硬件可实现的GNSS/INS矢量深组合跟踪环路(英文)

Hardware-implementable vector tracking loop for GNSS/INS deep integration

GNSS矢量跟踪环路(VTL)跟踪灵敏度和定位精度优于标量跟踪环路(STL),但实现复杂度高,三个主要难点是:多通道联合跟踪要求各通道同时获取观测量并在同一时刻更新环路参数;高频率计算卫星位置加重处理器运算负担;无法跟踪载波相位导致无法解调导航电文。以上三个难点阻碍VTL在硬件平台上实现,因此商业接收机通常使用容易硬件实现的STL,但性能次优。为了在嵌入式硬件平台上实现VTL,引入三种方法:异步观测量线性插值、卫星位置计算算法优化、特殊的导航电文解调方法,之后通过仿真验证优化算法的功能及性能。使用航迹发生器生成飞机协调转弯航迹,再使用GNSS卫星信号模拟器产生中频采样信号,基于Matlab平台处理数据并进行了对比分析。仿真结果表明该VTL计算卫星位置效率提升55倍,成功解调导航电文,VTL位置精度优于3 m,速度精度优于0.3 m/s,基于该VTL的矢量深组合(VDI)算法位置精度优于2 m,速度精度优于0.1 m/s。

Tracking sensitivity and positioning accuracy of GNSS vector tracking loop （VTL） are superior to that of scalar tracking loop （STL）, but VTL is difficult to implement on hardware because of three obstacles： 1） all tracking channels＇ measurements and parameters must be processed at the same time for multi-channel joint tracking; 2） the processor has high computational burden due to too frequent satellite position calculation; 3） it is unable to demodulate navigation message due to non-PLL tracking mode. Thus commercial receiver usually use such STL as its hardware is easy to access and its performance is sub-optimal. To apply the VTL on an embedded hardware platform in real-time mode, three methods are introduced： l） linear interpolation for synchronizing asynchronous-observables; 2） algorithm optimization for calculating satellite position; 3） a novel method for demodulating navigation date bits from vector frequency lock loop. Simulations of the VTL and VDI are carried out using a normal aircraft trajectory, in which data samples are generated by trajectory generator and GNSS signal simulator, and then processed and compared on Matlab platform. The results show that the calculation efficiency of satellite position has improved 55 times, and the navigation message is successfully demodulated, and the VTL＇s position and velocity accuracies are better than 3 m and 0.3 m/s, respectively, while the VDI＇s position and velocity accuracies are better than 2 m and 0.1 m/s, respectively.