Automatic guidance of underground mining vehicles using laser sensors

Autonomous guided vehicles are becoming extremely important in the mining industry. The underground environment is unique and complex in that the lighting conditions are poor, the roads are difficult to traverse, and no GPS can accurately receive signals in these areas. This paper analyzes the characteristics of commonly used positioning methods given that ordinary positioning and navigation methods do not work effectively underground. We outline the composition and principles in underground guidance of autonomous vehicles using the laser-based positioning system. This system is unique in that it draws on the premise of barcode theory, which allows for a feasible relative navigation system even without a GPS. Algorithms were developed to provide real-time control for an autonomous guided scraper. In the vehicle experiment, the scraper was able to autonomously move along the simulated laneway, and the trial average range longitudinal error was only 15 cm in a 40-m distance. Hence, this new type of positioning and navigation system can accurately and reliably guide vehicles.     

Evaluating the limitations of and alternatives in beaconing

In position-based routing protocols, each node periodically transmits a short hello message (called beacon) to announce its presence and position. Receiving nodes list all known neighbor nodes with their position in the neighbor table and remove entries after they have failed to receive a beacon for a certain time from the corresponding node. In highly dynamic networks, the information stored in the neighbor table is often outdated and does no longer reflect the actual topology of the network causing retransmissions and rerouting that consume bandwidth and increase latency. An analysis on the possible impact of beacons due outdated and inaccurate neighbor tables is needed. We quantify by analytical and simulation means the possible performance loss and explore the limitations of position-based routing protocols which use beaconing. In highly mobile ad-hoc networks, the delay can increase by a factor of 20. The neighbor table inaccuracy is the main source of packet loss in uncongested networks. We propose and evaluate several concrete mechanisms to improve the accuracy of neighborhood information, e.g., by dynamic adaptation of the timer values when beacons are broadcasted, and show their effectiveness by extensive simulation.     

星载自适应光学系统信标技术与理论

由于重力场、温度场、光学器件等产生波前误差,造成航空详查相机的分辨力和测量精度降低,用自适应光学钠导星信标系统对这种波前误差进行校正是一种理想的方法。通过对钠导星信标产生原理进行分析,提出了钠导星信标理论模型,并且在该模型的基础上进行了仿真实验,在实验中得到相机高度在250-400km高空时激光器最佳脉冲能量值在597-1530mJ之间,激光脉宽则在5.4-7.1ns之间,这些实验数据对实际应用有一定的参考价值。     

GPS信标机系统的设计与实现

介绍一种利用GPS定位,实现对目标无线定位任务的GPS信标机系统。采用在待测目标上放置信号发送装置,在地面或者其他位置放置信号接收装置,接收装置接收发送装置发送的定位信息,实现定位的目的。经实验得出,信号发送装置的定位信息:经度111°44.72018',纬度39°04.18254',海拔高度1 412 m;信号接收装置的定位信息:经度111°44.73089',纬度39°04.16502',海拔高度1 333 m。结果表明,能准确定位待测目标和接收装置的定位信息(包括时间、经度、纬度和海拔高度等),是一种很好的无线定位信标机系统。