JPS59228111A - Correction method for in-vehicle geomagnetic sensor - Google Patents

Abstract

PURPOSE:To display a correct azimuth simply, by adding a component, which is extended into the direction of east and west to a geomagnetism vector that is obtained by a geomagnetism sensor, and performing correction. CONSTITUTION:For example, a vehicle is running in the direction of noth east. In the area, where geomagnetism is normal, the geomagnetism is detected as a vector of OQ. In the area where the geomagnetism is abnormal, however, the geomagnetism vector is detected in the state of OP. Then, the vector OP is further extended, and an intersection R with a normal vector locus 1 is obtained. A vector OR is obtained. A difference PR between the OR and the OP is obtained. The PR is turned with the point P as the center so as to face the direction of east. A resultant vector OR' of the OP and the PR' is obtained. The OR' is used as the final geomagnetism vector after the correction.

Description

[Detailed description of the invention] The present invention relates to a correction method for a vehicle-mounted geomagnetic sensor.

An on-vehicle geomagnetic sensor is installed in a vehicle such as a car and has the function of detecting geomagnetism, and can generally measure the direction in which the vehicle is traveling and notify the driver of this information as information related to the driving situation to facilitate driving. Used as a sensor such as a compass. For example, a toroidal core type fluxgate type geomagnetic sensor is used as this geomagnetic sensor.

By the way, conventionally, if you drive a vehicle equipped with the above-mentioned direction indicator around the city, you can know which direction the vehicle is currently traveling in, but if you drive on the Kubuki Expressway, etc. has the characteristic that the geomagnetic detection function of the geomagnetic sensor is greatly disturbed. When we investigated the cause of this discrepancy, we discovered that it was a geomagnetic anomaly area where the magnitude of the geomagnetic field in the east-west direction was shortened. In other words, as shown in Figure 1, the geomagnetic vector is originally drawn in all directions (the trajectory should be 1, but
A similar vector trajectory on the Kubu Expressway looks like 2. Due to this reason, for example, when a vehicle turns northwest, in a geomagnetic anomaly area, there is a difference between the actual heading and the heading displayed by the compass. In this case, an error of angle 0 will occur.

In view of the above-mentioned problems, the present inventors have attempted to effectively solve the problems (the present invention has been accomplished).

An object of the present invention is to correct the on-vehicle geomagnetic sensor so that an error will not occur in the direction display of the direction meter even if a vehicle equipped with a direction indicator etc. having a geomagnetic sensor travels in a geomagnetically abnormal area such as the Kubuki Expressway. The purpose is to provide a method.

The feature of the present invention is that, taking into account that the cause of the abnormality in the geomagnetic anomaly area is compression of the geomagnetic field in the east-west direction, the geomagnetic vector obtained by the geomagnetic sensor is corrected by adding a component extending in the east-west direction. It's what I chose to do.

An embodiment of the present invention will be described in detail below based on the accompanying drawings.

FIG. 2 is a diagram for explaining the principle of correction according to the present invention. In FIG. 2, the vertical axis means the north-south direction, and the horizontal axis means the east-west direction. In addition, a toroidal core type fluxgate type geomagnetic sensor has windings for X output and Y output, respectively, located spatially orthogonal to each other around the core. is obtained.

The geomagnetic vector detected by the geomagnetic sensor can be obtained by combining the X output and Y output. Therefore, in FIG. 2, the horizontal axis represents the X output, and the vertical axis represents the Y output.

In FIG. 2, reference numeral 1 indicates a trajectory drawn by geomagnetic vectors in all normal directions when a vehicle equipped with a compass having a geomagnetic sensor runs on a general road. On the other hand, 2 is a trajectory drawn by a geomagnetic vector compressed in the east-west direction, which occurs when a vehicle similar to the one described above travels in a geomagnetically abnormal area such as the Kubi Expressway.

Before explaining the correction principle, we will briefly explain the configuration of the in-vehicle direction meter in the third section.
This will be explained based on the diagram. As mentioned above, the toroidal core type fluxgate type geomagnetic sensor 3 has an X output winding, a Y
It has output windings, and the output of each winding is amplified by a sensor amplifier 4 and then input to a computer 5, where A
-D conversion and vector synthesis to obtain the geomagnetic vector.

The direction indicator 6 of the compass is operated based on the geomagnetic vector obtained in this manner, and the direction in which the vehicle is currently traveling is displayed on the direction indicator 6.

Next, the principle of correction according to the present invention will be described. In FIG. 2, if the vehicle is now traveling northeast, in areas where the geomagnetism is normal, the geomagnetism will be detected by the OQ vector. However, in geomagnetic anomaly areas, the geomagnetic field is compressed in the east-west direction, so the geomagnetic sensor detects geomagnetic vectors in the OP state, where the vector length is short. Therefore, an angular error ZPOQ occurs between the normal geomagnetic vector OQ and the geomagnetic vector OP in the abnormal area.

Therefore, OI) is further extended to find the intersection R with the normal vector locus 1, and OR is found. After that, the difference PR between OR and OP is determined, and this I) R is rotated around point P so as to face east, and the vector sum OR' of OP and PR' is determined. This OR' is then used as the final geomagnetic vector after correction. Even in this correction, the error in ZR'OQ remains uncorrected, but it can be approximated to a normal geomagnetic vector OQ to the extent that there is no practical problem.

The above correction is prepared as an algorithm in the computer 5 and is performed by the computer 5. It goes without saying that the computer 5 can improve the accuracy of calculation in order to further reduce tear 1 ('oQ).

As is clear from the above description, according to the present invention, even when driving in a geomagnetically abnormal area such as the Kubuki Expressway, the vehicle-mounted azimuth meter can be corrected using a simple method and always display the correct azimuth. In particular, since it is sufficient to prepare a predetermined algorithm in the signal processing computer, it can be realized at low cost.

[Brief explanation of the drawings] Figure 1 is a diagram for explaining the problem of the in-vehicle geomagnetic sensor.
FIG. 2 is a diagram for explaining the principle of the correction method according to the present invention, and FIG. 3 is a block diagram showing the configuration of a vehicle-mounted compass. In the drawing, 1 is a locus of a normal geomagnetic vector, 2 is a locus of an abnormal geomagnetic vector, 3 is a geomagnetic sensor, and 5 is a computer.

Claims (1)

[Claims] In-vehicle direction meters, etc. that detect the geomagnetic field with a geomagnetic sensor and measure the direction and magnitude of the geomagnetic field with a computer to display the vehicle's heading.When the geomagnetic vector length is short, the difference in magnitude from the normal geomagnetic vector is detected. A method for correcting an in-vehicle geomagnetic sensor, characterized in that a composite vector determined by determining the difference between the vectors and extending the difference in the east-west direction is used as a geomagnetic vector in subsequent processing.