JP4400330B2 - Position detection apparatus and position detection method - Google Patents

Description

  The present invention relates to a position detection device and a position detection method for detecting the position of a mobile station.

  In recent years, GPS surveying using a carrier phase has been widely used in the field of surveying. In this GPS survey using the carrier phase, the reference side receiver and the positioning side receiver simultaneously receive satellite signals sent from a plurality of satellites, and the reference side and the positioning side integrate the carrier phase of each satellite signal. Each value is calculated independently. The integrated value of the carrier phase (hereinafter simply referred to as “phase integrated value”) includes an indeterminate element (hereinafter referred to as “integer value bias”) corresponding to an integral multiple of the wavelength of the carrier. Unlike the clock error or the like, this integer value bias cannot be eliminated by taking a single phase difference or a double phase difference of the phase integration value. For this reason, in the field of GPS surveying, a technique has been proposed in which the integral value bias, which is an uncertain factor, is eliminated by taking the triple phase difference of the phase integration value, or the integer value bias itself is obtained.

Here, as a technique for determining an integer value bias, a technique using a Kalman filter is known (see, for example, Patent Document 1). In this technology, a tracking filter that updates the state variable each time observations are made using the position on the positioning side and the integer bias as the state variables, and the single phase difference on the positioning side relative to the reference side as the observation amount is configured. Is done. As another technique for determining the integer value bias, a technique for obtaining an integer value bias of a double phase difference under a predetermined condition by a least square method using a double phase difference of a carrier wave including the integer value bias is known. (For example, refer to Patent Document 2).
JP 2004-77228 A JP 2003-98245 A

  By the way, the conventional technology as described above is based on the premise that radio waves from at least five satellites are continuously received (without a cycle trip) during the integer value bias determination process. However, in practice, there may be a case where the interruption of radio waves from a satellite that has been determined or is being determined (cycle trip). In this case, the processing for determining the integer bias must be repeated from the beginning. Don't be.

  In addition, the above-mentioned conventional technology does not assume that the positioning side moves during the integer bias determination process, but if the positioning side is a moving body such as a vehicle, the influence of surrounding buildings, tunnels, etc. Thus, a cycle trip is likely to occur even during the integer bias determination process. Moreover, since the radio wave reception state from the satellite of the receiver on the mobile unit changes due to the movement of the mobile unit, it may be necessary to switch the reference satellite used for positioning.

  Therefore, in view of the above problems, the present invention provides a position detection apparatus and a position detection method that do not require the integer bias determination process to be restarted from the beginning even when a cycle trip or switching of the reference satellite occurs. The purpose is to provide.

In order to solve the above problems, according to one aspect of the present invention, one reference satellite is selected from a plurality of satellites that can be observed by a mobile station, and observation data that the mobile station observes at predetermined intervals is used. An integer value bias included in the integrated value of the carrier phase of the satellite signal from each satellite is estimated based on the phase difference of the integrated values related to the other satellites based on the integrated value related to the reference satellite, and the estimation A position detection device for detecting the position of a mobile station based on the integer value bias,
When the reference satellite becomes unobservable, estimation of an integer bias is performed using past observation data with a satellite other than the reference satellite as a new reference satellite from among a plurality of observable satellites. It is characterized by
The other satellites to be the new reference satellites are selected as backup reference satellites before the period when the reference satellites become unobservable,
After the selection of the spare reference satellite, the processing necessary for estimating the integer bias is executed in parallel at predetermined intervals with each of the reference satellite and the spare reference satellite as a reference, and data obtained by the processing. Is used as the past observation data,
The other satellites to be the new reference satellites are selected as backup reference satellites before the period when the reference satellites become unobservable,
After the selection of the backup reference satellite, the covariance set with reference to the backup reference satellite is updated using observation data every predetermined period, and used as the past observation data,
The mobile station is a vehicle, and the position detection device is mounted on the vehicle,
There is provided a position detection device that includes detection means for detecting a dynamic state quantity relating to the movement of the vehicle, and the detection result of the dynamic state quantity is used for estimation of an integer value bias .

Further, according to another aspect of the present invention, a position detecting device for detecting a position of a mobile station by estimating an integer value bias included in an integrated value of a carrier wave phase of a satellite signal observed by the mobile station every predetermined period Because
One reference satellite is selected from a plurality of satellites that can be observed by the mobile station, and the integrated value of the carrier phase of the satellite signal from each satellite is calculated using the observation data observed by the mobile station at a predetermined period. And calculating the phase difference of the integrated values related to the other satellites based on the integrated value related to the reference satellite, and updating the first covariance data based on the reference satellite using the phase difference. First covariance update means;
A spare reference satellite that is different from the reference satellite is selected from a plurality of satellites that can be observed by the mobile station, and the carrier phase of the satellite signal from each satellite is measured using observation data that the mobile station observes at predetermined intervals. And the phase difference of the integrated values related to the other satellites based on the integrated value related to the backup reference satellite is calculated, and the second difference based on the backup reference satellite is calculated using the phase difference. Second covariance update means for updating the covariance data of
Integer value bias estimation means for estimating an integer value bias using the first covariance data obtained by the first covariance update means,
Updates by the first covariance update means and the second covariance update means are executed in parallel,
The integer value bias estimation means estimates the integer value bias using the second covariance data obtained by the second covariance update means when the reference satellite becomes unobservable. A position detection device is provided.

  In this aspect, only one backup reference satellite is selected, and when the reference satellite becomes unobservable, the first covariance update means uses the backup reference satellite as a reference satellite, and The second covariance update means selects a new backup reference satellite different from the backup reference satellite, and performs the update process on the new backup reference satellite. You may start. Alternatively, when a plurality of the reserve reference satellites are selected and the reference satellite becomes unobservable, the integer value bias estimation means may select the second reference satellite associated with the reserve reference satellite with the longest time being continuously observed. The integer value bias estimation processing may be performed using the covariance data. Alternatively, when a plurality of backup reference satellites are selected and the reference satellite becomes unobservable, the integer value bias estimation means outputs the second covariance data relating to the backup reference satellite having the smallest variance at that time. May be used to perform the integer value bias estimation process.

According to another aspect of the present invention, a reference satellite selection step of selecting one reference satellite from a plurality of satellites that can be observed by the mobile station;
A first covariance update step of updating first covariance data with reference to the reference satellite for each predetermined period using observation data observed by the mobile station for each predetermined period;
A backup reference satellite selection step of selecting a satellite other than the reference satellite as a backup reference satellite from a plurality of observable satellites;
After the preliminary reference satellite selection step, the observation is performed in parallel with the first covariance update step every predetermined period and the observation data observed by the mobile station every predetermined period is used as a reference. A second covariance update step for updating the second covariance data,
Based on the first covariance data obtained by the first covariance update step, an integer value bias included in the integrated value of the carrier phase of the satellite signal from each satellite is estimated, and the estimated integer value bias And a position detecting step for detecting the position of the mobile station based on
In the position detection step, when the reference satellite becomes unobservable, the estimation of the integer bias is executed based on the second covariance data obtained by the second covariance update step. A position detection method is provided.

  In any of the above aspects, whether or not satellite observation (reception) is impossible or possible is determined by whether or not the satellite signal reception intensity from the satellite is more than a predetermined minimum reception intensity. It may be based on judgment.

  According to the present invention, it is possible to obtain a position detection device and a position detection method that do not require the integer bias determination process to be restarted from the beginning even when the reference satellite is switched.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a carrier phase GPS positioning system according to the present invention. As shown in FIG. 1, the GPS positioning system includes a GPS satellite 10 that orbits the earth, a fixed reference station 20 that is installed at a predetermined position (known point) on the earth, and is positioned on the earth. And a mobile station 30 that can move.

  The GPS satellite 10 always broadcasts navigation messages toward the earth. The navigation message includes orbit information about the corresponding GPS satellite 10, a clock correction value, and an ionospheric correction coefficient. The navigation message is spread by the C / A code, is carried on the L1 carrier (frequency: 1575.42 MHz), and is constantly broadcast toward the earth.

  Currently, 24 GPS satellites 10 orbit the earth at an altitude of about 20,000 km, and each of the four GPS satellites 10 is evenly arranged on six Earth orbit planes inclined by 55 degrees. ing. Therefore, as long as the sky is open, at least five GPS satellites 10 can be observed at any time on the earth.

  FIG. 2 is a more detailed configuration diagram of the carrier phase GPS positioning system of FIG. The mobile station 30 includes a GPS receiver 32. In the GPS receiver 32, an oscillator (not shown) whose frequency matches the carrier frequency of the GPS satellite 10 is incorporated. The GPS receiver 32 converts the radio wave received from the GPS satellite 10 through the GPS antenna 32a into an intermediate frequency, and then performs C / A code synchronization using the C / A code generated in the GPS receiver 32. Retrieve the navigation message.

Further, the GPS receiver 32 measures the phase integration value Φ _iu of the carrier phase based on the carrier wave from each GPS satellite 10 _i . For the phase integration value Φ _iu , the subscript i (= 0, 1, 2,...) Indicates the number assigned to each GPS satellite 10 _i , and the subscript u is the integration on the mobile station 30 side. Indicates a value. As shown in the following equation, the phase integration value Φ _iu includes the phase Θ _iu (t) of the oscillator at the carrier reception time t and the carrier phase Θ _iu (t−τ) when the satellite signal is generated in the GPS satellite 10 _i. It is obtained as a difference.
Φ _iu (t) = Θ _iu (t) −Θ _iu (t−τ _u ) + N _iu + ε _iu (t) Equation (1)
Here, τ _u represents the travel time from the GPS satellite 10 to the GPS receiver 32, and ε _iu represents noise (error). Note that at the start of observation of the phase difference, the GPS receiver 32 can accurately measure the phase within one wavelength of the carrier wave phase, but cannot determine what wavelength it corresponds to. For this reason, an integer value bias N _iu is introduced to the phase integrated value Φ _iu (t) as an uncertain element as shown in the above equation.

  The mobile station 30 also includes a communication device 33 such as a mobile phone. As will be described later, the communication device 33 is configured to perform bidirectional communication with a communication facility 23 such as a mobile phone base station on the reference station 20 side.

The reference station 20 has a GPS receiver 22 including a GPS antenna 22a. GPS receiver 22, similar to the GPS receiver 32 of mobile station 30, based on the carrier wave from the GPS satellite 10 _i, as shown in the following equation, the integrated value [Phi _ib carrier phase at time t (t) Measure.
Φ _ib (t) = Θ _ib (t) −Θ _ib (t−τ _b ) + N _ib + ε _ib (t) Equation (2)
N _ib represents an integer value bias, and ε _ib represents noise (error). For the phase integration value Φ _ib , the subscript b indicates the integration value on the reference station 20 side. The reference station 20 transmits the measured phase integrated value Φ _ib to the mobile station 30 via the communication facility 23. A plurality of reference stations 20 are installed in a predetermined area. As shown in FIG. 2, each reference station 20 and communication facility 23 (or a plurality of communication facilities) may be connected via a network such as the Internet, or a communication facility 23 may be provided for each reference station 20. . In the former configuration, the mobile station 30 can obtain the information received by each reference station 20 as long as it can communicate with the communication facility 23.

  FIG. 3 is a functional block diagram showing an embodiment of the position detection apparatus 34 according to the present invention mounted on the mobile station 30. The position detection device 34 of the present embodiment is configured with a calculator 40 as the center, and the calculator 40 is connected to the GPS receiver 32 and the communication device 33 described above. Further, various sensors 50 mounted on the mobile station 30 are connected to the computing unit 40. Note that the computing unit 40 may be incorporated in the GPS receiver 32. When the mobile station 30 is a vehicle, the GPS receiver 32, the computing unit 40, and / or the communication device 33 may be mounted in the navigation device.

  The computing unit 40 may be composed of a microcomputer, and includes a satellite position calculating unit 42, a dynamic state quantity introducing unit 44, and an integer value bias estimating unit 48, as shown in FIG.

The satellite position calculation unit 42, based on the orbit information of the navigation message received by the GPS receiver 32, the position (X _i (t), Y) of each observable GPS satellite 10 _i in the world coordinate system at time t. _i (t), Z _i (t)) is calculated. Since the GPS satellite 10 is one of artificial satellites, its movement is limited to a certain plane (orbital plane) including the center of gravity of the earth. The orbit of the GPS satellite 10 is an elliptical motion with the earth's center of gravity as one focal point, and the position of the GPS satellite 10 on the orbital plane can be calculated by sequentially calculating the Kepler equation. Further, the position (X _i (t), Y _i (t), Z _i (t)) of each GPS satellite 10 _i at the carrier wave reception time t is determined by the orbital plane of the GPS satellite 10 and the equatorial plane of the world coordinate system. In consideration of the rotational relationship, the position of the GPS satellite 10 on the orbital plane is obtained by three-dimensional rotational coordinate conversion. As shown in FIG. 4, the world coordinate system is defined by an X axis and a Y axis that are orthogonal to each other within the equator plane, and a Z axis that is orthogonal to both axes, with the center of gravity as the origin.

  The dynamic state quantity introduction unit 44 calculates a predetermined dynamic state quantity of the mobile station 30 based on the output signals of the various sensors 50 input at a predetermined period, and creates a known input. For example, when the mobile station 30 is a vehicle, the dynamic state quantity introducing unit 44 includes two wheel speed sensors set on the non-driven wheels of the vehicle, various sensors such as a yaw rate sensor, a right / left G acceleration sensor, and an azimuth meter. Based on the 50 output signals, the vehicle longitudinal speed Vx (t) and the vehicle lateral speed Vy (t) at the carrier wave reception time t are calculated.

  Since the vehicle speed vectors (Vx (t), Vy (t)) are based on the body coordinate system (see FIG. 4) based on the vehicle body, the dynamic state quantity introducing unit 44 uses the speed vector (Vx ( t) and Vy (t)) are coordinate-converted into the world coordinate system via the local coordinate system. Normally, coordinate rotation conversion can be realized using Euler angles, but here, conversion from the body coordinate system to the local coordinate system is realized only with the yaw angle ψ (t), assuming that the roll angle and pitch angle are small. (However, it is naturally possible to consider the roll angle and the pitch angle, or to ignore the yaw angle.) The conversion from the local coordinate system to the world coordinate system is realized by conversion using the longitude φ (t) and the latitude λ (t) of the vehicle position.

Specifically, the vehicle position in the world coordinate system _{(X u, Y u, Z} u) and the longitude and latitude of the vehicle position (phi, lambda) and when, velocity vector d of the vehicle in terms of the world coordinate system / Dt [X _u , Y _u , Z _u ] is as follows:
d / dt [X _u , Y _u , Z _u ] ^T = rot (φ, λ) · rot (ψ) · [Vx, Vy] ^T equation (3)
Here, [] ^T means transposition of a matrix, and rot (φ, λ) and rot (ψ) are as follows.

尚、経度φ（ｔ）及び緯度λ（ｔ）は、測量が既に完了している所定地点の既知の経度及び緯度（固定値）であってよい。但し、経度φ（ｔ）及び緯度λ（ｔ）は、単独測位により得られる移動局３０の経度φ（ｔ）及び緯度λ（ｔ）（変動値）であってもよい。また、ヨー角度ψ（ｔ）は、ヨー角速度（ヨーレートセンサの検出信号）を積分することで算出されてよく、若しくは、方位角計を用いて決定されてもよい。

The longitude φ (t) and the latitude λ (t) may be known longitudes and latitudes (fixed values) at predetermined points where surveying has already been completed. However, the longitude φ (t) and the latitude λ (t) may be the longitude φ (t) and the latitude λ (t) (variation value) of the mobile station 30 obtained by independent positioning. Further, the yaw angle ψ (t) may be calculated by integrating the yaw angular velocity (detection signal of the yaw rate sensor) or may be determined using an azimuth meter.

If the right side of the above equation (3) is placed as inputs U01, U02, and U03 and discretized, the result is as follows.
X _u (t _n ) = X _u (t _n−1 ) + DT · U01 Expression (4)
Y _u (t _n ) = Y _u (t _n−1 ) + DT · U02 Formula (5)
Z _u (t _n ) = Z _u (t _n−1 ) + DT · U03 Equation (6)
Therefore, the final known input is as follows.
U = [DT · U01, DT · U02, DT · U03] ^T equation (6-1)
In the above equation, DT is a sample time (data update interval), and t _n = t _n−1 + DT. In the following description, for the sake of explanation, it is assumed that the sample time DT is the same as the calculation cycle of the phase integration value by the GPS receivers 22 and 32 described above.

In the integer value bias estimation unit 48, observation data relating to each GPS satellite 10 _i (particularly, the phase integrated value Φ _ib on the reference station 20 side received by the mobile station 30 via the communication device 33 and the phase on the mobile station 30 side). The integer value bias is estimated based on the integrated value Φ _iu ).

Specifically, the double phase difference between the phase integration values for the two GPS satellites 10 _j , 10 _h (i = j, h, where j ≠ h) at time t is expressed by the following equation.
[ _{Phi] jhbu} = ([ _{Phi] jb} (t)-[Phi] _ju (t))-([ _{Phi] hb} (t)-[Phi] _hu (t)) Equation (7)
On the other hand, the double phase difference Φ _jhbu of the phase integrated value is expressed as (distance between GPS satellite 10 _i and GPS receiver 22 or 32) = (wavelength L of carrier wave) × (phase integrated value), It becomes as follows.

Here, [X _b (t), Y _b (t), Z _b (t)] in Expression (8) are coordinate values (known) in the world coordinate system of the reference station 20 at time t, and [X _u (T), Y _u (t), Z _u (t)] are coordinate values (unknown) of the mobile station 30 at time t, and [X _j (t), Y _j (t), Z _j (t) ]] And [X _h (t), Y _h (t), Z _h (t)] are the coordinate values (calculated by the satellite position calculation unit 42) of the GPS satellites 10 _j and 10 _h at time t. N _jhbu is a double phase difference of an integer bias (that is, N _jhbu = (N _jb −N _ju ) − (N _hb −N _hu )).

In the integer value bias estimation unit 48, the following state equation is set using the known input derived by the dynamic state quantity introduction unit 44 (see the above equation (6-1)).
η (t _n ) = η (t _n−1 ) + U (t _n−1 ) + W (t _n−1 ) Equation (9)
Here, η (t _n ) represents a state variable at time t = t _n , and the position of the mobile station 30 [X _u (t _n ), Y _u (t _n ), Z _u (t _n )], And an integer value bias double phase difference N _ijbu (where i ≠ j). Here, the double difference _{N Ijbu} integer bias is required at least four, for example, when five GPS satellites _{10 0-4} is observable, based on the GPS satellites 10 _0, eta = [X _{u, Y u, Z u,} N 01bu, N 02bu, N 03bu, may be _{N 04bu].} U and W are the above-mentioned known input and disturbance (system noise: normal white noise), respectively.

The integer value bias estimation unit 48 employs the following observation equation.
Z (t _n ) = H (t _n ) · η (t _n ) + V (t _n ) (10)
Here, Z and V indicate an observation amount and an observation noise (normal white noise), respectively. The observation amount Z is a double phase difference of phase integration values (see the above formula (7)). State equation of the equation (9) is a linear, observation quantity Z is the state variable _X u, _Y since it is non-linear with respect to _u and _{Z u,} each term state variable _X u of the formula (8), _{Y u} And Z _u are partially differentiated to obtain H in equation (10).

Therefore, when the Kalman filter is applied to the state equation of the above equation (9) and the observation equation of the above equation (10), the following equation is obtained.
As time update,
η (t _n ) ⁽⁻⁾ = η (t _n−1 ) ⁽⁺⁾ + U (t _n−1 ) Equation (11)
P (t _n ) ⁽⁻⁾ = P (t _n−1 ) ⁽⁺⁾ + Q (t _n−1 ) Formula (12)
As an observation update,
^{_{K (t n) = P (}} t n) (-) · H T (t n) · (H (t n) · P (t n) (-) · H T (t n) + R (t n)) ^-1 Formula (13)
η (t _n ) ⁽⁺⁾ = η (t _n ) ⁽⁻⁾ + K (t _n ) · (Z (t _n ) −H (t _n ) · η (t _n ) ⁽⁻⁾ ) (14)
P (t _n ) ⁽⁺⁾ = P (t _n ) ⁽⁻⁾ −K (t _n ) · H (t _n ) · P (t _n ) ⁽⁻⁾ Equation (15)
Here, Q and R represent a covariance matrix of disturbance and a covariance matrix of observation noise, respectively. The above equations (11) and (14) are filter equations, the above equation (13) is a filter gain, and the above equations (12) and (15) are covariance equations. In addition, ^(-) and ⁽⁺⁾ indicated by superscript indicate before and after updating.

Next, with reference to FIG. 5, the operation of the position detection device 34 of the present embodiment will be described. The processing routine shown in FIG. 5 is executed at every calculation period (sample time DT) of the phase integrated value by the GPS receivers 22 and 32. Hereinafter, a processing routine at time t = t _n (= t _n−1 + DT) will be described as an example.

First, at step 100, the satellite information (position information of each GPS satellite 10 _i at time t = _{t n,} the phase integrated value of the reference station 20 side for each GPS satellite 10 _i, and, in the mobile station 30 side with respect to each GPS satellite 10 _i (Phase integrated value) is acquired.

In the following step 110, the satellite information obtained in the previous cycle (t = t _n-1 ) and the satellite information obtained in the current cycle are compared, and the satellite switching (for example, new whether such GPS satellites 10 _i of the occurrence and the GPS satellites 10 _i loss) has occurred is determined. At this time, only the GPS satellite 10 _i for which a predetermined minimum reception intensity or more is secured may be considered. That is, the GPS satellite 10 _i that has fallen below the minimum reception intensity in this cycle may be determined to be “disappeared (unobservable)”, and the GPS satellite 10 _i that has exceeded the minimum reception strength in this cycle may be determined. May be determined to be “appearance (observable)”.

In step 110 described above, it is determined in particular whether or not the GPS satellite 10 _i that has been observed as the reference satellite until the previous cycle is also observed in the current cycle. If the GPS satellite 10 _i that has been observed as the reference satellite becomes unobservable in this cycle, the process proceeds to step 120.

In step 120, the GPS satellite 10 _i that has been observed as a backup reference satellite is upgraded to a reference satellite, and another GPS satellite 10 _i that can be observed in this cycle is selected as a new backup reference satellite.

Here, the “preliminary reference satellite” and the “reference satellite” are handled in the same manner as described above, but differ only in whether the calculation result is used as the final output. That is, in this embodiment, substantially two or more reference satellites are selected, and the above-described calculation for the two or more reference satellites is executed in parallel. For example, if the first time (time t = t ₀₎ of the processing routine of six GPS satellites _{10 0-5} is observable, the integer ambiguity estimation unit 48, the GPS satellite 10 ₀ is selected as a reference satellite, the state variable _{η = [X u, Y u} , Z u, N 01bu, N 02bu, N 03bu, N 04bu, N 05bu] is set (initialized), which error covariance matrix P or the like is set in accordance with (initialization And the above-described Kalman filter is applied. Meanwhile, alternatively, the integer ambiguity estimation unit 48, GPS satellites 10 ₁ is selected as the preliminary reference satellite, the state variable _{η = [X u, Y u} , Z u, N 10bu, N 12bu, N 13bu, N _14bu , N _15bu ] are set (initialized), an error covariance matrix P or the like corresponding to this is set (initialized), and the above-described Kalman filter is applied. The calculation result related to the spare reference satellite is used for calculation processing in the next cycle (see the above formulas (11) to (15)) (see step 130), but for the first time when the reference satellite becomes unobservable. This is used in the positioning solution output process (see step 140). Note that “initialization” with respect to the state variable η, the error covariance matrix P, and the like refers to substituting predetermined initial values for the respective components.

In this step 120, any from a plurality of observable GPS satellites 10 ₁ of criteria to "pre-reference satellite" or "reference satellite" is standards based advanced of the GPS satellites 10 _1, anything It may be. Alternatively, "preliminary reference satellite" or "reference satellite" may be selected randomly from a plurality of observable GPS satellites 10 _1.

In the subsequent step 130, the above equations (11) to (15) are applied using the observation amount Z (t _n ) obtained in the current cycle, and positioning calculation is executed. At this time, when the process goes through the step 120, the state variable η and the error covariance matrix P set / updated with reference to the spare reference satellite are expressed as η (t _{n in the} above equations (11) and (12). ₋₁ ) ⁽⁺⁾ and P (t _n−1 ) ⁽⁺⁾ (in the case of the first processing routine, the state variable η and the error covariance matrix P initialized with reference to the spare reference satellite are , Used as η (t _n ) ⁽⁻⁾ and P (t _n ) ⁽⁻⁾ in the above formulas (11) and (12).

On the other hand, when not passing through the above step 120, that is, when the reference satellite can be observed in this cycle in the above step 110, the above equations (14) and (14) and the equation in the previous cycle (t = t _n-1 ) as usual. Using the η (t _n-1 ) ⁽⁺⁾ and P (t _n-1 ) ⁽⁺⁾ obtained by (15), the above formulas (11) to (15) are applied. This calculation process is executed in parallel for both the reference satellite and the standby reference satellite that have been observed from the previous cycle. That is, regardless of whether the process goes through the above step 120 or not, the arithmetic processing related to both the reference satellite and the backup reference satellite is executed in parallel.

Therefore, as long as the “standby reference satellite” and the “reference satellite” can be continuously observed, in the next cycle (t = t _{n + 1} ), for each of the “standby reference satellite” and the “reference satellite” in the current cycle. Using the derived η (t _n ) ⁽⁺⁾ and P (t _n ) ⁽⁺⁾ , the above formulas (11) to (15) are applied. In this way, the arithmetic processing for the “preliminary reference satellite” and the “reference satellite” is repeated independently and in parallel for each predetermined period DT. That is, the error covariance matrix P and the state variable η are derived and updated simultaneously and in parallel for the “preliminary reference satellite” and the “reference satellite”, respectively, and are inherited to the next cycle.

In the following step 140, processing for calculating and outputting a positioning solution is executed. The estimated value of the integer bias obtained from step 130 is obtained as a real number solution. However, since the integer value bias is actually an integer value, the closest integer solution (that is, wave number) is obtained with respect to the obtained real number solution. As this method, the integer value bias is decorrelated, and the search space for the integer solution is narrowed to specify the solution.
An MBDA method or the like may be used. In addition, when the GPS receivers 22 and 32 are two-frequency receivers that can receive both the L1 wave and the L2 wave emitted from the GPS satellite 10, the above-described operation is performed for each of the L1 wave and the L2 wave. Similar estimation may be performed simultaneously and in parallel to create a sum of both periods (wide lane) to narrow down integer solution candidates with integer bias.

  For the calculation and output of the positioning solution in step 140, the calculation result of step 130 for the “reference satellite” is used instead of the “preliminary reference satellite”. Therefore, when the process goes through the step 120, the calculation result of the step 130 for the new reference satellite that was upgraded to the “reference satellite” in the previous period but was the “preliminary reference satellite” in the previous period is used. The

  When the integer solution of the integer bias is determined in this way, the position of the mobile station 30 is accurately determined by the interference positioning method using the integer solution of the integer bias unless the cycle trip occurs thereafter. Can be calculated.

  By the way, according to the present embodiment, by inputting a known external input U (k) to the Kalman filter, it is possible to calculate a state variable (positioning, integer value bias) even when the mobile station 30 moves. . Therefore, even if the position detection device 34 according to the present embodiment is mounted on a moving body such as a vehicle, highly accurate positioning can be realized.

However, during the actual movement of the mobile station 30, the radio wave reception state from each GPS satellite 10 _i is not stable due to the influence of surrounding buildings, tunnels, etc., and the radio wave is stably received from a certain number of GPS satellites 10 _i. There are cases where it is impossible. In particular, when the GPS satellite 10 _i used as the reference satellite becomes unobservable, one new reference satellite is specified from the plurality of observable GPS satellites 10 _i , and an integer value is set based on the new reference satellite. The bias confirmation process must be started from the beginning.

In addition, while the mobile station 30 is actually moving, the GPS satellite 10 _i that can be observed by the mobile station 30 may change as the mobile station 30 moves over a long distance, and the reference satellite may need to be switched. . In this way, every time a cycle trip or switching of the reference satellite occurs, the integer bias determination process is restarted from the beginning for the new reference satellite (that is, the error covariance matrix P based on the new reference satellite). In the configuration in which all components of the state variable η are initialized), the position detection accuracy is temporarily deteriorated frequently due to the initialization, so that it is not suitable for a moving body such as a vehicle.

  On the other hand, according to the present embodiment, as described above, a standby reference satellite is selected separately from the reference satellite, and the same calculation processing as that for the reference satellite is performed on the backup reference satellite. Thus, even when the reference satellite is switched or a cycle trip occurs, the error covariance matrix P and the state variable η for the backup reference satellite derived before the switching can be used as they are. As a result, it is not necessary to repeat the integer bias determination process from the beginning after the reference satellite is switched, and the position detection accuracy is not greatly deteriorated. That is, according to the present embodiment, it is possible to realize position detection that is robust against switching of reference satellites and cycle trips, and maintains stable position detection accuracy even when mounted on a moving body such as a vehicle. can do.

  In this embodiment, the number of spare reference satellites may be 1 from the viewpoint of calculation load. In this case, each time the reference satellite becomes unobservable and the spare reference satellite is upgraded as a new reference satellite as described above, or every time the spare reference satellite becomes unobservable, one new spare reference satellite is set. Is done. Alternatively, the number of spare reference satellites may be a fixed value or a fluctuation value of 2 or more. In this case, when the reference satellite becomes unobservable, an appropriate backup reference satellite may be upgraded as a new reference satellite according to the priority assigned in advance. Alternatively, when the reference satellite becomes unobservable, the standby reference satellite continuously observed with the longest cycle may be upgraded as a new reference satellite. Alternatively, when the reference satellite becomes unobservable, the standby reference satellite having the smallest dispersion at that time may be upgraded as a new reference satellite. Thereby, temporary deterioration of accuracy at the time of switching of the reference satellite can be further suppressed.

FIG. 6 is test data demonstrating high position detection accuracy realized by the position detection device 34 according to the present embodiment. FIG. 6A shows a test result by a configuration to which the algorithm of the present embodiment (parallel operation processing introducing a spare reference satellite) is applied, the horizontal axis indicates the number of epochs (operation), and the vertical axis indicates positioning error. Is shown. FIG. 6B shows a test result by a configuration in which the error covariance matrix P is initialized every time the reference satellite is switched. All the calculation results are executed using the same satellite orbit data in which the switching of the GPS satellite 10 _i occurs frequently.

  When the algorithm of the present embodiment is not applied, as shown in FIG. 6B, a large accuracy error occurs when the reference satellite is switched, and the variation of the solution is large. When the algorithm of the example is applied, as shown in FIG. 6A, the dispersion of the solution is small, and it becomes possible to obtain a solution with good accuracy. That is, as shown in FIG. 6A, the reference satellites are switched at three points in time. At the time of the switching, the calculation results for the spare reference satellites calculated as the back process as described above are used. It is possible to obtain a highly accurate solution at the time of the switching (and after the switching).

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the Kalman filter is applied to the state equation of the above equation (9) and the observation equation of the above equation (10), but the present invention uses other estimation methods such as the least square method. The present invention can also be applied to the configuration to be applied.

  In the above-described embodiment, the known input U is introduced into the state equation of the above equation (9) so that the integer value bias can be determined with high accuracy in a short time even while the mobile station 30 is moving. The dynamic movement of the mobile station 30 may be compensated by other methods, or the compensation may be simply omitted (that is, there is no known input U).

  In the above-described embodiment, the influence of the initial phase of the oscillator and the clock error in the GPS receivers 22 and 32 is eliminated by taking the double phase difference as described above. A single phase difference that can eliminate only the initial phase and the GPS clock error may be employed. Further, in this embodiment, the ionospheric refraction effect, the tropospheric refraction effect, and the influence of multipath are ignored, but these may be taken into consideration.

  In the above description, a vehicle is given as an example of the mobile station 30, but the mobile station 30 may be a hawk lift, robot, receiver 32, and / or arithmetic unit in which the receiver 32 and / or the arithmetic unit 40 is mounted. An information terminal such as a mobile phone incorporating the device 40 is included.

  In the above-described embodiment, since constants are used for other covariance matrices (for example, Q, R), parallel calculation processing using a spare reference satellite as in the case of the error covariance matrix P is unnecessary. However, if a constant is not employed, similar parallel processing may be applied to other covariance matrices.

1 is a configuration diagram of a carrier phase GPS positioning system according to the present invention. It is a more detailed block diagram of the carrier wave phase type GPS positioning system of FIG. 2 is a functional block diagram showing an embodiment of a position detection device 34 according to the present invention mounted on a mobile station 30. FIG. It is a figure which shows the relationship between a world coordinate system and a local coordinate system, and the relationship between a local coordinate system and a body coordinate. It is a flowchart of the process implement | achieved by the position detection apparatus 34 of a present Example. It is test data which demonstrates the high position detection accuracy implement | achieved by the position detection apparatus 34 by a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 GPS satellite 20 Reference station 22 Reference station side GPS receiver 30 Mobile station 32 Mobile station side GPS receiver 34 Position detector 40 Calculator 42 Satellite position calculation part 44 Dynamic state quantity introduction part
48 Integer Bias Estimator

Claims (7)

One reference satellite is selected from a plurality of satellites that can be observed by the mobile station, and is included in the integrated value of the carrier phase of the satellite signal from each satellite using observation data that the mobile station observes every predetermined period Position detection for estimating an integer value bias based on a phase difference between integrated values related to other satellites based on the integrated value related to the reference satellite, and detecting the position of the mobile station based on the estimated integer value bias A device,
When the reference satellite becomes unobservable, estimation of an integer bias is performed using past observation data with a satellite other than the reference satellite as a new reference satellite from among a plurality of observable satellites. It is characterized by
The other satellites to be the new reference satellites are selected as backup reference satellites before the period when the reference satellites become unobservable,
After the selection of the spare reference satellite, the processing necessary for estimating the integer bias is executed in parallel at predetermined intervals with each of the reference satellite and the spare reference satellite as a reference, and data obtained by the processing. Is used as the past observation data,
The other satellites to be the new reference satellites are selected as backup reference satellites before the period when the reference satellites become unobservable,
After the selection of the backup reference satellite, the covariance set with reference to the backup reference satellite is updated using observation data every predetermined period, and used as the past observation data,
The mobile station is a vehicle, and the position detection device is mounted on the vehicle,
A position detection device comprising detection means for detecting a dynamic state quantity relating to the movement of the vehicle, wherein the detection result of the dynamic state quantity is used for estimation of an integer value bias. A position detection device that detects an integer value bias included in an integrated value of a carrier wave phase of a satellite signal observed by a mobile station every predetermined period, and detects the position of the mobile station,
One reference satellite is selected from a plurality of satellites that can be observed by the mobile station, and the integrated value of the carrier phase of the satellite signal from each satellite is calculated using the observation data observed by the mobile station at a predetermined period. And calculating the phase difference of the integrated values related to the other satellites based on the integrated value related to the reference satellite, and updating the first covariance data based on the reference satellite using the phase difference. First covariance update means;
A spare reference satellite that is different from the reference satellite is selected from a plurality of satellites that can be observed by the mobile station, and the carrier phase of the satellite signal from each satellite is measured using observation data that the mobile station observes at predetermined intervals. And the phase difference of the integrated values related to the other satellites based on the integrated value related to the backup reference satellite is calculated, and the second difference based on the backup reference satellite is calculated using the phase difference. Second covariance update means for updating the covariance data of
Integer value bias estimation means for estimating an integer value bias using the first covariance data obtained by the first covariance update means,
Updates by the first covariance update means and the second covariance update means are executed in parallel,
The integer value bias estimation means estimates the integer value bias using the second covariance data obtained by the second covariance update means when the reference satellite becomes unobservable. , Position detection device. Only one spare reference satellite is selected,
When the reference satellite becomes unobservable, the first covariance update means takes over the update process by the second covariance update means using the backup reference satellite as a reference satellite, and the second covariance update means The position detecting device according to claim 2, wherein the update unit selects a new backup reference satellite different from the backup reference satellite, and starts the update process for the new backup reference satellite. A plurality of spare reference satellites are selected,
When the reference satellite becomes unobservable, the integer value bias estimation means uses the second covariance data related to the standby reference satellite with the longest time being continuously observed, to estimate the integer value bias. The position detection device according to claim 2, which performs processing. A plurality of spare reference satellites are selected,
When the reference satellite becomes unobservable, the integer value bias estimation means performs the integer value bias estimation process using the second covariance data related to the standby reference satellite having the smallest variance at that time point. The position detection device according to claim 2. A reference satellite selection step for selecting one reference satellite from a plurality of satellites that can be observed by the mobile station;
A first covariance update step of updating first covariance data with reference to the reference satellite for each predetermined period using observation data observed by the mobile station for each predetermined period;
A backup reference satellite selection step of selecting a satellite other than the reference satellite as a backup reference satellite from a plurality of observable satellites;
After the preliminary reference satellite selection step, the observation is performed in parallel with the first covariance update step every predetermined period and the observation data observed by the mobile station every predetermined period is used as a reference. A second covariance update step for updating the second covariance data,
Based on the first covariance data obtained by the first covariance update step, an integer value bias included in the integrated value of the carrier phase of the satellite signal from each satellite is estimated, and the estimated integer value bias And a position detecting step for detecting the position of the mobile station based on
In the position detection step, when the reference satellite becomes unobservable, the estimation of the integer bias is executed based on the second covariance data obtained by the second covariance update step. The position detection method characterized by the above-mentioned.   A storage medium storing a computer-readable program for executing the position detection method according to claim 6.

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