Dynamic testing of state of the art vertical reference units

The University of Rhode Island (URI) Department of Ocean Engineering has been developing the capability for evaluating performance of shipboard vertical reference systems. This has involved building a six sensor vertical reference unit (VRU) for comparison with commercial systems and an automated motion simulator platform (AMSP) to test this generic VRU against other commercial references including those using attitude sensing GPS for augmentation. The VRU blends the measurements from 3 fixed (or strapped down) accelerometers and 3 angular rate sensors by means of 20 bit Delta-Sigma A/D converters and an IBM PC compatible computer. The AMSP uses 3 two foot long stepper motor driven linear actuators to move a 4 by 8 foot horizontal platform under computer control in roll, pitch, heave, and surge at a variety of rates simulating real ship motion. This paper describes the development of the VRU and AMSP systems.