Development of a high accuracy and high sampling rate displacement sensor for civil engineering structures monitoring

Abstract

Displacement is one of the key physical quantities that are necessary to understand characteristics and behaviours of civil engineering structures. In this study, a new displacement sensor module is developed by integrating GPS-RTK and accelerometer sensors into a single unit so that dynamic and pseudo-static displacements of various civil engineering structures can be measured with high accuracy, precision and sampling rate. Displacement is estimated by fusing GPS-RTK and accelerometer measurements using a two-stage Kalman filter. The two-stage Kalman filter improves accuracy, precision, and sampling rate by recursively integrating the acceleration measured by the accelerometer and correcting the integration error using the displacement intermittently measured from the GPS-RTK sensor. The proposed displacement sensor offers the following advantages over the existing GPS-RTK sensors commonly used for civil engineering structures monitoring: (1) The proposed displacement sensor can achieve a better accuracy (around 2 mm) and a better sampling rate (up to 100 Hz) compared to the conventional GPS-RTK sensors, and (2) The performance is less affected by weather conditions, multipath problems and signal blockage, which typically deteriorate the performance of conventional GPS-RTK sensors. To validate the performance of the proposed displacement sensor, a series of lab scale tests were conducted.