RU2584091C1 - Method for real-time monitoring of integrity of navigation field of global navigation satellite system - Google Patents

Abstract

FIELD: navigation system.

SUBSTANCE: invention relates to satellite navigation and can be used for real-time monitoring of navigation field integrity of global navigation satellite system (GNSS). Technical result is that together with consumer navigation equipment (CNE) place the storage equipment for consumer time scale and hardware of high-precision comparison of consumer time scale with GNSS system time scale, synchronise consumer time scale with GNSS system time scale, record time of receiving navigation message from spacecraft (SC) GNSS according to consumer time scale, determine pseudo range between each SC and consumer equipment, determine one set of consumer coordinates by three values of pseudo range. Obtained sets are analysed, several sets of consumer coordinates are obtained, SC GNSS is detected, navigation messages of which must not be used for navigation solutions.

EFFECT: broader functional capabilities.

1 cl, 1 dwg

Description

The invention relates to satellite navigation and can be used to control the integrity of the navigation field of the global navigation satellite system (GNSS). Under the integrity control of the GNSS navigation field, we understand the ability of the system to provide timely warning of those times when the whole system or individual spacecraft (SC) of the system should not be used for navigation definitions [1, p. 440].

There is a method of monitoring the integrity of the GNSS navigation field, in which GNSS spacecraft carry out continuous autonomous monitoring (self-monitoring) of the functioning of the main onboard systems [1, p. 337]. The autonomous control method provides that when unpaired violations of the normal functioning of the main onboard systems are detected that affect the quality of the navigation signal emitted by the spacecraft and the reliability of the transmitted navigation message, a sign of its malfunction is formed, which is transmitted to the system consumer as part of the operational information of the navigation message [1, p. . 337].

The disadvantage of this method of control is its incompleteness. So the means of self-monitoring are designed to detect not all possible violations in the operation of on-board systems, the malfunctions of the control devices themselves are not detected and are not accompanied by the transmission of the corresponding message to consumers, the distortion of the ephemeris cannot be detected on the GNSS spacecraft [1, p. 338].

A known method of monitoring the integrity of the GNSS navigation field, in which the quality of the navigation field is analyzed by the ground control and correction station (KKS), which includes reference measuring stations with known coordinates and transmitting means [1, p. 355-359]. At the same time, navigation messages of visible GNSS satellites are received at reference measuring stations. On the KKS, differential corrections are calculated and transmitted to consumers for the correct processing of navigation messages during navigation definitions.

The disadvantages of the described method are:

- a local customer service zone, since the service range of one KKS is about 300 km [1, p. 357];

- the influence of the ionosphere on the propagation of the radio signal of the navigation message received by the CCS, which can lead to its distortion of the message and as a result of an incorrect result of the analysis of the quality of functioning of the GNSS spacecraft;

- the cost of resources for the creation and operation of the KKS.

A known method of monitoring the integrity of the GNSS navigation field, in which the quality of the navigation field is controlled by special equipment that is part of the ground subsystem of control and management, field monitoring equipment (AKP) [1, p. 338]. After detecting a malfunction of the onboard equipment of some GNSS spacecraft, the field monitoring equipment provides the formation of a malfunction sign of this spacecraft and the transmission of the sign in the almanacs of all GNSS spacecraft.

The disadvantages of this method are:

- low efficiency of consumer notification when a GNSS SC malfunction is detected, since a significant length of time is allowed from the moment the malfunction is detected to the sign of a malfunction in the spacecraft navigation message (the inclusion of the sign in the almanacs of all the SC of the system must be provided no later than 16 hours [1 , p. 338]);

- the influence of the ionosphere on the propagation of the radio signal of the navigation message, which can lead to its distortion and as a result of an incorrect result of the analysis of the quality of functioning of the GNSS spacecraft;

- the cost of resources for the creation and operation of automatic transmissions.

There is a prototype method for monitoring the integrity of the GNSS navigation field, in which the analysis of navigation signals is carried out by the consumer by using the excess navigation information received in the navigation equipment of consumers (NAP) from various visible GNSS spacecraft [1, p. 339]. So, taking signals from more than four visible GNSS spacecraft, only four spacecraft make navigation determinations from the navigation messages. Various combinations of four spacecraft are selected from all visible spacecraft; several sets of consumer coordinates are obtained. For example, having received signals from five spacecraft, you can get five sets of consumer coordinates. They analyze the obtained sets and confirm the correctness of the received navigation messages or identify the GNSS satellite, the navigation messages of which should not be used for navigation definitions [1, p. 339]. The described method can be implemented if the NAP receives navigation messages from at least five different GNSS spacecraft.

A significant advantage of the method is the ability to quickly identify directly in the navigation equipment the consumer of the GNSS spacecraft broadcasting incorrect navigation messages that should not be used in the NAP for navigation definitions.

The disadvantage of the described method is the impossibility of monitoring the integrity of the navigation field if less than five GNSS satellites are in the radio visibility zone of the NAP. The need to solve the problem of monitoring the integrity of the navigation field when processing less than five navigation messages can be urgent in cases of decreasing the number of KA GNSS groups, reducing the ability to receive navigation messages in a mountain or forest area, urban conditions.

The problem to which the claimed invention is directed, is to provide the ability to control the integrity of the navigation field if the number of GNSS spacecraft in the radio visibility zone of the NAP is more than three GNSS spacecraft.

The main technical result achieved by the claimed invention is the operational detection of a malfunction of some GNSS satellite transmitting an incorrect navigation signal, if the number of GNSS spacecraft in the radio visibility zone of the NAP is not less than four GNSS spacecraft.

The essence of the invention lies in the fact that to control the integrity of the navigation field of the global navigation satellite system, navigation equipment of the consumer is used, navigation messages of spacecraft located in the radio visibility zone are received, navigation definitions are made, while some of the received navigation messages are used, several sets of consumer coordinates are received , analyze the received sets, confirm the correctness of the received navigation messages or identify a spacecraft whose navigation messages should not be used for navigational determinations, according to the invention, together with the consumer navigational equipment, they place the consumer’s timeline storage equipment and high-precision comparisons of the consumer’s timeline with the system timeline of the global navigation satellite system; before navigational determinations, they synchronize the scale timestamp with global navigation satellite system timeline system, when conducting navigation determinations, the time of receiving the navigation message of each spacecraft of the global navigation satellite system is recorded on the consumer’s time scale, using which the pseudorange between each spacecraft and the consumer’s equipment is determined, navigation messages of at least four spacecraft are received, one set of consumer coordinates is determined by three pseudorange values.

In accordance with the claimed method, when receiving four navigation messages, four sets of consumer coordinates are received. Using the obtained sets, they confirm the correctness of the received navigation messages or identify the spacecraft of the global navigation satellite system, the navigation messages of which should not be used for navigation determinations.

The basis of the invention is the ability to determine the coordinates of the consumer from navigation messages received from three GNSS satellites, if the consumer’s time scale coincides with the GNSS system time scale.

It should be noted that the principles of navigational definitions implemented in modern GNSS do not require the coincidence of the NAP timeline with the GNSS system timeline. The use of GNSS signals makes it possible to determine the coordinates of the consumer of navigation information after receiving navigation messages transmitted by four GNSS satellites simultaneously. To determine the three coordinates of the consumer and the deviation of the NAP timeline from the GNSS system timeline, a system consisting of four equations is used

where x, y, z are the desired coordinates of the consumer; x _j , y _j , z _j - coordinates of the GNSS spacecraft j = 1 (1) 4 transmitted as part of navigation messages; C is the speed of light; t _j is the propagation time of the navigation message signal from the j-th GNSS spacecraft to the NAP; τ is the deviation of the NAP timeline from the GNSS system timeline.

The claimed method provides that the time scale of the NAP coincides with the GNSS system time scale. Then provided

from (1) we get

From the system of equations (3) it follows that under condition (2) the coordinates of the consumer can be determined from the navigation messages of the three GNSS satellites.

The essential features characterizing the invention.

1. Placement together with GNSS consumer navigation equipment of storage equipment of the consumer’s timeline and equipment of high-precision comparisons of the consumer’s timeline with the GNSS system’s timeline.

2. Determination of one set of consumer coordinates by three pseudorange values between the spacecraft and consumer equipment, in contrast to the prototype method, in which at least four navigation messages received from different GNSS spacecraft are required to determine one set of consumer coordinates.

3. Synchronization of the consumer’s timeline with the GNSS system timeline in preparation for navigational definitions and monitoring the integrity of the navigation field.

In the prototype method, synchronization of the consumer’s timeline with the system timeline is not required, since the deviation of the consumer’s timeline from the system’s timeline is determined when processing navigation messages by including the deviation in the required parameters. However, to determine such a deviation, at least four navigation messages transmitted by different GNSS spacecraft are required. And when solving the system of equations (1), the sought quantities are x, y, z, τ. Therefore, using only four pseudorange values, only one set of consumer coordinates is calculated, and it is not possible to control the integrity of the navigation field when receiving navigation messages from four GNSS spacecraft.

4. The following set of sequential actions to control the integrity of the navigation field:

- synchronization of the consumer timeline with the GNSS system timeline before navigational definitions;

- determination of the pseudorange between the GNSS spacecraft and consumer equipment;

- determination of one set of consumer coordinates by three pseudorange values;

- identification of GNSS spacecraft, whose navigation messages should not be used for navigation definitions, by analyzing several sets of consumer coordinates, each of these sets being calculated according to three pseudorange values.

The main features that distinguish the claimed method from the prototype method.

1. To measure the pseudorange between the consumer equipment and the GNSS spacecraft, a consumer time scale is used, which coincides with the GNSS system time scale.

Comparison of the consumer’s time scale with the system time scale makes it possible to eliminate the pseudorange error caused by the difference in the consumer time scale from the system time scale in subsequent calculations, in contrast to the prototype method in which such a difference must be taken into account when determining the coordinates of the consumer.

2. The absence of an error in determining the pseudorange caused by the difference between the consumer’s time scale and the system time scale allows calculating the consumer’s coordinates using three pseudorange values, in contrast to the prototype method, in which corrections to the time scale are determined when calculating the consumer’s coordinates and use at least four pseudorange values to different GNSS spacecraft.

It should be emphasized that the coincidence of the consumer’s time scale and the system time scale means the unity of the reference point and the equality of the sizes of time units and the frequency of such time scales.

When compared with the prototype method, the claimed method has the following advantages.

If there are only four GNSS spacecraft in the radio visibility zone of the NAP, the coordinates of the consumer can be determined by the four navigation messages transmitted by them. However, the application of the prototype method does not allow the integrity of the navigation field to be checked by the navigation messages of four GNSS spacecraft. In the absence of control of the integrity of the navigation field, the coordinates of the consumer may not be calculated correctly. The advantage of the claimed method is the possibility of analyzing the integrity of the navigation field when receiving navigation messages of a smaller number of GNSS spacecraft than in the prototype method.

It should be emphasized that with a fully deployed GNSS orbital constellation, in an open area in the radio visibility zone of the consumer, there are usually more than four GNSS satellites, therefore, the use of the prototype method is possible. However, in conditions of limited visibility, for example, in a mountain or forest area, there are obstacles to the distribution of navigation signals. Therefore, the advantage of the claimed method is the ability to control the integrity of the navigation field on the navigation messages of only four GNSS spacecraft.

The application of the claimed method involves the comparison of the consumer timeline with the GNSS system timeline. Obviously, the requirements for the frequency of comparisons depend on the stability of the frequency standard of the consumer time reference. If a standard with characteristics close to the time standard set on the GNSS spacecraft is used in the consumer’s time standard, the interval between the scale comparisons should be about 12 hours.

A block diagram of a device for implementing the proposed method is presented in FIG. one.

The device comprises consumer 1 navigation equipment, consumer 2 timeline storage equipment, high-precision comparisons of consumer timeline with GNSS system timeline 3, on-board digital computer (BTSC) 4.

In this case, the output of NAP 1 is connected to the first input of the BCMC 4, the second output of the storage equipment of the consumer timeline 2 is connected to the second input of the BCMC 4, the first output of the storage equipment of the consumer timeline 2 is connected to the input of the equipment of comparisons of the consumer 3 time scale, the output of the equipment of high-precision comparisons 3 connected to the input of the storage equipment of the consumer timeline 2.

The device operates as follows.

The consumer 3 timeline comparisons equipment receives GNSS satellite navigation messages, receives the reference values, sizes of time and frequency units from the consumer 2 timeline storage equipment, and synchronizes the consumer’s timeline with the GNSS system timeline. NAP 1 receives navigation messages transmitted by the GNSS spacecraft, then the parameters contained in the navigation messages are received in the digital computer 4. From the equipment 2 in the digital computer 4 the data of the consumer timeline are received.

The digital computer 4 determines the pseudorange between each spacecraft and the consumer’s equipment, determines one set of consumer coordinates by three pseudorange values, receives several sets of consumer coordinates, reveals the GNSS spacecraft, whose navigation messages should not be used for navigation definitions.

The main technical result achieved by the claimed invention is the prompt detection directly in the NAP of a malfunction of the GNSS spacecraft transmitting an incorrect navigation signal if there are more than three GNSS spacecraft in the radio visibility zone of the NAP. The result is achieved by matching the consumer timeline with the GNSS system timeline. To carry out the comparison of the two time scales, together with the NAP, they place the consumer’s timeline storage equipment and high-precision comparisons of the consumer’s timeline with the GNSS system timeline.

From the sequence of actions necessary for the implementation of the method, it follows that the claimed method can be used to analyze the integrity of the GNSS navigation field by navigation messages transmitted by more than three GNSS spacecraft, and repeatedly reproduced.

Literature

1. GLONASS. The principles of construction and operation. / Ed. A.I. Petrova, V.N. Harisova. - M .: Radio engineering, 2005.

Claims (1)

A method for operatively monitoring the integrity of the navigation field of a global navigation satellite system, in which the consumer’s navigation equipment is used, the navigation messages of spacecraft in the radio visibility zone are received, navigation definitions are made, part of the received navigation messages are used, analysis of the received sets is made, several sets are received coordinates of the consumer, reveal a spacecraft whose navigation messages should not be used для for navigation definitions, characterized in that, together with the consumer navigation equipment, the consumer’s timeline storage equipment and the equipment of high-precision comparisons of the consumer’s timeline with the system timeline of the global navigation satellite system are placed, before the navigation determinations are carried out, the consumer’s timeline is synchronized with the global systemic timeline navigation satellite system, when conducting navigation definitions record the time n The reception of the navigation message of each spacecraft of the global navigation satellite system according to the consumer’s time scale, using which the pseudorange between each spacecraft and the consumer’s equipment is determined, one set of consumer coordinates is determined by three pseudorange values.

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