The Research On Structural Displacement Monitoring Method Based On Laser Projection-Sensing Technology And Smartphone

For civil engineering structures, the changes of live load, fatigue effect of structure itself, material aging, environmental corrosion effects and human’s behavior, all of these factors are likely to bring a devastating disaster to structures. In the worldwide, every year the casualties and property loss caused by the destruction of civil engineering structures are numerous. Therefore, ensure the safety of civil engineering structures not only is an important guarantee of safety of people life, but also can reduce the economic losses. During last decade, Structural Health Monitoring (SHM) Systems have been widely developed and utilized for various kinds of structures around the world. Integrated with kinds of nondestructive sensing technique, SHM system not only can be used to assess the safety and serviceability of structures, to detect structural damage in time, to forecast the possible disasters and timely giving guidance to people to stay away from the potential disaster, but also can provide evidence and guidance for the repair, maintenance and management decision-making of the structures. In this way, the service life of the structures can be improved and it will largely reduce property loss and casualties.Among the many monitoring projects, structural displacement is the hotspot in SHM. The displacement data is not only the extremely valuable raw data of the analysis of structural state. but also is an important monitoring parameter to ensure the safety of structural during construction and operational. So this article puts forward several structural displacement monitoring method based on laser projection-Sensing technology and smartphone, and a series of exploration research was conducted. The main contents are as follows:1. First, the laser spot recognition method was studied, and the detailed introduction of recognition principle and steps are made. Next, the software for the displacement monitoring system was developed. Cooperated with industrial camera, the software can realize the displacement monitoring of laser spot. A detailed introduction of the software is made and a series of static and dynamic experiments were conducted. The results show that such a system has high measurement accuracy and speed. Finally, a mid-span displacement monitoring experiment of truss bridge model were conducted, the experiment verify the applicability in practical project of the proposed method.2. Put forward the idea of using smartphone for structural displacement monitoring, and then, the displacement monitoring method based on laser projection-Sensing technology was transplanted onto the smartphone. After the calibration method was optimized, a laser spot displacement monitoring APP based on android platform called D-Viewer was developed. It can monitor the laser spot by calling the smartphone’s camera. We also performed a lot of static and dynamic displacement monitoring experiments using smartphones to verify the accuracy of D-Viewer. In addition, mid span displacement of one suspension bridge model was tested using D-Viewer. Results show that D-Viewer can be used as a convenient, fast, low-cost structural displacement monitoring method with reasonable precision.3. Further simplify the method of using smartphones for displacement monitoring. Directly paste the black round (printed on white paper) on the monitored object, through monitor the displacement of black round to achieve the purpose of monitoring the displacement of monitored object. What’s more, a new function of monitor the change of two black rounds’ centroid coordinate difference value is added. It can be used to monitor the crack width of structures, and its accuracy is verified by simulation experiment.