Sensor set expansion for modal vibration testing

Pretest planning is crucial to successful modal vibration testing. Sensor placement is one of the more important tasks performed during the pretest exercise. The accelerometers must be distributed such that all of the required dynamic information is obtained during the course of the vibration test. A new method for triaxial sensor set selection based on maximizing the determinant of the target mode information matrix is presented. Maximizing the determinant maximizes a combination of target mode signal strength and linear independence critical to both test-analysis correlation and modal identification. The method iteratively expands an initial set of sensors instead of iteratively reducing a large candidate set. In many cases, the candidate sensor set can have thousands of sensor locations. This change in approach can result in a dramatic reduction in the required computational effort. In addition, the new method allows a test engineer to specify a set of locations that they absolutely want to have in the final sensor configuration, and then optimally expand the initial set to the desired number of sensors. The initial sensor set can be as small as one triax. The work presented focuses on the selection of triaxial accelerometers as single units at nodes, but the method can be generalized to the selection of any number of sensors at each iteration.