High-precision indoor four-circle positioning method and system based on bluetooth channel sounding ranging

Abstract

The application belongs to the technical field of indoor positioning, and relates to a high-precision indoor four-circle positioning method and system based on Bluetooth channel detection ranging. The method comprises the following steps: arranging BLE base stations supporting Bluetooth protocol in an indoor area to be positioned; a BLE terminal to be positioned and all arranged BLE base stations respectively perform Bluetooth channel detection, and distance data of the terminal to be positioned to each BLE base station is calculated; a corresponding number of circle distance equations are established, positioning is solved according to the base station layout type in different scenes; and a target positioning result is output. The application can effectively reduce the influence of ranging error on the positioning result, solve the problem of insufficient positioning accuracy in the edge area, effectively reduce the influence of ranging error on the positioning result, identify the BLE base station with excessively large ranging error through residual error analysis, avoid the abnormal error of a single base station from leading to invalidation of the overall positioning result, and increase the system redundancy.

Description

Technical Field

[0001] This invention belongs to the field of indoor positioning technology, specifically relating to a high-precision indoor four-circle positioning method and system based on Bluetooth channel detection and ranging. Background Technology

[0002] With the rapid development of IoT technology and the continuous improvement of indoor space utilization efficiency, the demand for indoor positioning is experiencing explosive growth. In the industrial sector, there is a need for real-time and accurate positioning of production equipment, materials, and personnel to achieve intelligent management and safety monitoring of the production process; in the commercial sector, shopping malls and supermarkets need to use indoor positioning to provide navigation and shopping guidance services for customers, enhancing the consumer experience; and in the office sector, office buildings need to manage personnel and assets through positioning to improve office efficiency.

[0003] Currently, commonly used indoor positioning technologies include ultra-wideband (UWB) positioning, Bluetooth positioning, WiFi positioning, and RFID positioning. UWB positioning, by sending and receiving extremely narrow pulse signals, can achieve centimeter-level positioning accuracy, but suffers from high hardware costs, limited anti-interference capabilities, and high power consumption, hindering large-scale application. Traditional Bluetooth positioning often uses signal strength indication (SSI) ranging, estimating distance by measuring the strength of the received signal. However, due to the susceptibility of signal strength to multipath effects, obstructions, and environmental interference, ranging accuracy is low, typically with an error of 3-5 meters, making it unsuitable for industrial-grade high-precision positioning. RFID positioning, also based on signal strength ranging, suffers from insufficient accuracy and weak anti-interference capabilities, only enabling area-level positioning and failing to provide precise coordinate information.

[0004] Bluetooth channel detection technology, a novel high-precision ranging method, is a core feature added to the BLE (Bluetooth Low Energy) 6.0 protocol. Based on the channel detection mechanism extended by the BLE 6.0 protocol, this technology can detect the multipath characteristics of the wireless channel by transmitting specific detection sequences, including the delay, phase, and amplitude parameters of direct, reflected, and scattered signals. A multipath signal separation algorithm filters out direct signals and eliminates interference from reflected and scattered signals. Combined with the electromagnetic wave propagation speed, it achieves accurate distance measurement between the terminal and the base station. Bluetooth channel detection technology achieves a ranging accuracy of 0.1-0.5m and boasts advantages such as low power consumption, low cost, and strong hardware compatibility. It is compatible with existing BLE 6.0 and later wireless communication modules, addressing the pain point of insufficient positioning accuracy in traditional Bluetooth.

[0005] In existing technologies, positioning methods based on multi-base station ranging often employ three-circle intersection positioning. This involves measuring the distances to the terminal from three base stations, drawing circles with the three base stations as centers and the measured distances as radii, and identifying the intersection of these three circles as the terminal's location. However, three-circle positioning is susceptible to ranging errors. When ranging errors exist, the three circles cannot intersect precisely at a single point, leading to a decrease in positioning accuracy. Some four-base station positioning schemes only use simple geometric intersection calculations, failing to consider the unsolvable equations caused by ranging errors, and lack mechanisms for identifying and eliminating abnormal base stations. When the ranging error of a single base station is too large, it severely affects the accuracy of the positioning results, making it difficult to meet the high robustness positioning requirements of industrial scenarios. Furthermore, existing schemes often use a fixed four-base station layout, failing to consider the differences in shape and size of the area to be positioned and the insufficient positioning accuracy in edge areas. They also lack flexible base station adjustment schemes and corresponding solution adaptation logic, further limiting the improvement of positioning accuracy. Furthermore, existing technologies do not deeply integrate Bluetooth channel detection's high-precision ranging with the four-circle positioning theory, thus failing to fully leverage the advantages of Bluetooth channel detection's low power consumption and high precision, and also failing to solve the dual problems of insufficient accuracy in traditional Bluetooth positioning and weak error resistance in four-circle positioning.

[0006] Therefore, there is an urgent need for an indoor four-circle positioning scheme that combines high-precision ranging via Bluetooth channel detection, reasonable base station layout, anti-error calculation algorithm, and fault-tolerant mechanism to solve the defects of existing technologies, such as low positioning accuracy, weak anti-interference ability, poor robustness, insufficient layout flexibility, high power consumption, and high cost, and achieve low power consumption, high accuracy, and high robustness indoor positioning. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention provides a solution. This invention offers a high-precision indoor four-circle positioning method and system based on Bluetooth channel detection and ranging.

[0008] In a first aspect, the present invention provides a high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging, comprising: Deploy a group of BLE base stations supporting the Bluetooth protocol in the indoor area to be located; the BLE base station group includes four basic BLE base stations and several supplementary BLE base stations. The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, and calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data. Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, a corresponding number of circular distance equations are established using the four-circle positioning theory. Initial calculations are performed according to the base station layout type and scenario, and the verification error is calculated. The initial positioning result that meets the preset error threshold is output as the target positioning result. If no initial positioning result exists, an overdetermined linear equation system of the corresponding dimension is constructed according to the number of deployed BLE base stations. The optimal approximate coordinates are obtained by solving the least squares method. The optimal approximate coordinates are substituted into the circular distance equations of all deployed BLE base stations to calculate the distance residual of each base station. Based on the distance residual of the base station and the preset residual threshold, abnormal base stations are eliminated, and the remaining BLE base stations are used to recalculate the positioning until the optimized positioning result is obtained as the target positioning result. The target positioning results are output to the positioning display platform, along with the working status, ranging data, and distance residuals of each BLE base station.

[0009] Secondly, the present invention provides a high-precision indoor four-circle positioning system based on Bluetooth channel detection and ranging, including a BLE base station, a BLE terminal to be positioned, a positioning calculation unit and a positioning display platform; The BLE base station group includes four basic BLE base stations deployed in the indoor area to be located and supporting the Bluetooth protocol, as well as several supplementary BLE base stations. The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data, and sends the ranging data to the positioning calculation unit. The positioning calculation unit communicates with BLE base stations and the BLE terminal to be located. Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, it establishes a corresponding number of circular distance equations using the four-circle positioning theory. It performs initial calculations according to the base station layout type and scenario, calculates and verifies the error, and outputs an initial positioning result that meets the preset error threshold as the target positioning result. If there is no initial positioning result, it constructs an overdetermined linear equation system of the corresponding dimension according to the number of deployed BLE base stations, solves it using the least squares method to obtain the optimal approximate coordinates, substitutes the optimal approximate coordinates into the circular distance equations of all deployed BLE base stations, calculates the distance residual of each base station, and eliminates abnormal base stations based on the distance residuals of the base stations and the preset residual threshold. It then uses the remaining BLE base stations to recalculate the positioning until an optimized positioning result is obtained as the target positioning result. The positioning display platform, connected to the positioning calculation unit, is used to receive and display the target positioning results of the BLE terminal to be positioned, and at the same time output the working status, ranging data and distance residuals of each BLE base station.

[0010] As an optional implementation, the four basic BLE base stations are arranged according to the rule of rectangular vertices; the supplementary BLE base stations are arranged at the midpoints of the sides of the basic base stations.

[0011] As an optional implementation method, Bluetooth channel detection includes: the BLE terminal to be located transmitting a preset detection sequence; all deployed BLE base stations receiving and capturing the direct signal, reflected signal and scattered signal of the wireless channel; filtering out the direct signal through a multipath signal separation algorithm; extracting the time delay parameter of the direct signal; and calculating the straight-line distance from the terminal to be located to each BLE base station in combination with the electromagnetic wave propagation speed.

[0012] As an optional implementation method, initial calculations are performed according to the base station layout type and different scenarios, including: Let x be the x-coordinate of the terminal to be located, y be the y-coordinate of the terminal to be located, L be the side length of the square base station layout, M be the length of the rectangle, N be the width of the rectangle, and r1, r2, r3 and r4 be the distances from the terminal to be located to each base station, respectively. In a scenario where four basic BLE base stations are arranged in a square layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xL)² + y² = r²; The equation of the circle corresponding to the third base station is: (xL)² + (yL)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yL)² = r⁴²; In a scenario where four basic BLE base stations are arranged in a rectangular layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xM)² + y² = r²; The equation of the circle corresponding to the third base station is: (xM)² + (yN)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yN)² = r₄²; In a scenario where four basic BLE base stations are arranged in a square layout combined with the layout of newly added base stations, a corresponding number of circular distance equations are added to the original four circular distance equations.

[0013] As an optional implementation, when the initial positioning result that meets the preset error threshold is output as the target positioning result, if the verification error of the initial positioning result is greater than or equal to the preset verification error threshold, then the initial positioning result is used as the target positioning result; if the verification error of the initial positioning result is less than the preset verification error threshold, then there is no initial positioning result.

[0014] As an optional implementation, an overdetermined linear equation system is constructed, and the optimal approximate coordinates are obtained by solving it using the least squares method, including: Let the coefficient matrix be A, the observation vector be b, and the coordinate vector to be determined be θ. The least squares solution is... , ( ) T As a transpose transformation, the overdetermined linear equation system is expressed as: Aθ = b; the least squares solution is = (A A) - ¹A b.

[0015] As an optional implementation, let (x) i , y i Let be the coordinates of the i-th BLE base station, n be the total number of base stations deployed, and r be the coordinates of the i-th base station. i e is the distance from the terminal to the i-th base station, measured via Bluetooth channel detection. i Let be the distance residual from the terminal to the i-th base station, and the optimal approximate coordinates be expressed as ( , The obtained optimal approximate coordinates ( , Substituting the equations for all deployed BLE base stations into the circular equations, the distance residuals for each base station are calculated and expressed as follows: r i |

[0016] As an optional implementation, abnormal base stations are eliminated based on the distance residual of the base station and a preset residual threshold, including: if the distance residual of the base station is greater than the preset residual threshold, then the base station is determined to be an abnormal base station and the abnormal base station is eliminated.

[0017] As an optional implementation, the remaining BLE base stations are used to recalculate the positioning, including: If the number of remaining base stations is greater than or equal to three, and includes three or more of the four basic BLE base stations, the least squares method is used to solve the problem. If the remaining base stations include newly added base stations, then the circle equation of the newly added base stations is combined with the elimination method of subtracting equations from each other or the least squares method for solving the problem. If the number of remaining base stations is less than three, the system will issue a base station abnormality alarm signal to prompt staff to check the base station status.

[0018] The beneficial effects of this invention are: (1) This invention deeply integrates the four-circle positioning theory with the Bluetooth channel detection high-precision ranging technology. Bluetooth channel detection has high ranging accuracy by detecting multipath characteristics and filtering direct signals. Combined with the geometric calculation of four-circle positioning and the least squares anti-error algorithm, the impact of ranging error on the positioning result is effectively reduced. At the same time, a rectangular basic layout is adopted, and the geometric configuration of the base station is optimized by adding a new base station to solve the problem of insufficient positioning accuracy in the edge area. (2) The present invention adopts the BLE protocol and Bluetooth channel detection technology, which enables both the base station and the terminal to support low power operation mode. At the same time, the Bluetooth hardware module is low in cost and highly compatible, and can be adapted to existing BLE 6.0 and above devices without large-scale hardware modification, thus reducing system deployment costs. (3) In view of the errors that may exist in the Bluetooth channel detection and ranging process, the present invention combines the four-circle positioning theory and uses the least squares method to solve the overdetermined equation system. The solution logic can be adapted to different base station layouts, effectively reducing the impact of ranging error on the positioning result. (4) The present invention sets up an abnormal base station identification and elimination mechanism. By residual analysis, it identifies BLE base stations with excessive ranging errors and eliminates them. The remaining base stations are used for repositioning, avoiding the failure of the overall positioning result due to the abnormal error of a single base station. This increases the redundancy of the system. Even if multiple base stations are abnormal, the remaining base stations can still meet the positioning requirements, improving the fault tolerance and robustness of the system. At the same time, the BLE protocol has strong anti-interference capabilities, further improving the robustness of the system operation. (5) The present invention can selectively add base stations to adapt to different indoor scenarios. The base station layout is simple and easy to deploy. The BLE base station supports addition and expansion, expanding the applicability of the system. Attached Figure Description

[0019] Figure 1 This is a flowchart of the high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the principle of the high-precision indoor four-circle positioning system based on Bluetooth channel detection and ranging provided in Embodiment 2 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Example 1 As an example, to address the problems existing in the prior art, this embodiment provides a high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging.

[0022] The implementation details of the method in this embodiment are described below. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0023] As attached Figure 1 As shown in the figure, the high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging provided in this embodiment includes the following steps.

[0024] Deploy a group of BLE base stations supporting the Bluetooth protocol in the indoor area to be located; the BLE base station group includes four basic BLE base stations and several supplementary BLE base stations.

[0025] Specifically, the four basic BLE base stations are deployed according to the rule of rectangular vertices; the supplementary BLE base stations are deployed at the midpoints of the sides of the basic base stations.

[0026] For example, four BLE base stations are arranged according to the vertex rule of a square, with the side length of the square being L. The coordinates of the four base stations are preset as follows: base station 1 (0,0), base station 2 (L,0), base station 3 (L,L), and base station 4 (0,L). The value of L ranges from 20 to 60m. In this embodiment, L=40m, which can be adjusted according to the actual scenario. All four BLE base stations support BLE 6.0 and above protocols, integrate Bluetooth channel detection and ranging units, enable Bluetooth channel detection function, and establish a low-power wireless communication connection with the BLE terminal to be located, ensuring the compatibility of ranging data and low-power transmission.

[0027] Depending on the shape, size, and positioning accuracy requirements of the area to be located, the basic layout can be adjusted. There are two adjustment schemes, which can be used individually or in combination: (1) Layout adjustment: If the area to be located is a rectangle (let the length of the rectangle be M, the width of the rectangle be N, M≠N), the basic square layout is adjusted to a rectangular layout, and the coordinates of the four BLE base stations are adjusted as follows: first base station (0,0), second base station (M,0), third base station (M,N), fourth base station (0,N). In this embodiment, M=50m and N=30m can be set. (2) Supplementing BLE base stations: Based on the four basic BLE base station layouts or the rectangular adjustment layout, add 1-2 supplementary BLE base stations to improve the positioning accuracy in the edge area and the system redundancy. The coordinates of the supplementary BLE base stations are set as follows (adapted to the basic square layout, L=40m): Supplementary BLE base station 5: (L / 2,0), i.e. (20,0), is deployed at the midpoint between the first base station and the second base station to supplement the ranging redundancy at the lower edge of the area to be located; Supplementary BLE base station 6: (L,L / 2), i.e. (40,20), is deployed at the midpoint between the second and third base stations to supplement the ranging redundancy on the right edge of the area to be located; Supplementing BLE base stations requires that they be consistent with the original base stations in terms of BLE protocol version (BLE 6.0 and above), Bluetooth channel detection and ranging function, and communication protocol to ensure the compatibility of ranging data and low-power transmission. If the area to be located is rectangular, the coordinates of the new base station should be adjusted to (M / 2,0) and (M,N / 2).

[0028] The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, and calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data.

[0029] Specifically, Bluetooth channel detection includes: the BLE terminal to be located transmits a preset detection sequence, all deployed BLE base stations receive and capture the direct signal, reflected signal and scattered signal of the wireless channel, the direct signal is filtered out through a multipath signal separation algorithm, the time delay parameter of the direct signal is extracted, and the straight-line distance from the terminal to be located to each BLE base station is calculated in combination with the electromagnetic wave propagation speed.

[0030] The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations (four basic BLE base stations and supplementary BLE base stations, totaling 4-6). Based on the Bluetooth channel detection mechanism of the BLE protocol, it captures multipath signals (direct signals, reflected signals, and scattered signals) of the wireless channel by transmitting a specific detection sequence. It extracts key parameters such as multipath delay, phase, and amplitude, and filters out direct signals through a multipath signal separation algorithm to eliminate interference from reflected and scattered signals. Combined with the electromagnetic wave propagation speed, it calculates the straight-line distance from the terminal to be located to each BLE base station to achieve high-precision ranging.

[0031] The distances corresponding to the four basic BLE base stations are denoted as r1, r2, r3, and r4, the distance corresponding to the supplementary BLE base station 5 is denoted as r5, and the distance corresponding to the supplementary BLE base station 6 is denoted as r6. r1 is the distance from the terminal to the first base station, r2 is the distance from the terminal to the second base station, r3 is the distance from the terminal to the third base station, r4 is the distance from the terminal to the fourth base station, r5 is the distance from the terminal to the supplementary BLE base station 5, and r6 is the distance from the terminal to the base station 6. During the ranging process, the BLE terminal communicates with the base station in a low-power mode to reduce the overall power consumption of the system.

[0032] Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, a corresponding number of circular distance equations are established using the four-circle positioning theory. Initial calculations are performed according to the base station layout type and scenario, and the verification error is calculated. The initial positioning result that meets the preset error threshold is output as the target positioning result. If no initial positioning result exists, an overdetermined linear equation system of the corresponding dimension is constructed according to the number of deployed BLE base stations. The optimal approximate coordinates are obtained by solving the least squares method. The optimal approximate coordinates are substituted into the circular distance equations of all deployed BLE base stations to calculate the distance residual of each base station. Based on the distance residual of the base station and the preset residual threshold, abnormal base stations are eliminated, and the remaining BLE base stations are used to recalculate the positioning until the optimized positioning result is obtained as the target positioning result.

[0033] The initial calculation is performed according to the base station layout type and different scenarios, including: Let x be the x-coordinate of the terminal to be located, y be the y-coordinate of the terminal to be located, (x,y) be the coordinates of the terminal to be located, L be the side length of the square base station layout, M be the length of the rectangle, N be the width of the rectangle, and r1, r2, r3 and r4 be the distances from the terminal to be located to each base station, respectively. Scenario 1: A scenario where four basic BLE base stations are arranged in a square layout. Establish four circular distance equations, expressed as: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xL)² + y² = r²; The equation of the circle corresponding to the third base station is: (xL)² + (yL)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yL)² = r4².

[0034] Subtracting the circle equation corresponding to the first base station from the circle equation corresponding to the second base station, and eliminating the quadratic term y², we get: x²-(xL)²=r1²-r2², and solving for x, we get: x=(r1²-r2²+L²) / (2L).

[0035] Similarly, by subtracting the circle equation corresponding to the first base station from the circle equation corresponding to the fourth base station and eliminating the quadratic term x², we get: y²-(yL)²=r1²-r4², and solving for y, we get: y=(r1²-r4²+L²) / (2L).

[0036] Substitute the obtained x and y into the circle equation corresponding to the third base station for verification. If the verification error is less than or equal to the preset error threshold (in this embodiment, the preset error threshold is 0.5m, which is adapted to the ranging accuracy of Bluetooth channel detection), then the initial positioning result is output.

[0037] Scenario 2: A scenario where four basic BLE base stations are arranged in a rectangular layout. Establish four circular distance equations, expressed as: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xM)² + y² = r²; The equation of the circle corresponding to the third base station is: (xM)² + (yN)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yN)² = r4².

[0038] Scenario 3: A scenario combining a square layout of four basic BLE base stations with a newly added base station layout. A corresponding number of new circular distance equations are added to the existing four circular distance equations.

[0039] For the basic layout / rectangular layout and supplementary BLE base stations (taking basic layout and supplementary BLE base station 5 and supplementary BLE base station 6 as examples), two new circular distance equations are added to the original four: Complete the equation of the circle corresponding to BLE base station 5: (xL / 2)² + y² = r5²; The equation for the circle corresponding to BLE base station 6 is: (xL)² + (yL / 2)² = r6².

[0040] The solution logic was adjusted as follows: x and y are solved by first using the equations of the four basic BLE base stations (the circle equations corresponding to the first base station, the second base station, and the fourth base station), and then the equations are substituted into the circle equations corresponding to the third base station, the supplementary BLE base station 5, and the supplementary BLE base station 6 for verification.

[0041] Specifically, when the output initial positioning result that meets the preset error threshold is used as the target positioning result, if the verification error of the initial positioning result is greater than or equal to the preset verification error threshold, then the initial positioning result is used as the target positioning result; if the verification error of the initial positioning result is less than the preset verification error threshold, then there is no initial positioning result.

[0042] In this embodiment, if the verification error of all equations is less than or equal to 0.5m, the initial positioning result is output; if the verification error of any one or more equations exceeds 0.5m, it is determined that there is an error in ranging (which may be caused by multipath interference residue and base station anomalies, etc.), and least squares robust error solution is used.

[0043] When the verification in step S3 fails, i.e. the multiple circles have no precise intersection (the ranging error causes the equation system to be overdetermined and have no solution), in combination with the error resistance requirements of four-circle positioning, an overdetermined linear equation system of the corresponding dimension is constructed according to the number of BLE base stations deployed.

[0044] Specifically, an overdetermined system of linear equations is constructed, and the optimal approximate coordinates are obtained by solving it using the least squares method, including: Let the coefficient matrix be A, the observation vector be b, and the coordinate vector to be determined be θ. The least squares solution is... , ( ) T As a transpose transformation, the overdetermined linear equation system is expressed as: Aθ = b; the least squares solution is = (A A) - ¹A b.

[0045] The coefficient matrix is ​​a linear matrix determined by the geometric layout of the base stations. It is only related to the spacing and shape of the base stations and is used to establish a linear mapping relationship between the terminal coordinates and the ranging difference. x represents the horizontal coordinate of the terminal to be located, y represents the vertical coordinate of the terminal to be located, and the coordinate vector to be determined is the two-dimensional planar coordinate (x, y) of the BLE terminal to be located, θ = [x, y]^ T The observation vector represents the observation value vector obtained by real-time ranging calculation of each base station, and is determined based on the ranging r1, r2, r3 and r4 from the terminal to be located to each base station.

[0046] Matrix A and vector b are adjusted according to the base station layout as follows to ensure that the calculation results are compatible with the ranging accuracy of Bluetooth channel detection: (1) Under the basic square layout, subtract the circle equation corresponding to the first base station from the circle equation corresponding to the second base station, subtract the circle equation corresponding to the first base station from the circle equation corresponding to the fourth base station, subtract the circle equation corresponding to the second base station from the circle equation corresponding to the third base station, and subtract the circle equation corresponding to the fourth base station from the circle equation corresponding to the third base station to obtain four linear equations: 2Lx = r1² - r2² + L²; 2Ly = r1² - r4² + L²; 2Ly = r2² - r3² + L²; 2Lx = r4² - r3² + L².

[0047] Represented in matrix form Aθ=b, where: A=[[2L,0],[0,2L],[0,2L],[2L,0]]; b=[r1²-r2²+L²,r1²-r4²+L²,r2²-r3²+L²,r4²-r3²+L²]^T.

[0048] Similarly, for a rectangular layout, we can obtain: A=[[2M,0],[0,2N],[0,2N],[2M,0]]; b=[r1²-r2²+M²,r1²-r4²+N²,r2²-r3²+(M²-N²),r4²-r3²-(M²-N²)]^T; The least squares solution is =(A A) - ¹A b, The calculation formula for the basic square layout is: =[(r1²-r2²)+(r4²-r3²)+2L²] / (4L); =[(r1²-r4²)+(r2²-r3²)+2L²] / (4L); The calculation formula for a rectangular layout has been adjusted as follows: =[(r1²-r2²)+(r4²-r3²)+2M²] / (4M); =[(r1²-r4²)+(r2²-r3²)+2N²] / (4N); (2) Basic layout and 2 supplementary BLE base stations (a total of 6 base stations, taking the basic square layout as an example).

[0049] Based on the original four linear equations, the circular equation corresponding to the first base station is subtracted from the circular equation corresponding to supplementary BLE base station 5, and the circular equation corresponding to the second base station is subtracted from the circular equation corresponding to supplementary BLE base station 6, resulting in two linear equations: 2Lx = 2(r1² - r5²) + L² / 2; 2Ly = 2(r²² - r⁶²) + L² / 2; Matrix A is expanded to 6 rows and 2 columns: A=[[2L,0],[0,2L],[0,2L],[2L,0],[2L,0],[0,2L]] Vector b is expanded to 6 dimensions: b=[r1²-r2²+L²,r1²-r4²+L²,r2²-r3²+L²,r4²-r3²+L²,r1²-r5²+(L / 2)²,r2²-r6²+(L / 2)²]^T; The least squares solution still uses =(A A) - ¹A Substituting b into the expanded A and b, we obtain the optimal approximate coordinates. , The specific calculation formula has been adjusted as follows: =[(r1²-r2²)+(r4²-r3²)+2(r1²-r5²)+2L²+L² / 2] / (6L) =[(r1²-r4²)+(r2²-r3²)+2(r2²-r6²)+2L²+L² / 2] / (6L) In this embodiment, with the basic square layout (L=40m) and two supplementary BLE base stations, the following is obtained after substitution: =[(r1²-r2²)+(r4²-r3²)+2(r1²-r5²)+3200+400] / 240=[(r1²-r2²)+(r4²-r3²)+2(r1²-r5²)+3600] / 240; =[(r1²-r4²)+(r2²-r3²)+2(r2²-r6²)+3200+400] / 240=[(r1²-r4²)+(r2²-r3²)+2(r2²-r6²)+3600] / 240.

[0050] As an optional implementation, abnormal base stations are eliminated based on the distance residual of the base station and a preset residual threshold, including: if the distance residual of the base station is greater than the preset residual threshold, then the base station is determined to be an abnormal base station and the abnormal base station is eliminated.

[0051] Specifically, let (x) i , y i Let be the coordinates of the i-th BLE base station, n be the total number of base stations deployed, and r be the coordinates of the i-th base station. i e is the distance from the terminal to the i-th base station, measured via Bluetooth channel detection. i Let be the distance residual from the terminal to the i-th base station, and the optimal approximate coordinates be expressed as ( , The obtained optimal approximate coordinates ( , Substituting the equations for all deployed BLE base stations into the circular equations, the distance residuals for each base station are calculated and expressed as follows: r i |

[0052] After removing abnormal base stations, it is necessary to ensure that the number of remaining base stations is not less than 3 (to ensure the uniqueness and accuracy of the four-circle positioning solution). The positioning solution is then recalculated using the remaining BLE base stations, including: If the number of remaining base stations is greater than or equal to three, and includes three or more of the four basic BLE base stations, the least squares method is used to solve the problem. If the remaining base stations include newly added base stations, then the circle equation of the newly added base stations is combined with the elimination method of subtracting equations from each other or the least squares method for solving the problem. If the number of remaining base stations is less than three, the system will issue a base station abnormality alarm signal to prompt staff to check the base station status.

[0053] The target positioning results are output to the positioning display platform, along with the working status, ranging data, and distance residuals of each BLE base station.

[0054] For example, under a basic square layout, the measured distances from the terminal to the four base stations are: r1=25.0m, r2=30.1m, r3=33.0m, and r4=29.0m (distance measurement error ≤0.1m). Establish the equations for the distance between the four circles. Substituting r1, r2, r3, r4 and L=40m into the equations, we can calculate x=(25.0² - 30.1² + 40²) / (2×40)=(625-906.01+1600) / 80=1318.99 / 80≈16.49m, y=(25.0² - 29.0² + 40²) / (2×40)=(625-841+1600) / 80=1384 / 80=17.3m; Substituting x≈16.49m and y=17.3m into the circular equation of the third base station, (40-16.49)² + (40-17.3)²≈23.51² + 22.7²≈552.72 + 515.29 = 1068.01 ≠ 33.0² = 1089, the error is about 20.99m, which is greater than the preset error threshold of 0.5m. It is determined that there is an error in the ranging (due to multipath interference residue caused by the obstruction of the shelves in the warehouse). Construct an overdetermined system of linear equations, substitute r1, r2, r3, r4 and L=40m, and calculate the optimal approximate coordinates: =[(25.0²-30.1²)+(29.0²-33.0²)+3200] / 160=[(625-906.01)+(841-1089)+3200] / 160=(-281.01-248+3200) / 160=2670.99 / 160≈16.69m; =[(25.0²-29.0²)+(30.1²-33.0²)+3200] / 160=[(625-841)+(906.01-1089)+3200] / 160=(-216-182.99+3200) / 160=2801.01 / 160≈17.51m; The residual of the first base station, e1, is approximately equal to |√(16.69²+17.51²)-25.0|≈|24.23-25.0|=0.77m>0.5m (abnormal, affected by the obstruction of the shelf). The residual of the second base station is e2 = |√((16.69-40)²+17.51²)-30.1|≈|26.98-30.1|=3.12m>0.5m, which is determined to be an abnormal base station (obstructed by warehouse pillars). The residual of the third base station, e3, is calculated as follows: |√((16.69-40)²+(17.51-40)²)-33.0|≈|32.85-33.0|=0.15m≤0.5m; The residual of the fourth base station is e4 = |√(16.69²+(17.51-40)²)-29.0|≈|29.62-29.0|=0.62m>0.5m (slight anomaly). After removing the first, second, and fourth abnormal base stations, the remaining third base station (less than three) triggers a base station anomaly alarm signal, prompting staff to check for base station obstructions. Staff adjust the installation positions of the first and fourth base stations to avoid shelf obstructions and remeasure the corrected distances: r1 = 24.8m, r4 = 28.9m, while r2 and r3 remain unchanged. The least squares robust error calculation and abnormal base station identification and removal are then re-executed to calculate the optimal approximate coordinates. ≈17.98m The distance is approximately 17.26m. The residual of each base station is less than or equal to 0.5m. The final positioning coordinates are determined to be (17.98m, 17.26m).

[0055] For example, in a scenario with a basic layout and two supplementary BLE base stations: Based on the four basic BLE base station coordinates: base station 1 (0,0), base station 2 (40,0), base station 3 (40,40), and base station 4 (0,40), two supplementary BLE base stations are added, with coordinates of supplementary (20, 0) (midpoint between base station 1 and base station 2) and base station 6 (40, 20) (midpoint between base station 2 and base station 3). All six base stations support the BLE 6.0 protocol, enable Bluetooth channel detection ranging function, establish a low-power wireless communication connection with the BLE terminal to be located, and ensure ranging data compatibility. The BLE terminal and six BLE base stations respectively performed Bluetooth channel detection. The measured distances from the terminal to each base station were: r1=24.8m, r2=30.1m, r3=32.9m, r4=28.9m, r5=26.5m, and r6=30.8m (the ranging error was less than or equal to 0.1m). Six circular distance equations are established. Prioritizing the use of the circular equations corresponding to the first, second, and fourth base stations to solve for x and y, we obtain x = (24.8² - 30.1² + 40²) / (2×40) = (615.04 - 906.01 + 1600) / 80 = 1309.03 / 80 ≈ 16.36 m, y = (24.8² - 28.9² + 40²) / (2×40) = (615.04 - 906.01 + 1600) / 80 = 1309.03 / 80 ≈ 16.36 m, y = (24.8² - 28.9² + 40²) / (2×40) = 160 ... 40²) / (2×40)=(615.04-835.21+1600) / 80=1379.83 / 80≈17.25m; Substituting x and y into the circle equation corresponding to the third base station, the corresponding circle equation is verified and supplemented into the circle equation corresponding to BLE base station 6. The verification error of the circle equation corresponding to the third base station is about 0.6m (exceeding the threshold of 0.5m). The supplemented circle equation is: (16.36-20)²+17.25²≈13.25+297.56=310.81≠26.5²=702.25 (the error exceeds the preset error threshold). Equation 6: (16.36-40)²+(17.25-20)²≈558.77+7.56=566.33≠30.8²=948.64 (the error exceeds the preset error threshold). It is determined that there is an error in the ranging. Construct a 6-dimensional overdetermined linear equation system and use least squares robust solution. The matrix A = [[80,0],[0,80],[0,80],[80,0],[80,0],[0,80]], and the vector b = [24.8²-30.1²+1600, 24.8²-28.9²+1600, 30.1²-32.9²+1600, 28.9²-32.9²+1600, 24.8²-26.5²+400, 30.1²-30.8²+400]^T = [-281.97, -219.17, -177.8, -256, -88.61, -42.55]^T. Substitute these values ​​into the least squares formula to calculate the optimal approximate coordinates. =[(24.8²-30.1²)+(28.9²-32.9²)+2(24.8²-26.5²)+3600] / 240=[-281.97-256+2×(-88.61)+3600] / 240=(2974.81) / 240≈12.39m; =[(24.8²-28.9²)+(30.1²-32.9²)+2(30.1²-30.8²)+3600] / 240=[-219.17-177.8+2×(-42.55)+3600] / 240=(3017.93) / 240≈12.57m; Abnormal base station identification and removal, and calculation of residuals for 6 base stations: The residual of the first base station, e1, is approximately equal to |√(12.39²+12.57²)-24.8|, which is approximately equal to |17.66-24.8|=7.14m>0.5m (abnormal). The residual of the second base station is e2≈|√((12.39-40)²+12.57²)-30.1|≈|29.68-30.1|=0.42m≤0.5m; The residual of the third base station is e3≈|√((12.39-40)²+(12.57-40)²)-32.9|≈|39.65-32.9|=6.75m>0.5m (abnormal); The residual of the fourth base station is e4≈|√(12.39²+(12.57-40)²)-28.9|≈|30.65-28.9|=1.75m>0.5m (abnormal); The residual of BLE base station 5 is approximately e5≈|√((12.39-20)²+12.57²)-26.5|≈|14.95-26.5|=11.55m>0.5m (abnormal). The residual of BLE base station 6 is approximately e6≈|√((12.39-40)²+(12.57-20)²)-30.8|≈|30.15-30.8|=0.65m>0.5m (slight anomaly). After removing the abnormal first, third, and fourth base stations and the supplementary BLE base station 5, the remaining second base station and supplementary BLE base station 6 (less than 3) trigger an alarm signal from the system, prompting staff to check the status of the first, third, fourth, and supplementary BLE base stations 5. After investigation, staff found that the first, third, fourth, and supplementary BLE base stations 5 were obstructed by warehouse goods. After adjusting the base station positions, the corrected distances were measured again: r1=24.7m, r3=32.8m, r4=28.8m, r5=26.4m, while r2 and r6 remained unchanged. Steps 4 and 5 were then repeated to calculate the optimal approximate coordinates. ≈17.97m The distance is approximately 17.24m. The residual of each base station is less than or equal to 0.5m. The final positioning coordinates are determined to be (17.97m, 17.24m).

[0056] When adding a supplementary BLE base station, matrix A is 5 rows and 2 columns, and vector b is 5 dimensions. The solution logic follows the above extension method, only adding the equation terms corresponding to the base station to ensure that the solution accuracy is adapted to the ranging level of Bluetooth channel detection.

[0057] This invention deeply integrates the four-circle positioning theory with Bluetooth channel detection high-precision ranging technology. Bluetooth channel detection achieves ranging accuracy of 0.1-0.5m by detecting multipath characteristics and filtering direct signals. Combined with the geometric calculation of four-circle positioning and the least squares error-resistant algorithm, the impact of ranging error on the positioning result is effectively reduced. At the same time, a rectangular basic layout is adopted, and the geometric configuration of the base station is optimized by adding a new base station to solve the problem of insufficient positioning accuracy in the edge area. Finally, the positioning accuracy can be stabilized within 0.5m, which far exceeds the traditional BLE positioning accuracy.

[0058] This invention employs the BLE protocol and Bluetooth channel detection technology, enabling both the base station and the terminal to support low-power operation modes, with energy consumption far lower than that of ultra-wideband positioning systems. At the same time, the Bluetooth hardware module is low-cost and highly compatible, and can be adapted to existing BLE 6.0 and above devices without large-scale hardware modifications, reducing system deployment costs and demonstrating good industrialization prospects.

[0059] This invention addresses the potential errors such as residual multipath interference and signal obstruction during Bluetooth channel detection and ranging. It combines four-circle positioning theory with the least squares method to solve the overdetermined equations, and the solution logic can be adapted to different base station layouts, effectively reducing the impact of ranging errors on positioning results. The addition of new base stations increases the constraints, further enhancing the error resistance.

[0060] This invention establishes an abnormal base station identification and removal mechanism. By using residual analysis to identify BLE base stations with excessive ranging errors, these base stations are removed and repositioned using the remaining base stations, thus preventing the overall positioning result from failing due to the abnormal error of a single base station. The addition of base stations increases system redundancy, ensuring that even if multiple base stations malfunction, the remaining base stations can still meet the positioning requirements, improving the system's fault tolerance and robustness. At the same time, the BLE protocol has strong anti-interference capabilities, further enhancing the robustness of system operation.

[0061] This invention allows for the selective addition of new base stations to adapt to different indoor scenarios. The base station layout is simple and easy to deploy. The BLE base stations support addition and expansion, and the calculation logic can be adapted synchronously without overturning the original technical framework. In the future, the Bluetooth channel detection and ranging algorithm (such as the multipath signal separation algorithm) and the four-circle positioning calculation logic can be further optimized according to the positioning accuracy requirements to improve system performance. At the same time, it is compatible with subsequent upgrades of the BLE protocol, expanding the applicability of the system.

[0062] Example 2 Based on the same principle as the method shown in Embodiment 1 of the present invention, as illustrated in the appendix. Figure 2 As shown, a high-precision indoor four-circle positioning system based on Bluetooth channel detection and ranging includes a BLE base station, a BLE terminal to be positioned, a positioning calculation unit, and a positioning display platform. The BLE base station group includes four basic BLE base stations deployed in the indoor area to be located and supporting the Bluetooth protocol, as well as several supplementary BLE base stations. The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data, and sends the ranging data to the positioning calculation unit. The positioning calculation unit communicates with BLE base stations and the BLE terminal to be located. Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, it establishes a corresponding number of circular distance equations using the four-circle positioning theory. It performs initial calculations according to the base station layout type and scenario, calculates and verifies the error, and outputs an initial positioning result that meets the preset error threshold as the target positioning result. If there is no initial positioning result, it constructs an overdetermined linear equation system of the corresponding dimension according to the number of deployed BLE base stations, solves it using the least squares method to obtain the optimal approximate coordinates, substitutes the optimal approximate coordinates into the circular distance equations of all deployed BLE base stations, calculates the distance residual of each base station, and eliminates abnormal base stations based on the distance residuals of the base stations and the preset residual threshold. It then uses the remaining BLE base stations to recalculate the positioning until an optimized positioning result is obtained as the target positioning result. The positioning display platform, connected to the positioning calculation unit, is used to receive and display the target positioning results of the BLE terminal to be positioned, and at the same time output the working status, ranging data and distance residuals of each BLE base station.

[0063] As an optional implementation, the four basic BLE base stations are arranged according to the rule of rectangular vertices; the supplementary BLE base stations are arranged at the midpoints of the sides of the basic base stations.

[0064] As an optional implementation method, Bluetooth channel detection includes: the BLE terminal to be located transmitting a preset detection sequence; all deployed BLE base stations receiving and capturing the direct signal, reflected signal and scattered signal of the wireless channel; filtering out the direct signal through a multipath signal separation algorithm; extracting the time delay parameter of the direct signal; and calculating the straight-line distance from the terminal to be located to each BLE base station in combination with the electromagnetic wave propagation speed.

[0065] As an optional implementation method, initial calculations are performed according to the base station layout type and different scenarios, including: Let x be the x-coordinate of the terminal to be located, y be the y-coordinate of the terminal to be located, L be the side length of the square base station layout, M be the length of the rectangle, N be the width of the rectangle, and r1, r2, r3 and r4 be the distances from the terminal to be located to each base station, respectively. In a scenario where four basic BLE base stations are arranged in a square layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xL)² + y² = r²; The equation of the circle corresponding to the third base station is: (xL)² + (yL)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yL)² = r⁴²; In a scenario where four basic BLE base stations are arranged in a rectangular layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xM)² + y² = r²; The equation of the circle corresponding to the third base station is: (xM)² + (yN)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yN)² = r₄²; In a scenario where four basic BLE base stations are arranged in a square layout combined with the layout of newly added base stations, a corresponding number of circular distance equations are added to the original four circular distance equations.

[0066] As an optional implementation, when the initial positioning result that meets the preset error threshold is output as the target positioning result, if the verification error of the initial positioning result is greater than or equal to the preset verification error threshold, then the initial positioning result is used as the target positioning result; if the verification error of the initial positioning result is less than the preset verification error threshold, then there is no initial positioning result.

[0067] As an optional implementation, an overdetermined linear equation system is constructed, and the optimal approximate coordinates are obtained by solving it using the least squares method, including: Let the coefficient matrix be A, the observation vector be b, and the coordinate vector to be determined be θ. The least squares solution is... , ( ) T As a transpose transformation, the overdetermined linear equation system is expressed as: Aθ = b; the least squares solution is = (A A) - ¹A b.

[0068] As an optional implementation, let (x) i , y i Let be the coordinates of the i-th BLE base station, n be the total number of base stations deployed, and r be the coordinates of the i-th base station. i e is the distance from the terminal to the i-th base station, measured via Bluetooth channel detection. i Let be the distance residual from the terminal to the i-th base station, and the optimal approximate coordinates be expressed as ( , The obtained optimal approximate coordinates ( , Substituting the equations for all deployed BLE base stations into the circular equations, the distance residuals for each base station are calculated and expressed as follows: r i |

[0069] As an optional implementation, abnormal base stations are eliminated based on the distance residual of the base station and a preset residual threshold, including: if the distance residual of the base station is greater than the preset residual threshold, then the base station is determined to be an abnormal base station and the abnormal base station is eliminated.

[0070] As an optional implementation, the remaining BLE base stations are used to recalculate the positioning, including: If the number of remaining base stations is greater than or equal to three, and includes three or more of the four basic BLE base stations, the least squares method is used to solve the problem. If the remaining base stations include newly added base stations, then the circle equation of the newly added base stations is combined with the elimination method of subtracting equations from each other or the least squares method for solving the problem. If the number of remaining base stations is less than three, the system will issue a base station abnormality alarm signal to prompt staff to check the base station status.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging, characterized in that, include: Deploy a group of BLE base stations supporting the Bluetooth protocol in the indoor area to be located; The BLE base station group consists of four basic BLE base stations and several supplementary BLE base stations. The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, and calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data. Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, a corresponding number of circular distance equations are established using the four-circle positioning theory. Initial calculations are performed according to the base station layout type and scenario, and the verification error is calculated. The initial positioning result that meets the preset error threshold is output as the target positioning result. If no initial positioning result exists, an overdetermined linear equation system of the corresponding dimension is constructed according to the number of deployed BLE base stations. The optimal approximate coordinates are obtained by solving the least squares method. The optimal approximate coordinates are substituted into the circular distance equations of all deployed BLE base stations to calculate the distance residual of each base station. Based on the distance residual of the base station and the preset residual threshold, abnormal base stations are eliminated, and the remaining BLE base stations are used to recalculate the positioning until the optimized positioning result is obtained as the target positioning result. The target positioning results are output to the positioning display platform, along with the working status, ranging data, and distance residuals of each BLE base station.

2. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, The four basic BLE base stations are deployed according to the rule of rectangular vertices; the supplementary BLE base stations are deployed at the midpoints of the sides of the basic base stations.

3. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, Bluetooth channel detection includes: the BLE terminal to be located transmits a preset detection sequence, all deployed BLE base stations receive and capture the direct, reflected and scattered signals of the wireless channel, the direct signal is filtered out through a multipath signal separation algorithm, the time delay parameter of the direct signal is extracted, and the straight-line distance from the terminal to be located to each BLE base station is calculated in combination with the electromagnetic wave propagation speed.

4. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, Initial calculations are performed based on the base station layout type and different scenarios, including: Let x be the x-coordinate of the terminal to be located, y be the y-coordinate of the terminal to be located, L be the side length of the square base station layout, M be the length of the rectangle, N be the width of the rectangle, and r1, r2, r3 and r4 be the distances from the terminal to be located to each base station, respectively. In a scenario where four basic BLE base stations are arranged in a square layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xL)² + y² = r²; The equation of the circle corresponding to the third base station is: (xL)² + (yL)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yL)² = r⁴²; In a scenario where four basic BLE base stations are arranged in a rectangular layout, four circular distance equations are established, expressed as follows: The equation of the circle corresponding to the first base station is: x² + y² = r1²; The equation of the circle corresponding to the second base station is: (xM)² + y² = r²; The equation of the circle corresponding to the third base station is: (xM)² + (yN)² = r3²; The equation of the circle corresponding to the fourth base station is: x² + (yN)² = r₄²; In a scenario where four basic BLE base stations are arranged in a square layout combined with the layout of newly added base stations, a corresponding number of circular distance equations are added to the original four circular distance equations.

5. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, When the initial positioning result that meets the preset error threshold is output as the target positioning result, if the verification error of the initial positioning result is greater than or equal to the preset verification error threshold, then the initial positioning result is used as the target positioning result; if the verification error of the initial positioning result is less than the preset verification error threshold, then there is no initial positioning result.

6. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, Construct an overdetermined system of linear equations and solve it using the least squares method to obtain the optimal approximate coordinates. This includes: Let the coefficient matrix be A, the observation vector be b, the coordinate vector to be solved be θ, and the least squares solution be... , ( ) T As a transpose transformation, the overdetermined linear equation system is expressed as: Aθ = b; the least squares solution is = (A A) - ¹A b.

7. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, Let (x) i , y i Let be the coordinates of the i-th BLE base station, n be the total number of base stations deployed, and r be the coordinates of the i-th base station. i e is the distance from the terminal to the i-th base station, measured via Bluetooth channel detection. i Let be the distance residual from the terminal to the i-th base station, and the optimal approximate coordinates be expressed as ( , The obtained optimal approximate coordinates ( , Substituting the equations for all deployed BLE base stations into the circular equations, the distance residuals for each base station are calculated and expressed as follows: r i |。 8. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, Based on the distance residual of the base station and the preset residual threshold, abnormal base stations are removed, including: if the distance residual of a base station is greater than the preset residual threshold, the base station is determined to be an abnormal base station and is removed.

9. The high-precision indoor four-circle positioning method based on Bluetooth channel detection and ranging according to claim 1, characterized in that, The remaining BLE base stations are used to recalculate the positioning, including: If the number of remaining base stations is greater than or equal to three, and includes three or more of the four basic BLE base stations, the least squares method is used to solve the problem. If the remaining base stations include newly added base stations, then the circle equation of the newly added base stations is combined with the elimination method of subtracting equations from each other or the least squares method for solving the problem. If the number of remaining base stations is less than three, the system will issue a base station abnormality alarm signal to prompt staff to check the base station status.

10. A high-precision indoor four-circle positioning system based on Bluetooth channel detection and ranging, characterized in that, Includes BLE base station, BLE terminal to be located, positioning calculation unit and positioning display platform; The BLE base station group includes four basic BLE base stations deployed in the indoor area to be located and supporting the Bluetooth protocol, as well as several supplementary BLE base stations. The BLE terminal to be located performs Bluetooth channel detection with all deployed BLE base stations, extracts the characteristic parameters of multipath signals, filters out direct signals, calculates the distance data from the terminal to be located to each BLE base station to obtain ranging data, and sends the ranging data to the positioning calculation unit. The positioning calculation unit communicates with BLE base stations and the BLE terminal to be located. Based on the fixed coordinates of all deployed BLE base stations and the measured ranging data, it establishes a corresponding number of circular distance equations using the four-circle positioning theory. It performs initial calculations according to the base station layout type and scenario, calculates and verifies the error, and outputs an initial positioning result that meets the preset error threshold as the target positioning result. If there is no initial positioning result, it constructs an overdetermined linear equation system of the corresponding dimension according to the number of deployed BLE base stations, solves it using the least squares method to obtain the optimal approximate coordinates, substitutes the optimal approximate coordinates into the circular distance equations of all deployed BLE base stations, calculates the distance residual of each base station, and eliminates abnormal base stations based on the distance residuals of the base stations and the preset residual threshold. It then uses the remaining BLE base stations to recalculate the positioning until an optimized positioning result is obtained as the target positioning result. The positioning display platform, connected to the positioning calculation unit, is used to receive and display the target positioning results of the BLE terminal to be positioned, and at the same time output the working status, ranging data and distance residuals of each BLE base station.

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