EP0934506A2 - Procedes permettant d'estimer le biais d'un gyroscope au moyen du gps - Google Patents

Procedes permettant d'estimer le biais d'un gyroscope au moyen du gps

Info

Publication number
EP0934506A2
EP0934506A2 EP98939051A EP98939051A EP0934506A2 EP 0934506 A2 EP0934506 A2 EP 0934506A2 EP 98939051 A EP98939051 A EP 98939051A EP 98939051 A EP98939051 A EP 98939051A EP 0934506 A2 EP0934506 A2 EP 0934506A2
Authority
EP
European Patent Office
Prior art keywords
gyro
gps
heading
bias
movable vehicle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98939051A
Other languages
German (de)
English (en)
Other versions
EP0934506A4 (fr
Inventor
George Jeffrey Geier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motorola Solutions Inc
Original Assignee
Motorola Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Inc filed Critical Motorola Inc
Publication of EP0934506A2 publication Critical patent/EP0934506A2/fr
Publication of EP0934506A4 publication Critical patent/EP0934506A4/fr
Withdrawn legal-status Critical Current

Links

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
    • G01S19/38—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
    • G01S19/396—Determining accuracy or reliability of position or pseudorange measurements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
    • G01C21/26—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 specially adapted for navigation in a road network
    • G01C21/28—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 specially adapted for navigation in a road network with correlation of data from several navigational instruments
    • 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
    • G01S19/53—Determining attitude

Definitions

  • GPS global positioning satellite
  • DR Dead Reckoning
  • a DR system often takes the form of an interface to the transmission odometer of the vehicle to provide an indication of speed, in combination with a low cost gyro to track the vehicle's heading.
  • the accuracy of the DR system is critically dependent upon the accuracy to which the vehicle's heading is determined whereby each degree of heading error, in the absence of GPS, produces a cross-track position error which grows approximately as 1.7% of distance traveled.
  • the error associated with low cost rate gyros is generally dominated by their zero rate bias, which can be several degrees per second at turn on, and drift significantly with both time and temperature variations.
  • This rate bias if not removed, produces a heading error which grows linearly, proportional to the bias, in the absence of GPS heading information.
  • This heading error growth produces a quadratic growth in cross track position error, in the absence of GPS position information. Calibration of this zero rate bias is therefore essential in using the low cost gyro, even for relatively short duration lapses in GPS coverage.
  • U.S. Patent number 5,416,712 discloses a method, whereby a low pass filter is used to update the gyro's zero rate bias from measurements which are made during stationary periods.
  • a similar approach is used, with zero rate bias measurements input to a Kalman filter which estimates the bias.
  • these methods are unreliable or ineffective if Hall effect sensors are not installed in the host vehicle whereby variable reluctance sensors are typically used, which do not reliably sense low vehicle speeds.
  • variable reluctance sensors the vehicle may be moving (and so turning) when the sensor indicates that the vehicle is stationary. Further, speeds up to several miles per hour may not be sensed. Accordingly, traditional methods of gyro bias calibration, when used with variable reluctance sensors, can undesirably interpret vehicle turns as gyro zero rate bias, which can lead to excessive errors in the navigation system.
  • This invention permits reliable and automatic estimation and calibration of the gyro zero rate bias without requiring the installation of Hall effect sensors.
  • Three methods, which can be used individually or in combination, are disclosed whereby two of the methods are based upon innovative GPS detection schemes, referred to as a "GPS gyro", used for detecting vehicle heading change, and a “GPS accelerometer”, used for detecting stationary periods. Note that neither of these methods requires information from the vehicle's odometer. Note however that the effectiveness of each method can be improved by using vehicle speed data.
  • the third method operates at periodic intervals, without requiring knowledge of stationary or straight driving, and makes use of a Kalman filter model for open loop heading error to extract the contribution of and so estimate the gyro bias.
  • FIG. 1 is a block diagram illustrating the components of a GPS receiver integrated with a gyro and transmission odometer-based DR system installed in a movable vehicle;
  • FIG. 2 is a flowchart which indicates the use of a GPS gyro-based approach in gyro bias calibration in accordance with a preferred embodiment of the present invention
  • FIG. 3 is a flowchart which indicates the use of a GPS accelerometer-based approach in gyro bias calibration in accordance with a preferred embodiment of the present invention.
  • FIG. 4 is a flowchart which indicates the use of an open loop heading propagation in conjunction with a Kalman filter for gyro bias calibration in accordance with a preferred embodiment of the present invention.
  • FIG. 1 illustrates the components of the vehicle navigation system which could make use of the present invention, comprised of a GPS receiver 30, with a serial port input message added for input of DR sensor information to the receiver (i.e., the gyro sensed heading change, and odometer derived distance travelled) and software added to the receiver's microprocessor to implement the gyro bias calibration.
  • the gyro can be placed anywhere in the vehicle: its sensitive axis, however, must be oriented toward the local vertical to sense heading rate.
  • FIG. 1 a block diagram illustrating components of a GPS and DR system installed in a movable vehicle 10 is shown.
  • FIG. 1 includes DR processor 40 and GPS receiver 30 that is coupled to a GPS antenna 20, all of which are suitable for installation in movable vehicle 10.
  • Also shown in FIG. 1 are a plurality of GPS satellites 5 for generating GPS signals that are received by the GPS receiver 30 for enabling GPS receiver 30 to determine the position of movable vehicle 10 in a well known manner.
  • four satellites are required for enabling GPS receiver 30 to obtain a three-dimensional position fix for vehicle 10.
  • DR processor 40 which may be embedded in the GPS receiver, receives GPS data 32, such as Doppler or heading measurements, from GPS receiver 30, and accepts angular rate data 45 from a gyro 35, and speed data 46 from odometer interface 47 which may be coupled to the transmission of the vehicle.
  • the DR processor 40 also outputs the integrated position data 50 to an application specific device 60.
  • application specific device 60 may be a separate processor which implements a map matching algorithm to locate the vehicle on the correct street and to generate a display visible to the driver.
  • application specific device 60 may be a separate processor which implements a map matching algorithm to locate the vehicle on the correct street and to generate a display visible to the driver.
  • application specific device 60 may provide the necessary interface to a cellular phone or radio for establishing a communication link to proper third parties thereby informing such third parties of the location of movable vehicle 10.
  • GPS Doppler residuals are collected from the GPS receiver 300 and used in a unique way to determine when the vehicle's heading is essentially constant. This enables an accurate measurement of the gyro bias when the vehicle is moving. Each Doppler residual is found by removing the contribution of the (known) satellite velocity from the measured Doppler shift to that satellite, which is derived by the receiver's tracking loop. Successive pairs of Doppler differences are differenced to form a Doppler double difference ⁇ Dopp res in 310, which is used to determine the heading change 320 using Eqn. (1) below:
  • ⁇ HGPS 13 ( ⁇ Dopp res - ⁇ v ⁇ vf actor ) / (v ⁇ Hf actor ) (1)
  • ⁇ Dopp res (Dopp j -eg 1 - Dopp res J)k - opp ⁇ 1 -
  • Dopp r esJ Doppler double difference
  • i and j are the two satellite indices
  • k is a time index
  • Azj, Azj are the two satellite azimuth angles.
  • H is the heading at the previous second.
  • Eqn. (1) utilizes only two Doppler measurements. Also note that v and ⁇ v in Eqn. (1) are determined as a function of DR sensor availability. However, if vehicle speed data is supplied (i.e., an interface to the vehicle's transmission or wheel sensors exists), then this can be used to estimate both speed and speed change in Eqn. (1). On the other hand, if such an interface does not exist, speed and acceleration information are derived from GPS.
  • each pair-wise difference can be used to construct a Doppler double difference and solve for a heading change.
  • Each of these heading changes ⁇ HGPS 1J is optimally combined using Weighted Least Squares (WLS) 330, where the heading change solution from each Doppler pair is weighted inversely proportional to its error variance.
  • WLS Weighted Least Squares
  • ⁇ 2 ⁇ H I 2 ( ⁇ PRR 1 + ⁇ 2 PRRJ) + ⁇ 2 QSF ⁇ v2 ⁇ factor 2 +
  • OM 2 variance associated with road slope
  • ⁇ ⁇ M 2 variance associated with road slope change.
  • an integrity test statistic is computed in 340. This statistic is the normalized root-sum-square of the solution residuals (i.e., the difference between the WLS solution and the heading change solution found from each Doppler double difference).
  • a solution residual magnitude which is excessively large relative to the assumed heading change solution measurement variance ⁇ ⁇ H will invalidate the WLS solution, and the integrity test 350 will fail. Failure of the integrity test will cause the gyro bias estimator to be bypassed.
  • the integrity test 350 will pass, and the magnitude of the WLS heading change will be examined in 360.
  • ⁇ HGPSgyro is the WLS solution for heading change, found by inversely weighting (according to O" 2 ⁇ H ) the solutions from each GPS Doppler pair AHQPS ⁇ ; and ⁇ Hgyro is the gyro sensed heading change.
  • Eqn. (3) could alternatively be formed by excluding the subtraction of AHGPSgyro whereby the significance of its inclusion is determined from the magnitude of the threshold used for detection of straight travel in 360.
  • the contribution of ⁇ HGPSgyro in Eqn. (3) is only representative of the WLS solution error.
  • use of a larger threshold in 360 will likely include periods of slow vehicle heading change, when subtraction of ⁇ HGPSgyro n Eqn. (3) is important.
  • b is the bias estimate used to compensate the gyro output, initialized to zero; and k is the filter gain.
  • this first approach for estimating the zero gyro bias includes making use of GPS heading information in a unique way to achieve a gyro bias estimate.
  • the GPS headings are used with odometer derived speed, when available, to form an angular rate estimate ⁇ HGPSgyro-
  • This rate estimate is highly accurate, since it makes use of Doppler double differencing, which removes the dominant error source in each GPS heading (i.e., the contribution of SA).
  • the rate estimate can be used to determine when the vehicle is travelling nearly straight, when the gyro bias can be reliably measured.
  • ⁇ HGPSgyro can alternatively be found by simply differencing successive headings derived directly from GPS.
  • this simpler approach may be adequate in many embodiments of the invention, and replaces the sequence of operations indicated in steps 300-350 of FIG. 2 by a simple differencing of the GPS headings.
  • GPS Doppler information is also used in a unique way to determine when the vehicle is not accelerating whereby this information can be accurately estimated from GPS information, since the acceleration associated with Selective Availability (SA), the dominant source of GPS Doppler error, is below the level of any vehicle acceleration.
  • SA Selective Availability
  • speed information derived from either GPS (i.e., without the odometer interface), and/or from the (non Hall- effect sensing) odometer, and the sensed speed is below some threshold, it can be reliably determined that the vehicle is stationary.
  • the "GPS accelerometer” approach begins by collecting the available Doppler residuals from the receiver 400, as was done with the GPS gyro approach.
  • the Doppler double differences are then formed 410, as previously detailed below Eqn. (1).
  • Each Doppler double difference can then be used to estimate the change in vehicle velocity 420, as given by Eqn. (5) below.
  • ⁇ vGPS 1] [ ⁇ Doppresij + ⁇ H ( ⁇ Hfactor)] / ⁇ vfactor (5)
  • ⁇ H is the heading change sensed by the gyro.
  • Eqn. (5) is based on information from only a pair of satellites. Generally, more satellites are available, and the acceleration determined from each pair will be combined optimally using WLS 430, where each velocity change solution will be weighted inversely proportional to its error variance.
  • an integrity test statistic is formed 440 before computing the acceleration estimate. This statistic is this normalized root- sum-square of the solution residuals (i.e., the difference between the WLS solution and the velocity change solution found from each Doppler double difference).
  • a solution residual magnitude which is excessively large relative to the assumed velocity change solution measurement variance ⁇ 2 ⁇ v will invalidate the WLS solution, and the integrity test 450 will fail. Failure of the integrity test 450 will cause the gyro bias estimator to be bypassed.
  • the solution residuals are consistent, the integrity test 450 will pass, and the magnitude of the WLS velocity change solution is tested 460. If the computed velocity change is sufficiently small, it is concluded that the host vehicle is not accelerating, and a test 470 for a stationary condition may be performed. If the velocity change magnitude test 460 fails, on the other hand, the bias estimation is bypassed for this cycle.
  • the gyro sensed heading change is a direct measurement of the gyro bias 480, as indicated in Eqn. (7), and can (again) be applied to a low pass or Kalman filter to update 490 the estimate of the gyro bias, as described previously by Eqn. (4).
  • this second approach for estimating the zero gyro bias includes making use of GPS acceleration information to achieve a gyro bias estimate.
  • Doppler double differencing is used, which removes the dominant error source in each GPS determined speed (i.e., the contribution of SA).
  • the acceleration estimate can be used to determine when the vehicle is nearly stationary, when the gyro bias can be reliably measured.
  • the gyro bias estimation method based on Kalman filter extraction from an "open loop" propagation of the DR system heading is illustrated.
  • the open loop propagation is initiated periodically from a reliable GPS heading 500.
  • error variances denoted ⁇ 2 HOL anc * ⁇ 2 H ⁇ b > which represent the uncertainty associated with the open loop propagation of heading, and the uncertainty attributable to the uncompensated gyro bias, are initialized, as indicated in the equations below.
  • H OL H GPSstart (8)
  • HGPSstart i s the GPS heading used to initialize the open loop propagation.
  • HQL HQL + ⁇ Hgyro (11) where ⁇ Hgy ro is the gyro sensed heading change, compensated with the current gyro bias estimate.
  • ⁇ 2 HOL ⁇ 2 HOL + ⁇ 2 HGSF + ⁇ 2 H ⁇ b ( 12 )
  • o ⁇ b is the error variance associated with the uncompensated gyro bias.
  • HGPSstop is the GPS heading at the time at which the open loop propagation is stopped
  • HGPS is the GPS derived heading.
  • the bias must be extracted from the measurement expressed by Eqn. (15) using a Kalman filter which models the error contributors to H 0L -
  • the measurement noise and residual variances are computed in 550, as given by the equations below.
  • ⁇ 2 n ⁇ 2 HGPSstart + ⁇ 2 HGPSstop + ° 2 ngyro ( 16 )
  • ° 2 HGPSstart i s the error variance assigned to the GPS heading used to initialize the open loop propagation in Eqn. (8)
  • ⁇ 2 HGPSstop i s the heading error variance assigned to the GPS heading at the end of the propagation interval, used in Eqn. (15) to construct the bias measurement
  • ⁇ " ngyro is the error variance associated with the noise in the gyro reading itself, including quantization error.
  • a new open loop propagation is initiated 590 by resetting the error variances and the open loop heading propagation, using equations identical to those used for initialization 500 (i.e., Eqns. (8) through (10) above). Following this reset of the propagation, 590, the open loop propagation in 510 and 520 will be continued on the next cycle.
  • a failure counter is incremented 600 each time that a residual test 560 failure occurs. If the failure counter has not reached a maximum allowable value (e.g., representing five to ten successive residual test failures) in test 610, the bias estimation is bypassed. On the other hand, if the maximum allowable failure count is reached in test 610, the bias estimate and its error variance are reset to the measured values 620, and the error variances associated with the open loop heading propagation are similarly reset 630, as given by the equations below.
  • a maximum allowable value e.g., representing five to ten successive residual test failures
  • the present invention discusses three different methods which are used to form the bias measurement, as indicated for the GPS gyro based approach in Eqn. (3), the GPS accelerometer based approach in Eqn. (7), and the open-loop heading propagation approach in Eqn. (15). Although each of these equations is quite different, they are measuring the same (zero-rate) bias. The differences in the equations arise from the fundamentally different ways in which the bias measurements are constructed. In particular, for the GPS gyro approach, the vehicle may be turning slowly, so it is necessary to subtract ⁇ HGPSgyro in forming the bias measurement. On the other hand, when using the GPS accelerometer to sense a stationary condition, a pure bias measurement can be made from the gyro reading. Finally, in the open loop propagation based approach, the vehicle is neither travelling straight nor stationary, necessarily, so the bias must be extracted from the measured difference between the open loop heading propagation and GPS determined heading.

Abstract

En ajoutant au récepteur GPS (30) une certaine forme de navigation à l'estime (DR), un gyroscope (35) par exemple, on remplit les trous dus à la perte de la couverture GPS. La présente invention permet d'estimer et de caler, d'une manière automatique et fiable, le biais du gyroscope à vitesse nulle. Elle concerne en particulier trois procédés spécifiques (figures 2-4): le premier (figure 2) utilise un 'gyroscope GPS' pour détecter un changement de cap du véhicule, le deuxième (figure 3) utilise un 'accéléromètre GPS' pour détecter des périodes stationnaires, et le troisième (figure 4), qui utilise un modèle de filtre de Kalman pour l'erreur de cap en boucle ouverte, permet d'extraire la contribution de ladite erreur, et donc de l'estimer.
EP98939051A 1997-04-07 1998-04-02 Procedes permettant d'estimer le biais d'un gyroscope au moyen du gps Withdrawn EP0934506A4 (fr)

Applications Claiming Priority (3)

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US83496697A 1997-04-07 1997-04-07
US834966 1997-04-07
PCT/US1998/006568 WO1998049577A2 (fr) 1997-04-07 1998-04-02 Procedes permettant d'estimer le biais d'un gyroscope au moyen du gps

Publications (2)

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EP0934506A2 true EP0934506A2 (fr) 1999-08-11
EP0934506A4 EP0934506A4 (fr) 2001-01-17

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ATE345487T1 (de) * 1999-09-16 2006-12-15 Sirf Tech Inc Navigationssystem und -verfahren zum verfolgen der position eines objektes
US6380890B1 (en) * 2000-08-11 2002-04-30 Motorola, Inc. Information appliance system having a navigational position generator and method
US7103477B1 (en) 2005-08-08 2006-09-05 Northrop Grumman Corporation Self-calibration for an inertial instrument based on real time bias estimator
US8239133B2 (en) * 2008-07-02 2012-08-07 O2Micro, International Global positioning system and dead reckoning (GPSandDR) integrated navigation system
WO2010001968A1 (fr) * 2008-07-02 2010-01-07 独立行政法人産業技術総合研究所 Dispositif de mesure de positionnement d'un corps mobile
US20120173195A1 (en) * 2010-12-03 2012-07-05 Qualcomm Incorporated Inertial sensor aided heading and positioning for gnss vehicle navigation
CN106500693B (zh) * 2016-12-07 2019-06-28 中国电子科技集团公司第五十四研究所 一种基于自适应扩展卡尔曼滤波的ahrs算法
EP3667236B1 (fr) 2018-12-13 2023-09-06 Ordnance Survey Limited Procédé de détermination de données de positionnement
CN110780319A (zh) * 2019-09-16 2020-02-11 蓝箭航天空间科技股份有限公司 运载火箭组合导航功能验证系统及验证方法

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EP0934506A4 (fr) 2001-01-17
WO1998049577A3 (fr) 1999-03-04
WO1998049577A2 (fr) 1998-11-05

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