JP4525689B2 - Measuring device for moving objects - Google Patents

Description

The present invention relates to a mobile measurement device for measuring the position of the moving body.

Conventionally, user position and clock offset in geocentric Cartesian coordinate system obtained from simultaneous position equation, Cartesian coordinate value of satellite position at measurement time calculated from orbit parameters obtained from measurement satellite, and previous measurement time Or the satellite speed obtained by dividing the difference between the current position and the Cartesian coordinate value of the satellite position at the time before ΔT by the previous measurement time interval TI or ΔT and the measured value of the pseudo range rate. There is known a technique for calculating a user speed and a time offset rate in a geocentric Cartesian coordinate system using the other simultaneous velocity equation assembled by using (see, for example, Patent Document 1).
Japanese Patent No. 2996312

By the way, in GPS measurement , generally, the position of a moving body is measured based on the reception results of signals from a plurality of satellites. At this time, since the propagation path of the radio wave from the satellite to the moving body is different for each satellite, the measurement value (for example, pseudo distance) measured based on the signal from each satellite may include an error different for each satellite. For this reason, when performing measurement , weighting may be performed for each satellite. Conventionally, the weighting coefficient used for such weighting is often determined by factors such as the residual at the time of the previous measurement , the difference in elevation angle of each satellite, and the difference in received intensity of signals from each satellite. However, the weighting coefficient determined in this way may not appropriately reflect a different error for each satellite.

Accordingly, the present invention has an object to provide a mobile measurement device capable of performing a weighting operation with appropriately reflects the different error for each satellite.

In order to achieve the above object, a first invention provides a measuring apparatus for a moving body that measures the position of a moving body by observing the phase of a pseudo noise code carried on a satellite radio wave with the moving body.
Pseudo-range measuring means for measuring, for each satellite, a pseudo-range between the satellite and the moving body when the moving body is stopped, using the observed value of the phase acquired while the moving body is stopped;
An error index value calculating means for calculating an index value representing an error of the measured pseudo distance for each satellite based on the pseudo distance measured by the pseudo distance measuring means at a plurality of times when the moving body is stopped; ,
Weighting factor determining means for determining a weighting factor for each satellite based on the error index value for each satellite calculated by the error index value calculating means;
Measurement that measures the position of a moving body by moving using a weighting coefficient for each satellite determined by the weighting factor determination means, using the observed value of the phase acquired during movement of the moving body Means ,
Based on the pseudoranges measured by the pseudorange measuring means at a plurality of times while the moving body is stopped, an error average value calculating means for calculating an average value of errors of the measured pseudoranges for each satellite; Prepared,
The measurement means performs the measurement using the observed value of the phase corrected by the error average value calculated by the error average value calculation means .

2nd invention is the measuring apparatus for moving bodies which concerns on 1st invention,
The index value is variance or standard deviation.

According to the present invention, the mobile measurement device capable of performing a weighting operation with appropriately reflects the different error for each satellite is 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 moving body position measuring apparatus 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 the vehicle-mounted device 1 as a moving body position measuring device.

  FIG. 2 is a block diagram showing the main configuration of the vehicle-mounted device 1. As shown in FIG. 2, the vehicle-mounted device 1 includes a GPS receiver 20 and a vehicle stop determination unit 40 as main components. The main functions of the GPS receiver 20 will be described later.

  The vehicle stop determination unit 40 determines whether or not the vehicle 90 is stopped. There are a wide variety of such determination methods, and any appropriate method may be adopted. For example, the vehicle stop determination unit 40 may determine whether or not the vehicle is stopped based on an output signal (differential value or the like) of an acceleration sensor or an angular velocity sensor mounted on the vehicle 90. Alternatively, the vehicle stop determination unit 40 may determine whether or not the vehicle is stopped based on an output signal of a wheel speed sensor mounted on the vehicle 90. The vehicle stop determination unit 40 may output signals from other in-vehicle sensors that can output a physical quantity related to the vehicle speed, such as a sensor that measures the rotation speed of the output shaft of the transmission instead of or in addition to the wheel speed sensor. Further, it may be determined whether or not the vehicle is stopped by using an output signal of a sensor that detects an operation state of the brake pedal, a shift position, or the like.

FIG. 3 shows an example of the internal configuration of the GPS receiver 20. Hereinafter, to avoid complicating the description, it will be described as a representative signal processing relating satellite signals from one single GPS satellite 10 ₁ (1-channel signal processing). The signal processing described below is executed in parallel (simultaneously) with respect to the satellite signals from the observable GPS satellites 10 ₁ , 10 ₂ , 10 _3, etc. for each observation period (for example, 1 ms).

The GPS receiver 20 includes a GPS antenna 21, a high-frequency circuit 22, an A / D (analog-to-digital) conversion circuit 24, a DLL (Delay-Locked Loop) 110, a PLL (Phase-Locked Loop) 120, a satellite position calculation unit. 124 and a filter 130. The DLL 110 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 code generation unit 117, a pseudo distance calculation unit 118, And the measurement part 50 is included.

GPS antenna 21 receives a hygienic signal transmitted from the GPS satellite 10 _1, the voltage signal satellite signal received (in this example, frequency 1.5 GHz) is converted to. A voltage signal of 1.5 GHz is referred to as an RF (radio frequency) signal.

  The high-frequency circuit 22 amplifies a weak RF signal supplied via the GPS antenna 21 to a level at which A / D conversion can be performed later, and at the same time, an intermediate frequency (typically 1 MHz to 20 MHz). A signal obtained by down-converting the RF signal in this way is referred to as an IF (Intermediate frequency) signal.

The A / D conversion circuit 24 converts the IF signal (analog signal) supplied from the high frequency circuit 22 into a digital IF signal so that digital signal processing can be performed. The digital IF signal is supplied to the DLL 110, the PLL 120, and the like.

The replica C / A code generation unit 117 of the DLL 110 generates a replica C / A code. The replica C / A code with respect to the C / A code, which is put on the satellite signals from the GPS satellites 10 _1, + 1, the arrangement of -1 is the same code.

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 ₁ .

  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 120 by a mixer (not shown).

The cross-correlation calculation 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 ₁ . 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 phase delay amount delayed by the phase delay unit 114 is the same as the phase advance amount θ ₁ but has a different sign.

  Further, the digital correlation signal is input to the cross-correlation calculation unit 112 after being multiplied by a replica carrier generated by the PLL 120 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 ₁ . The Late correlation value L _CA is calculated by the following equation, for example.
Late correlation value L _CA1 = Σ {(digital IF) × (Late replica code)}
In this way, the cross-correlation calculation units 111 and 112 execute the correlation value calculation with the correlator interval d ₁ (also referred to as “spacing”) being 2θ ₁ . 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.

In pseudorange calculation unit 118, based on the phase information of the replica C / A code generated by the C / A code replica generator 117, pseudo-range [rho _'1 is, for example, is calculated by the following equation. As the meaning of the code, “′” added to the pseudorange ρ indicates that the filtering process described later is not executed, and the subscript “ ₁ ” indicates the C / A code related to the GPS satellite 10 _1. The pseudo distance ρ calculated based on
ρ ′ ₁ = N ₁ × 300
Here, _{N 1} is, C / A code corresponds to the number of bits, the phase and the reception of the replica C / A code generated by the C / A code replica generation unit 117 between the GPS satellite 10 ₁ and the vehicle 90 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 ′ ₁ calculated in this way is input from the DLL 110 to the filter 130.

In the PLL 120, the Doppler frequency Δf _{1 of} the Doppler-shifted received carrier wave (received carrier) is measured using a carrier replica signal generated inside. In other words, the PLL 120 measures the Doppler frequency Δf ₁ (= fr−f _L1 ) based on the replica carrier frequency fr and the known carrier frequency f _L1 (1575.42 MHz). The digital IF signal input to the PLL 120 is obtained by multiplying the replica C / A code supplied from the DLL 110 by a mixer (not shown). A signal representing the Doppler frequency Δf ₁ from the PLL 120 is input to the filter 130 and the measurement unit 50.

In the filter 130, the filter processing of the pseudo distance ρ ′ ₁ is executed using the Doppler frequency Δf ₁ . In the filter 130, for example according to the following arithmetic expression, pseudorange [rho ₁ after filtering are computed.

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. Further, [Delta] V is the relative velocity between the GPS satellite 10 ₁ and the vehicle 90 (Doppler velocity), for example using the following equation is calculated.
Δf _L1 = ΔV · f _L1 / (c−ΔV)
C is the speed of light. The filter processing expressed by Equation 1 may be processing known as carrier smoothing known in this field, and can be realized by using a Kalman filter in addition to the hatch filter described above. A signal representing the pseudo distance ρ ₁ from the filter 130 is input to the measurement unit 50.

Satellite position calculation unit 124, based on the satellite orbit information of the navigation message, the GPS satellite 10 _1, the current position in the world coordinate system _{S 1 = (X 1, Y} 1, Z 1) and the moving speed _V 1 = ( V ₁ , V ₁ , V ₁ ) are calculated. The satellite moving speed vector V ₁ = (V ₁ , V ₁ , V ₁ ) may be calculated by dividing the difference between the calculated current value and the previous value of the satellite position S ₁ by the time width of the calculation cycle. The satellite position S ₁ and the satellite moving velocity vector V ₁ derived by the satellite position calculation unit 124 in this way are input to the measurement unit 50.

Next, details of the measurement unit 50 of the present embodiment will be described.

FIG. 4 is a block diagram illustrating a main configuration of the measurement unit 50 according to the present embodiment. As shown in FIG. 4, the measurement unit 50 according to the present embodiment includes a σ _v calculation unit 42, a d _ave calculation unit 44, a σ _d calculation unit 46, a weight matrix generation unit 48, and a weighting calculation unit 49. The function of each part 42, 44, 46, 48, 49 is demonstrated referring FIG.5 and FIG.6.

FIG. 5 is a flowchart illustrating an example of the vehicle position measurement process realized by the measurement unit 50 of the present embodiment. The processing routine shown in FIG. 5 is repeatedly executed at predetermined intervals, for example, from when the ignition switch of the vehicle 90 is turned on to when it is turned off. 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, it is determined whether or not the vehicle 90 is currently stopped based on the determination result from the vehicle stop determination unit 40. If the vehicle is stopped, the process proceeds to step 504. As such a situation, typically, a situation before the start of vehicle travel after engine start, or a situation where the vehicle 90 temporarily stops due to a signal waiting after the start of vehicle travel is assumed. On the other hand, if the vehicle 90 is moving, the process proceeds to step 514.

  In step 504, it is determined whether or not the current counter value is "1". If the value of the counter is “1”, the process proceeds to step 506, otherwise (ie, if the counter value is greater than 1), the process proceeds to step 508.

In step 506, the position (X _u , Y _u , Z _u ) of the vehicle 90 based on the latest measurement result is stored as the vehicle position u ₀ = (X _u0 , Y _u0 , Z _u0 ) immediately after the stop. The vehicle position u ₀ = (X _u0 , Y _u0 , Z _u0 ) immediately after the stop may be derived by a weighting calculation described later, or derived by another measurement method (for example, inertial navigation). It may be. In addition, when inertial navigation is used, the inertia using the vehicle position corrected by matching the map data including the known position information of the road sign and the image recognition result of the road sign using the in-vehicle camera as the initial position. Navigation is preferred.

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

In step _510, the _{d ave} calculator 44, the average value _{d Ave_j} errors in pseudorange [rho _j (hereinafter, "distance error average value _{d Ave_j"} hereinafter) is, GPS satellite 10 _j for the current observable GPS satellites 10 _j Calculated every time. The subscript “ _j ” corresponds to the satellite number (j = 1, 2, 3, 4,...) Of the GPS satellite 10 that can be observed at present, and represents a value for each GPS satellite 10. . Here, it should be noted that the distance error average value d _{ave — j} is an average value of errors of the pseudo distance ρ _j observed in the stopped state. The distance error average value d _{ave — j} is calculated as follows, for example.

Here, n is the number of data, and in this example, n = (counter value). d _j (i) represents an error of the pseudo distance ρ _j (i) detected in the i-th cycle, where the first cycle in which the stop is detected is the first. For example, d _j (i) is calculated as follows using the fact that the measurement result immediately after the stop has the highest position accuracy.

Here, (X _j (i), Y _j (i), Z _j (i)) represents the satellite position calculated in the i-th cycle, and the satellite in the cycle corresponding to the i-th cycle as described above. The satellite position S _j calculated by the position calculation unit 124 is used. (X _u0 , Y _u0 , Z _u0 ) represents the vehicle position u ₀ immediately after the stop stored in step 506. Similarly, ρ _j (i) represents the pseudorange ρ _j calculated for the GPS satellite 10 _j in the i-th period. c · ΔT represents a clock error in the GPS receiver 20. As c · ΔT, a value obtained at the time of measurement by a weighting calculation unit 49 described later may be used.

In step 512, the standard deviation value σ _{d_j} of the error of the pseudorange ρ _j (hereinafter referred to as “distance error standard deviation value σ _{d_j} ”) calculated by the σ _d calculation unit 46 for the GPS satellite 10 _j that can be observed at present is obtained. , Calculated for each GPS satellite 10 _j . Similarly, it should be noted here that the distance error standard deviation value σ _{d — j} is the standard deviation value of the error of the pseudo distance ρ _j observed in the stopped state. For the distance error standard deviation value σ _{d — j} , for example, the following relational expression is calculated.
^{_{σ d_j 2 = Σ (d j}} (i) -d ave_j) 2 / n
Incidentally, sigma _{d_j} ² represents the variance of the error _{d j} pseudorange [rho _j. The distance error standard deviation value σ _{d_j} may be calculated using the values d _j (i) and d _{ave_j} calculated by the d _ave calculation unit 44.

In this way, while the vehicle 90 is stopped, the processing of step 508 and step 510 is repeated, and based on the data observed at any time while the vehicle 90 is stopped, the distance error average value d _{ave — j} and The distance error standard deviation value σ _{d — j} is calculated for each GPS satellite 10 _j at predetermined intervals. Obviously, the distance error average value d _{ave_j} and the distance error standard deviation value σ _{d_j} are reliable because the number of samples increases as the number of periods i increases while the vehicle 90 is stopped. Get higher. The distance error average value d _{ave_j} and the distance error standard deviation value σ _{d_j} calculated while the vehicle 90 is stopped in this way are calculated in Steps 514 to 518 described below. It is effectively used for measuring the position of the vehicle 90 after the start.

In step 514, it is determined whether the counter is greater than a predetermined threshold. This determination is to determine whether the distance error average value d _{ave_j} and the distance error standard deviation value σ _{d_j} calculated while the vehicle 90 is stopped are reliable. It may be set appropriately from the viewpoint. For example, the predetermined threshold value may be any value between 11 and 21 corresponding to the number of samples of 10 to 20 or more. If the counter is greater than the predetermined threshold, the process proceeds to step 516. Counter (if for example stoppage time is very short) in the case of less than a predetermined threshold value, the vehicle 90 is to the calculated distance error Mean value of d _{Ave_j} and distance error standard deviation sigma _{d_j} between which stop It is determined that the reliability is low, and the processing routine of the current cycle ends (return to step 500).

In step 516, the weight matrix generation unit 48 _performs weighting based on the distance error average value d _{ave — j} and the distance error standard deviation value σ d — _j calculated in the above steps 510 and 512 in the last period during the previous stop. Each component of the matrix W is determined. The weighting matrix W is zero except for the diagonal component, and the distance error standard deviation value σ _{d_j} calculated by the σ _d calculating unit 46 as described above is substituted for the diagonal component. Hereinafter, for convenience of explanation, it is assumed that four GPS satellites 10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ can be observed at present. In this case, the weighting matrix W is as follows.

In step 518, the weighting calculation unit 49, the pseudorange [rho ₁ were observed in this _period, [rho _2, [rho _3, based on the [rho _4, the weighting operation using a weighting matrix W generated in the above steps 516 , the current position of the vehicle _{90 (X u, Y u,} Z u) is measured. The weighting operation is executed using, for example, the following weighted least square method.

First, as a premise, the following relational expressions hold among the pseudo distance ρ _j , the satellite position (X _j , Y _j , Z _j ), and the vehicle position (X _u , Y _u , Z _u ).

Here, b = c · ΔT is set, and the general expression of the approximate expression obtained by linearizing the expression of Expression 5 with each state quantity, where the unknown quantity is (X _u , Y _u , Z _u , b) is the state quantity η, It becomes as follows.

Here, if an appropriate initial value of the state quantity η is (0, 0, 0, 0), Δρ _j is as follows.

The partial differential term is as follows.

Therefore, when Δρ _j is an observation quantity z _j , the relationship between the observation quantity z _j and the state quantity η is as follows using the observation matrix H.
z _j = H · η ^T
Here, the observation amount z and the observation matrix H are as follows for the four GPS satellites 10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ .

Accordingly, the state quantity η is obtained using the weighting matrix W as follows.

Here, in the above weighting operation, preferably, observable z _j, rather than using the pseudorange [rho _j as those obtained by correcting the pseudo range [rho _j distance error average value d _{Ave_j} is used. That is, a preferable observation amount z _j is as follows.

The measurement result of the position (X _u , Y _u , Z _u ) of the vehicle 90 obtained in this way may be output to, for example, a navigation system.

In step 520, it is determined whether or not the vehicle 90 has changed from the moving state to the stopped state based on the determination result from the vehicle stop determining unit 40. When the vehicle 90 changes from the moving state to the stopped state, the process returns to Step 500, and otherwise (ie, when the vehicle 90 is moving), the process proceeds to Step 518. That is, the process of step 518 is continuously executed based on the pseudo distance ρ _j and the satellite position (X _j , Y _j , Z _j ) that are observed at any time while the vehicle 90 is moving.

When the observable GPS satellite 10 changes during the movement of the vehicle 90, the weighting matrix W may be re-determined accordingly. For example, when a certain GPS satellite 10 _k becomes unobservable, a weighting matrix W excluding components related to the GPS satellite 10 _k is created, and accordingly, an observation amount z _k related to the GPS satellite 10 _k is calculated. The above-described weighting calculation may be executed based on the observation amount z _j related to the other GPS satellites 10 _j excluded. Also, if a new GPS satellite 10 _k (GPS satellite 10 _k which has not been observed while the vehicle 90 is stopped) was observed for such new GPS satellites 10 _k, distance error Mean value Since d _{ave_k} and distance error standard deviation value σ _{d_k} are not calculated, the above-described weighting calculation may be executed using an appropriate initial value of the weighting coefficient (diagonal component of the weighting matrix).

According to the vehicle position measurement process shown in FIG. 5 described above, as described above, the distance error average value d _{ave — j} used as the weighting coefficient of the weighting matrix W is the same as that of each GPS satellite 10 _j while the vehicle 90 is stopped. Since the calculation is based on the observation data, the weighting coefficient of the weighting matrix W with high reliability can be set. This is included in the observation data of each GPS satellite 10 _j (especially the observation value of the pseudorange ρ _j ) because it is not affected by the error factor caused by the movement of the vehicle 90 while the vehicle 90 is stopped. This is because the error can be evaluated with high accuracy for each GPS satellite 10 _j . As described above, according to the vehicle position measurement process shown in FIG. 5, the vehicle 90 is moving by setting the weighting matrix W with high accuracy by using the fact that the vehicle position does not change while the vehicle 90 is stopped. A highly accurate measurement result can be obtained.

Further, as described above, since the weighting calculation is executed by correcting the pseudo distance ρ _j with the distance error average value d _{ave — j} , a highly accurate measurement result can be obtained. That is, by removing the error included in the pseudo distance ρ _j by the distance error average value d _{ave — j} , a highly accurate measurement result can be obtained. Further, since the distance error average value d _{ave — j} is calculated based on the observation data of each GPS satellite 10 _j while the vehicle 90 is stopped as described above, the accuracy is high and the accuracy of the measurement result is high. Further improvement can be achieved.

Incidentally, in the vehicle position measurement processing shown in FIG. 5 above, the diagonal elements of the weight matrix W, in place of the distance error standard deviation sigma _{d_j,} variance sigma _{d_j} ² error d _j pseudorange [rho _j is May be substituted.

FIG. 6 is a flowchart illustrating an example of a vehicle speed measurement process realized by the measurement unit 50 of the present embodiment. The processing routine shown in FIG. 6 is repeatedly executed at predetermined intervals, for example, from when the ignition switch of the vehicle 90 is turned on to when it is turned off. The predetermined period may correspond to the observation period described above. The processing routine shown in FIG. 6 is described separately from the processing routine shown in FIG. 5 described above, but may be executed separately in parallel, or may be executed by being integrated into an integrated processing routine. May be.

  In step 600, a counter is initialized. That is, the value of the counter is set to “1”.

  In step 602, it is determined whether the vehicle 90 is currently stopped based on the determination result from the vehicle stop determination unit 40. If the vehicle is stopped, the process proceeds to step 604. Otherwise (ie, when the vehicle 90 is moving), the process proceeds to step 614.

  In step 604, it is determined whether or not the current counter value is "1". If the counter value is “1”, the process proceeds to step 606; otherwise (ie, if the counter value is greater than 1), the process proceeds to step 608.

In step 606, the position (X _u , Y _u , Z _u ) of the vehicle 90 based on the latest measurement result is stored as the vehicle position u ₀ = (X _u0 , Y _u0 , Z _u0 ) immediately after the stop. The vehicle position u ₀ = (X _u0 , Y _u0 , Z _u0 ) immediately after the stop may be derived by the above-described weighting calculation or derived by another measurement method (for example, inertial navigation). It may be.

  In step 608, the counter value is incremented by "1".

In step 610, the σ _v calculation unit 42 first calculates a standard deviation value σ _{v_j} (hereinafter referred to as “speed standard deviation value σ _{v_j} ”) of the vehicle speed V _{u_j in} the line-of-sight direction of the vehicle 90 with respect to the GPS satellite 10 _j . Calculated for each GPS satellite 10 _j . Similarly, where it should be noted that the velocity standard deviation sigma _{V_j} is the standard deviation of the vehicle speed V _{U_j} observed in the stop state. For example, the following relational expression is calculated for the speed standard deviation value σ _{v — j} for the GPS satellite 10 _j .
^{_{σ v_j 2 = Σ (V u_j}} (i) -V ave_j) 2 / n
_{Incidentally,} σ v_j ² represents a variance value of the vehicle speed _{V u_j.} V _{u_j} (i) is a vehicle speed V _{u_j} related to the GPS satellite 10 _j calculated in the i-th cycle with the first cycle in which the stop is detected as the first cycle. V _{Ave_j} is an average value of _{V u_j} (i) in each cycle, for example, calculated as follows.

Here, n is the number of data, and in this example, n = (counter value). Note that V _{ave — j} may be zero using the fact that the vehicle 90 is stopped. In this case, the speed standard deviation value σ _{v_j} is substantially a standard deviation value of an error of the vehicle speed V _{u_j} .

Vehicle velocity _{V u_j} (i) includes a Doppler range dp _j (i) about the GPS satellite 10 _j, the unit vector in the viewing direction of the vehicle 90 with respect to the GPS satellites 10 _{j l j} (i), satellite mobile GPS satellites 10 _j Using the relationship with the velocity vector V _j = (V _j (i), V _j (i), V _j (i)), for example, it is calculated as follows.

Here, the Doppler range dρ _j (i) is obtained by using, for example, dρ _j (i) using the wavelength λ (known) of the carrier wave and the Doppler frequency Δf _j (i) related to the GPS satellite 10 _j obtained in the period (i). = Λ · Δf _j (i). In the above equation, l _j · V _j is an inner product of the unit vector l _j and the satellite moving velocity vector V _j . Unit vector _{l j} is the vehicle position _u immediately after stopping stored in the above step _{606 0 = (X u0, Y} u0, Z u0) and the position S of the GPS satellites _{10 j (i) = (X} j (i ), Y _j (i), Z _j (i)) and the distance r _j (i) between the vehicle 90 and the GPS satellite 10 _j are calculated as follows, for example.

_{Incidentally, r} j (i) are as follows.

In this way, the processing of step 608 and step 610 is repeated while the vehicle 90 is stopped, and the speed standard deviation value σ _{v_j} is determined based on the data observed at any time while the vehicle 90 is stopped. It is calculated for each GPS satellite 10 _j at predetermined intervals. Obviously, the speed standard deviation value σ _{v —} j becomes more reliable because the number of samples increases as the number of periods i while the vehicle 90 is stopped increases. The speed standard deviation value σ _{v — j} calculated while the vehicle 90 is stopped in this manner is the speed of the vehicle 90 after the vehicle 90 starts to move after the stop in steps 614 to 618 described below. It is effectively used for measurement .

In step 614, it is determined whether the counter is greater than a predetermined threshold. This determination is to determine whether the speed standard deviation value σ _{v_j} calculated while the vehicle 90 is stopped is reliable or not. If the predetermined threshold is appropriately set from this viewpoint, Good. For example, the predetermined threshold value may be any value between 11 and 21 corresponding to the number of samples of 10 to 20 or more. If the counter is greater than the predetermined threshold, the process proceeds to step 616. When the counter is equal to or smaller than a predetermined threshold (for example, when the stop time is very short), it is determined that the reliability of the speed standard deviation value σ _{v_j} calculated while the vehicle 90 is stopped is low. Then, the processing routine of the current cycle ends (return to step 600).

In step 616, the weight matrix generation unit 48 determines each component of the weighting matrix _{W_v} based on the speed standard deviation value σ _{v_j} calculated in step 610 in the last period during the previous stop. . The weighting matrix _{W_v} is zero except for the diagonal component, and the speed standard deviation value σ _{v_j} calculated by the σ _v calculating unit 42 as described above is substituted for the diagonal component. Hereinafter, for convenience of explanation, it is assumed that four GPS satellites 10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ can be observed at present. In this case, the weighting matrix _{W_v} is as follows.

In step 618, the weighting calculation unit 49, Doppler range dp ₁ were observed in this period, dp _2, dp _3, based on dp _4, the weighting operation using a weighting matrix _{W _v} generated in the above step 616 Thus, the current speed of the vehicle 90 v = (v _u , v _u , v _u ) is measured . The weighting operation is executed using, for example, the following weighted least square method.

First, as a premise, the following relational expression is established among the Doppler range dρ _j , the satellite moving speed vector V, and the speed vector v = (v _u , v _u , v _u ) of the vehicle 90. The symbol black circle on the letter represents a dot (time differentiation), for example, the Doppler range dρ _j is ρ _j dot (time differentiation).

Here, the I dot and the T dot represent the variation amount of the ionospheric error and the variation amount of the troposphere error, but are treated as white noise ε because they are very small. The b dot is a differential value of the clock error. Equation 17 can be modified as follows when observation data from _four GPS satellites 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ is used.

In the equation (18), the left side is an observation amount z. "Dp _j" of the observation amount _{z j} about GPS satellites 10 _j on the basis of the Doppler frequency Δf _j (i) as described above, is calculated by _{dρ j = λ · Δf j (} i). Further, _"l j · _{V j"} of the observation amount _{z j} about GPS satellites 10 _j is the inner product of the cycle unit in (i) vector _l j (i) and the satellite moving velocity vector _V j (i), the satellite The moving velocity vector V _j (i) is calculated based on the satellite orbit information of the navigation message by the satellite position calculation unit 124 as described above, and the unit vector l _j (i) is weighted as described above in the period (i). calculation unit 49 (FIG. 518 5) of the position of the vehicle 90 calculated by the measurement results using the _{(X u (i), Y} u (i), Z u (i)), as follows, May be calculated.

Then, the observation matrix G is set as follows.

The state quantity η is composed of the speed vector v = (v _u , v _u , v _u ) of the vehicle 90 and b dots. When η = (v, b dots) is set, the state quantity η is obtained from the weighting matrix _{W_v} . Using, it is obtained as follows.

The measurement result of the speed vector v of the vehicle 90 obtained in this way may be output to, for example, a navigation system.

In step 620, it is determined whether or not the vehicle 90 has changed from the moving state to the stopped state based on the determination result from the vehicle stop determination unit 40. If the vehicle 90 changes from the moving state to the stopped state, the process returns to Step 600. Otherwise (ie, when the vehicle 90 is moving), the process proceeds to Step 618. That is, the process of step 618 is continuously executed based on the Doppler range dρ _j and the satellite moving speed vector V _j that are observed as needed while the vehicle 90 is moving.

If the observable GPS satellite 10 changes during the movement of the vehicle 90, the weighting matrix _{W_v} may be determined again accordingly. For example, when a certain GPS satellite 10 _k becomes unobservable, a weighting matrix _{W_v} excluding a component related to the GPS satellite 10 _k is created, and accordingly, an observation amount z _k related to the GPS satellite 10 _k is created. The above-described weighting calculation may be executed based on the observation amount z _j related to the other GPS satellites 10 _j excluding. Also, if a new GPS satellite 10 _k (GPS satellite 10 _k which has not been observed while the vehicle 90 is stopped) was observed for such new GPS satellites 10 _k, the rate standard deviation Since σ _{v_k} has not been calculated, the above-described weighting calculation may be performed using an appropriate initial value of the weighting coefficient (diagonal component of the weighting matrix).

According to the vehicle speed measurement processing shown in FIG. 6 of the above, as described above, the weighting matrix W velocity standard deviation sigma _{V_j} used as weighting factors _{_v} is, each GPS satellite 10 _j while the vehicle 90 is stopped Therefore, the weighting coefficient of the highly reliable weighting matrix _{W_v} can be set. This is included in the observation data of each GPS satellite 10 _j (especially the observation value of the Doppler range dρ _j ) since it is not affected by the error factor caused by the movement of the vehicle 90 while the vehicle 90 is stopped. This is because the error can be evaluated with high accuracy for each GPS satellite 10 _j . As described above, according to the vehicle speed measurement process shown in FIG. 6, the vehicle position is not changed while the vehicle 90 is stopped (that is, the vehicle speed is zero while the vehicle 90 is stopped). By setting a high weighting matrix _{W_v} , a highly accurate measurement result can be obtained while the vehicle 90 is moving.

In the vehicle speed measurement process shown in FIG. 6 described above, the variance value σ _{v — j} ² may be substituted for the diagonal component of the weight matrix W _— v instead of the speed standard deviation value σ _{v — j} .

  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 weighting coefficients of the weight matrices W and _{W_v} are other values such as a residual at the time of the previous measurement , a difference in elevation angle of each satellite, a difference in signal reception intensity from each satellite, and the like. It may be set in consideration of these factors.

In the above-described embodiment, the pseudo distance ρ is derived using the C / A code. However, the pseudo distance ρ may be measured based on another pseudo noise code such as an L2 wave P code. Good. 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 pseudorange [rho based on P-code, that M _P bit of P code to measure whether it is received by the vehicle 90 as P code GPS satellite 10 ₁ is bit 0, [rho _{'P =} 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 satellite systems other than GPS, for example, other GNSS (Global Navigation Satellite System) such as Galileo. is there.

1 is a system configuration diagram showing an overall configuration of a GPS to which a moving body measuring apparatus according to the present invention is applied. 2 is a block diagram illustrating a main configuration of the vehicle-mounted device 1. FIG. 2 is a diagram illustrating an example of an internal configuration of a GPS receiver 20. FIG. It is a block diagram which shows the main structures of the measurement part 50 of a present Example. It is a flowchart which shows an example of the vehicle position measurement process implement | achieved by the measurement part 50 of a present Example. It is a flowchart which shows an example of the vehicle speed measurement process implement | achieved by the measurement part 50 of a present Example.

DESCRIPTION _{OF SYMBOLS} 1 Onboard equipment 10 GPS satellite 20 GPS receiver 40 Vehicle stop determination part 42 (sigma) _v calculation part _44dave calculation part 46 (sigma) _d calculation part 48 Weight matrix generation part 49 Weighting calculation part 50 Measurement part 90 Vehicle

Claims (3)

In the moving body measuring apparatus for observing the phase of the pseudo noise code carried on the satellite radio wave with the moving body and measuring the position of the moving body,
Pseudo-range measuring means for measuring, for each satellite, a pseudo-range between the satellite and the moving body when the moving body is stopped, using the observed value of the phase acquired while the moving body is stopped;
An error index value calculating means for calculating an index value representing an error of the measured pseudo distance for each satellite based on the pseudo distance measured by the pseudo distance measuring means at a plurality of times when the moving body is stopped; ,
Weighting factor determining means for determining a weighting factor for each satellite based on the error index value for each satellite calculated by the error index value calculating means;
Measurement that measures the position of a moving body by moving using a weighting coefficient for each satellite determined by the weighting factor determination means, using the observed value of the phase acquired during movement of the moving body Means ,
Based on the pseudoranges measured by the pseudorange measuring means at a plurality of times while the moving body is stopped, an error average value calculating means for calculating an average value of errors of the measured pseudoranges for each satellite; Prepared,
The measuring device for a moving body , wherein the measuring unit performs the measurement using the observed value of the phase corrected by the error average value calculated by the error average value calculating unit . The measuring apparatus for moving bodies according to claim 1, wherein the index value is dispersion or standard deviation.   The error index value calculating means is configured to calculate the index value with reference to a pseudo distance related to a time immediately after the stop among pseudo distances measured by the pseudo distance measuring means at a plurality of times during the stop of the moving body. The measuring apparatus for a moving body according to claim 1, wherein the measuring apparatus is calculated.