Suppression of the G-sensitive drift of laser gyro in dual-axis rotational inertial navigation system

The dual-axis rotational inertial navigation system(INS)with dithered ring laser gyro(DRLG)is widely used in high precision navigation.The major inertial sensor errors such as drift errors of gyro and accelerometer can be averaged out,but the G-sensitive drifts of laser gyro cannot be averaged out by indexing.A 16-position rotational simulation experiment proves the G-sensitive drift will affect the long-term navigation error for the rotational INS quantitatively.The vibration coupling and asymmetric structure of the DRLG are the main errors.A new dithered mechanism and optimized DRLG is designed.The validity and efficiency of the optimized design are conformed by 1 g sinusoidal vibration experiments.An optimized inertial measurement unit(IMU)is formulated and measured experimentally.Laboratory and vehicle experimental results show that the divergence speed of longitude errors can be effectively slowed down in the optimized IMU.In long term independent navigation,the position accuracy of dual-axis rotational INS is improved close to 50%,and the G-sensitive drifts of laser gyro in the optimized IMU are less than 0.0002°/h.These results have important theoretical significance and practical value for improving the structural dynamic characteristics of DRLG INS,especially the highprecision inertial system.

An improved computation scheme of strapdown inertial navigation system using rotation technique

To improve the accuracy of strapdown inertial navigation system(SINS) for long term applications,the rotation technique is employed to modulate the errors of the inertial sensors into periodically varied signals,and,as a result,to suppress the divergence of SINS errors.However,the errors of rotation platform will be introduced into SINS and might affect the final navigation accuracy.Considering the disadvantages of the conventional navigation computation scheme,an improved computation scheme of the SINS using rotation technique is proposed which can reduce the effects of the rotation platform errors.And,the error characteristics of the SINS with this navigation computation scheme are analyzed.Theoretical analysis,simulations and real test results show that the proposed navigation computation scheme outperforms the conventional navigation computation scheme,meanwhile reduces the requirement to the measurement accuracy of rotation angles.

ROTATING FIBER OPTIC GYRO STRAP-DOWN INERTIAL NAVIGATION SYSTEM WITH THREE ROTATING AXES

The principle of the inertial navigation system（INS） with rotating inertial measurement unit （IMU） is analyzed. A new IMU is established to rotate round each axis in three directions. Then, the related error models for the designed system during rotating are deduced and the improved system is built. Finally, the performance simulation of the proposed system is provided. The simulation result indicates that the designed system can improve the accuracy of the roll and the pitch as well as heading by rotating three axes, thus guaranting the heading accuracy. Moreover, based on the principle of rotation at six different positions, such structure can carry out real-time calibration, and improve the system performance.

Analysis of Error for a Rotating Strap-down Inertial Navigation System with Fibro Gyro

The error equation of a rotating inertial navigation system was introduced. The effect of the system's main error source (constant drift of gyro and zero bias of accelerometer) under rotating conditions for the system was analyzed. Validity of theoretical analysis was shown via simulation, and that provides a theoretical foundation for a rotating strap-down inertial navigation system during actual experimentation and application.

Method of Improving the Navigation Accuracy of SINS by Continuous Rotation

A method of improving the navigation accuracy of strapdown inertial navigation system (SINS) is studied. The particular technique discussed involves the continuous rotation of gyros and accelerometers cluster about the vertical axis of the vehicle. Then the errors of these sensors will have periodic variation corresponding to components along the body frame. Under this condition, the modulated sensor errors produce reduced system errors. Theoretical analysis based on a new coordinate system defined as sensing frame and test results are presented, and they indicate the method attenuates the navigation errors brought by the gyros' random constant drift and the accelerometer's bias and their white noise compared to the conventional method.

A tightly coupled rotational SINS/CNS integrated navigation method for aircraft

Strapdown inertial navigation system(SINS)/celestial navigation system(CNS)integrated navigation is widely used to achieve long-time and high-precision autonomous navigation for aircraft.In general,SINS/CNS integrated navigation can be divided into two integrated modes:loosely coupled integrated navigation and tightly coupled integrated navigation.Because the loosely coupled SINS/CNS integrated system is only available in the condition of at least three stars,the latter one is becoming a research hotspot.One major challenge of SINS/CNS integrated navigation is obtaining a high-precision horizon reference.To solve this problem,an innovative tightly coupled rotational SINS/CNS integrated navigation method is proposed.In this method,the rotational SINS error equation in the navigation frame is used as the state model,and the starlight vector and star altitude are used as measurements.Semi-physical simulations are conducted to test the performance of this integrated method.Results show that this tightly coupled rotational SINS/CNS method has the best navigation accuracy compared with SINS,rotational SINS,and traditional tightly coupled SINS/CNS integrated navigation method.

A Quaternion Scaled Unscented Kalman Estimator for Inertial Navigation States Determination Using INS/GPS/Magnetometer Fusion

This Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer technologies have been widely used in a variety of positioning and navigation applications. In this paper, a low cost solid state INS/GPS/Magnetometer integrated navigation system has been developed that incorporates measurements from an Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer (Mag.) to provide a reliable complete navigation solution at a high output rate. The body attitude estimates, especially the heading angle, are fundamental challenges in a navigation system. Therefore targeting accurate attitude estimation is considered a significant contribution to the overall navigation error. A better estimation of the body attitude estimates leads to more accurate position and velocity estimation. For that end, the aim of this research is to exploit the magnetometer and accelerometer data in the attitude estimation technique. In this paper, a Scaled Unscented Kalman Filter (SUKF) based on the quaternion concept is designed for the INS/GPS/Mag integrated navigation system under large attitude error conditions. Simulation and experimental results indicate a satisfactory performance of the newly developed model.

Error Model of Rotary Ring Laser Gyro Inertial Navigation System

To improve the precision of inertial navigation system（INS） during long time operation,the rotation modulated technique（RMT） was employed to modulate the errorr of the inertial sensors into periodically varied signals,and,as a result,to suppress the divergence of INS errors.The principle of the RMT was introduced and the error propagating functions were derived from the rotary navigation equation.Effects of the measurement error for the rotation angle of the platform on the system precision were analyzed.The simulation and experimental results show that the precision of INS was ① dramatically improved with the use of the RMT,and ② hardly reduced when the measurement error for the rotation angle was in arc-second level.The study results offer a theoretical basis for engineering design of rotary INS.

Comparison of strapdown inertial navigation algorithm based on rotation vector and dual quaternion

For the navigation algorithm of the strapdown inertial navigation system, by comparing to the equations of the dual quaternion and quaternion, the superiority of the attitude algorithm based on dual quaternion over the ones based on rotation vector in accuracy is analyzed in the case of the rotation of navigation frame. By comparing the update algorithm of the gravitational velocity in dual quaternion solution with the compensation algorithm of the harmful acceleration in traditional velocity solution, the accuracy advantage of the gravitational velocity based on dual quaternion is addressed. In view of the idea of the attitude and velocity algorithm based on dual quaternion, an improved navigation algorithm is proposed, which is as much as the rotation vector algorithm in computational complexity. According to this method, the attitude quaternion does not require compensating as the navigation frame rotates. In order to verify the correctness of the theoretical analysis, simulations are carried out utilizing the software, and the simulation results show that the accuracy of the improved algorithm is approximately equal to the dual quaternion algorithm.

Research of Strapdown Integrated Navigation System Based on Rota­tion Control Technology

To realize high-precision Single-axial Rotating FOG-SINS,a low-power,low-cost,middle-precision rotating control mechanism design for single-axial rotating navigation system is put forward.Through theory analysis,design and experimental verification,the rotating control mechanism has good control precision and high reliability,which meets the demands for developing middle&high-precision FOG-SINS.

基于器件信息融合的双旋转惯导系统误差调制策略

目前,大型水面和水下载体一般安装两套旋转惯导系统(RINS),两套系统按相同的旋转调制策略独立运行,系统信息仅互为备份,缺乏有效融合。针对两台旋转惯导系统配置,开展基于器件信息深度融合的联合旋转调制策略研究,进一步提高系统精度。不改变单套系统结构和编排的前提下,优化经典的单轴4位置旋转方案,联合设计两套系统惯性测量单元(IMU)的旋转策略和转停时序,确保任一时刻有一台惯导处于转停状态,在时序上对转停状态下的惯性测量单元输出(陀螺仪和加速度计)信息进行融合,减小因惯性测量单元转动与刻度系数误差和安装误差的耦合效应。误差特性的理论分析验证了联合调制策略的优势。仿真结果表明:在典型误差作用下,采用联合旋转调制策略的系统定位误差,由单套旋转惯导系统精度的2.3 n mile/72 h提高到0.7 n mile/72 h。

旋转惯导姿态误差补偿方法分析

旋转惯导能够实现误差自补偿,从而提高系统导航精度。但旋转惯导中的旋转结构较为复杂,存在轴系的非正交误差、测角误差等,导致姿态输出随着旋转而发生波动,影响着惯导姿态解调输出的精度。针对惯导姿态误差补偿方法,选取4种常用的拟合补偿方法进行讨论,并结合实际采集数据,进行试验比对与分析,为后续工程应用提供参考。

光学陀螺旋转调制惯导系统及关键技术发展

面向长航时、高精度的自主导航技术需求,系统梳理光学陀螺旋转调制惯导系统的发展历程及关键技术现状具有重要的现实意义。首先,基于惯导系统误差特性,阐述了旋转调制技术的基本原理。其次,系统回顾和梳理欧美等西方国家旋转惯导系统发展历程,分析了系统发展演变后的技术逻辑,总结了我国旋转惯导系统的研制现状。最后,立足于提高系统自主导航精度,从旋转策略优化、误差标校、初始对准3个方面分析了旋转惯导系统需解决的关键技术及研究现状。在总结光学陀螺旋转调制惯导系统及关键技术发展基础上,针对后续旋转惯导系统研究提出了几点思考,为高精度自主导航技术研究提供参考。

基于双惯导协同的误差参数估计与融合算法

针对无外界参考信息的双惯导系统长期使用后系统参数发生变化导致导航精度降低,且系统间缺少信息融合的问题,提出了一种同等精度双惯导协同误差估计与信息融合算法。首先以两套旋转式惯导间相对速度误差与位置误差作为观测量,建立包含陀螺和加速度计零偏的导航误差模型。然后分析了不同转序下各状态量的可观测性,采用Kalman滤波对各参数进行有效估计,估计完成后对双惯导系统进行误差补偿及信息融合。仿真结果表明,所提算法对陀螺零偏估计精度优于0.002(°)/h,加速度计零偏估计精度优于4μg,在抑制误差发散的同时,提高了旋转式惯导导航精度。

双轴冗余旋转惯导系统精对准方法

冗余旋转惯导系统(RRINS)相比捷联惯导系统可在提高可靠性的同时通过旋转调制技术减小惯性器件常值误差对导航性能的影响。针对该类系统高精度初始对准需求,以正四面体RRINS为例,对其精对准进行研究。建立每3个陀螺仪和3个加速度计组合方式下系统精对准误差模型;设计卡尔曼滤波器及双轴转位方案;将每种组合方式下的精对准结果及陀螺仪和加速度计零偏的均值作为最终估计结果。仿真结果表明,加速度计零偏估计相对误差在0.2%以内,陀螺仪零偏估计相对误差在0.1%以内。精对准实验结果表明,同等时间内,所提方法的精对准误差相比静基座减小75%以上,将实验中估计出的零偏补偿惯性器件测量信息后,导航解算姿态误差减小65%以上,导航性能得到有效提高。仿真和实验结果表明,所提方法可有效提高精对准精度,并可准确估计惯性器件的零偏。

捷联惯性导航系统误差模型综述

不同的捷联惯性导航系统误差模型主要由误差的数学定义形式及误差的参考坐标系决定。在详细讨论了捷联惯性导航系统的误差模型在相同的参考坐标系下不同的数学形式时的误差方程,以及相同的数学形式下不同参考坐标系时误差模型间数学关系的基础上,推导了乘性四元数误差之间和旋转矢量误差之间的关系,并给出了在应用不同误差模型时的注意事项。

激光陀螺单轴旋转惯性导航系统

高精度的惯性导航系统是提高舰船综合作战性能的基础。为了提高惯性导航系统的精度,采用单轴旋转惯性测量组件的方法,研制了激光陀螺单轴旋转惯性导航系统。介绍了系统的硬件组成,主要包括系统基本结构,惯性器件的主要技术参数和导航计算机的组成。描述了系统的多位置初始对准方式和温度补偿方案。对该系统进行了长时间静态导航实验和跑车实验,实验结果表明:四次长时间静态导航实验峰值定位误差5d优于1nm,10d优于2nm;两次跑车实验峰值定位误差77h优于1.4nm、15d优于2.5nm。

半球谐振陀螺旋转惯导系统误差抑制机理研究

为了优化半球谐振陀螺旋转惯导系统设计、合理分配系统误差,本文分别从局部和全局角度出发,系统分析了旋转惯导系统在静基座条件下的误差传播规律。利用局部分析法讨论了旋转对惯性器件常值误差、标度因数误差以及安装误差的抑制情况,讨论了调制速度与陀螺仪标度因数误差、安装误差耦合所产生误差的特点,给出了组建旋转惯导系统时惯性元件的选择准则;利用全局分析法推导了多误差源同时激励下旋转惯导系统的误差传播模型,得到了导航误差的时域解析表达式。最后通过仿真验证了理论分析的正确性。研究结果为半球谐振陀螺旋转惯导系统的工程设计、改进提供一定的理论支持。

捷联惯性导航系统姿态算法研究

用四元数和旋转矢量在捷联惯导系统中表示姿态矩阵,在圆锥运动的条件下,对旋转矢量算法进行了优化。对四元数、旋转矢量优化算法进行了仿真比较。仿真结果表明:等效旋转矢量算法明显优于四元数算法。

激光陀螺单轴旋转惯导系统多位置对准技术研究

激光陀螺单轴旋转惯导系统初始对准精度受陀螺漂移和加速度计零位的限制,为了减少对准误差,对多位置对准技术进行了研究。给出了单轴旋转惯导系统误差方程,利用奇异值分解的方法,对多位置对准时的系统各状态变量的可观测性进行分析,利用卡尔曼滤波仿真研究了多位置对准过程中方位失准角估计误差收敛情况,系统地分析了卡尔曼滤波器参数P0、Q、R的选取对陀螺漂移的估计精度和收敛速度的影响规律。对单轴旋转惯导系统进行了动基座对准的跑车实验,实验结果表明:多位置对准可以提高陀螺漂移和加速度计零位的估计精度,提高系统对准精度,系统跑车定位误差优于1 nautical mile/72 h(1 853.2 m/72 h)。