JPH0543257B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a data processing method for an angular velocity sensor, and more particularly to a data processing method for an angular velocity sensor in a vehicle-mounted navigation device.

Background Art 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. being developed.

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

To find the direction from the output data of the angular velocity sensor, first, the data output by the angular velocity sensor when there is no angular velocity (angular velocity is zero) is set as the center value Gdc of the sensor output, and the displacement is calculated based on this center value Gdc. Find the direction by integrating. At this time, the center value Gdc may change due to temperature drift or the like. If the central value Gde changes, the error will appear as a drift in the bearing when calculating the bearing. Furthermore, due to the characteristics of the electrical circuit (for example, operational amplifier) used to detect angular velocity sensor data, even though the vehicle has actually rotated 90 degrees, the rotation angle determined from the output data of the angular velocity sensor may not be exactly 90 degrees. There may be cases where this is not the case. Therefore, a correction coefficient is required to correct this error. However, when determining this correction coefficient, if the rotation angle of the vehicle is not accurately determined, an error will occur here as well.

Summary of the invention The present invention has been made in view of the above points, and
It is an object of the present invention to provide a data processing method for an angular velocity sensor that makes it possible to accurately detect the azimuth of a vehicle by increasing the reliability of azimuth data obtained by the angular velocity sensor.

The angular velocity sensor data processing method according to the present invention detects that the vehicle has made one rotation, calculates a rotation angle based on the output data of the angular velocity sensor during this one rotation, and a rotation angle based on the output data of the geomagnetic sensor, and calculates the rotation angle based on the output data of the geomagnetic sensor. It is characterized in that the ratio of rotation angles is used as a correction coefficient for the angular velocity sensor.

Embodiments 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 on-vehicle navigation device to which the angular velocity sensor data processing method according to the present invention is applied. In the same figure, 1
2 is a geomagnetic sensor for outputting vehicle orientation data based on geomagnetism (earth magnetic field); 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 (Global Positioning System) device for detecting the current location of the vehicle from latitude and longitude information, and the outputs of these sensors (devices) are supplied to the system controller 5.

The system controller 5 includes each sensor (device)
an interface 6 that receives the outputs of 1 to 4 as input and performs A/D (analog/digital) conversion, etc.;
A CPU (central processing circuit) 7 that processes various image data and calculates the amount of movement of the vehicle based on the output data of each sensor (device) 1 to 4 sequentially sent from the interface 6;
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 in which information necessary for executing programs is written and read.
(Random Access Memory) 9 and the so-called
A recording medium 10 consisting of a CD-ROM, an IC card, etc., on which digitized (numerical) map information is recorded, a graphics memory 11 consisting of a V-RAM (Video RAM), etc., and information sent from the CPU 7. The controller 13 includes a graphics controller 13 that controls graphics data such as a map to be drawn in a graphics memory 11 and displayed as an image on a display 12 such as a CRT. The input device 14 includes a keyboard or the like, and issues various commands and the like to the system controller 5 through key input by the user.

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

The CPU 7 first performs initialization (steps) to execute the program.
S1), then it is determined whether the current location of the vehicle has been set (step S2). If the current location has not been set, a current location setting routine is executed (step S3), for example, the current location is set by key input on the input device 14. Next, the travel distance is set to zero (step S4), and then it is determined whether or not there is a key input from the input device 14 (step S5).

If there is no key input, a map of the area around the current location is displayed on the display 12, and the current location and direction of the vehicle 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 S6).

When there is a key input, the following routines are executed according to the input data: resetting the current location (step S7), sensor correction (step S8), setting the destination (step S9), and enlarging/reducing the map (step S10). do.

In addition, the CPU 7 constantly calculates the vehicle direction based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at fixed time intervals, as shown in FIG.
S11, S12).

By the way, the geomagnetic sensor 1 generally consists of a pair of magnetic detection elements arranged with a phase angle of 90 degrees to each other on the same plane, and one of these elements detects the geomagnetic component in the U direction (north direction), for example. 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 the U and V detection elements determines that the geomagnetic sensor 1 is centered at the origin O of the UV orthogonal coordinate system, as shown in FIG. A circular locus is drawn. Therefore, for example, the clockwise azimuth θ from the north (U axis) at point P (U ₁ , V ₁ ) is calculated by the following equation (1).

θ=tan ^-1 (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 both U and V The direction of the vehicle can be detected by calculating equation (1) based on the output data from the detection element.

Ideally, only magnetic flux due to the earth's magnetic field would exist around the geomagnetic sensor 1, but in vehicles, it is common for there to be extra magnetic flux due to the magnetization of the body steel plate, etc. It is. Therefore, in order to eliminate the influence of magnetization of the vehicle body and perform accurate direction detection, a method disclosed in, for example, Japanese Patent Laid-Open No. 57-28208 has been proposed. In this method, when the U and V magnetic detection elements are fixed to the vehicle and there is no relative displacement between them, the center of a circle drawn by plotting the output obtained by rotating the magnetic detection elements once, Considering that the distance from the coordinate origin is due to the influence of body magnetization, the output data obtained from both detection elements is corrected so that the center of the drawn circle moves to the origin, and the body magnetization is adjusted. We are trying to remove the influence of magnetism. To be more specific, the center Q of the circle drawn by the outputs of both detection elements is located at a position moved from the origin, as shown by the circle in FIG. Therefore, the maximum values U _nax , V _nax and the minimum values U _nio , V _nio of the outputs U and V of both detection elements are determined.
, and then calculate the coordinates of the center Q using the following equation (2).

U _O = (U _nax + U _nio / 2 V _O = (V _nax + V _nio ) / 2 ... (2) Using the calculated values U _O and V _O , each magnetic sensing element is determined by the following equation (3). The output values U and V of are corrected,
The direction is calculated from the corrected U' and V'.

U′=U−U _O V′=V−V _O ……(3) Also, in order to increase the reliability of the output data of the geomagnetic sensor 1, fluctuations in the output data of the geomagnetic sensor 1 are allowed based on a certain rule. Set a permissible range (hereinafter referred to as a window). That is, as shown by diagonal lines in Figure 5, a window is set in the angular direction based on the previously determined azimuth data (U _o-1 , V _o-1 ), and the previously determined azimuth data and the currently determined azimuth data are If the azimuth data obtained this time is significantly different from the azimuth data obtained last time, 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. By replacing the data with the average value (the number of times is arbitrary), 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, 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 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 angular velocity and vehicle speed. For example, the vehicle speed is 40 [Km/h]
In this case, if the maximum angular velocity is 30 [degrees/s], if the output data of the geomagnetic sensor 1 exceeds this range, it will be treated 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 the vehicle speed, it is also possible to set the window according to the vehicle speed by adding 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. The CPU 7 can determine the current orientation by time-integrating the output data of the angular velocity sensor 2 and calculating the orientation that has changed from the angular velocity using interrupt processing by a timer. First, the CPU 7 converts the data output by the angular velocity sensor 2 in a state where there is no angular velocity (angular velocity is zero) to the center value of the sensor output.
Gdc, the displacement is determined based on this center value Gdc, and the orientation is determined by integrating over time. At this time, the center value Gdc may change due to temperature drift or the like. If the central value Gdc changes, the error will appear as a drift in the orientation when calculating the orientation. Furthermore, due to the characteristics of the electrical circuit (for example, operational amplifier) used to detect angular velocity sensor data, even though the vehicle has actually rotated 90 degrees, the rotation angle determined from the output data of the angular velocity sensor may not be exactly 90 degrees. There may be cases where this is not the case. Therefore, a correction coefficient is required to correct this error. However, when calculating this correction coefficient,
If the rotation angle of the vehicle is not accurately determined, errors will occur here as well.

Next, the steps of the data processing method of the angular velocity sensor according to the present invention executed by the CPU 7 will be described in the sixth section.
This will be explained according to the flowchart shown in the figure.

First, the CPU 7 determines whether the vehicle is stationary (step S20). If it is not stationary, this judgment is repeated until it is determined that it is stationary. If it is determined that it is stationary, the direction determined by the angular velocity sensor 2 is set to zero, and the correction coefficient α of the angular velocity sensor 2 is set to the initial value (α = 1.0).
(S21). As a result, the azimuth data obtained from the angular velocity sensor 2 is corrected by the correction coefficient α
will not be affected. Next, store the output data of the geomagnetic sensor 1 at this time in the memory (RAM9) as a start value (step
S22). Then, by rotating the vehicle once,
Since one-turn correction is performed to remove the influence of magnetization of the vehicle body and perform accurate direction detection, the process waits for this one-turn correction to be completed (step S23). Note that this one-turn correction, as described above, is executed by the method disclosed in, for example, Japanese Patent Application Laid-Open No. 57-28208.

Once the one-rotation correction is completed, the geomagnetic sensor 1
The output data at the end of the process is stored in the memory (RAM9) (step S24). At this point, the azimuth calculation by the angular velocity sensor ₂ in the routine shown in FIG.
(step S25).

Next, using the coordinates U _O and V _O of the center Q of the circle in Fig. 4 obtained by one rotation correction, step S22 is performed.
The vehicle direction at the start is determined from the output data of the geomagnetic sensor 1 at the start of the one-rotation correction stored in step S24, and further from the output data of the geomagnetic sensor 1 at the end of the one-rotation correction stored in step S24. The direction of the vehicle at the end of the process is determined, and the rotation angle θ ₁ that the vehicle rotated during one rotation correction from both directions is calculated (step S26). And, I memorized it in Stetsu S25,
The ratio (θ ₂ /θ ₁ ) between the rotation angle θ ₂ by the angular velocity sensor 2 and the rotation angle θ ₁ by the magnetic sensor 1 is determined, and this is set as a new correction coefficient α for the angular velocity sensor 2 (step S27).

From now on, when calculating the direction from the output data of the angular velocity sensor 2 in step S12 of FIG.
By using this correction coefficient α, it is possible to correct the drift caused by the characteristics of the electric circuit, etc., so that the azimuth detection by the angular velocity sensor 2 can be performed more accurately.

Effects of the Invention As explained above, according to the present invention, a highly reliable correction coefficient necessary for calculating the azimuth of the angular velocity sensor is obtained by using the one-rotation correction of the geomagnetic sensor. Since the correction of the geomagnetic sensor is completed at the same time, it is possible to perform subsequent direction detection more accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device to which the angular velocity sensor data processing method according to the present invention is applied, and FIGS. 2 and 3 show the basic structure executed by the CPU in FIG. A flowchart showing the procedure, Figure 4 is a diagram showing the trajectory drawn by the output data of the geomagnetic sensor, Figure 5 is a diagram showing the state where a window is set on the trajectory drawn by the output data of the geomagnetic sensor, and Figure 6 is a diagram showing the trajectory drawn by the output data of the geomagnetic sensor. 2 is a flowchart showing the steps of a data processing method for an angular velocity sensor according to the present invention, which is executed by the CPU in FIG. 1; 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.

Claims (1)

[Scope of Claims] 1. An angular velocity sensor that detects the angular velocity of a vehicle; and a geomagnetic sensor that outputs azimuth data of the vehicle based on geomagnetism; A data processing method for an angular velocity sensor in an in-vehicle navigation device that detects the orientation of a vehicle, the method detecting that the vehicle has made one rotation, and determining the rotation angle based on the output data of the angular velocity sensor during this one rotation and the geomagnetic sensor. A data processing method for an angular velocity sensor, characterized in that rotation angles are calculated based on output data of the angular velocity sensor, and a ratio of these rotation angles is used as a correction coefficient for the angular velocity sensor. 2. To determine that the vehicle has made one rotation,
2. The angular velocity sensor data processing method according to claim 1, wherein output data of the geomagnetic sensor is used. 3. The angular velocity sensor data processing method according to claim 2, wherein at the same time as determining that the vehicle has made one rotation, one rotation correction of the geomagnetic sensor is also performed.