JPH01307618A - Vehicle position detector - Google Patents

Abstract

PURPOSE:To improve the accuracy for inferring the present position by usually inferring the present position from an earth magnetism detecting means and a running distance detecting means, and checking up whether magnetization exists or not and correcting an output value of the earth magnetism detecting means, when an abnormal ferromagnetic field has been detected. CONSTITUTION:Usually an azimuth in the advance direction is derived from an output value of an earth magnetism detecting means 11 at every prescribed time, a running distance is derived from an output of a running distance detecting means 10, and from these values, the present position is detected by a dead reckoning arithmetic means 13. When a vehicle passes through in a ferromagnetic field in a grade crossing, etc. in the course of running, and the direction and strength of an abnormal ferromagnetic field is measured from an output of the earth magnetism detecting means 11, an output variation quantity and a variation direction of the earth magnetism detecting means 11 are derived in a magnetization correction quantity arithmetic means 15, and the output of the earth magnetism detecting means 11 is corrected by using its output variation quantity and variation direction in an azimuth arithmetic means 12. In such a way, a new present position is inferred in the dead reckoning arithmetic means 13.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vehicle position detection device that accurately estimates the current location of a vehicle, etc. in order to display the current location along with a map or notify the vehicle by voice.

Conventional technology FIG. 4 shows a conventional vehicle position detection device.

The structure of this conventional example will be explained below with reference to FIG. 4.

In the figure, numeral 41 is a distance detecting means, 42 is an azimuth detecting means using a geomagnetic sensor, 43 is a map memory storing map data and the geomagnetic direction on a predetermined straight road, and 4
4 is a control means, and 45 is a display means.

Next, the operation of the vehicle position detection device will be explained.

The direction of geomagnetism on a predetermined straight road is stored in the map memory 43, and the control means 44 compares the direction of geomagnetism based on the data from the direction detection means 42 with the direction of geomagnetism on the stored straight road. When the difference reaches a predetermined value, the output of the azimuth detection means is corrected based on the geomagnetic direction data in the map memory, and the output of the azimuth detection means is corrected based on the data from the mileage detection means in 41 above and the error-corrected data from the azimuth detection means. Calculate the current position of. The current position calculated in this way is displayed on a display together with a map (Japanese Patent Laid-Open No. 610-89300).

Problems to be Solved by the Invention As mentioned above, in the conventional vehicle position detection device, the direction of travel is corrected by storing geomagnetic data for each straight road in the map memory in advance, and calculating the difference between this data and the data from the direction detection means. Since this method is carried out using a geomagnetic field, it may not be possible to correct for changes in the environment due to the increase or decrease of buildings, etc., and it has been difficult to implement because the geomagnetic field is measured over a wide area.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vehicle position detection device that can improve the accuracy of current position estimation.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a traveling distance detecting means for detecting the traveling distance of a vehicle, a geomagnetism detecting means for detecting the traveling direction of the vehicle and the strength of the magnetic field, and the above-mentioned. an abnormal value determining means for determining an abnormal magnetic field from an output value of the geomagnetism detecting means and determining the change direction and strength of the abnormal magnetic field; and an abnormal magnetic field detection signal of the abnormal value determining means and data on the changing direction and strength of the abnormal magnetic field. magnetization correction amount calculation means for calculating the amount of change in the output value of the geomagnetism detection means due to the magnetization of the vehicle body and correcting the traveling direction calculation; azimuth calculating means for determining the traveling direction of the vehicle from the output value of the vehicle; and based on the traveling distance obtained from the previous estimated position by the traveling distance detecting means and the azimuth of the traveling direction of the vehicle obtained from the azimuth calculating means. It consists of a dead reckoning calculation means for estimating the new current position.

According to the above configuration, the present invention usually estimates the current position from the vehicle-mounted geomagnetism detection means and the mileage detection means, checks whether it is magnetized when an abnormally strong magnetic field is detected, and if it is magnetized, the geomagnetism detection means Since the output value of is corrected, the vehicle position can be detected with high accuracy.

Example The configuration of one embodiment of the present invention will be described below.

In FIG. 1, numeral 10 is a distance detecting means, and 11 is a distance detecting means.
is a geomagnetic detection means. Reference numeral 12 denotes an azimuth calculating means for determining the traveling direction from the vehicle traveling direction data of the geomagnetism detecting means and the amount of change in the output value of the geomagnetic detecting means. 13 is a dead reckoning calculation means for estimating the current position from the outputs of the travel distance detection means and the azimuth calculation means. Reference numeral 14 indicates abnormal value determining means for determining an abnormality in the output value of the geomagnetic field detecting means and determining the changing direction and strength of the abnormal magnetic field. 15 represents an abnormal magnetic field detection signal from the abnormal value determining means and the changing direction and strength of the abnormal magnetic field. The magnetization correction amount calculating means calculates the amount of change in the output value of the earth's magnetic field detecting means due to the magnetization of the vehicle body from the data of the vehicle body, and corrects the heading calculation by the heading calculating means.

Reference numeral 16 denotes a terminal for outputting the estimated position data obtained by the dead reckoning calculation means 13.

Next, the operation of the above configuration will be explained.

At regular intervals, the azimuth of the traveling direction is determined from the output value of the geomagnetism detection means 11, the travel distance is determined from the output of the travel distance detection means 10, and the current position is detected from these values by the dead reckoning calculation means 13. . Now, the previous detection position is (X
O, YO). Assuming that the traveling direction of the vehicle body becomes θ during a certain time T and the traveling distance calculated from the output value of the traveling distance detecting means 10 is A, the detected position is determined as follows.

X: AXCOSθ+XO Y”AXslnθ+YO With the above X and Y as new detection positions, respectively X09
YO, the above calculation is repeated every time T to update the detected position.

However, in reality, the vehicle body is magnetized by a strong magnetic field at a railroad crossing or the like, and the output value from the earth's magnetic field detection means 11 changes, so the detected position determined by the above method deviates from the actual position. Therefore, in the present invention, the abnormal value determining means 14 measures the direction and strength of the abnormal strong magnetic field from the output of the earth's magnetic field detecting means 11, and the magnetization correction amount calculating means 15 measures the change m in the output of the earth's magnetic field detecting means 11 and the direction of change. The current position is determined with high precision by calculating the output of the geomagnetism detecting means 11 using the amount and direction of change in the output in the azimuth calculating means 12, and estimating the new current position in the dead reckoning calculating means 13. I can guess.

Vehicle position correction using the above method will be explained using FIGS. 2 and 3.

Figure 2 shows the output values Vxs Vy of two mutually orthogonal components of the geomagnetism detection means attached to an unmagnetized car.
The trajectory generally represents the horizontal component of the geomagnetic field. 20 is a trajectory when the vehicle body is turned in the absence of an abnormal magnetic field. 21 is the trajectory drawn by the output value Vx+Vy when the geomagnetism detection means detects an abnormal magnetic field caused by a moving object such as a truck, and 22 is the trajectory of the output value Vx+Vy when the geomagnetism detection means detects an abnormally strong magnetic field caused by a railroad crossing. It is a trajectory to be drawn.

The circle 23 is a predetermined threshold value with the strength of the magnetic field constant. In general, abnormal magnetic fields caused by fixed objects such as railroad crossings are stronger than abnormal magnetic fields caused by moving objects such as trucks, and can be distinguished by the amount of change in magnetic field strength. They can also be distinguished by the strength of the magnetic field, including Note that even if the vehicle body is magnetized, the coordinates of V If it is translated in parallel, it can be handled in the same way as when it is not magnetized.

In FIG. 3, in step 301, the vehicle is turned in advance to obtain the equation of the circle drawn by the output value VxtV'l of the geomagnetism detection means. Here, alb is the center of the circle, and R is the radius of the circle. In step 302, the output values from the travel distance detection means and the geomagnetism detection means are input, and in step 303, the input values and correction values Cx and CY of the output of the geomagnetism detection means are used to determine the azimuth θ of the travel direction and the travel distance. A is found, and the current position is detected as follows using the previously detected current position X01YO.

X: AXOO5θ+XO Y: AXslnθ+YO With the above X and Y as new estimated positions, xo respectively
, yo. In step 304, the cumulative moving distance is calculated from the moving distance A. In step 305, it is compared whether the cumulative moving distance is greater than a predetermined moving distance LO, and if L≧LO, then in step 306, the output values Vx and VY from the geomagnetism detection means are stored in a table in order. This table stores the output values of the geomagnetism detection means from a point returned by a predetermined distance C to the current position, and the output data of the geomagnetism detection means before that point is sequentially deleted. In step 307, the traveling distance d from the time when abnormal magnetic field detection was previously determined is determined, and L=O
In step 308, if the distance d is larger than the predetermined distance C, in step 309, the maximum value Vxma xlV ym a
1 Find Vymin. In step 310, the above data is used to determine the variation width M of the magnetic field strength as follows.

M= ((Vxmax-Vxmin) 2+ (Vy
max-VYmin)91'' In step 311, it is checked whether the change width is larger than a predetermined threshold value Mth.

If the geomagnetic variation width M is smaller than the predetermined threshold Mth, it is determined that no abnormal magnetic field has been detected, and step 31
In step 5, d is set to O and the process returns to step 302. 'If the geomagnetic variation width M is larger than the predetermined threshold Mth, it is determined that an abnormal magnetic field has been detected, and in step 312, the maximum value and minimum value of VX, whichever is closer to the above a, is set to Vxfs a (
The one without is designated as Vxl. Similarly, if the maximum value and minimum value of Vy, which is closer to the above value, is Vyf, and the one which is not closer to b is Vyl, the direction of change Φ of the abnormal magnetic field in the Vx-'Vy plane can be determined as follows.

Φ= j a n-1 ((Vy 1-V3' f )/
(Vxl-Vxf)) (When (Vxl-Vxf)≧0.) Φ=π+jan-1((Vyl-Vyf)/(Vxl-
Vxf)) ((Vx l - Vx f ) <O) In step 313, the circle equation in step 301 is compared with the current output value of the geomagnetism detection means, and from the current output value, R1 = ((Vx -a) 2+ (Vy-b)
01 no 2 is calculated, and if this R1 satisfies (R-dR)<R1<(R+dR) dR: threshold value, it is determined that magnetization is not performed, and in step 315, the above-mentioned d is set to O and step Return to 301. If not satisfied, it is assumed that magnetization is achieved and a correction amount is determined in step 314.

In magnetization, the movement amount CM of the center of the circle drawn by the output value of the geomagnetism detection means with respect to the geomagnetic variation width M has the following relationship.

CM F AXM + B A, B are constants that differ depending on the vehicle model and are measured through experiments. Also, the direction of movement is the direction of change of the abnormally strong magnetic field Φ
This is approximately 180° opposite direction.

Therefore, in step 314, the center of the circle drawn by the output value of the geomagnetism detecting means moves f according to the geomagnetic variation width M.
ficM is determined, and the correction ffk CX1CY is determined from the change direction Φ of the abnormal magnetic field as follows.

Cx=CMXcos(Φ+π) Cy=CMXsln(Φ+π) Then, in step 315, the first half d is set to O, and step 30
Return to 2.

In the above embodiment, the determination of whether or not it is an abnormal magnetic field is made from the amount of change in the strength of the magnetic field, but the absolute value of the strength of the magnetic field (Vx2+VY2) 1/2 is calculated and the predetermined threshold value shown in FIG. If it is larger than circle 23, it may be determined that there is an abnormal magnetic field. Further, characteristics of the magnetic field change such as the direction of the magnetic field change may be used to determine the abnormal magnetic field.

Effects of the Invention As described above, according to the present invention, even if the car's body is magnetized by driving in a strong magnetic field such as at a railroad crossing, the current position can be accurately determined by automatically correcting the output data of the geomagnetism detection means. Can be detected well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a vehicle position detection device in an embodiment of the present invention, FIG. 2 is a locus diagram of the output of the geomagnetism detection means,
FIG. 3 is a flowchart showing the arithmetic processing of the means of the device, and FIG. 4 is a block diagram of a conventional vehicle position detection device. 10... Travel distance detection means, 11... Geomagnetism detection means, 12... Direction calculation means, 13... Dead reckoning calculation means, 14... Abnormal value judgment means, 15.・
... Magnetization correction amount calculation means.

Claims (3)

[Claims] (1) Mileage detection means for detecting the mileage of the vehicle;
geomagnetism detection means for detecting the traveling direction of the vehicle and the strength of the magnetic field; an abnormal value determination means for determining an abnormal magnetic field from the output value of the geomagnetism detection means and determining the change direction and strength of the abnormal magnetic field; and the abnormal value. Magnetization correction amount calculation means for calculating the amount of change in the output value of the geomagnetism detection means due to magnetization of the vehicle body from the abnormal magnetic field detection signal of the determination means, data on the change direction of the abnormal magnetic field, and data on the strength of the abnormal magnetic field, and correcting the heading calculation. , azimuth calculating means for determining the traveling direction of the vehicle from the traveling direction of the vehicle by the geomagnetism detecting means and the output value from the magnetization correction amount calculating means; and a traveling distance obtained from the previously estimated position by the traveling distance detecting means. and dead reckoning calculation means for calculating a new current position based on the azimuth in the direction of travel of the vehicle obtained by the azimuth calculation means. (2) In the abnormal value determination means, the strength of the magnetic field is determined from the output sample of the geomagnetism detection means, and if the strength of the magnetic field is greater than or equal to a predetermined value, it is determined that it is an abnormal magnetic field, and the output value of the geomagnetism detection means changes. 3. The vehicle position detection device according to claim 2, wherein a direction vector is determined. (3) In the magnetization correction amount calculation means, after receiving the abnormal magnetic field detection signal from the abnormal value determination means, the magnitude of the abnormal magnetic field measured in advance and the amount of change in the output value of the geomagnetism detection means due to the magnetization of the vehicle body are calculated. 2. The vehicle position detection device according to claim 1, wherein the correction amount is determined from a relationship.