CN111220950A - Indoor positioning method based on LED visible light - Google Patents
Indoor positioning method based on LED visible light Download PDFInfo
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
An indoor positioning method based on LED visible light comprises the following steps: establishing a visible light channel transmission as a line-of-sight transmission model; the method comprises the steps that through a sensor node positioning algorithm APIT in a wireless sensor network, the initial positioning of an indoor positioning point is realized by combining the signal transmission time of visible light indoor communication; and adjusting the rotation angle of the LED lamp in the proximity range area according to the initially positioned positioning range information to enable the LED lamp to vertically irradiate the target object. According to the positioning range of initial positioning, three LED lamps with the closest distance are selected, the position estimation coordinates obtained through nonlinear optimization are used as coordinates of a centroid algorithm, weighting factors are used as constraints of the centroid algorithm, and therefore specific positioning of the target object is obtained. The method of the invention ensures that the positioning precision of each indoor position is high and the error jump is small through the fusion of the APIT method and the TDOA method; through discrete wavelet transform, the influence of noise link performance is reduced; the mutual influence of adjacent LED signals is avoided by the technologies of frequency division multiplexing, time division multiplexing and the like.
Description
Technical Field
The invention relates to the field of communication, in particular to an indoor positioning method based on LED visible light.
Background
Due to the complexity of indoor environment, the GPS technology commonly used for outdoor real-time positioning cannot be normally used, the occurrence of the indoor positioning technology just makes up the defects of positioning technologies such as GPS and the like, and the indoor positioning has good applicability in large indoor places such as hospitals, parking lots, markets and the like. The LED visible light has the advantages of wide available frequency band, no electromagnetic field interference, easy equipment construction, low error rate and the like, and the LED has fast response, can be modulated by high frequency, is green energy and has wide application range, so the technology based on the LED visible light positioning becomes an important choice for improving the indoor positioning precision.
Disclosure of Invention
The invention aims to provide a novel positioning method based on LED visible light so as to improve the indoor positioning accuracy.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
an indoor positioning method based on LED visible light comprises the following steps:
s1, establishing a visible light channel transmission as a line-of-sight transmission model, wherein the indoor moving speed of the target object is negligible relative to the speed of light, the visible light channel is regarded as a quasi-static channel, and the establishment of an equivalent baseband transmission model comprises the following steps:
wherein the content of the first and second substances,
the symbols are convolution symbols, R is the responsivity of the photodetector, x (t) is the optical power of the transmitted signal, h (t) is the impulse response of the channel, and n (t) represents the dominant noise source in the channel;
s2, realizing the initial positioning of the indoor positioning point by combining the signal transmission time of visible light indoor communication through a sensor node positioning algorithm APIT in the wireless sensor network;
s3, adjusting the rotation angle of the LED lamp in the proximity range area according to the initially positioned positioning range information to enable the LED lamp to vertically irradiate the target object; according to the positioning range of the initial positioning, three LED lamps with the nearest distance are selected, the centroid weighting algorithm is applied to the TDOA algorithm to further improve the positioning accuracy, the position estimation coordinates obtained through nonlinear optimization are used as the coordinates of the centroid algorithm, and the weighting factors are used as the constraints of the centroid algorithm, so that the specific positioning of the target object is obtained.
Further, the step S1 further includes: a discrete wavelet transform is added in S1 for denoising to improve link performance.
Further, the step S2 specifically includes:
s21, obtaining a triangular area through measurement, and recording a linear equation of three sides;
s22, after all triangular areas of the APIT test are obtained, calculating all recorded three-edge intersection points;
and S23, selecting points which can form a minimum polygon from the obtained intersection points, obtaining the minimum polygon, namely the range determined by the initial positioning, and selecting three LED lamps with a short distance range for final positioning.
Further, the step S3 further includes:
s31, on the basis of the TDOA method, the LEDs are nearest to the target object and are distributed circumferentially, so that the positioning errors of all indoor positions are uniform, and the positioning accuracy is improved;
s32, when the TDOA is used for positioning, the VLC based on the white light LED is used for transmitting the positioning reference information, and the signals sent by the adjacent LEDs can be separated on the target object and interference among the signals can not be caused by adopting carrier allocation, wavelength division multiplexing, time division multiplexing and code division multiplexing.
Further, in step S3, the calculation formula of the target object coordinates is specifically as follows:
wherein d iskkIs the distance between the target object and the LED lamp, NiSetting N for the number of LEDs participating in positioningi＝3，(xi，yiH) is the coordinate of the ith LED lamp, (x)kk，ykk0) the coordinates solved for the objective function; w is a1，w2，w3Is a weighting factor; (x, y) are coordinates of the target object.
Compared with the prior art, the invention has the beneficial effects that:
the method improves the positioning precision of each indoor position and reduces the error jump through the fusion of APIT and TDOA; the influence of noise link performance is reduced by Discrete Wavelet Transform (DWT), and the mutual influence of adjacent LED signals is avoided by adopting the technologies of Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM) and the like.
Drawings
FIG. 1 is a schematic view of an indoor visible light positioning scene according to the present invention;
FIG. 2 is a spatial model diagram of a visible light positioning system according to the present invention;
FIG. 3 is a two-dimensional model of the ceiling LED lighting distribution of the present invention;
FIG. 4 is a diagram of an initial positioning simulation of the present invention;
FIG. 5 is a noise reduction simulation of the present invention;
FIG. 6 is a graph comparing the actual radiation distribution of three Lambertian LEDs of the present invention with a 65 standard Lambertian distribution;
FIG. 7 is a diagram of a base station model according to the present invention.
The specific implementation mode is as follows:
the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example (b):
the specific coordinates of the target object are obtained by combining the APIT optimal triangle test method with the TDOA algorithm and applying the idea of the centroid weighting algorithm to indoor positioning. The positioning timeliness is improved by carrying out final positioning after the positioning range is determined through initial positioning, and the positioning accuracy is improved by fusing the two positioning methods.
Fig. 1 is a schematic view of an indoor visible light positioning scene provided in the present invention, and the method includes the following steps:
s1, in the embodiment of the present invention, the visible light channel model adopts a line-of-sight (LOS) link model, and since the moving speed of the target object in the room is negligible relative to the speed of light, the visible light channel is considered as a quasi-static channel. The equivalent baseband transmission model is established as follows:
wherein the content of the first and second substances,
the symbols are convolution symbols, R is the responsivity of the photodetector, x (t) is the optical power of the transmitted signal, h (t) is the impulse response of the channel, and n (t) represents the dominant source of noise in the channel. In order to improve the link performance, Discrete Wavelet Transform (DWT) technology is used for noise reduction. Matlab simulation is carried out, a 5-3 (m) closed room is simulated, as shown in figure 2, a designed LED lamp is placed at a position close to the central height, noise reduction is realized from three aspects of signal Decomposition (DWT), system processing and signal reconstruction (IDWT) through Discrete Wavelet Transform (DWT) technology, figure 5 is a noise reduction simulation graph, the left graph is an effect graph without discrete wavelet transform technology, and the right graph is an effect graph with discrete wavelet transformThe technical effect diagram is added with the discrete wavelet transform technology to realize the optimization of indoor communication and enhance the positioning effect.
S2, setting related parameters:
in order to ensure that the power of the LED light source for communication is lower than the power range causing damage to human eyes, the optical power of the transmitted signal should be lower than the maximum power borne by human eyes, and the formula for setting the maximum power here is as follows:
where T is the signal age.
To ensure the communication effect, the measured received optical power formula is as follows:
PrLOS＝Hlos(0)×Pt
wherein Hlos(0) For producing a direct gain, P, of an optical signal from a transmitter to a receivertIs the transmit power of the transmitter.
The radiation model used satisfies a lambertian radiation model, the light emitting mode of the LED can be represented by a relative radiation intensity distribution diagram as shown in fig. 6, and the abscissa in the relative radiation intensity distribution diagram represents the beam radiation angle, i.e. the included angle between the beam radiation direction and the center normal of the LED; the ordinate represents the relative radiation intensity, i.e. the relative ratio of the radiation intensity to the central radiation intensity of the LED. The relative radiation intensity distribution graph shows the relationship between the LED radiation angle and the radiation intensity. The light emitting modes of the LG-XP3535 type 365nm ultraviolet, the Cree-XPE type 455nm blue and the light macro-XP 3535 type 750nm infrared LEDs are all marked as Lambert, the visual angle is 130 degrees (namely the half-power angle is 65 degrees), and FIG. 7 shows the actual relative radiation intensity distribution graph and phi of the LEDs1/2For comparison between the 65 ° standard lambertian distribution plots, the curves show good consistency, which indicates that the degree of fitting of the lambertian luminescence pattern to the actual radiation pattern is very high, and therefore the radiation intensity is highest when the target object is vertically illuminated indoors.
S4, performing initial positioning when the target object enters the room and continuously moves, wherein the distribution diagram of the LED on the ceiling is shown in figure 3, and if the positioned point is positioned in the triangular area through the optimal triangular inner point test (PIT) of APIT, the triangular area is reserved, after the tested triangular area set is obtained, the intersection points of all triangles in the triangular area set are calculated, and the minimum polygon which can be formed by the intersection points is obtained. And determining the positioning range of the initial positioning. And adjusting the rotation angles of other lamps according to the initial positioning range, so that the LED lamp vertically irradiates the target object, the illumination radiation intensity received by the target object is within the ideal set radiation intensity range, the step is completed, and the positioning range is determined. As shown in fig. 4, x is a target object, and a hatched portion in the drawing is an initial positioning range, and final positioning is performed by the LEDs 1, 2, and 3 which are close to the initial positioning range.
And S5, the terminal location is based on the TDOA algorithm, and the distance difference is measured by measuring the time difference from the mobile terminal to different transmitting ends. By applying the idea of the centroid weighting algorithm, the distance calculation formula of the target object and the LED lamp is assumed as follows:
wherein d iskkIs the distance between the target object and the LED lamp, NiFor the number of LEDs participating in positioning, N is set in the experimenti＝3，(xi，yiH) is the coordinate of the ith LED lamp, (x)kk，ykk0) the coordinates solved for the objective function.
The weighting factor is calculated as follows:
the target object actual coordinate calculation formula is as follows:
where (x, y) are the target object location coordinates.
S6, in the established visible light positioning system, the specific position of a person is identified, positioning and data transmission are realized while illumination is carried out, an indoor model integrating illumination, communication and positioning is realized, a base station model diagram is shown in fig. 7, the model is formed by combining 3 led lamps, each led lamp on the base station can stretch and rotate, and better illumination and positioning effects are realized conveniently.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (5)
1. An indoor positioning method based on LED visible light is characterized by comprising the following steps:
s1, establishing a visible light channel transmission as a line-of-sight transmission model, wherein the indoor moving speed of the target object is negligible relative to the speed of light, the visible light channel is regarded as a quasi-static channel, and the establishment of an equivalent baseband transmission model comprises the following steps:
wherein the content of the first and second substances,
the symbols are convolution symbols, R is the responsivity of the photodetector, x (t) is the optical power of the transmitted signal, h (t) is the impulse response of the channel, and n (t) represents the dominant noise source in the channel;
s2, realizing the initial positioning of the indoor positioning point by combining the signal transmission time of visible light indoor communication through a sensor node positioning algorithm APIT in the wireless sensor network;
s3, adjusting the rotation angle of the LED lamp in the proximity range area according to the initially positioned positioning range information to enable the LED lamp to vertically irradiate the target object; according to the positioning range of the initial positioning, three LED lamps with the nearest distance are selected, the centroid weighting algorithm is applied to the TDOA algorithm to further improve the positioning accuracy, the position estimation coordinates obtained through nonlinear optimization are used as the coordinates of the centroid algorithm, and the weighting factors are used as the constraints of the centroid algorithm, so that the specific positioning of the target object is obtained.
2. The method as claimed in claim 1, wherein the step S1 further includes: a discrete wavelet transform is added in S1 for denoising to improve link performance.
3. The method as claimed in claim 1, wherein the step S2 specifically includes:
s21, obtaining a triangular area through measurement, and recording a linear equation of three sides;
s22, after all triangular areas of the APIT test are obtained, calculating all recorded three-edge intersection points;
and S23, selecting points which can form a minimum polygon from the obtained intersection points, obtaining the minimum polygon, namely the range determined by the initial positioning, and selecting three LED lamps with a short distance range for final positioning.
4. The method for indoor positioning based on LED visible light of claim 1, wherein the step S3 further comprises:
s31, on the basis of the TDOA method, the LEDs are nearest to the target object and are distributed circumferentially, so that the positioning errors of all indoor positions are uniform, and the positioning accuracy is improved;
s32, when the TDOA is used for positioning, the VLC based on the white light LED is used for transmitting the positioning reference information, and the signals sent by the adjacent LEDs can be separated on the target object and interference among the signals can not be caused by adopting carrier allocation, wavelength division multiplexing, time division multiplexing and code division multiplexing.
5. The method as claimed in claim 1, wherein in step S3, the target object coordinates are calculated by the following formula:
wherein d iskkIs the distance between the target object and the LED lamp, NiSetting N for the number of LEDs participating in positioningi＝3，(xi，yiH) is the coordinate of the ith LED lamp, (x)kk，ykk0) the coordinates solved for the objective function; w is a1，w2，w3Is a weighting factor; (x, y) are coordinates of the target object.
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| CN112698339A (en) * | 2020-12-31 | 2021-04-23 | 中国人民解放军战略支援部队信息工程大学 | Target detection method, device and system |
| CN113783619A (en) * | 2021-09-17 | 2021-12-10 | 深圳大学 | Optimization method based on fusion of visible light communication and visible light positioning |
| WO2023039827A1 (en) * | 2021-09-17 | 2023-03-23 | 深圳大学 | Optimization method based on fusion of visible light communication and visible light positioning |
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