JP2008249427A - Positioning device for moving body, and positioning method for moving body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform accurate positioning even during a multipath generation time. <P>SOLUTION: A positioning device for a moving body includes a pseudo distance calculation means 203, a calculation means 212 of a distance between a satellite and the moving body for calculating the distance between the satellite and the moving body by integrating a variation (hereinafter referred to as a distance variation) of the distance between the satellite and the moving body determined from an observation value of a satellite radio wave to an initial value of the distance between the satellite and the moving body, a mode switching means 208 for switching the first distance calculation mode by the pseudo distance calculation means to/from the second distance calculation mode by the calculation means of the distance between the satellite and the moving body, and a composite wave detection means 206 for detecting reception of a composite wave comprising a direct wave of the satellite radio wave and its reflected wave. The device has a characteristic wherein the mode switching means switches from first distance calculation mode to the second distance calculation mode, when reception of the composite wave is detected by the composite wave detection means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a moving body positioning device and a moving body positioning method that can perform positioning accurately even when multipath occurs.

Conventionally, a means for detecting a phase of a PN code related to a signal received from a GPS satellite and obtaining a pseudorange from the GPS satellite using this phase, and a Doppler component included in a carrier received from the GPS satellite are integrated from a predetermined time point. Means for determining the amount of change in the pseudo distance from the time point, means for correcting the pseudo distance based on the obtained amount of change, and use of the mobile body or the mobile device related to the mounting using the corrected pseudo distance There is known a GPS receiver characterized by comprising a means for obtaining a person's position (see, for example, Patent Document 1).
JP-A-7-198821

  However, in the technique described in Patent Document 1 described above, a positioning method that performs so-called carrier smoothing is employed. However, when multipath (receives radio waves propagated through multiple paths) occurs, the phase of the PN code Even if carrier smoothing is performed, the accuracy of the pseudo distance obtained from the above becomes worse.

  Accordingly, an object of the present invention is to provide a moving body positioning device and a moving body positioning method that can perform positioning accurately even when multipath occurs.

In order to achieve the above object, the first invention provides a positioning device for a mobile unit that receives satellite radio waves from a satellite by a mobile unit and measures the position of the mobile unit.
A pseudo-range calculating means for calculating a pseudo-range between the satellite and the moving body based on the code phase of the signal carried on the satellite radio wave;
The initial value of the distance between the satellite and the moving object is multiplied by the amount of change in the distance between the satellite and the moving object (hereinafter referred to as the distance change amount) obtained from the observation value of the satellite radio wave. A distance calculating means for calculating a distance between the satellite moving bodies;
Mode switching means for switching between a first distance calculation mode by the pseudo distance calculation means and a second distance calculation mode by the inter-satellite moving distance calculation means;
A synthetic wave detecting means for detecting reception of a synthetic wave composed of a direct wave of a satellite radio wave and a reflected wave thereof;
The mode switching means switches from the first distance calculation mode to the second distance calculation mode when reception of the synthesized wave is detected by the synthesized wave detecting means.

2nd invention is the positioning apparatus for moving bodies which concerns on 1st invention,
The inter-satellite moving body distance calculating means uses the pseudo distance calculated by the pseudo distance calculating means before the reception of the combined wave is detected as the initial value. The term “before the reception of the composite wave” is preferably the time immediately before the reception state of only the direct wave changes to the reception state of the composite wave (the latest observation period).

3rd invention is the positioning apparatus for moving bodies based on 1st invention,
The inter-satellite moving distance calculating means calculates the distance change amount based on the observed value of the Doppler frequency of the satellite radio wave in the first period in which the reception of the composite wave is detected, while From the predetermined period, the distance change amount is calculated as a difference value of each pseudo distance calculated by the pseudo distance calculating means in each period. The predetermined period may be a period immediately after the initial period, or may be a period after a plurality of periods from the initial period, or may be an interval between periods or a bias included in an observed value of the Doppler frequency. It may be determined in consideration of an accumulation mode of errors caused by components.

4th invention is the positioning method for mobile bodies which receives the satellite radio wave from a satellite by a mobile body, and measures the position of this mobile body,
A pseudo-range calculation step for calculating a pseudo-range between the satellite and the moving body based on the code phase of the signal carried on the satellite radio wave;
The initial value of the distance between the satellite and the moving object is multiplied by the amount of change in the distance between the satellite and the moving object (hereinafter referred to as the distance change amount) obtained from the observation value of the satellite radio wave. A distance calculation step between satellite moving bodies for calculating the distance between
A combined wave detection stage for detecting reception of a combined wave composed of a direct wave of a satellite radio wave and a reflected wave thereof at a predetermined period;
A step of positioning the position of the moving body using the inter-satellite moving body distance calculated in the satellite moving body distance calculating step when reception of the combined wave is detected in the synthetic wave detecting stage. It is characterized by that.

5th invention is the positioning method for moving bodies which concerns on 4th invention,
In the distance calculation step between the satellite mobile bodies, the pseudo distance calculated in the pseudo distance calculation step before the period in which the reception of the synthetic wave is detected in the synthetic wave detection step is used as the initial value. To do.

6th invention is the positioning method for moving bodies which concerns on 4th invention,
When reception of the composite wave is detected in a continuous cycle in the composite wave detection step, in the initial cycle in which reception of the composite wave is detected in the inter-satellite mobile unit distance calculation step, the distance change amount Is calculated on the basis of the observed value of the Doppler frequency of the satellite radio wave, while the difference in the pseudo distance calculated in each period of the pseudo distance calculation stage from the predetermined period after the first period is calculated. It is calculated as a value.

  ADVANTAGE OF THE INVENTION According to this invention, the positioning apparatus for moving bodies and the positioning method for moving bodies which can be measured with sufficient precision at the time of multipath generation are obtained.

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

  FIG. 1 is a system configuration diagram showing an overall configuration of a GPS (Global Positioning System) to which a mobile positioning device according to the present invention is applied. As shown in FIG. 1, the GPS is composed of a GPS satellite 10 that orbits the earth and a vehicle 90 that is located on the earth and can move on the earth. The vehicle 90 is merely an example of a moving body, and other moving bodies include motorcycles, railways, ships, airplanes, hawk lifts, robots, information terminals such as mobile phones that move with the movement of people, and the like. There can be.

  The GPS satellite 10 constantly broadcasts navigation messages (satellite signals) toward the earth. The navigation message includes satellite orbit information (ephemeris and almanac) regarding the corresponding GPS satellite 10, a clock correction value, and an ionosphere correction coefficient. The navigation message is spread by the C / A code, is carried on the L1 wave (frequency: 1575.42 MHz), and is constantly broadcast toward the earth. The L1 wave is a combined wave of a Sin wave modulated with a C / A code and a Cos wave modulated with a P code (Precision Code), and is orthogonally modulated. The C / A code and the P code are pseudo noise codes, and are code strings in which -1 and 1 are irregularly arranged periodically.

  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.

  The vehicle 90 is equipped with a GPS receiver 20 as a moving body positioning device.

  FIG. 2 is a block diagram illustrating an example of a main configuration of the GPS receiver 20. FIG. 3 is a block diagram illustrating an example of a main configuration of the DLL 203 of the GPS receiver 20.

Here, the signal processing of the GPS receiver 20 related to the satellite signal from the GPS satellite 10 _j out of the plurality of observable GPS satellites 10 will be described as a representative. The signal processing for the satellite signal from the GPS satellite 10 _j is substantially the same as the signal processing for the satellite signal from the other GPS satellites 10. Actually, the signal processing relating to the satellite signal described below is executed in parallel (simultaneously) on the satellite signals from the observable GPS satellites.

  As shown in FIG. 2, the GPS receiver 20 includes a high-frequency circuit 201, an A / D (analog-to-digital) conversion circuit 202, a DLL (Delay-Locked Loop) 203, and a PLL (Phase-Locked Loop). 204, a filter 205, a multipath detection unit 206, a mode switching unit 208, a satellite position calculation unit 209, a satellite-vehicle distance calculation unit 212, and a positioning calculation unit 214.

  The A / D conversion circuit 202 converts the IF signal (analog signal) supplied from the high frequency circuit 201 into a digital IF signal so that digital signal processing can be performed.

The DLL 203 is configured to perform a C / A code synchronization with an L1 wave C / A code using an internally generated replica C / A code and calculate a pseudorange ρ ′ _j . As the meaning of the code, “′” added to the pseudorange ρ _j indicates that the filtering process described later is not executed, and the subscript “ _j ” is a value (ρ ′ ′) for the GPS satellite 10 _{j. The} same applies to values other than _j ). The digital IF signal is actually multiplied by a replica carrier supplied from the PLL 204 by a mixer (not shown) and then input to the DLL 203.

  Specifically, as shown in FIG. 3, the DLL 203 includes a cross-correlation calculation units 111 and 112, a phase advancement unit 113, a phase delay unit 114, a phase shift calculation unit 115, a phase correction amount calculation unit 116, a replica C / A. A code generation unit 117 and a pseudo distance calculation unit 118 are included.

The replica C / A code generation unit 117 generates a replica C / A code. The replica C / A code is a code having the same sequence of +1 and −1 with respect to the C / A code put on the satellite signal from the GPS satellite 10 _j .

The replica C / A code generated by the replica C / A code generation unit 117 is input to the cross correlation calculation unit 111 via the phase advancement unit 113. That is, an early replica code is input to the cross correlation calculation unit 111. In the phase advancer 113, the replica C / A code is advanced by a predetermined phase. Let the phase advance amount advanced by the phase advancer 113 be θ _j .

  In addition, the digital correlation signal is input to the cross-correlation calculation unit 111 after being multiplied by a replica carrier generated by the PLL 204 by a mixer (not shown).

The cross-correlation calculating unit 111 calculates a correlation value (Early correlation value E _CA ) using the input digital IF signal and the Early replica code of the phase advance amount θ _j . The Early correlation value E _CA is calculated by the following equation, for example.
Early correlation value E _CA = Σ {(digital IF) × (Early replica code)}
The replica C / A code generated by the replica C / A code generation unit 117 is input to the cross correlation calculation unit 112 via the phase delay unit 114. That is, the late replica code is input to the cross-correlation calculation unit 112. In the phase delay unit 114, the replica C / A code is delayed by a predetermined phase. The amount of phase delay delayed by the phase delay unit 114 is the same as the phase advance amount θ and has a different sign.

  Further, the digital correlation signal is input to the cross-correlation calculation unit 112 after being multiplied by the replica carrier generated by the PLL 204 by a mixer (not shown).

The cross-correlation calculation unit 112 calculates a correlation value (Late correlation value L _CA ) using the input digital IF signal and the Late replica code of the phase delay amount −θ. The Late correlation value L _CA is calculated by the following equation, for example.
Late correlation value L _CA = Σ {(digital IF) × (Late replica code)}
In this way, the cross-correlation calculators 111 and 112 execute the correlation value calculation with the correlator interval L (also referred to as “spacing”) being 2θ. The Early correlation value E _CA and the Late correlation value L _CA calculated by the cross correlation calculation units 111 and 112 are input to the phase shift calculation unit 115.

The phase shift calculation unit 115 calculates the degree of phase shift between the digital IF signal and the replica C / A code generated by the replica C / A code generation unit 117. That is, the phase shift calculation unit 115 calculates (estimates) the phase shift amount Δφ of the replica C / A code with respect to the received C / A code. The phase shift amount Δφ of the replica C / A code is calculated by the following equation, for example.
(Phase shift amount Δφ) = (E _CA −L _CA ) / 2 (E _CA + L _CA )
The phase shift amount Δφ calculated in this way is input to the phase correction amount calculation unit 116.

In the phase correction amount calculation unit 116, an appropriate phase correction amount is calculated so as to eliminate the phase shift amount Δφ. An appropriate phase correction amount is calculated, for example, according to the following arithmetic expression.
(Phase correction amount) = (P gain) × (phase shift amount Δφ) + (I gain) × Σ (phase shift amount Δφ)
This equation is an equation representing feedback control using PI control, and the P gain and the I gain are experimentally determined from the balance between variation and response, respectively. The phase correction amount calculated in this way is input to the replica C / A code generation unit 117.

  In the replica C / A code generation unit 117, the phase of the generated replica C / A code is corrected by the phase correction amount calculated by the phase correction amount calculation unit 116. That is, the tracking point of the replica C / A code is corrected. The replica C / A code thus generated is input to the cross-correlation calculation units 111 and 112 via the phase advance unit 113 and the phase delay unit 114 as described above, and also to the pseudo distance calculation unit 118. In the cross-correlation calculators 111 and 112, the replica C / A code generated in this way is used for correlation value calculation for the IF digital signal input in the next observation cycle.

The pseudo distance calculation unit 118 calculates the pseudo distance ρ ′ _j based on the replica C / A code generated by the replica C / A code generation unit 117 using, for example, the following equation.
ρ ′ _j = N _CA × 300
Here, N _CA corresponds to the number of bits of the C / A code between the GPS satellite 10 _j and the vehicle 90, and the phase and reception of the replica C / A code generated by the replica C / A code generation unit 117. It is calculated based on the receiver clock inside the machine 1. The numerical value 300 is derived from the fact that the C / A code has a 1-bit length of 1 μs and a length corresponding to 1 bit of about 300 m (1 μs × light speed). A signal representing the pseudo distance ρ ′ _j calculated in this way is input from the DLL 203 to the filter 205.

Returning to FIG. The PLL 204 measures the Doppler frequency (Doppler component) Δf _j of the Doppler-shifted received carrier by performing a correlation value calculation with the received carrier (received carrier) using the internally generated carrier replica signal. It is configured. Actually, the digital IF signal is multiplied by a replica C / A code supplied from the DLL 203 by a mixer (not shown) and then input to the PLL 204. The PLL 204 calculates the Doppler frequency Δf _j (= fr−f _L ) based on the replica carrier frequency fr and the known carrier frequency f _L (1575.42 MHz).

In the filter 205, for example, the pseudo distance ρ _j after the filter processing is calculated according to the following arithmetic expression.

ここで、（ｉ）は今回値を表し、（ｉ−１）は前回値を表し、Ｍは、重み係数である。Ｍの値は、精度と応答性を考慮しつつ適切に決定される。また、ΔＶは、ＧＰＳ衛星１０_ｊと車両９０との間の相対速度を表し、ＰＬＬ２０４から得られるドップラ周波数Δｆ_ｊを用いて、例えば以下の関係式により算出されてよい。
Δｆ_ｊ＝ΔＶ・ｆ_Ｌ／（ｃ−ΔＶ）
尚、上述のフィルタ２０５のフィルタ処理は、本分野で知られているキャリアスムージングと呼ばれる処理であり、上述のハッチフィルタを用いたフィルタ処理以外にも、例えばカルマンフィルタを用いても実現可能である。

Here, (i) represents the current value, (i-1) represents the previous value, and M is a weighting factor. The value of M is appropriately determined in consideration of accuracy and responsiveness. ΔV represents a relative speed between the GPS satellite 10 _j and the vehicle 90, and may be calculated using the Doppler frequency Δf _j obtained from the PLL 204, for example, according to the following relational expression.
Δf _j = ΔV · f _L / (c−ΔV)
Note that the filter processing of the above-described filter 205 is processing known as carrier smoothing known in this field, and can be realized by using, for example, a Kalman filter in addition to the above-described filter processing using the hatch filter.

  The multipath detection unit 206 detects the occurrence of multipath (receives radio waves propagating through multiple paths), that is, reception of a composite wave composed of a direct wave of a satellite radio wave and a reflected wave thereof. The cycle of the multipath detection process by the multipath detection unit 206 is synchronized with the above-described pseudorange observation cycle.

  FIG. 4 is a diagram schematically illustrating the state of the vehicle at time t = t1 when the multipath does not occur and the state of the vehicle at time t = t2 when the multipath occurs. Multipath occurs mainly due to a reflector (eg, a high-rise building) existing around the vehicle. Various methods for detecting the occurrence of multipath have been proposed, and any appropriate method may be adopted. For example, the occurrence of multipath may be detected by utilizing the fact that the temporal change of the pseudo distance calculated by DLL 203 becomes abnormally large in the cycle in which multipath has occurred. Alternatively, the occurrence of multipath may be detected by utilizing the fact that C / N, which is the ratio between the intensity (power) of a carrier wave and the intensity (power) of noise, decreases in the cycle in which the multipath occurs.

  FIG. 5 is a diagram illustrating another example of a method for detecting the occurrence of multipath. In FIG. 5, the horizontal axis represents the code phase of the CA code, and the vertical axis represents the correlation value.

In the situation where the multibus does not occur, only the direct wave is received from the GPS satellite 10 _j. Therefore, the correlation characteristic between the C / A code and the replica C / A code is shown in FIG. As shown by the straight line, the image is symmetrical with respect to the correlation peak value. On the other hand, when a multibus occurs, a reflected wave having a correlation peak value is received with a code phase shifted from the code phase of the correlation peak value related to the direct wave, as shown by a straight line of the reflected wave in FIG. The Therefore, when a multibus occurs, a combined wave of a direct wave and a reflected wave as shown by the straight line of the received wave in FIG. 5 is received. In the example shown in FIG. 5, the reflected wave has an upward convex correlation value characteristic, but may have a downward convex correlation value characteristic. In any case, when a multibus occurs, the correlation peak related to the direct wave does not appear clearly in the correlation value characteristic of the received wave, so that it is difficult to detect the code phase that takes the correlation peak value. As a result, the phase shift amount Δφ can change greatly. Further, when a multibus occurs, the correlation peak value of the received wave greatly changes with respect to the correlation peak value in a situation where the multibus does not occur. Therefore, the multipath detecting unit 206 may determine that a multipath has occurred by detecting such a phase shift amount Δφ or a change mode of the correlation peak value.

  When the multipath detection unit 206 detects the occurrence of multipath, the multipath detection unit 206 outputs a mode switching command from the normal mode to the multipath mode to the mode switching unit 208. Further, after detecting the occurrence of multipath, the multipath detection unit 206 outputs a mode switching command from the multipath mode to the normal mode to the mode switching unit 208 when the occurrence of multipath is not detected. . The mode switching command is supplied to the mode switching unit 208 in synchronization with the pseudo-distance observation period described above.

The mode switching unit 208 performs mode selection between the normal mode and the multipath mode in response to the mode switching command from the multipath detection unit 206. The mode switching period by the mode switching unit 208 is synchronized with the observation period. As shown in FIG. 6, the mode switching unit 208 forms a multipath mode (step 710) and detects a multipath in the period in which the occurrence of multipath is detected by the multipath detection unit 206 (YES in step 700). In the period in which the occurrence of multipath is not detected by the unit 206 (NO in step 700), the normal mode is formed (step 720). When the normal mode is selected, the pseudo distance ρ _j after the filter processing from the filter 205 is output to the positioning calculation unit 214 described later. If the multi-path mode is selected, later satellite - satellite from the inter-vehicle distance calculating section 212 - a vehicle distance d _j is output to the positioning computation unit 214 will be described later.

Returning to FIG. The satellite position calculation unit 209, based on the satellite orbit information of the navigation message, the current position S _j = (X _j , Y _j , Z _j ) and the moving speed V _j = (in the world coordinate system of the GPS satellite 10 _j. V _j , V _j , V _j ) are calculated. The satellite moving velocity vector V _j = (V _j , V _j , V _j ) may be calculated by dividing the difference between the calculated current value and the previous value of the satellite position S _j by the time width of the calculation cycle. The satellite position S _j and the satellite moving speed vector V _j derived in this way by the satellite position calculation unit 209 are input to the positioning calculation unit 214.

The satellite-vehicle distance calculation unit 212 outputs the previous value ρ _j (i-1) of the pseudo distance ρ _j output from the filter 205 or the satellite-vehicle distance d calculated by the satellite-vehicle distance calculation unit 212 itself. _j of previous values _d j of the (i-1), used as the initial value, the initial value, the satellite between the previous period (i-1) to the current period (i) - the vehicle distance _{d j} of variation Δd _j (hereinafter referred to as “distance change Δd _j (i) of current cycle (i)”) is added to calculate satellite-vehicle distance d _j (i) of the current cycle. That is, the satellite-to-vehicle distance calculation unit 212 uses d _j (i) = ρ _j (i−1) + Δd _j (i) or d _j (i) = d _j (i−1) + Δd _j (i ), The satellite-to-vehicle distance d _j (i) in the current cycle is calculated. Which of the previous value ρ _j (i−1) of the pseudorange ρ _j and the previous value d _j (i−1) of the satellite-vehicle distance d _j is used as the initial value of the current cycle (i) Depends on the mode of period (i-1). That is, when the mode of the previous cycle (i−1) is the normal mode, the previous value ρ _j (i−1) of the pseudo distance ρ _j is used as the initial value of the current cycle (i), and the previous cycle (i− When the mode 1) is the multipath mode, the previous value d _j (i−1) of the satellite-vehicle distance d _j is used as the initial value of the current cycle (i). Therefore, in the period (i) when the occurrence of multipath is detected for the first time by the multipath detection unit 206, the satellite-to-vehicle distance calculation unit 212 sets the previous value ρ _j (i−1) of the pseudo distance ρ _j as the initial value. If the satellite-vehicle distance d _j (i) of the current cycle is calculated and the multipath detection unit 206 continuously detects the occurrence of multipath in the subsequent cycle (i), the satellite- the inter-vehicle distance calculating section 212, satellite - as an initial value the previous value d _{j (i-1)} of the vehicle distance d _j, satellite each period - that continue to calculate the inter-vehicle distance d _{j (i)} Become.

Here, an example of a method of calculating the distance change amount Δd _j (i) of the current cycle (i) in the satellite-vehicle distance calculation unit 212 will be described.

The distance change Δd _j (i) in the current cycle (i) is based on the Doppler frequency Δf _j (i) or Δf _j (i-1) observed in the current cycle (i) or the previous cycle (i-1). May be calculated. Specifically, the distance change amount Δd _j (i) in the current cycle (i) is obtained by changing the relative speed ΔV between the GPS satellite 10 _j and the vehicle 90 from the previous cycle (i−1) to the current cycle (i). May be calculated by time integration over an elapsed time (ie, sampling interval). That is, Δd _j (i) = ∫ΔV · dt may be calculated. ΔV is a relative speed in a direction connecting the GPS satellite 10 _j and the vehicle 90, and is calculated according to a relational expression, for example, Δf _j = ΔV · f _L / (c−ΔV). As Δf _j , the Doppler frequency Δf _j (i) or Δf _j (i−1) observed in the current cycle (i) or the previous cycle (i−1) may be used. C is the speed of light. Alternatively, ΔV may be calculated by ΔV = λ · Δf _j using Doppler frequency Δf _j (i) or Δf _j (i−1) as Δf _j . Note that λ is the wavelength (known) of the carrier wave.

The positioning calculation unit 214 uses the pseudo-range ρ _j (i) after the filter processing from the filter 205 or the satellite-to-vehicle distance d _j (i) from the satellite-to-vehicle distance calculation unit 212 and the GPS satellite 10 _j. satellite position according to on the basis of _{(, X j (i) Y} j (i), Z j (i)) and the position of the vehicle 90 at the current period _{(i) (X u (i} ), Y u (i ), Z _u (i)) is calculated. The positioning of the position of the vehicle 90 may be executed using, for example, the least square method based on the following relational expression.

尚、ｃ・ΔＴは、ＧＰＳ受信機２０における時計誤差を表わす。この場合、例えば測位に用いるＧＰＳ衛星１０_ｊの数が４つである場合には、数５の式が４つ立つので、時計誤差ｃ・ΔＴを除去した測位が実現される。尚、この際、ＧＰＳ衛星１０_ｊの観測量に含まれる誤差を推定し、当該推定した誤差レベルを表す指標値（例えば分散）を重み付け行列の対角成分に用いて、重み付け測位演算が実行されてもよい。
ここで、上記の数５の左辺の観測量に関して、擬似距離ρ_ｊ（ｉ）及び衛星−車両間距離ｄ_ｊ（ｉ）のいずれが用いられるかは、今回周期（ｉ）のモードに依存する。即ち、今回周期（ｉ）のモードが通常モードである場合、擬似距離ρ_ｊが用いられ、今回周期（ｉ）のモードがマルチパスモードである場合、衛星−車両間距離ｄ_ｊ（ｉ）が用いられる。したがって、測位演算部２１４は、マルチパス検出部２０６によりマルチパスの発生が検出されていない各周期（ｉ）では、擬似距離ρ_ｊを観測量として用いて測位演算を行う一方、マルチパス検出部２０６によりマルチパスの発生が検出されている各周期（ｉ）では、衛星−車両間距離ｄ_ｊ（ｉ）を観測量として用いて測位演算を行う。

Note that c · ΔT represents a clock error in the GPS receiver 20. In this case, for example, when the number of GPS satellites 10 _j used for positioning is four, four formulas are established, and thus positioning without clock error c · ΔT is realized. At this time, an error included in the observation amount of the GPS satellite 10 _j is estimated, and an index value (for example, variance) representing the estimated error level is used as a diagonal component of the weighting matrix to perform weighted positioning calculation. May be.
Here, with respect to the observed amount on the left side of Equation 5, whether the pseudo distance ρ _j (i) or the satellite-vehicle distance d _j (i) is used depends on the mode of the current cycle (i). . That is, when the mode of the current cycle (i) is the normal mode, the pseudo distance ρ _j is used, and when the mode of the current cycle (i) is the multipath mode, the satellite-vehicle distance d _j (i) is Used. Therefore, the positioning calculation unit 214 performs the positioning calculation using the pseudo distance ρ _j as an observation amount in each period (i) where the occurrence of multipath is not detected by the multipath detection unit 206, while the multipath detection unit In each period (i) in which the occurrence of multipath is detected by 206, positioning calculation is performed using the satellite-vehicle distance d _j (i) as an observation amount.

FIG. 7 is a diagram schematically illustrating a variation mode of the pseudo distance ρ _j when the multipath occurs and a variation mode of the Doppler frequency Δf _j when the multipath occurs. 7, each calculated value of the pseudorange [rho _j and Doppler frequency Delta] f _j (each observation) are shown in solid lines, the true value of the pseudorange [rho _j and Doppler frequency Delta] f _j is indicated by the dashed line .

When a multibus occurs, the correlation peak related to the direct wave does not appear clearly in the correlation value characteristic of the received wave, so that it becomes difficult to detect the code phase that takes the correlation peak value. As a result, the code phase tracking ( The accuracy of code synchronization will deteriorate. Such a problem can also occur in a configuration in which the tracking method is varied when a multibus is generated and the accuracy of code phase tracking is increased to some extent. Therefore, pseudorange [rho _j, as shown in the upper part of FIG. 7, at time t = t3 the time t = t2 and multipath multipath occurs is complete, time rate of change of pseudorange [rho _j is large variation To do. That is, the pseudo-range ρ _j has an error with respect to the true value rapidly increasing at the time t = t2 when the multipath occurs due to the deterioration of the accuracy of the code phase tracking. On the other hand, since the Doppler frequency Δf _j is not affected by the multipath, the error with respect to the true value does not increase even at the time t = t2 when the multipath occurs.

In this embodiment, paying attention to this point, as described above, when the occurrence of a multibus is detected, a multipath mode is formed, and a satellite based on the Doppler frequency Δf _j is used instead of the pseudorange ρ _j. Since the inter-vehicle distance _dj is used for the positioning calculation, it is possible to prevent the deterioration of the positioning accuracy that may occur when the multibus is generated.

Example 2, with respect to Example 1 above, primarily satellites in the multi-pass mode - mode of calculating the inter-vehicle distance d _j are different. In the following, only processing unique to the second embodiment will be described. Other configurations and processes may be the same as those in the first embodiment, and the definitions of various terms are the same as those in the first embodiment.

  FIG. 8 is a flowchart illustrating a flow of main processes realized in the GPS receiver 20 according to the second embodiment. The processing routine shown in FIG. 8 is repeatedly executed at predetermined intervals, for example, from when the ignition switch of the vehicle 90 is turned on to after it is turned off, similarly to the processing routine of FIG. The predetermined period may correspond to the observation period described above.

  In step 500, the counter is initialized. That is, the value of the counter is set to “1”.

  In step 502, based on the detection result of the current cycle by the multipath detection unit 206, it is determined whether or not a multipath has occurred in the current cycle. If a multipath has occurred in the current cycle, the process proceeds to step 503. Otherwise, the process proceeds to step 514.

  In step 503, the mode switching unit 208 forms a multipath mode.

  In step 504, it is determined whether or not the current counter value is "1". If the value of the counter is “1” (that is, if it is the first cycle in which multipath is detected), the process proceeds to step 506, otherwise (that is, if the value of the counter is greater than 1). Go to step 508.

In step 506, the satellite-vehicle distance calculation unit 212 calculates the distance change amount Δd _j (i) of the current cycle (i) in the calculation manner described in the first embodiment.

  In step 508, the counter value is incremented by "1".

In step 510, the satellite-to-vehicle distance calculation unit 212 calculates the distance change Δd _j (i) of the current cycle (i) from the pseudo-distance ρ _j (i) of the current cycle obtained from the filter 205. It is calculated by subtracting the distance ρ _j (i−1). That is, the distance change amount Δd _j (i) of the current cycle (i) is calculated by Δd _j (i) = ρ _j (i) −ρ _j (i−1).

In step 512, the satellite-to-vehicle distance calculation unit 212 calculates the satellite-to-vehicle distance d _j (i) in the current cycle using the distance change Δd _j (i) calculated in step 506 or 510. Is done. If the current cycle is the first cycle in which a multipath is detected, the satellite-to-vehicle distance d _j (i) is expressed as d _j (i) = ρ _j (i−1) + Δd _j (i ) And when the multipath is detected even in the previous cycle of the current cycle, the satellite-vehicle distance d _j (i) is calculated as d _j (i) = d _j (i−1) + Δd _j It is calculated by (i).

  In this way, the processing of steps 503 to 512 (however, the processing of step 506 is only the first time) is repeatedly executed continuously while the multipath is detected. At this time, the value of the counter represents the number of periods in which the multipath mode is continuously continued.

  In step 514, it is determined whether the current counter value is greater than one. That is, it is determined whether or not the previous cycle was the multipath mode. If the current counter value is larger than 1, if the previous cycle was the multipath mode, the process proceeds to step 516. In other cases (that is, when the current counter value is “1”), the process proceeds to step 520.

In step 516, the multipath mode is maintained, and the satellite-vehicle distance calculation unit 212 calculates the distance change amount Δd _j (i) in the current cycle (i) in the same calculation manner as in step 506.

In step 518, the satellite-to-vehicle distance calculation unit 212 uses the distance change amount Δd _j (i) calculated in step 516 to obtain d _j (i) = d _j (i−1) + Δd _j (i ) To calculate the satellite-vehicle distance d _j (i) in the current cycle. When the processing in step 518 is completed, the processing routine for the next cycle starts from step 500. As a result, the counter is initialized in the next cycle.

  In step 520, the mode switching unit 208 forms a normal mode.

Incidentally, as described above, the satellite-to-vehicle distance d _j based on the Doppler frequency Δf _j is different from the pseudorange ρ _j and has characteristics that are not easily affected by multipath, but is included in the observed value of the Doppler frequency Δf _j. Includes errors due to bias components. The error due to the bias component is not so large per se, but if the multipath mode continues for a long period of time, the error due to the bias component is accumulated accordingly, and there is a possibility that the positioning accuracy is deteriorated. is there. On the other hand, the difference value of the pseudo distance ρ _j between the periods has a characteristic that an error becomes large at the start of multipath (and at the end of multipath) as described above (see FIG. 7). In the period from the start to the end, the difference value of the pseudo distance ρ _j between the periods has a characteristic that the influence of the multipath is canceled by the difference, so that it is difficult to be affected by the multipath.

In this embodiment, paying attention to this point, the satellite-to-vehicle distance d based on the Doppler frequency Δf _j is used instead of the pseudorange ρ _j in the cycle at the start of the multipath and the cycle at the end of the multipath. _{While j} is used for the positioning calculation, in the period from the start to the end of the multipath, the difference value of the pseudo distance ρ _j between each period is used for the positioning calculation. As a result, it is possible to realize a positioning calculation that is less susceptible to multipath while preventing the accumulation of errors due to the bias component, and the positioning accuracy is improved.

  The following modifications can be considered for the embodiment described above.

  For example, in this embodiment, the normal mode may be immediately restored in the cycle at the end of multipath. That is, the processing of step 520 may be executed when the processing of steps 514, 516, and 518 of FIG. 8 is eliminated and a negative determination is made at step 502 of FIG.

In the above-described embodiment, the satellite-to-vehicle distance d _j based on the Doppler frequency Δf _j is used in one cycle at the start of the multipath, but the accumulated error due to the bias component has an allowable level. As long as it does not exceed, the satellite-to-vehicle distance d _j based on the Doppler frequency Δf _j may be used at the start of the multipath and in a plurality of periods thereafter. That is, in step 504 of FIG. 8, it may be determined whether or not the counter value is greater than a predetermined value. If the counter value is greater than the predetermined value, the process may proceed to step 508. In this case, the predetermined value is a value of 2 or more, and is a value adapted so that the accumulation of errors due to the bias component does not exceed the allowable level.

  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, when the distance change amount Δd _j (i) of the current cycle (i) is calculated in the situation where the previous cycle (i−1) is the normal mode, the initial value is obtained from the filter 205. The previous value ρ _j (i−1) of the pseudo distance ρ _j is used, but the present invention is not limited to this. For example, as shown in the following equation (3), the distance _{r j} between the vehicle 90 and the GPS satellites 10 _j, the previous period (i-1) positioning result of _{(X u (i-1)} , Y u ( i−1), Z _u (i−1)) and the position S _j = (X _j (i−1), Y _j (i−1), Z of the GPS satellite 10 _{j in} the previous period (i−1). _j (i-1)), and the derived distance r _j may be used as an initial value.

この際、前回周期（ｉ−１）の測位結果（Ｘ_ｕ（ｉ−１），Ｙ_ｕ（ｉ−１），Ｚ_ｕ（ｉ−１））は、上述の測位演算部２１４における衛星航法による測位演算で得られたものでなく、慣性航法のような他の測位方法で得られたものであってよい。

At this time, the positioning results (X _u (i−1), Y _u (i−1), Z _u (i−1)) of the previous cycle (i−1) are obtained by the satellite navigation in the positioning calculation unit 214 described above. It may not be obtained by positioning calculation, but may be obtained by other positioning methods such as inertial navigation.

  In the above description, as a preferred embodiment, filter processing such as carrier smoothing is performed in the normal mode. However, such filter processing may be omitted.

In the above-described embodiment, the pseudorange ρ is derived using the C / A code in the normal mode. However, the present invention is based on the P code of the L1 wave and / or the P code of the L2 wave, Similarly, the present invention can be applied to a configuration for calculating the pseudorange ρ with respect to the GPS satellite 10. In the case of a P code, since it is encrypted with a W code, when performing P code synchronization, the P code may be extracted by a DLL using a cross correlation method. The pseudo distance ρ _j based on the P code is determined by measuring whether the M _P bit of the P code is received by the vehicle 90 on the assumption that the P code is the 0th bit in the GPS satellite 10 _j , so that ρ _j = M It can be determined as _P × 30.

  In the above-described embodiment, an example in which the present invention is applied to the GPS has been shown. However, the present invention can also be applied to a satellite system below the GPS, for example, another GNSS (Global Navigation Satellite System) such as Galileo. is there.

It is a figure which shows the whole system. 2 is a block diagram illustrating an example of a main configuration of a GPS receiver 20. FIG. 3 is a block diagram illustrating an example of a main configuration of a DLL 203 of the GPS receiver 20. FIG. It is a figure which shows typically a multipath generation | occurrence | production situation. It is a conceptual diagram for demonstrating the other multipath detection method. 5 is a flowchart illustrating a mode switching method by a mode switching unit 208. And variation mode of the multipath pseudorange incurred ρ _{j (i),} is a diagram schematically showing a variation mode of the Doppler frequency Delta] f _j at the time of the multipath occurs. 10 is a flowchart showing a flow of main processing realized in the GPS receiver 20 according to the second embodiment.

Explanation of symbols

20 GPS receiver 90 vehicle 201 high frequency circuit 202 A / D conversion circuit 203 DLL
204 PLL
205 Filter 206 Multipath Detection Unit 208 Mode Switching Unit 209 Satellite Position Calculation Unit 212 Satellite-Vehicle Distance Calculation Unit 214 Positioning Calculation Unit

Claims (6)

In a mobile positioning device that receives satellite radio waves from a satellite by a mobile body and measures the position of the mobile body,
A pseudo-range calculating means for calculating a pseudo-range between the satellite and the moving body based on the code phase of the signal carried on the satellite radio wave;
The initial value of the distance between the satellite and the moving object is multiplied by the amount of change in the distance between the satellite and the moving object (hereinafter referred to as the distance change amount) obtained from the observation value of the satellite radio wave. A distance calculating means for calculating a distance between the satellite moving bodies;
Mode switching means for switching between a first distance calculation mode by the pseudo distance calculation means and a second distance calculation mode by the inter-satellite moving distance calculation means;
A synthetic wave detecting means for detecting reception of a synthetic wave composed of a direct wave of a satellite radio wave and a reflected wave thereof;
The mode switching means switches from the first distance calculation mode to the second distance calculation mode when reception of the synthesized wave is detected by the synthesized wave detecting means. .   2. The positioning for a moving body according to claim 1, wherein the inter-satellite moving body distance calculating means uses, as the initial value, a pseudo distance calculated by the pseudo distance calculating means before reception of the combined wave is detected. apparatus.   The inter-satellite moving distance calculating means calculates the distance change amount based on the observed value of the Doppler frequency of the satellite radio wave in the first period in which the reception of the composite wave is detected, while The mobile positioning device according to claim 1, wherein the distance change amount is calculated as a difference value between the pseudo distances calculated by the pseudo distance calculation means in each cycle from a predetermined cycle. In a mobile positioning method for receiving satellite radio waves from a satellite by a mobile body and positioning the position of the mobile body,
A pseudo-range calculation step for calculating a pseudo-range between the satellite and the moving body based on the code phase of the signal carried on the satellite radio wave;
The initial value of the distance between the satellite and the moving object is multiplied by the amount of change in the distance between the satellite and the moving object (hereinafter referred to as the distance change amount) obtained from the observation value of the satellite radio wave. A distance calculation step between satellite moving bodies for calculating the distance between
A combined wave detection stage for detecting reception of a combined wave composed of a direct wave of a satellite radio wave and a reflected wave thereof at a predetermined period;
A step of positioning the position of the moving body using the inter-satellite moving body distance calculated in the satellite moving body distance calculating step when reception of the combined wave is detected in the synthetic wave detecting stage. A positioning method for a mobile object, characterized in that   5. The pseudo-distance calculated in the pseudo-range calculation step before the period in which the reception of the synthetic wave is detected in the synthetic wave detection step is used as the initial value in the satellite mobile object distance calculation step. The positioning method for moving bodies described in 1.   When reception of the composite wave is detected in a continuous cycle in the composite wave detection step, in the initial cycle in which reception of the composite wave is detected in the inter-satellite mobile unit distance calculation step, the distance change amount Is calculated on the basis of the observed value of the Doppler frequency of the satellite radio wave, while the difference in the pseudo distances calculated in each period of the pseudo distance calculation stage from the predetermined period after the first period is calculated. The positioning method for a moving body according to claim 4, wherein the positioning method is calculated as a value.

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