KR100421802B1 - Precise calibration of pseudolite antenna positions for indoor navigation system - Google Patents

Abstract

The present invention relates to precisely measuring the position of the pseudo-satellite signal transmitting antenna for indoor navigation. In particular, the most efficient minimum measurement point is selected according to the reference station and the pseudo-satellite arrangement, and the pseudo-satellite signal is measured therein. The exact position of the pseudo satellite transmitting antenna is calculated. Recently, as part of a method of using a GPS system indoors, research on the construction of an indoor navigation system using Pseudolite has been actively conducted in various fields, and is in the preparation stage for practical use. One of the factors affecting the performance of the indoor navigation system using the pseudo satellite is the position measurement accuracy of the pseudo satellite signal transmitting antenna. Therefore, accurately measuring the position of the pseudo satellite transmitting antenna is a key technology in commercializing the indoor navigation system using the pseudo satellite. In particular, since the method of the present invention uses the transmit signal of the pseudo satellite, it is advantageous in that the phase center of the antenna can be measured relatively accurately, which is impossible in the conventional method using a tape measure or other geometrical tool. As a result of calculating pseudo-satellite position measurement error through simulation, it was confirmed that it can be measured with accuracy within 1 ~ 2cm.

Description

Precise calibration of pseudolite antenna positions for indoor navigation system

The present invention relates to a method for precisely determining the position of a pseudo satellite signal transmitting antenna that influences the performance of an indoor navigation system constructed using pseudo satellites. The present invention relates to a method of accurately calculating and determining the position of a pseudo satellite signal transmitting antenna based on a pseudo satellite signal measured therein.

Recently, as part of the method of using the Global Positioning System (GPS) indoors, researches on the construction of indoor navigation systems using pseudo satellites have been actively conducted, and various fields have already been prepared for practical use. Are on stage. The performance of indoor navigation system using this pseudo satellite depends on several factors, one of which is the positioning accuracy of the pseudo satellite signal transmitting antenna. Therefore, accurately measuring the position of the pseudo satellite signal transmitting antenna is a key technology in commercializing the indoor navigation system using the pseudo satellite. Conventionally, in measuring the position of the pseudo-satellite signal transmitting antenna, a tape measure or other geometric tool is used. In this method, it is difficult to accurately measure the phase center of the antenna.

Accordingly, the technical problem of the present invention is to provide a method for determining the position of a pseudo-satellite signal transmitting antenna using only a signal transmitted from a pseudo-satellite for indoor navigation without using a tape measure or other geometric measurement tool.

Another technical problem of the present invention is to provide a method for efficiently determining the position of a pseudo satellite signal transmitting antenna while minimizing a measurement error for a given reference station and pseudo satellite arrangement.

1 is a schematic configuration diagram of an indoor navigation system to which a positioning method of a signal transmitting antenna of the present invention is applied;

FIG. 2 is a diagram to illustrate measurements used in the system of FIG. 1; FIG.

3 is a flowchart illustrating a process of determining a phase center of a pseudo-satellite signal transmitting antenna using a dual differential carrier phase;

4a and 4b show the positions of the measuring points optimized under each constraint;

5 is a view showing the change of the optimum measurement point arrangement according to the position of the reference station;

6 is a flowchart illustrating an algorithm for calculating the position of a pseudo satellite and an unknown carrier phase unknown using a bi-differential carrier phase measurement;

7 is a diagram showing measurement point arrangement for pseudosatellite position measurement performance comparison analysis; And

FIG. 8 is a graph obtained by simulation of pseudo-satellite position measurement error in the measurement point arrangement shown in FIG. 7.

In order to solve the above technical problems, the method of positioning a signal transmitting antenna according to the present invention may include at least three or more pseudo-satellites generating the same signal as the GPS L1 C / A code and each having an antenna transmitting the signal. And a reference station for receiving the pseudo-satellite signal and generating correction information, a user receiving the pseudo-satellite signal and correction information to obtain its position, and a center for displaying the user's position by combining the information. A method for determining the position of the signal transmitting antenna in an indoor navigation system including a processing device, wherein the position of the pseudo satellite transmitting antenna is approximately several meters in position for arranging pseudolites and improving convergence of a mathematical algorithm. Within the initial position Assuming a position of the reference station at a fixed position of the base; Measurement point to minimize the location measurement error Placement of Pseudosatellite Covariance Matrices Using Mathematics Programs Performance index to minimize Determining through the step, where, , , , , , , Also, Is the location of the i pseudolite, Is the location of the reference station, Is your location, Is the line of sight to the satellite, Is the clock error of the receiver, Is the clock error of pseudo-satellite, Is an unknown constant of the carrier phase, Is the noise of the receiver, Is the standard deviation of the carrier phase measurement noise; Place the user at, and simultaneously measure the pseudo-satellite carrier phases at the user and the reference station, Estimate of least-squares estimation error using Position of Pseudo Satellite Signaling Antenna by Calculating a convergence value of the antenna position calculation value; It characterized by comprising the step of judging by the equation.

If the antenna position calculation value does not converge in the step of determining whether the antenna position calculation value is converged, the antenna position calculation is performed by a pseudo satellite rearrangement step of replacing the hypothetical position of the pseudo satellite position with the calculated pseudo satellite position. It is preferable to go through it again until the value converges.

At this time, the pseudo satellites do not need to be synchronized.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

On the other hand, throughout the description of this embodiment, the position of the pseudo satellite refers to the phase center of the pseudo satellite signal transmitting antenna.

1 is a schematic configuration diagram of an indoor navigation system to which a positioning method of a signal transmitting antenna of the present invention is applied. Referring to FIG. 1, six pseudo satellites 100a to 100f are arranged at various heights. The reference station 110 is located on the bottom surface, and the user 120 moves along the five measurement points around it. Each satellite generates the same signal as the GPS L1 C / A code and is not synchronized with each other. The reference station 110 is equipped with a GPS receiver equipped with a program modified for an indoor navigation system and a computer which can perform various calculations. In this case, the same signal as the GPS L1 C / A code means "a quasi-random number of 1 with L1 = 1575.52 MHz, which is one of two L-Band frequencies in a radio frequency (RF) region where a GPS satellite normally transmits. Signal modulated with Coarse / Acquisition (C / A) -code consisting of pseudo-random binary code.

FIG. 2 is a diagram to illustrate measurements used in the system of FIG. 1.

Referring to FIG. 2, signal transmitting antennas 100a 'and 100b' are shown in place of pseudo satellites.

Carrier phase measurements shown in FIG. 2 may be represented by Equation 1 below.

here, Is the location of the i pseudolite, Is the location of the reference station, Is your location, Is the line of sight vector to the satellite, B is the clock error of the receiver, Is the clock error of pseudo-satellite, Is an unknown constant of the carrier phase, Is the noise of the receiver.

The single differential measurement for the carrier phase equations of Equation 1 is defined as Equation 2.

When the carrier phase equations of Equation 1 are doubled between the user and the reference station, the i th pseudo satellite and the j th pseudo satellite, the following Equation 3 is obtained.

In other words, when the carrier phase between the pseudo-satellites is differentiated, the clock error of the receiver is eliminated, and when the double difference between the user and the reference station is eliminated, the clock error of the pseudo-satellite is eliminated.

The process of determining the phase center of the pseudo-satellite signal transmitting antenna using the dual differential carrier phase is shown in the flowchart of FIG. 3. Referring to FIG. 3, first, a pseudo satellite group for an indoor navigation system is disposed (S310). Subsequently, an initial position of the pseudo satellite group is assumed (S320). Next, for the given reference station's position and the assumed pseudo-satellite group, the arrangement of measurement points that can minimize the positioning error is determined through an optimization performance index that minimizes the pseudo-satellite positioning covariance matrix (S330). ). The step S330 will be described later in more detail. Once the optimal measurement point is determined, the pseudo-satellite carrier phases are simultaneously measured and recorded by the reference station, and then the phase center of the pseudo-satellite signal transmitting antenna is calculated by calculating the least-squares estimation error using the dual difference equation (S340). ). The step S340 will also be described in more detail later. Subsequently, it is determined whether or not convergence is calculated by calculating a difference between the position of the pseudo satellite obtained in step S340 and the position of the pseudo satellite initially assumed. If it has not converged, the initial hypothesis of the pseudo satellite is replaced with the calculated pseudo satellite position (S370), and the steps S320 to S350 are repeated until convergence. In the case of a convergence result in step S350, the value is determined as the phase center of the pseudo-satellite signal transmission antenna (S360). As a result of the simulation, even if the step S370 is repeated, it is found that about 2 to 3 times are sufficient convergence. In positioning the signal transmitting antenna according to the present invention, it should be noted that the departure starts from the following premise.

First, the reference station is fixed and its location is known exactly. Secondly, the position of each measuring point is known exactly and exists within a certain range. Third, in the pseudo-satellite carrier phase measurement for measuring the position of the pseudo-satellite, the GPS receiver does not continuously perform the pseudo-satellite carrier phase measurement but does not occur in the middle, that is, cycle slippage is not generated.

As described above, an important algorithm in signal transmission antenna positioning according to the present invention is to obtain an optimized measurement point arrangement that minimizes pseudo-satellite positioning errors according to the arrangement of a given reference station and the satellite group (step S330) and By using the carrier phase measurements collected at the reference station and each measurement point, the phase center and the carrier phase unknown of the pseudo satellite transmitting antenna can be divided into steps (step S340), each of which will be described in detail below.

[Measurement Point Placement Optimization Algorithm]

The placement of the measuring points to minimize the positioning error of the pseudosatellite depends on the geometrical arrangement of the reference station and the pseudosatellite group. This is because noise is mixed in the carrier phase, the signal transmitted from the pseudo-satellite, which is often assumed to be white noise. In other words, an optimal measurement point means a set of measurement points that "minimize the pseudopositional positioning covariance matrix".

A pseudosatellite positioning covariance matrix for determining pseudo satellite positioning accuracy is calculated as in Equation 4 below. That is, Equation 4 expresses all the dual differential carrier phase measurements for calculating the pseudo-satellite position in one determinant form.

here, to be.

Since Equation 4 is a nonlinear function of the reference station and each pseudo-satellite position, it is linearized as shown in Equation 5 based on the position of the given reference station and the assumed pseudo-satellite to simplify the calculation.

Equation 5 may be redefined as in Equation 6.

Then, the linearized pseudolite positioning covariance matrix is calculated as shown in Equation (7).

here, ego,

, to be.

Then, the optimization performance index is expressed by Equation 8.

In addition, since the navigation system is configured indoors, there is a constraint that the position of the measurement point must be within a certain range. Thus, it ultimately results in an optimization problem with constraints.

Computer simulations were performed to see what results the algorithm gave. The configuration of the indoor navigation system used in the simulation was as shown in FIG. 1, and the phase center positions of the pseudo satellite signal transmitting antennas are shown in Table 1.

Pseudo-satellite number X (m) Y (m) Z (m) One -5.0 -5.0 +2.5 2 0.0 -5.0 +2.0 3 +5.0 -5.0 +2.5 4 +5.0 +5.0 +2.5 5 0.0 +5.0 +2.0 6 -5.0 +5.0 +2.5

In addition, the position limitation of the measurement point used as a constraint in the optimization is shown in Equation (9). In this simulation, it is assumed that the measuring points are all at the bottom, and the reference station is located at the origin.

At this time, the noise characteristics of the pseudo-satellite carrier phase are characteristic values of typical GPS receivers. Was 2 mm. As a result, the results as shown in Figs. 4A and 4B were obtained for the case of using five measuring points and six measuring points. 4A and 4B, the central black square represents the reference station, the hollow circle is pseudosatellite, and the black circle represents the position of the optimized measuring point under each constraint.

In the case of using five measuring points, the arrangement of the measuring points symmetrically shifting the result of FIG. 4A with respect to the X axis also gives a minimum covariance matrix value, so there are two optimized measuring point arrangements. These results indicate that the position of the pseudo satellite and the reference station are both symmetric with respect to the origin, because the pseudo-satellite position measurement error covariance matrix values are symmetric with respect to the origin. In particular, in case of 6 points, complete origin symmetry results are given.

In order to analyze how the position of the reference station affects the position of the optimized measuring point, the position of the optimized measuring point was calculated while moving the position of the reference station placed at the origin as shown in FIG. 5. When five measuring points are used, it can be seen that as the reference station moves up from the center, the measuring point also rises as indicated by the arrow. In other words, it can be seen that the position of the reference station also affects the optimum measurement point arrangement. Therefore, if the reference station is not located at the origin, intuitive positioning of the optimal measuring point using symmetry or the like is not known. From this, the usefulness of the method of the present invention can be seen.

[Pseudosatellite Positioning Algorithm]

An algorithm for calculating the position of the pseudolite and an unknown carrier phase unknown using a dual differential carrier phase measurement is shown in the flowchart of FIG. 6.

Referring to FIG. 6, first, a carrier phase double difference measurement value of a reference station and a measurement gain is collected (S3410). Subsequently, the pseudo-satellite position x ₀ and the carrier phase unknown constant are estimated (S3412). Next, the nonlinear least-squares estimation calculation form is changed using Equation 10 below (S3414).

Next, the least squares estimation error δx ₀ is calculated by using Equation 11 (S3416).

When the estimation error is calculated, it is determined whether the error converges (S3418). At this time, if the error does not converge, the pseudo-satellite position is updated using Equation 12 (S3420).

If the error converges, a real carrier phase unknown constant is obtained at the estimated pseudo-satellite position (S3422). Then, the unknown integer term is removed from the pseudo-satellite position while the carrier phase unknown constant is integerized (S3424). Subsequently, based on this result, the pseudolite position is recalculated in the same manner as above (S3426). The pseudo-satellite position calculation is completed by recalculation (S3428).

The observation matrix used for calculating the position of the pseudo satellite is generated as follows.

Equation 13 is obtained by double-differentiating the carrier phases measured in the i-th pseudolite and the j-th pseudosatellite.

here, to be.

By double-differentiating all pseudo-satellite carrier phase measurements measured at one measurement time (1-epoch), the matrix of Equation 14 can be made.

Here, each parameter is defined as in Equation 15.

here, Is, to be.

Collecting this for all measured times (k epochs) is shown in Equation 16 below.

Here, in order to accurately measure the position of the pseudo satellite, the observation matrix should be made full-rank, which should satisfy the relationship as shown in Equation 17.

Where k is the number of epochs and m is the number of pseudosatellites.

Therefore, in order to accurately measure the positions of six pseudolites, the pseudosatellite carrier phase measurements must be collected at at least five measurement points.

In order to verify the effect of the method of the present invention, the following simulation was performed. That is, the degree of improvement of pseudosatellite positioning error in the case of using optimally arranged measuring points and in the case of using arbitrary measuring points was compared with the case of using 5 measuring points and 6 measuring points, respectively. 7 shows the arrangement of the measurement points in the four cases.

In order to ensure the accuracy of the performance comparison, the results of performing 100 times using different pseudo-satellite carrier phase noise components in each simulation are shown in FIG. 8.

In addition, the specific numerical value is put together in Table 2.

Measuring point placement Total pseudo-satellite position error (RMS) 5 points optimized 0.0144m Intuitive 5 points 0.0214m 6 points optimized 0.0104m Intuitive 6 points 0.0123m

The present invention has proposed a method for accurately measuring the position of a pseudo satellite signal transmitting antenna that influences the accuracy of an indoor navigation system constructed using a pseudo satellite. In particular, the method of the present invention uses carrier phase information, which is a signal transmitted from a pseudo-satellite, to accurately measure an antenna phase center that is difficult to measure when using a tape measure or other geometric surveying tools. Therefore, it will contribute greatly to the performance improvement of indoor navigation system using pseudo satellite. In addition, by providing a method of minimizing the positioning error of the pseudo satellite at the minimum measurement point, it is possible to measure the position of the pseudo satellite for indoor navigation in a more economical and efficient manner.

Claims (3)

At least three or more pseudo-satellites which generate the same signal as the GPS L1 C / A code, each having an antenna for transmitting the signal, a reference station for receiving the pseudo-satellite signal and generating correction information; Determining a position of the signal transmitting antenna in an indoor navigation system including a user receiving a pseudo-satellite signal and correction information to obtain its position, and a central processing unit displaying the user's position by combining the information. In the method, In order to locate pseudo-satellites and improve the convergence of mathematical algorithms, the position of the pseudo-satellite transmitting antenna is measured within a few meters by using an eye measurement and its initial position. Assuming; The location of the reference station in the stationary position Measurement point to minimize the location measurement error Placement of Pseudosatellite Covariance Matrices Using Mathematics Programs Performance index to minimize To determine through Where, , , , , , , , Also, here Is the location of the i pseudolite, Is the location of the reference station, Is your location, Is the line of sight to the satellite, Is the clock error of the receiver, Is the clock error of pseudo-satellite, Is an unknown constant of the carrier phase, Is the noise of the receiver, Is the standard deviation of carrier phase measurement noise; The optimized measuring point Place the user at, and simultaneously measure the phases of the pseudo-satellite carriers at the user and the reference station, Estimate of least-squares estimation error using Position of Pseudo Satellite Signaling Antenna by Calculating a; Whether the antenna position calculation value converges Positioning method of the signal transmitting antenna, characterized in that it comprises the step of determining by the equation. The pseudo-satellite rearrangement method of claim 1, wherein when the antenna position calculation value does not converge in the step of determining whether the antenna position calculation value is converged, a pseudo-satellite rearrangement is substituted for the hypothesis of the initial position of the pseudo-satellite with the calculated pseudo-satellite position. And repeating the above steps until convergence of the antenna position calculation value. The method of claim 1, wherein the pseudolites are not synchronized.