Paired structured light configuration for structural health monitoring

The displacement measurement in structural health monitoring (SHM) was not popular due to inaccessibility and the huge size of the civil infrastructures. The frequently employed approaches such as accelerometer, strain gauge, PZT, GPS, LVDT(Linear Variable Differential Transformer) require high cost and are difficult to install and maintain. To develop an SHM system that directly measures the displacement of the structure using lowcost sensor, we proposed a multiple paired structured light (SL) system. The proposed paired SL module which uses two lasers and a camera in pair is inexpensive to implement and can directly measure the accurate relative displacement between any two locations on the structure. The steepest descent and extended Kalman filter-based displacement estimation methods was proposed by deriving a kinematic equation and its constraints. In this paper, we theoretically justify the minimal configuration of the proposed paired structured light system. To do so, another configurations are further investigated. The calibration method was proposed for this specific configuration. After building a prototype of the paired SL module, some real experiments are performed to test the feasibility of the system for a structural displacement monitoring.