Indoor positioning method based on Bluetooth and inertial sensor fusion

Abstract

The invention discloses an indoor positioning method based on Bluetooth and inertial sensor fusion, and the method comprises the following steps: S1, an offline stage: collecting the signal intensity of a Bluetooth base station at different distances, and fitting a distance formula through a piecewise function form; in the online stage, the distance between the Bluetooth base station and the to-be-positioned point is calculated according to the signal strength of each Bluetooth base station; s2, screening the scanned Bluetooth base stations, removing the Bluetooth base stations of which the signal intensity is lower than a threshold value to obtain pre-selected Bluetooth base stations, and calculating a positioning result according to coordinates of the pre-selected Bluetooth base stations; s3, calculating vector deviation angles by taking a positioning result in the step S2 as a starting point and the scanned coordinates of the base station as an end point so as to obtain multiple groups of deviation angle data, and limiting the vector deviation angles in a range of 0 to 2pi; s4, calculating the angle difference between the vector deviation angle corresponding to each group of Bluetooth base stations and the course angle of the inertial sensor, and constraining the result between 0 and pi; s5, performing signal compensation on the Bluetooth signal value according to the angle difference; and S6, selecting a given trilateral positioning equation, and performing position calculation in combination with the compensated signal value in the step S5 to obtain a final positioning result.

Description

Technical Field

[0001] The present invention relates to wireless sensor positioning technology, and specifically to an indoor positioning method based on the fusion of Bluetooth and inertial sensors. Background Art

[0002] In the field of Bluetooth positioning, a complex non-line-of-sight environment will cause a significant reduction in positioning accuracy. In the scenario of pedestrian positioning, the occlusion of the human body is one of the main reasons for non-line-of-sight.

[0003] Due to the occlusion of the human body on the transmitter and receiver, at the same position, there are also significant differences in the Bluetooth signal strength received by the receiver when the human body faces different directions; this difference makes it impossible for both the distance-based and fingerprint database-based Bluetooth positioning methods to obtain a relatively accurate positioning result.

[0004] Therefore, an inertial sensor is used to obtain the pedestrian heading information, and the pedestrian heading data is used to compensate the signal strength value of the occluded Bluetooth base station, so as to obtain a relatively accurate positioning result through the compensated signal strength data. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art; for this purpose, the present invention proposes an indoor positioning method based on the fusion of Bluetooth and inertial sensors, which is used to solve the technical problem that the existing technology does not consider the influence of the human body's different orientations on the Bluetooth signal strength, resulting in insufficient accuracy of the positioning result.

[0006] To achieve the above object, the present invention provides an indoor positioning method based on the fusion of Bluetooth and inertial sensors, including the following steps:

[0007] S1. In the offline stage, after collecting the Bluetooth base station signal strength at different distances, fit the distance formula in the form of a piecewise function; in the online stage, calculate the distance between the Bluetooth base station and the point to be located according to the signal strength of each Bluetooth base station;

[0008] S2. Screen the scanned Bluetooth base stations, remove the Bluetooth base stations with signal strength lower than the threshold to obtain the preselected Bluetooth base stations, and calculate the positioning result according to the coordinates of the preselected Bluetooth base stations;

[0009] S3. Take the positioning result in step S2 as the starting point and the coordinates of the scanned base station as the end point, calculate the vector deflection angle, so as to obtain multiple sets of deflection angle data, and limit these vector deflection angles within the range of 0 to 2π;

[0010] S4. Calculate the angle difference between the vector deflection angle corresponding to each base station and the heading angle of the inertial sensor, and constrain the result within the range of 0 to π;

[0011] S5. Implement signal compensation on the signal value according to the angle difference;

[0012] S6. Given the trilateration positioning equation, use the compensated signal value in S5 for position calculation to obtain the final positioning result.

[0013] Furthermore: The specific method of S1 is as follows:

[0014] To describe the relationship between the distance d from the base station to the point to be located and the signal strength r received by the point to be located, its expression is as follows:

[0015]

[0016] Among them, a, b, e, and f are all parameters to be fitted, and can be obtained by observing the data of the distance d and the Bluetooth signal strength r;

[0017] c, g are signal strength thresholds, d represents the distance from the base station to the point to be located, and r represents the signal strength.

[0018] Furthermore: The specific method of S2 is as follows:

[0019] If the number of preselected base stations is 1, directly use the coordinates of this base station as the primary positioning result;

[0020] If the number of preselected base stations is 2, use the reciprocal of the distance for weighted calculation of the weighted average of the coordinates of the two Bluetooth base stations, and use this average value as the primary positioning result;

[0021] If the number of preselected base stations is 3, use the trilateration method for coordinate calculation, and its calculated value is the primary positioning result;

[0022] If the number of preselected base stations is greater than 3, select the four base stations with the strongest signals from the scanned base stations, combine them in groups of 3, process each group combination through the trilateration equation, so as to obtain 4 groups of corresponding base stations and positioning coordinates; calculate the sum of the Euclidean distances between each group of positioning coordinates and the positioning coordinates of all other groups, and then remove the group of positioning coordinates with the farthest Euclidean distance from the positioning coordinates of other groups among the 4 groups of positioning coordinate data, and retain the average value of the positioning coordinates corresponding to the remaining 3 groups of base stations as the primary positioning result.

[0023] Furthermore: The preselected base stations are defined as (x i , y i ), i ∈ {1, 2,..., N}, where N is the total number of preselected base stations;

[0024] When the number of preselected base stations is 1, that is, N = 1 and i = 1, the positioning result at this time is:

[0025]

[0026] When the number of preselected base stations is 2, i.e., N = 2, the positioning result is:

[0027]

[0028] where w i represents the weight of the i-th base station, and its mathematical expression is:

[0029]

[0030] where d i is the distance from the point to be located to the positioning base station;

[0031] When the number of preselected base stations is equal to 3, i.e., N = 3, the basic positioning equation between the receiver and the transmitter in the trilateration positioning mode is:

[0032]

[0033] Simplifying the above system of equations into matrix form gives:

[0034] AX = B;

[0035]

[0036] Then, using the least squares method to solve, we can obtain:

[0037] X = (ATA) -1 A T B;

[0038] Thus, the positioning result is:

[0039]

[0040] where X(1) and X(2) respectively represent the first and second element values in X.

[0041] When the number of preselected base stations is greater than 3, then select 4 base stations with the strongest signals from the scanned base stations, i.e., N = 4, and combine them in groups of 3 base stations. The combinations are denoted as P1, P2, P3, and P4, a total of 4 groups. For each group of 3 base stations, use the basic positioning equation between the receiver and the transmitter in the above trilateration positioning mode to process, and obtain 4 groups of positioning results (x′ 1 , y′ 1 ), (x′ 2 , y′ 2 ), (x′ 3 , y′ 3 ), (x′ 4 , y′ 4 ) corresponding to P1, P2, P3, and P4;

[0042] Then, calculate the sum of distances from the positioning result of the k-th group to the positioning results of the other three groups:

[0043]

[0044] where D k represents the sum of distances from the positioning result of the k-th group to the positioning results of the other three groups, (x′ k , y′ k ) is the positioning result of the k-th group, k ∈ {1, 2, 3, 4};

[0045] Compare the above four sums of distances, obtain the number m of the positioning result corresponding to the maximum sum of distances, and eliminate the m-th group of positioning results (x m , y m );

[0046] Thus, the positioning result is:

[0047]

[0048] Furthermore: The calculation formula for the vector deflection angle in S3 is as follows:

[0049] B = mod(arctan(x i - x, y i - y), 2π);

[0050] where B is the vector deflection angle, mod represents the remainder operation, arctan represents the arctangent function, (x, y) is the positioning result obtained in step S2, and (x i , y i ) is the preselected base station screened out in step S2.

[0051] Furthermore: In S4, the formula for calculating the angle difference is as follows:

[0052] Δθ = mod(|h - B|, π);

[0053] where Δθ is the angle difference, h is the current inertial sensor heading angle, B is the vector deflection angle, and mod represents the remainder operation.

[0054] Furthermore: In S5, the specific method for implementing signal compensation for the angle difference is as follows:

[0055] When the angle difference is less than π / 2, the signal occlusion effect of the human body is relatively weak. Therefore, no additional compensation is performed on the signal strength within this range;

[0056] When the angle difference exceeds π / 2, the degree of signal occlusion by the human body will increase significantly with the increase of the angle difference. When the angle difference reaches π, that is, 180 degrees, and the human body is completely back to the base station, the occlusion effect reaches the maximum value, and at this time, the human body obstructs the signal most severely.

[0057] When the angle difference is greater than π / 2, the corresponding signal compensation formula for the angle difference is as follows:

[0058]

[0059] where r i is the compensated signal strength, and r 0 is the original signal strength; A is the parameter to be fitted, which can be obtained by comparing the relationship between the angle difference and the signal strength value under the same distance condition; Δθ is the angle difference.

[0060] Furthermore, in S6, the specific method for resolving the positioning result is as follows:

[0061] Use the compensated signal value in S5 to perform distance calculation. After obtaining the distance, select the positioning equation in S2 according to the number of preselected base stations to perform position calculation to obtain the final positioning result.

[0062] The beneficial effects of the present invention are as follows: This method aims at the problem that the signal attenuation of the base station behind the human body is serious due to human occlusion. By judging the angle difference between the base station and the human body orientation, the signal strength is compensated, thereby improving the ranging accuracy; and the compensated signal value is used for distance and position calculation to obtain a high-precision positioning solution; this method has a small amount of calculation and high positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention and the prior art, the following will briefly introduce the drawings required for the description of the embodiments and the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0064] Figure 1 is the flow schematic diagram of the present invention;

[0065] Figure 2 is the performance comparison diagram of the positioning method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0066] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be described and explained below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided by the present invention without creative efforts fall within the scope of protection of the present invention.

[0067] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present invention. For those of ordinary skill in the art, the present invention can also be applied to other similar scenarios based on these drawings without creative efforts.

[0068] In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed by the present invention, some design, manufacturing or production changes based on the technical content disclosed by the present invention are only conventional technical means and should not be understood as the content disclosed by the present invention being insufficient.

[0069] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0070] Please refer to Figure 1 , the system flowchart of the present invention, including the following steps:

[0071] S1. In the offline stage, after collecting the signal strengths of Bluetooth base stations at different distances, fit the distance formula in the form of a piecewise function; in the online stage, calculate the distance between the base station and the point to be located according to the signal strengths of each Bluetooth base station.

[0072] S2. Screen the scanned Bluetooth base stations, remove the Bluetooth base stations with signal strengths lower than the threshold to obtain the preselected Bluetooth base stations, and calculate the positioning result according to the coordinates of the preselected Bluetooth base stations.

[0073] S3. Taking the positioning result in step S2 as the starting point and the coordinates of the scanned base station as the end point, calculate the vector deflection angle, so as to obtain multiple sets of deflection angle data, and limit these vector deflection angles within the range of 0 to 2π.

[0074] S4. Calculate the angle difference between the vector deflection angle corresponding to each group of base stations and the heading angle of the inertial sensor, and constrain the result within the range of 0 to π.

[0075] S5. Perform signal compensation on the signal value according to the angle difference.

[0076] S6. Given the trilateration equation, use the signal value after signal compensation in S5 to perform position calculation to obtain the final positioning result.

[0077] Specifically:

[0078] First, convert the collected Bluetooth signal strength data into distance data; then, screen the base stations that meet the conditions according to the threshold for corresponding coordinate calculation; then, use the angle constraint of the inertial sensor to compensate the Bluetooth signal strength; finally, use the compensated Bluetooth base stations to perform positioning again to obtain the final positioning result.

[0079] To describe the relationship between the distance d from the base station to the point to be located and the signal strength r received by the point to be located at the base station, its expression is as follows:

[0080]

[0081] Among them, a, b, e, and f are all parameters to be fitted. The main purpose is to obtain the piecewise function of signal strength and distance through the distance data d and signal strength data r. The specific operation process includes the offline positioning stage and the real-time positioning stage:

[0082] In the offline positioning stage, collect the signal strength of the target base station under line-of-sight conditions at one-meter intervals to obtain a data set, and fit the piecewise function of signal strength and distance with this data set;

[0083] In the real-time positioning stage, according to the piecewise function of signal strength and distance fitted in the offline stage for each base station signal strength, calculate the distance between each base station and the point to be located, and then the relationship between the distance d from the base station to the point to be located and the signal strength r received by the point to be located at the base station can be described;

[0084] c and g are signal strength thresholds, d represents the distance from the base station to the point to be located, and r represents the signal strength.

[0085] The specific method of S2 is as follows:

[0086] If the number of preselected base stations is 1, directly use the coordinates of this base station as the primary positioning result;

[0087] If the number of preselected base stations is 2, use the reciprocal of the distance for weighted calculation, and the weighted average of the coordinates of the two base stations is the primary positioning result;

[0088] If the number of preselected base stations is 3, use the trilateration method for coordinate calculation, and its calculated value is the primary positioning result;

[0089] The number of preselected base stations is greater than 3. Select four base stations with the strongest signals from the scanned base stations and combine them in groups of 3. Process each group through the trilateration equation to obtain 4 groups of corresponding base stations and positioning coordinates; calculate the sum of the Euclidean distances between each group of positioning coordinates and all other groups of positioning coordinates, and then remove the group of positioning coordinates with the farthest Euclidean distance from other positioning coordinates among the 4 groups of positioning coordinates. Retain the average value of the positioning coordinates corresponding to the remaining 3 groups of base stations as the result of one positioning; the preselected base stations are defined as (x i , y i ), i ∈ {1, 2,..., N}, where N is the total number of preselected base stations. The specific processing for the following several situations is as follows:

[0090] When the number of preselected base stations is 1, that is, N = 1 and i = 1, the positioning result at this time is:

[0091]

[0092] When the number of preselected base stations is 2, that is, N = 2, the positioning result is:

[0093]

[0094] Among them, w i represents the weight of the i-th base station, and its mathematical expression is:

[0095]

[0096] Among them, d i is the distance from the point to be located to the positioning base station;

[0097] When the number of preselected base stations is equal to 3, that is, N = 3, the basic positioning equation between the receiver and the transmitter in the trilateration mode is:

[0098]

[0099] Simplify the above equations into matrix form to get:

[0100] AX = B;

[0101]

[0102] Then use the least squares method to solve and get:

[0103] X = (A T A) -1 A T B;

[0104] Thus, the positioning result is:

[0105]

[0106] Among them, X(1) and X(2) respectively represent the first and second element values in X.

[0107] When the number of preselected base stations is greater than 3, 4 base stations with the strongest signals are selected from the scanned base stations, that is, N = 4, and they are combined in a way of 3 base stations as a group. The combinations are denoted as P1, P2, P3, and P4, a total of 4 groups. The basic positioning equation between the receiver and the transmitter in the above trilateration positioning mode is used to process the 3 base stations in each group, and 4 groups of positioning results (x′ 1 , y′ 1 ), (x′ 2 , y′ 2 ), (x′ 3 , y′ 3 ), (x′ 4 , y′ 4 ) corresponding to P1, P2, P3, and P4 are obtained;

[0108] Then, calculate the sum of distances from each group of positioning results to the other 3 groups of positioning results:

[0109]

[0110] Among them, D k represents the sum of distances from the kth group of positioning results to the other 3 groups of positioning results, (x′ k , y′ k ) is the kth group of positioning results, k ∈ {1, 2, 3, 4};

[0111] Compare the above four groups of distance sums, obtain the number m of the positioning result corresponding to the maximum distance sum, and eliminate the mth group of positioning results (x m , y m );

[0112] Thus, the positioning result is:

[0113]

[0114] The calculation formula for the vector deflection angle in S3 is as follows:

[0115] B = mod(arctan(x i - x, y i - y), 2π);

[0116] Among them, B is the vector deflection angle, mod represents the remainder operation, arctan represents the arctangent function, (x, y) is the positioning result obtained in step S2, and (x i , y i ) is the preselected base station screened out in step S2.

[0117] In S4, the formula for calculating the angle difference is as follows:

[0118] Δθ = mod(|h - B|, π);

[0119] Where Δθ is the angle difference, h is the current heading angle of the inertial sensor, B is the vector deflection angle, and mod represents the remainder operation.

[0120] In S5, the specific method for implementing signal compensation for the angle difference is as follows:

[0121] When the angle difference is less than π / 2, the shielding effect of the human body on the signal is relatively weak, and no additional compensation is made to the signal strength within this range;

[0122] When the angle difference exceeds π / 2, the shielding degree of the human body on the signal will increase significantly with the increase of the angle difference. Until the angle difference reaches π, that is, 180 degrees, when completely facing away from the base station, the shielding effect reaches the maximum value, and at this time, the human body's obstruction of the signal is the most serious;

[0123] That is, only for the state where the angle difference is greater than π / 2, the corresponding signal compensation formula for the angle difference is implemented as follows:

[0124]

[0125] Where r i is the compensated signal strength, r 0 is the original signal strength; A is the parameter to be fitted, which can be obtained by comparing the relationship between the angle difference and the signal strength value under the same distance condition; Δθ is the angle difference.

[0126] In S6, the specific method for resolving the positioning result is as follows:

[0127] Use the compensated signal value in S5 for distance resolution. After obtaining the distance, select the positioning equation in S2 according to the number of preselected base stations for position resolution to obtain the final positioning result.

[0128] A specific embodiment provided by the present invention:

[0129] As Figure 2 shown:

[0130] In this embodiment, the coordinates of more than 4 Bluetooth positioning base stations are given. The tester holds the mobile phone and conducts tests at any position within the signal coverage area of the base station. Then, the mobile phone scans the signal strength of the Bluetooth positioning base station, converts the scanned signal strength into the distance from the tester to the base station through the distance formula, and finally, the final positioning result can be obtained through the trilateration method and the signal compensation formula; among the results of 50 positionings, the errors of the traditional positioning method are 2.2 meters respectively, and the positioning error of the method of the present invention is 1.17 meters.

[0131] Analyzed numerically, the method of the present invention has significant advantages in the pedestrian navigation scenario.

[0132] The above has given a very detailed application description of one or more embodiments of the present invention. However, the content described is only a specific example of the present invention and cannot be considered as limiting the scope of implementation of the application of the present invention. Any other methods and changes proposed based on the content of the present invention should fall within the scope of patent protection of the present invention.

Claims

1. An indoor positioning method based on the fusion of Bluetooth and inertial sensor, characterized in that: The steps include: S1, in the offline stage, after collecting the signal strength of the Bluetooth base station at different distances, the distance formula is fitted through a piecewise function form; in the online stage, the distance between the Bluetooth base station and the point to be located is calculated according to the signal strength of each Bluetooth base station; S2, screening the scanned Bluetooth base stations, removing the Bluetooth base stations with signal strength lower than the threshold, obtaining pre-selected Bluetooth base stations, and calculating the positioning results according to the coordinates of the pre-selected Bluetooth base stations; S3, taking the positioning result of step S2 as the starting point and the scanned Bluetooth base station coordinates as the end point, calculating the vector deflection angle, thereby obtaining multiple sets of deflection angle data, and limiting these vector deflection angles to the range of 0 to 2π; S4, calculating the angle difference between the vector deflection angle corresponding to each group of base stations and the heading angle of the inertial sensor, and constraining the result to be between 0 and π; S5. Perform signal compensation on the signal value according to the angle difference; S6. Select the given three-side positioning equation and combine it with the compensated signal value in S5 to perform position calculation to obtain the final positioning result.

2. According to claim 1, the indoor positioning method based on the fusion of Bluetooth and inertial sensor is characterized in that: The specific method of S1 is as follows: In order to describe the relationship between the distance d from the Bluetooth base station to the point to be located and the Bluetooth base station signal strength r received by the point to be located, the expression is as follows: Among them, a, b, e and f are all parameters to be fitted, which can be obtained by observing the distance d and signal strength r data; c and g are signal strength thresholds, d represents the distance from the base station to the point to be located, and r represents the signal strength.

3. The indoor positioning method based on the fusion of Bluetooth and inertial sensor according to claim 1 is characterized in that: The specific method of S2 is as follows: The pre-selected base station is defined according to the number (x i ,y i ), i∈{1,2,...,N}, N is the total number of pre-selected base stations; When the number of pre-selected base stations is 1, that is, N=1, i=1, the positioning result is: When the number of pre-selected base stations is 2, that is, N=2, the positioning result is: Among them, w i represents the weight of the i-th base station, and its mathematical expression is: Among them, d i The distance from the point to be located to the positioning base station; When the number of pre-selected base stations is equal to 3, that is, N = 3, the basic positioning equation between the receiver and the transmitter in the three-side positioning mode is: Simplifying the above equations into matrix form: AX = B; Then use the least squares method to solve it: X=(A T A) -1 A T B; Therefore, the positioning result is: Here, X(1) and X(2) represent the first and second element values ​​in X, respectively. When the number of pre-selected base stations is greater than 3, 4 base stations with the strongest signals are selected from the scanned base stations, that is, N=4, and they are combined in groups of 3 base stations. The combinations are recorded as P1, P2, P3, and P4, totaling 4 groups. The basic positioning equation between the receiver and the transmitter in the above-mentioned three-side positioning mode is used to process the 3 base stations in each group, and 4 groups of positioning results (x′1, y′1), (x′2, y′2), (x′3, y′3), and (x′4, y′4) corresponding to P1, P2, P3, and P4 are obtained. Then, calculate the sum of the distances from the Kth group of positioning results to the other three groups of positioning results: Among them, D k represents the sum of the distances between the kth group of positioning results and the other three groups of positioning results, (x′ k , y′ k ) is the kth group positioning result, k∈{1,2,3,4}; Compare the above four groups of distance sums, obtain the positioning result number m corresponding to the maximum distance sum, and eliminate the mth group of positioning results (x m ,y m ); Therefore, the positioning result is:

4. The indoor positioning method based on the fusion of Bluetooth and inertial sensor according to claim 1 is characterized in that: The calculation formula of the vector deflection angle in S3 is as follows: B=mod(arctan(x i -x,y i -y),2π); Wherein, B is the vector deflection angle, mod represents the modulus operation, arctan represents the inverse tangent function, (x, y) is the positioning result obtained in step S2, (x i ,y i ) is the pre-selected Bluetooth base station screened in step S2.

5. The indoor positioning method based on the fusion of Bluetooth and inertial sensor according to claim 1 is characterized in that: In S4, the formula for calculating the angle difference is as follows: Δθ=mod(|hB|,π); Among them, Δθ is the angle difference, h is the current inertial sensor heading angle, B is the vector deviation angle, and mod represents the modulo operation.

6. The indoor positioning method based on the fusion of Bluetooth and inertial sensor according to claim 1 is characterized in that: In S5, the specific method of implementing signal compensation for the angle difference is as follows: When the angle difference is less than π / 2, the human body's shielding effect on the signal is relatively weak, and no additional compensation is made for the signal strength within this range; When the angle difference exceeds π / 2, the degree of signal obstruction by the human body will increase significantly as the angle difference increases, until the angle difference reaches π, that is, 180 degrees, when the person is completely facing away from the base station, the obstruction effect reaches its maximum value, at which point the human body's obstruction to the signal is most serious; That is, only when the angle difference is greater than π / 2, the corresponding angle difference signal compensation formula is as follows: Among them, r i is the signal strength after compensation, r0 is the original signal strength; A is the parameter to be fitted, which can be obtained by comparing the relationship between the angle difference and the signal strength value under the same distance conditions; Δθ is the angle difference.

7. The indoor positioning method based on the fusion of Bluetooth and inertial sensor according to claim 1 is characterized in that: In S6: The compensated signal value in S5 is used to calculate the distance. After the distance is obtained, the positioning equation in S2 is selected according to the pre-selected number of base stations to calculate the position and obtain the final positioning result.

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