JPS63109313A - Method for detecting azimuth of vehicle - Google Patents

Abstract

PURPOSE:To detect an accurate azimuth, by enhancing the reliability of the azimuth calculated by an angular velocity sensor. CONSTITUTION:At first, the tolerant range permitting the variation in the output data of an earth magnetism sensor 1 is set to a ROM8. Next, when the output data of the magnetism sensor 1 is within said range, the reliability of the output data is judged to be high to allow the azimuth calculated from the output data of an angular velocity sensor 2 coincide with the azimuth calculated from the output data of the earth magnetism sensor 1 and the azimuth calculated from the angular velocity sensor 2 is corrected. By this method, the drift generated by azimuth calculation is canceled on the basis of the output data of the earth magnetism sensor 1 detecting an absolute azimuth. When the output data of the earth magnetism sensor 1 does not enter the tolerant range, since the reliability of the azimuth calculated from said data is inferior, the azimuth calculated from the output data of the angular velocity sensor 2 is allowed to stand as it is. By this method, the azimuth of a vehicle can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION 1/5 The present invention relates to a method for detecting the orientation of a vehicle, and more particularly to a method for detecting the orientation of a vehicle using an angular velocity sensor in an on-vehicle navigation device.

In recent years, research has been conducted into in-vehicle navigation devices 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. , has been developed.

Such a navigation device requires an azimuth sensor that detects the azimuth of the vehicle, and as this azimuth sensor, for example, an angular velocity sensor that detects the azimuth of the vehicle by detecting the angular velocity of the vehicle is used. However, since the azimuth determined from the output data of this angular velocity sensor is not an absolute azimuth, a drift may occur in the detected azimuth.

11 Momme JJ The present invention was made in view of the above-mentioned points, and an object of the present invention is to provide a method for detecting the direction of a vehicle that enables accurate direction detection by increasing the reliability of the direction determined by the angular velocity sensor. shall be.

The vehicle orientation detection method according to the present invention sets a tolerance range that allows variations in the output data of the geomagnetic sensor, and as long as the output data of the geomagnetic sensor is within the tolerance range, the orientation determined from the output data of the geomagnetic sensor is determined. The azimuth determined by the angular velocity sensor is corrected by matching the azimuth determined from the output data of the angular velocity sensor.

Tomo-Sei-3 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 an in-vehicle navigation device to which a vehicle orientation detection method according to the present invention is applied. In the figure, 1 is a geomagnetic sensor for outputting vehicle orientation data based on geomagnetism (earth's magnetic field), 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, and 3 is a geomagnetic sensor for detecting the distance traveled by the vehicle. Mileage sensor, 4 is Gp for detecting the current location of the vehicle from latitude and longitude information etc.
3 (Global Positioning System
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. A CPU (central processing circuit) 7 that calculates vehicle movement 1, etc. based on the output data of each sensor (device) 1 to 4.
, a ROM (read only memory) 8 in which various processing programs for the CPU 7 and other necessary information are written in advance, and a RAM (random memory) in which information necessary for executing programs is written and read. access memory) 9, a recording medium 10 consisting of a so-called CD-ROM, an IC card, etc., on which digitized (numerical) map information is recorded, and a V-RAM (Vi
The graphics controller 13 is configured to draw graphic data such as a map sent from the CPtJ7 in the graphic memory 11 and display it as an image on a display 12 such as a CRT. ing. The input device 14 consists of a keyboard or the like, and various commands and the like are issued to the system controller 5 by manual keystrokes according to names used.

Next, the basic steps performed by CPLJ7 are:
This will be explained according to the flowchart shown in FIG.

The CPU 7 first initializes the program to execute it (step 81), and then determines whether the current location of the vehicle has been set (step 32>. If the current location is not set, the current location is A set routine is executed (step S3), for example, the current location is set by manual keystrokes on the input device 14.Next, the mileage is set to zero (step S4), and then whether there is manual keystrokes from the input device 14 or not. 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).

Here, as shown in FIG. 3, by color-coding the vehicle mark M into the left side and the right side with respect to the traveling direction of the vehicle and distinguishing between the left and right sides, the vehicle mark M can, for example, move on the screen of the display 12 from above. Even when the vehicle is traveling downwards, it is possible to distinguish between the right side and the left side with respect to the direction of travel, so no matter which direction the vehicle mark M is facing on the screen of the display 12, when the vehicle turns, whether it is a right turn or a left turn. This makes it easy to identify what has been done.

Although the vehicle mark M is color-coded to the left and right in relation to the direction of travel of the vehicle, the present invention is not limited to this.In short, when displaying a map screen with the direction on the map constant regardless of the direction of the vehicle. In other words, it is sufficient if the vehicle mark displayed on the map is asymmetrical with respect to the direction of travel of the vehicle.

If there is key human power, the current location is reset (step S7) and sensor correction (step S8) according to the input data.
, destination setting (step 39), and map enlargement/reduction (step 510) routines are executed.

Although it is assumed that setting the current location in step S7 and setting the destination in step S9 is done manually, as shown in FIG. It is also possible to input data by reading it with a barcode detection device (not shown), which saves time and effort for inputting data.

Here, it is preferable that what kind of data is indicated by the barcode differs depending on the scale of the map.

For example, when the scale is small, rough data such as prefecture names and municipal names are shown, and as the scale becomes larger, detailed data such as parks, amusement parks, hotels, department stores, etc. are shown. Also, if many types of data are shown on the same map, the map will become difficult to read, so for example,
It is also possible to limit the information to one type, such as an atlas that only shows restaurants.

In addition, the CPU 7 constantly calculates the direction of the vehicle based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at regular time intervals, as shown in FIG. 5, by interrupt processing using a timer (step S11.812).

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
The geomagnetic component in the direction (north direction) is detected, and the other is in the V direction (
It is designed to detect the geomagnetic component in the east direction. When the geomagnetic sensor 1 having such a configuration is rotated once on a horizontal plane, the output data from both the detection elements U and II generates a circle centered at the origin 0 of the U and Cartesian coordinate system, as shown in FIG. ■The trajectory is drawn. Therefore, for example, point P
The clockwise azimuth θ from the north (U axis) at (U+, V+) is calculated by the following equation (1).

θ−tan→ (Ll/V) ・−・−(1) Therefore,
Such a geomagnetic sensor 1 is attached to a vehicle at a predetermined angle with respect to the front and rear or left and right directions of the vehicle.
By performing the calculation of equation (1) based on the output data from both detection elements, 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 Japanese Unexamined Patent Publication No. 57-28208 is proposed. In this method, U, ■ the center of a circle drawn by plotting the output obtained by rotating the magnetic sensing element once when the magnetic sensing element is fixed to the vehicle and there is no relative displacement between the two; 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 body magnetization is adjusted. We are trying to remove the influence of magnetism. To be more specific, the output of the rain detection element is drawn (the center Q of the circle is located at a position moved from the origin, as shown by ■ in FIG. 6). Therefore, the output U of the rain detection element is drawn.

The maximum values Um and Vaa and the minimum values L1mn and Vin of (2) are determined, and the coordinates of the center Q are calculated from these using the following equation (2).

Llo = (LJmx+Umn) / 2)...
...(2) Vomi (■諒+V mn) / 2 Using the calculated values Uo and Vo, the output values U and ■ of each magnetic detection element are corrected by the following formula (3), and the corrected values are The direction is calculated from 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) is set based on a certain rule to allow variation in the output data of the geomagnetic sensor 1. In other words, as shown by diagonal lines in Figure 7,
A window is set in the angular direction using the previously obtained azimuth data (Un→, Vn-+) as a reference, and the difference between the previously obtained azimuth data and the currently obtained azimuth data is constantly monitored. If the direction data is significantly different from the obtained direction data, that is, if it is outside the window, that data should be treated as an error and replaced with predetermined data, such as the previous data or the average value of data from a number of times in the past (the number of times is arbitrary). This increases the reliability of the output data of the geomagnetic sensor 1. 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, since the data varies due to A/D conversion errors and the like, the window is set with a certain width in the radial direction. In FIG. 7, α indicates an angle tolerance, and β indicates 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 angular velocity and vehicle speed. For example, when the vehicle speed is 40 [km/h], the maximum angular velocity is 30 [1! /s], when the output data of the geomagnetic sensor 1 exceeds this range, it is determined as an error and replaced with the previous data or the average value of several past data.

In addition, when setting a window using an angle, it is also possible to set the angle according to changes in vehicle speed.In addition to setting the angle as a linear function relative to vehicle speed, it is also possible to set a window according to vehicle speed by providing a certain hysteresis. This eliminates the need to frequently change the corresponding angle in response to changes.

Incidentally, the angular velocity sensor 2 generally outputs data proportional to the angular velocity around the sensor sensing axis. C.P.L.I.
7 is the angular velocity sensor 2 due to the interrupt processing by the timer.
The current heading can be determined by integrating the output data over time and calculating the changed heading from the angular velocity.

However, since there is a possibility that errors in this calculation may result in drift, it is necessary to correct the orientation determined by the angular velocity sensor 2.

Next, the procedure of the vehicle direction detection method according to the present invention executed by the CPLI 7 will be explained according to the flowchart of FIG.

The CPU 7 first determines whether so-called one-rotation correction has been completed (step 520). If not completed, execute one rotation correction routine (step 521)
. In this one-rotation correction routine, the vehicle equipped with the geomagnetic sensor 1 is rotated once, and the values of Uo, Vo (center value), 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 fetched (step 823), and it is determined whether or not this output data is included in the window mentioned earlier (the shaded area in FIG. 7) (step 524). If yes, calculate the vehicle's direction based on the above-mentioned equations (1) to (3) from the output data of the geomagnetic sensor 1 (step $25).The calculated direction is shown in Fig. 2. In step S6 in the flowchart, the map is displayed on the display 12.Furthermore, the direction determined from the output data of the angular velocity sensor 2 is matched with the direction determined from the output data of the geomagnetic sensor 1 (step S6). 826).

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

On the other hand, if the output data of the geomagnetic sensor 1 does not fit into the window, the count fiIN of the window error counter is incremented by 1'' in step 52.
9) Then, it is determined whether the count value N has reached the maximum window error value Nw (step 530).
. Then, until the window error maximum value Nw is reached, the output data of the geomagnetic sensor 1 that has been imported this time is regarded as an error, and the direction obtained based on the previous value or the average value of the past several times of the output data of the geomagnetic sensor 1 is After completing step 831), the process returns to step S23.

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

Then, set a timer for a certain period of time until the center value deviation judgment maximum value E's is reached (step 834).
, until it is determined that time is up in step 335, the output data of the geomagnetic sensor 1 is captured (step 836).
, and calculates the orientation based on the data (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 maximum value Ex for determining center value deviation, it is determined that the center value has exceeded,
Correct the center ffi deviation using other data (Step 838), set the count value N of the window error counter and the count value E of the center value deviation determination counter to zero (Step 539), and then return to Step 823. . 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 the center value shifts, the output data of the geomagnetic sensor 1 will not enter the window no matter how long it takes, so by counting the number of times it 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 radius r does not change unless the strength of the earth's magnetism changes.) Therefore, the center coordinates can be determined using other data, and the center value deviation can be corrected.

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 center value has shifted. The values known in the state are the output data (U, V) of the geomagnetic sensor 1, the radius r determined by one rotation correction, and the output data of the angular velocity sensor 2, and these values are expressed by the following equation (4). It becomes.

jl=r-sinθ+U.

) ・・・・・・(4) y=r−cosθ+V.

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

Uo=U-r-sin θ) (5) VO=V-r-cos θ Therefore, the current center value (Uo, VO) can be obtained from equation (5).

Further, as another method for determining the angle θ, the angle of the road on which the vehicle is currently traveling may be calculated using map data, and the angle of this road may be set 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. Since we know the values at both ends (two points) of , we can calculate the slope of the linear function from these values by
By doing 'tW, the angle θ can be found.

As explained above, according to the present invention, a tolerance range is set to allow fluctuations in the output data of the geomagnetic sensor, and when the output data of the geomagnetic sensor is within the range, the output data of the geomagnetic sensor is changed. To ensure high reliability, the drift caused by the azimuth calculation can be eliminated by matching the azimuth determined from the output data of the geomagnetic sensor with the azimuth determined from the output data of the angular velocity sensor, and by correcting the azimuth determined by the angular velocity sensor. Since this can be canceled using the output data of the geomagnetic sensor that detects the absolute orientation, the orientation of the vehicle can be accurately detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device to which the vehicle orientation detection method according to the present invention is applied;
The figure is a flowchart showing the basic procedure executed by the CPU in Figure 1, Figure 3 is a diagram showing an example of a vehicle mark displayed on the display, and Figure 4 is a diagram showing data in the atlas as a barcode. 5 is a flowchart showing the processing procedure of the timer interrupt executed by the CPU in FIG. 1, FIG. 6 is a pictorial diagram showing the trajectory of the output data of the geomagnetic sensor, and FIG. 8 is a flowchart showing the procedure of the vehicle orientation detection method according to the present invention executed by the CPU in FIG. FIG. 3 is a diagram showing a state in which the locus drawn by the output data of FIG. Explanation of symbols of main parts 1... Geomagnetic sensor 2... Angular velocity sensor 5... System controller 7... CPU 10... Recording medium 12...Display 14...
Input device figure 2 + JIL? r2 勺目 4ji朱5 fig.

Claims (1)

[Claims] A direction detection method that includes an angular velocity sensor that detects the angular velocity of a vehicle, and detects the direction of the vehicle based on output data of the angular velocity sensor, and outputs direction data of the vehicle to the vehicle based on geomagnetism. A geomagnetic sensor is also installed, and a tolerance range is set to allow variations in the output data of this geomagnetic sensor, and as long as the output data of the geomagnetic sensor is within this tolerance range, the output data of the angular velocity sensor is calculated. A method for detecting the orientation of a vehicle, characterized in that the orientation is made to match the orientation determined from the output data of the geomagnetic sensor.