Structural displacement estimation through multi-rate fusion of accelerometer and RTK-GPS displacement and velocity measurements

Abstract

For civil infrastructure monitoring, RTK-GPS sensors are commonly used to measure dynamic displacement. However, these sensors have poor precision (around 0.5–5 cm in the vertical direction) and a low sampling rate (up to 20 Hz). Furthermore, both the accuracy and the precision of the RTK-GPS sensors deteriorate when signals from satellites are not properly received by the sensors due to multipath, bad weather, signal blockage, etc. In this study, a new dynamic displacement estimation method is proposed so that the accuracy, precision, and sampling rate of dynamic displacement can be improved by combining the acceleration measured by a force-feedback accelerometer and the velocity and displacement measured by a low-cost RTK-GPS sensor. The uncertainty levels in the displacement and velocity measured by the RTK-GPS sensor are evaluated based on the quality of the received satellite signals, and the measurement from the RTK-GPS sensor is fused with the acceleration measured from the accelerometer using a two-stage Kalman filter. The performance of the proposed method is validated through a series of lab-scale tests and a field test conducted on Yeongjong Grand Bridge in South Korea. In the tests, the accuracy of the estimated vertical displacement was about 2 mm, and displacement, velocity, and acceleration are all simultaneously estimated at a sampling rate of 100 Hz.