JPH10288523A - Moving body azimuth detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the influence of disturbance and reduce the accumulation of errors by composing the geomagnetic azimuth from a geomagnetic azimuth detecting means with the rotating angle from a rotating angle detecting means in a frequency area to determine the azimuth of a moving body. SOLUTION: This moving body azimuth detector has a geomagnetic sensor 1 constituting geomagnetic azimuth detecting means, an optical fiber gyro (angle speed sensor) 2 constituting rotating angle detecting means, and a computer 3 constituting azimuth composing means. The computer 3 combines the change portions in a fixed time of the azimuth and angle by the respective sensor in a frequency area when the azimuth of a moving body is calculated. At this time, the rotating angle and the geomagnetic azimuth are differently weighted depending on frequency, respectively, such that the angle sensor 2 is weighted in high frequency area, and the geomagnetic sensor 1 is weighted in low frequency area, and outputs the resulting combined value as the azimuth of the moving body. Further, the computer 3 has also the function of changing this ratio of weighting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving body direction detecting apparatus using both a direction based on geomagnetism detection and a rotation angle based on rotational angular velocity detection, and in particular, a moving body direction with less influence of disturbance and less error accumulation. The present invention relates to a detection device.

[0002]

2. Description of the Related Art Conventionally, a geomagnetic sensor that outputs geomagnetic components in the front-rear direction and the left-right direction of a vehicle body has been used as a compass or a moving body direction detecting device used for displaying a traveling locus for a vehicle or a vehicle. There is a sensor that combines a geomagnetic sensor with an angular velocity sensor that is not affected by geomagnetism.

[0003] As an example of the latter, a change in the geomagnetic azimuth (absolute azimuth) generated within a fixed time and a change in the angle similarly obtained from the angular velocity sensor are compared with respective judgment values obtained by experiments. Some of them determine which change is to be adopted.

[0004]

The method using only the geomagnetic sensor calculates the absolute azimuth from the detected geomagnetism,
The azimuth of the traveling direction of the vehicle body is obtained.However, it is susceptible to the disturbance magnetic field generated when passing a railroad crossing, a bridge, or when a nearby magnetized truck travels. This causes an error in the detected orientation.

In a system in which a terrestrial magnetism sensor and an angular velocity sensor are combined, and the change in the azimuth of each sensor is compared with a determination value, when the vehicle travels on a locus such as a sharp curve with a sharp angle change, the angular velocity sensor is used. Errors accumulate.

[0006] In a system in which a geomagnetic sensor and an angular velocity sensor are combined, if the angular velocity sensor drifts, errors accumulate over time. For this reason,
For long-term operation, a low-drift angular velocity sensor is required, and a low-drift angular velocity sensor is expensive.
It is not practical in terms of cost.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a moving body direction detecting device which is less affected by disturbance and has less accumulated errors.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a rotational angle detecting means for measuring a rotational angular velocity of a moving body by an angular velocity sensor and integrating the rotational angular velocity with time to obtain a rotational angle. A geomagnetic azimuth detecting means for detecting the traveling direction of the moving object by a geomagnetic sensor, and an azimuth synthesizing means for synthesizing the geomagnetic azimuth and the rotation angle in the frequency domain to obtain the azimuth of the moving object.

The azimuth combining means may combine the rotation angle and the geomagnetic azimuth with different weights depending on frequencies.

[0010]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, a moving body direction detecting device according to the present invention includes a geomagnetic sensor 1 constituting geomagnetic direction detecting means, an optical fiber gyro (angular velocity sensor) 2 forming rotational angle detecting means, and The computer includes a computer 3 constituting the azimuth synthesizing means and a display 4 for displaying a result.

When calculating the azimuth of the moving object, the computer 3
Changes in the azimuth and angle of each sensor over a certain period of time are combined in the frequency domain. At this time, different weights are assigned to the rotation angle and the geomagnetic azimuth depending on the frequency so that the angular velocity sensor 2 is weighted in the high frequency region and the geomagnetic sensor 1 is weighted in the low frequency region.
The combined value is output as the direction of the moving object. Further, the computer 3 has a function of changing the weighting ratio. For example, when the disturbance of the geomagnetism is detected, the weight to the rotation angle is increased to reduce the error from the true azimuth.

The calculation of the azimuth of the moving object by the coupling between the rotation angle and the geomagnetic azimuth in the frequency domain is performed according to the following procedure.

(1) Data is collected from the geomagnetic sensor 1 and the angular velocity sensor 2 at a certain time interval ΔT. The azimuth is calculated from the terrestrial magnetism data, and this is set as the terrestrial magnetism azimuth θ _Mi. The angular velocity data is integrated and converted into an angle, which is defined as a rotation angle θ _Gi . Where the subscript i (i = 0, 1, 2,
・ ・) Are numbers assigned in the order of data collection.

(2) The low frequency component θ _Mi ^(L) of the geomagnetic azimuth is calculated by the following equation.

Θ _Mi ^(L) = k × θ _Mi + (1−k) × θ _Mi−1 ^(L) where k is a coefficient, which is calculated by the following equation.

K = (2πf _C ΔT) / (1 + πf _C ΔT) Here, f _C is a predetermined cutoff frequency. However, the computer 3 can change the cutoff frequency f _C. If the cutoff frequency f _C is high, the geomagnetic sensor 1
The weight of the angular velocity sensor 2 increases when the weight of the angular velocity sensor 2 increases.

(3) The low frequency component θ _Gi ^(L) of the rotation angle is calculated by the following equation.

Θ _Gi ^(L) = k × θ _Gi + (1−k) × θ _Gi-1 ^(L) (4) The high frequency component θ _Gi ^(H) of the rotation angle is calculated by the following equation.

Θ _Gi ^(H) = θ _Gi −θ _Gi ^(L) (5) The direction θ _{Si of the} moving object is calculated by the following equation.

Θ _Si = θ _Mi ^(L) + θ _Gi ^{(H) When} the moving body direction detecting device is started (i = 0), initialization is performed as follows.

Θ _Mi ^(L) = θ _Mi θ _Gi ^(L) = 0 FIG. 2 shows the frequency characteristics of the output obtained by the above-described synthesis formula. The horizontal axis represents frequency, and the vertical axis represents gain (weight).
Represents As shown, the weight of the geomagnetic sensor 1 is large in the low frequency region, and the area surrounded by the characteristic curve 21 of the magnetic sensor is large. In the high frequency region, the weight of the angular velocity sensor 2 is large, and the area surrounded by the characteristic curve 22 of the angular velocity sensor is large. These two areas are separated by a certain frequency in the figure. This frequency is the cutoff frequency f _C
It is. When the cutoff frequency f _C is high, the area surrounded by the characteristic curve 21 of the magnetic sensor increases, and therefore, the weight of the geomagnetic sensor in the output increases. When the cutoff frequency f _C is low, the area surrounded by the characteristic curve 22 of the angular velocity sensor increases, and therefore, the weight of the angular velocity sensor in the output increases.

FIG. 3 shows a flow of the operation of the moving body direction detecting apparatus of the present invention. The operation will be described below.

(1) Initial setting is performed. That is, the first azimuth of the magnetic sensor 1 (geomagnetic azimuth) and the angle of the angular velocity sensor 2 (rotation angle) are read, and the first terrestrial magnetic azimuth is substituted for the output azimuth θ _S0 .

(2) Wait for ΔT seconds.

(3) Geomagnetic orientation θ _Mi after waiting for ΔT seconds
And the rotation angle θ _Gi are read into the computer 3.

(4) Change Δθ in geomagnetic azimuth during ΔT seconds
Calculate _M.

(5) Change Δθ _{G in} rotation angle during ΔT seconds
Is calculated.

(6) By taking the absolute difference between Δθ _M and Δθ _G ,
This value is compared with a threshold value A (for example, 0.5 degrees).
If the absolute difference is larger than the threshold value A, it is determined that the geomagnetism is disturbed. Based on this determination, the cutoff frequency f _C
And the weight of the geomagnetic sensor is reduced.

(7) Geomagnetic Direction θ _Mi and Previous Output Direction θ
The absolute difference from _Si-1 is obtained, and this value is compared with a threshold value B (for example, 1.0 degree). If the absolute difference is larger than the threshold value B, it is determined that the vehicle is rotating. Based on this determination, the cutoff frequency f _C is lowered, and the weight of the angular velocity sensor with high rotation angle detection accuracy is increased.

(8) The terrestrial magnetic orientation θ _Mi and the rotation angle θ _Gi are synthesized using the cutoff frequency f _C determined from the above, and this is set as the current output orientation θ _Si .

(9) Output the output orientation θ _Si to the display.
Thereafter, the following (3) is repeated.

In this embodiment, an optical fiber gyro is used as the angular velocity sensor. However, instead of such an optical angular velocity sensor, a mechanical angular velocity sensor (mechanical gyro,
A vibration gyro may be used.

By mounting the moving body direction detecting device of the present invention on a vehicle, it is possible to realize a car navigation or a car location which is not affected by disturbance of geomagnetism.

[0035]

The present invention exhibits the following excellent effects.

(1) When mounted on a vehicle and used for displaying a traveling locus, errors are unlikely to occur even when approaching a railroad crossing or other magnetized magnetic material.

(2) Even if an error occurs in the angular velocity sensor due to running on a curve or the like, the output azimuth gradually converges due to the geomagnetic azimuth, and the error of the angular velocity sensor does not accumulate in the output azimuth.

(3) Since the angular velocity sensor does not need to have a low drift, a relatively inexpensive angular velocity sensor can be used, which is cost effective.

[Brief description of the drawings]

FIG. 1 is a block diagram of a moving body direction detecting apparatus according to an embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram in the synthesis in the frequency domain according to the present invention.

FIG. 3 is a flowchart of the operation of the moving body direction detecting device of the present invention.

[Explanation of symbols]

 1 geomagnetic sensor 2 angular velocity sensor 3 computer

Claims (2)

[Claims] An angular velocity sensor measures a rotational angular velocity of a moving body, integrates the rotational angular velocity with time to determine a rotational angle, and a geomagnetic azimuth detection that detects a traveling direction of the moving body by a geomagnetic sensor. And a azimuth synthesizing means for synthesizing the terrestrial magnetic azimuth and the rotation angle in a frequency domain to obtain an azimuth of the mobile body. 2. The moving body direction detecting device according to claim 1, wherein the direction synthesizing unit combines the rotation angle and the geomagnetic direction with different weights depending on frequencies.