WO2009115899A2 - Dispositif de positionnement d'un corps en déplacement et procédé de positionnement d'un corps en déplacement - Google Patents

Dispositif de positionnement d'un corps en déplacement et procédé de positionnement d'un corps en déplacement Download PDF

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Publication number
WO2009115899A2
WO2009115899A2 PCT/IB2009/000548 IB2009000548W WO2009115899A2 WO 2009115899 A2 WO2009115899 A2 WO 2009115899A2 IB 2009000548 W IB2009000548 W IB 2009000548W WO 2009115899 A2 WO2009115899 A2 WO 2009115899A2
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WIPO (PCT)
Prior art keywords
psr
computed
pseudorange
moving body
computing
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PCT/IB2009/000548
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English (en)
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WO2009115899A3 (fr
Inventor
Naoto Hasegawa
Hideaki Tampo
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Toyota Jidosha Kabushiki Kaisha
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Publication of WO2009115899A2 publication Critical patent/WO2009115899A2/fr
Publication of WO2009115899A3 publication Critical patent/WO2009115899A3/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/48—Determining position by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
    • G01S19/49—Determining position by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system whereby the further system is an inertial position system, e.g. loosely-coupled
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position

Definitions

  • the present invention relates to a moving body positioning device through which a moving body receives a radio wave from a satellite to determine the position of the moving body, and a moving body positioning method.
  • JP-A-2001-4734 discloses a GPS receiver that includes: a GPS antenna for receiving a satellite signal; a wave detecting section for computing a Doppler shifted frequency and a pseudorange from the received signal; a pseudorange estimating section for computing a rate of change in the pseudorange from the Doppler shifted frequency to estimate the pseudorange; and a positioning section for selectively using the computed pseudorange or the estimated pseudorange to determine the position of the GPS receiver.
  • the positioning section determines the position of the GPS receiver by using either the pseudorange that is computed by the wave detecting section when a radio wave from the satellite can be received or the pseudorange estimated by the pseudorange estimating section when the radio wave is blocked and thus the pseudorange cannot be computed.
  • the pseudorange estimating section computes a relative velocity between the satellite and the GPS receiver from the Doppler shifted frequency obtained in previous positioning process, and estimates the current pseudorange from the relative velocity and the pseudorange obtained in the previous positioning process.
  • the present invention provides a moving body positioning device with which highly accurate positioning can be achieved even when an error in a computed pseudorange is large, and also provides a moving body positioning method.
  • a moving body positioning device through which a moving body receives a radio wave from a satellite to determine the position of the moving body includes: PSR computing means for computing a pseudorange between the satellite and the moving body per given cycle based on an observed phase of a pseudo random noise code in a satellite wave; ADR computing means for computing an accumulated Doppler range (ADR) per given cycle based on an observed Doppler shifted frequency of the satellite wave; positioning means for determining the position of the moving body per given cycle based on the pseudorange that is computed by the PSR computing means; satellite position computing means for obtaining information representing a satellite position and computing the satellite position per given cycle; previous value PSR estimating means for computing an estimated value of the pseudorange in a previous cycle (an estimated previous value) based on a magnitude of a difference vector between a positioning result of the moving body in the previous cycle that is obtained from the positioning means and a computed result of the satellite position in the previous cycle that is obtained from the satellite position computing means;
  • the computing cycles of the ADR computing means and the PSR computing means are not necessarily be synchronized with the positioning cycle of the positioning means and the computing cycle of the satellite position computing means.
  • the positioning cycle of the positioning means and the computing cycle of the satellite position computing means may be synchronized with integral multiples of the computing cycles of the ADR computing means and the PSR computing means.
  • the previous cycle and the current cycle of the ADR computing means and those of the PSR computing means are synchronized with the previous cycle and the current cycle of the positioning means and those of the satellite position computing means.
  • the determination by the PSR error determination means is typically made in an cycle synchronized with the computing cycle of the PSR computing means.
  • the PSR error determination means may make a determination in the computing cycle of the PSR computing means that is synchronized with the positioning cycle of the positioning means and the computing means of the satellite positioning means.
  • the PSR error determination means does not have to make a determination per positioning cycle of the positioning means and per computing cycle of the satellite position computing means, but may make a determination once per a certain plurality of cycles or at random cycles.
  • the positioning means determines the position of the moving body in the current cycle based on the estimated pseudorange that is computed by the PSR estimating means instead of the pseudorange that is computed by the PSR computing means in the current cycle when either one of the following conditions is met: the PSR error determination means determines that the error in the pseudorange that is computed by the PSR computing means in the current cycle exceeds the given allowable range, and a given time period has not been elapsed since a satellite related to the pseudorange is captured.
  • the positioning means may determine the position of the moving body in the current cycle based on the estimated pseudorange that is computed by the PSR estimating means instead of the pseudorange that is computed by the PSR computing means in the current cycle if the PSR error determination means determines that the error in the pseudorange that is computed by the PSR computing means in the current cycle exceeds the given allowable range, and the given time period has not been elapsed since the satellite related to the pseudorange is captured.
  • the determination of whether or not the satellite is newly captured may be made based on a captured time period that corresponds with a time period required for filtering process of the pseudorange and that starts from a cycle in which the satellite is captured.
  • the filtering process may be carrier smoothing using a Hatch filter or a Kalman filter.
  • the positioning means may execute positioning by an inertial navigation method with use of information from an INS sensor when it is impossible to execute positioning by a satellite navigation method based on a reception result of the satellite wave.
  • the positioning result of the moving body in the previous cycle that is produced in the positioning means and used in the previous value PSR estimating means may include a positioning result derived by the inertial navigation method.
  • the positioning means may execute positioning when the number of satellites for which either the pseudorange or the estimated pseudorange is computed is equal to or greater than three. [0013] In the moving body positioning device according to the first aspect, the positioning means may execute positioning by the satellite navigation method when the number of satellites for which the estimated pseudorange is computed is equal to or greater than four, and when the number of satellites for which the pseudorange is computed is equal to or greater than two.
  • the PSR error determination means may compare a difference ⁇ PSR between pseudoranges that are computed by the PSR computing means in the previous and current cycles with a difference ⁇ ADR between ADRs that are computed by the ADR computing means in the previous and current cycles, with respect to the same satellite, and may determine whether or not the error in the pseudorange that is computed by the PSR computing means exceeds the given allowable range.
  • the PSR error determination means may determine that the error in the pseudorange that is computed by the PSR computing means exceeds the given allowable range when an absolute value
  • the positioning means may determine the position of the moving body in the current cycle based on the pseudorange that is computed by the PSR computing means in the current cycle when the PSR error determination means determines that the error in the pseudorange that is computed by the PSR computing means in the current cycle does not exceed the given allowable range.
  • the previous value PSR estimating means may compute the estimated previous value by adding the magnitude of the difference vector to an estimated value of a clock error that is included in the pseudorange.
  • the estimated value of the clock error may be derived by calculating back from the positioning result produced in the positioning means.
  • the PSR estimating means may compute the estimated pseudorange in the first cycle of the two or more cycles by adding the estimated previous value to the difference between ADRs that are computed by the ADR computing means in the previous and current cycles, and from the second cycle onward by adding the estimated pseudorange that is computed in the previous cycle to the difference between ADRs that are computed by the ADR computing means in the previous and current cycles.
  • a moving body positioning method through which a moving body receives a radio wave from a satellite to determine the position of the moving body includes: computing a pseudorange between the satellite and the moving body per given cycle based on an observed phase of a pseudo random noise code in a satellite wave; computing an accumulated Doppler range per given cycle based on an observed Doppler frequency of the satellite wave; determining the position of the moving body per given cycle based on the computed pseudorange; obtaining information representing a satellite position to compute the satellite position per given cycle; computing an estimated previous value as an estimated value of the pseudorange in a previous cycle based on a magnitude of a difference vector between a positioning result of the moving body in the previous cycle and a computed result of the satellite position in the previous cycle; computing an estimated pseudorange as an estimated value of the pseudorange in a current cycle by adding the estimated previous value to a difference between the accumulated
  • Doppler ranges computed in the previous and current cycles determining whether an error in the computed pseudorange exceeds a given allowable range; and determining the position of the moving body in the current cycle based on the estimated pseudorange, which is computed in the current cycle, instead of the pseudorange that is computed in the current cycle when it is determined that the error in the pseudorange that is computed hi the current cycle exceeds the given allowable range.
  • a moving body positioning device with which highly accurate positioning can be achieved even when an error in a computed pseudorange is large and a moving body positioning method can be provided.
  • FIG 1 is a system configuration diagram showing a general configuration of a GPS to which a moving body positioning device according to a first embodiment of the present invention is applied;
  • FIG.2 is a block diagram showing an example of main components of a GPS receiver according to the first embodiment of the present invention;
  • FIG 3 is a block diagram showing an example of main components of a DLL of the GPS receiver according to the first embodiment of the present invention
  • FIG 4 is a flow chart showing the flow of main processing executed by the GPS receiver according to the first embodiment of the present invention.
  • FIG 5 is a graph showing time sequences of PSR, EPSR, and ADR after capture of a GPS satellite according to the first embodiment of the present invention
  • FIG 6 is a block diagram showing an example of main components of a GPS receiver according to a second embodiment of the present invention
  • FIG 7 is a flow chart showing the flow of main processing executed by the GPS receiver according to the second embodiment of the present invention.
  • FIG 1 is a system configuration diagram showing a general configuration of a Global Positioning System (GPS) to which a moving body positioning device according to the present invention is applied.
  • GPS Global Positioning System
  • the GPS is constituted of GPS satellites 10 orbiting the Earth and a vehicle 90 located and traveling on the Earth.
  • the vehicle 90 is merely an example of a moving body, and the moving body can also be any of a motorcycle, train, ship, aircraft, foiklift, robot, information terminal such as a cellular phone that moves together with a user, and the like.
  • the GPS satellite 10 continuously broadcasts a navigation message (satellite signal) to the Earth.
  • the navigation message includes the satellite orbital information of the corresponding GPS satellite 10 (an ephemeris and an almanac), a correction value of a clock, and an ionospheric correction factor.
  • the navigation message is diffused by a C/A-code and continuously broadcasted to the Earth on an Ll carrier (frequency: 1575.42 MHz).
  • the Ll carrier is a synthetic wave of a sine wave modulated by the C/A-code and a cosine wave modulated by a precision code (P-code), and is orthogonally modulated.
  • Both the C/A-code and the P-code are a pseudo random noise code, a repeated sequence with a random set of -Is and Is.
  • the twenty four GPS satellites 10 orbit the Earth at an altitude of about 20,000 km, and each four of the GPS satellites 10 are evenly arranged in one of six Earth orbital planes that are each inclined 55 degrees to the other. Therefore, as long as the sky is clear, at least five GPS satellites 10 can be constantly observed from anywhere 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 showing an example of main components of the GPS receiver 20 according to the first embodiment of the present invention.
  • FIG 3 is a block diagram showing an example of main components of a DLL 203 of the GPS receiver 20 according to the first embodiment of the present invention.
  • the processing of the signal from the GPS satellite 10 j is substantially the same as the processing of a signal from another GPS satellite 10.
  • the processing of a satellite signal, which is described later, is performed in parallel (simultaneously) with the processing of signals from all the observable GPS satellites.
  • the GPS receiver 20 includes a high-frequency circuit 201, an analog-to-digital (AfO) converter circuit 202, a Delay-Locked Loop (DLL) 203, a Phase-Locked Loop (PLL) 204, a filter 205, a PSR e ⁇ or determination section 206, an ADR computing section 208, a satellite position computing section 209, a PSR estimating section 212, a position computing section 214, a computed value storing section 216, and a PSR previous value estimating section 218.
  • AfO analog-to-digital
  • DLL Delay-Locked Loop
  • PLL Phase-Locked Loop
  • the A/D converter circuit 202 converts an EF signal (analog signal) supplied from the high-frequency circuit 201 to a digital IF signal for digital signal processing.
  • the DLL 203 is configured to synchronize a phase of the C/A-code on the Ll carrier with a phase of an internally generated replica C/A-code and to compute a pseudorange (PSR) (hereinafter referred to as "PSR'j")-
  • PSR pseudorange
  • the apostrophe added to PSR j indicates that filtering process, which is described later, has not been performed, and a symbol with the subscript "j" indicates that it is a value related to the GPS satellite 1O j (the same rule applies to values other than PSR'j).
  • the digital IF signal is multiplied by a replica carrier, which is supplied from the PLL 204, by a mixer (not shown), and then input to the DLL 203 in practice.
  • the DLL 203 includes cross-correlation computing sections 111 and 112, a phase leading section 113, a phase lagging section 114, a phase shift computing section 115, a phase correction amount computing section 116, a replica C/A-code generating section 117, and a PSR computing section 118.
  • a replica C/A-code is generated in the replica C/A-code generating section 117.
  • the replica C/A-code has the same sequence of +ls and -Is as the C/A-code on the signal from the GPS satellite 10j.
  • the replica C/A-code generated in the replica C/A-code generating section 117 is input to the cross-correlation computing section 111 via the phase leading section 113.
  • an early replica code is input to the cross-correlation computing section 111.
  • the replica C/A-code is led for given phases.
  • An amount of the phases by which the replica C/A-code is led in the phase leading section 113 is set as ⁇ j.
  • the digital IF signal is also input to the cross-correlation computing section 111 after being multiplied by the replica carrier, which is generated in the PLL 204, by the mixer (not shown).
  • the input digital IF signal and the early replica code with the phase leading amount of ⁇ j are used to compute a correlation value (early correlation value ECA)-
  • the early correlation value ECA ⁇ S computed by the following equation, for example:
  • Early correlation value ECA ⁇ (digital IF) x (Early replica code) ⁇ .
  • the replica C/A-code generated in the replica C/A-code generating section 117 is input to the cross-correlation computing section 112 via the phase lagging section 114.
  • a late replica code is input to the cross-correlation computing section 112.
  • the replica C/A-code is lagged for given phases.
  • the amount of phases by which the replica G/A-code is lagged in the phase lagging section 114 is equal to the phase leading amount ⁇ j but is denoted by an opposite sign.
  • the digital EP signal is also input to the cross-correlation computing section 112 after being multiplied by the replica carrier, which is generated in the PLL 204, by the mixer (not shown).
  • IQ the cross-correlation computing section 112 the input digital IF signal and the late replica code with the phase lagging amount of - ⁇ j are used to compute a correlation value (late correlation value LCA).
  • the correlation values with a correlation interval L are computed in the cross-correlation computing sections 111, 112.
  • the early correlation value ECA and the late correlation value LCA that are respectively computed in the cross-correlation computing sections 111, 112 arc input to the phase shift computing section 115.
  • phase shift computing section 115 a phase shift amount is computed between the digital IF signal and the replica C/A-code generated in the replica C/A-code generating section 117.
  • a phase shift amount ⁇ of the replica C/A-code with respect to the received C/A-code is computed (estimated) in the phase shift computing section 115.
  • phase shift amount ⁇ computed as above is input to the phase correction amount computing section 116.
  • phase correction amount computing section 116 a proper phase correction amount is computed to offset the phase shift amount ⁇ .
  • the above equation represents feedback control using PI control, and P-gain and I-gain are experimentally determined in consideration with a balance between variation and responsiveness.
  • the phase correction amount computed as above is input to the replica C/A-code generating section 117. [0042] In the replica C/A-code generating section 117, the phase of the replica
  • the C/A-code to be generated is corrected for the phase correction amount that is computed in the phase correction amount computing section 116. In other words, a tracking point of the replica C/A-code is corrected.
  • the replica C/A-code generated as above is input to the cross-correlation computing sections 111, 112 via the phase leading section 113 and the phase lagging section 114 as described above, and is also input to the PSR computing section 118. Li the cross-correlation computing sections 111, 112, the replica C/A-code generated as above is used to compute the correlation value with respect to the IF digital signal that will be input in the next observation cycle.
  • PSR' j is computed by the following equation, for example:
  • NCA denotes the number of bits in the C/A-code from the GPS satellite 1O j to the vehicle 90, and is computed based on the phase of the replica C/A-code generated in the replica C/A-code generating section 117 and a receiver clock in the GPS receiver 20.
  • the numerical value 300 is derived from a fact that a bit length of the C/A-code is 1 ⁇ s, which is equivalent to about 300 m (1 ⁇ s x the speed of light).
  • a signal representing PSR J j which is computed as above, is input from the DLL 203 to the filter 205.
  • the PLL 204 computes a correlation value relative to a received carrier wave (received carrier) by using a replica carrier signal generated therein, and then measures a Doppler frequency (Doppler shifted frequency) ⁇ f j of the Doppler-shifted received carrier.
  • the digital IF signal is multiplied by the replica C/A-code, which is supplied from the DLL 203, by the mixer (not shown) and then input to the PLL 204 in practice.
  • a signal that represents the Doppler frequency ⁇ f j . which is computed in the PLL 204, is input to the filter 205 and the ADR computing section 208.
  • (i) denotes a current value
  • (i-1) denotes a previous value (the same rale applies when (i) or (i-1) is added to other symbols).
  • M is a weighting factor. The value M is properly determined in consideration of precision and responsiveness.
  • the above filtering process in the filter 205 is so-called carrier smoothing known in the art, and can also be executed with a Kalman filter, for example, instead of the above-mentioned filtering process with a Hatch filter.
  • a signal that represents PSRj after the filtering process, which is computed as described above, is input to the PSR error determination section 206 and the position computing section 214.
  • the PSR error determination section 206 evaluates an error in PSR j after the filtering process, and then determines whether or not the error exceeds a given allowable range. Of all the various determination methods, one method will be described later. A determination result produced in the PSR error determination section 206 is input to the position computing section 214.
  • an accumulated Doppler range, ADR j is computed by using the Doppler frequency ⁇ fj obtained in the PLL 204.
  • ADR j is an integrated value of a Doppler range dp j that is computed from the Doppler frequency ⁇ f j , and an initial value of ADR j can be any value.
  • ADR j may be computed by the following equation: [Equation 2]
  • ADRo denotes any initial value
  • a Doppler range dp j (k) denotes the Doppler range dp j obtained in a cycle k.
  • a signal that represents ADRj, which is computed as described above, is input to the PSR error determination section 206 and the PSR estimating section 212.
  • IGS International GNSS Service
  • the position S j of the GPS satellite 1Oj can be derived immediately after the GPS satellite 1O j is captured.
  • the satellite position S j derived in the satellite position computing section 209 as described above is input to the position, computing section 214.
  • the PSR estimating section 212 computes an estimated value (i) with respect to a current value PSR'j(i) of the pseudorange that is computed in the PSR computing section 118 as described above. From now, the estimated value (i) is referred to as "EPSR j (i)" (EPSR: estimated pseudorange) for distinction.
  • EPSR j (i-l) of the previous value
  • the estimated value PSRJO of the PSR previous value obtained in the PSR previous value estimating section 218, which will be described later, is used.
  • EPSR j is computed by adding a difference between the current value ADRj(I) and the previous value ADR j (M) to the estimated value PSRJO of the PSR previous value.
  • a signal that represents EPSRj, which is derived in the PSR estimating section 212 as described above, is input to the position computing section 214.
  • the position of the vehicle 90 may be computed by the following equation using a least square method or the like, for example: [Equation 3]
  • c • ⁇ T denotes a clock error in the GPS receiver 20. If the number of GPS satellites 10 available for positioning is four, the equation 3 is computed for four coordinates, thereby allowing positioning without the clock error c • ⁇ T. In this case, an error included in the observed range of each GPS satellite 10 may be estimated, and an index value that represents the error level (a variance) may be used as a diagonal element of a weighting matrix to compute a weighted position.
  • a decision on whether to use PSR,(i) or EPSR,(i) depends on the determination result produced in the PSR error determination section 206 in the current cycle (i), that is, an error in PSR j (i).
  • PSRj is used if it is determined that the error in PSR j (Q in the current cycle (i) is within the given allowable range
  • EPSRj(i) is used if it is determined that the error in PSR j (i) in the current cycle (i) exceeds the given allowable range.
  • PSR j is used as the measured range for the positioning in cycles (i) in which the error in PSRj(i) is in the given allowable range. Meanwhile, in the other cycles (i) in which the error in PSRj(i) exceeds the given allowable range, EPSR j (i) is used as the measured range for the positioning.
  • the positioning result produced in the position computing section 214 as described above may be supplied to a navigation system (not shown) for display of a vehicle location on a map, for example. It should be noted that the position computing section 214 may compute a speed of the vehicle 90 by using the Doppler range dp j in addition to the position of the vehicle 90.
  • the clock error c • ⁇ T (see the equation 3) in the GPS receiver 20 that is derived by calculating back from the positioning result in the position computing section 214 is also stored in the computed value storing section 216.
  • the clock error c • ⁇ T may be computed in the position computing section 214 for each cycle (i); however, it may be computed only once when code tracking is completed.
  • the PSR previous value estimating section 218 computes an estimated value PSRjo (hereinafter referred to as an "estimated previous value PSRJO") with respect to the previous value PSR' j (i-l) of the pseudorange that is computed in the PSR computing section 118 as described above .
  • the estimated previous value PSRjo is computed by the following equation, for example, by using the previous value of the position of the vehicle 90, ((X 11 (H), Y u (i-1), Zu(H)), the previous value of the satellite position, (X j (i-l), Yj(i-l), Zj(I-I)), and the clock error c • ⁇ T in the GPS receiver 20, which are all stored in the computed value storing section 216: [Equation 4]
  • FIG 4 is a flow chart showing the flow of main processing executed by the GPS receiver 20 according to the first embodiment of the present invention.
  • a loop 1 is performed per given cycle (positioning cycle of the position computing section 214), and a current cycle is set here as a cycle (i) for description.
  • the positioning cycle of the position computing section 214 may be synchronized with a PPS signal and 1 second, for example.
  • the computing cycles of PSR and ADR may be synchronized with the positioning cycle, or may be fractional multiples of the positioning cycle (for example, 10 ms).
  • a loop 2 is set within the loop 1 and is executed for each of the observable GPS satellites 10 in one cycle. A description below is mainly made on the processing in the loop 2 in regard to the GPS satellite 1Oj.
  • step 400 PSR j (i) of the current cycle is derived in the DLL 203 and the filter 205, and ADRj(i) of the current cycle is computed in the ADR computing section 208.
  • step 404 it is determined in the PSR error determination section 206 whether or not the GPS satellite 1O j is newly captured and whether or not the error in PSR(i) in the current cycle exceeds the allowable range.
  • the determination of whether or not the GPS satellite 10 j is newly captured may be made based on the number of elapsed cycles (a captured time period) from a cycle in which the GPS satellite 10 j is captured initially, or based on whether or not the captured time period is shorter than a given time period, for example.
  • the given time period may correspond with time ⁇ Tl required for the filter 205 to complete the processing (see FIG 5), for example, and is adjusted in accordance with test results, etc.
  • the given threshold value is a compatible value, and, for example, it may be set as a value slightly larger than the maximum absolute value j ⁇ PSR - ⁇ ADR
  • Another method may be used to determine whether or not the error in PSR(i) in the current cycle exceeds the given allowable range. For example, it may be determined that the error in PSR(i) in the current cycle exceeds the given allowable range when reception sensitivity of radio waves from the GPS satellite 1O j is lower than a given reference value, when a peak correlation value that is computed at the time of code tracking is lower than a given reference value, or when multipath of the radio waves from the GPS satellite 10 j is detected. [0063] In step 404, if it is determined that the GPS satellite 10j is newly captured and that the error in PSR(i) in the current cycle exceeds the given allowable range, the process proceeds to step 406.
  • the process proceeds to step 410.
  • the process may proceed to step 406 if it is determined that the GPS satellite 10 j is newly captured or that the error in PSR(i) in the current cycle exceeds the given allowable range.
  • the process proceeds to step 410 if it is determined that the GPS satellite 10 j is not newly captured and that the error in PSR(i) in the current cycle does not exceed the given allowable range.
  • the process may proceed to step 406 if it is determined that the error in PSR(i) in the current cycle exceeds the given allowable range, and the process may proceed to step 410 if it is determined that the error in PSR(i) hi the current cycle does not exceed the given allowable range.
  • an estimated value of the previous value PSR j (M) of PSR j is computed in the PSR previous value estimating section 218.
  • the computing method of the estimated previous value PSRJO is as described above.
  • the estimated previous value PSRJO can be computed by substituting the previous value of the positioning result of the vehicle 90 ((X 11 (M), Y n (H), Zu(i-1)), the previous value of the satellite position (X j (M), Y j (M) 9 Zj(M)), and the clock error c « ⁇ T in the GPS receiver 20, which are all stored in the computed value storing section 216, into the above equation 4.
  • step 406 is executed only when the condition in step 404 is true. Alternatively, when the conditions in above step 404 are true for consecutive cycles, the processing in step 406 may only be executed for the first cycle.
  • step 408 the estimated value of the current value PSR j (Q of PSR j , that is, EPSR j (i) is computed in the PSR estimating section 212.
  • the computing method of EPSR j (i) is as described above.
  • EPSRj(i) is computed by the following equation, for example, by using the current value ADRj(i) obtained from the ADR computing section 208 and the previous value ADR j (M) obtained from the computed value storing section 216:
  • EPSRj(i) EPSRj(M) + ADRj(i) -ADRj(M).
  • EPSR j (M) is a previous value, and in an cycle in which step 406 is executed, the estimated previous value PSRjo obtained in step 406 is used.
  • EPSRj(i) is computed in step 408, PSR(i) obtained in step 400 will be replaced with EPSR j (i).
  • PSR(i) obtained in step 400 is discarded when the condition in step 404 is true, and EPSRj(i) is adapted instead.
  • PSR(i) is adopted.
  • step 410 it is determined whether or not PSR(i) or EPSR(i) is computed for all the observable GPS satellites 10. If the condition is true, the process leaves the loop 2 and proceeds to step 412. Meanwhile, if PSR(i) or EPSR(i) has not been computed for one or more of the GPS satellites 10, the processing in the loop 2 (the processing from step 400) is executed for the appropriate GPS satellites 10.
  • step 412 the position of the vehicle 90 in the current cycle (i), (X u (i), Y u (i), Z tt (i)), is computed in the position computing section 214 by using PSR(i) or EPSR(i) obtained for each of the GPS satellites 10 in the loop 2 in the current cycle (i).
  • the computing method of the position of the vehicle 90 is as described above. However, if the number of observed GPS satellites 10 is greater than that required for positioning, PSR(i) may be used preferentially to EPSR(i). In other words, only when the number of GPS satellites 10 for which PSR(i) is computed is insufficient, the GPS satellites 10 for which EPSR(i) is computed may be supplementary used to compute the position of the vehicle 90.
  • step 414 the positioning result that is obtained in step 412, ADR, and the current values of the satellite positions are stored in the computed value storing section 216. These computed values are used as "previous values" in the next cycle.
  • step 416 positioning in the current cycle is terminated, and the process from the loop 1 is repeated in the next cycle.
  • FIG 5 shows time sequences of PSR j , EPSR j , and ADR j that are computed as above.
  • FIG 5 shows the time sequences of PSR j , EPSR j , and ADR j according to the GPS satellite 1Oj.
  • FIG 5 schematically shows the time sequence of a true value of PSRj.
  • a graph starts at time t0 when the GPS satellite 1O j is captured.
  • the error in PSRj (an error relative to the true value) is large because the processing in the filter 205 is not completed.
  • ADRj is a relative value, it retains relatively high accuracy even in the time period ⁇ T1 in a short time since the capture of the GPS satellite 1Oj. Therefore, it can be understood that EPSRj computed from the satellite position, the previous value of the positioning result, and ADRj has a smaller error than PSRj even in the time period ⁇ T1 in a short time since the capture of the GPS satellite 1O j . Consequently, EPSR j can be used for positioning. In other words, by using EPSRJ instead of PSR j , the positioning can be executed with high accuracy from the time period ⁇ T1 in a short time since the capture of the GPS satellite 1O j . In an example shown in FIG 5, PSRj is used for positioning from time tl onward because the error in PSRj becomes smaller at time tl, for example.
  • the highly accurate positioning can be started and maintained by using EPSRj, which is appropriately estimated, instead of PSR j even in a time period in a short time since the capture of the satellite 1Oj or a time period in which the accuracy of PSR j according to the GPS satellite 10 j is low. Accordingly, the positioning with high accuracy can be started from the time immediately after the GPS satellite 1O j is newly captured, for example, and can be maintained even when the accuracy of PSR j according to the GPS satellite 1O j is temporarily degraded under the influence of the multipath, etc.
  • the second embodiment of the present invention mainly differs from the first embodiment in which the positioning computation is executed by the satellite navigation method in a point that the position is computed by selectively using an inertial navigation method with an INS sensor. Description will hereinafter be made by focusing on the unique features of the second embodiment, and the other features of the second embodiment may be the same as the features of the first embodiment
  • FIG 6 is a block diagram showing an example of main components of a GPS receiver 20' according to the second embodiment of the present invention.
  • the GPS receiver 20' includes an INS sensor data obtaining section 220 that obtains INS sensor data from the INS sensor (not shown) installed in the vehicle 90.
  • the INS sensor may be constituted of a tii-axial acceleration sensor and a tri-axial angular velocity sensor.
  • Aposition computing section 214' computes the position of the vehicle 90,
  • the vehicle position and vehicle speed (INS positioning results) computed by the inertial navigation method in the position computing section 214' may be respectively compared with the vehicle position and vehicle speed (GPS positioning results) computed by the above satellite navigation method to obtain difference values therebetween. Then, the difference values may be input to the Kalma ⁇ filter to determine various correction amounts.
  • FIG 7 is a flow chart showing the flow of the main processing executed by the GPS receiver 20' according to the second embodiment of the present invention.
  • INS sensor data is obtained in the INS sensor data obtaining section 220.
  • step 702 PSR j (i) in the current cycle is derived in the DLL 203 and the filter 205, and ADR j (i) in the current cycle is computed in the ADR computing section 208.
  • step 706 it is determined in the PSR error determination section 206 whether or not the GPS satellite 10 j is newly captured and whether or not the error in PSR(i) in the current cycle exceeds the given allowable range.
  • the determination method can be the same as that in step 404 of FIG 4 in the first embodiment.
  • step 706 if it is dete ⁇ nined that the GPS satellite 10 j is newly captured and that the error in PSR(i) exceeds the given allowable range, the process proceeds to step 708. Unless one of the above condition is satisfied, the process proceeds to step 712.
  • the process may proceed to step 708 if it is dete ⁇ nined that the GPS satellite 1O j is newly captured or that the error in PSR(i) in the current cycle exceeds the given allowable range.
  • the process proceeds to step 712 if it is determined that the GPS satellite 1Oj is not newly captured and that the error in PSR(i) in the current cycle does not exceed the given allowable range.
  • the process may proceed to step 708 if it is dete ⁇ nined that the error in PSR(i) in the current cycle exceeds the given allowable range, and the process may proceed to step 712 if it is dete ⁇ nined that the error in PSR(i) in the current cycle does not exceed the given allowable range.
  • step 708 the estimated value of the previous value PSR j (M) of PSR j , that is, the estimated previous value PSRJO is computed in the PSR previous value estimating section 218.
  • the computing method of the estimated previous value PSRJO is as described above.
  • the processing in step 708 is executed only in a first cycle in which the condition in step 706 is true. Alternatively, when the conditions in above step 706 are true for consecutive cycles, the processing in step 708 may only be executed for the first cycle.
  • step 710 the estimated value of the current value PSR j (i) of PSRj, that is, EPSRj(i) is computed in the PSR estimating section 212.
  • the computing method of EPSRj(i) is as described above.
  • EPSR j (i) is computed by the following equation, for example, by using the current value ADR j (i) that is obtained from the ADR computing section 208 and the previous value ADR j (i-l) that is obtained from the computed value storing section 216:
  • EPSRj(i) EPSRj(i-l) + ADRj(i) -ADR j (I-I).
  • EPSRj(i-l) is a previous value
  • the estimated previous value PSRjo obtained in step 708 is used.
  • EPSRj(I) is computed in step 710
  • PSR(i) obtained in step 702 will be replaced with EPSR,(i).
  • PSR(i) obtained in step 702 is discarded when the condition in step 706 is true, and EPSRj(i) is computed instead.
  • step 712 it is determined whether or not PSR(i) or EPSR(i) is computed for all the observable GPS satellites 10. If the condition is true, the process leaves the loop 2 and proceeds to step 714. Meanwhile, if PSR(i) or EPSR(i) has not been computed for one or more of the GPS satellites 10, the processing in the loop 2 (the processing from step 702) is executed for the appropriate GPS satellites 10.
  • step 714 it is determined whether or not GPS positioning computation is possible in the position computing section 214'.
  • the positioning by the satellite navigation method positioning by the equation 3 that is described in the first embodiment is possible.
  • the GPS positioning computation is possible when the number of the GPS satellites 10 for which PSR(i) or EPSR(i) is computed is equal to or larger than a given number.
  • the given number may be 3, but preferably be equal to or larger than 4 to eliminate the clock error.
  • the GPS positioning computation is possible when the number of the GPS satellites 10 for which PSR(i) or EPSR(i) is computed is equal to or larger than a given number ThI, and when the number of the GPS satellites 10 for which PSR(i) is computed is equal to or larger than a given number Th2.
  • the given number ThI may be an appropriate number equal to or larger than 4, and the given number Th2 may be set smaller than the given number ThI (for example, 2). If it is determined in step 714 that the GPS positioning computation is possible, the process proceeds to step 716, If it is determined in step 714 that the GPS positioning computation is impossible, the process proceeds to step 718.
  • step 716 the position of the vehicle 90, (X u (i), Y u (i), Z n (J)), in the current cycle (i) is computed in the position computing section 214' by using PSR(i) or EPSR(i) obtained for each of the GPS satellites 10 in the loop 2 in the current cycle (i).
  • the computing method of the position of the vehicle 90 is as described above. However, if the number of the observed GPS satellites 10 is larger than that required for positioning, PSR(i) may be used preferentially to EPSR(i).
  • step 718 the position of the vehicle 90, (X 0 (J), Y u (i), Zu(i)), is computed by the i ⁇ ertial navigation method in the position computing section 214' .
  • the computing method of the position of the vehicle 90 by the inertial navigation method is as described above.
  • step 720 the positioning result obtained in step 716 or 718, ADR, and the current values of the satellite positions are stored in the computed value storing section 216. These computed values are used as "previous values" in the next cycle.
  • step 722 positioning in the current interval is terminated, and the process from the loop 1 is repeated in the next cycle.
  • the highly accurate positioning can be started and maintained by using EPSR j , which is appropriately estimated, instead of PSR j even in a time period in a short time since the capture of the satellite 10; or a time period in which the accuracy of PSR j according to the GPS satellite 1O j is low. Accordingly, the positioning with high accuracy can be started from the time immediately after the GPS satellite 10j is newly captured, for example, and can be maintained even when the accuracy of PSR,- according to the GPS satellite 1Oj is temporarily degraded under the influence of the multipath, etc.
  • the estimated previous value PSR j o can be computed in any cycle because the positioning result can be output either by the satellite navigation method or by the inertial navigation method.
  • the PSR estimating section 212 and the PSR previous value estimating section 218 may be operated only when the determination result in the above PSR error determination section 206 is negative, that is, only in a cycle in which the error in PSRj afteT the filtering process exceeds the given allowable range.
  • part of various functions performed by the GPS receiver 20 may be performed by an external computer that is connected to the GPS receiver 20, or may be performed in cooperation with an external computer that is connected to the GPS receiver 20.
  • the filter 205 is used; however, the filter 205 may be omitted.
  • the determination processing is executed every positioning cycle in the PSR error determination section 206; however, the determination processing may be executed once per a plurality of positioning cycles or at random cycles (any cycle that is synchronized with the positioning cycle).
  • the determination processing in the PSR error determination section 206 may only be executed for a given time period after the new GPS satellite 10 is captured. From the similar perspective, processing shown in FIG. 4 and FIG. 7 may only be executed for a given time period after the new GPS satellite 10 is captured.
  • PSR is derived by using the C/A-code; however, PSR can be computed based on another pseudo random noise code such as a P-code on an L2 carrier.
  • the P-code may be decoded by the DLL that uses a cross-correlation method upon synchronization of the P-code.
  • GNSS Global Navigation Satellite System

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Navigation (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Traffic Control Systems (AREA)

Abstract

Un dispositif de positionnement d'un corps en déplacement selon la présente invention comprend : des moyens d'estimation d'une valeur de PSR précédente destinés à calculer une valeur précédente estimée dans un cycle précédent sur la base d'une grandeur d'un vecteur de différence entre un résultat de positionnement du corps en déplacement dans le cycle précédent, et un résultat calculé de la position d'un satellite dans le cycle précédent; des moyens d'estimation de PSR destinés à calculer une pseudo-plage estimée dans le cycle actuel en ajoutant la valeur précédente estimée à une différence entre les ADR qui sont calculés dans les cycles précédent et actuel; et des moyens de détermination d'erreur de PSR destinés à déterminer si une erreur dans la pseudo-plage dépasse une plage permise donnée, les moyens de positionnement déterminant la position du corps en déplacement dans le cycle actuel sur la base de la pseudo-plage estimée quand on détermine que l'erreur dans la pseudo-plage dans le cycle actuel dépasse la plage permise donnée.
PCT/IB2009/000548 2008-03-19 2009-03-19 Dispositif de positionnement d'un corps en déplacement et procédé de positionnement d'un corps en déplacement WO2009115899A2 (fr)

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