A fusion positioning method based on a Beidou pseudolite

Abstract

The application discloses a fusion positioning method based on a Beidou pseudolite, and aims at a one-dimensional positioning problem in a shielding environment such as an indoor corridor, an underground pipe gallery and a railway tunnel, and adopts a positioning method of fusing a pseudolite and inertial navigation. Firstly, a positioning area is divided into multiple linear positioning sub-areas, pseudolites are erected at two ends of each sub-area, carrier phase and pseudorange values are measured by a receiver, a pseudorange difference value between the pseudolites is corrected by using the carrier phase, pseudorange differential positioning is carried out, a positioning point of the receiver at a previous time and a current time is calculated, a distance between the positioning points is compared with a distance calculated by inertial navigation, and within a fluctuation range of a pseudorange error, an optimal correction value of the pseudorange is searched, and a corresponding pseudorange differential positioning result is the final positioning result.

Description

Technical Field

[0001] The present invention relates to the field of personnel and vehicle safety monitoring and intelligent transportation in shielded environments such as indoor corridors, underground pipe corridors, and railway tunnels, and specifically to a fusion positioning method based on Beidou pseudo-satellites. Background Art

[0002] With the maturity of various indoor positioning technologies, people begin to hope to apply relevant indoor positioning technologies to narrow and long sheltered environments such as railway tunnels, highway tunnels, and underground pipeline corridors to achieve positioning, monitoring and management of personnel and vehicles. At present, mainstream indoor positioning technologies mainly include Bluetooth positioning, WIFI positioning, ultra-wideband positioning and other technologies. Although they have solved certain indoor positioning problems, they still have certain limitations. First, the positioning accuracy of Bluetooth and WIFI positioning technologies is limited, and ultra-wideband is expensive and has limited coverage.

[0003] Currently, the Beidou navigation and positioning system can achieve high-precision positioning of pedestrians in outdoor environments. Pseudo-satellites use the same positioning technology, broadcasting Beidou-like navigation signals in shielded environments such as indoors and underground. Receivers measure the distance between the user and the pseudo-satellite to achieve positioning. Furthermore, pseudo-satellite signals have a wide coverage range, reducing equipment deployment. For narrow and long environments like tunnels and utility corridors, directional antennas can be used to radiate pseudo-satellite signals along the tunnel, reducing signal reflections from the tunnel walls and improving ranging accuracy. Therefore, a fused positioning method based on Beidou pseudo-satellites is proposed to address one-dimensional positioning issues in shielded environments such as underground utility corridors and railway tunnels. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a Beidou pseudo-satellite fusion positioning method, which adopts the pseudo-satellite + inertial navigation fusion positioning method to solve the one-dimensional positioning problem in narrow and long shielded environments such as tunnels, pipe corridors, and corridors, and realize the positioning control of personnel and vehicles in tunnels, pipe corridors, and corridors.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A fusion positioning method based on Beidou pseudolites includes the following steps:

[0007] (1) The positioning area is divided into multiple linear positioning sub-areas. Two pseudolites are set up at both ends of the positioning sub-areas, namely pseudolites 1 and 2. Pseudolites 1 and 2 transmit navigation signals respectively. The navigation signal power is adjusted so that the navigation signal covers the entire positioning sub-area. The coordinates of the pseudolites are calibrated using a total station.

[0008] (2) The receiver is fixed at a known point to receive navigation signals and measure the pseudoranges of the pseudolites at both ends. The clock error between the pseudolites and the receiver is eliminated by subtracting the pseudoranges. The actual distance difference from the known point to the two pseudolites' transmitting antennas is then used to calculate the clock error between the pseudolites and compensate for the pseudorange difference.

[0009] (3) Assemble the receiver and the inertial navigation system on the same carrier. When the carrier is not moving, calculate the initial coordinates of the carrier using the pseudo-range difference after compensation between the pseudo-satellites; the motion trajectory of the carrier is on the line connecting the ground projections of the pseudo-satellites at both ends;

[0010] (4) After the carrier moves, the inertial navigation is used to calculate the distance the carrier has moved at the current moment relative to the previous moment. At the same time, within the pseudo-range measurement error range, the carrier phase measured by the receiver is used to correct the compensated pseudo-range difference;

[0011] (5) Based on the corrected pseudo-range difference, the coordinate point of the carrier is calculated, the distance between the two coordinate points at the previous moment and the current moment is obtained, and the difference between the distance and the inertial navigation distance is calculated. When the difference is the smallest, the two calculated coordinate points are the positions of the carrier at the two moments.

[0012] Furthermore, step (2) specifically includes the following steps:

[0013] (201) The receiver is fixed at a known point to receive the navigation signal, and the pseudorange observations ρ1 and ρ2 from the receiver to pseudolite 1 and pseudolite 2 are obtained and difference processing is performed. The formula is as follows:

[0014] Δρ 2,1 =ρ2-ρ1 (1)

[0015] Based on the pseudorange observation equation, formula (1) can be further written as:

[0016]

[0017] Where: Δρ 2,1 is the pseudo-range difference from the receiver to the transmitting antennas at both ends; and is the true distance from the receiver to pseudolite 1 and pseudolite 2; δt u is the clock deviation between the receiver and GPS; δt 2 and δt 1 are the clock deviations between pseudolite 2 and pseudolite 1 and GPS respectively; c is the speed of light, ε ρ is other errors;

[0018] From formula (2), we can see that when the two pseudorange observations are subtracted, the clock bias between the receiver and GPS and other errors can be eliminated, leaving only the clock bias between the pseudo-satellites (δt 2 -δt1 );

[0019] (202) According to the known point coordinates A(X a ,Y a ,Z a ), calculate the actual distance from the receiver to pseudolite 1 and pseudolite 2, where the coordinates of pseudolite 1 (X1, Y1, Z1) and pseudolite 2 (X2, Y2, Z2) have been calibrated in step (1), so the formula (2) for:

[0020]

[0021] (203) According to formula (2) and formula (3), the compensation value ρ of the pseudo-range difference between pseudo-satellites is calculated c =ΔL-Δρ 2,1 .

[0022] Furthermore, the specific process of calculating the initial coordinates of the carrier in step (3) is as follows:

[0023] A coordinate system is established with the line connecting the ground projections of the two pseudolites as the X-axis and the perpendicular as the Y-axis. Pseudolite 1, pseudolitite 2, and the carrier have the same Y-axis coordinates. The coordinates of the carrier at the initial moment are assumed to be (x0, y0, z0), where the height z0 is a fixed value H. The carrier coordinates are calculated as follows:

[0024]

[0025] in, is the pseudorange difference between pseudolite 2 and pseudolite 1 at the initial moment. By solving the above formula, x0 is obtained, and the coordinates of the carrier at the initial moment are obtained.

[0026] Furthermore, the specific steps of step (4) are as follows:

[0027] (401) After the carrier moves, the moving distance of the carrier at the current moment i compared to the moment i-1 is calculated based on the motion state of the carrier at the previous moment i-1 by using the inertial navigation one-dimensional track recursion.

[0028] Where S is the distance the carrier moves, a is the acceleration of the carrier, and υ0 is the velocity of the carrier at time i-1;

[0029] (402) According to the receiver's tracking accuracy of the C / A code phase, the pseudo-range difference between pseudo-satellites is no greater than the set threshold value A. At the same time, the carrier phase measurement accuracy is much greater than the pseudo-range measurement accuracy. Therefore, the carrier phase measured by the receiver is used to correct the compensated pseudo-range difference. The calculation formula is as follows:

[0030]

[0031] Among them, N i is the integer cycle of the carrier phase at time i, λ is the wavelength of the navigation signal, is the pseudorange difference between pseudolite 2 and pseudolite 1 at time i, is the fractional part of the carrier phase difference between pseudolite 2 and pseudolite 1 at time i;

[0032] (403) According to the formula Calculate N i All values ​​of n i , and then obtain the corresponding corrected pseudorange difference

[0033] Furthermore, the specific steps of step (5) are as follows:

[0034] (501) According to the formula Calculate the coordinate point P at time i-1 and i i-1 and P i ;

[0035] (52) Let ΔP = ||P i -P i-1 ||, among all the values ​​of ΔP, when the value of |ΔP-S| is the smallest, the coordinate obtained at time i is the position of the current carrier.

[0036] The advantages of the present invention compared to the prior art are:

[0037] The mainstream technologies for positioning personnel and vehicles in narrow and long shielded environments include Bluetooth positioning technology and ultra-wideband positioning technology. However, since Bluetooth positioning technology mostly uses fingerprint positioning or RSSI technology, the workload of fingerprint collection in the early stage of fingerprint positioning is large, and the fingerprint will change due to environmental influences, and the positioning is unstable. The positioning accuracy of RSSI technology is often only about 2m. The technology in the present invention can achieve higher-precision positioning by utilizing the fusion of pseudo-satellite and inertial navigation. For ultra-wideband positioning technology, bidirectional ranging is used to transmit and receive. Although it can achieve high-precision positioning, it cannot locate high-speed targets. Pseudo-satellite positioning uses passive positioning, which is not restricted by high-speed targets and can still achieve positioning. Overall, the method of using pseudo-satellite plus inertial navigation fusion can achieve high-precision location services while meeting the needs of personnel and vehicle positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a principle block diagram of the present invention.

[0039] Figure 2 Flowchart of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further explained below with reference to the accompanying drawings.

[0041] like Figure 1 and Figure 2 As shown, a fusion positioning method based on Beidou pseudo-satellite includes the following steps:

[0042] (1) The positioning area is divided into multiple linear positioning sub-areas. Pseudolite 1 and pseudolite 2 are respectively set up at both ends of the positioning sub-area to transmit navigation signals. The navigation signal power is adjusted so that the pseudolite navigation signal can cover the entire positioning sub-area. The coordinates of the pseudolite are calibrated by a total station, and the coordinates (X1, Y1, Z1) and (X2, Y2, Z2) of pseudolite 1 and pseudolite 2 are recorded for subsequent receiver positioning.

[0043] (2) The receiver is fixed on a known point A, receives the pseudo-satellite navigation signal, and measures the pseudo-range to the pseudo-satellites at both ends. Due to the existence of pseudo-satellite clock errors and the clock error between the pseudo-satellite and the receiver, the measured pseudo-range contains errors. The clock error between the pseudo-satellite and the receiver is eliminated by pseudo-range difference. The actual distance difference from the known point to the two transmitting antennas is used to further calculate the clock error between the pseudo-satellites, which is used to compensate for the difference between the pseudo-ranges in the subsequent positioning process.

[0044] The specific steps are as follows:

[0045] (201) The receiver is fixed at a known point to receive the navigation signal, and the pseudorange observations ρ1 and ρ2 from the receiver to pseudolite 1 and pseudolite 2 are obtained and difference processing is performed. The formula is as follows:

[0046] Δρ 2,1 =ρ2-ρ1 (1)

[0047] Based on the pseudorange observation equation, formula (1) can be further written as:

[0048]

[0049] Where: Δρ 2,1 is the pseudo-range difference from the receiver to the transmitting antennas at both ends; and is the true distance from the receiver to pseudolite 1 and pseudolite 2; δt u is the clock deviation between the receiver and GPS; δt 2 and δt 1 are the clock deviations between pseudolite 2 and pseudolite 1 and GPS respectively; c is the speed of light, ε ρ is other errors;

[0050] From formula (2), we can see that when the two pseudorange observations are subtracted, the clock bias between the receiver and GPS and other errors can be eliminated, leaving only the clock bias between the pseudo-satellites (δt 2 -δt 1);

[0051] (202) According to the known point coordinates A(X a ,Y a ,Z a ), calculate the actual distance from the receiver to pseudolite 1 and pseudolite 2, where the coordinates of pseudolite 1 (X1, Y1, Z1) and pseudolite 2 (X2, Y2, Z2) have been calibrated in step (1), so the formula (2) for:

[0052]

[0053] (203) According to formula (2) and formula (3), the compensation value ρ of the pseudo-range difference between pseudo-satellites is calculated c =ΔL-Δρ 2,1 , that is, the error of the pseudorange difference caused by the clock difference between pseudosatellites.

[0054] (3) The receiver and the inertial navigation system are assembled on the same carrier. When the carrier does not move, the initial coordinates of the carrier are calculated using the pseudo-range difference between the pseudo-satellites (after compensation). The motion trajectory points of the carrier are considered to be on the line connecting the ground projections of the pseudo-satellites at both ends.

[0055] The specific process of calculating the initial coordinates of the carrier is as follows:

[0056] A coordinate system is established with the line connecting the ground projections of the two pseudolites as the X-axis and the perpendicular line as the Y-axis. Pseudolite 1, pseudolitite 2, and the carrier have the same Y-axis coordinates. The coordinates of the carrier at the initial moment are assumed to be (x0, y0, z0), where the height z0 is a fixed value H. The carrier coordinates are calculated as follows:

[0057]

[0058] in, is the pseudorange difference between pseudolite 2 and pseudolite 1 at the initial moment. By solving x0 in the above formula, the coordinates of the carrier at the initial moment can be obtained.

[0059] (4) After the carrier moves, the inertial navigation is used to calculate the distance the carrier has moved at the current moment relative to the previous moment; at the same time, within the pseudo-range measurement error range, the carrier phase measured by the receiver is used to correct the compensated pseudo-range difference.

[0060] The specific steps are as follows:

[0061] (401) After the carrier moves, the moving distance of the carrier at the current moment i compared to the moment i-1 is calculated based on the motion state of the carrier at the previous moment i-1 by using the inertial navigation one-dimensional track recursion.

[0062] Where S is the distance the carrier moves, a is the acceleration of the carrier, and υ0 is the velocity of the carrier at time i-1.

[0063] (402) According to the receiver's tracking accuracy of the C / A code phase, the measurement error of the pseudorange is about 0.3m. Therefore, the measurement error of the pseudorange difference between pseudosatellites is about 0.6m. The measurement accuracy of the carrier phase is about 1mm. The calculation formula for correcting the pseudorange difference by the carrier phase is as follows:

[0064]

[0065] Among them, N i is the integer cycle of the carrier phase at time i, λ is the wavelength of the pseudo-satellite navigation signal, is the pseudorange difference between pseudolite 2 and pseudolite 1 at time i, is the fractional part of the carrier phase difference between pseudolite 2 and pseudolite 1 at time i.

[0066] (403) According to the formula Calculate N i All values ​​of n i , and then obtain the corresponding corrected pseudorange

[0067] (5) Based on the corrected pseudo-range difference, the coordinate point of the carrier is calculated, and then the distance between the two coordinate points at the current moment and the previous moment is obtained. The difference between the distance calculated by the inertial navigation is calculated. When the difference is the smallest, the two calculated coordinate points are the positions of the carrier at the two moments.

[0068] The specific steps are as follows:

[0069] (501) According to the formula Calculate the coordinate point P at time i-1 and i i-1 and P i .

[0070] (502) Let ΔP = ||P i -P i-1 ||, among all the values ​​of ΔP, when the value of |ΔP-S| is the smallest, the coordinate obtained at time i is the position of the current carrier.

Claims

1. A fusion positioning method based on BeiDou pseudo-satellite, characterized in that: The steps include: (1) The positioning area is divided into multiple linear positioning sub-areas. Two pseudolites are set up at both ends of the positioning sub-areas, namely pseudolites 1 and 2. Pseudolites 1 and 2 transmit navigation signals respectively. The navigation signal power is adjusted so that the navigation signal covers the entire positioning sub-area. The coordinates of the pseudolites are calibrated using a total station. (2) The receiver is fixed at a known point to receive navigation signals and measure the pseudoranges of the pseudolites at both ends. The clock error between the pseudolites and the receiver is eliminated by subtracting the pseudoranges. The actual distance difference from the known point to the two pseudolites' transmitting antennas is then used to calculate the clock error between the pseudolites and compensate for the pseudorange difference. (3) Assemble the receiver and the inertial navigation system on the same carrier. When the carrier is not moving, calculate the initial coordinates of the carrier using the pseudo-range difference after compensation between the pseudo-satellites; the motion trajectory of the carrier is on the line connecting the ground projections of the pseudo-satellites at both ends; (4) After the carrier moves, the inertial navigation is used to calculate the distance the carrier has moved at the current moment relative to the previous moment. At the same time, within the pseudo-range measurement error range, the carrier phase measured by the receiver is used to correct the compensated pseudo-range difference; (5) Based on the corrected pseudo-range difference, the coordinate point of the carrier is calculated, the distance between the two coordinate points at the previous moment and the current moment is obtained, and the difference between the distance and the inertial navigation distance is calculated. When the difference is the smallest, the two calculated coordinate points are the positions of the carrier at the two moments.

2. The method for fusion positioning based on BeiDou pseudolites according to claim 1, characterized in that: Step (2) specifically includes the following steps: (201) The receiver is fixed at a known point to receive the navigation signal, and the pseudorange observations ρ1 and ρ2 from the receiver to pseudolite 1 and pseudolite 2 are obtained and difference processing is performed. The formula is as follows: Dr. 2,1 =ρ2-ρ1 (1) Based on the pseudorange observation equation, formula (1) can be further written as: Where: Δρ 2,1 is the pseudo-range difference from the receiver to the transmitting antennas at both ends; and is the true distance from the receiver to pseudolite 1 and pseudolite 2; δt u is the clock deviation between the receiver and GPS; δt 2 and δt 1 are the clock deviations between pseudolite 2 and pseudolite 1 and GPS respectively; c is the speed of light, ε ρ is other errors; From formula (2), we can see that when the two pseudorange observations are subtracted, the clock bias between the receiver and GPS and other errors can be eliminated, leaving only the clock bias between the pseudo-satellites (δt 2 -δt 1 ); (202) According to the known point coordinates A(X a ,Y a ,Z a ), calculate the actual distance from the receiver to pseudolite 1 and pseudolite 2, where the coordinates of pseudolite 1 (X1, Y1, Z1) and pseudolite 2 (X2, Y2, Z2) have been calibrated in step (1), so the formula (2) for: (203) According to formula (2) and formula (3), the compensation value ρ of the pseudo-range difference between pseudo-satellites is calculated c =ΔL-Δρ 2,1 .

3. The fusion positioning method based on BeiDou pseudolites according to claim 2, characterized in that: The specific process of calculating the initial coordinates of the carrier in step (3) is as follows: A coordinate system is established with the line connecting the ground projections of the two pseudolites as the X-axis and the perpendicular as the Y-axis. Pseudolite 1, pseudolitite 2, and the carrier have the same Y-axis coordinates. The coordinates of the carrier at the initial moment are assumed to be (x0, y0, z0), where the height z0 is a fixed value H. The carrier coordinates are calculated as follows: in, is the pseudorange difference between pseudolite 2 and pseudolite 1 at the initial moment. By solving the above formula, x0 is obtained, and the coordinates of the carrier at the initial moment are obtained.

4. The method for fusion positioning based on BeiDou pseudolites according to claim 3, characterized in that: The specific steps of step (4) are as follows: (401) After the carrier moves, the moving distance of the carrier at the current moment i compared to the moment i-1 is calculated based on the motion state of the carrier at the previous moment i-1 by using the inertial navigation one-dimensional track recursion. Where S is the distance the carrier moves, a is the acceleration of the carrier, and υ0 is the velocity of the carrier at time i-1; (402) According to the receiver's tracking accuracy of the C / A code phase, the pseudo-range difference between pseudo-satellites is no greater than the set threshold value A. At the same time, the carrier phase measurement accuracy is much greater than the pseudo-range measurement accuracy. Therefore, the carrier phase measured by the receiver is used to correct the compensated pseudo-range difference. The calculation formula is as follows: Among them, N i is the integer cycle of the carrier phase at time i, λ is the wavelength of the navigation signal, is the pseudorange difference between pseudolite 2 and pseudolite 1 at time i, is the fractional part of the carrier phase difference between pseudolite 2 and pseudolite 1 at time i; (403) According to the formula Calculate N i All values ​​of n i , and then obtain the corresponding corrected pseudorange difference 5. The method for fusion positioning based on BeiDou pseudolites according to claim 4, characterized in that: The specific steps of step (5) are as follows: (501) According to the formula Calculate the coordinate point P at time i-1 and i i-1 and P i ; (52) Let ΔP = ||P i -P i-1 ||, among all the values ​​of ΔP, when the value of |ΔP-S| is the smallest, the coordinate obtained at time i is the position of the current carrier.

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