Real-time Rotation Monitoring of Offshore Structures based on GNSS and Accelerometer Data Fusion

Monitoring rotation responses accurately of offshore structures under different environmental conditions is an important and challenging technical issues in ensuring the health conditions of structures. We present a novel method for achieving this by integration of collocated GNSS and accelerometer data. The development is based on parameterization of the rotation angles to connect the accelerometer reference frame and the GNSS reference frame. The approach combines GNSS time-differencing technique and accelerometer measurement, so that their complementary merits are inherited, enabling to simultaneously capture static and dynamic rotational responses without auxiliary information, such as local reference station. Validation using data collected in controlled vibration test and a large cross-sea bridge during heavy vehicles and typhoon excitations demonstrates the  high performance of our method in capturing high-rate and broadband velocities and rotations, which are important for understanding structural dynamic behavior yet are often overlooked. Results of controlled vibration test demonstrated that the accuracy of velocity responses was improved by about 70%, compared to GNSS-derived solutions. The time-frequency analysis reveals the integrated solution also extends the measurable frequency bandwidth and improves modal frequency identification compared to GNSS-only technique. Field tests show its superior ability to detect subtle both static and dynamic rotational responses, with the accuracy reaching 0.002°.