JP2007271500A - Position/attitude estimation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance attitude estimation precision and position estimation precision, by reducing a multipath error without complicating a device, in a GNSS (Global Navigation Satellite System) position/attitude estimation device using a plurality of antennas. <P>SOLUTION: This attitude estimation device of the present invention includes a function for assigning a carrier wave phase difference calculated by a following expression using attitude angle information, as a restriction condition, in a correlation device mounted with plurality of antennas on a moving body, and for correlating a GNSS satellite signal acquired in the each antenna with a replica signal generated in an inside of the device, and further includes a means for reducing the multipath error of a carrier wave phase by using the correlation device having the restriction condition, using the attitude angle obtained by a function of a conventional GNSS attitude estimation device as an initial value, and for estimating the carrier wave phase in the each antenna to recalculate the attitude angle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a GNSS navigation positioning technique, and more particularly to an apparatus for improving posture estimation accuracy and position estimation accuracy. This GNSS is an abbreviation for Global Navigation Satellite System. It is a global navigation positioning system using satellites represented by GPS, GLONASS operated in Russia, GALILEO being developed in Europe, and Japan being developed. Includes quasi-zenith satellite system.

GNSS is widely used for navigation positioning of aircraft, ships, and automobiles, but it can also be used for attitude determination by using the phase difference of GPS observation data (carrier phase) for multiple antennas, and practically used as a GPS compass for ships Has been. In order to improve the position / posture estimation accuracy, it is necessary to reduce the multipath error (multiple propagation error) included in the GNSS signal.
It is known that this multipath error can be reduced by using a special antenna (choke ring, antenna, etc.) and using an advanced correlator (narrow correlator, strobe correlator) inside the receiver. It is also possible to reduce the noise by receiving these antennas and comprehensively processing these received signals.

  As what is received by a plurality of antennas, Patent Document 1 discloses a positioning device for obtaining a positioning device capable of realizing high positioning accuracy even when there is temporary shielding or fading of radio waves. A device is presented. This positioning device has a function to receive radio waves from a transmitter with multiple receivers, position the transmitter at regular intervals based on the received signals, and estimate the next periodic positioning prediction value. A positioning processing unit that calculates a positioning prediction error based on a comparison between an observed value based on received signals of a plurality of receivers and a predicted value based on an estimated next periodic positioning prediction value; and a transmitter based on the positioning prediction error Filter means for estimating the state of the positioning value and the next periodic positioning prediction value. In conventional positioning devices, if positioning is temporarily interrupted due to temporary shielding of radio waves or fading that occurs in the indoor environment, the integer bias will be lost, making it impossible to continue positioning. . Alternatively, since positioning must be performed using an erroneous integer value bias, there is a problem that errors in subsequent positioning increase. In addition, since positioning is performed based on the phase difference between the receivers, if the receiver used as a phase reference is shielded or the reception state is deteriorated due to fading or the like, the accuracy of measurement of the phase difference in all equations is deteriorated. There is a problem that positioning accuracy deteriorates. However, the present invention makes it possible to perform positioning based on the received signal of each receiver without using a specific receiver as a reference by utilizing the predicted positioning value estimated by the filter means. A positioning device capable of realizing high positioning accuracy can be obtained even when there is temporary shielding or fading of radio waves at a certain receiver.

  Further, Patent Document 2 aims to improve the detection accuracy of positioning and improve the reliability by removing the influence of multipath in a positioning device that performs positioning of a mobile object using a GPS satellite. A “positioning device” is disclosed. This positioning device was obtained by dividing n antennas (n is an integer of 1 or more) for receiving signals from GPS satellites and m baseband signals into m pieces in the time axis direction (m × n). (M × n) channel position information is calculated from the baseband signals of (m × n), and (m × n) baseband signal processing units are provided to demodulate the received signal from each of the n antennas to generate n baseband signals. For each n baseband signals and distributed to m data at different times to obtain (m × n) baseband signals, and the spatial diversity and temporal diversity By configuring so as to calculate the position, the reliability is improved and the position detection accuracy is improved.

Incidentally, Patent Document 1, Patent Document 2, and Non-Patent Document 1 described above are also intended to provide a highly accurate positioning device, and do not assume that an accurate posture device is provided. Further, Patent Document 1 is a technique for removing the influence of temporary shielding or fading of radio waves, and is not a technique for reducing or removing multipath errors. Although Patent Document 2 mentions multipath, this apparatus uses a reception state detection unit from (m × n) channel position information calculated by (m × n) baseband signal processing units. The position of the (m × n) channel calculated by the screening unit that screens the position information of the bad reception state according to the detected reception state information and (m × n) baseband signal processing units. After the screened information is removed from the information, a technique is employed in which diversity processing is performed in the calculation unit to detect and calculate the position information of the moving body, which makes the processing method cumbersome and complicates the apparatus.
The US patent of Patent Document 3 uses a correlator that arranges a plurality of antennas and correlates a signal acquired by each antenna and a signal generated inside the receiver, but uses external information for the attitude angle. It is.
JP 2005-326184 A “Positioning device” published on November 24, 2005 Japanese Patent Laid-Open No. 2005-69743 “Positioning Device” published on March 17, 2005 US Pat. No. 6,883,212 MY Vorobiev et al., “Method and Apparatus for Multipath Mitigation Using Antenna Array” Apr. 19, 2005. Ray, JK, ME Cannon and P. Fenton, Mitigation of Static Carrier Phase Multipath Effects Using Multiple C1osely-Spaced Antennas, NAVIGATION, J. of the Institute of Navigation, 46, No.3, 1999, pp193-202.

  An object of the present invention is to improve posture estimation accuracy and position estimation accuracy by reducing a multipath error in a GNSS position / posture estimation device using a plurality of antennas without complicating the device.

また、本発明の姿勢推定装置は、上記構成に加え、従来のＧＮＳＳ姿勢推定装置の機能により得られた姿勢角を初期値とし、前記の拘束条件を有する相関器を用いることにより搬送波位相のマルチパス誤差を軽減し、各アンテナにおける搬送波位相φ_ｍ＋φ_ｋを推定して姿勢角を再度計算する手段を備えるようにした。なお、φ_ｍは基準となるアンテナにおける位相の推定値である。
また、本発明の姿勢推定装置は、上記構成に加え、再計算した姿勢角が収束したか否かを判定する手段を備え、収束していなければこの時の推定値を初期値として再び処理を繰り返し、収束するまで行い、その結果として姿勢角を高精度に推定する。また、マルチパス誤差が低減された搬送波位相を用い搬送波差分測位や精密単独測位手法における精度を向上させるようにした。 The attitude estimation apparatus according to the present invention includes a plurality of antennas mounted on a moving body, and uses an attitude angle information in a correlator that correlates a GNSS satellite signal acquired by each antenna and a replica signal generated inside the apparatus. A function of imposing the carrier phase difference calculated in 2 as a constraint condition is provided.

In addition to the above-described configuration, the attitude estimation apparatus of the present invention uses the correlator having the above-described constraint conditions, with the attitude angle obtained by the function of the conventional GNSS attitude estimation apparatus as an initial value, and is capable of multi-carrier phase. A path error is reduced, and a means for recalculating the attitude angle by estimating the carrier phase φ _m + φ _k at each antenna is provided. Note that φ _m is an estimated value of the phase in the reference antenna.
In addition to the above configuration, the posture estimation apparatus of the present invention further includes means for determining whether or not the recalculated posture angle has converged. If the posture angle has not converged, the estimated value at this time is used as an initial value to perform the process again. Repeat until convergence, and as a result, estimate the attitude angle with high accuracy. In addition, the carrier phase with reduced multipath error is used to improve the accuracy in the carrier differential positioning and precision single positioning methods.

The attitude estimation apparatus according to the present invention includes a plurality of antennas mounted on a moving body, and uses an attitude angle information in a correlator that correlates a GNSS satellite signal acquired by each antenna and a replica signal generated inside the apparatus. Since it has a function to impose the carrier phase difference calculated in 2 as a constraint condition,
As a result, the posture estimation apparatus of the present invention can perform posture estimation only by a GNSS receiver without using a posture detection device such as a gyro, and the estimation accuracy is improved as compared with the conventional case by reducing multipath errors. be able to. If this device is mounted on a moving body such as a ship, the position and orientation of the moving body can be estimated with higher accuracy than before, and it will make a significant contribution to earth environmental science and engineering, such as remote sensing from the moving body. Can do.

複数あるアンテナの相互位置関係は固定であるから、各ｄ_ｋ値は既知である。また、搬送波位相差φ_ｋは次式 (式２) で与えられる。

上記した式２の関係はＧＮＳＳ衛星からアンテナが直接受信した搬送波について成立するものであって、高層ビル等の構造物に反射して伝搬されたマルチパス誤差信号には成立しないことに着目する。次に、複数ある各アンテナで受信した信号と受信機内部で生成したレプリカ信号との相関処理を行うが、アンテナｋ(ｋ＝２〜ｎ)で受信した信号に対する相関値を計算する際に式２で計算した搬送波位相差を拘束条件として使用する。すなわち、アンテナで取得した信号に対するレプリカ信号の同相成分および直交成分を振幅をＡとしてそれぞれ次式（式３）とすると、

アンテナｋで取得した信号に対するレプリカ信号はそれぞれ、次式(式４)となる。

全アンテナに対する相関値から、受信信号に重畳されているマルチパス誤差信号が排除され、ＧＮＳＳ衛星からの直進搬送波を推定して特定できる。結果としてアンテナ１における位相の推定値φ_ｍが得られ、アンテナｋに対する位相の推定値はφ_ｍ＋φ_ｋとなる。 The principle of posture estimation in the posture estimation apparatus of the present invention using the method of correlating with the replica signal will be described. When a plurality (n) of GNSS antenna groups (Ant-1 to Ant-n) are mounted on a moving facility such as a ship, an aircraft, or a large vehicle and arranged in a three-dimensional space, one antenna Ant-1 The positional relationship between the other antenna Ant-k and the GNSS satellite will be discussed with reference to FIG. Although the actual positional relationship is three-dimensional, this figure is depicted two-dimensionally on a plane including the central positions of the three parties. The distance from Ant-1 and Ant-k of the antenna to the GNSS satellite is sufficiently large compared to the distance between Ant-1 and Ant-k of the antenna and can be regarded as being at infinity. Become. Now, let E be the elevation angle of the GNSS satellite viewed from the antenna with reference to Ant-1 of the antenna, and let d _k be the distance between the phase centers of Ant-1 and Ant-k of the antenna, and Ant-1 and Ant-k of the antenna. Is a posture angle θ, and the delay distance L that is the difference between the antenna Ant-1 and the GNSS satellite and the antenna Ant-k and the GNSS satellite is It is calculated by the following formula (Formula 1).

Since the mutual positional relationship between a plurality of antennas is fixed, each d _k value is known. The carrier phase difference φ _k is given by the following equation (Equation 2).

It should be noted that the relationship of Equation 2 above is established for a carrier wave directly received by an antenna from a GNSS satellite, and not for a multipath error signal reflected and propagated to a structure such as a high-rise building. Next, a correlation process is performed between a signal received by each of a plurality of antennas and a replica signal generated inside the receiver, and an expression is used when calculating a correlation value for a signal received by antenna k (k = 2 to n). The carrier phase difference calculated in 2 is used as a constraint condition. That is, when the in-phase component and the quadrature component of the replica signal with respect to the signal acquired by the antenna are set to amplitude A, respectively,

Each replica signal for the signal acquired by the antenna k is expressed by the following formula (formula 4).

The multipath error signal superimposed on the received signal is excluded from the correlation values for all the antennas, and the straight carrier wave from the GNSS satellite can be estimated and specified. As a result, an estimated value φ _m of the antenna 1 is obtained, and the estimated value of the phase for the antenna k is φ _m + φ _k .

  As shown in FIG. 1, the overall configuration of the posture estimation apparatus of the present invention includes a group 1 of a plurality of GNSS antennas 1 to N, a low noise amplifier (LNA) 2, an RF unit 3 including a bandpass filter, an amplifier, a mixer, and the like, an analog / Digital converter (ADC) 4, data processor 5 that processes signals from each antenna in the same manner as a normal GNSS receiver and outputs pseudorange, carrier phase, navigation message, pseudorange, carrier phase for each antenna , An arithmetic unit 6 for calculating the position and posture angle from the navigation message, and an estimator 7 for estimating the position and posture with high accuracy. The estimator 7 uses, as an initial value, the posture angle calculated by the calculator 6, the past output posture angle value of the estimator 7, or the current posture angle predicted value based on the past output value of the estimator 7.

The processing in the estimator 7 will be described along the flowchart shown in FIG. Since a plurality of antennas are mounted on the mobile equipment, the initial posture angle E is not accurately specified as in the conventional apparatus. The predicted value of the first incorrect posture angle E in Step 1 to compute the carrier phase difference phi _k in antenna pair as an initial value. In step 2, correlation calculation is performed with the phase difference as a constraint, and the carrier phase φ _m + φ _k at each antenna is estimated. The attitude angle E is calculated again from the carrier phase φ _m + φ _k estimated in step 3. Subsequently, in step 4, it is determined whether or not the estimation of the posture angle E has converged. If it has not converged, the estimated value at this time is used as an initial value, and the process is repeated from step 1 until convergence. If it converges, the process proceeds to step 5 where the antenna position is calculated using the estimated carrier wave value at that time, and a highly accurate position / posture angle value is output.
The position / orientation estimation apparatus of the present invention may be a precision point positioning (PPP) apparatus that performs precise positioning using GPS precise satellite orbits, clock estimates, and carrier observation data without using a reference station. .

  Since the position / orientation angle accuracy is improved by reducing the multipath error, it can be used in all GNSS application fields that require a highly accurate position or orientation angle. For example, it is an improved product of a GPS compass used in ships and the like. It can also contribute to the field of global environmental science and engineering, such as remote sensing from mobile objects.

It is a block diagram which shows the whole structure of the attitude | position estimation apparatus which concerns on this invention. It is a flowchart explaining the process in the estimator 7 of the attitude | position estimation apparatus which concerns on this invention. It is a figure explaining the positional relationship of one antenna Ant-1, another antenna Ant-k, and a GNSS satellite, and the constraint conditions in the attitude | position estimation apparatus of this invention.

Explanation of symbols

1 Antenna group 2 Low noise amplifier (LNA)
3 RF section 4 Analog / digital converter (ADC)
5 Data processor 6 Arithmetic unit 7 Estimator

Claims (4)

In a correlator that mounts a plurality of antennas on a moving body and correlates a GNSS satellite signal acquired by each antenna and a replica signal generated inside the apparatus, a carrier phase difference φ calculated by the following equation using attitude angle information A position / posture estimation device having a function of imposing _k as a constraint.

Where E is the elevation angle of the GNSS satellite viewed from the antenna, d _k is the distance between the phase centers of one antenna and the other antenna k, θ is the angle between the horizontal line of the lines connecting the positions of both antennas, and the attitude angle λ is the wavelength of the carrier wave. The attitude angle obtained by the function of the conventional GNSS attitude estimation device is set as an initial value, and the multipath error of the carrier phase is reduced by using the correlator having the above-described constraint conditions, and the carrier phase φ _m + φ _{k at} each antenna is reduced. The position / orientation estimation apparatus according to claim 1, further comprising means for estimating the angle and recalculating the attitude angle.
Φ _m is the estimated phase of the reference antenna.   A means to determine whether or not the recalculated attitude angle has converged. If it has not converged, repeat the process again using the estimated value at this time as the initial value until it converges. As a result, the attitude angle is highly accurate. The position / posture estimation apparatus according to claim 2, wherein   A means for determining whether or not the recalculated attitude angle has converged. If it has not converged, repeat the process again using the estimated value at this time as the initial value, and continue until convergence, reducing the multipath error. The position / posture estimation apparatus according to claim 2, wherein the phase is used to improve accuracy in carrier wave differential positioning or precision single positioning method.

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