| The design, theory and error analysis of a novel six-degree-of-freedom accelerometer sensor (SDOFA) are presented. The Rensselaer Polytechnic Institute' s Laboratory for Noise and Vibration Control Research prototype was developed over a period of six years. Originally conceived by Professor Henry A. Scarton, Dr. Warren C. Kennedy and Dr. Dian-Xue Wang in 1985-86, the SDOFA uses six translational accelerometers compactly arranged in a 30 gram 25.4 mm cube to measure simultaneously translational and rotational accelerations in three orthogonal directions. The exact theory of the SDOFA and procedures for calculating rotational as well as translational acceleration through the measured outputs of the six translational accelerometers are given. The sensitivity of the SDOFA is about 1 V/g for translational and 2 mV/rad/s{dollar}sp2{dollar} for rotational with a bandwidth of 10 Hz-1,000 Hz. The maximum shock range of the SDOFA is 5,000 g for translational shock and 3,000,000 rad/s{dollar}sp2{dollar} for rotational shock. The corresponding working ranges are {dollar}pm{dollar}10 g and 6,000 rad/s{dollar}sp2{dollar} with a resolution threshold of 0.001 g pk (linear), 0.62 rad/s{dollar}sp2{dollar} (angular). These results conclusively show that the SDOFA is able to simultaneously and accurately measure six accelerations at a point.; Experimentally, the derived theory of the SDOFA was confirmed by: (1) using a shaker and a reference accelerometer doing the calibration and the translational acceleration test; (2) using two different models of parallel translational sensors acting through different perpendicular distances and resulting in identical rotational acceleration; (3) using a free-free beam for modal testing and finite element analysis and resulting in successful data comparison with the analytical results; (4) utilizing the complex beam, free-free rectangular plate and an H frame analyze and finite element analysis, again comparing results with the SDOFA output.; The successful implementation of this multi-degree-of-freedom accelerometer sensor could be used in the field of experimental modal analysis to provide better information on mode shapes of any structure especially if rotational effects are important. The rotational-translational sensor can also be used as a more accurate vibration monitoring device for any industrial, transportation, or military application. |
