Research On Embedded Ponsitioning Synchronous System Of Mobile Laser Scanning Platform On Subway

Three-dimensional(3D) laser scanning technology has the characteristics of high resolution and high accuracy on the space object detection, and it has been widely applied in the tunnel spatial structure detecting field. There are two methods to scan the tunnel: fixed scanning in sub-station and mobile scanning on subway. Comparing with the traditional fixed scaning method, adopting mobile scanning method leads to the higher operation efficiency, the lower labour use, the stabler data quality, and the smaller amount of the data processing. However, the mobile laser scanning system should ensure mobile locations are strictly synchronized to the scanning data and accurate set of scanning spatial coordinate system in the process of scanning.Based on the previously developed mobile laser scanning prototype system, this paper researches and designs a mobile laser scanning system on subway based on ARM embedded positioning and synchronizing technology with light weight, small volume, low power consumption and can be driven by a motor. This new system has the advantages of high reliability of positioning and synchronizing, and complete mobile platform attitude data provided. Meanwhile, it can be also driven by a motor and has the characteristics of light weight, small volume, and low power consumption. The paper firstly researches the overall structure framework of the system, demonstrates the feasibility of synchronous data processing flow and method, and puts forward the method of the modular approach to design the system. The system uses STM32 microprocessor as the core of the data processing unit to real time detect the dynamic position and horizontal posture of the platform by means of the photoelectric encoders combined with the two-dimension sensed inclinometer, thus effectively provides the three-dimensional coordinate information of spatial data. Bi-directional preservational mechanism is adopted in the system design that the synchronous data are saved to the SD card and real time uploaded to the host computer, effectively guarentees the reliability of data storage. Related research work is also extended to the actual engineering application. With the host computer as a part of the mobile laser scanning platform for the system working status display, data storage and operation management, a specialized communication protocol is developed between its Lab View interface and the embedded system.The new mobile system addressed in this paper is based on the embedded positioning and synchronizing system as the research focus, this paper respectively researches on positioning and synchronizing method, function realization, spatial coordinate detetion and platform driven method and some other aspects. The functional verification and the whole tests of the system designed are carried on in the research work, and the results show that the system has basically achieved the research goal as planned. Finally some analysis of system data error sources and potential ways and methods for reducing the error are given in this paper.