Development Of All Source Navigation And Positioning Hardware Platform

In this thesis,a smart interface based on a high-performance ARM core board with a Linux operating system is designed.As a subsystem of all-source navigation,the smart interface can fulfil the parallel data acquisition,data processing and real-time transmission of navigation data collection tasks.The smart interface is designed and implemented from hardware,kernel state software and user state software three aspects to meet the requirements of unified interface,plug and play,flexible congifuration,real-time acquisition,parallel processing and transmission on all-source navigation hardware.Aiming at the needs of plug-and-play and multi-channel data parallel acquisition for various sensors in the all-source navigation system,based on high-performance development board,equipped with FPGA interface expansion board,this thesis implements interface redundancy and parallel data acquisition from the hardware.The operating mechanism of the driver plug-and-play and daemon processes in the Linux operating system is studied,based on the hot plug event mechanism and the daemon process in the Linux kernel,the real-time monitoring and reporting of the sensor status is realized.In the process of data processing,the LOF outlier detection algorithm is applied to the detection and elimination of outliers of navigation sensors for the noise and outliers of sensor data.This paper studies the advantages and disadvantages of LOF algorithm and the update mechanism of incremental ELOF algorithm,and proposes a mechanism that can dynamically update the neighborhood K value,so that the improved ELOF algorithm can dynamically update the value of local outliers in real time according to the motion characteristics of the navigation carrier,and improves the detection and recognition rate of outliers.Aiming at the non-uniformity of the time reference of navigation information in various sensors,the least square method was used for data curve fitting according to the navigation data time stamp,and the time reference of each sensor data was unified based on the fitting curve.Aiming at the requirements of real-time interaction between smart interface and navigation computer,this thesis studies and uses the UDP transport layer protocol,in order to ensure the stability of the UDP transport layer protocol,serial number,acknowledgment response,error retransmission,data frame disorder reordering and other stability mechanisms are implemented in the UDP protocol data frame based on the custom data frame,which improve transmission stability on the basis of ensuring real-time transmission.Aiming at the stability,real-time,concurrency and modularization requirements of the all source navigation software system,the thesis studies the principle of Linux process and thread,and designs the multi-thread and multi-process software framework based on the core processor of multi-core and multi-thread.Each sensor corresponds to a process,modularly designing task execution programs,and each process uses multi-thread to implement related functions,making full use of hardware resources,so that the system can process data acquisition and processing tasks of multiple sensors in parallel.Finally,the design and implementation of the all-source navigation smart interface subsystem test platform,testing the smart interface sensor identification,system stability,transmission real-time performance and other aspects of performance.The test results show that the performance of all aspects of the system can meet the requirements of all-source navigation.The hardware concept of the smart interface can effectively reduce the software and hardware pressure of the navigation computer.