RU2539140C1 - Integrated strapdown system of navigation of average accuracy for unmanned aerial vehicle - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: invention can be used in small-sized strapdown inertial navigation systems (SINS) integrated with a variety of external systems of unmanned aerial vehicles (UAVs). SINS comprises: a unit of sensing elements (SE), a unit of calculation of linear and angular velocities and geographical coordinates, a unit of generating the signals of damping, the units of quaternion calculations, the unit of calculation of the matrix of directing cosines and angles of orientation, the receiver of signals of satellite navigation system (SNS), the unit of determining the quality of SNS signal, the switch of vector signals, the first and second adders-subtractors of vector signals, the unit of air data system (ADS), the unit of determining the heading error, the unit of determining and correction of the wind speed.

EFFECT: improvement of accuracy.

2 dwg

Description

Technical field

The invention relates to the field of small-sized strapdown inertial navigation systems (SINS), integrated with various external sensor systems of navigation information, for unmanned aerial vehicles (UAVs).

State of the art

The use of small-sized SINS with "coarse" and medium-precision sensitive elements (SE) is described in a number of US patents of the 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 an external corrector such as a satellite system (GPS type), which is crucial for their use in unmanned aircraft.

The main disadvantage of the SINS data is the impossibility of long-term operation of the system without a satellite navigation system (SNA) (or GPS - Global Positioning System), for which it is possible to organize the production of active jamming (GPS jamming).

The closest analogue (prototype) to the proposed device can be recognized as an integrated strapdown satellite system based on “coarse” sensing elements (RF patent No. 2380656, IPC G01C 23/00, published on January 27, 2010). This system performs error damping using the difference between the SINS and SNA accelerations.

The main limitation of such a SINS is the fact that it calculates the speeds and coordinates in the case of using the SNA. If the CHC does not provide a navigation solution, the considered SINS does not calculate current speeds and coordinates.

The main objective of the invention is a significant increase in the accuracy of calculating coordinates in an autonomous mode, which is a key point in the use of UAVs.

Disclosure of invention

To achieve a technical result, the device integrated medium-format integrated navigation system for an unmanned aerial vehicle 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,

the first and second blocks of quaternion computing,

block for calculating the matrix of guide cosines and orientation angles,

SNA signal receiver

unit for determining the signal quality of the SNA,

vector signal switch

first and second adders-subtractors of vector signals,

course error determination unit,

unit for determining and correcting wind speed,

air signal system (SHS) unit.

The set of connections of various signals between the blocks and switching links in different maneuvers of the SINS carrier vehicle can be described in essence 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.

Two signals are received from the SNA signal receiver, the first of which is the vector signal of the apparatus’s linear speed, according to the SNA data, goes to the positive input of the first adder-subtractor, as well as to the first input of the heading error determination unit and to the first input of the wind speed detection and correction unit; the second signal - the signal quality of communication with the SNA is fed to the input of the SNA signal quality determining unit, the output of which is connected to the control input of the vector signal switch.

The vector signal of the linear velocity of the V _INS system from the third output of the linear and angular velocity and geographical coordinates calculation unit is fed to the second input of the heading error determination unit, to the second input of the wind speed determining and correction unit, as well as to the subtraction inputs of the first and second adders-subtractors, the outputs of which are connected to the corresponding inputs of the above switch.

At the positive input of the second adder-subtractor, as well as at the third feedback input of the wind speed determination and correction unit, a speed signal is received from the SHS unit, the input of which receives speed signals from the wind speed determination and correction unit, the fourth input of which receives the course output signal the entire system from the second output of the block computing matrix of the 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 geographic coordinates calculation unit, the third input of which receives a course error signal from the output of the course error determination unit.

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 respectively receive the corrective angular velocity control signals from the second output from the linear and angular calculation block speeds and geographical coordinates and angular velocity damping signals from the output of the damping signal generation block.

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 speed (or its components) and geographical coordinates of the device.

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

To significantly improve the accuracy of calculating the speeds and coordinates of UAVs in the autonomous mode when using “coarse” or mid-range CE BINS, the integrated SINS, in addition to the SNA, introduced a SHS with a unit for determining and correcting wind speed and direction, as well as with a system display unit in azimuth movable base. In this case, the unit for determining and correcting wind speed and direction functions not only in the presence of the SNA signal, but also in its absence - while the correction of wind signals is carried out only by inertial information. And at the same time, unconventional damping from SHS was also used. 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 the offline numbering mode using the SHS signal.

List of drawings

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

Figure 2 - comparison of timelines of the errors of determining the coordinates of the proposed device and the prototype in the absence of a signal of the SNA.

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 - block communication system with the SNA; 9 - block determining the signal quality of the SNA; 10 - switch; 11 - the first adder-subtractor; 12 - second adder-subtractor; 13 - block error rate determination; 14 - unit for determining and correcting wind speed; 15 - block system of air signals.

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;

- вектор управляющих (корректирующих) сигналов угловой скорости для вычислительной платформы; $${\omega }_{\mathrm{one}}^c$$

- vector of control (correcting) angular velocity signals for a computing platform;

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

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

- вектор сигналов демпфирования вычислительной платформы по угловой скорости;from block 4: $${\omega }_2^c$$

- the vector of the damping signals of the computing platform in angular velocity;

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: apparatus orientation angles (system output signals): H - course, курс - 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 (or V (GPS)) - the vector of the linear velocity of the device relative to the Earth, determined by the SNA and its sensors;

from block 15: V _SHS — linear directional speed of the apparatus, determined by the system of air signals (SHS) taking into account wind speed;

from block 14: U _N , U _E - components of the wind speed in the north and east directions;

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

- 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 adder-subtractor 11: $$\delta {\widehat{V}}_{\mathrm{one}}$$

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

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

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

- оценка ошибки системы по курсу.from block 13: $$\delta \widehat{H}$$

- assessment of system error at the rate.

Information and signal exchange between the inputs and outputs of the blocks is carried out along the communication lines shown on the block diagrams by solid thin lines. Communication lines are known lines of communication and information exchange, for example, through 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 and helicopter complexes. Types of functional communications. Types and levels of electronic signals).

System device

To improve the accuracy of autonomous calculation of coordinates and speed 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 аппарата (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.The magnitude of the signals of angular velocities ω _b measured by the CRS of block 1 calculates the elements of the quaternion of the final rotation from the associated coordinate system to the inertial (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 device (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: $$a_N=C_b^N{a}_b$$

.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: $$a_N=C_b^N{a}_b$$

.

Then, in block 3, the linear and angular velocities of the apparatus are calculated in the navigation coordinate system and the geographical coordinates of the apparatus 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 indications of ANNs and SHS (adder-subtractor 12 vector signals). Switching the operating mode of the 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.

To calculate the ground speed from the SHS signals (block 15), it is necessary to add the components of the wind speed U _N , U _E to the true air speed V _air . These components are determined in block 14 determining and correcting wind speed:

U _N = V _N (GPS) -V _air cosH

U _E = V _E (GPS) -V _air sinH

Here V _N (GPS), V _E (GPS) - components in the north and east directions of the signal speed V _CHC from block 8 of the SNA;

V _air is the true airspeed measured by the SHS (in block 15);

H is the true course angle from the exit of the entire system (from block 7).

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 $$-K^b\delta {\widehat{V}}_N$$

, $$-K^b\delta {\widehat{V}}_E$$

в блоке 4, и все эти демпфирующие сигналы поступают на соответствующие корректирующие входы второго блока кватернионных вычислений 6.Vector Difference Selected by Switch 10 $$\delta \widehat{V}$$

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 $$-K^b\delta {\widehat{V}}_N$$

, $$-K^b\delta {\widehat{V}}_E$$

in block 4, and all these damping signals are fed to the corresponding correction inputs of the second block of quaternion calculations 6.

). Так, например, в слабоманевренном полете K=1,4 1/c, K^b=0,05 1/метр, а в ощутимом маневре K=0,2 1/c, K^b=0,001 1/метр.The novelty of the system lies in the fact that the damping coefficients K and K ^b decrease stepwise in the maneuver of the device (the maneuver is determined by comparing the derivative of the course angle with the threshold of the rate of change of course $$\dot{H}<\mathrm{one}gR\mathrm{but}d/\mathrm{from}$$

) So, for example, in a weakly maneuverable flight K = 1.4 1 / s, K ^b = 0.05 1 / meter, and in a tangible maneuver K = 0.2 1 / s, K ^b = 0.001 1 / meter.

по угловой скорости для вычислительной платформы и из блока 4 сигналы демпфирования вычислительной платформы $${\omega }_2^c$$

по угловой скорости.As a result, the corresponding inputs of the 2nd quaternion block 6 go from block 3 signals: the absolute angular velocity vector ω _{N of the} navigation trihedron to control the computing platform, the control (correcting) damping signals $${\omega }_{\mathrm{one}}^c$$

in angular velocity for the computing platform and from block 4, the damping signals of the computing platform $${\omega }_2^c$$

angular velocity.

.An important new point is the calculation of the components of the wind speed for the case when the SNA signals cannot be used even with a rather weak maneuver of the aircraft $$\dot{H}<0,\mathrm{one}gR\mathrm{but}d/\mathrm{from}$$

.

,

, в качестве составляющих сигналов ускорения

,

используют не текущие мгновенные значения, а значения, сглаженные фильтром низких частот (например, апериодическим звеном). Величину порога по ускорению δ выбирают в пределах 0,1…0,2 м/с² в зависимости от типа БПЛА.In this case, in block 14, the speed signals V of the _ANN calculate the acceleration components smoothed out by the low-pass filter a _N , a _E in the north and east directions, then the modulus of the difference of these components and components (with the layout of the sine and cosine of the current heading angle) of the accelerations calculated according to the readings of the SHS signals, they are compared with a given threshold value for acceleration δ:

,

as components of acceleration signals

,

they do not use current instantaneous values, but values smoothed by a low-pass filter (for example, an aperiodic link). The value of the acceleration threshold δ is selected in the range 0.1 ... 0.2 m / s ² depending on the type of UAV.

If the threshold condition is met, then it is believed that the wind speed has not changed.

If the threshold condition is not satisfied, then the components U _N , U _E of the wind speed in the north and east are adjusted according to the corresponding integral formulas:

, $$V_N^L(GPS)$$

- последние (верхний индекс L - от английского слова last - последний) запомненные значения составляющих в северном и восточном направлениях сигнала скорости V_CHC аппарата из блока 8 СНС на момент пропадания сигнала СНС (GPS).Here $$V_E^L(GPS)$$

, $$V_N^L(GPS)$$

- the last (upper index L - from the English word last - last) stored values of the components in the north and east directions of the signal of speed V _{CHC of the} device from block 8 of the SNA at the time of the disappearance of the SNA signal (GPS).

To determine the heading error in flight, use the heading block 13 for determining the heading error, which implements the Kalman filter for the following system model (as the model, the ANS error equations are used that relate speed errors, heading errors and intrinsic errors of the SE sensors):

$${\dot{F}}_E=-\frac{\delta V_N}{R}+w_{\mathrm{one}}(t)$$

$${\dot{F}}_N=\frac{\delta V_E}{R}+w_2(t)$$

- при интегрировании получаем ошибку курса $$\delta \widehat{H}$$

. $${\dot{F}}_{up}=w_3(t)$$

- when integrating, we get a course error $$\delta \widehat{H}$$

.

Here Ф _N , Ф _E are the components of horizontal errors in the north and east directions, Ф _up is the error in azimuth (course error); w ₁ (t), w ₂ (t), w ₃ (t) - white input noise; δV _E , δV _N are the components of the ANN errors in speed in the north and east directions. This error is the difference between V _VNS and V _SNA (the same as V (GPS)).

Measurement Model:

$$z=\underset{H}{\underbrace{\left[\begin{array}{ccccc}\mathrm{one}& 0& 0& 0& 0\\ 0& \mathrm{one}& 0& 0& 0\end{array}\right]}}\left[\begin{array}{l}\delta V_E\\ \delta V_N\\ F_E\\ F_N\\ F_{up}\end{array}\right]+V(GPS)$$

из блока 13 подают в блок 3 для формирования сигнала корректирующей угловой скорости $${\omega }_1^c=-\frac{\delta \widehat{H}}{h_{N3}}=-\frac{{\widehat{Ф}}_{up}}{h_{N3}}$$

(где h_N3 - период дискретизации вычислений сигнала), передаваемой во второй блок кватернионных вычислений 6.Heading Error Signal $$\delta \widehat{H}$$

from block 13 is fed to block 3 to generate a signal of the correcting angular velocity $${\omega }_{\mathrm{one}}^c=-\frac{\delta \widehat{H}}{h_{N3}}=-\frac{{\widehat{F}}_{up}}{h_{N3}}$$

(where h _N3 is the sampling period of the signal calculations) transmitted to the second block of quaternion calculations 6.

Before take-off, UAVs exhibit SINS into the horizon (determine the initial course and pitch angles) and only when take-off, if there is a signal from the SNA, they exhibit in azimuth and determine the course error. Then, using the SNA signal, the components of the wind speed are determined. In the case when the SNA signal is unavailable, it is possible to carry out the correction of the wind speed signal only by inertial information, which is fundamental to ensure a sufficiently long operation of the system in standalone mode.

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. Errors of the numbering of coordinates are calculated in accordance with the equations of the prototype algorithm 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 (of the order of several thousand seconds) of the autonomous operation of the proposed system.

The proposed technical system was implemented by TeKnol LLC (Russia) in the device device CompaNav-3 and passed a complete series of tests for various types of UAVs.

Claims (1)

An integrated strapdown medium-accuracy navigation system for an unmanned aerial vehicle, containing a block of sensitive elements (SE), consisting of three accelerometers and three angular velocity sensors along three orthogonal axes, a unit for calculating accelerations from the coordinate system connected to the navigation system, a block for calculating linear and angular speeds and geographical coordinates, a block for generating damping signals, the first and second blocks of quaternion computations, a block for calculating the matrix of guide cosines and orientation fishing, satellite navigation system (SNA) signal receiver, SNA signal quality determination unit, vector signal switch, vector and second adders-vector signal adders, course error determination unit, wind speed detection and correction unit, air signal system (AHS) unit ; while the outputs of the linear acceleration signals of the accelerometers of the SE block are fed to the first input of the acceleration conversion unit from the coordinate system connected to the navigation system, and the output of the directional cosines matrix signals of the calculation unit of the directional 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 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; two signals are received from the SNA signal receiver, the first of which is the vector signal of the apparatus’s linear speed according to the SNA data and is fed to the positive input of the first adder-subtracter, as well as to the first input of the heading error determination unit and to the first input of the wind speed determining and correction unit; the second signal - the signal quality of communication with the SNA is fed to the input of the SNA signal quality determining unit, the output of which is connected to the control input of the vector signal switch; the vector signal of the linear velocity of the system from the third output of the block for calculating linear and angular velocities and geographical coordinates is fed to the second input of the unit for determining the error of the course, to the second input of the unit for determining and correcting the wind speed, and also to the subtraction inputs of the first and second adders-subtracters, the outputs of which connected to the corresponding inputs of the above switch; the positive input of the second adder-subtractor, as well as the third feedback input of the wind speed determination and correction unit, receives a speed signal from the SHS unit, the input of which receives speed signals from the wind speed determination and correction unit, the fourth input of which receives the course output signal the entire system from the second output of the block computing matrix of the guide 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 input of which receives a course error signal from the output of the course error determination unit; 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 respectively receive the corrective angular velocity control signals from the second output from the linear and angular calculation block speeds and geographical coordinates and angular velocity damping signals from the output of the damping signal generation block; 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 apparatus; 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 according to the angles of the course, pitch and roll of the apparatus.

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