JPH03291514A - Stable value extracting method for earth magnetism azimuth sensor - Google Patents

Abstract

PURPOSE:To reduce an error due to coordinate variance by performing a dividing and an evaluating process using the ratios of the mean coordinate points of several past X and Y coordinate points about an optional set value of the azimuth circle radius of the earth magnetism sensor and individual coordinate points used for the averaging. CONSTITUTION:Output data on an absolute azimuth which is detected by the earth magnetism azimuth sensor 1 and base upon the earth magnetism, output data on the azimuth change of a vehicle from the difference between the right and left wheel speeds of the vehicle which is detected by a wheel speed sensor 2, and output data on the moving distance of the vehicle which is detected by a travel distance sensor 3 are inputted to an arithmetic part 5 through a sensor interface 4. The arithmetic part 5 calculates the running mean coordinate point of several past coordinate points on X and Y coordinates based upon the X and Y component output values of the sensor 1 including the current point. Then the ratio of the values for the mean coordinate point of the past coordinate points used for the running averaging and the optional set value of the azimuth circle radius on the X and Y coordinates is evaluated as the coordinate variance, the data detected by the sensor 1 is given a grade of detection accuracy, and the result is display at a display part 6.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for extracting stable values of a geomagnetic azimuth sensor, in which a geomagnetic azimuth sensor and a wheel speed sensor are mounted on a vehicle, and stable data is extracted by removing irregular data due to the influence of magnetic disturbance.

[Conventional technology]

FIGS. 8 and 9 are block diagrams of a device showing a conventional magnetization correction method for a geomagnetic azimuth sensor disclosed in, for example, Japanese Unexamined Patent Publication No. 63-128222, and an explanation of the principle of output change of the geomagnetic azimuth sensor when the azimuth changes. In the figure, 71
72 is a geomagnetic azimuth sensor, 72 is a vehicle azimuth change detecting means, such as a wheel speed sensor, and 73 is a calculation means. Moreover, FIG. 9 shows the geomagnetic direction sensor 71 when the direction changes.
It is an explanatory diagram of output change. First, when the vehicle changes by A, the direction sensor output also changes from A to B. In this case, assuming that the radius of the azimuth circle of the geomagnetic azimuth sensor 71 does not change before and after the azimuth change, as is clear from FIG. 9, the center of the azimuth circle, 0, is 2 with the line segment It is an equilateral triangle, and the vertex of the triangle has an apex angle of θ. In other words, if the amount of change θ in the vehicle's azimuth, the rotation direction, the output A of the geomagnetic azimuth sensor 71 before the azimuth of the vehicle changes, and the output B of the geomagnetic azimuth sensor 71 after the azimuth has changed, the center of the azimuth, that is, the amount of magnetization can be found. FIG. 6 is an explanatory diagram of output changes and calculations of a magnetic orientation sensor 71. FIG. New magnetization occurs while the vehicle is moving, and the amount of magnetization becomes ΔX-
Suppose that it changes to ΔXI+Δy−Δyl. Furthermore, the relatively stable output of the geomagnetic direction sensor 71 before curving is expressed as AP(XI + 'jI), and the output of the relatively stable geomagnetic direction sensor 71 after curving is expressed as BP(XZ
, 7z). First, the output AP (x+ , )'+ ) of the geomagnetic direction sensor 71 before the vehicle changes direction.
is stored in the calculation means 73. Next, when the vehicle changes direction, the wheel speed sensors 7 for the left and right wheels
2 etc., the amount of change in orientation θ is determined. Figure (C) shows the vehicle before the azimuth change, and Figure (D) shows the change angle θ after the azimuth has changed due to the counterclockwise rotation of the vehicle. It is assumed that θ determined by the left and right wheel speed sensors and θ are the same angle. After direction change, direction sensor output BP (XZ +yz)
is found. These APIs (XI +y+) + Bp(Xz
1y2) From θ3, assuming that the radius for the direction before and after the direction change is constant, in the figure (a), s < s x, s y) = (X + ”
, V + "V Z )2 Length between Ap and B, L-(x+ xz)" ± (y+ 3'z)
” and here, the direction of vectors A, , B is θ.+l
If F, then ``All+1F=tan-'['=2'' huge] (X, -X. π×θAll!IF<π) If the direction of vector S02 is θSOP, then θSOP
”'θA P I P + 2 Center of magnetization 0.(Δ
X1+Δy+) is (ΔXl+Δy1)=(SX+fcosθ5OPI S y + 42 sx
nθ,. , ).

[Problem to be solved by the invention]

The conventional magnetization correction method for a geomagnetic azimuth sensor is executed as described above, and therefore, among the magnetic information detected using the geomagnetic azimuth sensor, magnetic information including disturbance magnetism other than geomagnetism is averaged. The idea is that it is effective against isolated magnetic disturbances in places where the geomagnetic environment is stable, but it is important to suppress detection errors when the geomagnetism itself is distorted, such as on an elevated road, and the absolute orientation is biased. The problem was that it was not possible. In addition, the idea that the radius of the azimuth circle used for magnetization correction of the geomagnetic azimuth sensor is constant before and after the azimuth change is based on the idea that the radius of the azimuth circle used for magnetization correction of the geomagnetic azimuth sensor is the same before and after the azimuth change. When the environment is stable, the radius of the azimuth circle is stably obtained as the radius changes, so even if it is possible to detect a change in the vehicle body magnetization state and prevent erroneous correction, When the earth's magnetic field itself is distorted, such as on an elevated road, the vehicle body magnetization state cannot be changed and there is a risk of incorrect correction being performed. This invention was made to solve the above-mentioned problems, and includes a geomagnetic azimuth sensor's X and Y component output values, a detected absolute azimuth, and a wheel speed sensor that detects the azimuth of a moving body using methods other than geomagnetism. , based on several past data including the current value of each azimuth change angle of the second azimuth sensor, a comprehensive evaluation is performed with the dispersion of each data as an evaluation target, and the detection accuracy is determined based on the data of the geomagnetic azimuth sensor. The purpose of the present invention is to obtain a stable value extraction method for a geomagnetic azimuth sensor that removes heretical data by assigning ranks (grades).

[Means to solve the problem]

The stable value extraction method of the geomagnetic direction sensor according to the present invention is as follows:
X, the first orientation sensor that uses geomagnetism. Coordinates, direction,
The arithmetic unit performs a comprehensive evaluation of each variation between J and J, and assigns a grade of detection accuracy to the data of the first direction sensor. The ratio between the average coordinate point obtained by moving the moving average of several X and Y coordinate points, the size between the coordinate points of the individual coordinate points used for the average, and the arbitrary setting value of the radius of the azimuth circle of the first azimuth sensor The azimuth variation is calculated as the moving average of the azimuth change angle of the past several absolute azimuths including the current value and the absolute value of the azimuth change angle detected by the second azimuth sensor. The difference is evaluated based on the magnitude of the difference, and the radius variation is evaluated as the ratio between the arbitrary set value and the current value of the radius of the azimuth circle of the first azimuth sensor.

[Effect]

The stable value extraction method of the geomagnetic azimuth sensor in this invention includes evaluating the ratio of the current value to an arbitrary setting value of the azimuth circle radius of the first azimuth sensor, and also evaluating the ratio of the current value to an arbitrary setting value of the azimuth circle radius of the first azimuth sensor. The past number of X, Y including the value
Evaluation of the ratio of the size of the moving average of the X and Y coordinate points to the component output value, the change angle of the absolute azimuth for several past values including the current value, and the method for detecting the azimuth using methods other than geomagnetism. The heretical data that cannot be removed by individual evaluation is removed based on the evaluation standard value of the difference between the two average values obtained by moving the average of the absolute values of the azimuth change angles of the azimuth sensors of 2. To be able to extract stable data by removing everything without omission.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a mobile navigation device according to an embodiment of the present invention.
The geomagnetic azimuth sensor 2 is a first azimuth sensor that detects an absolute azimuth based on geomagnetism, and the wheel speed sensor is a second azimuth sensor that detects changes in the vehicle's azimuth based on differences in vehicle left and right wheel speeds. 3 is a mileage sensor that detects the travel distance of a vehicle as a moving body, and each of the sensors I to
3 is input to the sensor interface 4. 5 extracts stable values of geomagnetic sensor data based on the output data from each sensor 1 to 3 sent sequentially, and the distance traveled by the vehicle;
A calculation unit calculates the heading direction and the position of the own army, and 6 is a display unit that draws the position of the own vehicle. Next, coordinate variations, azimuth variations, radius variations, etc. were considered as evaluation targets for extracting stable values of the output data of the geomagnetic azimuth sensor l, and respective evaluation methods will be described below. First, coordinate variations are determined as shown in Figure 2 (I), which determines magnetic disturbances including disturbance magnetism other than geomagnetism. , the ratio ΔL of the size ΔL between the average coordinate point obtained by moving the moving average of several past XY coordinate points including the current value and the individual coordinate points used for the average, /R
By classifying them by At, they are evaluated in three stages: large, medium, and small. Direction variation is used to determine direction disturbance as shown in Figure 2 (c), and is based on the direction change angle of the past several absolute directions θ, including the current value, and the direction detected from the second direction sensor. The change angle ψ1 is evaluated in three stages, large, medium, and small, by classifying the inverse magnitude of both average values obtained by moving averages of the respective absolute values of the change angle ψ1. Here, the reason why the determination is made based on the magnitude of the difference between both average values is to remove the azimuth disturbance caused by the zigzag running of the vehicle. In addition, the radius variation is used to determine the magnitude of disturbance magnetism other than geomagnetism, and is divided into three levels (large, medium, and small) based on the ratio of the current value to the self-learned value of the radius of the azimuth circle of the geomagnetic azimuth sensor 1. Evaluate. An example of the evaluation standard values used in evaluating these variations is shown in Part 3.
As shown in the figure. In FIG. 3, a is the evaluation reference value for the coordinate variation, b is the azimuth variation, and C is the evaluation reference value for the radius variation. Figure 4 is a diagram showing isoline divisions for stable value extraction, and is graded in five stages from 1 to 5, with 1 being the most stable, based on the evaluation results of the coordinate variations and orientation variations obtained in Figure 3. I am attaching it. Next, the operation will be explained using the flowcharts of FIGS. 5 and 6. First, in step 5T41 in FIG. 5, initial processing of the device, initial display, and rotation correction of the geomagnetic azimuth sensor 1 are executed. Also, here, the self-learning value of the azimuth circle radius of the geomagnetic azimuth sensor 1 is initialized, step 5T42.
The system then waits until the vehicle has traveled a certain distance. In step ST43, output data from the geomagnetic azimuth sensor 1 and wheel speed sensor 2 is input to the calculation unit 5 via the sensor interface 4. In step 5T44, the absolute heading and the change in the heading of the vehicle are calculated. Step ST45 evaluates variations in coordinates and orientation and ranks detection accuracy for extracting stable values of geomagnetic orientation sensor data, Step 5T
At step 46, the traveling direction of the vehicle is calculated using equation (1). (
In equation 1), θ and θ1-1 are the current and previous values of the vehicle's heading, JK is the absolute heading, ψ is the change in the vehicle's heading, and k is the value that changes depending on the grade.The weighting of the absolute heading is a coefficient. Each is shown below. θ1=θ=−1+cJK−θ1−1)×+ψX(1−k) (1) In step ST47, the magnetization of the geomagnetic direction sensor 1 is corrected. In step 5T48, each data is stored in the memory and the vehicle position is updated. In FIG. 6, in step ST51, the turning angle and turning distance of the vehicle are updated, and in step 5T52, it is determined whether the detection accuracy class is class 1 (moving straight with small magnetic disturbance), and if it is not class 1, If it is class 1, it exits the magnetization correction process and executes step 5T53. In step 5T53, it is determined whether the settings of the X and Y component output values before the azimuth change and the turning angle and turning distance of the vehicle are valid, and whether the X and Y component output values before the azimuth change are not set or the turning angle is 60°
If the turning distance is less than 120° or more than 200 m, execute step ST54; otherwise, execute step S.
Execute T55. Here, the reason why the turning angle and turning distance are included in the processing conditions is to remove data before and after changes in the magnetic environment and to enable correction based on left and right turning movements of the vehicle. In step 5T54, the X before the direction change
. The Y component output value is set and the turning angle and turning distance of the vehicle are cleared to zero, and then the process exits from the magnetization correction process. In step ST55, the variation in the radius of the azimuth circle of the geomagnetic azimuth sensor 1 is evaluated (determining the magnitude of disturbance magnetism other than geomagnetism). In step ST56, if the evaluation result in step 5T55 is large, the magnetization correction process is skipped, Otherwise, step ST57 is executed. In step 5T57, the self-learning value of the azimuth circle radius of the geomagnetic azimuth sensor 1 is updated. In step ST58, if the evaluation result in step 5T55 is within the range, the magnetization correction process is exited, otherwise step 5T59 is executed. In step 5T59, the amount of magnetization is calculated and corrected based on equations (2) and (3) based on the relationship between the X and Y component output values before and after the azimuth change and the turning angle of the vehicle shown in FIG. In equations (2) and (3), X, Y, and Xz, Yz are the X and Y component output values before and after the azimuth change, ψ is the vehicle turning angle, X eo + YCO and XO
, Y (1 is the X and Y component output value of the fixed center which is determined by the circuit as the estimated center of the azimuth circle of the geomagnetic azimuth sensor l, δX,
δY is the amount of magnetization X. This is the Y component output value. δX=Xc, -X. δY = Yc, -Y. In addition, in the above embodiment, coordinate variations, azimuth variations,
Although the individual evaluation methods, usage, and grading of radial variation and radial variation have been described, grading by other evaluation methods may also be used and the same effects as in the above embodiments can be achieved. Further, in the magnetization correction of the geomagnetic sensor according to this embodiment, the X and Y component output values before and after the azimuth change are used as raw coordinate points, but the average coordinate point of the averaged X and Y component output values may be used.

【Effect of the invention】

As described above, according to the present invention, the first
The X and Y component output values of the direction sensor. Coordinates and orientation based on several past data including the detected absolute orientation and the current value of the orientation change angle of the second orientation sensor that detects the vehicle orientation using methods other than geomagnetism. The calculation unit comprehensively evaluates each variation in the radius data and assigns a detection accuracy grade to the data of the first orientation sensor. This has the effect of being able to remove heretical data from the viewpoint of the size of the azimuth and the size of the azimuth disturbance. Furthermore, by evaluating any combination of the above three variations, it is possible to remove irregular data that cannot be removed by evaluating a single variation, and it is possible to accurately perform processes such as the vehicle heading direction and the magnetization correction of the first direction sensor. It has the effect of making you able to do it. In addition, since the data of the first direction sensor is graded in terms of detection accuracy, it is easy to use (or weight) the data of the geomagnetic direction sensor according to the grade, and it is possible to process the data of the first direction sensor. This has the effect of making management easier and more reliable.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a vehicle position detection device according to an embodiment of the present invention, Figs. 2 (a) to (c) are illustrations for explaining evaluation of a variation target, and Fig. 3 is used for variation evaluation as an example. An explanatory diagram of evaluation reference values, Fig. 4 is an explanatory diagram of equal margining for stable value extraction, Figs. 5 and 6 are flowcharts showing the operation of the present invention, and Fig. 7 is the X and Y component output before and after the direction change. An explanatory diagram of values and vehicle turning angles, Figure 8 is a configuration diagram of magnetization correction in a conventional vehicle detection device, Figure 9 is an explanatory diagram of output changes of the geomagnetic azimuth sensor when the direction changes, and Figure 1O (a) is a diagram of the geomagnetic field. Figure (II) is an explanatory diagram of the rotation angle of the vehicle determined by the left and right wheel speed sensors, and (C) and (D) are diagrams explanatory of the change in the orientation of the vehicle. In the figure, 1 is a geomagnetic azimuth sensor (first azimuth sensor), 2 is a wheel speed sensor (second azimuth sensor), 3 is a travel distance sensor, and 5 is a calculation unit. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] Past information including the X and Y component output values of the first azimuth sensor that uses geomagnetism, the detected absolute azimuth, and the current value of the azimuth change angle of the second azimuth sensor that detects the azimuth of the vehicle using a method other than the geomagnetism. Based on the individual data, the arithmetic unit performs a comprehensive evaluation using the dispersion of each data of coordinates, direction, and radius as an evaluation target, and assigns a detection accuracy grade to the data of the first direction sensor. The coordinate variation is the average coordinate point obtained by moving the moving average of several past X and Y coordinate points including the current value, the size between the individual coordinate points used for the average, and the radius of the azimuth circle of the first azimuth sensor. The azimuth variation is calculated as the ratio of the azimuth change angle of the past several absolute azimuths including the current value and the respective absolute values of the azimuth change angle detected by the second azimuth sensor. The radial variation is evaluated as the ratio between the arbitrary set value and the current value of the radius of the azimuth circle of the first azimuth sensor. Stable value extraction method for direction sensor.