JPH0371011A - Azimuth correction data storage system in electronic compass - Google Patents

Abstract

PURPOSE:To eliminate the trouble some operation to store new correction data every time a battery is replaced by storing a nonvolatile memory with correction data for erasing a disturbing magnetic field which causes a measurement error to the detection signal of an earth magnetism sensor. CONSTITUTION:This system is equipped with the earth magnetism sensor 1 which detects the azimuth of the earth magnetism, an azimuth signal amplifying circuit 8 which amplifies an azimuth signal outputted by the sensor 1 and converts it into a digital signal, a correcting signal calculating means which finds the correction data for disturbing magnetic field erasure to the azimuth signal from the circuit 8, a compensating circuit 20 which converts the correction data into an analog signal and outputs the analog signal to the sensor 1, and the nonvolatile memory 25. Then the signal of the earth magnetism azimuth detected by the sensor 1 is supplied to the correcting signal calculating means and found data is stored in the memory 25; and the correction data is read out of the memory 25 in measurement mode and supplied to the sensor 1 to erase the disturbing magnetic field.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides correction data for erasing interfering magnetic fields that cause measurement errors with respect to geomagnetic direction signals from an electronic compass for detecting the direction of a vehicle, such as an automobile. Regarding the storage method.

[Conventional technology]

Modern cars are equipped with electronic compasses to help drivers know which direction the car is heading in unfamiliar areas.

This type of electronic compass is equipped with a detection coil that is perpendicular to the radial direction of an annular core that is excited by an excitation signal source. Using a double-frequency magnetic sensor that outputs double-frequency pulses, the detection signal from this sensor is processed and input to a display device installed on the driver's cab panel, which displays the direction of travel of the vehicle in relation to the geomagnetic direction. That's what I do.

By the way, since the car body is made of ferromagnetic material, the car body itself becomes magnetized during manufacturing processes such as sheet metal and explosion welding, or when passing near factories, railroad crossings, etc., and the residual magnetism caused by this becomes magnetized. Acts as a disturbing magnetic field on the earth's magnetic field,
This will give a measurement error. To eliminate interfering magnetic fields,
Turn the car once or several times in the same direction as the clockwise direction,
The detection signal from the geomagnetic sensor at this time is input to a microcomputer installed in the car, and correction data in, for example, 16 directions is calculated, and the data is stored in advance in the computer's built-in memory consisting of capacitors and transistors, or the memory using flip-flops. This is stored, read out during the geomagnetic direction measurement mode, and applied to the detection coil of the geomagnetic sensor to eliminate the interfering magnetic field.

[Problem to be solved by the invention]

The correction data used in the above-mentioned device is stored in a memory that always requires backup by the voltage supply from the on-board battery, so when the voltage supply is cut off when the battery is replaced, the stored correction data is lost. It disappears in an instant. Therefore, each time a battery is installed, it is necessary to turn the vehicle and re-memorize the correction data, which is a cumbersome operation, and also requires the installation of a battery backup circuit.

This invention was made in view of the above-mentioned problems, and its purpose is to eliminate the need for re-storing correction data each time the battery is replaced, and to eliminate the need for a battery backup circuit. An object of the present invention is to provide a new direction correction data storage method for an electronic compass.

[Means for solving problems]

The azimuth correction data storage method in the electronic compass of the present invention includes a geomagnetic sensor that detects the geomagnetic azimuth, an azimuth signal amplification circuit that amplifies the azimuth signal output from the geomagnetic sensor and converts it into a digital signal, and an azimuth signal amplification circuit that a correction signal calculation means for obtaining correction data for canceling a disturbing magnetic field with respect to an azimuth signal from the azimuth signal; a compensation circuit that converts the correction data sent from the correction signal calculation means into an analog signal and outputs it to the geomagnetic sensor; and a correction signal calculation means. The present invention is characterized in that it includes a nonvolatile memory in which the obtained correction data is written and read.

[For production]

The geomagnetic azimuth signal detected from the geomagnetic sensor is applied to the correction signal calculation means via the azimuth signal amplification circuit, the correction data obtained by this means is stored in a non-volatile memory, and the correction data is read from the non-volatile memory in the measurement mode. In addition to the geomagnetic sensor, it also eliminates interfering magnetic fields.

〔Example〕

Embodiments of the system of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the circuit i component of one embodiment of the system of the present invention, in which reference numeral (1) is attached to an annular core (2), and detection windings (3), (4) orthogonal to the radial direction of the annular core (2). ) and excitation circuit〈
This is a known double frequency type magnetic sensor formed by winding an excitation winding (5) connected to an oscillator <6> via a coil (8).
is an azimuth signal amplification circuit that separately converts the horizontal and vertical component detection signals U and V of the geomagnetic azimuth signal detected by the detection windings (3) and <4) into digital signals;
From the vertical component detection signals U and V, the frequency of the oscillator (6) is
A bandpass filter (9) that detects the filtrate at twice the frequency, (1
4), an AC amplifier (10) for amplifying the filtered signal, (
15) and this output signal to a rectifier (11), (16)
DC amplifier (12
), (17), and AD converters (13), (18) that convert this DC level signal into digital quantities. (19) is a microcomputer which, in the correction data storage mode, rotates the car once or several times in the same direction as the clockwise direction and reads the digital signal indicating the geomagnetic direction from the direction signal amplification circuit (8) as shown in FIG. As shown, the vehicle body magnetization vector F1. which acts as a disturbing magnetic field. The erroneous geomagnetic azimuth vector H8 having a phase difference θ8 formed by In order to correct it so that it becomes, correction data Hg (V), -11 which generates a compensation magnetic field -■8 which cancels the vehicle body magnetization vector H,
. The compensation circuit (20) is configured to transmit correction data 11g (V
)H, (Ll) are converted into analog signals by DA converters (21), (23), and buffer amplifiers (22), (2
4) Compensation current rgm obtained via 1. (U) is input to the detection coils (3) and (4).

The reference numeral (26) indicates a display unit that indicates the direction of travel of the vehicle in relation to the geomagnetic direction, and the reference numeral (27) indicates a power supply circuit for a microcomputer (19) connected to an ignition (IG) switch (not shown). be.

To explain the operation of the device configured in this way, in the correction data storage mode, the vehicle is turned once or several times in the same direction as the clockwise direction, and the vehicle body magnetization vector Hg from the geomagnetic sensor (]) does not reach the geomagnetic direction. The vector L is detected and input to the microcomputer (19) via the azimuth signal amplification circuit 1i'8 (8), and a correction vector component forming a compensation magnetic field 113 for erasing the vehicle body magnetization vector 118 is generated.
〇, (U), -H, and (V) are calculated for, for example, 16 directions, and these are stored in the nonvolatile memory (25). Since the non-volatile memory (25) retains the stored data even if the power supply is lost, the correction data continues to be stored even if the microcomputer (19) goes into a no-voltage state when replacing the battery. Therefore, there is no need to store the correction data again after replacing the battery, and in the measurement mode, the correction data is immediately read out from the non-volatile memory (25) and the compensation current 1.(U) is transmitted through the compensation circuit (20). , l5 (V) as a magnetic sensor (1
) is input to the detection coils (3) and (4), and the vehicle body magnetization patterns 1 to 11 are input. The geomagnetic vector H without error is obtained by erasing
8 is displayed on the display section (26).

〔Effect of the invention〕

As described above, according to the present invention, the correction data for erasing the interfering magnetic field that causes measurement errors in the signals detected from the geomagnetic sensor is stored in the non-volatile memory, so each time the battery is replaced, The more it is possible to omit the troublesome operation of storing new correction data, the more effective it is to have a parts battery backup and to simplify the configuration of the device's energizing power supply circuit. be.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a circuit diagram of one embodiment of the system of the present invention, and Fig. 2 is a circuit diagram of an embodiment of the system of the present invention.
The figure is a vector diagram showing the relationship between the geomagnetic vector, the vehicle body magnetization vector that gives a measurement error to the geomagnetic vector, and the compensation magnetic field vector. In the drawing (1)...geomagnetic sensor, (3), (4)...detection coil, (5)...excitation coil, (8)...azimuth signal amplification circuit, (19)...microcomputer, (20)... 〉・
Compensation circuit, (25>... non-volatile memory.

Claims (1)

[Scope of Claims] A geomagnetic sensor that detects the geomagnetic direction; a direction signal amplification circuit that amplifies the direction signal output from the geomagnetic sensor and converts it into a digital signal; and a direction signal output from the direction signal amplification circuit. a correction signal calculation means for obtaining correction data for the interference magnetic field cancellation method; a compensation circuit for converting the correction data sent from the correction signal calculation means into an analog signal and outputting it to the geomagnetic sensor; An azimuth correction data storage method in an electronic compass that includes a nonvolatile memory for writing and reading correction data.