JPH0755490A - Apparatus for determining direction of travel - Google Patents

Abstract

PURPOSE:To provide an apparatus for determining the direction of travel, which automatically performs precise correction without relying on geomagnetism. CONSTITUTION:The apparatus comprises a GPS receiving means 11 for receiving an electric wave transmitted from a GPS satellite 10, a speed vector operation means 12 for calculating Doppler effect of the received electric wave by means of the GPS receiving means 11 and finding a speed vector of a vehicle, and a correction means 14 for replacing a vehicle progression direction with the direction of the speed vector on the basis of the output of a relative rotation angle detection means 13 and correcting it in the case where a running speed exceeds a specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling direction identification device for identifying the traveling direction of a vehicle body.

[0002]

2. Description of the Related Art A traveling direction discriminating apparatus has been put into practical use, which discriminates the traveling direction of a moving vehicle and continuously outputs a signal indicating the traveling direction. The traveling direction identification device is used for rotating the vehicle body image displayed on the liquid crystal display provided on the front panel, or for calculating the current position of the vehicle by calculating it in combination with the output of the vehicle speed sensor in the navigation device. ing.

An example of a traveling direction identification device in a conventional navigation device is configured by combining a gyro sensor for measuring a relative rotation angle of a vehicle body and a magnetic sensor for detecting an absolute direction (east, west, north, and south) of the vehicle body. It was here,
Initialize the gyro sensor using the north-south direction obtained by the magnetic sensor, and if the display of the traveling direction by the gyro sensor becomes questionable, initialize the gyro sensor using the north-south direction obtained by the magnetic sensor. cure.

That is, the traveling direction that changes momentarily during operation is measured exclusively by the gyro sensor having high responsiveness and high resolution, but the gyro sensor itself cannot identify the absolute direction (for example, north and south). Therefore, when starting traveling, it is necessary to give the absolute direction by the magnetic sensor as an initial value, and the limit value of the gyro sensor uses the absolute direction because errors accumulate over time and the deviation from the absolute direction expands. It is necessary to periodically correct the limit price of the gyro sensor.

By the way, by calculating the momentary position of the vehicle,
As a navigation device which indicates a vehicle position on a map which is displayed as an image, a navigation device using a radio signal transmitted from a GPS satellite has been put into practical use. GPS (Global Positioning S
The ystem) receiver receives radio waves transmitted from multiple satellites that orbit the earth at an altitude of more than 20,000 km, and expresses them by fixing the longitude, latitude (and altitude) on the earth. The absolute position is calculated. Here, normally, the transmitted signals from four of the 20 or so satellites that orbit the earth in the vertical direction and the horizontal direction are used.

Therefore, for example, by calculating the difference between the absolute positions at the start and end of a fixed time while the vehicle is moving straight, it is possible to obtain the absolute direction fixed to the coordinates of the earth surface. Then, by using this absolute direction, it is possible to periodically correct the limit price of the gyro sensor.

That is, on a straight road, the first absolute position is stored, the vehicle travels straight for a predetermined time, the second absolute position is obtained, and the first absolute position is subtracted from the second absolute position. , The movement vector fixed to the coordinates of the surface of the earth is calculated, and the direction of the movement vector is determined.

[0008]

When the geomagnetic field is detected by the magnetic sensor to identify the absolute direction, there is a problem that the exact absolute direction cannot be detected in a place where the geomagnetic field is disturbed.
For example, when crossing a railroad crossing, traveling along a railroad track, passing by a steel mill or a machine shop, or in an area with abnormal geomagnetism, the absolute reliability of the magnetic sensor output is remarkably high. descend.

When the vehicle body (made of iron) is accidentally magnetized by passing through a place with a strong magnetic field, the offset due to the magnetization of the vehicle body becomes a steady error of the magnetic sensor, and every time the vehicle passes through a place with a strong magnetic field. There is also a problem that the offset amount changes.

Therefore, in the traveling direction identification device which detects the geomagnetism by using the magnetic sensor and periodically corrects the limit value of the gyro sensor, the traveling direction is rather confused when the correction is performed in a place where the geomagnetism is disturbed. become.

On the other hand, since the GPS receiver has an absolute position measurement error of 30 m or more, it is practical except for the case where it is moving at a high speed comparable to an aircraft or when it is traveling for a long distance of several 100 m. There is a problem that a high correction accuracy cannot be obtained.

That is, it is necessary to secure a straight road every time correction is performed, and the correction cannot be started unless the operator specifies the start point and the end point of the straight road. Therefore, if the operator neglects the correction, the error in the output of the traveling direction identification device will endlessly increase.

It is an object of the present invention to provide a traveling direction identification device that automatically executes accurate correction without relying on geomagnetism.

[0014]

FIG. 1 is an explanatory view of the basic constitution of the present invention. In FIG. 1, the traveling direction identification device according to claim 1 is a traveling direction identification device having relative rotation angle detection means for measuring a relative rotation angle with respect to a vehicle body posture, and a GP which receives radio waves transmitted from a GPS satellite 10.
The S receiving means 11 and the speed vector calculating means 12 for calculating the Doppler effect of the signal received by the GPS receiving means 11 to obtain the speed vector of the vehicle body, and the relative rotation angle when the traveling speed is larger than a predetermined value. Correction means 14 for correcting the vehicle body traveling direction based on the output of the detection means 13 by replacing it with the direction of the velocity vector is provided.

A traveling direction identification device according to a second aspect is the first aspect.
In the traveling direction identification device, if the absolute value of the velocity vector obtained by the velocity vector computing means exceeds the predetermined value and is large, the correcting means determines the traveling direction of the vehicle body based on the output of the relative rotation angle detecting means. The means for correction is made by replacing with the direction of the velocity vector.

[0016]

In the traveling direction discriminating apparatus of the present invention, for example, the conventional relative rotation angle detecting means (for example, a gyro sensor) is not mainly used to discriminate the traveling direction, but the absolute direction based on the signal transmitted from the GPS satellite is used. To adopt. And G
The method of calculating the absolute direction from the signal sent from the PS satellite is 2
The absolute direction is obtained by detecting the Doppler effect at one time (from the velocity vector) rather than by the difference between the two absolute positions. Since the velocity vector itself is not the final purpose, its absolute value does not have to be calculated.

In a range where the traveling speed is small, the relative value of the detection error with respect to the obtained speed vector is large, so that the absolute direction by the speed vector is not adopted and the relative rotation angle detecting means corrected in the last absolute direction is used. Adopt the direction of travel by.

For example, in a normal driving condition, when the vehicle reaches a constant speed after the start of traveling, the relative rotation angle detection means initializes the traveling direction, and unless the constant speed is interrupted, the absolute direction based on the speed vector is changed. Substantially continue to be adopted. Then, for example, during a period in which the reception state of the radio wave transmitted from the GPS satellite deteriorates or the velocity vector cannot be calculated with a required accuracy by interrupting a certain velocity, the result of identification of the traveling direction by the relative rotation angle detection means is adopted. .

In FIG. 1, in the traveling direction identification device according to the first aspect, the GPS receiving means 11 extracts the reception signal from the radio wave transmitted from the GPS satellite 10. Then, the velocity vector calculation means 12 calculates the Doppler effect of the received signal to obtain, for example, the inclination of the velocity vector of the vehicle body with respect to the absolute coordinates (latitude, longitude), that is, the absolute direction.

The correction means 14 executes the correction for replacing the traveling direction of the vehicle body with the absolute direction based on the output of the relative rotation angle detection means 13 at the timing when the traveling speed is sufficiently high and the absolute direction can be obtained with high accuracy. After that, the traveling direction of the vehicle body based on the output of the relative rotation angle detection unit 13 is a direction deviated by the relative rotation angle detected by the relative rotation angle detection unit 13 with this absolute direction as a base point.

In the traveling direction identification device of the second aspect, the traveling speed is determined by calculating the absolute value of the speed vector obtained by the speed vector calculating means without relying on a special vehicle speed sensor.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an explanatory view of a traveling direction identification device of an embodiment,
FIG. 3 is a flowchart of the embodiment. In FIG. 2, (a) shows the device configuration and (b) shows the velocity vector. Here, GP
When the velocity vector is calculated based on the output of the S receiver and the absolute value of the velocity vector exceeds a prescribed value, this absolute value is used as the traveling direction output, but when the absolute value of the velocity vector is less than the prescribed value In addition, the result of the identification of the traveling direction by the gyro sensor corrected with the last effective absolute direction is used as the traveling direction output.

In FIG. 2 (a), the traveling direction identification device of the embodiment is a GPS receiver 21 that receives radio waves transmitted from GPS satellites, and a gyro sensor 23 that measures the relative rotation angle of the vehicle body due to steering during driving. , Provides an arithmetic element 22 for performing arithmetic operation using the outputs of the GPS receiver 21 and the gyro sensor 23, various constants and programs necessary for the arithmetic operation to the arithmetic element 22, and temporarily saves the operation result of the arithmetic element 22 It has a memory 24 such as.

The GPS receiver 21 outputs received signals from a plurality of GPS satellites, which are used to calculate the vehicle position (absolute position) every moment, to a navigation device (not shown). Is an individual GPS
In addition to the satellite received signal, the measurement result of the Doppler effect (transition frequency) of the received signal is output.

The computing element 22 identifies the type (number) of the GPS satellite from the received signal of the GPS satellite, and calls the computation information on the identified GPS satellite from the memory 24. And from the measurement result of the Doppler effect of the received signal,
GP specified by calculating the relative speed between the vehicle and GPS satellites
By subtracting the ground speed of the S satellite, the current relative speed of the own vehicle in the coordinate axis connecting the own vehicle and the GPS satellite is obtained.

By performing the same calculation operation on a plurality of GPS satellites, the current relative speed of the vehicle can be obtained with respect to a plurality of coordinate axes corresponding to the plurality of GPS satellites. The velocity vector of the vehicle is calculated with respect to the north, south, east, and west coordinate axes.

For example, as shown in FIG. 2 (b), the first G
When the relative velocity vector in the longitude direction is obtained from the received signal of the PS satellite and the relative velocity vector in the latitude direction is obtained from the received signal of the second GPS satellite, the current velocity vector of the vehicle is obtained by comparing both relative velocity vectors. As a result of the combination, the absolute value of the velocity vector and the absolute direction (θ) are calculated.

However, the orbit of an actual GPS satellite is
It differs depending on the type (number) of the GPS satellites, and as shown in FIG. 2B, the relative velocity vector in the longitude direction and the latitude direction cannot be obtained every time.

The gyro sensor 23 measures the relative rotation angle of the inertial body (flywheel, gas flow, optical fiber, etc.) housed in the housing with respect to the housing fixed to the vehicle body, and causes the arithmetic element 22 to operate. Output the measurement result. The arithmetic element 22 performs a synthesis process of the relative rotation angle measured by the gyro sensor 23 and the last acquired effective absolute direction, and outputs the advancing direction every moment.

That is, the last acquired effective absolute direction is added to the relative rotation angle measured by the gyro sensor 23 in the period from the time when the last acquired effective absolute direction is acquired to the present, The direction of travel.

Therefore, from the time when the last effective absolute direction is acquired to the time when the next effective absolute direction is acquired, the progress of the vehicle body changes corresponding to the driver's momentary steering state. For the direction, the output change of the gyro sensor 23 is exclusively picked up and rewritten.

The flowchart of FIG. 3 shows an arithmetic program in the arithmetic element 22 of FIG. 2 (a). In FIG. 3, in step 31, the received signal of the GPS receiver 21 is identified and it is determined whether or not the normal Doppler effect is required. Then, if the normal Doppler effect is obtained, the GPS satellite is specified and the vehicle relative speed to the ground is calculated in step 32. In step 33, the velocity vector is calculated through a combination calculation of a plurality of relative velocities, and the absolute value and the deviation angle (absolute direction) of the velocity vector are obtained.

In step 34, the absolute value of the speed vector is identified, and only when the absolute value of the speed vector exceeds the reference value, that is, when the ground speed of the vehicle body is a certain value or more, the steps 35 to 37 are executed. The correction operation is executed.

On the other hand, if the absolute value of the speed vector is less than the reference value, that is, if the ground speed of the vehicle body is less than a certain value, it is discriminated in step 39 whether or not the absolute direction is already stored. It Then, if the absolute direction is stored, the traveling direction is calculated by subtracting the change in the output of the gyro sensor 23 from the last rewritten and stored absolute direction, and the correction operation is executed in steps 35 to 37. In the same way as in the case of the above, the traveling direction is output in step 38.

On the other hand, if the normal Doppler effect is not detected in the GPS receiver after the start of traveling due to bad radio wave conditions, or if the predetermined speed cannot be reached due to traffic congestion, step 39 is NO. The program is repeated without tracing the traveling direction.

In this embodiment, the correction operation is cut off when the absolute value of the velocity vector is less than the reference value. However, regarding the accuracy of the absolute direction (ie, the velocity vector), a plurality of relative velocities are Since it is also important to obtain each accurately, the correction operation may be performed when at least two relative velocities are both equal to or more than a predetermined value.

Further, relative velocities are obtained for three or more GPS satellites, and a velocity vector is calculated by a combination of three types,
The correction operation may be executed only when the three velocity vectors are substantially equal.

Furthermore, in this embodiment, after the start of traveling, the GP
Until the normal Doppler speed is obtained from the S receiver and the traveling speed becomes equal to or higher than a certain speed, the traveling direction is not output. Therefore, for example, during this period, the absolute direction stored last time during the traveling is stored. May be used to perform the combining calculation in the traveling direction. Alternatively, a simple magnetic sensor may be combined to initially set a rough initial value.

[0039]

According to the traveling direction identification device of the first aspect,
It is possible to use a highly accurate absolute direction by measuring the Doppler effect of the signal transmitted by the GPS satellite. For example, even in the current state of the art, the absolute position detection error by GPS is 30 m or more, whereas the relative velocity detection error by measuring the Doppler effect of the GPS satellite signal is 0.1 m / sec. Therefore, for example, even at a low traveling speed of about 30 km / hour (8 m / sec), it is possible to identify the absolute direction with sufficient accuracy.

Further, since the correction operation of the traveling direction using the absolute direction is executed frequently and automatically, the traveling direction is not changed and the traveling direction of the vehicle on the navigation screen does not suddenly change. A person can trust these displays and concentrate on driving without paying attention to the correction operation of the traveling direction.

Further, unlike the magnetic sensor, there is no fear that the reliability of the absolute direction will be lost due to the disturbance of the earth's magnetism or the magnetization of the vehicle body, and the backward direction can be normally identified even when the vehicle body is backed up. .

By the way, in the traveling direction identification device using the conventional magnetic sensor, after starting the operation, it is necessary to trace the circle in a wide place and rotate the vehicle body by 360 degrees. Also,
It was necessary to capture the output of the backward light and the back gear sensor in order to judge the back running of the vehicle body. On the other hand, according to the traveling direction identification device of the first aspect, a wide space for tracing the circle is unnecessary, and it is not necessary to take in the output of the backward light or the back gear sensor.

According to the traveling direction identification device of claim 2, G
Since the traveling speed is determined from the output of the receiver of the signal transmitted from the PS satellite, it is not necessary to provide a special speed sensor.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of a traveling direction identification device according to an embodiment.

FIG. 3 is an explanatory diagram of a flowchart of an embodiment.

[Explanation of symbols]

 10 GPS Satellites 11 GPS Receivers 12 Velocity Vector Calculation Means 13 Relative Rotation Angle Detection Means 14 Correction Means

Claims (2)

[Claims] 1. A traveling direction identification device having a relative rotation angle detecting means (13) for measuring a relative rotation angle with respect to a vehicle body posture, comprising a GPS receiving means (11) for receiving radio waves transmitted from a GPS satellite (10). ) And a speed vector calculation means (12) for calculating a Doppler effect of a signal received by the GPS reception means (11) to obtain a speed vector of the vehicle body, and the relative rotation when the traveling speed is larger than a predetermined value. A traveling direction identification device, comprising: a correction means (14) for correcting the vehicle body traveling direction based on the output of the angle detection means (13) by replacing it with the direction of the velocity vector. 2. The traveling direction identification device according to claim 1,
When the absolute value of the speed vector calculated by the speed vector calculation means is larger than a predetermined value, the correction means sets the vehicle body traveling direction based on the output of the relative rotation angle detection means to the direction of the speed vector. An advancing direction identifying device, characterized in that it is a means for replacing and correcting.