JPS63158408A - Processing method of data of geomagnetism sensor - Google Patents

Abstract

PURPOSE:To detect the azimuth of a vehicle more accurately and thereby to conduct navigation with excellent accuracy, by increasing the reliability of azimuth data which are determined by a geomagnetism sensor. CONSTITUTION:A system controller 5 comprises an interface 6 which receives as inputs the outputs of a geomagnetism sensor 1 for outputting the azimuth data of a vehicle on the basis of geomagnetism, an angular speed sensor 2 of the vehicle, a running distance sensor 3 and a sensor 4 for detecting the present place of the vehicle and conducts A/D conversion and others, CPU 7 computing the amount of movement of the vehicle, ROM 8 and RAM 9, a recording medium 10 wherein map informations are recorded, a graphic memory 11 and a display 12. CPU 7 sets the tolerance limits of variation in output data of the geomagnetism sensor 1 and conducts correction of the output data of the geomagnetism sensor 1 on the basis of prescribed data when the output data of the geomagnetism sensor 1 are not within these tolerance limits continuously for a prescribed time. Thereby the azimuth of the vehicle is detected more accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data processing method for a geomagnetic sensor in an on-vehicle navigation device.

In recent years, in-vehicle navigation devices have been developed that guide a vehicle to a predetermined destination by storing map information in a memory, reading the map information from the memory, and displaying the map information along with the vehicle's current location on a display device. being researched and developed.

Such a navigation device requires a direction sensor that detects the direction of the vehicle, and as this direction sensor, for example, a geomagnetic sensor that detects the direction of the vehicle based on geomagnetism (earth's magnetic field) is used. However, this geomagnetic sensor is easily affected by disturbance magnetic fields, and its output may be affected when a vehicle passes a railroad crossing, a railway bridge, or when a large vehicle (such as a truck or bus) passes by the vehicle. The data will contain large errors.

1. The present invention has been made in view of the above-mentioned points, and by increasing the reliability of the direction data obtained by the geomagnetic sensor, the direction of the vehicle can be detected more accurately and navigation with good precision can be performed. The purpose of this study is to provide a data processing method for a geomagnetic sensor that allows

The geomagnetic sensor data processing method according to the present invention sets a tolerance range that allows variations in the output data of the geomagnetic sensor, and when the output data of the geomagnetic sensor does not fall within the tolerance range for a predetermined period of time, a predetermined The feature is that the output data of the geomagnetic sensor is corrected based on the data.

Friend-Jul! Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the configuration of a vehicle-mounted navigation device to which a geomagnetic sensor data processing method according to the present invention is applied. In the figure, 1 is a geomagnetic sensor for outputting vehicle orientation data based on geomagnetism, 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, 3 is a mileage sensor for detecting the distance traveled by the vehicle, 4 is a GPS for detecting the vehicle's current location from latitude and longitude information, etc.
(Global Po5tionino System
m) device, and the output of each of these sensors (devices) is supplied to the system controller 5.

The system controller 5 has an interface 6 which inputs the outputs of the sensors (devices) 1 to 4 and performs A/D (analog/digital) conversion, etc., and processes various image data which are sequentially sent from the interface 6. CPU (central processing circuit) that calculates vehicle movement 3, etc. based on the output data of each sensor (device) 1 to 4
7 and a ROM (read-only) in which various processing programs and other necessary information for the CPU 7 are stored in advance.
RAM (random memory) 8 and RAM (random
access memory) 9 and the so-called CD-ROM 11C
A recording medium 10 consisting of a card etc., on which digitized (numerical) map information is recorded, and a V-RAM (
Graphic memory 1 consisting of Video RAM), etc.
1, and a graphic controller 0-13 that controls graphic data such as a map sent from the CPU 7 to be drawn in a graphic memory 11 and displayed as an image on a display 12 such as a CRT. The input device 14 consists of a keyboard, etc., and various commands are issued to the system controllers 0-5 by manual keystrokes according to names used.

Next, the basic procedure executed by the CPU 7 will be explained according to the flowchart shown in FIG.

The CPLI 7 first initializes to execute the program (step 81), and then determines whether the current location of the vehicle has been set (step 82>. If the current location is not set, the current location is Execution of a set routine (step S3), for example, the current location is set using the key input from the input device 14.Next, the mileage is set to zero (step S4), followed by key input from the input device 14. It is determined whether or not (step 85).

If there is no key personnel available, a map of the area around the current location is displayed on the display 12, and the current location of the vehicle and its direction are displayed on this map using, for example, a vehicle mark, and when the vehicle moves, the map scrolls as the vehicle moves. Furthermore, when the vehicle position is about to exceed the range of the map data currently on the graphic memory 11, the necessary map data is read out from the recording medium 10 and displayed on the display 12 (step 86).

If there is key human power, the current location is reset according to the input data (step $7), sensor correction (step S8)
, destination setting (step 89), and map enlargement/reduction (step 510) routines are executed.

In addition, as shown in FIG. 3, the CPU 7 uses interrupt processing by a timer to constantly measure the vehicle's direction based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2, which is an auxiliary direction sensor, at fixed time intervals ( step 811,
812).

By the way, the geomagnetic sensor 1 generally consists of a pair of magnetic detection elements arranged on the same plane with a phase angle of 90° to each other, and one of the pair of elements is, for example, U
One detects the geomagnetic component in the direction (north direction), and the other detects the geomagnetic component in the V direction (east direction). When the geomagnetic sensor 1 having such a configuration is rotated once on a horizontal plane, the output data from both detection elements U and ■ generates a circle centered at the origin O of the Uv rectangular coordinate system as shown in FIG. The trajectory is drawn. Therefore, for example, point P
The clockwise azimuth θ from the north (0 wheel) at (LJ+, V+) is calculated by the following equation (1).

θ-tau (U/V)・=・(1) Therefore, such a geomagnetic sensor 1 is attached to the vehicle at a predetermined angle with respect to the front and rear or left and right directions of the vehicle, and the detection of both U and By performing ml of equation (1) based on the output data from the element, the direction of the vehicle can be detected.

Ideally, only magnetic flux due to the earth's magnetic field exists around the geomagnetic sensor 1, but in a vehicle,
Generally, there is extra magnetic flux due to magnetization of the body steel plate. Therefore, in order to remove the influence of magnetization of the vehicle body and perform accurate direction detection,
For example, a method disclosed in VJ Publication No. 57-28208@ is proposed. In this method, when the magnetic sensing element is fixed to the vehicle and there is no relative displacement between the two, the center of a circle drawn by plotting the output obtained by rotating the magnetic sensing element once Considering that the distance from the coordinate origin is due to the influence of body magnetization, the output data obtained from the rain detection element is corrected so that the center of the drawn circle moves to the origin, and the body The effect of magnetization is removed. To be more specific, the center Q of the circle drawn by the output of the rain detection element is located at a position moved from the origin, as shown by ■ in FIG. Therefore, the output U of the rain detection element.

The maximum values LIm, Vw and the minimum values Un, Van of (2) are determined, and the coordinates of the center Q are calculated from these using the following equation (2).

Llo = (LJm+Um)/2 )......(2) Vo = (V whale + V axis)/2 Using the calculated values Llo and Vo, the output value of each magnetic detection element is determined by the following formula (3). U and (2) are corrected, and the direction is calculated from the corrected U' and V'.

U==U−Ll.

) (3) V-=V-V.

Furthermore, in order to increase the reliability of the output data of the geomagnetic sensor 1, a tolerance range (hereinafter referred to as a window) within which variation in the output data of the geomagnetic sensor 1 is allowed is set based on a certain rule. That is, as shown by the diagonal lines in Fig. 5, a window is set in the angular direction based on the previously obtained azimuth data (Un-+, Vn-+), and the azimuth data obtained previously and the azimuth data obtained this time are compared. The difference is constantly monitored, and if the current direction data is significantly different from the previous direction data, that is, if it is outside the window, that data is treated as an error and the data is changed to predetermined data, such as the previous data or the number of times in the past. is optional) By replacing the data with the average value, the reliability of the output data of the geomagnetic sensor 1 is improved. Furthermore, since the data output from the geomagnetic sensor 1 mathematically applies to the equation of a circle, data that does not fit into this equation can also be determined as an error. However, the data varies due to A/DI conversion errors, etc.
The window is set with a certain width in the radial direction as well. In FIG. 5, α represents an angle tolerance, and β represents a radius tolerance.

Note that since the difference in orientation varies depending on the time interval at which the orientation data is obtained, it is also possible to determine it based on the relationship between the angular velocity and the vehicle speed. For example, if the vehicle speed is 40 [km/hl] and the maximum angular velocity trace is 30 [degrees/S], if the output data of the geomagnetic sensor 1 exceeds this range, it will be considered an error, and Replace with the average value of the data. In addition, when setting the window using an angle, it is also possible to set the angle according to changes in vehicle speed.In addition to setting the angle with a linear number of squares relative to the vehicle speed, it is also possible to set the window with a certain hysteresis. This eliminates the need to frequently change the corresponding angle in response to changes in vehicle speed.

Next, the procedure of the geomagnetic sensor data processing method according to the present invention executed by CPLJ7 will be explained according to the flowchart of FIG.

The CPL 17 first determines whether so-called one-rotation correction has been completed (step 520). If it has not been completed, execute the one-rotation correction routine (step 521).
). In this one-rotation correction routine, the geomagnetic sensor 1 is
The vehicle carrying A is rotated once, and the values of Uo, Vo (center I), and radius r are determined. The determined value is stored in RAM9.

Next, an initial orientation is set (step 522).

Since the vehicle is stationary when the engine is started and the orientation of the vehicle should be constant, it is preferable to set the initial value at this time. After setting the initial orientation, the output data of the geomagnetic sensor 1 is taken in (step 823), and it is determined whether or not this output data falls within the aforementioned window (the shaded area in FIG. 5) (step 524). If it is within the window, the direction of the vehicle is calculated based on the above-mentioned equations (1) to (3) from the captured output data of the geomagnetic center 1 (step 525). The calculated direction is displayed together with the map on the display 12 in step S6 in the flowchart of FIG. Subsequently, the azimuth determined from the output data of the angular velocity sensor 2 is matched with the azimuth determined from the output data of the geomagnetic sensor 1 (step 526).

Next, the count wIN of the window error counter, which counts the number of times the output data of the geomagnetic sensor 1 is outside the window, and the count value E, of the center value deviation judgment counter, which counts the number of times the center value deviation has occurred, are both set to zero. Step 527), then return to step 823. The above flow indicates that the output data of the geomagnetic sensor 1 is within the window without being affected by the disturbance magnetic field.
This is the flow during normal operation.

On the other hand, if the output data of the geomagnetic sensor 1 does not fit into the window, the count value N of the window error counter is incremented by "1" in step 829.
), then it is determined whether the count value N has reached the maximum window error severity Nm (step 530). Then, until the window error reaches the maximum of 11 Nmx, the output data of the geomagnetic sensor 1 that has been imported this time is regarded as an error, and the direction determined from the past direction or the output data of the auxiliary direction sensor such as the angular velocity sensor 2 is used.Step 531) , and then returns to step 823.

Further, when the count value N of the window error counter reaches the window error maximum value Nwa, the count value E of the center value deviation counter is counted up by 1'' (step 532), and then the count value E is It is determined whether the determination maximum value Ewrx has been reached (step 533).

Then, in step 834, the timer is set for a certain period of time until the center value deviation judgment maximum 'rNEw is reached.
), the output data of the geomagnetic sensor 1 is captured (step 836) until it is determined that time is up in step 835.
), the direction i! based on that data! 1 Perform n (
step 537). That is, if the output data of the geomagnetic sensor 1 does not fit into the window for a certain period of time, the window is temporarily canceled and error processing is not performed for a certain period of time. Through this processing, it is possible to cope with the case where non-standard data is captured due to, for example, a sudden steering wheel.

As described above, if the output data of the geomagnetic sensor 1 is not within the window, the reliability of the orientation determined from this data is poor, so the orientation determined from the output data of the angular velocity sensor 2 is left as is.

When the count value E of the center value deviation counter reaches the center value deviation determination maximum value EII11x, it is determined that the center value deviation has occurred, and the center value f deviation is corrected using other data (step 838), and the window error counter is The count value N of the center value deviation determination counter and the count value E of the center value deviation determination counter are both set to zero (step 539), and then step 82
Return to 3. For example, when a vehicle passes through a railroad crossing, the vehicle body is magnetized by the strong magnetic field at the railroad crossing, which causes the output data of the geomagnetic sensor 1 to have a DC component, resulting in a center value shift as shown in FIG. , so that it is no longer possible to correctly determine the direction. If the vehicle body is magnetized in this way and a center value shift occurs, the output data of the geomagnetic sensor 1 will not fit into the window no matter how long it takes.
By counting the number of times the window does not enter the window for a certain period of time, it can be determined that this state has occurred. In such a situation, even if the output data of the geomagnetic sensor 1 has a DC component, only the center coordinates of the circle equation change and the radius r does not change (the strength of the geomagnetic field changes). (the radius r remains unchanged unless

In the correction of this center value deviation, for example, output data of the angular velocity sensor 2 is used as other data. Although the angular velocity sensor 2 cannot determine the absolute value, it can determine the angle by integrating on the time axis. The known value when the center value is shifted is geomagnetic sensor 1.
output data (Ll, V), the radius r determined by one rotation correction, and the output data of the angular velocity sensor 2,
These values have the relationship expressed by the following equation (4).

U=r-3inθ+UO V−r−cosθ+V.

By transforming the equation (4), the following equation (5) is obtained.

Uo =Ur-sinθ Vo =Vr-cosθ Therefore, the current center value (Uo, VO) can be obtained from equation (5).

Further, as another method for determining the angle θ, it is also possible to measure the angle of the road on which the vehicle is currently traveling using map data, and use this road angle as the angle θ. That is, a road is represented by a line (line segment) connecting two points, each point is digitized and stored in the recording medium 10 as map data, and from this map data the line segment where the vehicle is located is determined. Both ends of (
Since the value of point 2) is known, the angle θ can be determined by calculating the slope of the linear function from this value.

Next, the procedure of another embodiment of the geomagnetic sensor data processing method according to the present invention executed by the CPLJ7 will be described with reference to the flowcharts of FIGS. 8 and 9.

The CPU 7 performs interrupt processing as shown in FIG. 8 every unit traveling distance or every intermediate time. That is, the output data U and ■ of the geomagnetic sensor 1 and the output data G of the angular velocity sensor 2 are taken in and stored in the respective set memories (RA
M9) Save in the above array and update the pointer and counter (step 540), then judge whether the output data of the geomagnetic sensor 1 is in the window mentioned above (the shaded area in Fig. 5). (Step 5
41). If it is in the window, perform steps (1) to (3) mentioned above from the output data of the imported geomagnetic sensor 1.
Calculate the vehicle heading based on the formula (step 542)
. In addition, if it is within the window, it is assumed that the reliability of the h position data obtained from the geomagnetic sensor 1 is high, and the direction obtained from the angular velocity sensor 2 is set to the geomagnetic sensor 1.
(step 543).
). As a result, the reliability of the orientation determined by the acceleration sensor 2 can always be maintained at the same level as the reliability of the orientation determined by the geomagnetic sensor 1. Subsequently, the count value N of the window error counter that counts the number of times the output data of the geomagnetic sensor 1 is outside the window is set to zero (step 544), and the interrupt routine is ended.

On the other hand, if the output data of the geomagnetic sensor 1 does not fall within the window, the count value N of the window error counter is incremented (step 545), and then the count value N reaches the maximum window error value Nm. It is determined whether or not (step 846). Then, if the window error maximum value Nwa has not been reached,
Step 5: Use the past direction or the direction determined from the output data of the auxiliary direction sensor such as the angular velocity sensor 2.
47) If the maximum value N5ax is reached, set a correction flag to monitor that the output data of the geomagnetic sensor 1 does not fall within the window for a predetermined period of time (Step 848), and end the interrupt routine. .

FIG. 9 shows a routine for verifying the correlation between data between the geomagnetic sensor 1 and the angular velocity sensor 2, and correcting the output data of the geomagnetic sensor 1. It is called and executed every time.

The CPU 7 first determines whether or not the above-mentioned correction flag is set (step 550), and if it is set, the geomagnetic sensor 1 and the angular velocity sensor 2
Data extraction for verification is performed from the raw data U, ■, and G (step $51). In this calculation, the output data G of the angular velocity sensor 2 is expressed as X using the following equation using the center values Llo and Vo of the output data of the geomagnetic sensor 1 and the radius r of the circle.

Converted to Y coordinate system.

Qx-r-CO3(G)+VO Gy=r-sin(G)+U.

As a result, the output data of the angular velocity sensor 2 is converted into the coordinate system of the output data of the geomagnetic sensor 1, and in the normal state,
U=Gy, V=Gx.

Here, when the vehicle body is moved i4, as shown in FIG. 10, the output data of the geomagnetic sensor 1 will be distributed on the circumference of the radius r that has been translated in parallel by the magnetization vector. Therefore, if normal data processing is performed, an incorrect direction will be detected.

Therefore, in the next step 852, the displacement in the X-axis direction
(i) = V (i) - Standard deviation of G x (i) (
Find 7U. Then, this standard deviation σU is compared with a predetermined set value σth (step 553), and if it is within the set value σth, the process proceeds to the next step 854. Here, the displacement in the Y-axis direction Yd(i) = U(i) - G
Find the standard deviation σV of y(i). Then, this standard deviation σV is compared with a predetermined set value σth (step 555), and if it is within the set value σth, the center value Uo
, Vo as the estimated value Uon , V.

. (Step 856) Then, the correction flag is reset (Step 557). Thereafter, the vehicle direction is calculated using the updated center values Uo and Vo. Mark +1! If the deviations σU and σV do not fall within the set values, this routine is repeated until the data is updated so that they fall within the set values.

As explained above, according to the present invention, a tolerance range is set in which fluctuations in the output data of the geomagnetic sensor are allowed, and the output data of the geomagnetic sensor is not continuously within this tolerance range for a predetermined period of time. If not, by correcting the output data of the geomagnetic sensor based on predetermined data, even if the geomagnetic sensor continues to receive disturbances or the vehicle body becomes magnetized due to passing through a railroad crossing, etc. Since reliable azimuth data can be obtained by eliminating the influence of the disturbance, it is possible to detect the vehicle direction more accurately and realize highly accurate navigation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an in-vehicle video game controller to which the data processing method of the geomagnetic sensor according to the present invention is applied, and FIGS. 2 and 3 show the basic steps executed by the CPU in FIG. 1. 4 is a line diagram showing the locus drawn by the output data of the geomagnetic sensor, Fig. 5 is a line diagram showing the state in which a window is set on the locus drawn by the output data of the geomagnetic sensor, and Fig. 6 is a line diagram showing the locus drawn by the output data of the geomagnetic sensor. 70-D, No. 7 showing the steps of the data processing method of the geomagnetic sensor according to the present invention executed by the CPU in
The figure is a diagram showing the state in which the locus drawn by the output data of the geomagnetic sensor has a center value deviation, and Figures 8 and 9 are for the CPU.
FIG. 10 is a flowchart showing the procedure of another embodiment of the geomagnetic sensor data processing method according to the present invention, which is executed by FIG. Explanation of symbols of main parts

Claims (3)

[Claims] (1) A data processing method for a geomagnetic sensor mounted on a vehicle and outputting azimuth data of the vehicle based on geomagnetism, the geomagnetic sensor A data processing method for a geomagnetic sensor, characterized in that when the output data of the geomagnetic sensor does not fall within the permissible range for a predetermined period of time, the output data of the geomagnetic sensor is corrected based on predetermined data. (2) The geomagnetic sensor data processing method according to claim 1, wherein the predetermined data is output data of an angular velocity sensor that detects the angular velocity of the vehicle. (3) The data processing method for a geomagnetic sensor according to claim 1, wherein the predetermined data is map data indicating at least two positions in front and behind where the vehicle is located.