JPH0820263B2 - Vehicle orientation correction device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle azimuth correcting device used in a vehicle position detecting device for detecting the position of a vehicle traveling on an arbitrary road.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting the position of a vehicle traveling in an arbitrary portion of a road traffic network, a process of performing necessary processing on output signals from a distance sensor, a direction sensor and both sensors. A dead reckoning navigation system has been proposed, which is provided with a device and obtains vehicle position data based on a distance change amount ΔL that accompanies traveling of a vehicle and a vehicle direction θ. In this method, for example, the east-west component Δx of ΔL (= ΔL × cos
θ) and the north-south direction component Δy (= ΔL × sin θ) are calculated, and the above-mentioned respective components Δx and Δy are added to the previous position data (Px ′, Py ′) to obtain the current position data (Px, This is a method of calculating Py).

In the above method, the vehicle heading data is required in addition to the distance change amount in calculating the position data. And if the direction data contains an error,
The error is accumulated and the position data becomes inaccurate. For this reason, the vehicle position and heading data must be accurate.

[0004]

By the way, there is a method of using a sensor (geomagnetic sensor) for detecting an absolute azimuth as a method of acquiring the azimuth data at the time of departure of the vehicle. However, the azimuth detected by the geomagnetic sensor usually includes the following error. That is, the geomagnetic sensor that detects the geomagnetism and knows the absolute azimuth of the moving body detects the strength of the weak earth magnetic field, and if the moving body is magnetized, an error will occur in its output data. . Initialization processing of the geomagnetic direction sensor is performed to cancel this error, but especially when the vehicle is running, especially when crossing railroad crossings, power cable buried locations, iron bridges, highways with noise barriers, and valleys of high-rise buildings. An error occurs again due to a change in the amount of magnetization of the vehicle body, often under the influence of a strong electromagnetic field from the outside.

On the other hand, a vehicle may be equipped with a GPS receiver. GPS (Global Positioning System) is a technology for positioning one's position by using radio waves from GPS satellites, and its principle is radio waves generated by a plurality of artificial satellites orbiting in a predetermined orbit. By measuring the propagation delay time of the
It is to measure a dimensional position. Positioning the position of the vehicle by mounting the GPS receiver itself is an extremely effective means for detecting the position of the vehicle. However, in order to directly determine the direction of the vehicle using this GPS receiver. Has some problems. That is, when measuring the Doppler shift generated by receiving radio waves from GPS satellites while traveling, the vehicle needs to be traveling at a high speed to some extent. Therefore, the direction cannot be measured unless the vehicle is traveling on the highway, and therefore it cannot always be used for correcting the direction of the vehicle.

The present invention has been made in view of the above problems, and is used when detecting the position of a vehicle based on distance data and azimuth data associated with traveling, and detects the position of the vehicle. It is an object of the present invention to provide a vehicle azimuth correction device that can correct the azimuth used for the vehicle direction and can obtain a more accurate azimuth, position, or traveling locus.

[0007]

In order to solve the above-mentioned problems, a vehicle heading correction device of the present invention is a traveling distance sensor, a heading sensor, and a vehicle traveling obtained from the traveling distance sensor and the heading sensor. Used in a vehicle position detecting device having an estimated position detecting means for detecting the position of the vehicle based on the distance data and the azimuth data, a GPS receiver,
Specify the combination of satellites used for positioning to the GPS receiver
Combination specifying means that can be used, and the above combination specifying hand
Orientation dependent on the constellation of satellites in a combination specified by stages
Error ellipse calculation means for obtaining positioning error with
Supplied from GPS receiver corresponding to the combination of satellites
Store multiple GPS vehicle position data at each time
The storage means to store and the vehicle that has traveled between the two points
A set of satellites that minimizes the positioning error in the direction perpendicular to the moving direction.
The GP at the two points of time when the combination is adopted and the combination is adopted.
S vehicle position data is acquired from the storage means to obtain a GPS vehicle
A first calculation means for obtaining a moving direction of the vehicle connecting the positions;
Based on the difference between the estimated vehicle positions detected between the above two time points
Second calculating means for obtaining the moving direction of the vehicle, and these two
Comparing the moving direction of the vehicle obtained by the calculation means of
Azimuth correction that finds the difference and corrects the azimuth of the vehicle using this difference
And the correct means .

[0008]

[Function] With the above vehicle orientation correction device, two time points have passed.
Positioning perpendicular to the direction of travel of the vehicle
At the two points in time for the satellite combination that minimizes the error
GPS vehicle position data is obtained and detected between the two points above
Based on the difference between the estimated vehicle positions,
Comparing the movement directions of these two vehicles to obtain the difference,
The orientation of the vehicle can be corrected using the difference in

The combination designating means designates a combination of satellites used for positioning with respect to the GPS receiver. That is,
There are currently 17 GPS satellites that orbit the earth (2 in the future).
There will be four) and there will be 3 to 4 satellite combinations to choose from. The shape of the error ellipse of the vehicle position data supplied from the GPS receiver differs depending on which satellite combination is selected. So while the two points have passed
Reads the moving direction of the vehicle based on a combination of satellite position error output of the movement direction and perpendicular direction is minimum traveling vehicle from the storage means. "Running after the two points have passed"
For example, a temporary combination of satellites is used in
GPS vehicle determined based on (any combination is acceptable)
The moving direction connecting both positions may be adopted.

This will be described with reference to FIG. The vehicle position obtained by the estimated position detecting means when the GPS is first acquired (referred to as "estimated vehicle position") is O, and the estimated vehicle position obtained by the estimated position detecting means is obtained when the second acquisition is performed. Is P, and the traveling locus therebetween is L. And the GP obtained when the first acquisition was made
The vehicle position calculated from the S position data (referred to as "GPS vehicle position") is O1 , and the GPS vehicle position calculated from the position data obtained when the second acquisition is performed is P1.

The GPS vehicle position O1 and the estimated vehicle position O may be different or may coincide with each other. The coincidence occurs when the estimated position detecting means adopts the GPS vehicle position O1 as the initial position of the vehicle when the GPS vehicle position O1 is acquired. However, since the object of the present invention is the correction of the azimuth, the initial position Do not necessarily have to match. However, in the case of explanation in the drawings, it is easier to explain them by overlapping, and therefore the origins O and O1 are drawn in an overlapping manner in the drawings.

The coordinates of the estimated vehicle position P are (x, y) and the coordinates of the GPS vehicle position P1 are (x1, y1). It is assumed that the estimated position detection means adopts the initial azimuth θo at the origin O when detecting the estimated vehicle position P. On the other hand, based on the coordinates (x1, y1) of the GPS vehicle position P1, the direction α of the vector OP1 at the origin O can be known from the following equation (a).

Α = tan ^-1 (y1 / x1) (a) Here, the error of the GPS vehicle position P1 becomes a problem. The distribution of the error of the GPS vehicle position P1 becomes an ellipse as is known, and its shape differs depending on the combination of satellites used for positioning. For example, as shown in FIG. 2, when the satellites 1, 2, 3, 4 in the north-south direction are selected, the error ellipse of the GPS vehicle position P1 becomes an ellipse elongated in east and west. If satellites 5, 2, 6, 7 in the east-west direction are selected, GPS
The error ellipse of the vehicle position P1 becomes a slender ellipse in the north and south.

The relationship between the major axis direction of the ellipse and the direction OP1 is illustrated in FIG. 3A and 3B show a case where the major axis direction of the ellipse and the direction OP1 do not match. FIG. 3C shows a case where the major axis direction of the ellipse is closest to the direction OP1. FIG.
In the cases (a) and (b), since the true GPS vehicle position P1 is within the ellipse, the angle viewed from the origin O to the major axis of the ellipse, that is, the azimuth error is relatively wide, whereas in FIG. In case (c), the angle from the origin O to the minor axis of the ellipse is relatively small. By selecting the combination of satellites in this way, the heading error of the GPS vehicle position P1 can be made sufficiently smaller than the heading error of the estimated vehicle position P.

Since the combination of satellites when positioning the origin O and the combination of satellites when positioning the GPS vehicle position P1 are kept the same,
The offset position error from the true vehicle position to the GPS vehicle position P1 can be canceled and the accuracy of the direction OP1 can be improved. This is because the offset position error appears in almost the same direction and the same magnitude unless the satellite combination is changed.

Therefore, from the GPS vehicle position data stored in the storage means, a combination of satellites whose elliptical shape is the narrowest in the direction of the vector OP1 (corresponding to FIG. 3 (c)) is selected (this combination is In order to cancel the offset error, it is necessary to fix it without changing it until a series of vehicle orientation correction procedures is completed.) The GPS vehicle position related to this satellite combination is read out, and the position of the origin O and the movement of the vehicle are newly read. When the direction is obtained and the formula (a) is applied to obtain the direction α, the direction α can be regarded as the true direction.

Further, based on the coordinates (x, y) of the estimated vehicle position P, the direction β of the vector OP at the origin O can be known by the following equation (b). β = tan ⁻¹ (y / x) (b) Therefore, if the difference between the direction β and the direction α is α−β = Δθ, the absolute azimuth θ of the vehicle can be corrected using the difference Δθ. That is, if “×” represents a vector product and “·” represents a scalar product, tan Δθ = tan (α−β) = sin (α−β) / cos (α−β) = OP × OP1 / OP · OP1 = (X y1-x1 y) / (x x1 + y y1) Therefore, Δθ = tan ^-1 (x y1-x1 y) / (x x1 + y y1)… (c). Therefore, the azimuth θ'obtained by θ + Δθ = θ '... (d) can be used as the absolute azimuth of the vehicle again.

If the initial azimuth θo is modified, Δθ
If the above is added to the initial azimuth θo, the traveling locus of the vehicle from the origin O can be recalculated by using the azimuth θo ′ obtained by θo + Δθ = θo ′ (e). In this way, a more accurate traveling locus L'can be obtained.

[0019]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 4 shows a block diagram of a vehicle position detection device for implementing the vehicle orientation correction device of the present invention. The vehicle position detection device includes wheel speed sensors 1a and 1b that detect the rotational speeds of the left and right wheels, a gyro that detects a turning angular velocity (an optical fiber gyro that reads the turning angular velocity as a phase change of interference light, and a cantilever of a piezoelectric element). (A vibration gyro that detects a turning angular velocity using vibration technology, a mechanical gyro, etc.) 2, a geomagnetic sensor 3 that detects an absolute direction of a vehicle based on geomagnetism, a GPS receiver 4, and a geomagnetism. An azimuth estimating unit 5 that estimates the current azimuth of the vehicle based on the initial azimuth input from the sensor 3 or the initial azimuth correcting unit 7 and the data of the azimuth change amount detected by the gyro 2, and the wheel speed sensor 1a,
The initial position (vehicle position set by the keyboard 10 or G
The travel distance data from the vehicle position input from the PS receiver 4) is calculated, and the azimuth data output from the azimuth estimation unit 5 is acquired to calculate a travel locus starting from the initial position by dead reckoning. A position detecting unit 6, an initial azimuth correcting unit 7, a navigation controller 8, and a road map stored in a map memory 11 and a display 9 for displaying a vehicle position, a azimuth, a traveling locus, etc. on a CRT, a liquid crystal display or the like. Have

The map memory 11 is a cassette tape or a CD.
-A storage medium such as a ROM, DAT, semiconductor memory, or IC memory is used, and a road network within a predetermined range as conventionally known,
Data such as intersections and railway transportation networks are stored in the form of combinations of nodes and links. The navigation controller 8 is composed of a graphic processor, an image processing memory, etc., and performs a search for a map displayed on the display 9, an input of an initial position, a switching of scales, scrolling, and the like.

The initial azimuth correction unit 7 specifies the combination of satellites used for positioning to the GPS receiver 4, and
Based on the two position data received by the GPS receiver 4, the moving direction α of the vehicle during the reception of these two times is obtained, and the above-mentioned two times based on the vehicle position data output by the position detection unit 6. The moving direction β of the vehicle during the reception of is obtained, and the absolute azimuth of the vehicle is corrected based on the difference Δθ in the moving direction of the vehicle thus obtained.

The operation of the vehicle position detecting device having the above structure will be described. First, the driver turns on the key to start the vehicle position detecting device before traveling, operates the keyboard 10 to select a road map within a predetermined range including the current position from the map memory 11, and displays it on the display 9. . Then keyboard 1
Operate 0 to set the initial position of the vehicle. This setting is performed by moving the cursor indicating the position of the vehicle on the map. At this time, the initial direction of the vehicle is set by capturing the output of the geomagnetic sensor 3. In this way, the data representing the initial position and the initial azimuth of the vehicle are supplied to the azimuth estimating unit 5 and the position detecting unit 6.

After the completion of the above series of initial settings, the vehicle is started, and the position detecting section 6 calculates the traveling distance data from the initial position based on the wheel rotation speed signals of the wheel speed sensors 1a and 1b, and the azimuth estimating section. At 5, the present azimuth is integrated based on the angular velocity data of the gyro 2. Then, the position detecting unit 6 calculates the traveling locus data based on the both data and supplies it to the navigation controller 8. The navigation controller 8 displays the vehicle position / direction and the traveling locus on the screen of the display 9 together with the road map.

Further, the initial azimuth correcting unit 7 knows the orbital position of the GPS satellite at the current time from a known table or the like, and the major axis direction of the error ellipse is the most azimuth of the vehicle obtained by the temporary combination of the satellites. Select the matching satellite combination.
Then, the combination is instructed to the GPS receiver 4 and the vehicle position data relating to the combination is output.
Note that the GPS receiver 4 is instructed to combine satellites.
The method is well known, but will be briefly described here. GPS
The transmitted radio waves of are using the spread spectrum method.
The code signal contains a subframe that specifies the satellite number.
Are included. Therefore, the GPS receiver 4
Then, in the code synchronization circuit, the code corresponding to the satellite number is
If you use code pattern to synchronize the code,
Can retrieve the navigation message from the satellite
It How to find the error ellipse is also well known, but here
Explain. Covariance matrix (positioning precision) obtained by satellite constellation
Used to calculate GDOP, which is the evaluation coefficient of degree. In two dimensions
HDOP, represented as PDOP in 3D)
Pseudo-distance in the longitude and latitude directions
Expansion coefficient of standard deviation σ ₀ of measurement error (σ _xx , σ _yy )
Is used to give the following equations showing the standard deviations σ _x , σ _y
It σ _x = σ _xx σ _{0 0} σ _y = σ _yy σ ₀ The correlation coefficient ρ _xy is also an element of the covariance matrix σ _xy
^{Using 2} gives: ρ _xy = σ _xy ² / σ _xx σ _yy These may be substituted into the following equation representing the error ellipse. ^{_{x 2 / σ x 2 -2ρ xy}} xy / σ x σ y -y 2 / σ y 2
= (1-ρ _xy ² ) C This ellipse is called a covariance ellipse. Where the square root of C is the ellipse
A random variable inside this ellipse, which is proportional to the length of the axis of the circle
The probability P of observing x and y is a function of C, and P = 1-exp (-C / 2) (Okuda, Yasuda "
Te] IEICE Transactions Vol. J75-BI
I, No. 2, pp. 138-144, 1992 2
Month). The initial azimuth correction procedure in the initial azimuth correction unit 7 when the vehicle position data is input will be described in detail.

First, when the first vehicle position data (Xo, Yo) for one combination of satellites is input from the GPS receiver 4, the azimuth θo at that time is acquired from the azimuth estimating unit 5,
Stored in memory together with vehicle position data (Xo, Yo). Since the vehicle position data (Xo, Yo) at this time is input to the position detection unit 6 as initial position data, the position detection unit 6 resets the current position to (Xo, Yo), and the current position (Xo, Yo) , Yo)
The vehicle position is calculated starting from. Note that the vehicle position data relating to a plurality of other combinations of satellites at this time are also stored in the memory.

Next, when the second vehicle position data (X1, Y1) relating to the temporary combination is input from the GPS receiver 4, the initial azimuth correcting unit 7 determines the current azimuth data θ at that time as the azimuth estimating unit 5. Estimated vehicle position data (X, Y)
Is acquired from the position detection unit 6. Then, based on these data, the estimated movement amount (x, y) = (X, Y)-(Xo, Yo) of the vehicle during these two receptions is obtained, and based on the GPS reception data, The reception movement amount (x1, y1) = (X1, Y1)-(Xo, Yo) of the vehicle during the above two receptions is obtained. Then, the combination of satellites whose major axis of the ellipse is closest to the direction (x1, y1) is obtained, and the first and second vehicle position data relating to this combination are obtained from the memory. And
Azimuth estimation error Δθ with direction (x, y)
Then, the initial azimuth can be corrected by adding this to the initial azimuth θo.

The initial azimuth θo ′ thus modified
Is supplied to the azimuth estimating unit 5, the azimuth estimating unit 5 recalculates the azimuth data of the vehicle based on the initial azimuth θo ′ by utilizing the idle time, and the position detecting unit 6 calculates the recalculated azimuth data. The travel locus data is calculated again based on In this recalculation process, the azimuth data and the traveling distance data acquired from the gyro 2 and the wheel speed sensors 1a and 1b are stored in a predetermined memory.

The travel locus data recalculated by the position detecting unit 6 in this manner is input to the navigation controller 8 and displayed on the display 9. Therefore, the locus displayed on the display 9 is the GPS
The correct trajectory is corrected each time the data is received.

[0029]

As described above, according to the present invention, the GPS
The moving direction of the vehicle determined during the acquisition of the vehicle position data twice, using the difference between the moving direction of the vehicle obtained based on the estimated position data outputted by the estimation position detecting means towards position of the vehicle Can be corrected, so that a more accurate azimuth can be determined. In this case, the combination of satellites used for positioning can be designated to the GPS receiver with the smallest azimuth error, so that the azimuth correction error becomes very small. Also, offset error can be offset.

Further, if the initial azimuth is corrected by this, the traveling locus to be advanced can be recalculated, and a more accurate traveling locus can be obtained.

[Brief description of drawings]

FIG. 1 is a vehicle travel locus diagram for explaining a vehicle orientation correction method.

FIG. 2 is a diagram showing the arrangement of GPS satellites at a certain time.

FIG. 3 is a diagram illustrating a relationship between a major axis direction of an error ellipse and a direction OP based on an estimated vehicle position. (a) and (b) show the case where the major axis direction of the ellipse does not coincide with the direction OP, and (c) shows the case where the major axis direction of the ellipse is closest to the direction OP.

FIG. 4 is a block diagram of a vehicle position detection device for implementing the vehicle orientation correction device of the present invention.

[Explanation of symbols]

 1a, 1b Wheel speed sensor 2 Gyro 4 GPS receiver 5 Direction estimation unit 6 Position detection unit 7 Initial direction correction unit

Claims (1)

[Claims] 1. A vehicle having a mileage sensor, an azimuth sensor, and an estimated position detecting means for detecting the position of the vehicle based on the mileage data and the azimuth data of the vehicle obtained from the mileage sensor and the azimuth sensor. Used in a position detection device, specifies a GPS receiver and a combination of satellites used for positioning with respect to the GPS receiver
And the satellites of the combination specified by the above-mentioned combination specifying means.
Error ellipse for determining positioning error with directivity depending on position
It is supplied from the GPS receiver corresponding to the combination of calculation means and multiple satellites.
Stores multiple GPS vehicle position data at each time point
The storage means to be kept and the direction perpendicular to the moving direction of the vehicle that has traveled between the two points
A satellite combination that minimizes directional positioning error is used.
GPS vehicle position data at the two points in time depending on the combination of
A vehicle connecting between GPS vehicle positions by acquiring the
Based on the difference between the first calculation means for obtaining the moving direction of the vehicle and the estimated vehicle position detected between the two time points.
Second calculating means for obtaining the moving direction of the vehicle and the moving direction of the vehicle obtained by these two calculating means
Compare the directions to find the difference, and use this difference to fix the heading of the vehicle.
A vehicle azimuth correction device having a correct azimuth correction means .