JPS6246809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the difference between the azimuth signal value detected at a predetermined period and the azimuth signal value detected a certain period before, and determines the azimuth to be displayed based on this difference. The present invention relates to a vehicle direction meter that ensures prevention of erroneous display of direction.

BACKGROUND ART Conventionally, it has been considered to mount a compass on a vehicle so that the driver of the vehicle can know the direction in which the vehicle is traveling, and recently electronic compass has been proposed. First, the principle of the direction sensor of an electronic direction meter will be explained with reference to FIG. The X coil 2 and the Y coil 3 are wound so as to be orthogonal to each other. When the earth's magnetism H exists, electromotive forces _V X and V _Y proportional to the X-axis and Y-axis components of the earth's magnetism H are induced in the X coil 2 and the Y coil 3, respectively. The processing circuit 4 vector-composes the electromotive forces V _X and V _Y and outputs the angle θ of the coil with respect to magnetic north as azimuth data.

By the way, on the ground, local geomagnetic disturbances occur due to structures containing reinforcing bars (iron bridges, buildings, etc.), railway tracks and power transmission lines carrying large currents (hereinafter referred to as "disturbances"). call). When a vehicle equipped with a direction meter passes through a place where such disturbances occur, the direction of the vehicle is affected by such disturbances, so the following operations have been conventionally performed to remove the effects of the disturbances. In other words, if A _o is the azimuth data that is captured at a certain time of the azimuth data that will be incorporated next at a fixed time interval, A _{o -1} is the azimuth data that is captured a certain time before that, and K is a constant, then |A _o -A
_o-1 | When ≦K, the direction is displayed based on the direction data A _o , assuming that there is no influence from disturbance, but |
When A _o −A _o-1 |>K, A _o is regarded as abnormal data affected by disturbance, and the azimuth is displayed based on the azimuth data A _o-1 captured a certain time before.

In this way, erroneous display due to disturbance can be prevented, but since the constant K is constant, there is a limit to the accuracy of direction display. In other words, if the constant K is set too large, abnormalities in the heading data due to small disturbances will not be detected and the abnormal heading will be displayed as is.If the constant K is set too small, the heading will be displayed even though the vehicle's direction has actually changed. There is a problem in that changes are mistakenly judged as changes due to external disturbances.

The present invention focuses on the fact that the angle at which a vehicle can change its running direction during a certain period of time is determined by the vehicle speed. In a device that detects the difference between the direction signal value and the direction signal value and decides which direction signal value should be displayed based on this difference, the difference is calculated as a predetermined function of the vehicle speed in order to ensure that the direction is not displayed incorrectly. It was designed to change.

The present invention will be explained below based on the drawings.

FIG. 2 shows an embodiment of the compass circuit according to the present invention, where 5 is a compass having a compass sensor as shown in FIG. 1, 6 is a memory for storing the previously captured compass data, 7 is a comparator that compares the currently captured data with the previously captured data; 8
is a comparison data generator, which consists of a distance sensor 81 that generates a pulse every time the vehicle travels a certain distance, a distance-vehicle speed converter 82, and a function generator 83 that generates comparison data determined by the vehicle speed. .
Reference numeral 9 denotes an oscillator whose output signal becomes a time reference signal for the distance-vehicle speed converter 82, and is divided by a divider 10 for the comparator 7 to become an azimuth data acquisition signal S.

Now, in the above circuit, the pulse signal from the distance sensor 81 is sent to the distance-vehicle speed converter 82, where the period between the pulses is measured using the signal from the oscillator 9 as a time reference signal, and the period between the pulses is measured as speed data to the function generator 8.
Sent to 3. The function generator 83 generates, as comparison data, an angle θ that can change during the generation interval t of the data acquisition signal S, which is determined by the vehicle speed and the turning performance of the vehicle. That is, t: Data acquisition signal generation interval (seconds) v: Vehicle speed (m/second) θ: Maximum rotation angle (radians) at which the vehicle can turn at that speed r: Minimum turning radius r _n at vehicle speed v
_io : Minimum turning radius of the vehicle, G: Maximum centrifugal force that the vehicle can withstand when turning at vehicle speed v, then v ² /r=G, vt=rθ and r≧r _nio , For V<√ _nio , θ=vt/r _nio …(1), V
≧√ Gr _nio can be expressed as θ=G・t/v…(2). The relationship between the rotation angle θ of the vehicle and the minimum rotation radius r at the vehicle speed v is as shown in FIG.
The result will be as shown in the figure. Therefore, the function generator 83 outputs θ determined by either of the above equations (1) or (2) for the vehicle speed v as comparison data. In a place where there is no disturbance, the previous orientation data B stored in the memory 6 and the current orientation data A are B-θ<A<
Since the condition B+θ is satisfied, the current orientation data A is output as the true value, and the orientation data A is also stored in the memory 6.

Next, if we consider the case where the vehicle travels in a place where there is a large disturbance such as under a guard or at a railroad crossing, the current azimuth data A changes significantly due to the influence of this disturbance, and the condition of B-θ<A<B+θ is satisfied. Not satisfied. Therefore, the comparator 7 outputs the previous normal azimuth data B as is, and considers the current azimuth data A to be abnormal and ignores it.

Next, a case where the above-mentioned direction meter is applied to a vehicle position detection device will be described.

As shown in Fig. 5, the principle of position detection is as follows: If the minute distance traveled while the azimuth data capture signal S is generated is dl, and the azimuth at that time is θ, then the coordinates of the current position P at that time (x, y) is expressed as x=x ₀ +sin θ·dl where the coordinates of the starting point Q y=y ₀ +cos θ·dl are (x ₀ , y ₀ ). In other words, the coordinates (x, y) of the current position P are determined by dividing the distance traveled while the data acquisition signal S was generated into X and Y axes (east-west, north-south) components and integrating them, and then the coordinates (x, y) of the starting point Q. ₀ , _y0 )
It is found by adding to .

If there is an error in θ due to disturbance when the data acquisition signal S is generated, it will appear as an error in the travel distance on the X and Y axes. As the distance traveled increases, the number of times the azimuth data is captured also increases, resulting in
The absolute value of the error in the traveling distance of the Y-axis component also increases, and the coordinates of the current position P cannot be accurately determined. If the comparison data is a fixed value, no matter how large or small the comparison data is, it will not be possible to accurately grasp the geomagnetic anomaly, and this will cause an error in θ, making the calculation of the current position inaccurate. By adopting a vehicle speed response type, geomagnetic anomalies can be grasped more accurately, and the calculation result of the current position can be made even more accurate.

In the above example, the data acquisition signal is generated by the oscillator at regular intervals, but the same effect can be obtained even if the distance pulse is generated every n (n is an integer) distance pulses. Further, the compass does not need to be electronic, and may be of a type that optically reads the needle position of a magnetic compass.

As explained above, in the present invention, since the comparison data θ is a variable value depending on the vehicle speed, it is possible to detect abnormalities in the earth's magnetic field more accurately. In other words, if the comparative data θ is set to a fixed value and is increased, it will be regarded as a normal value in the case of a slight abnormality, and if the comparative data θ is decreased, the vehicle will turn at a slower speed and change its direction. The present invention can prevent such changes from being regarded as abnormal due to disturbances, leading to erroneous judgments, and enables more accurate orientation detection. Furthermore, when detecting the position of a vehicle using the compass according to the present invention, the current position is determined by integrating the travel distance from the starting point in the east-west and north-south directions. The present invention is particularly effective because it is integrated as a north-south travel distance.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the direction sensor, Figure 2 is a block diagram of the direction meter according to the present invention, Figure 3 is an illustration of the function generator, Figure 5 is a diagram of the principle of position detection, and Figure 4 is a diagram of the principle of position detection. FIG. 3 is a relationship diagram showing the relationship between vehicle speed v and azimuth θ using the data acquisition signal generation interval t as a parameter. 1...Ferromagnetic material, 2...X coil, 3...Y coil,
4... Processing circuit, 5... Direction meter, 6... Memory, 7... Comparator, 8... Comparison data generator, 9... Oscillator, 10
...Divider, 81...Distance sensor, 82...Distance-vehicle speed converter, 83...Function generator.

Claims (1)

[Claims] 1. Geomagnetic detection means for detecting the direction of geomagnetism and outputting direction data, storage means for storing the direction data, direction data stored in the storage means and direction data outputted from the geomagnetism detection means after a predetermined period of time. Comparison means for comparing the difference between the azimuth data and outputting the azimuth data stored in the storage means when the difference between the azimuth data is larger than a predetermined value, and outputting the azimuth data output after the predetermined time when it is smaller than the predetermined value. and a display section that displays the direction based on the direction data output from the comparison means, the predetermined value is determined by the maximum rotation that can change within the predetermined time determined by the vehicle speed and the turning performance of the vehicle. A vehicle compass that is characterized in that it changes depending on the corner.