Optimal Placement of Triaxial Accelerometers for Modal Vibration Tests

Proper pretest planning is a vital component of any successful vibration test. An extremely important part of the pretest exercise is the placement of sensors, usually in the form of accelerometers. The accelerometers must be placed such that all of the important dynamic information is obtained during the course of the test. The resulting sensor configuration must be optimal in some sense such that test resources are conserved. The state-of-the-practice is to select individual sensor location/directions from a candidate set based upon one of several available criteria. Triaxial accelerometers are then placed at the corresponding locations. In general, this results in the non-optimal placement of many of the accelerometers. This paper presents a new technique, based upon Effective Independence, that places triaxial accelerometers as single units in an optimal fashion. The technique is applied and compared with standard approaches using the X-33 vehicle.