A base station calibration method based on a fusion of TOF and AOA methods

Abstract

The present application belongs to the field of base station calibration, and is a base station calibration method based on fusion of TOF and AOA method. A base station is selected as an original base station to establish a coordinate system. With the original base station as the origin, a first adjacent base station A is found in a counterclockwise or clockwise direction, the distance r between the original base station and the base station A is measured n , the spatial coordinates of the base station A are calculated, and the azimuth of the base station A to be determined is distinguished by azimuth. The distance r between the original base station and a base station B adjacent to the base station A is measured n , the azimuth and the pitch angle are calculated, the base station A and the base station B are projected onto the xoy plane of the original base station, a spherical equation is established, two sets of spatial coordinate solutions of the base station B are obtained by solving the spherical equation, and the azimuth of the base station B is used to determine the final solution. The calibration method improves the x and y coordinate accuracy of the base station. Through distance measurement of three base stations, mutual constraint is achieved, and the calibration accuracy is improved.

Description

Technical Field

[0001] This invention belongs to the field of base station calibration, specifically a base station calibration method based on the fusion of TOF and AOA methods. Background Technology

[0002] Currently, Ultra Wide Band (UWB) technology is a wireless carrier communication technology that uses nanosecond-level non-sinusoidal narrow pulses to transmit data, thus offering a wide spectral range. This technology boasts several advantages, such as low system complexity, insensitivity to channel attenuation, low transmitted signal power spectral density, and low interception capability. UWB technology is commonly used in positioning applications, achieving high positioning accuracy down to the centimeter level. UWB technology has a wide range of applications, including robot positioning, indoor navigation, and landslide detection.

[0003] my country has a complex and diverse topography, with a vast mountainous area accounting for 33% of the total area. In years with abundant rainfall, natural disasters such as landslides and mudslides occur frequently. Therefore, monitoring soil movement is crucial. Typically, UWB positioning technology is used to monitor soil at multiple points on mountainsides, acquiring spatial state data of the soil. By comprehensively analyzing sudden real-time state data, the likelihood of landslides can be predicted to some extent, allowing for advance planning and preventing loss of life and property.

[0004] After deploying positioning base stations, determining their coordinates is a challenging task. If the base stations are all located on flat ground, measuring their coordinates is relatively easy. However, if they are located on a hillside, determining their coordinates becomes much more difficult, mainly due to the long distances between base stations and the complex surrounding environment.

[0005] Currently, common UWB positioning system architecture diagrams are as follows: Figure 1 As shown, the system contains four or more base stations and at least one tag. The system can set any base station as the origin of the spatial coordinate system and any direction as the direction of the coordinate axis; however, for ease of calculation, base station 0 is usually used as the origin. Determining the coordinate axes requires selecting another base station. Automatic base station calibration requires selecting at least three base stations and arranging them according to a rule; determining the coordinates of existing base stations is more difficult. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a base station calibration method based on the fusion of TOF and AOA methods, thereby solving the problem of difficult base station coordinate positioning.

[0007] This invention is implemented as follows:

[0008] A base station calibration method based on a fusion of Time-of-Flight (TOF) and AoA methods, the method comprising:

[0009] A base station is selected as the origin base station, which is a base station with an antenna array, and is used to measure the angle of arrival (AOA) of UWB signals transmitted from other base stations, including the azimuth angle (θ). n and pitch angle It is equipped with a geomagnetic sensor to distinguish the north and south poles and use this direction as a reference for establishing a coordinate system. The direction pointing to the north pole is taken as the positive direction of the y-axis. The origin base station takes itself as the origin of the spatial coordinate system. The electronic gyroscope built into the origin base station identifies the vertical direction and takes its upward direction as the positive direction of the z-axis. The positive direction of the x-axis is determined by the right-hand rule.

[0010] Using the origin base station as the origin, find the first nearest base station A in a counterclockwise or clockwise direction, and measure the distance r between the origin base station and base station A. n The spatial coordinates of base station A are calculated using the following formula, with the azimuth angle used to determine the orientation of base station A. The formula is:

[0011] x n =r n sinθ n

[0012] y n =-r n cosθ n

[0013]

[0014] Where, θ n It is the azimuth angle. Let x be the pitch angle, (x) n y n , z n () represents the coordinates of the base station;

[0015] Measure the distance r between the origin base station and a nearby base station B. n As well as the azimuth and elevation angles, project base stations A and B onto the xoy plane of the origin base station and establish the spherical equation:

[0016]

[0017] d 02 The distance between the origin base station and base station B can be determined by... Directly obtained, d 12 First, calculate the height difference Δl between base station A and base station B. 12 and spatial distance l 12Then, by using the Pythagorean theorem, we can calculate the coordinates of the origin base station, base station A, and base station B, respectively. We obtain two sets of spatial coordinate solutions for base station B by solving the spherical equation, and use the azimuth angle of base station B to determine the final solution.

[0018] Furthermore, the distance r between the origin base station and the base station is measured. n The method used is the Time-of-Flight (TOF) method, which calculates the distance between two base stations by measuring the "time of flight" between the transmitter and reflector of a signal such as ultrasound, microwave, or light at the origin base station and other base stations.

[0019] Furthermore, using azimuth angles to determine the final solution includes: constructing a vector from the origin base station A0 and the base station to be calibrated as follows: Let unit vector The final solution is expressed as:

[0020]

[0021] Furthermore, atmospheric pressure sensors are used for positioning to calculate the current altitude h of each base station relative to sea level. n Using the height h0 of the origin base station as a reference, the current heights of the base station to be calibrated and the origin base station are compared to calculate the z' coordinate of the base station to be calibrated. The z' coordinate obtained by the atmospheric pressure sensor positioning is combined with the z coordinate obtained by the fusion of TOF and AOA methods, and the final result of the z-direction coordinate of the base station to be calibrated is obtained by weighted averaging.

[0022] Furthermore, the weighted average method is expressed by the following formula:

[0023] z final =γz+ωz`

[0024] γ+ω=1

[0025] Among them, the parameters γ and ω must be adjusted according to the local air pressure.

[0026] Furthermore, the relationship between altitude and pressure is used to calculate the current altitude h of each base station relative to sea level. n The relationship between the height and the pressure is as follows:

[0027]

[0028] in,

[0029] γ: Poisson's ratio during adiabatic processes;

[0030] P: Pressure measured by an atmospheric pressure sensor;

[0031] h: Current altitude;

[0032] P b : is the pressure at sea level where h = 0;

[0033] T b : The temperature at sea level where h = 0;

[0034] μ: Molar mass of air

[0035] R: Universal gas constant

[0036] g: acceleration due to gravity.

[0037] Compared with the prior art, the beneficial effects of this invention are as follows:

[0038] This invention's AOA and TOF methods improve the efficiency of positioning system deployment by automatically calibrating base station coordinates. The calibration method improves the accuracy of the base station's x and y coordinates. Furthermore, by measuring the distances between three base stations and establishing mutual constraints, the calibration accuracy is further enhanced. Attached Figure Description

[0039] Figure 1 Schematic diagram of common UWB positioning systems;

[0040] Figure 2 Schematic diagram of two-point planar positioning;

[0041] Figure 3 Three-point planar positioning diagram;

[0042] Figure 4 Schematic diagram of the TOF and AOA fusion positioning method of this invention;

[0043] Figure 5 The present invention integrates TOF and AOA positioning, with the base station B projected onto the xoy plane;

[0044] Figure 6 This is a schematic diagram illustrating the principle of the TOF method provided in an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] See Figure 1 As shown, this invention selects a third base station 3, then connects the zeroth base station 0 and the third base station 3, and uses the direction pointing towards the third base station 3 as the positive y-axis; uses the direction perpendicular to the y-axis and in the vertical plane, pointing upwards, as the z-axis; and uses the direction perpendicular to the yz plane and pointing towards base station 1 as the x-axis, thus forming a spatial coordinate system XYZO, as shown. Figure 1As shown. Theoretically, knowing the x and y coordinates of two base stations allows us to determine the position of tag T in the XOY plane. However, solving the equations reveals two sets of solutions, as shown below. Figure 2 As shown. To further determine the position of tag T in the XOY plane, an additional base station is needed for positioning, such as... Figure 3 As shown. The UWB positioning system knows the coordinates of the first base station 1, the second base station 2, and the third base station 3, as well as the distances between them, dis1, dis2, and dis3. Now, assume that the three base stations and the tag T are located in the XOY plane, i.e., z1 = z2 = z3 = z = 0. The coordinates of the tag T are calculated using the following formula.

[0047]

[0048] Similarly, the spatial coordinates of tag T can be determined using four base stations.

[0049] Based on the above analysis, accurate positioning requires the system to accurately measure the distance between the tag and the base station, and the established spatial coordinate system to accurately reflect the location of the base station and its relative positional relationship. Base station calibration in a UWB positioning system has a significant impact on the system's positioning accuracy. Generally, it requires manually measuring the relative position of the base stations and then setting appropriate coordinates for input into the positioning system. However, such measurement operations are labor-intensive and require specialized measuring tools. Some researchers have used the ranging function of the UWB positioning system for base station calibration, but the base stations need to be arranged according to certain rules, making the implementation quite cumbersome. To improve the deployment efficiency of the positioning system...

[0050] The method for automatic base station calibration provided by this invention integrates AOA and TOF methods to automatically calibrate the base station coordinates, thereby improving the efficiency of deploying the positioning system.

[0051] The steps include the following:

[0052] First, establish the spatial coordinate system. The origin, base station A0, is a base station with an antenna array, capable of measuring the angle of arrival (AOA) of UWB signals transmitted from other base stations, which is the azimuth angle θ. n and pitch angle The origin base station A0 is equipped with a geomagnetic sensor to distinguish the north and south poles, using this direction as a reference for establishing the coordinate system, with the direction pointing north as the positive y-axis. Origin base station A0 itself serves as the origin of the spatial coordinate system. The built-in electronic gyroscope in origin base station A0 identifies the vertical direction and uses its upward direction as the positive z-axis. Finally, the positive x-axis direction is determined using the right-hand rule.

[0053] This invention uses the Time-of-Flight (TOF) method to calculate the distance between two base stations by measuring the "time of flight" between the transmitter and reflector of a signal such as ultrasound, microwave, or light at the origin base station and another base station. See also... Figure 6 As shown,

[0054] Device A initiates a distance measurement request, and device B responds and listens for the radio message initiated by device A. A sends a radio message to B and records its transmission timestamp t1. After receiving the message, B records it at a specific time delay t1. replyB Then a reply is sent to A. After A receives the reply and records a timestamp t2, a specific delay t is then passed. replyA A radio message is sent to B, and the transmission timestamp t3 is recorded. Finally, B receives the message and records the timestamp t4. Since the round-trip time is known, we can obtain:

[0055] t roundA =t replyB +2*TOF=t2-t1

[0056] t roundB =t replyA +2*TOF=t4-t0

[0057] The flight time of the signal is:

[0058]

[0059] Assuming the speed of wireless signal propagation in the air is c, then the distance between the two devices is:

[0060] l = c * TOF

[0061] Using the Time-of-Flight (TOF) method, the distance r between the origin base station A0 and one of the base stations is measured. n The spatial coordinates of an unknown base station can be determined using the following formula, assuming the coordinates of the unknown base station are (x... n y n , z n ).

[0062]

[0063] The above method can determine the location of any one of the base stations. The system selects counter-clockwise or counter-clockwise rotation, using azimuth angles to distinguish the location of the base station to be determined. However, using this method alone to determine the coordinates of unknown base stations results in low accuracy because there are no mutual constraints between the base stations. For example, in... Figure 4 In this invention, formula (2) is used to first determine the spatial coordinates of the first nearby base station A, with the origin base station as the origin and in the counterclockwise direction, as (x1, y1, z1).

[0064] The following section uses a fusion of Time-of-Flight (TOF) and AoA methods to locate the second base station B encountered in the counter-clockwise direction. The distance r2 between the origin base station A0 and base station B is obtained using the TOF method, and the azimuth angle θ2 and elevation angle are obtained using the AoA method. Using azimuth θ2 and elevation angle Project base stations A and B onto the plane where the origin base station A0 is located, such as... Figure 5 As shown. Establish the equation of the sphere:

[0065]

[0066] d 02 It can be done Directly obtained, d 12 Then we need to first calculate the height difference Δl between base station 1 and base station 2. 12 and spatial distance l 12 Then, Δl is calculated using the Pythagorean theorem. 12 Using the AOA method, it is not difficult to calculate, including finding the z-coordinates z2 and z1 of base station B and base station A, that the height difference between base station B and base station A is Δl. 21 =z2-z1,l 12 This can be obtained using the TOF method.

[0067] From equation (3), two sets of solutions for the coordinates of base station B can be obtained. Furthermore, the azimuth angle θ2 is used to determine the final solution. The vector formed by the origin base station A0 and base station A is... Let unit vector Therefore:

[0068]

[0069] For the next nearby base station C, the same method is used. Based on the obtained spatial coordinates of base station B, the spatial coordinates can be obtained using the above method.

[0070] To further improve positioning accuracy, atmospheric pressure sensors can be used to assist positioning. The current h of each base station (including the origin base station A0) can be calculated using formula (5). n (Relative to sea level), using the h0 of the origin base station as a reference. By comparing the current heights of the base station to be determined and the origin base station, the z' coordinate of the base station to be determined can be calculated. Assuming the gas is an adiabatic system and the atmospheric temperature decreases with altitude, the formula for altitude versus pressure is as follows:

[0071]

[0072] in,

[0073] γ: Poisson's ratio during adiabatic processes

[0074] P: Pressure measured by an atmospheric pressure sensor

[0075] h: Current altitude

[0076] P b : The pressure at h = 0 (sea level)

[0077] T b : The temperature at h = 0 (sea level)

[0078] μ: Molar mass of air

[0079] R: Universal gas constant

[0080] g: acceleration due to gravity;

[0081] The final result of the z-direction coordinate of the unknown base station is obtained by weighted averaging the z-coordinate obtained by combining the z-coordinate obtained by the TOF and AOA fusion method and the z' coordinate obtained by the atmospheric pressure sensor:

[0082] z final =γz+ωz` (6)

[0083] γ+ω=1 (7)

[0084] Among them, the parameters γ and ω must be adjusted according to the local air pressure.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A base station calibration method based on a fusion of TOF and AOA methods, characterized in that, The method comprises: Selecting one base station as an origin base station, the origin base station is a base station with an antenna array, for measuring the angle of arrival AOA of UWB signals from other base stations, including azimuth angle And pitch angle ; and with a geomagnetic sensor for distinguishing the north and south polar directions, and taking the direction as the reference for establishing the coordinate system, pointing to the north polar direction as the positive direction of the y axis, the origin base station taking itself as the origin of the spatial coordinate system, the electronic gyroscope built-in the origin base station identifying the vertical direction, and taking the upward direction as the positive direction of the z axis, determining the positive direction of the x axis through the right-hand rule; Take the original base station as the original point and find the first adjacent base station A in the clockwise direction, measure the distance between the original base station and base station A And calculate the spatial coordinates of base station A by the following formula, distinguish the direction of base station A to be determined by the azimuth angle, the formula is: ， ， ， wherein is an azimuth angle, is an elevation angle, , , is a coordinate of the base station A; measuring the distance between the origin base station and base station B , base station B is the second base station found in the clockwise direction with the origin base station as the origin, and the azimuth angle and the elevation angle , projecting base station A and base station B onto the xoy plane of the origin base station to establish a spherical equation: ， ， is the distance between the origin base station and base station B in the xoy plane of the origin base station, which is obtained by directly, is the distance between base station A and base station B projected onto the xoy plane of the origin base station, which is obtained by the height difference between base station A and base station B and the spatial distance is calculated by using the Pythagorean theorem, respectively, are the coordinates of the origin base station, base station A and base station B, two sets of spatial coordinates of base station B are obtained by solving the spherical equation, and the final solution is determined by using the azimuth of base station B. Atmospheric pressure sensors are used for positioning to calculate the current altitude of each base station relative to sea level. The height of the origin base station Using this as a benchmark, the current altitude of the base station to be determined is calculated by comparing it with the current altitude of the origin base station. Coordinates obtained from locating the atmospheric pressure sensor Coordinates obtained by combining TOF and AOA methods The coordinates of the base station to be calibrated are obtained by weighted averaging. The final result of the direction coordinates.

2. The base station calibration method based on the fusion TOF and AOA method according to claim 1, characterized in that, The distance between the origin base station and the base station is measured by using a TOF method, which calculates the distance between the two by measuring the "time of flight" of a signal such as an ultrasonic wave, microwave or light between the transmitter and the reflector between the origin base station and the other base station.

3. The base station calibration method based on the fusion of TOF and AOA method according to claim 1, characterized in that, Using the azimuth angle to determine the final solution comprises: taking the origin base station and the base station to be calibrated to form a vector , assuming a unit vector = (0, -1), the final solution is expressed as: 。 4. The base station calibration method based on the fusion of TOF and AOA method according to claim 1, characterized in that, The weighted average method uses the following formula: ， Where: Parameters and Must be adjusted according to local barometric pressure.

5. The base station calibration method based on the fusion of TOF and AOA methods according to claim 1, characterized in that, calculating the current height of each base station relative to sea level using the relationship between height and pressure , the relationship between height and pressure being: ， wherein, : Poisson's ratio during adiabatic process; : pressure measured by the atmospheric pressure sensor; : current height; : P0 is the pressure at sea level for h = 0; : T is the temperature at sea level for h = 0; : molar mass of air : universal gas constant : gravitational acceleration.

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