JPH01297400A - Navigation device - Google Patents

Abstract

PURPOSE:To detect the position and speed of a user with high precision by calculating the parameter as the index of the navigation precision from the geometrical relation between an artificial satellite for assisting navigation and a user and determining the gain for correcting the transmission error according to the variation of the calculated values. CONSTITUTION:In a navigation system 4 provided for a user, a receiver 5 which receives and demodulates the signals supplied from an artificial satellite 2 for assisting navigation and measures the relative distance and relative speed between the user and the satellite 2 and decodes the information for calculating the position and speed of the satellite 2 is installed. Further, a navigation calculating device 6 which calculates each estimated error of the absolute position and speed of the user which is transmitted from a dynamic model in which the movement of the user is described, in the valve of the parameter which forms the index of the navigation system and precision from the geometrical relation between four satellites for assisting navigation and the user and determines the gain for correcting the transmission error according to the variation of the value and corrects the transmission error of the absolute position and speed of the user is installed. The result of the calculation is displayed on a display device 10.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides navigation aids by equipping a plurality of satellites in different earth orbits with transmitters capable of accurate locking and spread spectrum communication. By using a dedicated receiver to receive and process signals on the earth's surface, in the air, or in outer space, the absolute position and velocity of the user equipped with the receiver can be determined in real time. It is related to the navigation device that determines.

[Conventional technology]

Figures 3 and 4 are an example of NAVIGATION.
(VOL.

25, Mu2. GPS ((
31obalPositioning System)
As seen in the example above, artificial satellites for navigation support were used to determine three-dimensional absolute position and velocity on the earth's surface, in the air, or in outer space. This is a diagram showing the configuration of a navigation device, and in Figure 1, 111 is the earth, (2) is a navigation support satellite orbiting the earth, (3) is a ground station that manages the navigation support satellite, ( 4) is a navigation device. The navigation device (4) is composed of a dedicated receiver (5) for receiving signals from an artificial satellite for navigation support, a navigation calculation device 1 [61, a navigation result display device], and a navigation calculation device! +61 is a state quantity propagation section (7) and a gain calculation section (8).

It is composed of a state quantity update unit (9), a covariance propagation unit αD, and a covariance update unit @.

In addition, in Figure 3, other devices in an artificial satellite for navigation support, such as a navigation signal transmitter, are used as source devices.

Although an attitude control device, a tracking and telemetry command device, a gas jet device, a structure, etc. are required, they are omitted because they are not directly relevant to the explanation of this invention.

Next, the operation will be explained. In such a device, in order to determine the absolute position and speed of a user equipped with this navigation device using a navigation support satellite, it is necessary to . A dedicated receiver (5) receives a signal that is spread spectrum modulated using a specific code that includes information for calculating the position and speed of an artificial satellite for navigation support, and performs spectrum despreading by knowing the specific code in advance. The transmitted signals are demodulated and decoded, and the predicted values of the position and speed of each navigation support satellite are calculated based on the decoded information.

The phase of the received signal, Dovplaschiff), was obtained by measuring f. The relative distance and speed information between the navigation support satellite and the user equipped with the navigation device is processed using a Kalman filter in the navigation calculation unit (6) to determine the user's absolute position and speed with high precision. do.

The navigation calculation unit (6) uses a Kalman filter to determine absolute position and velocity with high precision.

The state quantity propagation unit (7
) by using the user's dynamics model, and the covariance propagation unit Oυ
, and based on the calculated covariance, the gain calculation unit (8) periodically calculates the Kalman gain necessary for updating the state quantity and covariance, and based on the result, It is obtained from the dedicated receiver (5) in the state quantity update unit (9) and the covariance update unit α2. Predicted position and speed of each navigational support satellite, and relative distance between the navigational support satellite and the user carrying the navigation device.

Using the relative velocity information, the user position and velocity propagation error calculated by the state quantity propagation unit (7) and the covariance propagation unit 0υ and the covariance value at that time are corrected.

[Problem to be solved by the invention]

Since the conventional navigation device is configured as described above, in order to determine the absolute position and velocity with high precision using a Kalman filter within the navigation device.

In addition to propagating the position and velocity based on the user's dynamics, it is also necessary to propagate the covariance as well.The gain of the Luman filter is calculated periodically based on the covariance value. In addition to correcting the propagation error, it is necessary to correct the covariance value itself, which poses problems such as the possibility of overloading other processing and the possibility of making real-time processing impossible.

Further, depending on the power of the computer used, the application of the Kalman filter itself may become impossible, which is a frequent problem.

This invention was made to solve the above-mentioned problems, and it is possible to reduce the calculation load required for navigation calculations and obtain highly accurate position and speed information of the user through real-time processing. The purpose is to obtain equipment.

[Means to solve the problem]

The navigation device t according to the present invention uses the Kalman filter as it is, propagates the covariance, calculates the Kalman gain for correcting the propagation error based on the propagated covariance, and updates the covariance based on the result. Instead, GD, which is a parameter that is an index of navigation accuracy, is calculated from the geometric relationship between the four navigation support satellites used for navigation and the user.
Calculate the value of OP, Vmax, and use the fact that the value is a function of the change in the covariance value calculated by the Kalman filter at each time point to calculate the gain in the navigation arithmetic unit according to the change in the value of the above parameter. The gain for correcting the propagation error is determined in the section, and the state update section uses a Kalman filter type information processing mechanism to calculate the user's absolute position,
This is an attempt to correct velocity propagation errors.

[For production]

The navigation device according to the present invention receives signals from an artificial satellite for navigation support using a dedicated receiver.

It was determined by demodulating and deciphering the contents. Based on the position of the satellite for navigation support and the user position information obtained by the navigation calculation device, parameters representing the relationship between the placement of the satellite for navigation support, the geometric relationship with the user, and the navigation accuracy are calculated. The four observable satellites that provide the best navigation accuracy are selected, and the gain calculation unit uses the propagation error correction gain determined based on the above parameter values.

The propagation error of the user's position and velocity calculated by the user's Guinamix model in the state quantity propagation section.

Based on the relative distance and speed information between the nine selected four satellites and the user measured by a dedicated receiver, υ is corrected by using a Kalman filter type information processing mechanism, so it is different from conventional Kalman filter calculations. It was needed. It becomes possible to obtain the user's position and velocity with high precision through real-time processing without propagating or updating the covariance, or performing gain calculations based on the covariance.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In Fig. 2, (1) is the earth, and (2) is orbiting the earth, and is always spread spectrum modulated by a specific code. Premix the position and speed of your aircraft 11. A navigation support satellite that sends out signals to measure absolute distance and speed, including information for calculation; (3) is a navigation support satellite that monitors the navigation support satellite; included in the signal sent to the user. A ground station that has the role of regularly uploading information for calculating the position and speed of navigation support satellites to each navigation support satellite, (4) is a navigation device that the user should be equipped with,
It consists of a dedicated receiver (5), a navigation calculation device (6), and a navigation result display device αα.

(5) receives signals from satellites for navigation support.

The signal is demodulated by performing spectrum despreading, and the relative distance and velocity between the user and the navigation aid satellite are measured, and the navigation aid satellite included in the signal is (6) is a navigation calculation device for determining the user's absolute position and speed, and calculates the user's position based on the user's dynamics model. , a state quantity propagation unit (7) that calculates velocity.

A gain calculation unit (8) that calculates parameters indicating the geometric relationship between the user and the navigation support satellite, and calculates gains for correcting propagation errors in position and velocity based on the parameters.
, and a state quantity updating unit (9) that corrects the position and velocity propagation errors calculated in the state quantity propagation unit (7) by a Kalman filter type error correction mechanism based on the results.

In addition, (IQI is a navigation result display device for displaying navigation calculation results such as the type and number of the selected navigation support satellites obtained by the above processing, the user's absolute position, and speed. .

In addition, in Figure 1, other devices 9 that make up the satellite for navigation support are required, such as a dedicated transmitter for navigation, a power supply device, an attitude control device, a tracking and telemetry command device, a gas jet device, or a body structure. However, since it is not directly relevant to the explanation of this invention, it is omitted.

In the navigation device (4), the dedicated receiver (5) demodulates the spread spectrum modulated signal from the navigation support satellite (2) and determines the phase of the signal.

By measuring the Doppler shift, the relative distance and relative speed between the navigation support artificial satellite (2) and the user carrying the navigation device (4) are measured.

The location of the navigational aid satellite included in the signal.

Decipher the information and use the results for speed calculations.

Calculates the position and speed of satellites used as navigation aids during measurements. The measured relative distance and relative velocity are expressed as follows.

Relative distance - (Xs-X)"+(Ys-Y)"+(Zs-
Z)”+b+νi ・fit...(2) However.

(Xs, Ys, Zs) Position of satellite for navigation support (Vxs, Vys, Vzs) Speed of satellite for navigation support (X, Y, Z) User position (■
^Vy, Vz) User speed b User clock bias error n User clock drift error Random error when measuring relative distance Random error when measuring relative speed.

The distance between the navigation aid satellite and the user is determined by the signal transmission time given by the navigation aid satellite's clock, the signal transmission time given by the user's dedicated receiver clock, and the user's Since it is determined by the difference in the signal reception time given by the clock of the dedicated receiver of the satellite, the clock error of the satellite for navigation support and the dedicated receiver of the user is also determined by the relative distance and relative speed as shown in equations 11+ and +21. This is a cause of measurement error.

Therefore, in order to determine position and speed with high precision using a navigation system using this artificial satellite.

It is also necessary to estimate the user's clock error, and for this purpose it is necessary to use four satellites for navigation support.

At this time, in order to select the four navigation support satellites that give the best navigation results, the current user position and the reception Based on the information contained in the signal, a dedicated receiver (5
), select the navigation support satellite (2) that is observable by the user, and select the navigation support satellite (2) that is observable by the user, and select the navigation support satellite (2) that is inversely proportional to GDOP or GDOP. The volume of the tetrahedron created by the four satellites and the user.

This will be used as an evaluation standard for selecting the four optimal satellites.

(]DOP indicates the covariance of the estimation error when estimating the user position and clock error using the least squares method from the relative distance information between the four satellites and the user given by the mountain formula f4 Note 6 According to NAVIGATION (VOL, 25゜2. SUMMER, 1978), if the unit vectors from the user's position to the satellite position for navigation support are e; (i = 1.4), they can be expressed by a quadratic equation. I can do it.

GDOP = 57; A; 7; W... (3) Here, 6xx", 6yy2.6zz2 is the estimated error of the user's position due to the geometric arrangement between the navigation support satellite and the user. The variance kn 6tt'' indicates the estimated error covariance of the clock error.

Also, (It indicates the transposed matrix of the matrix G, and o-1 indicates the inverse matrix of the matrix G.

Therefore, the combination of navigation support satellites that provides the best navigation accuracy is the combination that minimizes the IDOP value. However, (31, (41, (as seen from equation 51, G
Calculating DOP is tedious.

NAVIGATION (VOL, 25.A2.SU
According to MIIR, 1978), there is a relationship between GDOP and the tetrahedral volume ■ created by connecting the vertices of the unit vector eH (i-1, 4) from the user to the navigation support satellite.

GDOP・1/V・・・・・・・・・・・・ (6)
There is a relationship between Here, ~ is a symbol representing a proportional relationship.

Therefore, by selecting four navigation aid satellites whose volumes take the maximum value Vmax k.

The combination of navigation aid satellites that provides the best navigation accuracy can be determined.

By the way, 1. Normal Kalman filter processing is performed according to the following equation.

Propagation of state quantity and covariance x = f (x)・・・・・・・・・・・・・・・
(7) Society=FP+PFt+Q・・・・・・・・・・・・
・ (8) Kalman gain calculation K ・PHt(HPHt+R)・' ・・・・・・
・・・・・・ +91 state quantity, covariance update X+=XL+K(Z・h(Xj)・・・・・・・・・
Scream P+=(I・KH)P・・・・・・・・・・・・ 11
1 Here, the 10 symbol indicates after update, and the - symbol indicates before update.

Also.

X Estimated state quantities (position, speed, clock bias.

(Kurobuku Drift) f (x) User's dynamics model P State quantity error covariance 2 Observed value (relative distance, relative speed between navigation support satellite and user) h(x) Estimated state quantity Used observed value predicted value Q Process noise R Observation error matrix K Kalman gain matrix ■ Unit matrix Here, NAVIGATION (VOL, 25.
A2. SUMMER.

(1978), the value U of GDOP, Vmax,
+31. As is clear from equation (6), 9 selected 4
It is obtained by the least squares method when using four navigational aid satellites. It is a function of the navigation accuracy error covariance at each time point. Utilizing this property, instead of propagating the covariance using equation (8) and calculating the gain for correcting the propagation error based on the result using equation (9) as in a normal Kalman filter, the above parameters can be used. , gain calculation section (
8) GDOP, Srui! Based on the value of Vmax, the Kalman gain is approximately determined by the following equation.

K・Fl(GDOP)Ht(HF,(GDOP)H'+
R)・'... O force=F2(Vmax)Ht(
HF2(Vmax)H'+R)・'...Q31
Here, FB (GDOP), p2 (Vmax)
is the state quantity error covariance matrix P'i GDOP and Vm
This is a gain matrix obtained by approximately expressing it as a function of ax.

Q21. (Using the gain expressed by equation 131, the error in the user's position and velocity calculated by equation (7) using the dynamics model of the user in state quantity propagation unit (9) is transmitted to state quantity updating unit. In (9), correction is performed using a Kalman filter type error correction mechanism.

As a result, instead of the normal Kalman filter processing expressed by equation (7) 2~αυ, 171.1u11. (
By using only IZ, equation (13), the user's absolute position and velocity can be determined, which was required for conventional Kalman filter calculations. It is possible to omit covariance propagation in equation (8), covariance update in equation (111), and gain calculation based on covariance in equation (9).

Furthermore, in order to calculate the gain for error correction, parameters indicating the relationship between the geometric relationship between the user and the navigation support satellite and the navigation accuracy are periodically calculated onboard the aircraft. As explained above, in this case, if the flight route of the user is known in advance, 11 is calculated in advance.

This does not prevent the gain for correcting the propagation error from being determined in advance based on the calculation result, but the purpose is to further increase the calculation speed, reduce the calculation load, and reduce the calculation algorithm compared to the present embodiment. I can do it.

〔Effect of the invention〕

As described above, the navigation device according to the present invention has a large calculation load compared to the conventional navigation calculation device using a Kalman filter.
This is because covariance propagation, updating, and the covariance-based gain meter U part can be omitted.

Significant reduction in the amount of calculations and associated simplification of processing.

High speed can be achieved.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an earth observation device according to the present invention, and FIGS. 3 and 4 are diagrams showing a conventional navigation device using an artificial satellite for navigation support. (1) is the earth, (2) is an artificial satellite for navigation support, (3)
is a ground monitoring station, and (4) is a navigation device that the user should be equipped with. (5) is a dedicated receiver, (6) is a navigation calculation device, (7) is a state quantity propagation unit, (8) is a Kane calculation unit, and (9) is a state quantity propagation unit. QQI is a navigation result display device, OD is a covariance propagation unit, O2
is the covariance update part. In addition, in FIG. 1, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) By equipping multiple satellites in different earth orbits with accurate clocks and transmitters capable of spread spectrum modulation, they can be used as navigational support satellites, and their own position, speed, etc. After a message containing information is spread spectrum modulated using a specific code, it is sent toward the earth, and the signal is received and demodulated by a dedicated receiver on the earth's surface, in the air, or in outer space. Along with position and speed information, the phase of the received signal,
Relative distance and speed information between a navigation support satellite and a user equipped with a dedicated receiver is obtained by measuring the Toppler shift, and this information is used by processing this information with a navigation calculation device. In a navigation device that determines the user's absolute position and speed, the state quantity propagation unit in the navigation calculation device calculates the prediction error of the user's absolute position and speed propagated by the dynamics model that describes the user's movement. Using the geometric relationship between the four navigation support satellites selected for the purpose of the project and the user, and the distance measurement data between the four selected navigation support satellites and the user, GDOP (Geometric Dilutr) is a parameter that indicates the relationship with navigation accuracy when position estimation is performed using the square method.
The user's absolute position and velocity can be calculated with high accuracy through real-time processing, using a propagation error correction gain determined according to the value of icofPrecision, and periodically correcting it using a Kalman filter type information processing mechanism. A navigation device characterized by determining. (2) In the above navigation device, the prediction error of the user's absolute position/velocity propagated by the dynamics model that describes the user's motion in the state quantity propagation section in the navigation calculation device is inversely proportional to GDOP. , the positions of the four navigation aid satellites selected for navigation, and the volume of the tetrahedron with the user position as its apex, the four navigation aid satellites selected for navigation and the user. A Kalman filter-type information processing mechanism is used, using a gain for propagation error correction determined based on the parameter indicating the geometric relationship between A navigation device characterized in that the user's absolute position and speed are determined with high precision through real-time processing, and the absolute position and speed of the user are determined periodically.