Navigation Computation in Terrestrial Strapdown Inertial Navigation Systems

The problem of computing the translational velocity and position relative to earth, which has to be solved by the processor of a strapdown inertial navigation system is discussed. Several approaches are briefly examined with consideration given to the form in which the sensor data are generated and to the computational burden involved in each approach. A computational scheme is finally selected in which the computation is divided into three rate levels. The differential equations of this scheme are developed and the assumptions on which the development is founded are stated. Three variants of the basic scheme are presented, each based on a different level of simplifying assumptions. The main purpose of this work is to develop the differential equations to be solved at each stage of the computation, rather than the numerical implementation of the solution. This work supplies the theoretical background for some of the numerical methods which are now being used.     

捷联惯导系统圆锥误差分析

捷联惯导系统由于数学平台隔离作用的不完善,当运载体沿机体坐标轴存在同频率的角振动和线振动时,角振动引起的整流效应将在姿态更新计算中产生圆锥误差,角振动和线振动引起的整流效应将在速度计算中产生划桨误差,在位置计算中产生涡卷误差。文中详细分析了圆锥误差产生机理,针对某型飞机装备 SIGMA50 GPS/SINS 组合导航系统对底座安装的精度要求,分析了安装误差、陀螺频带不够宽、姿态更新率过低对姿态精度的影响,并对维护捷联惯导系统提出建议。     

捷联式惯导系统动态误差特性研究

根据载体运动状态下捷联惯性导航系统(SINS)的误差方程时变的特点,推导出捷联惯性导航系统动态误差模型,并对其在几种动态环境下的误差特性进行了仿真研究。     

Error Analysis of Space-Stable Inertial Navigation Systems

The error equations for a space-stable inertial navigation system are derived. This is done by directly perturbing the mechanization equations in the inertial frame and then transforming in open-loop fashion to the local-level frame. A rotating inertial platform and velocity and altitude damping are considered. The relations between errors in space-stable and local-level systems are noted. Numerical results are presented for certain random error sources.     

A New Mathematical Formulation for Strapdown Inertial Navigation

A differential equation is developed for the orientation vector relating the body frame to a chosen reference frame. The time derivative of this vector is the sum of the inertially measurable angular velocity vector and of the inertially nonmeasurable noncommutativity rate vector. It is precisely this noncommutativity rate vector that causes the computational problems when numerically integrating the direction cosine matrix. The orientation vector formulation allows the noncommutativity contribution to be isolated and, therefore, treated separately and advantageously. An orientation vector mechanization is presented for a strap down inertial system. Further, an example is given of the applica tion of this formulation to a typical rigid body rotation problem.     

捷联惯性导航系统高精度动态仿真算法

由于飞行器动态模型航迹生成算法与惯性导航系统算法原理存在差异,无法直接仿真分析惯性传感器不同误差特性对惯性导航系统动态性能的影响.基于飞行器动态模型航迹数据,提出一种捷联惯性导航系统高精度动态仿真实现方法,设计了惯导参数动态计算误差并行补偿方案,实现了对导航系统动态仿真过程中导航参数计算误差的有效分离.在搭建的仿真平台上,有效验证了所提出仿真方法的性能,为实际惯性传感器选型和指标选择提供支撑.     

捷联惯导系统发展及其军事应用

从20世纪80年代开始,以激光陀螺和光纤陀螺为代表的捷联惯导系统逐步进入实用阶段,为高新技术武器装备的革新改造打下了坚实技术基础。本文主要介绍捷联惯导系统的组成、原理、特点、发展趋势及其在航空军事领域中的主要应用。     

Autonomous Upgrading of Inertial Navigation Systems

The performance of substandard inertial platform gyros can be improved through the sampled supervision of their operation by a higher grade gyroscope mounted directly on the platform. The relative drift rates of the susbstandard platform gyros are estimated on a cyclical basis. This paper describes techniques for estimating the drift rates. It deals with the method of applying these estimated values in the form of platform correction signals.     

Doppler Radar Error Equations for Damped Inertial Navigation System Analysis

The use of Doppler radar measurements to provide velocity damping for an aircraft inertial navigation system is considered. Three different Doppler antenna configurations are examined: two-axis stabilized, azimuth stabilized, and data stabilized antennas. A general reference velocity error equation is presented and appropriately evaluated for each of the Doppler configurations. Specific elements of the error equations are examined and physically interpreted for both local-level and space-stable inertial systems. Detailed examination of the interaction of Doppler radar and inertial navigation velocity error mechanisms is provided.     

利用车载试验分离惯导平台误差研究

分析了车载试验时平台的安装方式以及所需要的外测信号等问题,给出了误差模型以及导航误差方程,设计并进行相关软件仿真。结果表明,在现有外测信号精度下,该方法可分离出惯导平台误差中加速度计和陀螺仪的零次项误差系数,对加速度计的一次项误差系数分离效果也较好。     

惯导平台系统连续翻滚试验测试方法研究

首先以X加速度计坐标系为基准建立了平台台体坐标系,推导了基于框架角的姿态方程,即状态方程,并以三个加速度计输出作为观测量建立了观测方程。在此基础上,应用D最优设计方法对平台系统重力场连续翻滚测试进行了优化设计,给出了改进的扩展卡尔曼滤波方程。最后,试验结果验证了该测试方法的有效性。     

Analysis Strapdown Navigation Using Quaternions

A brief review of the theory of strapdown inertial navigation is presented in which the attitude of the sensor box with respect to inertial space is represented by the four-parameter quaternion vector. . A 4X4 matrix R is defined which aids in relating quaternions to direction cosines and facilitates interpretation of the equations for error propagation, which are also derived. In the interpretation, it is shown that the error in the quaternion vector causes aor-(correctable) scale factor error and an equivalent tilt vector error that propagates the same way as the platform tilt vector in a gimbaled system.     

Strapdown Guidance Error Analysis

A crucial part of so-called ?strapdown? techniques for inertial guidance systems is the generation of the matrix of direction cosines relating the body axes to the reference axes. This is generally done by direct integration of a set of differential equations having the body angular velocities as inputs. This paper is devoted to an error analysis of two commonly used integration schemes, namely, direction cosines and quaternions. Scale, skew, and drift errors are defined, and the susceptibility of the integration schemes to these types of error is examined. It is concluded that the quaternion scheme offers an advantage because it intrinsically yields zero skew error. The paper is presented in two parts, for convenience.     

陀螺RRW在惯导系统中的误差传播特性

角速率随机游走是高精度光纤陀螺的一项主要随机误差源,对惯性导航系统的误差有着较大影响。分析了角速率随机游走的统计特性,推导了角速率随机游走引起的惯性导航系统姿态、位置误差的解析表达式,研究了静基座环境下的惯性导航系统在长时间导航环境下的随机误差传播规律,对角速率随机游走作用下的惯性导航系统误差进行了仿真与实验,验证了所推导公式的正确性,对惯性导航系统的设计与误差分析具有一定的参考意义。     

GPS Aided Inertial Navigation

The Global Positioning System is an extremely accurate satellite-based navigation system which, after its completion in 1989, will provide users worldwide, 24 hour. all weather coverage. A joint research project among Boeing, Rockwell-Collins, and Northrop has been completed in which a GPS receiver was integrated with a low-cost strap-down inertial navigation system and a flight computer. A Kalman filter in the latter allows in-fight alignment and calibration of the INS. In addition, feedback from the INS to the GPS receiver improves the system's ability to reacquire satellite signals after outages. The resulting system combines the accuracy of GPS with the jamming immunity and autonomy of inertial navigation. System tests were conducted in which a Boeing owned T-33 jet aircraft was flown through known test pattern to align and calibrate the INS. Earlier tests, including tests against an airborne jammer, were conducted in a modified passenger bus.     

加表量化精度对惯导平台误差系数辨识的影响

通过采用加表的输出以及由离心机半径、角速度、角位置所确定的向心加速度输入作为观测量的辨识方法,结合惯导平台的误差模型,仿真分析了加表量化精度对惯导平台误差系数辨识结果的影响。结果表明,加表量化精度越高,惯导平台误差系数的辨识精度越高。     

From Autopilot to Strapdown: Electrotechnology in Inertial Guidance and Control

Electrotechnology has been a significant factor in the evolution of guidance and control (G & C) over the last half century. Ship stabilizers that used rotating wheels for brute force control were electrically driven. However, the first pilotless aircraft, developed in World War I, was controlled primarily with pneumatic servos. Inertial guidance and electronic control systems surfaced at Peenemunde around World War II. Advances in fire control servos led to development of the floated gyro and ushered in precision inertial navigators. Digital electronics replaced analog designs, so that the level of G & C sophistication increased dramatically. As digital computers became smaller and more powerful their use proliferated. The manned space program in the 60's saw substantial improvements in electronics reliability and performance. The successful first launch of the Space Shuttle, with all its complexity, is a tribute to electronics progress. It is difficult to predict what G & C advances electrotechnology will bring in the next 50 years.     

Optimum Reset of Ship's Inertial Navigation System

Optimum linear filter and control theory is applied to the practical problem of supplementing an inertial navigation system with discrete reference information. The information takes the form of position obtained from Loran C or Decca, for example, and occasional azimuth fixes obtained from star sightings. In particular, optimum use of this information is discussed for the Ship's Inertial Navigation System (SINS) installations intended for missile carrying submarines and warships. A model representative of the SINS dynamics is formulated appropriate for application of optimum filter and control theory. Interpretation of the optimum control dictated in part by the augmented SINS model is discussed. Simulation studies that show the relative transient behavior and the stabilizing effect of the closed-loop filter and control processes are also presented.     

A New Algorithm for Strapped-Down Inertial Navigation

When a whole-number digital computer, rather than an incremental digital computer, is used to solve the strapped-down inertial navigation computational problem, the approximate direct solution of the direction-cosines matrix equation is no longer the optimal algorithm. The Euler parameters are demonstrated to afford improved accuracy and reduced computation time when used in an appropriate algorithm. A new method of classifying the transformation errors is developed and used.