基于北向陀螺零偏自观测的捷联惯性导航系统双位置初始对准方法

Two-position alignment for SINS based on north gyroscope bias self-observations

传统捷联惯性导航系统单位置初始对准系统不完全可观测,不可观测的东向陀螺零偏造成航向估计的主要误差。双位置初始对准可以改善系统的可观测性,但一般需要精确的转位机构,不便于工程应用。该文提出一种基于北向陀螺零偏自观测的双位置初始对准方法,只需陀螺载体在近似水平的任意两个位置停留片刻,从第1位置提取北向陀螺零偏信息传递给第2位置作为观测量,即可提高东向陀螺零偏的可观测度并提高航向对准精度。为了寻找最优转角,提出一种全面可观测度分析方法,将可观测度细分为表征不同条件下同一状态可观测程度的相对可观测度和表征状态收敛速度的可观测阶两部分,利用相对可观测度分析得出最佳转角为±90°,并进行了仿真实验验证。实测实验结果表明:相比于单位置对准,双位置对准将航向误差由0.268°降低到0.041°,并可估计出水平陀螺零偏。

The traditional one-position initial alignment system for the strap-down inertial navigation system （SINS） is not completely observable because the unobservable east gyroscope bias creates a large heading error. The two-position method can improve the observability but always needs an additional precise rotator which is impractical. This paper describes a two-position method based on a north gyroscope bias self-observation, which only needs two arbitrary approximate horizontal positions. The north gyroscope bias is extracted from one position and transmitted to the other position as an observation to make the east gyroscope bias observable and reduce the heading error. The rotation angle is optimized using a comprehensive degree of observability which includes a relative degree of observability and an order of observability. The relative degree of observability indicates the observability of the same state for different conditions while the order of observability indicates the convergence rate. The relative degree of observability shows that the optimal rotation angle is ± 90°, which is verified by numerical simulations. Tests show that this two-position method reduces the heading error from 0. 268° to 0. 041° and estimates the horizontal gyroscope bias.