The conventional Kalman filter(CKF)is widely used in tightly-coupled INS/GPS integrated navigation systems.The linearization accuracy of the CKF observation model is one of the decisive factors of the estimation accuracy and therefore navigation accuracy.Additionally,the conventional observation model(COM)used by the filter may be divergent,which would result into some terrible accuracies of INS/GPS integration navigation in some cases.To improve the navigation accuracy,the linearization accuracy of the COM still needs further improvement.To deal with this issue,the observation model is modified with the linearization of the range and range rate equations in this paper.Compared with COM,the modified observation model(MOM)further considers the difference between the real user position and the position calculated by SINS.To verify the advantages of this model,INS/GPS integrated navigation simulation experiments are conducted with the usage of COM and MOM respectively.According to the simulation results,the positions(velocities)calculated using COM are divergent over time while the others using MOM are convergent,which demonstrates the higher linearization accuracy of MOM.
针对截断伪随机扩频序列相关特性不能由数学解析表达式给出的问题,采用计算截断伪随机序列相关最大旁瓣值的方法,确定了北斗与GPS操作者间频率协调的伪随机扩频码码簇,给出了截断非整周期伪随机扩频序列的相关特性与整周期序列的相关特性具有可比拟性的结论;基于双方所确定的伪随机扩频序列,分析了不同伪随机码码簇间的多址干扰,给出了不同系统伪随机码码簇间的多址干扰可使导航接收机的捕获相关损耗达到1~2 d B的结果。
