Dynamic Displacement Estimation of Bridge Using MIMO Radar Interferometry from an Oscillating Platform

A radar-based, non-contact, marker-less bridge dynamic displacement estimation approach from oscillating platforms is proposed. The proposed approach makes use of a multiple-input multiple-output (MIMO) radar device to generate two-dimensional (2D) images of the bridge at short time intervals, in combination with radar interferometry techniques. Additionally, we propose a novel dynamic motion error compensation (DMEC) process to compensate for platform-induced phase errors. The DMEC is a data-driven approach that does not require any auxiliary data and applies corrections in the spatial domain for each interferogram, leveraging the 2D imaging capability of the MIMO radar. The proposed method was validated using simulated synthetic aperture radar (SAR) datasets of bridge under controlled conditions, demonstrating significant enhancement in displacement signatures and enabling the detection of both deflection and modal vibrations with high precision. Field validation experiments were also conducted using an oscillating MIMO radar to observe a simply supported girder bridge. The results showed that the system could detect sub-millimeter deflection signals induced by vehicle live loads—much smaller than platform oscillations—with the minimum observed deflection amplitude of -152.7 μm.