JP2007248345A - Positioning method and positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device capable of acquiring a result of independent positioning in a shorter time. <P>SOLUTION: A positioning method for positioning the position of the positioning device 10 receiving a radio wave based on a propagation time of the radio wave transmitted from a plurality of satellites Si is characterized as follows: each position of a prescribed number of satellites whose orbits are known is calculated only once (S1); a pseudo-distance based on a temporary arrival time of the radio wave from the satellite position is calculated (S3); the position of the positioning device is positioned by an independent positioning method by using the pseudo-distance (S4); and when a timepiece error of the positioning device is over a prescribed value as the result of the independent positioning (S5), the independent positioning is repeated after correcting the pseudo-distance as much as the timepiece error (S4). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a positioning method and a positioning device that receive radio waves from satellites, and more particularly to a positioning method and a positioning device that receive radio waves from a plurality of satellites and perform positioning based on the propagation time of radio waves.

  There is known a positioning method for positioning a mobile object using radio waves from a GPS (Global Positioning System) satellite. In this positioning method, preferably four or more GPS satellites launched on the earth orbit are captured, and a navigation message is received to measure the mobile body. In the positioning by the GPS satellite, various methods for shortening the time from the acquisition of the GPS satellite to the positioning of the moving body have been proposed (for example, see Patent Document 1). In positioning by GPS satellites, it is necessary to capture a plurality of GPS satellites. However, in the positioning method described in Patent Document 1, a transmission time and position of at least one GPS satellite is calculated, and a mobile object input from the user By using the approximate position, positioning calculation is started without acquiring other GPS satellites.

Here, the procedure of the conventional positioning method will be briefly described. FIG. 1 shows the procedure of a conventional positioning method.
A. Calculation of pseudo distance with GPS satellite Si at time T when the radio wave is received The radio wave transmitted by GPS satellite Si (i is the satellite number) is a C / A code with a carrier wave L1 having a wavelength of 1575.42 MHz fixed for each GPS satellite. Modulated by (Coarse / Acquisition Code) and transmitted. Since the C / A code has a phase of 1023 bits per millisecond while repeating a bit string of 1 or 0, the propagation time of the radio wave is measured by this phase shift. The receiver side generates a C / A code replica of the selected GPS satellite, and uses a clock synchronized with the clock of the GPS satellite to adjust the timing so that the two C / A codes are synchronized. The pseudo distance ri to the GPS satellite Si is calculated by converting the timing adjustment amount into time and multiplying by the speed of light (radio wave speed) C. Since the clock of the receiver is inferior in accuracy to the clock of the GPS satellite, this pseudo distance ri includes the clock error of the receiver. Therefore, considering the clock error, the pseudo-intelligence distance ri can be expressed as follows.
Pseudo distance r = ρ (true distance) + s (error distance due to clock error) to (1)
B. Calculation of satellite coordinates (Xi, Yi, Zi) at time T The orbit of the GPS satellite is known from the ephemeris data of the navigation message. Therefore, the position of the GPS satellite in the orbit at time T in the receiver is calculated by a predetermined formula. F is a satellite coordinate calculation function.
(Xi, Yi, Zi) = F (T) to (2)
C. The distance between the position (x, y, z) of the moving body and the position (x, y, z) of the moving body for calculating the error distance s due to the clock error and the position of the GPS satellite is the true distance ρ. Since they are equal, the distance ρ can be expressed as:
ρi = √ {(Xi−x) ² + (Yi−y) ² + (Zi−z) ² } to (3)
Since the position of the moving body is the position of the three-dimensional space in this way, in order to determine three unknowns of x, y, and z, a total of three GPS is used to determine x, y, and z from Equation (3). The satellite can be captured and the same formula can be established. However, since the clock of the mobile receiver includes an error as described above, if the position shift due to the clock error is regarded as an unknown, the total number of unknowns is four. For this reason, normally, in single positioning by GPS satellites, four GPS satellites are captured to determine pseudorange r, and four unknowns are determined.
Pseudo distance ri = √ {(Xi−x) ² + (Yi−y) ² + (Zi−z) ² } + s (error distance due to clock error) to (4)
However, in Equation (4), the unknown number has a square or square root and is not linear, so the unknown number cannot be determined as it is. Therefore, appropriate initial values (x0, y0, z0) and s0 of unknowns are determined, linearization is performed around the initial values by Taylor expansion, and a solution is determined by a successive approximation method (Newton-Raphson method). There are no particular restrictions on the initial values (x0, y0, z0) and s0. For example, it is known that the initial values (x0, y0, z0) will eventually converge if they are used as known coordinate points on the ground. Then, the temporary pseudo distance ri (0) is expressed using the initial values (x0, y0, z0) and s0.
ri (0) = √ {(Xi−x0) ² + (Yi−y0) ² + (Zi−z0) ² } + s0
~ (5)
Since the actual pseudo distance ri is calculated, it is possible to calculate a residual Δri that is a difference from the temporary pseudo distance ri (0).

Residual Δri = ri (0) −ri˜ (6)
If the initial values (x0, y0, z0) and s0 are corrected so that the residual Δri becomes zero, the corrected position can be obtained as the final positioning result.

  Therefore, how the pseudo distance ri changes due to each of the three-dimensional directions and the clock error is calculated, and each of the initial values (x0, y0, z0) and s0 change amounts so that the residual Δri becomes zero. (Correction amount) is obtained.

  How the pseudo distance ri changes depending on the three-dimensional directions and the clock error depends on the partial differentiation (δri / δx, δri / δy, δri / δz, (δri / δs).

If the correction amounts for making the residual Δri close to zero are Δx, Δy, Δz, and Δs, the following equations are obtained.
Δr1 = {δr1 / δx} · Δx + {δr1 / δy} · Δy + {δr1 / δz} · Δz + {δr1 / δs} · Δs
Δr2 = {δr2 / δx} · Δx + {δr2 / δy} · Δy + {δr2 / δz} · Δz + {δr2 / δs} · Δs
...
Δrn = {δrn / δx} · Δx + {δrn / δy} · Δy + {δrn / δz} · Δz + {δrn / δs} · Δs
~ (7)
Equation (7) is a simultaneous equation that can be obtained by the number of captured GPS satellites, but since there are four unknowns, it is sufficient to obtain at least four equations. In the case of a computer, since the four equations are easily handled by using a matrix, the equation (7) is expressed as the equation (8). Solving equation (8) with respect to Δx, Δy, Δz, Δs, the initial values (x0, y0, z0) and the correction amount of s0 can be known.

しかしながら、式（８）式では、１回の計算で適当な補正量Δｘ、Δｙ、Δｚ、Δｓが得られるものではないので、数回同様な演算を繰り返す。すなわち、得られたΔｘ、Δｙ、Δｚ、Δｓにより初期値（ｘ０、ｙ０、ｚ０）及びｓ０を補正して、再度、仮の疑似距離ｒｉ（０）及び残差Δｒｉを求める（式（５）、（６））。そして、Δｘ、Δｙ、Δｚ、Δｓを算出し、Δｘ、Δｙ、Δｚ、Δｓが十分小さい値になったら、計算を打ち切り最終的な測位位置とする。

However, in equation (8), appropriate correction amounts Δx, Δy, Δz, Δs cannot be obtained by one calculation, and the same calculation is repeated several times. That is, the initial values (x0, y0, z0) and s0 are corrected by the obtained Δx, Δy, Δz, Δs, and the temporary pseudo distance ri (0) and the residual Δri are obtained again (formula (5)). (6)). Then, Δx, Δy, Δz, and Δs are calculated. When Δx, Δy, Δz, and Δs become sufficiently small values, the calculation is terminated and the final positioning position is obtained.

D. Correction of pseudo distance ri Once the correction amount Δs is calculated, the clock error ΔT (= Δs / c) on the receiver side can be calculated by dividing the total amount of the correction amount Δs with respect to the initial initial value s0 by the speed of light c. Therefore, the pseudo distance ri is corrected by the clock error ΔT of the receiver.

E. Repeated satellite position calculation → single positioning GPS satellites are orbiting at high speed, so if there is a clock error, the satellite coordinates (Xi, Yi, Zi) at time T will actually be at different positions in the receiver. (Step B) Therefore, the satellite coordinates (Xi ′, Yi ′, Zi ′) at time T + ΔT are calculated again from the clock error ΔT on the receiver side. Then, the temporary pseudo distance ri (0) and the residual Δri are calculated again.

The subsequent steps are the same as the single positioning in Step C. By repeating such satellite position calculation → single positioning until the clock error ΔT converges, positioning is performed with the clock error corrected with high accuracy.
Japanese Patent Laid-Open No. 6-18645

  However, if the calculation of the satellite coordinates and the single positioning are repeated in this way, it takes time until the position of the moving body is determined. This becomes more prominent as the number of GPS satellites increases.

  An object of this invention is to provide the positioning apparatus which can obtain the result of a single positioning in a shorter time in view of the said subject.

  In view of the above problems, the present invention provides a positioning method for positioning the position of a positioning device that has received radio waves based on the propagation times of radio waves transmitted by a plurality of satellites, and the positions of a predetermined number of known orbits are only once. Calculate and calculate a pseudo distance based on the temporary arrival time of radio waves from the satellite position (the approximate arrival position of the satellite is known, so the arrival time of the radio waves can be estimated), and use the pseudo distance to perform a single positioning method In this case, the position of the positioning device is measured, and if the clock error of the positioning device is greater than or equal to a predetermined value as a result of the single positioning, the pseudo distance is corrected by the clock error and the single positioning is repeated.

  According to the present invention, the position of a predetermined number of satellites whose orbits are known is calculated only once, and after that, only the normal single positioning calculation and the correction of the pseudorange are performed. The resulting positioning device can be provided.

  The present invention also relates to a positioning method for positioning the position of a positioning device that has received radio waves based on propagation times of radio waves transmitted by a plurality of satellites. (A) Satellite coordinates of the satellites at the transmission time at which the satellites have transmitted radio waves. (B) a step of calculating an initial value of the reception time when the positioning device receives the radio wave, and (c) a first pseudo distance between the satellite and the positioning device based on a difference between the reception time and the transmission time. And (d) a first pseudo-range with a plurality of satellites, and an initial position and a second pseudo-range with a predetermined initial position of the positioning device and a second pseudo-range with the satellite are reduced. And (e) determining whether or not the clock error has converged, and (f) if the clock error has not converged, the first pseudo distance based on the clock error. A step of correcting a clock error There until convergence, repeat steps (d) and (f), characterized in that.

  To provide a positioning device that can obtain a result of independent positioning in a shorter time.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 2 shows a configuration diagram of a single positioning system to which the positioning device 10 is applied. The radio wave transmitted from the GPS satellite Si is transmitted by modulating a carrier wave L1 having a wavelength of 1575.42 MHz with a fixed C / A code (Coarse / Acquisition Code) for each satellite. Note that the wavelength of the carrier wave and the C / A code are merely examples, and the positioning device 10 of the present embodiment can be applied to a positioning mode in which positioning is performed by measuring radio waves from a satellite. The object whose position is measured by the positioning device is a moving body such as a vehicle, an aircraft, a ship, etc., but the position of a stationary object may be measured.

  Each GPS satellite transmits a radio wave by carrying a navigation message on a carrier wave. The data transmission speed of the navigation message is 50 bps. The navigation message has 1500 bits of data per frame consisting of 5 subframes. Each subframe contains the status of each satellite, clock correction coefficient, orbit information (ephemeris data), orbit information (almanac data), etc. Have.

  The positioning device 10 includes an RF (Radio Frequency) unit 11, a signal treatment unit 12, and a positioning calculation unit 13. The positioning device 10 is configured as a microcomputer in which a CPU, a ROM, a RAM, an NV-RAM (Non-Volatile RAM), a communication unit, and the like are connected by a bus, and will be described later by the CPU executing a program stored in the ROM. Realize the positioning process. In addition, the signal treatment part 12 and the positioning calculating part 13 may each be comprised with the single microcomputer.

  The RF unit 11 amplifies the radio wave received by the antenna with an amplifier, and then removes the carrier wave by a filter and extracts the C / A code component. Further, since the RF unit 11 includes at least four channels, GPS satellites can be tracked by the number of channels.

  The signal processing unit 12 extracts each C / A code and navigation message data by utilizing the fact that the C / A code is different for each GPS satellite Si, and also transmits radio waves from the GPS satellite as will be described later. Specify the time.

  Since the GPS satellite that enters the predetermined elevation angle from the positioning device 10 is known from the orbit information, the signal processing unit 12 generates a C / A code replica of the GPS satellite having a high altitude (easy to receive radio waves). The C / A code of each GPS satellite is stored in advance.

  The signal processing unit 12 averages the correlation function between the generated C / A code replica and the received and extracted C / A code over several code periods, and the correlation function indicates an expected value of 1 or more. Once the A code is obtained, it is tracked as if the GPS satellite was captured.

  The signal processing unit 12 detects the phase difference between the C / A code replica obtained in the acquisition process and the extracted C / A code, and sends it to the positioning calculation unit 13. When the phase of the C / A code of the desired GPS satellite is determined, a navigation message is obtained by demodulating radio waves using the C / A code of the GPS satellite, and orbit information and the like are sent to the positioning calculation unit 13.

  Then, the positioning method of the positioning calculating part 13 is demonstrated. FIG. 3 is a flowchart showing a positioning procedure. The positioning device 10 according to the present embodiment measures the position of a moving body using the time when a GPS satellite transmits radio waves.

[Step S1]
First, the positioning calculation unit 13 calculates the satellite coordinates (Xi, Yi, Zi) at the transmission time Tsi when the GPS satellite Si transmits radio waves. Since the signal processing unit 12 generates the C / A code replica in synchronization with the highly accurate timepiece of the GPS satellite Si, the time of the timepiece of the GPS satellite is known. In addition, since the signal processing unit 12 continuously receives the C / A code, the time at which a portion of the continuous C / A code is transmitted from the GPS satellite can be obtained by referring to the clock of the positioning device 10. Is done.

  The positioning calculation unit 13 calculates the satellite coordinates of the GPS satellite Si based on the time Tsi when the GPS satellite Si thus specified transmits radio waves. As described above, since the orbit of the GPS satellite is known from the ephemeris data, the position on the orbit of the GPS satellite at time Tsi is calculated by a predetermined formula.

(Xi, Yi, Zi) = F (Tsi) to (9)
Since radio waves are captured from a plurality of GPS satellites, the transmission time Tsi is different for each satellite.

[Step S2]
The positioning calculation unit 13 calculates an initial value (temporary arrival time) of the reception time Ta at which the radio wave transmitted by the GPS satellite Si at the transmission time Tsi reaches the positioning device 10. The reception time Ta includes an error caused by the timepiece of the positioning device 10. In addition, since the positioning device 10 in principle measures the position where the distance from a plurality of GPS satellites intersects one point as the position of the moving body, the reception time Ta of the radio wave is one.

Ta = (Ts1 + Ts2 + Ts3 + ... + Tsn) / N + Tm (10)
In Equation (10), N is the number of captured GPS satellites, so the first term is the average of the GPS satellite transmission times. Tm is an approximate arrival time of radio waves from the GPS satellite to the positioning device 10. Since the approximate position of the GPS satellite is known, Tm can be estimated to be 60 to 80 milliseconds, for example.

  The calculation method of the reception time Ta is not limited to the first term of the equation (10), and may be the median value of a plurality of transmission times Tsi or may be the transmission time Tsi of the GPS satellite with the best reception state. Etc. are arbitrary.

[Step S3]
Next, the positioning calculation unit 13 calculates a pseudo distance ρi to each GPS satellite. Since the radio wave transmission time Tsi and the reception time Ta are obtained, the pseudo distance ρi is calculated by multiplying the difference between them by the speed of light.

ρi = (Ta−Tsi) × C˜ (11)
[Step S4]
Next, the positioning calculation unit 13 measures the position (x, y, z) of the moving body by single positioning. Since the principle of independent positioning is the same as that in step C described above, the overlapping part will be described briefly.

  The positioning calculation unit 13 sets up four or more equations with the position error in the three-dimensional space and the distance error due to the clock error as unknowns.

  In the present embodiment, the pseudo distance ρi is calculated by the equation (11). That is, in Formula (4), the distance error s due to the clock error is added to the pseudo distance, but in this embodiment, it is handled that Ta includes the clock error.

Next, appropriate initial values (x0, y0, z0) and s0 are determined, linearization is performed around the initial values, and a solution is determined by a successive approximation method (Newton-Raphson method). Then, the temporary pseudo distance ρi (0) is expressed using the initial values (x0, y0, z0) and s0.
ρi (0) = √ {(Xi−x0) ² + (Yi−y0) ² + (Zi−z0) ² } + s0
~ (12)
Since the actual pseudo distance ρi is calculated by the equation (11), the residual Δρi that is a difference from the temporary pseudo distance ρi (0) can be calculated.

Residual Δρi = ρi (0) −ρi˜ (13)
If the convergence calculation for correcting the initial values (x0, y0, z0) and s0 is repeated so that the residual Δρi becomes zero, the corrected position can be obtained as the final positioning result.

  Therefore, how the pseudorange ρi changes due to each three-dimensional direction and clock error is calculated, and the initial values (x0, y0, z0) at which the residual Δρi becomes zero and the respective change amounts (corrections) (Quantity). Similar to the equations (7) and (8), the initial values (x0, y0, z0) and the correction amounts Δx, Δy, Δz, Δs of s0 can be calculated.

[Step S5]
The positioning calculation unit 13 determines whether or not the correction amount Δs has converged. Whether or not it has converged is determined by whether or not Δs has become a predetermined value or less.

[Step S6]
If Δs has not converged, the positioning calculation unit 13 corrects the pseudo distance ρi calculated by Expression (11) with Δs.

ρi ′ = ρi−Δs˜ (14)
Thereafter, steps S4 to S6 are repeated.
If Δs has not converged, the process returns to step S4, and the pseudo distance ρi ′ is newly calculated. Therefore, the residual Δρi is calculated again using the equation (13). Then, correction amounts Δx, Δy, Δz, and Δs are calculated so that the residual Δρi becomes zero.

  In step S5, when the correction amount Δs converges, the calculation is terminated, and (x0, y0, z0) corrected by the correction amounts Δx, Δy, Δz are set as positioning coordinates (x, y, z). Further, the time corrected by ΔT = Δs / c obtained by dividing the correction amount Δs by the speed of light c is set as the positioning time of the positioning device 10.

  As described above, the positioning device 10 according to the present embodiment does not need to repeat the single positioning and the calculation of the satellite coordinates by calculating the satellite coordinates at the time when the GPS satellites have transmitted the radio wave in advance, so that the final positioning is performed. Can be shortened. That is, an accurate satellite position is calculated once, and thereafter only the correction of the pseudo distance is executed until the clock error converges, so that the calculation time can be shortened.

  FIG. 4 shows a table comparing the calculation times of the conventional positioning method and the positioning method of the present embodiment. 4A shows the data used for the calculation, and FIG. 4B shows the calculation result. FIG. 4 (a) shows the satellite numbers 1, 4, 7 and 13 of the four GPS satellites used, the GPS satellite navigation message (radio wave) transmission time, the pseudo distance by the conventional positioning method, and the present embodiment. The pseudo distance by the positioning method is shown. The pseudorange obtained by the conventional positioning method is obtained by multiplying the propagation time of the radio wave by the speed of light. Further, the pseudo distance according to the positioning method of the present embodiment is obtained by multiplying the transmission time by Tm (for example, 70 milliseconds) and the speed of light.

  FIG. 4B shows errors and calculation times for the x, y, and z coordinates of the moving object. The coordinate error (positioning accuracy) is the same, but according to the positioning device 10 of the present embodiment, the calculation time is almost halved.

  As is clear from the experimental results, the positioning device 10 of the present embodiment can significantly reduce the calculation time while maintaining the positioning accuracy.

It is a figure which shows the procedure of the conventional positioning method. It is a block diagram of a single positioning system. It is a flowchart figure which shows a positioning procedure. It is the table | surface which compared the calculation time of the conventional positioning method and the positioning method of this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Positioning device 11 RF part 12 Signal processing part 13 Positioning operation part

Claims (3)

In a positioning method for correcting the clock error on the receiving side based on the propagation time of radio waves transmitted by a plurality of satellites and positioning the positioning device that has received the radio waves,
Calculate the position of a given number of known orbits once,
Calculate a pseudorange based on the provisional arrival time of radio waves from the position of the satellite,
Using the pseudo distance, positioning the positioning device by a single positioning method,
As a result of the single positioning, when the clock error of the positioning device is a predetermined value or more, the pseudo distance is corrected by the amount of the clock error, and the single positioning is repeated.
A positioning method characterized by that. In a positioning method for correcting the clock error on the receiving side based on the propagation time of radio waves transmitted by a plurality of satellites and positioning the positioning device that has received the radio waves,
(A) calculating satellite coordinates of the satellite at the transmission time when the satellite transmits radio waves;
(B) calculating an initial value of a reception time when the positioning device receives the radio wave;
(C) calculating a first pseudo distance between the satellite and the positioning device based on a difference between the reception time and the transmission time;
(D) The initial position and the clock error so that a difference between a first pseudo distance with the plurality of satellites and a second pseudo distance between the predetermined initial position of the positioning device and the satellite is small. The steps to fix
(E) determining whether the clock error has converged,
(F) correcting the first pseudo distance based on the clock error when the clock error has not converged, and
Repeat steps (d) and (f) until the clock error converges,
A positioning method characterized by that. In a positioning device that receives radio waves transmitted by a plurality of satellites and corrects the clock error and positions the receiving side,
Calculating a position of a predetermined number of satellites whose orbit is known only once, and having a positioning calculation unit that calculates a pseudo distance based on a provisional arrival time of radio waves from the position of the satellite;
The positioning calculation unit measures the position of the positioning device by a single positioning method using the pseudo distance,
As a result of the single positioning, when the clock error of the positioning device is a predetermined value or more, the pseudo distance is corrected by the amount of the clock error, and the single positioning is repeated.
A positioning device characterized by that.

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