use a homogeneous subsurface consistent with a glaciated soil. Seismic signatures are also given for M1A1 and T72 vehicles following similar straight-ahead path and speed profiles. Seismic spectrograms in the 20-60 Hz band clearly demonstrate harmonic families associated with the fundamental track-block passage rate and the target speed profile. Lower frequency seismic signal spectral peaks (below 5 Hz) are demonstrated in standard PSD spectra. We tentatively associate these low frequency peaks with the low frequency resonances observed in the vertical and pitch motions of the vehicle sprung mass (hull and turret). Spectral peaks in this frequency band will propagate for 10’s of kilometers and may serve as important target classification features. 1 Dynamic Analysis Design System (DADS), LMS International, CAE Division, Coralville, Iowa. 2 Lacombe, J., Moran, M. and S. Happel, “A 3-Dimensional Dynamics Model For Generating Tracked Vehicle Seismic Signals”, Proceedings, 2000 Meeting of the MSS Specialty Group on Battlefield Acoustic and Seismic Sensing, 440000-195-X (I), pp 377-383, Jan. 2001. Report Documentation Page Report Date 00 Oct 2001 Report Type N/A Dates Covered (from... to) Title and Subtitle Mechanical System Simulations for Seismic Signature Modeling Contract Number