RU2539131C1 - Strapdown integrated navigation system of average accuracy for mobile onshore objects - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: invention can be used in small-sized strapdown inertial navigation systems (SINS) integrated both with a satellite navigation system (SNS) and with the odometer system for use in mobile onshore devices of different types. The system comprises a unit of sensing elements (SE), a unit of calculating linear and angular velocities and the geographical coordinates, the unit of generation of signals of damping, the first and second units of quaternion calculations, the unit of calculating the matrix of the directing cosines and angles of the system orientation, the receiver of signals of the satellite navigation system (SNS), the unit of determining the quality of SNS signal, the switch of the vector signals, the first and second adders-subtractors of the vector signals, the unit of correction of course angle, and also the wander of directional (azimuth) gyroscope, the unit of stop-detector, the unit of the odometer system with a plurality of connections of different signals between the units and switching connections in different manoeuvres of the object-carrier of SINS.

EFFECT: improvement in accuracy when using coarse or moderate-accurate sensitive elements of SINS.

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Description

Technical field

The invention relates to the field of strapdown inertial navigation systems (SINS) integrated with both a satellite navigation system (SNA) and an odometric system (OD) for use in various types of mobile ground devices.

State of the art

The use of SINS with “coarse” or medium-precision sensitive elements (CE) is described in a number of US patents of American GNS corporation, for example, in a number of patents on small-sized micromechanical inertial measuring devices (US patents Nos. 6671648, 6522992, 6516283). The focus of these patents is on providing advantages over traditional SE units based on the use of external navigation information sensors (such as GPS).

The main disadvantage of the SINS data is the impossibility of long-term operation in stand-alone mode when the SNA is turned off, which is fundamentally important when setting any type of active jamming (GPS jamming).

In US patent 5375059 (publ. 20.12.1994) (US patent analogues 5390125, 5438517) conceptually describes a complex integrated system for accurately determining the position of the device on or near the Earth in real time, in which in an integrated mode including the SNA, SINS , OD with a combination of their information and its digital processing using Kalman filters.

However, this system is overly complex, containing many additional systems, not so much navigation, as control and execution of the movement of the device in the area, including obstacles. An integrated navigation system is described only at the conceptual and functional levels without the necessary and sufficient details of the interaction of its components.

With mathematical details, a multisensory integrated navigation system using odometer measurements, in particular for matrix and integral mathematical formulas of Kalman filters, is discussed in Paul D. Groves's Principles of GNSS, Inertial and Multisensor Integrated Navigation Systems, Artech House, 2006, P 441-443.

The main limitation of such a system is the fact that for “coarse” and mid-range CEs (drift of gyroscopes of 0.5 ... 2 deg / h) SINS, it will not be able to provide accurate reckoning of coordinates in autonomous mode when the SNA is turned off.

The main objective of the invention is a significant increase in the accuracy of calculating the velocities and coordinates of a ground object in an autonomous mode when using "coarse" or medium-precision CE BINS.

Disclosure of invention

To achieve a technical result, the device of the middle-accuracy strapdown integrated navigation system for a mobile ground object contains:

CE block, consisting of three accelerometers and three angular velocity sensors along three orthogonal axes,

unit for recalculation of accelerations associated with the navigation coordinate system,

block for calculating linear and angular velocities and geographical coordinates,

damping signal generation unit, first and second blocks of quaternion calculations,

a unit for calculating a matrix of guide cosines and orientation angles of the system, a receiver of SNA signals,

unit for determining the signal quality of the SNA,

vector signal switch

first and second adders-subtractors of vector signals,

a block for the correction of the course angle, as well as the drift of the course (azimuthal) gyroscope,

stop detector unit,

odometric system unit.

The set of connections of various signals between the blocks and switching links in different maneuvers of the SINS carrier object can be essentially described as follows.

The outputs of the linear acceleration signals of the accelerometers of the SE block are supplied to the first input of the acceleration conversion unit from the coordinate system connected to the navigation system, and the first output of the conversion unit matrix signals of the direction cosines of the matrix unit of the direction cosines matrix and system orientation angles is connected to the second input of the conversion unit. The outputs of the angular velocities of the speed sensors of the SE block are fed to the first input of the first block of quaternion calculations, the output of which is connected to the first input of the second block of quaternion calculations, the output of which is connected to the input of the block calculation module of the guiding cosines and orientation angles and to the second feedback input of the first block of quaternion calculations .

The output of the acceleration signals from the acceleration conversion unit from the coordinate coordinate system connected to the navigation system is connected to the first input of the linear and angular velocity and geographical coordinates calculation unit.

Three signals are received from the SNA signal receiver, the first of which, according to the SNA, is the linear object velocity vector signal arriving at the positive input of the first adder-subtractor, and the second signal, the SNA communication quality signal, is input to the SNA signal quality determining unit, the output of which is connected to the control input of the switch, and the third signal of the track angle of the object, according to the SNA, is fed to the first input of the course angle correction block, as well as the drift of the directional gyroscope.

In this case, the second input of the indicated correction block is connected with the output of the signal of the heading angle of the system from the block calculation matrix of the guiding cosines and orientation angles, and the third input of this correction block is connected to the output of the stop detector block, the first input of which is connected to the output of the acceleration signal from the acceleration conversion block from the coordinates connected to the navigation system, and at the second input of the stop detector block, angular velocity signals from the SE block are received.

The vector signal of the linear speed of the _VINS system V from the third output of the block for calculating linear and angular velocities and geographical coordinates is fed to the subtraction inputs of the first and second adders-subtracters, the outputs of which are connected to the corresponding inputs of the above switch. At the positive input of the second adder-subtractor, a speed signal is received from the odometric system unit, the input of which is the output signal of the course of the entire system from the calculation unit of the matrix of guiding cosines and orientation angles. The output of the switch is connected to the input of the block for generating damping signals and the second input of the block for calculating linear and angular velocities and geographical coordinates, the third and fourth inputs of which are connected to the corresponding first and second outputs of the block for correcting the course angle, as well as the drift of the directional gyroscope.

The vector signal of the absolute angular velocity of the navigation trihedron from the first output of the block for calculating linear and angular velocities and geographical coordinates is fed to the second input of the second block of quaternion calculations, the third and fourth inputs of which receive the first and second correcting signals of angular velocities, respectively, from the second output (vertical control signal angular velocity) from the block for calculating linear and angular velocities and geographical coordinates and from the output of the block for generating signals firovaniya.

The third and fourth outputs of the block for calculating linear and angular velocities and geographical coordinates are respectively the outputs of the entire system in linear velocity (or its components) and geographical coordinates of the object.

The second, third and fourth outputs of the signals of the orientation angles of the block computing the matrix of guide cosines and orientation angles are the corresponding outputs of the system at the angles of the course, pitch and roll of the object.

To significantly improve the accuracy of calculating the velocities and coordinates of a ground object in the autonomous mode when using “coarse” or medium-precision CE BINS, it is proposed, first of all, to periodically calibrate (compensate) the drift of an azimuthal (directional) gyroscope both using the SNA and in the mode of mobile stops ground object (at the signal of the stop detector). In addition, to smooth the readings of speed and, therefore, to more accurately obtain the coordinates of the object, better, “soft” damping of SINS errors by the readings of the odometric system in the absence of SNA signals is carried out. It is important to note that in the case of a satisfactory SNA signal, the system is always in integrated mode with the SNA, and only if there is a failure of the SNA, the system goes into offline mode of calculation using the signal from the odometric system.

List of drawings

Figure 1 - block diagram of the device of the proposed system.

Figure 2 is a comparison of time graphs of errors in determining the coordinates of the proposed device and the traditional system of the prior art.

The implementation of the invention

In Fig. 1, the system blocks are numbered as follows: 1 — the CE block, consisting of three accelerometers and three angular velocity sensors (DLS) located along three orthogonal axes; 2 - unit for recalculation of accelerations associated with the navigation coordinate system; 3 - block calculating linear and angular velocities and geographical coordinates; 4 - block the formation of damping signals; 5 - the first block of quaternion calculations; 6 - second block of quaternion calculations; 7 - block calculating the matrix of guide cosines and orientation angles; 8 - SNA (receiver of SNA signals); 9 - block determining the signal quality of the SNA; 10 - switch vector signals; 11 - the first adder-subtractor of vector signals; 12 - the second adder-subtractor of vector signals; 13 - block correction of the angle of the course, as well as the drift of the course (azimuthal) gyroscope; 14 - block stop detector; 15 - block odometric system.

The following designations of the device signals are adopted in the diagram:

from block 1: a _b is the vector of signals of apparent accelerations from accelerometers in the coupled system and ω _b is the vector of signals of absolute angular velocity from the TLS in the coupled coordinate system;

from block 2: a _N is the vector of apparent accelerations in the navigation coordinate system;

from block 3: ω _N is the absolute angular velocity vector of the navigation trihedron for controlling the computing platform;

- управляющий (корректирующий) сигнал вертикальной угловой скорости для вычислительной платформы; $${\omega }_{up}^c$$

- control (correcting) signal of vertical angular velocity for a computing platform;

V _ANN is a vector signal of the linear velocity of the object relative to the Earth in projections on the axis of the navigation trihedron (V _N , V _E are the components of the output linear velocity vector V of the object in the north and east directions);

φ, λ - output geographical coordinates of the object: latitude and longitude;

from block 4: ω ^c is the vector of correction (control) signals of the angular velocity of damping of the computing platform;

from block 6: q ₀ , q ₁ , q ₂ , q ₃ - quaternions of rotation from the associated coordinate system to the navigation coordinate system;

- матрица направляющих косинусов между связанной и навигационной системами координат;from block 7: object orientation angles (system output signals): H - course, ϑ - pitch, γ - roll; as well as: $$C_b^N$$

- a matrix of guide cosines between the associated and navigation coordinate systems;

from block 8: V _CHC - vector signal of the linear velocity of the object relative to the Earth, determined by the sensors of the SNA; H (GPS) - the track angle of the object according to the SNA;

from block 15: V _OD - vector signal of the linear velocity of the object, determined by the odometric system (OD) and its sensors;

- выбранная коммутатором из двух разностей разность сигналов линейных скоростей;from vector switch 10: $$\delta \hat{V}$$

- the difference of the linear velocity signals selected by the switch from two differences;

- разность сигналов линейных скоростей по показаниям ИНС и СНС;from the first vector adder-subtractor 11: $$\delta {\hat{V}}_{\mathrm{one}}$$

- the difference of the linear velocity signals according to the ANN and SNA;

- разность сигналов линейных скоростей по показаниям ИНС и одометрической системы;from the second vector adder-subtractor 12: $$\delta {\hat{V}}_2$$

- the difference of the linear velocity signals according to the readings of the ANN and the odometric system;

- оценка ошибки системы по курсу, $$\delta {\hat{\omega }}_{up}^{dr}$$

- оценка ошибки угловой скорости (дрейфа) моделируемого азимутального (курсового) гироскопа.from block 13: $$\delta \hat{H}$$

- assessment of system error at the rate, $$\delta {\hat{\omega }}_{up}^{dr}$$

- estimation of the error of the angular velocity (drift) of the simulated azimuthal (course) gyroscope.

Information and signal exchange between the inputs and outputs of the blocks is carried out along the communication lines shown in the block diagram by solid thin lines. Communication lines are known lines of communication and information exchange, for example, via serial code, parallel code, multiplex, etc. Various digital and analog channels can be used as data transmission channels, for example, information exchange channels made in accordance with GOST 18977 -79 (Airborne equipment complexes. Types of functional connections. Types and levels of electronic signals).

System device

To improve the accuracy and efficiency of the autonomous calculation of speeds and coordinates in the absence of signals from the SNA, the device is assembled, programmed, debugged and works as follows.

между связанной и навигационной системами координат, а также выходные углы ориентации объекта (курс, тангаж, крен). Также элементы (q₀, q₁, q₂, q₃) второго кватерниона используются в первом блоке кватернионных вычислений (блок 5) в качестве корректирующих сигналов обратной связи.Using the values of the signals of angular velocities w _b measured by the TLS of block 1, the elements of the quaternion of the final rotation from the associated coordinate system to the inertial are calculated (block 5), and then from the inertial coordinate system to the navigation (block 6). For the elements (q ₀ , q ₁ , q ₂ , q ₃ ) of the second quaternion of the final rotation (block 6) in block 7, the elements of the matrix of guide cosines are calculated $$C_b^N$$

between the connected and navigation coordinate systems, as well as the output orientation angles of the object (course, pitch, roll). Also, the elements (q ₀ , q ₁ , q ₂ , q ₃ ) of the second quaternion are used in the first block of quaternion calculations (block 5) as correction feedback signals.

осуществляют пересчет ускорений a _b, измеряемых акселерометрами блока 1, из связанной в навигационную систему координат:

.For the next calculation step in block 2, according to the obtained elements of the matrix of guide cosines $$C_b^N$$

recalculate the accelerations a _b measured by the accelerometers of block 1 from the coordinate system connected to the navigation system:

.

Then, in block 3, the linear and angular velocities of the object are calculated in the navigation coordinate system and the geographical coordinates of the object are calculated. The calculated angular velocities, as well as the control signals for the correction of angular velocities, are supplied to the corresponding inputs of the 2nd quaternion block (block 6).

To implement the damping signals of the SINS computing platform in blocks 3 and 4, they use (through the switch 10 vector signals) the difference of linear velocity signals according to the ANN and SNA (adder-subtractor 11 vector signals) or, when the SNA signal cannot be used, the difference of linear velocity signals readings of the ANN and the odometric system (adder-subtractor 12 vector signals). Switching the operation mode of the vector switch 10 is carried out depending on the quality of the received SNA signal, evaluated in block 9 determining the quality of the SNA signal. Block 9 works as follows: the quality of the SNA signal is determined by the value of the DOP (Dilution of Precision, decrease in accuracy) parameter. The value of DOP characterizes the geometry of the positioning of the satellites of the global navigation system relative to the antenna of the SNA receiver. The higher the DOP value, the closer the satellites are to each other and, therefore, the lower the accuracy of the obtained navigation parameters. The optimum value is considered to be a DOP value of less than 6. With a DOP value> 20 or the absence of a SNA signal, SNA information is not used in further calculations. In block 15, the output angle of the system’s course from block 7 is also used to lay out the velocity vector V _OD in the components in the north and east directions using the sine and cosine of the angle of the course.

линейных скоростей (в виде составляющих в северном и восточном направлениях) используют для формирования первых демпфирующих сигналов $$-K\delta \widehat{V_N}$$

, $$-K\delta \widehat{V_E}$$

в блоке 3 (эти сигналы используются в качестве сигналов обратной связи для вычисления сигналов линейных скоростей в блоке 3) и вторых демпфирующих сигналов $$-K^b\delta {\hat{V}}_N$$

, $${\text{K}}^{\text{b}}\text{δ}{\hat{\text{V}}}_{\text{E}}$$

в блоке 4, и все эти демпфирующие сигналы поступают на соответствующие корректирующие входы второго блока кватернионных вычислений 6. Коэффициенты K и K^b - параметры формирования сигналов демпфирования (их примерные размерные величины могут быть: K=1,4 1/с, K^b=0,05 1/метр).Vector Difference Selected by Switch 10 $$\delta \hat{V}$$

linear velocities (in the form of components in the north and east directions) are used to form the first damping signals $$-K\delta \widehat{V_N}$$

, $$-K\delta \widehat{V_E}$$

in block 3 (these signals are used as feedback signals for calculating linear velocity signals in block 3) and second damping signals $$-K^b\delta {\hat{V}}_N$$

, $${\text{K}}^{\text{b}}\text{δ}{\hat{\text{V}}}_{\text{E}}$$

in block 4, and all these damping signals are supplied to the corresponding correcting inputs of the second block of quaternion calculations 6. The coefficients K and K ^b are the parameters for generating damping signals (their approximate dimensional values can be: K = 1.4 1 / s, K ^b = 0.05 1 / meter).

для вычислительной платформы и из блока 4 сигналы демпфирования ω^c вычислительной платформы БИНС по угловой скорости.As a result, the corresponding inputs of the 2nd quaternion block 6 from block 3 go signals: the absolute angular velocity vector ω _{N of the} navigation trihedron for controlling the SINS computing platform, the control (correcting) signal of the vertical angular velocity $${\omega }_{up}^c$$

for the computing platform and from block 4, damping signals ω ^{c of} the SINS computing platform in angular velocity.

In block 13 correction of the angle of the course implemented the following original digital algorithm. Calibration of the heading error (azimuth) by the SNA signal in the proposed device is original in that the system’s indication of the course exit angle (from block 7) follows the SNA’s indication of the directional angle (from block 8) (the SNA determines only the directional angle, and the ANN determines the angle course). At the same time, in block 13, the course output signal is calculated by the discrete formula of the aperiodic link

, $$H_k^{out}=H_k^{\mathrm{AND}N\mathrm{FROM}}+Kn\left(H(GPS)-H_k^{\mathrm{AND}N\mathrm{FROM}}\right)$$

,

Where

H (GPS) is the travel angle calculated by GPS;

H ^ANN - the signal of the course N by ANN from block 7

k is the index of the current time discretization moment;

) K_H=0, так как в этом случае нельзя корректировать ИНС по показаниям СНС). Таким образом, разность показаний системы по курсу и СНС по путевому углу пропускается через указанное апериодическое звено и далее компенсируется в показаниях ИНС посредством определяемого в фильтре Калмана блока 13 сигнала оценки ошибки системы по курсу δH, который поступает в блок 3 для формирования корректирующей составляющей угловой скорости $${\omega }_{up}^c$$

.K _H - gain of a discrete aperiodic link (approximately K _H = 10 ^-3 - in the usual mode, when there is no slippage in turning a wheel or tracks of a land vehicle, but in case of slippage (if the modulus of the rate of change of the course angle

) K _H = 0, since in this case it is impossible to adjust the ANN according to the testimony of the SNA). Thus, the difference in the system readings for the heading and SNA along the track angle is passed through the specified aperiodic link and then compensated for in the ANS readings using the Kalman filter of block 13 of the system error estimation signal at the rate δH, which is sent to block 3 to form the correction component of the angular velocity $${\omega }_{up}^c$$

.

курсового гироскопа с использованием традиционного фильтра Калмана с моделямиIn block 13, the current instantaneous signals for estimating the system error at the rate δH and for estimating the error of the angular velocity (drift) are calculated $$\delta {\hat{\omega }}_{up}^{dr}$$

heading gyro using a traditional Kalman filter with models

- модель системы; $${\dot{\omega }}_{up}^{dr}=\ddot{H}=0$$

- system model;

z = Н ^out - Н ^ANN - measurement model.

оценки ошибки угловой скорости (дрейфа) азимутального (курсового) гироскопа компенсируется в блоке 3 вычисления линейных и угловых скоростей. Компенсация производится простым вычитанием полученной оценки дрейфа из сигнала угловой скорости.At the same time, the stop detector unit 14 is triggered at the object stops with a common signal for the resulting comparison of the scalar module of linear acceleration signals and the angular velocity of the object with its predetermined threshold values. Threshold values do not depend on the type of carrier object, but depend on the type of sensitive elements (low-precision microelectromechanical SEs or fiber-optic sensors) that are part of the system. Thresholds are selected in the following ranges: for acceleration δ <0.01-0.1 m / s ² , for angular velocity δ <0.0001-0.001 deg / s. These thresholds have the physical meaning of restrictions on the SINS correction during the maneuver of the object. After the common signal of the stop detector coming from block 14 to block 13 is triggered, in block 13 the signal of the simulated azimuthal (directional) gyroscope is averaged. This averaging is necessary because the instantaneous value of the drift estimate contains significant high-frequency noise. In order to filter out this noise, you can use any low-pass filter. The signal received from block 13 $$\delta {\hat{\omega }}_{up}^{dr}$$

estimates of the error of the angular velocity (drift) of the azimuthal (course) gyroscope is compensated in block 3 of the calculation of linear and angular velocities. Compensation is made by simply subtracting the resulting drift estimate from the angular velocity signal.

For the proposed system to work, before the general start of the object’s movement, the SINS is displayed in the horizon (the initial angles of the course and pitch are determined), and only after the start of the movement, the system is displayed in azimuth and the drift of the directional gyro is estimated using the signal from the SNA. After that, the system can start working offline without SNA, using only the signal from the odometric system.

Figure 2 presents the error SINS on the geographical coordinates of latitude and longitude in offline mode (with unavailable SNA) of the proposed system and prototype. Coordinate calculation errors are calculated in accordance with the equations of the prototype algorithm, which is a classic navigation solution algorithm for calculating errors, and compared with the calculation of the proposed device. At the same time, the data from field tests are used as “raw” input signals. When comparing the graphs, one can see a critical increase in the accuracy of the numbering of coordinates over a long time (about several thousand seconds) of the autonomous operation of the proposed system.

The proposed technical system has been successfully tested and implemented by TeKnol LLC (Russia) in the installation of the BINS-TEK product for various types of land vehicles.

Claims (1)

An average-format strap-down integrated navigation system for a mobile ground object, containing a block of sensitive elements (SE), consisting of three accelerometers and three angular velocity sensors along three orthogonal axes, an acceleration conversion unit from the coordinate coordinate system connected to the navigation system, a linear and angular velocity calculation unit, and geographical coordinates, block for generating damping signals, first and second blocks of quaternion calculations, block for computing the matrix of guiding cosines and angles in the orientation of the system, a signal receiver of the satellite navigation system (SNA), a block for determining the signal quality of the SNA, a vector signal switcher, first and second adders-subtractors of vector signals, a block of course angle correction, as well as a course gyro drift, a stop detector block, an odometer block systems; while the outputs of the linear acceleration signals of the accelerometers of the SE block are sent to the first input of the acceleration conversion unit from the coordinate system connected to the navigation system, and the first output of the conversion unit signals is connected to the first output signal of the direction cosine matrix of the calculation unit of the matrix of direction cosines of the matrix and orientation angles of the system; the outputs of the angular velocities of the speed sensors of the SE block go to the first input of the first block of quaternion calculations, the output of which is connected to the first input of the second block of quaternion calculations, the output of which is connected to the input of the block calculation matrix of the guiding cosines and orientation angles and to the second feedback input of the first block of quaternion calculations ; the output of the acceleration signals from the acceleration conversion unit from the coordinate coordinate system connected to the navigation system is connected to the first input of the linear and angular velocity and geographical coordinates calculation unit; Three signals are received from the SNA signal receiver, the first of which is the vector linear velocity signal of the object according to the SNA is fed to the positive input of the first adder-subtractor, the second signal of communication quality with the SNA is fed to the input of the SNA signal quality determination unit, the output of which is connected to the control input switch, and the third signal of the path angle of the object according to the SNA is fed to the first input of the course angle correction unit, as well as the drift of the directional gyroscope; the second input of the indicated correction unit is connected with the output of the signal of the heading angle of the system from the calculation unit of the matrix of guide cosines and orientation angles, and the third input of the specified correction unit is connected to the output of the stop detector unit, the first input of which is connected to the output of the acceleration signal from the acceleration conversion unit from the coordinates connected to the navigation system, and at the second input of the stop detector block, angular velocity signals from the SE block are received; vector signal of the linear speed of the system from the third output of the block for calculating linear and angular velocities and geographical coordinates is fed to the subtraction inputs of the first and second adders-subtracters, the outputs of which are connected to the corresponding inputs of the above switch; the positive input of the second adder-subtractor receives a speed signal from the odometric system unit, the input of which receives the output signal of the course of the entire system from the block calculating matrix of guiding cosines and orientation angles; the output of the switch is connected to the input of the damping signal generation unit and the second input of the linear and angular velocity and geographical coordinates calculation unit, the third and fourth inputs of which are connected to the corresponding first and second outputs of the course angle correction unit, as well as the course gyro drift; the vector signal of the absolute angular velocity of the navigation trihedron from the first output of the block for calculating linear and angular velocities and geographical coordinates is fed to the second input of the second block of quaternion calculations, the third and fourth inputs of which receive the first and second correcting signals of angular velocities, respectively, from the second output (vertical control signal angular velocity) from the block for calculating linear and angular velocities and geographical coordinates and from the output of the block for generating signals firovaniya; the third and fourth outputs of the block for calculating linear and angular velocities and geographical coordinates are respectively the outputs of the entire system in linear velocity and geographical coordinates of the object; the second, third and fourth outputs of the signals of the orientation angles of the block calculating the matrix of guide cosines and orientation angles are the corresponding outputs of the system at the angles of the course, pitch and roll of the object.

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