METHOD FOR POSITIONING TARGET IN BUILDING BASED ON ASSISTANCE OF TWO AIRCRAFT

Abstract

A method for positioning a target in a building based on the assistance of two aircraft includes the following steps: allowing two aircraft with respective direction-finding devices to fly around a building, and sending a signal by a positioning tag carried by an indoor target; measuring projections of directions of the signal source on a horizontal plane respectively by the two aircraft, and indicating a position of the indoor target on the horizontal plane by an intersection of the two projections; and according to a difference between barometric pressures of the indoor target and the aircraft, obtaining an altitude of the target to further obtain position coordinates of the target. The method avoids deploying an indoor positioning base station, and improves the positioning accuracy, stability and anti-interference performance.

Claims

1. A method for positioning a target in a building based on assistance of two aircraft, wherein the two aircraft are respectively denoted as a first aircraft and a second aircraft; the first aircraft is provided with a first global navigation satellite system (GNSS) positioning device, a first direction-finding device and a first barometer; the second aircraft is provided with a second GNSS positioning device and a second direction-finding device; the indoor target carries a positioning tag and a second barometer; and the method comprises the following steps: allowing the first aircraft and the second aircraft to fly around the building, and sending a signal by the positioning tag; obtaining position coordinates A.sub.1=(x.sub.1, y.sub.1, z.sub.1) of the first aircraft in real time by the first GNSS positioning device; obtaining position coordinates A.sub.2=(x.sub.2, y.sub.2, z.sub.2) of the second aircraft in real time by the second GNSS positioning device; receiving, by the first direction-finding device, the signal sent by the positioning tag, and measuring a yaw angle in a direction of the signal source as α.sub.1; according to the position coordinates A.sub.1=(x.sub.1, y.sub.1, z.sub.1) of the first aircraft, obtaining projection of a connecting line between the first aircraft and the indoor target on a horizontal plane to be denoted as a first projection line; receiving, by the second direction-finding device, the signal sent by the positioning tag, and measuring a yaw angle in a direction of the signal source as α.sub.2; according to the position coordinates A.sub.2=(x.sub.2, y.sub.2, z.sub.2) of the second aircraft, obtaining projection of a connecting line between the second aircraft and the indoor target on the horizontal plane to be denoted as a second projection line; assuming that position coordinates of the indoor target are A.sub.d=(x.sub.d, y.sub.d, z.sub.d), calculating an intersection of the first projection line and the second projection line as (x.sub.d, y.sub.d); measuring, by the first barometer, a first barometric pressure at a position of the first aircraft as p.sub.1, and measuring, by the second barometer, a second barometric pressure at a position of the indoor target as p.sub.d; and according to the position coordinates of the first aircraft, a principle that the barometric pressure decreases by 100 P.sub.a for every 9 meters rise, and a difference between the first barometric pressure and the second barometric pressure, obtaining an altitude z.sub.d of the indoor target to further obtain the position coordinates of the indoor target.

2. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 1, wherein the intersection (x.sub.d, y.sub.d) is calculated as follows: letting k.sub.1=tan(α.sub.1), then a point-slope equation of the first projection line is y−y.sub.1=k.sub.1(x−x.sub.1); letting k.sub.2=tan(α.sub.2), then a point-slope equation of the second projection line is y−y.sub.2=k.sub.2 (x−x.sub.2); and thus, coordinates of the intersection of the first projection line and the second projection line are obtained as (x.sub.d,y.sub.d), wherein x.sub.d=(b.sub.2−b.sub.1)/(k.sub.2−k.sub.1), y.sub.d=k.sub.1(x.sub.d−x.sub.1)+b.sub.1=−k.sub.1x.sub.1+y.sub.1, and b.sub.2=−k.sub.2x.sub.2+y.sub.2.

3. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 1, wherein the first aircraft and the second aircraft are unmanned aerial vehicle (UAVs) or manned helicopters.

4. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 1, wherein the positioning tag is connected to the second barometer; the positioning tag has a signal modulation function, and the second barometric pressure measured by the second barometer is modulated in the signal sent by the positioning tag; and each of the first direction-finding device and the second direction-finding device has a corresponding signal demodulation function.

5. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 1, wherein the first direction-finding device and the second direction-finding device measure the yaw angle in the direction of the signal source by using an amplitude comparison method, a Doppler method, a phase interference method, a correlation interference method or a time difference of arrival (TDOA) method.

6. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 1, wherein the first direction-finding device and the second direction-finding device are one-dimensional (1D) direction-finding devices.

7. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 2, wherein the first aircraft and the second aircraft are unmanned aerial vehicle (UAVs) or manned helicopters.

8. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 2, wherein the positioning tag is connected to the second barometer; the positioning tag has a signal modulation function, and the second barometric pressure measured by the second barometer is modulated in the signal sent by the positioning tag; and each of the first direction-finding device and the second direction-finding device has a corresponding signal demodulation function.

9. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 2, wherein the first direction-finding device and the second direction-finding device measure the yaw angle in the direction of the signal source by using an amplitude comparison method, a Doppler method, a phase interference method, a correlation interference method or a time difference of arrival (TDOA) method.

10. The method for positioning the target in the building based on the assistance of the two aircraft according to claim 2, wherein the first direction-finding device and the second direction-finding device are one-dimensional (1D) direction-finding devices.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIGURE is a schematic view of an embodiment of the present invention.

[0013] Reference Numerals: 2. first aircraft; 3. second aircraft; 4. indoor target; and 6. building.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment

[0014] As shown in FIGURE, in the present embodiment, two aircraft are used to assist in positioning an indoor target. The two aircraft are denoted as the first aircraft 2 and the second aircraft 3 respectively. The first aircraft 2 is provided with a first GNSS positioning device configured to measure a position of the first aircraft in real time, a first direction-finding device, and a barometer configured to measure a barometric pressure at the position of the first aircraft in real time. The second aircraft 3 is provided with a second GNSS positioning device configured to measure a position of the second aircraft in real time, and a second direction-finding device. The first direction-finding device and the second direction-finding device may be 1D direction-finding devices or two-dimensional (2D) direction-finding devices. When the 2D direction-finding devices are used, only measured yaw angles are used, and pitch angles are discarded.

[0015] The first aircraft and the second aircraft may be unmanned aerial vehicles (UAVs) or manned helicopters. They are preferably UAVs to position the indoor target, which are more convenient and safer to operate.

[0016] Because the radio signal radiation is directional, the direction of the radio signal radiation source can be determined by the direction-finding device. In the present embodiment, the first aircraft 2 and the second aircraft 3 separately carry one 1D direction-finding device. The 1D direction finding device can measure the yaw angle in the direction of the signal source by using an amplitude comparison method, a Doppler method, a phase interference method, a correlation interference method or a time difference of arrival (TDOA) method. This belongs to the prior art, which can refer to related documents, and will not be repeated here. The 1D direction-finding devices and the antenna systems thereof can refer to “Design of Shortwave Direction Finding Processor Based on Wasson-Watt Principle” (Wang Baorui et al., Chinese Journal of Scientific Instrument, 2010, 31(8): 313-317).

[0017] The indoor target 4 carries a second barometer configured to measure a barometric pressure at a position of the indoor target 4. There are two types of positioning tags: a non-cooperative positioning tag and a cooperative positioning tag. The cooperative positioning tag can only transmit wireless signals that are not encoded, that is, it can transmit radio signals on any single frequency point, similar to a interphone. Therefore, it can only be used to detect the signal direction. When the barometric pressure measured by the second barometer is transmitted, it is necessary to transmit the barometric pressure to a data processing terminal through other prior communication methods. A signal modulation function is added in the cooperative positioning tag on the basis the non-cooperative positioning tag. First, the positioning tag is connected to the second barometer, so that information such as an identification (ID) and the barometric pressure can be modulated and encoded in the signal transmitted by the positioning tag. The first direction-finding device and the second direction-finding device have the corresponding signal demodulation function, and the measured barometric pressure can be directly received by the first direction-finding device and the second direction-finding device. Then, the first direction-finding device and the second direction-finding device transmit relevant data to the data processing terminal, which is more convenient for management. Therefore, in the present embodiment, the cooperative positioning tag is preferably used. Both modulation and demodulation of signals belong to the prior art, which will not be repeated here.

[0018] In the present embodiment, the method for positioning a target in a building based on the assistance of two aircraft includes the following steps:

[0019] The first aircraft 2 and the second aircraft 3 fly around the building 6, and the positioning tag sends a signal. The first GNSS positioning device obtains position coordinates A.sub.1=(x.sub.1, y.sub.1, z.sub.1) of the first aircraft in real time, and sends the position coordinates A.sub.1=(x.sub.1, y.sub.1, z.sub.1) to the data processing terminal. The second GNSS positioning device obtains position coordinates A.sub.2=(x.sub.2, y.sub.2, z.sub.2) of the second aircraft in real time, and sends the position coordinates A.sub.2=(x.sub.2, y.sub.2, z.sub.2) to the data processing terminal.

[0020] The first direction-finding device receives the signal sent by the positioning tag, and the first direction-finding device measures a yaw angle α.sub.1 in a direction of the signal source, and sends the yaw angle α.sub.1 to the data processing terminal. According to the position coordinates A.sub.1=(x.sub.1, y.sub.1, z.sub.1) of the first aircraft, the data processing terminal obtains projection of a connecting line between the first aircraft and the indoor target on a horizontal plane, which is denoted as a first projection line. Similarly, the second direction-finding device receives the signal sent by the positioning tag, and the second direction-finding device measures a yaw angle α.sub.2 in a direction of the signal source, and sends the yaw angle α.sub.2 to the data processing terminal. According to the position coordinates A.sub.2=(x.sub.2, y.sub.2, z.sub.2) of the second aircraft, the data processing terminal obtains projection of a connecting line between the second aircraft and the indoor target on the horizontal plane, which is denoted as a second projection line.

[0021] Assuming that position coordinates of the indoor target are A.sub.d=(x.sub.d, y.sub.d, z.sub.d), an intersection of the first projection line and the second projection line is calculated as (x.sub.d, y.sub.d). In a specific implementation, the intersection (x.sub.d, y.sub.d) is calculated as follows:

[0022] Letting k.sub.1=tan(α.sub.1), then a point-slope equation of the first projection line is y−=k.sub.1(x−x.sub.1). Letting k.sub.2=tan(α.sub.2), then a point-slope equation of the second projection line is y−y.sub.2=k.sub.2(x−x.sub.2).

[0023] Thus, the coordinates of the intersection of the first projection line and the second projection line are obtained as (x.sub.d,y.sub.d), where x.sub.d=(b.sub.2−b.sub.1)/(k.sub.2−k.sub.1), y.sub.d=k.sub.1(x.sub.d−x.sub.1)+y.sub.1, b.sub.1=−k.sub.1x.sub.1+y.sub.1, and b.sub.2=−k.sub.2x.sub.2+y.sub.2.

[0024] The first barometer measures a barometric pressure p.sub.1 at the position of the first aircraft, and sends the barometric pressure p.sub.1 to the data processing terminal. The second barometer measures a barometric pressure p.sub.d at the position of the indoor target, and sends the barometric pressure p.sub.d to the data processing terminal. According to the principle that the barometric pressure decreases by 100 P.sub.a for every 9 meters rise, the difference between the two barometric pressures and the position coordinates of the first aircraft, the data processing terminal obtains an altitude z.sub.d of the indoor target to further obtain the position coordinates (x.sub.d, y.sub.d, z.sub.d) of the indoor target, thereby completing the positioning of the indoor target.

[0025] In the present embodiment, various data measured by the first aircraft, the second aircraft and the positioning tag of the indoor target are transmitted to the data processing terminal (preferably in a wireless transmission mode), and the data processing terminal performs positioning operations.