加速度辅助的EKF跟踪环及时间延迟影响分析

Acceleration aided EKF-PLL and analysis of time delay effect

高动态情况下,GNSS/INS紧耦合系统中传统的速度辅助跟踪环路容易失锁,针对该问题提出一种加速度辅助的EKF载波跟踪方法。惯性辅助环路的跟踪性能与惯性信息计算的卫星多普勒误差大小有关,这决定于惯性信息的精度和时间延迟,其中时间延迟主要包括环路预测引入的延迟及辅助信息更新率低于环路更新率引入的延迟。通过分析指出,在时间延迟的影响下,加速度辅助计算的卫星多普勒误差远小于速度辅助。以PLI为衡量指标,仿真试验表明了在高动态且惯性信息存在时间延迟的情况下,传统速度辅助估计的多普勒误差过大,无法辅助环路跟踪。而提出的加速度辅助EKF跟踪环受时间延迟的影响较小,误差小于1g的加速度信息可辅助跟踪存在10g/s视线加加速度的高动态卫星信号。

In view that traditional velocity aided GNSS carrier tracking loop in GNSS/INS tightly coupled system is easy to lose lock under high dynamic situation,an acceleration-aided EKF-PLL carrier tracking method is proposed.The performance of inertial information aided tracking loop is related to the satellite doppler error induced by inertial information,and the satellite doppler error is determined by the accuracy and time delay of aiding inertial information.Besides,the time delay is mainly induced by the prediction loop and the aiding information whose update rate is lower than that of tracking loop.The analysis shows that the doppler error calculated by acceleration aiding is less than the one by velocity aiding.Take the PLI as parameter index,the simulation test shows that,under high dynamic situation and inertial information time delay,the doppler error estimated by traditional velocity aiding is too large to aid the tracking loop,while the error estimated by acceleration aided EKF-PLL is robust to time delay,and the acceleration error less than 1g can be used to aid the track of the high dynamic signal with 10g/s line-of-sight jerk.