Vibrometer Steering System for Dynamic In-flight Tracking and Measurement

A noncontact measurement system is developed for measuring lightweight flexible structures in motion by steering a vibrometer beam to a point on the structure located by videogrammetry. Triangulation of video data, videogrammetry, can capture large scale motion in near real-time, but has limited data collection rates and spatial resolution. Laser vibrometry can capture minute structural vibrations but requires precise alignment. This paper presents a method to register a vibrometry system within a videogrammetry system so that the vibrometer can be steered to sub-degree accuracy. Because videogrammetry is data intensive, there is some processing delay resulting in tracking error. By using a Kalman filter, dynamic tracking error can be reduced by half. Vibration results compared to baseline cases show no impairment to natural frequency measurement. The dynamic in-flight tracking and measurement system will allow testing of more sensitive structures such as flexible wing air vehicles or deployable space structures.