Positioning method and system based on electromagnetic waves

Abstract

The present invention relates to a positioning method and system based on electromagnetic waves. When the direct line of sight between a terminal and a base station is blocked, a mobile device is used to carry a reflective surface, and a reflection channel of terminal-reflective surface-base station is constructed through the reflective surface. The base station receives positioning signals transmitted by the terminal at N time points, and estimates the channel between the terminal and the base station according to the positioning signals. The channel is composed of N≥1 sub-paths, and the channel sub-paths passing through the terminal-reflective surface-base station at N time points are extracted from the channel. At the N time points, the geographical locations of the reflective surface are different. The base station performs positioning operation processing on the parameters of the channel sub-paths passing through the terminal-reflective surface-base station at the N time points to obtain terminal position parameters, which can be used for underground mine rescue and other occasions.

Description

Technical Field

[0001] The invention relates to a positioning method and system based on electromagnetic waves. Background Art

[0002] There are many reasons for mine accidents, such as water seepage, collapse, explosion, etc., coupled with the complex shaft system and unknown rescue routes, which make it difficult to accurately locate the trapped people and hinder the rescue process. Therefore, it is necessary to accurately locate the position of the trapped people as soon as possible.

[0003] Ultra Wide Band (UWB) positioning technology is one of the main technologies currently used for underground positioning. The UWB positioning tag is a movable target to be positioned. It sends nanosecond pulse signals to the surrounding area. The UWB base stations fixedly installed in the surrounding area receive and measure the above pulse signals. After filtering, sliding correlation and other operations, each calculates the arrival time of the pulse signal and other positioning measurement information. By collecting the positioning measurement information of multiple UWB base stations, the target position information can be obtained according to the triangulation calculation formula.

[0004] Since this type of underground positioning technology is very dependent on the line of sight (LOS) between the positioning terminal and the positioning base station, if the falling rocks and other collapsed objects block the line of sight transmission path between the positioning terminal and the positioning, the above positioning method will fail and the rescuers will not be able to obtain the position of the trapped personnel. Therefore, it is urgent to design a device for locating trapped personnel underground that meets the needs of emergency rescue in mine accidents. Summary of the invention

[0005] The object of the present invention is to provide an electromagnetic wave-based positioning method and an electromagnetic wave-based positioning system for implementing the method, which can realize terminal positioning under certain circumstances where the direct line of sight between the terminal and a base station is blocked.

[0006] The technical solution of the present invention is: when the direct line of sight between the terminal and the base station is blocked, a mobile device is used to carry a reflecting surface, and a reflection channel of the terminal-reflecting surface-base station is constructed through the reflecting surface. The base station receives the positioning signal transmitted by the terminal at N (multiple) moments, and estimates the channel between the terminal and the base station according to the positioning signal. The channel is composed of M≥1 (one or more) sub-paths, and the channel sub-paths passing through the terminal-reflecting surface-base station at N moments are extracted from the channel. At the N moments, the geographical locations of the reflecting surface are different. The base station performs positioning operation processing on the parameters of the channel sub-path passing through the terminal-reflecting surface-base station at the N moments to obtain the terminal position parameters.

[0007] Preferably, the selected sub-path is determined jointly by the arrival direction angle of each sub-path and the channel delay.

[0008] Preferably, the base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at each of the N moments, and selects in the channel that the direction of the incoming wave is within the angle range determined by the spatial angle The channel subpath with the smallest delay is Δ, where Δ is a constant, which is generally determined by the mean square error of the angle estimation and represents the fluctuation of the angle estimation due to the presence of noise.

[0009] Preferably, the base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at each of the N moments, and selects in the channel that the direction of the incoming wave is within the angle range determined by the spatial angle The difference between the angle of each sub-path and the spatial angle θ is determined, denoted as Δθ i , and the difference between the delay of each subpath and the average delay of S subpaths, denoted as Δτ i ,calculate i belongs to the S sub-path, Δ, A and B are constants, and the smallest ρ i The corresponding sub-path is the sub-path selected at the current moment.

[0010] Preferably, the base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at the current moment according to the GPS coordinates of the reflection surface at each of the N moments.

[0011] Preferably, the positioning signal is an electromagnetic wave pilot signal.

[0012] Preferably, the base station is equipped with a multi-antenna array.

[0013] Preferably, the base station performs positioning calculations on the parameters of the channel sub-path passing through the terminal-reflection surface-base station at the N moments in time as follows: calculate the path distance passing through the terminal-reflection surface-base station based on the time delay of the channel sub-path selected by the base station at each of the N moments, calculate the distance from the terminal to the reflection surface based on the path distance passing through the terminal-reflection surface-base station and the distance from the reflection surface to the base station, and determine the position of the terminal based on multiple groups of distances from the terminal to the reflection surface and corresponding multiple groups of reflection surface position data.

[0014] Preferably, the method for calculating the position of the terminal based on multiple sets of distances from the terminal to the reflecting surface and the corresponding multiple sets of reflecting surface position data is a triangulation positioning method or a positioning method based on the SAR principle.

[0015] The electromagnetic wave-based positioning system comprises a base station, a terminal and a reflecting surface, wherein the reflecting surface is mounted on a movable platform and the base station is equipped with multiple antennas. Any electromagnetic wave-based positioning method disclosed in the present invention is adopted to construct a reflection channel of terminal-reflecting surface-base station through the reflecting surface, and the positioning operation of the terminal is performed according to the positioning signal received by the base station to realize the terminal positioning.

[0016] Preferably, when the position of the terminal is calculated by using the triangulation positioning method, a reflecting surface mounted on a movable platform is provided and moved in any direction at any speed, so that the reflecting surface is in different geographical locations at N moments, and there is a path passing through the terminal-reflecting surface-base station at each of the N moments, so as to obtain multiple sets of data suitable for the triangulation positioning method from the reflecting surfaces at different geographical locations.

[0017] Preferably, when the position of the terminal is calculated by using a positioning method based on the SAR principle, a reflecting surface mounted on a movable platform is provided, and the reflecting surface is carried by the movable platform to move in a straight line at a certain speed and direction, and the positioning signal emitted by the terminal is used at different times during the linear movement to obtain multiple sets of data corresponding to different positions of the reflecting surface and suitable for the positioning method based on the SAR principle.

[0018] Preferably, the movable platform is a small unmanned aerial vehicle.

[0019] The beneficial effects of the present invention are as follows: the present invention adopts a movable platform to set the reflecting surface at an appropriate position and posture, and constructs a reflecting channel of terminal-reflecting surface-base station, thereby being able to implement positioning operations on the terminal based on the positioning signal received by the base station, and realizing terminal positioning in corresponding situations where the direct line of sight is blocked, and can be used for underground mine rescue and other occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the equipment layout and positioning principle of the triangulation positioning method involved in the present invention;

[0021] Figure 2 It is a schematic diagram of the positioning principle of the positioning method using the SAR principle involved in the present invention;

[0022] Figure 3 It is a schematic diagram of the positioning principle of the positioning method involved in the present invention;

[0023] Figure 4 yes Figure 3 Schematic diagram of the channel multipath involved in the example. DETAILED DESCRIPTION

[0024] See also Figure 3 and Figure 4In this electromagnetic wave-based positioning method, when the line-of-sight path (LOS path) between the terminal and the base station is blocked, a reflecting surface (including a transmitting element or a reflector, etc.) is carried or set by a mobile device (or a movable platform, such as a small drone) or other means, and a reflecting channel (path) of terminal (for example, a terminal device used by rescue personnel for positioning / calling for help)-reflecting surface-base station is constructed through the reflecting surface. That is, the reflecting surface is moved to or set at an appropriate position (when necessary, the posture / orientation of the reflecting surface is appropriately set / adjusted), so that the positioning signal from the terminal can reach the reflecting surface through the line-of-sight path and be reflected by the reflecting surface, and the positioning signal reflected by the reflecting surface can reach the base station through the line-of-sight path and be received by the base station, and the positioning operation of the terminal is performed according to the positioning signal received by the base station to realize the positioning of the terminal.

[0025] In the case where the line-of-sight channel between the base station and the target is blocked by falling rocks, water seepage, etc., the present invention uses a small movable device (e.g., a drone) to carry the reflective surface, pass through the gap between the falling rocks, and reach a suitable location (e.g., the area where people are trapped). By adjusting the orientation and height of the drone platform / reflective surface, a reflective channel / path between the rescued person-reflective surface-base station is constructed. At any time t, the path is and Composition, of which is the path (or distance) from the terminal to the reflecting surface at time t, is the path (or distance) from the reflection surface to the base station at time t.

[0026] The base station receives the positioning pilot signal sent by the terminal through the above path, and estimates the distance l based on the pilot signal. t Includes: distance from terminal to reflective surface and the distance from the reflecting surface to the base station Right now: In addition, there may be distance deviations / errors such as distance Δl caused by timing deviations. These distance deviations / errors also exist in the prior art and can be processed according to existing processing methods. They are usually not considered in the application scenarios of the present invention.

[0027] The position of the drone relative to the base station can be obtained according to the prior art, and in the present invention it can be assumed to be accurately known, that is, the distance from the reflecting surface to the base station is a known quantity. Therefore, l t The only unknown quantity in

[0028] Two positioning methods can be used to realize the positioning of the drone to the terminal, determine the position of the terminal relative to the drone, and determine the position of the terminal relative to the drone based on the terminal position and the drone position. One method is the traditional positioning technology (also known as the triangulation positioning method): the drones are placed at large intervals between each other, forming a deployment method similar to that of distributed base stations, and the terminal position is determined using the traditional triangulation positioning method. Another method is the traditional angle measurement technology (also known as the positioning method based on the SAR principle), where the drones fly in a straight line at a fixed speed (rate) and direction, and the reflective surface continuously (periodically, or continuously) reflects the signal to the base station. The base station receives multiple frames of continuous reflected signals and can use the SAR principle to determine the angle of the target, thereby locating the target.

[0029] See also Figure 1 The traditional triangulation positioning method requires that the channel between the signal transmitter and the receiver is a line of sight. For the same signal transmitter (for example, the terminal used by the rescued person involved in the present invention, collectively referred to as UWB tag or tag in the following description of the triangulation positioning method using UWB positioning technology as an example), there are multiple signal receiving ends located in different positions (for example, the drone platform / reflection surface involved in the present invention, collectively referred to as UWB base station or base station in the following description of the triangulation positioning method using UWB positioning technology as an example) that receive the signal sent by the transmitter as the basic data for locating the transmitter.

[0030] UWB positioning technology requires that the clocks between UWB base stations be synchronized. In practice, the synchronization accuracy of UWB base stations can be very precise, within 0.1ns. Therefore, it is assumed that the clocks between UWB base stations are synchronized. After the UWB tag sends a pulse signal, the time required to reach each base station is different. Figure 1 As shown, they are t1-t4 respectively.

[0031] Taking base station 1 as the benchmark, the distance difference between the tag and other base stations i and the distance between the tag and base station 1 can be obtained as follows:

[0032] r i,1 =c×(t i -t1)

[0033] Where c is the speed of light.

[0034] Taking plane coordinates as an example (similar to the three-dimensional coordinate system), assuming that the coordinates of base station i are (x i ,y i ), 1≤i≤M, where the location coordinates of base station 1 are (x1, y1), the coordinates of the tag are (x, y), and the distance from the tag to the base station is:

[0035]

[0036] Then the distance difference between the tag and base station i and the tag and base station 1 is:

[0037] r i，1 =ri -r1

[0038] Then there is

[0039] (r i，1 +r1) 2 =(xx i ) 2 +(yy i ) 2

[0040] Simplified:

[0041]

[0042] in,

[0043]

[0044] X i,1 =x i -x1,y i，1 =y i -y1

[0045] make:

[0046]

[0047]

[0048]

[0049] but

[0050] h=Gz

[0051] Under the existing technology, there are many methods to calculate the parameter z. For example, according to the least squares algorithm fitting, the parameter z can be obtained as:

[0052]

[0053] Therefore, the coordinates of the tag can be calculated based on the position (coordinates) of the relevant base station to achieve the positioning of the tag.

[0054] See also Figure 2The positioning method based on the SAR principle requires that the channel between the signal transmitting end and the receiving end is a line of sight. For a signal transmitting end (for example, the terminal used by the person to be rescued in the present invention), a signal receiving end (for example, the drone platform / reflecting surface in the present invention, and in the following description of the positioning method based on the SAR principle using SAR as an example, collectively referred to as a base station or SAR / synthetic aperture radar) is used to move in a straight line at a certain speed and direction, and continuously (for example, periodically collect) obtain the signal of the signal transmitting end (for example, the terminal used by the person to be rescued in the present invention, and in the following description of the positioning method based on the SAR principle, collectively referred to as a terminal), and obtain multiple frames of signals corresponding to different moving positions, which are used as basic data for positioning the transmitting end.

[0055] Synthetic Aperture Radar (SAR) is an imaging radar that uses two-dimensional matched filtering to obtain high-resolution images. Based on the working principle of SAR, this article introduces its application in positioning scenarios. Figure 2 The working mode of SAR is given. The base station is placed on a movable platform. For example, the platform (base station) moves to the right at a speed v and can receive signals sent by the terminal at different times.

[0056] Taking the plane coordinate system as an example, assume that the perpendicular distance from the terminal to the base station in the running direction (straight line path) is R0, the foot coordinates of the perpendicular are (x0, y), and the moving speed of the platform (base station) is parallel to the x-axis. Then at time t, the distance from the terminal to the base station can be expressed as

[0057]

[0058] In general, R0>>vt-x0, so the above formula can be approximated as

[0059]

[0060] If the foot of the perpendicular is regarded as the origin of the plane coordinate system, then x0 = 0, and the above formula can be further simplified to:

[0061]

[0062] The distance that changes with time will be more obvious in the phase of the echo signal. By extracting the echo signals at N moments and extracting the phase information at the N moments, the vertical distance R0 from the terminal to the base station can be estimated. The detailed steps of the synthetic aperture positioning method are mature technologies and will not be described in detail here.

[0063] Therefore, referring to the triangulation positioning method or the SAR positioning method, the base station in the triangulation positioning is replaced by the movable reflecting surface in the present invention, or the base station in the SAR positioning is replaced by the movable reflecting surface in the present invention, and the relative position of the movable reflecting surface relative to the base station in the present invention can be obtained by other means, so the positioning of the tag is achieved according to the relevant channel parameters extracted from the base station in the received signal of multiple frames (N moments).

[0064] Considering that in actual scenarios, there are a large number of reflection paths between the terminal and the reflecting surface and between the reflecting surface and the base station (see Figure 3 and Figure 4 ), interferes with or affects the accuracy and performance of positioning. The present invention implements channel (path) selection in the following manner:

[0065] 1) Channel selection between the base station and the reflecting surface: Since the relative position between the base station and the reflecting surface is known and the base station can be equipped with multiple antennas, the beam selection method can be used to select the one whose angle of arrival (AoA) best matches the spatial position of the reflecting surface from among the numerous reflection paths;

[0066] 2) Channel selection between the reflecting surface and the terminal: Since the reflecting surface is installed on a movable platform and has to pass through a narrow gap, neither the movable platform nor the reflecting surface can be too large, and it cannot be assumed that the reflecting surface has the function of multiple antennas. In this case, the path with the shortest propagation time can be selected among the multiple paths based on the shortest path principle (the direct line of sight path is the shortest).

[0067] The specific implementation scheme based on the above path selection includes that the movable platform is equipped with GPS, and the GPS position coordinates of the movable reflective surface are fed back to the base station. Taking the two-dimensional plane coordinate system as an example, assuming that the position coordinates of the movable platform at N moments are (x1, y1), (x2, y2), ..., (x N ,y N ), the base station is equipped with a linear array consisting of M antennas, whose position coordinates are (x ′ 1,y′1)、(x ′ 2, y′2), …, (x ′ M , y′ M ). At each of the N moments, the base station device can calculate the angle information of the movable reflective surface in the coordinate system determined by the base station array antenna based on the position coordinates of the base station array antenna and the position coordinates of the movable device at that moment. One calculation method includes: according to the GPS coordinates (x′1, y′1) of the antenna positions at both ends of the base station array antenna and (x′ M , y′ M ), calculate the slope of the base station antenna array, that is, According to the position coordinates (x n ,y n ), calculate the slope of the coordinates of the mobile device to the center point of the base station: Then the angle θ of the movable reflector in the coordinate system determined by the base station array antenna satisfies

[0068] The base station receives the signal transmitted by the terminal at each of the N moments, and estimates the channel between the terminal and the base station based on the received signal. Assume that the channel estimated at the nth moment contains I subpaths, and the direction of the wave of each subpath relative to the base station array is θ1, θ2, ..., θ I , the delay of each subpath is τ1, τ2, …, τ I . Find the path that satisfies The channel subpaths are S, where △ is a constant and is determined by the mean square error of the angle estimation. Due to the influence of noise and interference, there is a certain error in the angle estimation, so an angle range is defined, and the channel subpaths whose angle estimation falls within the angle range are considered to have reached the base station after being reflected by the reflection surface.

[0069] According to the channel (path) selection principle, the method includes:

[0070] 1) Select τ among the S sub-paths i The smallest sub-path is used as the reflection path from terminal to reflection surface to base station;

[0071] 2) In the S sub-paths, calculate △θ i =θ i -θ, as well as The subpath with the smallest ρi is selected as the reflection path of the terminal-reflection surface-base station, where A and B are constants or configurable parameters, representing the weights in the spatial angle domain or the delay domain, respectively.

[0072] Based on the above path selection, the reflection paths of the terminal-reflection surface-base station at N moments can be obtained, and the time delays of the reflection paths at the N moments are respectively The reflection path length of the terminal-reflection surface-base station can be calculated based on the time delay at N moments, that is, the path length at each moment is the sum of the path length from the terminal to the reflection surface and the path length from the reflection surface to the base station. If the location information of the reflection surface or the movable device equipment is known, the path length from the reflection surface to the base station can be regarded as a known quantity, so the path length from the terminal to the reflection surface can be easily calculated. Combined with the triangulation positioning method or the SAR angle measurement method, the position of the trapped person can be located.

[0073] The system for implementing the above method may include: a base station device (or base station), a terminal device (e.g., a UBW tag), a movable platform (e.g., a drone, especially a small drone), and a reflective surface. The base station device is equipped with multiple receiving antennas, the reflective surface is mounted on the movable platform, and the movable platform is controlled to move to different positions. The base station device receives the signal transmitted by the terminal device, and estimates and selects the transmission path between the base station and the terminal according to the received signal, wherein the principle of transmission path selection is: the shortest path with the smallest azimuth interval from the movable platform.

[0074] The mobile platform can be moved to N different positions. The base station receives the signals transmitted by the reflective surfaces at N different positions, calculates the signal transmission distance according to the selected path, and calculates the position of the terminal according to the differential and triangulation positioning methods.

[0075] The mobile platform can be moved to N different positions. The base station receives the signals transmitted by the reflecting surfaces at N different positions, calculates the signal transmission distance and phase according to the selected path, and calculates the location of the terminal according to the SAR imaging principle.

[0076] Generally, the distance between the N different positions can be controlled to be of the same order of magnitude as the distance between the reflecting surface and the terminal. If necessary, the distance between the N different positions can also be controlled to be much smaller than the distance between the reflecting surface and the terminal.

[0077] The angle of the mobile platform in the airspace observed by the base station antenna can be determined based on the positional relationship between the base station and the mobile platform.

[0078] The base station can eliminate channel multipaths in other angular spaces through an iterative elimination method.

[0079] Unless otherwise specified or when one preferred or optional technical means is a further limitation of another technical means, the preferred and optional technical means disclosed in the present invention can be arbitrarily combined to form several different specific implementation methods.

Claims

1. A positioning method based on electromagnetic waves, characterized in that: In the case where the direct line of sight between the terminal and the base station is blocked, a mobile device is used to carry a reflecting surface, and a reflection channel of the terminal-reflecting surface-base station is constructed through the reflecting surface. The base station receives the positioning signal transmitted by the terminal at N times, and estimates the channel between the terminal and the base station according to the positioning signal. The channel is composed of M≥1 sub-paths, and the channel sub-paths passing through the terminal-reflecting surface-base station at N times are extracted from the channel. At the N times, the geographical locations of the reflecting surface are different. The base station performs positioning operation processing on the parameters of the channel sub-paths passing through the terminal-reflecting surface-base station at the N times to obtain the terminal position parameters.

2. The positioning method according to claim 1, characterized in that: The selected subpath is determined by the arrival direction angle of each subpath and the channel delay.

3. The positioning method according to claim 2, characterized in that: The base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at each of N moments, and selects in the channel that the direction of the incoming wave is within the angle range determined by the spatial angle. The channel sub-path with the smallest delay within the range of , where Δ is a constant and represents the angle fluctuation range.

4. The positioning method according to claim 2, characterized in that: The base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at each of N moments, and selects in the channel that the direction of the incoming wave is within the angle range determined by the spatial angle. The difference between the angle of each sub-path and the spatial angle θ is determined and recorded as Δθ i , and the difference between the delay of each subpath and the average delay of S subpaths, denoted as Δτ i ,calculate i belongs to the S-bar diameter, Δ, A and B are constants, and the smallest ρ i The corresponding sub-path is the sub-path selected at the current moment.

5. The positioning method according to any one of claims 1 to 4, characterized in that: The base station determines the spatial angle θ of the reflection surface relative to the base station antenna array at the current moment according to the GPS coordinates of the reflection surface at each of the N moments.

6. The positioning method according to claim 1, characterized in that: The base station performs positioning calculations on the parameters of the channel sub-path passing through the terminal-reflection surface-base station at the N moments in time as follows: calculate the path distance passing through the terminal-reflection surface-base station based on the time delay of the channel sub-path selected by the base station at each of the N moments, calculate the distance from the terminal to the reflection surface based on the path distance passing through the terminal-reflection surface-base station and the distance from the reflection surface to the base station, and determine the position of the terminal based on multiple groups of distances from the terminal to the reflection surface and corresponding multiple groups of reflection surface position data.

7. The positioning method according to claim 6, characterized in that: The method for calculating the position of the terminal based on multiple sets of distances from the terminal to the reflecting surface and the corresponding multiple sets of reflecting surface position data is a triangulation positioning method or a positioning method based on the SAR principle.

8. A positioning system based on electromagnetic waves, characterized in that: The invention comprises a base station, a terminal and a reflecting surface, wherein the reflecting surface is mounted on a movable platform, the base station is equipped with multiple antennas, and the electromagnetic wave-based positioning method described in any one of claims 1 to 7 is adopted, a reflection channel of terminal-reflecting surface-base station is constructed through the reflecting surface, and positioning operation of the terminal is performed according to the positioning signal received by the base station to realize terminal positioning.

9. The positioning system according to claim 8, characterized in that: When the triangulation method is used to calculate the terminal's position, a reflecting surface mounted on a movable platform is set up to move at an arbitrary speed and in an arbitrary direction, and is at different geographical locations at N moments, and there is a path passing through the terminal-reflecting surface-base station at each of the N moments, so as to obtain multiple sets of data suitable for the triangulation method from the reflecting surfaces at different geographical locations.

10. The positioning system according to claim 8, characterized in that When the position of the terminal is calculated by using a positioning method based on the SAR principle, a reflective surface is set on a movable platform. The movable platform carries the reflective surface and moves in a straight line at a certain speed and direction. At different times in the linear movement, the positioning signal emitted by the terminal is used respectively to obtain multiple sets of data corresponding to different positions of the reflective surface and suitable for the positioning method based on the SAR principle.

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