JPH05322575A - Electronic azimuth meter - Google Patents

Abstract

PURPOSE:To accurately detect earth magnetism and an azimuth without being affected by hysteresis even when a magnetic detection means has a property generating hysteresis. CONSTITUTION:A magnetic detection part 2 is constituted by forming four reluctance elements MR1, MR2, MR3, MR4 on a substrate 20 in a bridge form and winding biasing coils CL1, CL2 around the substrate 20. A bias magnetic field turning the analogue switches AS1, AS2, AS3, AS4 of a switch part 30 ON/OFF to be reversed is applied to the biasing coil CL1 to measure earth magnetism. Thereafter, a bias current i1 is attenuated and vibrated by utilizing a condenser C1 to attenuate and vibrate the bias magnetic field to demagnetize the residual magnetism of the reluctance elements MR1, MR2, MR3, MR4. The bias magnetic field reversed in the same way by a switch part 40 is applied to the biasing coil CL2 to measure earth magnetism and, thereafter, an attenuated and vibrated bias magnetic field is applied to demagnetize the residual magnetism of the relutance elements MR1, MR2, MR3, MR4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic azimuth meter, and more particularly to an electronic azimuth meter which calculates an azimuth based on the strength of geomagnetism.

[0002]

2. Description of the Related Art Conventionally, in an electronic azimuth meter, a bias coil for applying a bias magnetic field is wound around a magnetic detecting means and inverted to this bias coil in order to accurately detect the earth's magnetism in a stable state. Supply current,
A method is known in which a bias magnetic field whose direction is reversed is applied to the magnetic detection means. In order to generate this bias magnetic field, for example, a MOS-FET (Meta
l Oxide Semi Conductor-Field Effect Transistor) is used to apply a constant voltage to the switching circuit, and the switching operation of this switching circuit causes the bias coil connected in series with the resistor to supply / stop the bias current and change the direction of the current. There is a method of performing inversion control. Thus, by applying the reverse bias magnetic field, it is possible to more accurately determine the direction of the geomagnetism.

[0003]

However, in such a conventional electronic azimuth meter, by applying a reverse bias magnetic field, the direction of the earth's magnetism is determined,
Although the azimuth can be calculated, the magnetic detection means itself is magnetized (residual magnetism) due to the influence of the magnetic hysteresis of the magnetic detection means used in the electronic azimuth meter, and the earth magnetism detection result becomes inaccurate. There was a problem that the direction could not be calculated accurately. For example, due to the hysteresis of the magnetic detection means, the magnitude of the output of the magnetic detection means differs depending on whether the electronic azimuth meter changes from the east direction to the north direction or from the west direction to the north direction. However, there was a problem that the direction could not be detected accurately. Therefore, an object of the present invention is to provide an electronic azimuth meter capable of detecting the magnitude of the earth's magnetism and calculating an accurate azimuth without the magnetic detection means being affected by hysteresis.

[0004]

In order to achieve the above object, an electronic azimuth meter according to the present invention comprises a magnetic detecting means for detecting the magnitude of a magnetic field and a bias magnetic field applying means for applying a bias magnetic field to the magnetic detecting means. Means, an azimuth calculating means for calculating an azimuth from the magnitude of the geomagnetism detected by the magnetism detecting means, and a bias magnetic field generated by the bias magnetic field applying means for eliminating the magnetism carried by the magnetism detecting means. It is characterized by including a bias magnetic field oscillating means for attenuating while vibrating.

[0005]

According to the present invention, the bias magnetic field oscillating means changes the bias magnetic field applied by the bias magnetic field applying means to the magnetism detecting means from positive to negative and from negative to positive while biasing the bias magnetic field. The magnitude of the magnetic field is reduced. Since the residual magnetism generated by the magnetic hysteresis increases as the external magnetic field increases, the residual magnetism carried by the magnetic detecting means gradually decreases by the operation of the bias magnetic field, and disappears as the magnitude of the bias magnetic field becomes zero. To do. By properly performing this operation, more accurate azimuth measurement can be performed without being affected by magnetic hysteresis.

[0006]

EXAMPLES The present invention will be specifically described below based on examples. 1 to 7 are views showing an embodiment of an electronic azimuth meter according to the present invention. FIG. 1 is a block configuration diagram of the electronic azimuth meter 1. The electronic azimuth meter 1 includes a magnetic detector 2,
A bias magnetic field control unit 3, an orientation calculation unit 4, a display unit 5 and the like are provided.

The magnetic detector 2 uses a so-called magnetoresistive element, and in a state where four magnetoresistive elements (magnetic detecting means) MR1, MR2, MR3, MR4 are connected on the substrate 20 in a bridge shape. Has been formed.

The magnetoresistive elements MR1, MR2, MR
3 and MR4, the magnetoresistive element MR1 and the magnetoresistive element MR3 are arranged in the same magnetic detection direction, and the magnetoresistive element MR2 and the magnetic resistance element MR4 are arranged in the same magnetic detection direction. In addition, the magnetic detection directions of the magnetic resistance elements MR1 and MR3 and the magnetic detection directions of the magnetic resistance elements MR2 and MR4 are arranged so as to differ by 90 degrees. The resistance value of each of the magnetoresistive elements MR1, MR2, MR3, and MR4 changes due to the action of magnetism.

Further, the substrate 20 has power supply terminals P1 and P
2 and output terminals S1 and S2 are formed. A constant voltage VC is applied to the power supply terminals P1 and P2, and the output terminals S1 and S2 are connected to the azimuth calculation unit 4.

The magnetoresistive elements MR1, MR2, MR
3, the bias coil CL1 and the bias coil CL2 (bias magnetic field applying means) are wound around the substrate 20 on which the MR4 is formed, and the bias magnetic fields generated by the bias coil CL1 and the bias coil CL2 are orthogonal to each other. It is being rolled around. As will be described later, the bias coil CL1 and the bias coil CL2 apply a bias magnetic field whose magnetic field direction is reversed to the magnetic detection unit 2 by a current supplied from the bias magnetic field control unit 3 while the magnetic field directions are reversed. A bias magnetic field that attenuates is applied.

The bias magnetic field control section 3 includes a switch section 30 for the bias coil CL1, a switch section 40 for the bias coil CL2, an operational amplifier OP, a resistor R and a control section 5.
0, etc., and the switch unit 30 has a bias coil C
The switch unit 40 is connected to L1 and the bias coil CL2.

A predetermined reference voltage VREF is input to the non-inverting input terminal of the operational amplifier OP, and the voltage between the magnetoresistive element and the resistor R is input to the inverting input terminal thereof. The output of the operational amplifier OP is connected to the switch unit 30 and the switch unit 40, and a constant current is supplied via the switch units 30 and 40 to the bias coil CL1.
Alternatively, it is supplied to the bias coil CL2.

The switch section 30 includes a capacitor C1, analog switches AS1, AS2, AS3, AS4, etc., and the capacitor C1 is connected in parallel to the bias coil CL1.

Each analog switch AS1, AS2, AS
3, the operation of AS4 is controlled by the control unit 50, and the control unit 50 controls the analog switches AS1 and AS4.
And analog switch AS2, AS3 paired on /
By controlling the off state, the direction of the bias current i1 flowing through the bias coil CL1 and its supply / stop are controlled.

That is, the analog switch AS1 and the analog switch AS2 are connected to the output terminal of the operational amplifier OP, and the analog switch AS3 and the analog switch AS4 are connected to the inverting input terminal of the operational amplifier OP.

Therefore, in the switch unit 30, when the analog switch AS1 and the analog switch AS4 are on, the bias current i1 flows in the positive direction of the X axis and the bias magnetic field is generated in the negative direction of the Y axis at the point of FIG. 1a. Also,
When the analog switch AS2 and the analog switch AS3 are turned on, the bias current i1 flows in the negative direction of the X-axis and the bias magnetic field is generated in the positive direction of the Y-axis at the point of FIG. 1a.

The capacitor C1 is a bias coil CL1.
When the supply of the bias current i1 to the bias coil CL1 is stopped, that is, when the analog switches AS1 to AS4 are all off, the supply of the bias current i1 to and from the bias coil CL1 is performed. A bias current i1 that is repeatedly accumulated and inverted and then attenuated is supplied to the bias coil CL1.

The switch section 40 includes a capacitor C2, analog switches AS5, AS6, AS7, AS8, etc., and the capacitor C2 is connected in parallel to the bias coil CL2.

Each analog switch AS5, AS6, AS
Similarly, the operation of 7, AS8 is controlled by the control unit 50, and the control unit 50 controls the operation of the analog switch AS.
5, AS8 and analog switches AS6, AS7 are paired to control ON / OFF to control the direction of the bias current i2 flowing in the bias coil CL2 and its supply / stop.

The output terminal of the operational amplifier OP is connected to the analog switch AS5 and the analog switch AS6, and the inverting input terminal of the operational amplifier OP is connected to the analog switches AS7 and AS8.

Therefore, in the switch section 40, when the analog switch AS5 and the analog switch AS8 are turned on, the bias current i2 flows in the Y-axis positive direction and the bias magnetic field is generated in the X-axis positive direction at the point of FIG. 1b. Also,
When the analog switch AS6 and the analog switch AS7 are turned on, the bias current i2 flows in the negative direction of the Y axis and the bias magnetic field is generated in the negative direction of the X axis at the point of FIG. 1b.

Since the capacitor C2 is connected in parallel with the bias coil CL2, the bias coil C2
When the supply of the bias current i2 to L2 is stopped, that is, when the analog switches AS5 to AS8 are all off, the supply and storage of the bias current i2 to the bias coil CL2 is repeated, and the bias current i2 is inverted and attenuated. Is supplied to the bias coil CL2.

The control unit 50 turns on / off the analog switches AS1, AS2, AS3 and AS4 of the switch unit 30.
Off and analog switch AS of the switch unit 40
5, ON / OFF of AS6, AS7, AS8 is controlled,
The supply / stop of the bias current i1 and the bias current i2 supplied to the bias coil CL1 and the bias coil CL2 is controlled, and the bias current i1 and the bias current i are utilized by using the capacitors C1 and C2.
Vibration and damping of 2.

The azimuth calculation section 4 comprises an amplification section 61, an A / D conversion section 62, a calculation section 63, etc.
It is connected to the output terminals S1 and S2 of the magnetic detector 2.

The amplification section 61 is composed of, for example, an operational amplifier, and amplifies the analog detection signal input from the output terminals S1 and S2 of the magnetic detection section 2 to generate the A / D conversion section 6.
Output to 2.

The A / D converter 62 converts the difference between the detection signals amplified by the amplifier 61 into a digital signal, and the calculator 6
Output to 3.

The calculation unit 63 calculates the azimuth based on the digital detection signal input from the A / D conversion unit 62,
The calculated azimuth is output to the display unit 5, and the display unit 5 displays and outputs the azimuth.

That is, the calculation unit 63 calculates the azimuth based on the detection signal when the bias magnetic field is applied by the bias coil CL1 and the bias coil CL2, and calculates as follows.

Now, the difference between the detection signals from S1 and S2 when the bias magnetic field in the Y-axis positive direction and the Y-axis negative direction of FIG. 1 is applied by the bias coil CL1 is Y1 and Y, respectively.
2 and S1 when a bias magnetic field in the X-axis positive direction and the X-axis negative direction of FIG. 1 is applied by the bias coil CL2,
When the difference between the detection signals from S2 is X1 and X2, respectively, the calculation unit 63 calculates the azimuth θ by the following equation. θ = tan ⁻¹ (Y1-Y2) / (X1-X2)

The display unit 5 is, for example, a liquid crystal display device or the like, and displays and outputs information necessary for the electronic azimuth meter 1, in particular, the azimuth in a predetermined display format.

Next, the operation will be described. Each magnetic resistance element MR1, MR2, MR3, MR4 of the electronic azimuth meter 1 has its resistance value when a magnetic field is not acting, as shown in FIG. Becomes maximum, and its resistance value gradually decreases as the magnetic field acts.

Here, as shown in FIG. 2, by applying the bias magnetic field B, the detection position is set on the characteristic curve having a large change, and whether the geomagnetism E is in the positive direction or the negative direction. , Are set so that they can be detected.

However, the magnetoresistive elements MR1, MR2,
MR3 and MR4 have a property of generating hysteresis, that is, a property of having a residual magnetism even when an external magnetic field is applied and the external magnetic field is gradually attenuated and disappeared. As shown in, the characteristic curve changes (in FIG. 3, the external magnetic field is slowly changed from positive to negative and from negative to positive).

With such a property that causes hysteresis, for example, as shown in FIG. 4, when the magnitude of the external magnetic field changes from X1 to X0, the magnetoresistive elements MR1, MR2, MR3, The resistance value of MR4 is R1, but when the magnitude of the external magnetic field changes from X2 to X0, the magnetoresistive elements MR1, MR2, MR3, MR
The resistance value of 4 is R2.

Therefore, even if the magnitude of the external magnetic field is the same, if the magnitude of the external magnetic field before the change is different, the resistance values of the magnetoresistive elements MR1, MR2, MR3, MR4 are different. As a result, in the azimuth meter having no means for avoiding the influence of this hysteresis, the magnetoresistive element MR
When the magnitude of the geomagnetism is detected by using 1, MR2, MR3, and MR4, different detection results are obtained for the same magnitude of the geomagnetism due to the previous orientation of the compass, due to the influence of hysteresis. Therefore, the magnitude of the geomagnetism cannot be detected accurately, and the azimuth cannot be calculated accurately.

Therefore, in this embodiment, the bias magnetic field B is applied to detect the magnitude of the earth's magnetism, and thereafter, the applied bias magnetic fields B are vibrated and attenuated so that the magnetoresistive elements MR1 and MR2. , MR3,
The residual magnetism of MR4 is erased and the effect of hysteresis is removed.

That is, as shown in FIG. 5, the control section 50 first turns on the analog switch AS3 of the switch section 30 and turns on the analog switch AS2 and the analog switch AS3 for a predetermined time. When the analog switch AS2 is turned on for a predetermined time, the bias current i1 in FIG. 1 flows in the negative direction of the X axis at the point a for a predetermined time, and the bias magnetic field B is generated in the positive direction of the Y axis for a predetermined time.

While the bias magnetic field B is being applied, the calculating unit 4 samples the detection signal input from the detecting unit 2 according to an instruction from the control unit 50.

After the bias magnetic field B is applied in the positive direction of the Y-axis for a predetermined time to detect the magnitude of the earth's magnetism, the analog switch AS2 is turned off as shown in FIG. When the analog switch AS2 is turned off, the supply of power to the bias coil CL1 is cut off and the bias coil CL1 is opened. At this time, as shown in FIG. 5, the bias current i1 is attenuated and oscillated by the bias coil CL1 and the capacitor C1 in accordance with the time constants of the bias coil CL1 and the capacitor C1, and the magnetic field generated in the bias coil CL1 is also shown in FIG.
As shown in, the vibration oscillates.

The magnetic field generated by the bias coil CL1 attenuates and vibrates, so that the magnetoresistive element MR1,
Demagnetize MR2, MR3, and MR4 as shown in FIG.
The external magnetic field can always be measured from the state where the magnetic field is zero.

When this bias current i1, that is, the damping oscillation of the bias magnetic field B is performed for a predetermined time, next, after turning on the analog switch AS4, the analog switch AS3 is turned off at a predetermined time interval, and the analog switch AS3 is turned off. The switch AS1 is turned on.

When the analog switch AS1 and the analog switch AS4 are turned on, the bias current i1 in FIG. 1 flows in the positive direction of the X axis at the point a for a predetermined time, and the bias magnetic field B is generated in the negative direction of the Y axis for a predetermined time.

While the bias magnetic field B is being applied, the calculating unit 4 similarly samples the detection signal input from the detecting unit 2 according to an instruction from the control unit 50.

After applying the bias magnetic field B in the negative direction of the Y-axis for a predetermined time, as shown in FIG.
Turn off. When the analog switch AS1 is turned off, the supply of power to the bias coil CL1 is cut off and the bias coil CL1 is opened. At this time, similarly, the bias current i1 is attenuated and oscillated by the bias coil CL1 and the capacitor C1, as shown in FIG.
The magnetic field generated in the magnetic field is also attenuated and vibrated as shown in FIG. 6 to demagnetize the magnetoresistive elements MR1, MR2, MR3 and MR4 as shown in FIG.

When this bias current i1, that is, the damping oscillation of the bias magnetic field B is performed for a predetermined time, the analog switch AS3 is turned on, and the application of the bias magnetic field by the bias coil CL1 and the measurement of the earth magnetism by the bias magnetic field are completed. To do.

Next, the application of the bias magnetic field by the bias coil CL2 and the measurement of the earth magnetism by the bias magnetic field are performed in the same manner. That is, after the measurement of the geomagnetism by the bias magnetic field of the bias coil CL1 is completed, the control unit 50 causes the analog switch AS6 and the analog switch AS7 of the switch unit 40 to operate for a predetermined time at predetermined intervals, as shown in FIG. turn on. When the analog switch AS6 and the analog switch AS7 are turned on for a predetermined time, the bias current i2 in FIG. 1 flows in the Y-axis negative direction at a point b for a predetermined time, and the bias magnetic field B is generated in the X-axis negative direction for a predetermined time.

While the bias magnetic field B is being applied, the calculation unit 4 samples the detection signal input from the detection unit 2 according to an instruction from the control unit 50.

After applying the bias magnetic field B in the negative direction of the X-axis for a predetermined time, as shown in FIG.
Turn off. When the analog switch AS6 is turned off, the supply of power to the bias coil CL2 is cut off and the bias coil CL2 is opened. At this time, similarly, as shown in FIG. 5, the bias current i2 is attenuated and oscillated by the bias coil CL2 and the capacitor C2 according to the time constants of the bias coil CL2 and the capacitor C2, and the magnetic field generated in the bias coil CL2 is also generated. , As shown in FIG.

The magnetic field generated by the bias coil CL2 attenuates and vibrates, so that the magnetoresistive element MR1,
MR2, MR3 and MR4 can be demagnetized as shown in FIG.

After the bias oscillation of the bias current i2, that is, the bias magnetic field B is performed for a predetermined time, the analog switch AS8 is turned on, and then the analog switch AS7 is turned off at a predetermined time interval. Turn on the switch AS5.

When the analog switch AS5 and the analog switch AS8 are turned on, the bias current i2 of FIG. 1 flows in the Y-axis positive direction at the point b for a predetermined time, and the bias magnetic field B is generated in the X-axis positive direction for a predetermined time.

While the bias magnetic field B is being applied, the calculation unit 4 similarly samples the detection signal input from the detection unit 2 according to an instruction from the control unit 50.

After applying the bias magnetic field B in the positive direction of the X-axis for a predetermined time, as shown in FIG.
Turn off. When the analog switch AS5 is turned off, the supply of power to the bias coil CL2 is cut off and the bias coil CL2 is opened. At this time, similarly, the bias current i2 is attenuated and oscillated by the bias coil CL2 and the capacitor C2 as shown in FIG.
The magnetic field generated in the
The magnetoresistive elements MR1, MR2, MR3, MR4 can be demagnetized as shown in FIG.

After the bias oscillation of the bias current i2, that is, the bias magnetic field B is performed for a predetermined time, the analog switch AS7 is turned on, and the bias magnetic field is applied by the bias coil CL2 and the geomagnetism is measured by the bias magnetic field. To do.

By the above operation, the potential differences X1, Y1, X2, Y2 of S1 and S2 at the time of applying the bias magnetic field in each direction can be detected. Therefore, the arithmetic unit 63 calculates the azimuth by the instruction of the control unit 50, and the display unit displays. 5 displays this.

Thereafter, the above processing is repeated to measure the azimuth in each case. As described above, since the demagnetization is performed every time the geomagnetism is detected and the magnitude of the geomagnetism can be detected from the state where the magnetic field is zero, the azimuth can be measured without the influence of the magnetic hysteresis.

The structure of this embodiment is merely an example, and the present invention is not limited to the method of connecting the magnetoresistive element, the method of applying the bias magnetic field, the method of calculating the azimuth, and the like.

The magnetic detecting means is not limited to the magnetoresistive element, and the present invention can be applied to the magnetic detecting means as long as it is easily affected by hysteresis.

[0059]

According to the present invention, the bias magnetic field vibrating means vibrates and attenuates the bias magnetic field applied by the bias magnetic field applying means to the magnetic detecting means, thereby reducing the residual magnetism of the magnetic detecting means. Since it can be demagnetized, it is possible to provide an electronic azimuth meter that can obtain an accurate measurement value with a simple configuration even if a magnetic detection means that is easily affected by hysteresis is used.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electronic azimuth meter according to an embodiment of the present invention.

FIG. 2 is a diagram showing an output characteristic of a magnetoresistive element in which an influence of hysteresis is ignored.

FIG. 3 is a diagram showing output characteristics of a magnetoresistive element when the influence of hysteresis is taken into consideration.

FIG. 4 is an explanatory diagram of a state in which a geomagnetic detection error occurs when the magnetoresistive element has hysteresis.

FIG. 5 is a diagram for explaining the operation of the electronic compass.

FIG. 6 is a diagram showing changes in a bias magnetic field applied during a degaussing period of a magnetoresistive element.

FIG. 7 is a diagram showing changes in output characteristics of a magnetoresistive element during a degaussing period.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electronic azimuth meter 2 Magnetic detection part 3 Bias magnetic field control part 4 Direction calculation part 5 Display part 30, 40 Switch part 50 Control part 61 Amplification part 62 A / D conversion part 63 Calculation part OP operational amplifier R resistance MR1, MR2, MR3 , MR4 Magnetoresistive element CL1, CL2 Bias coil AS1, AS2, AS3, AS4, AS1, AS2, A
S3, AS4 Analog switch i1, i2 Bias current C1, C2 Capacitor

Claims (1)

[Claims] 1. A magnetic detection means for detecting the magnitude of a magnetic field, a bias magnetic field applying means for applying a bias magnetic field to the magnetic detection means, and an azimuth for calculating an azimuth from the magnitude of the geomagnetism detected by the magnetic detection means. An electronic device comprising: a calculating unit; and a bias magnetic field oscillating unit that vibrates and attenuates the bias magnetic field generated by the bias magnetic field applying unit in order to eliminate the magnetism carried by the magnetic field detecting unit. Type compass.