Measurement of Structural Displacement Using Visually Servoded Paired Structured Light System

Abstract

Over the past several decades, there has been rapid growth in research on the displacement measurement system for large structures. However, widely used sensors such as accelerometers, strain gauges, PZT, and GPS have disadvantages that they indirectly measure the displacement, are difficult to install, or costly to maintain. To solve the aforementioned problem, a paired structured light (SL) system was introduced in the previous study. Each module is composed of two screens facing with each other each with one or two lasers and a camera. Though the system can successfully estimate 6-DOF displacement, the measurable displacement range is limited due to the limited screen size. In this paper, therefore, a visually servoed paired SL system is proposed. The newly proposed system uses a visually servoed 2-DOF manipulator in order to make the projected laser beams are always on the screen. In other words, the laser pointer is controlled by a manipulator before it gets off. Various experiments were performed to validate the proposed system. The results show that the proposed system estimates 6-DOF displacement with high accuracy and with largely expanded measurement range. By cascading multiple modules, the proposed system can be applied to the massive structures such as long-span bridges or high-rise buildings.

The Multi-Parameter Wireless Sensing System (MPwise): Its Description and Application to Earthquake Risk Mitigation

“…Displacement measurements of high-rise buildings based on conventional imaging have been proposed by [ 32 , 33 ], the latter using high-speed linear cameras, while [ 34 , 35 ] proposed the dynamic monitoring of slender structures using various computer-vision techniques. Most of these approaches involve 1-D or 2-D measurements, but with more complex arrangements, 3-D structural monitoring is also possible, as showed by [ 36 , 37 , 38 ]. The mentioned techniques and approaches can be used to integrate the pre-event assessment of fragility for residential structures, and to collect in real-time information about the health state of the structure during and after an earthquake (see also [ 32 ] for a specific application to damage detection).…”