WO2023026470A1 - Magnetic field sensor and magnetic field detection method - Google Patents

Abstract

Provided is a magnetic field sensor that does not have temperature dependency.　This magnetic field sensor comprises: a single two-dimensional oscillator which is driven by a drive signal corresponding to a first rotary oscillation mode and a drive signal corresponding to a second rotary oscillation mode, and to which a first current signal corresponding to the first rotary oscillation mode and a second current signal corresponding to the second rotary oscillation mode are input; and a magnetic field detecting unit which outputs a first resonance frequency and a second resonance frequency corresponding to the first rotary oscillation mode on the basis of a signal output from the two-dimensional oscillator, and detects a magnetic field on the basis of the first resonance frequency and the second resonance frequency.

Description

Magnetic field sensor and magnetic field detection method

The present invention relates to a magnetic field sensor and a magnetic field detection method, for example, a magnetic field sensor and a magnetic field using a gyro device having a single (one) mode-matched two-dimensional vibrator (resonance frequencies of two orthogonal axes match). It relates to a detection method.

Conventionally, magnetic field sensors (also called magnetic sensors, etc.) have been proposed for detecting the magnitude and direction of magnetic fields. For example, Patent Document 1 below discloses a magnetic field sensor using a semiconductor element such as a Hall sensor.

Japanese Patent Publication No. 2016-510116

A magnetic field sensor using a semiconductor element such as a Hall sensor, as described in Patent Document 1, has temperature dependence and is not robust against temperature changes. Therefore, there is a possibility that the measurement accuracy of the magnetic field deteriorates due to the change in temperature. Therefore, a magnetic field sensor that is robust against changes in temperature is desired.

One of the purposes of the present invention is to provide a new and useful magnetic field sensor and magnetic field detection method for solving these problems.

One aspect of the present invention is
It is driven by a drive signal corresponding to a first rotational vibration mode and a drive signal corresponding to a second rotational vibration mode, and is further driven by a first current signal corresponding to the first rotational vibration mode and a second rotational vibration mode corresponding to the second rotational vibration mode. a single two-dimensional oscillator to which a current signal is input;
a first detector that detects the amplitude and phase of a component corresponding to a first rotational vibration mode from the signal output from the two-dimensional vibrator;
a second detector that detects the amplitude and phase of a component corresponding to the second rotational vibration mode from the signal output from the two-dimensional vibrator;
a first oscillation circuit that outputs a first resonance frequency corresponding to a first rotational vibration mode based on the phase detected by the first detector;
a second oscillation circuit that outputs a second resonance frequency corresponding to a second rotational vibration mode based on the phase detected by the second detector;
A magnetic field sensor that detects a magnetic field based on a first resonance frequency and a second resonance frequency.

Another aspect of the present invention is
A drive signal corresponding to the first rotational vibration mode, a drive signal corresponding to the second rotational vibration mode, and a first current signal and the second rotational vibration mode corresponding to the first rotational vibration mode for the two-dimensional vibrator. A second current signal corresponding to is input,
A first detection unit detects the amplitude and phase of a component corresponding to the first rotational vibration mode from the signal output from the two-dimensional oscillator,
A second detection unit detects the amplitude and phase of a component corresponding to the second rotational vibration mode from the signal output from the two-dimensional oscillator,
the first oscillation circuit outputs a first resonance frequency corresponding to the first rotational vibration mode based on the phase detected by the first detector;
the second oscillation circuit outputs a second resonance frequency corresponding to the second rotational vibration mode based on the phase detected by the second detector;
The magnetic field detection method, wherein the magnetic field detection unit detects the magnetic field based on the first resonance frequency and the second resonance frequency.

According to the present invention, it is possible to provide a magnetic field sensor and a magnetic field detection method that are robust against changes in temperature. It should be noted that the contents of the present invention should not be construed as being limited by the effects exemplified in this specification.

FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; FIG. 2 is a diagram that is referred to when a description of the underlying technology of the present invention is made; It is a figure referred when description about an outline of one embodiment is made. It is a figure referred when description about an outline of one embodiment is made. It is a figure referred when description about an outline of one embodiment is made. It is a figure referred when description about an outline of one embodiment is made. It is a figure referred when description about an outline of one embodiment is made. It is a figure referred when description about an outline of one embodiment is made. FIG. 4 is a diagram for explaining a configuration example of a two-dimensional transducer according to one embodiment; 1 is a block diagram showing a configuration example of a magnetic field sensor according to an embodiment; FIG. It is a figure for demonstrating an example of the effect obtained by one embodiment.

Hereinafter, embodiments of the present invention and the like will be described with reference to the drawings. The description will be given in the following order.
<Regarding the technology that is the premise of the present invention>
<One embodiment>
<Modification>
The embodiments and the like described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments and the like.

<Regarding the technology that is the premise of the present invention>
The inventor of this patent application has previously proposed a gyro device and a control method for the gyro device. The content of the proposal is published as a patent document, Japanese Patent Application Laid-Open No. 2020-169819. The content described in the patent document can be applied to the present patent application. Schematically, the present invention is a magnetic field sensor obtained by improving the gyro device described in the above patent document, that is, a magnetic field sensor applying the principle of FM (Frequency Modulation) gyroscope. Therefore, in order to facilitate understanding of the present invention, the contents described in the above-mentioned patent documents, which are the premise of the present invention, will be briefly described. It should be noted that the present invention does not necessarily include all of the contents described in the above patent documents, and a part thereof may be used.

First, a general gyro device (gyroscope) will be described. In the following description, a small vibrating gyro device using MEMS (Micro Electro Mechanical Systems) will be described as an example. The gyro device detects the angular velocity of rotation (hereinafter referred to as the rotational angular velocity as appropriate). A plurality of methods are known for detecting the rotational angular velocity _Ωz . As a first method, a method called AM (Amplitude Modulation) mode is known. In AM mode, the angular velocity is obtained by measuring the amplitude (displacement) along the sense axis (eg, Y-axis) that changes due to the Coriolis force when vibration is applied along the drive axis (eg, X-axis). Since the amplitude in the sense axis direction is proportional to the rotational angular velocity _Ωz , the rotational angular velocity _Ωz can be detected by detecting the amplitude. In the AM mode, the resonance frequencies in the drive axis direction and the sense axis direction are set to be different (mode mismatch) in consideration of the fact that the vibration applied in the drive axis direction directly excites the sense axis direction. However, in the AM mode, since measurements are performed at a frequency distant from the resonance frequency, there are problems such as a decrease in sensitivity. In AM mode, there is a trade-off in principle between sensitivity and measurement bandwidth, and it is impossible to achieve both high sensitivity and wide bandwidth.

The second method is a method called force rebalancing, in which feedback control is applied so that the AM mode amplitude in the sense axis direction is always 0, and the rotational angular velocity is obtained from the magnitude of the feedback signal. In this case, a vibrator in which the resonance frequencies of the drive axis and the sense axis are matched (mode-matched) can be used. However, there is a problem that the scale factor (the magnitude of the output with respect to the rotational angular velocity) fluctuates due to temperature and the like.

In view of the problems of the first and second methods as described above, the embodiment described later employs driving the gyro device in FM mode. Compared to other methods, the FM mode has advantages such as accurate and stable sensitivity (scale factor), superior temperature characteristics in principle, and unlimited dynamic range. mentioned.

Here, the basic principle of FM mode will be explained. Since the principle of the FM mode itself is publicly known, only a brief description will be given here. An FM mode gyro is composed of a vibrator (also called a resonator) that vibrates in two orthogonal (independent) axial directions. In FM mode, vibrators whose resonance frequencies are matched on each axis (mode-matched) are used. In this state, it is known that when a rotational angular velocity is given to the vibrator, the relationship represented by the following formula 1 holds. In Equation 1, λ is the resonance frequency, ω is the resonance frequency when no rotation is applied (since the mode is matched, the resonance frequency is the same for both axes), and Ω _z is the rotational angular velocity given to the oscillator. there is

It should be noted that the vibration referred to below is not limited to linear vibration (for example, X direction and Y direction), and any vibration can be used as long as it is a mode-matched orthogonal vibration mode. For example, in the case of a ring-shaped resonator, as shown in Figs. 1 and 2, the two orthogonal vibrations are not necessarily simple linear vibrations, but the state of displacement in each vibration mode is represented by mode coordinates (generalized coordinates), it can be treated in exactly the same way as linear vibration. In the following, including these mode coordinates (generalized coordinates), one mode is called "X axis (or X direction)", and the mode orthogonal to it is called "Y axis (or Y direction)". Modes 1 and 2 in FIGS. 1 and 2 are mathematically or vibrationally orthogonal).

Formula 2 below is derived from Formula 1.

That is, as shown by Equation 2, the resonance frequencies in the X-axis and Y-axis directions match when no rotation is applied, that is, mode match. It is divided into _z and ω-Ω _z . Assuming that these two resonance frequencies are λ _{1 and} λ ₂ , the difference (deviation) between the resonance frequencies λ _{1 and} λ ₂ is proportional to the rotational angular velocity _Ωz . For example, the rotation angular velocity Ω _z can be obtained by the following formula 3.

where the motion corresponding to λ ₁ (= ω + Ω _z ) corresponds to clockwise (CW) and the motion corresponding to λ ₂ (= ω - Ω _z ) corresponds to counterclockwise (CCW). there is In other words, when rotation is applied to a mode-matched vibrator, the natural vibration mode is not linear (vibration in the X or Y direction alone), but rotational vibration (the phase of vibration in the X and Y directions is 2-dimensional vibration with a deviation of ±90 degrees (°). Note that the actual rotation of the vibrator is a superposition of these CW mode and CCW mode.

"How to detect the components of each mode"
The FM mode has been described above. For example, control is performed to excite one vibrator that is two-dimensionally mode-matched in the above-described FM mode (hereinafter referred to as a two-dimensional vibrator as appropriate). Therefore, in order to obtain the rotational angular velocity _Ωz , the components of the CW mode (first rotational vibration mode) and CCW mode (second rotational vibration mode) contained in the rotational vibration (output) of the two-dimensional oscillator must be separated. must be detected by Therefore, next, a method for separating and detecting the CW mode component and the CCW mode component from the output of the two-dimensional oscillator will be described.

FIG. 3 is a diagram for explaining a general synchronous detection method. A signal having a predetermined amplitude (Amplitude) and phase (Phase) in the input signal (Signal) SI is input. An input signal SI is branched and input to multipliers (mixers) 1 and 3, respectively. In the coherent detection method, two signals whose phases are shifted by 90 degrees are used as reference signals, and after the reference signals are multiplied by separate multipliers 1 and 3, filtering is performed to obtain a demodulated output. For example, a cosine wave and a sine wave are used as reference signals, the multiplier 1 multiplies the input signal SI by the cosine wave, and the multiplier 3 multiplies the input signal SI by the sine wave.

The signal output from the multiplier 1 is input to the LPF (Low Pass Filter) 2 and filtered. Filtering by the LPF 2 outputs only components that have the same frequency and the same phase as the reference signal (cosine wave in this example).

On the other hand, the signal output from the multiplier 3 is input to the LPF 4 and filtered. Filtering by the LPF 4 outputs only components having the same frequency and phase as the reference signal (sin wave in this example) in the multiplier 3 .

The input signal SI is demodulated by outputs from LPFs 2 and 4, and the amplitude r and phase θ of the input signal SI are detected based on the demodulated output.

By developing and applying this synchronous detection method, processing is performed to detect the CW mode component and the CCW mode component. In the following explanation, we will explain an example of detecting only the CW mode component from a signal that is a combination of the CW mode and the CCW mode generated in the two-dimensional oscillator. components can be detected.

FIG. 4 is a diagram for explaining a method of detecting a CW mode component from the input signal SI. A signal output from the two-dimensional oscillator is input as the input signal SI. When a two-dimensional oscillator is used, the input signal SI can be expressed in vector representation including components in the X and Y directions, as shown.

The input signal SI is branched and input to multipliers 1 and 3, respectively. Signals CW-I (In phase) and CW-Q (Quadrature Phase) are used as reference signals, and the multiplier 1 multiplies the input signal SI by the signal CW-I. Multiplication by I is performed by the multiplier 3 . Signals CW-I and CW-Q are signals having the same amplitude, frequency, and rotation direction, but with a phase difference of 90 degrees, as symbolically shown in FIG.

The input signal SI is multiplied by the signal CW-I by the multiplier 1, and the output is supplied to the LPF 2. The multiplier 3 multiplies the input signal SI by the signal CW-Q, and the output is supplied to the LPF 4 . As a result of filtering by LPFs 2 and 4, the input signal SI is demodulated, and the amplitude r and phase θ of the CW mode component included in the input signal SI can be detected based on the demodulated output.

FIG. 5 is a diagram for explaining a detailed configuration example of the multipliers 1 and 3 described above. The multiplier 1 includes, for example, a multiplier 1a, a multiplier 1b, and an adder 1c. The multiplier 3 includes, for example, a multiplier 3a, a multiplier 3b, and an adder 3c.

As described above, in the case of a two-dimensional oscillator, signals (amplitudes) in the X-axis and Y-axis directions (hereinafter referred to as signals SIX and SIY as appropriate) are input to the multiplier 1 as the input signal SI. The multiplier 1a multiplies the signal SIX by the X-axis component of the signal CW-I, and the multiplier 1b multiplies the signal SIY by the Y-axis component of the signal CW-I. The adder 1c adds the outputs of the multipliers 1a and 1b and outputs the result to the LPF2.

The multiplier 3a multiplies the signal SIX by the X-axis component of the signal CW-Q, and the multiplier 3b multiplies the signal SIY by the Y-axis component of the signal CW-Q. The adder 3c adds the outputs of the multipliers 3a and 3b and outputs the result to the LPF 4.

The point that the CW mode component included in the output of the two-dimensional oscillator can be detected by the method described above will be described in more detail with reference to FIGS. 6 to 9. FIG. The example shown in FIG. 6 is an example of detection using the signal CW-I as a reference signal. In this example, the signal in the X-axis direction of CW-I is a sine wave, and the signal in the Y-axis direction is a cosine wave. If it is assumed that the input signal SI is only the component of the signal CW-I, the output waveform of the multiplier 1a is the waveform WA1a, and the output waveform of the multiplier 1b is the waveform WA2a. The waveform of the signal obtained by adding the outputs of the multipliers by the adder 1c becomes the waveform WA3a. When this signal waveform is passed through LPF2, the waveform of the obtained signal becomes waveform WA4a (DC component) similar to waveform WA3a because the filtering process by LPF2 is equivalent to the process of obtaining the average. That is, when the input signal SI contains the component of the signal CW-I, the component can be detected by detection using the signal CW-I.

The example shown in FIG. 7 is an example of detection using the signal CW-I as a reference signal, but it is assumed that the input signal SI is only the component of the signal CW-Q that is 90 degrees out of phase with the signal CW-I. For example. In this case, the output waveform of the multiplier 1a becomes the waveform WA1b, and the output waveform of the multiplier 1b becomes the waveform WA2b. The signal obtained by adding the outputs of these waveforms by the adder 1c becomes 0 as shown in the figure, and therefore the output of the LPF 2 also becomes 0 as shown in the figure.

The example shown in FIG. 8 is an example of detection using the signal CW-I as the reference signal, but the input signal SI is only the component of the counterclockwise signal CCW-I whose rotation direction is different from that of the signal CW-I. This example assumes that In this case, the output waveform of the multiplier 1a becomes the waveform WA1c, and the output waveform of the multiplier 1b becomes the waveform WA2c. The waveform of the signal obtained by adding the outputs of the multipliers by the adder 1c becomes a waveform WA3c that is symmetrical with 0 as the center. When the signal of waveform WA3a is passed through LPF2, its output becomes 0 as shown.

The example shown in FIG. 9 is an example of detection using the signal CW-I as the reference signal. This is an example assuming only the component of the signal CCW-Q whose phase differs from I by 90 degrees. In this case, the output waveform of the multiplier 1a becomes the waveform WA1d, and the output waveform of the multiplier 1b becomes the waveform WA2d. The waveform of the signal obtained by adding the outputs of the multipliers by the adder 1c becomes a waveform WA3d that is symmetrical about 0 as the center. When the signal of waveform WA3d is passed through LPF2, its output becomes 0 as shown.

That is, any two-dimensional oscillation (expressed by the linear combination of CW-I, CW-Q, CCW-I, and CCW-Q) occurring in the two-dimensional oscillator is expressed by using the signal CW-I as a reference signal. With synchronous detection, only the component of the signal CW-I included in the output signal of the two-dimensional oscillator is obtained. This is also true for detected components when using other signals as reference signals. Table 1 below is obtained by summarizing the above.

As shown in Table 1, when the signal CW-Q component is included in the output of the two-dimensional oscillator, the reference signal can be detected as the signal CW-Q, while the other signal components have no output. becomes 0. When the output of the two-dimensional oscillator contains the component of the signal CCW-I, the reference signal can be detected as the signal CCW-I, while the output of the other signal components is 0. When the output of the two-dimensional oscillator contains the component of the signal CCW-Q, the reference signal can be detected as the signal CCW-Q, while the output of the other signal components is 0. That is, for example, if two detectors are provided and the reference signal in each detector is set to a combination of signal CW-I and signal CW-Q, and a combination of signal CCW-I and signal CCW-Q, two-dimensional vibration CW mode component and CCW mode component can be detected independently from the child's output.

Based on the above description, a gyro device (gyro device 10) capable of detecting angular velocity will be described. FIG. 10 is a diagram showing a configuration example of the gyro device 10. As shown in FIG. The gyro device 10 includes, for example, a single two-dimensional oscillator 15, a drive signal generator 20, a first detector 30a, a first PLL (Phase Locked Loop) circuit 40a as an example of a first oscillation circuit, A first AGC (Automatic Gain Control) section 50a, a second detection section 30b, a second PLL circuit 40b as an example of a second oscillation circuit, a second AGC section 50b, and a two-dimensional oscillator 15 provided on the input side of the Amplifiers 61a and 61b and amplifiers 62a and 62b provided on the output side of the two-dimensional oscillator 15 are provided.

Although not shown, the gyro device 10 may be equipped with a DA (Digital to Analog) converter and an AD (Analog to Digital) converter, and may perform each process by digital signal processing. In this case, the DA converter is provided, for example, in front of the amplifiers 61a and 61b, and configured to convert the digital drive signal output from the drive signal generator 20 into an analog drive signal. Further, the AD converter is provided, for example, in the rear stage of the amplifiers 62a and 62b, and is configured to convert analog format signals output from the two-dimensional oscillator 15 into digital format.

The two-dimensional vibrator 15 is, for example, a ring-shaped vibrating member that can be excited by drive signals corresponding to CW mode and CCW mode. The shape of the two-dimensional vibrator 15 is not limited to the ring shape, and may be any shape such as a square plate, a cylinder, a square prism, or a quadruple mass using four masses. is.

The drive signal generator 20 supplies the two-dimensional vibrator 15 with a drive signal obtained by multiplexing a drive signal corresponding to the CW mode (first drive signal) and a drive signal corresponding to the CCW mode (second drive signal). The drive signal supplied from the drive signal generator 20 excites the two-dimensional vibrator 15 . In this example, the drive signal for the X-axis direction corresponding to the CW mode is a cos wave (hereinafter referred to as cos _cw signal), and the drive signal for the Y-axis direction is a -sin wave (hereinafter referred to as -sin _cw signal). is used. Note that the drive signal does not necessarily have to be a cosine wave or a -sin wave as long as the Y-direction signal leads the X-direction signal by 90 degrees in phase. -cos wave (hereinafter referred to as -cos _CCW signal) as the drive signal for the X-axis direction corresponding to CCW mode, and -sin wave (hereinafter referred to as -sin _CCW signal) as the drive signal for the Y-axis direction is used. It should be noted that the drive signal does not necessarily need to be a -cos wave or -sin wave if the Y-direction signal is 90 degrees behind the X-direction signal. The drive signal generator 20, for example, generates a drive signal corresponding to the CW mode based on the signal fed back from the first PLL circuit 40a, and generates a drive signal corresponding to the CCW mode based on the signal fed back from the second PLL circuit 40b. Generate a signal. The drive signal generator 20 includes, for example, a multiplier 201, a multiplier 202, a multiplier 203, a multiplier 204, an adder 205, and an adder 206.

The first detector 30 a detects the amplitude r _cw and the phase θ _cw of the CW component included in the output of the two-dimensional oscillator 15 . Details of the first detection unit 30a will be described later.

The first PLL circuit 40a includes a phase comparator 41a, a PID (Proportional Integral Differential) control section 42a, and an oscillator 43a such as a VCO (Voltage Controlled Oscillator) or an NCO (Numerical Controlled Oscillator) that can change the oscillation frequency. I have. Although detailed illustration is omitted to prevent the illustration from becoming complicated, the output of the first PLL circuit 40a (all or part of the output may be used) is the drive signal generation unit 20, the first It is configured to be fed back to each of the detection units 30a.

The first AGC section 50a includes an amplitude comparator 51a and a PID control section 52a. The output of the first AGC section 50 a is configured to be fed back to the drive signal generation section 20 .

The second detection section 30b detects the amplitude r _CCW and phase θ _CCW of the CCW component included in the output of the two-dimensional oscillator 15 . Details of the second detection unit 30b will be described later.

The second PLL circuit 40b includes a phase comparator 41b, a PID control section 42b, and an oscillator 43b capable of changing the oscillation frequency of VCO, NCO, or the like. Although detailed illustration is omitted to prevent the illustration from becoming complicated, the output of the second PLL circuit 40b (it may be all or part of the output) is the drive signal generation unit 20, the second It is configured to be fed back to each of the detection units 30b.

The second AGC section 50b includes an amplitude comparator 51b and a PID control section 52b. The output of the second AGC section 50b is configured to be fed back to the drive signal generation section 20. FIG.

FIG. 11 is a diagram for explaining a configuration example of the first detection unit 30a. The first detection unit 30a includes detectors 31a and 32a to which the signal output from the two-dimensional transducer 15 is branched and input, an LPF 33a that filters the output of the detector 31a, and an output of the detector 32a. An LPF 34a that performs filtering and an amplitude phase detector 35a that detects the amplitude r _cw and phase θ _cw of the CW component contained in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPF 33a and LPF 34a. .

The detector 31a includes a multiplier 310a to which an X-axis component of the output from the two-dimensional oscillator 15 is input, and a multiplier 310a to which a Y-axis component of the output from the two-dimensional oscillator 15 is input. 311a and an adder 312a for adding the respective outputs of the multipliers 310a and 311a. The detector 32a includes a multiplier 320a to which the X-axis direction component of the output from the two-dimensional oscillator 15 is input, and a multiplier 320a to which the Y-axis direction component of the output from the two-dimensional oscillator 15 is input. 321a and an adder 322a for adding the respective outputs of the multipliers 320a and 321a.

In this example, the CW-I component in the X-axis direction is a sine signal, the CW-I component in the Y-axis direction is a cos signal, the CW-Q component in the X-axis direction is a cos signal, and the CW-I component in the Y-axis direction is a cos signal. The -Q component is the -sin signal.

FIG. 12 is a diagram for explaining a configuration example of the second detection unit 30b. The second detection unit 30b includes detectors 31b and 32b to which the signal from the two-dimensional transducer 15 is branched and input, an LPF 33b that performs filtering on the output of the detector 31b, and a filter on the output of the detector 32b. and an amplitude phase detector 35b for detecting the amplitude r _CCW and phase θ _CCW of the CCW component contained in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPF 33 b and LPF 34 b.

The detector 31b includes a multiplier 310b to which an X-axis component of the output from the two-dimensional oscillator 15 is input, and a multiplier 310b to which a Y-axis component of the output from the two-dimensional oscillator 15 is input. 311b and an adder 312b that adds the outputs from the multipliers 310b and 311b. The detector 32b includes a multiplier 320b to which the X-axis component of the output from the two-dimensional oscillator 15 is input, and a multiplier 320b to which the Y-axis component of the output from the two-dimensional oscillator 15 is input. 321b and an adder 322b that adds the respective outputs of the multipliers 320b and 321b.

In this example, the CCW-I component in the X-axis direction is a -sin signal, the CCW-I component in the Y-axis direction is a cos signal, the CCW-Q component in the X-axis direction is a -cos signal, and the Y-axis direction is the -sin signal.

Next, an operation example of the gyro device 10 will be described with reference to FIGS. 10 to 12. FIG. A drive signal generator 20 generates a drive signal for the two-dimensional oscillator 15 . After the signal fed back from the PID control unit 52a is multiplied by the multipliers 201 and 202 for each of the cos _cw signal and the -sin _cw signal, the output signal from the multiplier 201 is supplied to the adder 205, The output signal from multiplier 202 is provided to adder 206 . The -cos _CCW signal and the -sin _CCW signal are each multiplied by multipliers 203 and 204 by signals fed back from PID control section 52b, and then the output signal from multiplier 203 is supplied to adder 205. , the output signal from multiplier 204 is provided to adder 206 . Adder 205 adds the output signal from multiplier 201 and the output signal from multiplier 203 and outputs the result. After the output signal from the adder 205 is amplified with an appropriate amplification factor by the amplifier 61a, it is input to the two-dimensional oscillator 15 as the input _Xd . On the other hand, adder 206 adds the output signal from multiplier 202 and the output signal from multiplier 204 and outputs the result. After the output signal from the adder 206 is amplified with an appropriate amplification factor by the amplifier 61b, it is input to the two-dimensional oscillator 15 as the input _Yd .

A two-dimensional oscillator 15 is excited by the inputs X _d and Y _d , and outputs X _s and Y _s from the two-dimensional oscillator 15 are obtained. After the outputs _Xs and _Ys from the two-dimensional vibrator 15 are amplified with an appropriate amplification factor by the amplifiers 62a and 62b, the outputs _Xs are branched and sent to the first and second detectors 30a and 30b, respectively. Then, the output _Ys is branched and input to the first and second detectors 30a and 30b.

The first detector 30 a detects the CW component included in the output of the two-dimensional oscillator 15 . Specifically, the detector 31a in the first detection unit 30a detects the signal CW-I, and the result is filtered by the LPF 33a. The component is detected, and the detection result is supplied to the amplitude phase detector 35a. Further, the detector 32a in the first detection unit 30a detects the signal CW-Q, and the result is filtered by the LPF 34a to detect the CW-Q component included in the output of the two-dimensional oscillator 15. and supplies the detection result to the amplitude phase detector 35a. The amplitude phase detector 35a detects the amplitude r _cw and the phase θ _cw of the CW component contained in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPF 33a and LPF 34a. That is, as described above, by performing synchronous detection using the signals CW-I and CW-Q as reference signals, only the CW component contained in the output of the two-dimensional oscillator 15 can be detected.

The phase θ _cw detected by the first detector 30a is supplied to the first PLL circuit 40a. The phase comparator 41a in the first PLL circuit 40a compares the phase θ _cw and the set phase θ _cw,set (in the following explanation, proceed assuming that θ _cw,set =90°), and performs PID control based on the comparison result. The part 42a performs control to set the phase θ _cw to 90°, that is, the resonance frequency f _cw . The oscillator 43a is controlled by the output from the PID control _{section 42a, whereby the signal sin cw and} the signal cos _cw of the resonance frequency fcw are output from the oscillator 43a. These signals are fed back to the input side, and control is performed such that the resonance frequency of the drive signal corresponding to the CW mode is maintained at the resonance frequency _fcw . Also, the signal sin _cw and the signal cos _cw are fed back to the first detector 30a, and based on this, the signal CW-I and the signal CW-Q are generated as reference signals. In this example, the relationships sin=sin _cw , cos=cos _cw , and -sin=-1*sin _cw are established between the signal to be fed back and the reference signal.

The amplitude r _cw obtained by the first detection section 30a is supplied to the first AGC section 50a. The amplitude comparator 51a in the first AGC unit 50a compares the amplitude r _cw with a predetermined first set value Rset _,cw, and based on the comparison result, the PID control unit 52a adjusts the amplitude r _cw to the predetermined first set value. Executes the control with the value R _set,cw . The output from the PID controller 52a is fed back to the drive signal generator 20, and the gain is controlled so that the amplitude of the drive signal corresponding to the CW mode is maintained at the first set value _Rset,cw .

A similar process is performed for a system for detecting CCW components contained in the output of the two-dimensional oscillator 15 . Specifically, the detector 31b in the second detection unit 30b detects using the signal CCW-I, and the CCW-I included in the output of the two-dimensional oscillator 15 is filtered by the LPF 33b. The component is detected, and the detection result is supplied to the amplitude/phase detector 35b. In addition, the detector 32b in the second detection unit 30b detects using the signal CCW-Q, and the result is filtered by the LPF 34b to detect the CCW-Q component included in the output of the two-dimensional oscillator 15. and supplies the detection result to the amplitude phase detector 35b. The amplitude phase detector 35b detects the amplitude r CCW and the phase θ _CCW of the CCW component included in the output signal of the two-dimensional vibrator 15 based on the outputs from _the LPF 33b and LPF 34b. That is, as described above, by synchronously detecting the signal CCW-I and the signal CCW-Q as reference signals, only the CCW component included in the output of the two-dimensional oscillator 15 can be detected.

The phase θ _CCW obtained by the second detector 30b is supplied to the second PLL circuit 40b. The phase comparator 41b in the second PLL circuit 40b compares the phase θ _CCW with 90°, and based on the comparison result, the PID controller 42b controls the phase θ _CCW to 0, that is, the resonance frequency _fcw . The oscillator 43b is controlled by the output from the PID control section 42b, whereby the oscillator 43b outputs the signal sin _CCW and the signal cos _CCW of the resonance frequency f _CCW which are in phase with each other. The resonance frequency f _CCW is fed back to the input side, and control is performed to maintain the resonance frequency of the driving signal corresponding to the CCW mode at the resonance frequency f _CCW . Also, the signal sin _CCW and the signal cos _CCW are fed back to the second detector 30b, and based on this, the signal CCW-I and the signal CCW-Q are generated as reference signals. In this example, the relationships -sin=sin _ccw , cos=cos _ccw , -cos=-1*cos _ccw are established between the signal to be fed back and the reference signal.

The amplitude r _CCW obtained by the second detection section 30b is supplied to the second AGC section 50b. The amplitude comparator 51b in the second AGC section 50b compares the amplitude _rCCW with the second set value Rset _,CCW , and based on the comparison result, the PID control section 52b determines whether the amplitude _rCCW is the second set value _Rset,CCW. Execute control to be _CCW . The output from the PID controller 52b is fed back to the drive signal generator 20, and the gain is controlled so that the amplitude of the drive signal corresponding to the CCW mode is maintained at the second set value Rset _,CCW .

FIG. 13 is a diagram schematically showing the flow of signals in the gyro device 10. FIG. Thick lines in FIG. 13 indicate the flow of signals. The CCW component contained in the output of the two-dimensional oscillator 15 is cut by the first detection section 30a, and only the CW component loops through one system (upper system in FIG. 13). The CW component contained in the output of the two-dimensional oscillator 15 is cut by the second detector 30b, and only the CCW component loops through the other system (lower system in FIG. 13).

Next, a configuration example of the angular velocity detector (angular velocity detector 70) will be described. In this example, the angular velocity detector 70 is described as being incorporated in the gyro device 10, but may be incorporated in another device.

FIG. 14 is a diagram showing a configuration example of the angular velocity detector 70. As shown in FIG. The angular velocity detector 70 includes a subtractor 71 and a multiplier 72, for example. The angular velocity detector 70 obtains the resonance frequency f _cw output from the first PLL circuit 40a and the resonance frequency f _CCW output from the second PLL circuit 40b. At 72, it is multiplied by a constant (in the case of an ideal oscillator with an angular gain of 1, it is multiplied by 1/2). That is, the angular velocity detection unit 70 detects the rotation angular velocity _Ωz by performing the same calculation as Equation 3 described above. By integrating this rotational angular velocity _Ωz , the gyro device 10 can detect the angle of rotation.

According to the gyro device 10 described above, since it is composed of a single two-dimensional vibrator, it is possible to reduce the size of the device, and the vibrator can be used in the same manner as when a plurality of vibrators are used. It eliminates the need to match the characteristics and usage environment of Furthermore, it is possible to independently detect the components corresponding to CW and CCW modes from the output of the two-dimensional oscillator, detect the rotational angular velocity from these detection results, and finally detect the rotational angle. can.

<One embodiment>
[overview]
This embodiment realizes a magnetic field sensor (magnetic field sensor 1000) in which the temperature dependence is canceled by improving the gyro device 10 described above. First, the principle of such a magnetic field sensor will be schematically described with reference to FIGS. 15 to 18. FIG.

FIG. 15 shows the circular motion of the two-dimensional oscillator 15 in the CW mode described above, and FIG. 16 is a diagram schematically showing the circular motion of the two-dimensional oscillator 15 in the CCW mode described above. 15 and 16 (the same applies to FIGS. 17 and 18), the two-dimensional vibrator 15 is represented by a circular mass, and four springs supporting the mass (a pair of springs in each of the X and Y directions). is shown schematically.

Since the two-dimensional oscillator 15 has equivalent spring constants in the x-axis and y-axis, in other words, it is degenerate, normally (when no magnetic field is applied), the same frequency f ₀ to vibrate. Let f _cw be the frequency of rotational motion in CW mode and f _ccw be the frequency of rotational motion in CCW mode, then f _cw =f ₀ and f _ccw =f ₀ . Note that f ₀ is the frequency defined by the mass of the mass and the spring constant. Degeneracy means that many modes have the same energy (that is, resonance frequency). In this example, the resonance frequency of the two-dimensional oscillator 15 is the same for each rotational vibration mode in the stationary coordinate system. means that

Here, as shown in FIG. 17, consider the case where there is a magnetic field (B _z ) during vibration in the CW mode. A current i is applied to the two-dimensional vibrator 15 in synchronization with the vibration. Due to the presence of the magnetic field B _z , the Lorentz force F (F=I×BL) is generated when the current i is applied. By synchronizing with the vibration, in other words, by passing the current i in the tangential direction of rotation, an inward Lorentz force F is always generated as shown in FIG. By changing the ratio of the current flowing in the X direction and the current flowing in the Y direction and the amount of current flowing, it is possible to make the current flow equivalently in the tangential direction of rotation.

By generating an inward Lorentz force F, the restoring force of the spring is equivalently strengthened. This increases the resonance frequency. This can be represented by the following formula (4).

Also, as shown in FIG. 18, consider the case where there is a magnetic field (B _z ) during vibration in the CCW mode. A current i is applied to the two-dimensional vibrator 15 in synchronization with the vibration. The direction of the current i flowing in the CCW mode is opposite to the direction of the current i flowing in the CW mode. Due to the presence of the magnetic field B _z , the Lorentz force F is generated when the current i is applied. By synchronizing with the vibration, in other words, by passing the current i in the tangential direction of rotation, an outward Lorentz force F is always generated as shown in FIG. By changing the ratio of the current flowing in the X direction and the current flowing in the Y direction and the amount of current flowing, it is possible to make the current flow equivalently in the tangential direction of rotation.

By generating an outward Lorentz force F, the restoring force of the spring is equivalently weakened. This lowers the resonance frequency. This can be represented by the following formula (5). In addition, if the direction of the Lorentz force acts in the opposite direction in the CW mote and the CCW mode, even if it is the opposite direction to the above (that is, the outward Lorentz force in the CW mode and the inward Lorentz force in the CCW mode) good.

The above changes are represented by the following formula (6).

As shown in Equation (6), the degeneracy is resolved by the presence of the magnetic field, and the vibration frequencies in each vibration mode become those shown in Equations (4) and (5). Here, f ₀ has temperature dependence, that is, the Young's modulus of the two-dimensional oscillator 15 changes with temperature. However, the frequency difference (f _cw −f _ccw ) is not affected by temperature because f ₀ is cancelled. Also, the current flowing through the two-dimensional oscillator 15 can be controlled. From the above, for example, the magnetic field can be measured by removing the influence of the current i by calculation after measuring the frequency difference. Since the frequency difference is not affected by temperature changes as described above, it is possible to measure the magnetic field with high accuracy.

By the way, when the gyro device 10 is used as a magnetic field sensor, the magnetic field sensor also detects angular velocity. In the absence of a magnetic field, an angular rate modulated frequency term kΩ appears (for CW mode), as shown in equation (7) below.

If there is a magnetic field, it can be represented by the above-mentioned formula (4), so the following formula (8) is derived from the formulas (4) and (7).

The same is true for f _CCW . From the above, the frequency difference Δf(f _cw -f _ccw ) when the gyro device 10 is used as a magnetic field sensor is expressed by the following equation (9).

In the Δf expression in equation (9), an angular velocity-dependent term 2kΩ and a magnetic field and current-dependent 2Δf(I,B) term (a term that finally corresponds to the magnetic field itself by performing calculations) appear. FIG. 19 is a diagram schematically showing spectra of waveforms corresponding to respective terms. The horizontal axis of FIG. 19 indicates the signal frequency, and the vertical axis indicates the magnitude of the signal. A waveform WA5 corresponds to the term 2 kΩ dependent on the angular velocity, and a waveform WA6 corresponds to the term 2Δf(I, B) dependent on the magnetic field and current.

As shown in FIG. 19, since both waveforms generally overlap in the frequency domain, the angular velocity and the magnetic field cannot be separated from each other, and both cannot be detected. Therefore, the magnitude of the controllable current i is modulated at a predetermined frequency. The predetermined frequency (the frequency of the modulated signal) is a frequency higher than the angular velocity frequency (for example, 100 Hz) to be detected. For example, current i is modulated at a given frequency W _B (i=i ₀ sin(W _B ,t)). Note that the first frequency and the second frequency may be the same or different.

As a result, as schematically shown in FIG. 20, the frequency fluctuation component due to the magnetic field (waveform WA6 in this example) is frequency-shifted to the high frequency side. If this is represented by an equation, it becomes the following equation (10).

A frequency fluctuation component caused by a magnetic field can be detected by synchronous detection at the frequency W _B . Since the magnitude of the current i is known, only the magnetic field component can be detected by dividing by the current i.

[An example of a two-dimensional oscillator]
Next, the two-dimensional vibrator 15A applicable to this embodiment will be described. The two-dimensional vibrator 15A has, for example, an additional configuration for causing a current to flow through the two-dimensional vibrator 15A. FIG. 21 shows a configuration example of the two-dimensional oscillator 15A.

The two-dimensional oscillator 15A has a mass 151 near the center. The shape of the mass 151 is not limited to a rectangular shape, and may be other shapes such as a circular shape. In principle, one mass 151 may be used, but a plurality of masses may be used. For example, using four cells 151 can increase the Q value.

Like the two-dimensional oscillator 15, the two-dimensional oscillator 15A is a degenerate oscillator, so it has a symmetrical and equivalent configuration in each of the X and Y directions. Such a configuration generally includes a drive electrode, a shuttle connected to mass 151 and driven by the drive electrode, and a sense electrode for detecting displacement of the shuttle.

For example, a drive electrode 151A is provided on the X+ side (right side in FIG. 21). Drive electrode 151A is connected to shuttle 151B. A voltage is applied to the comb-teeth electrode of the drive electrode 151A to displace the shuttle 151B, thereby displacing the mass 151 connected to the shuttle 151B. The displacement of the shuttle 151B can be detected by detecting a change in electrostatic capacity generated in the comb-teeth electrodes of the sense electrode 151C. The shuttle 151B is also provided with ports 151D and 151E for current flow. For example, control is performed to flow current from the port 151D to the port 151E.

A drive electrode 152A is provided on the X-side (left side in FIG. 21). Drive electrode 152A is connected to shuttle 152B. A voltage is applied to the comb-teeth electrode of the drive electrode 152A to displace the shuttle 152B, thereby displacing the mass 151 connected to the shuttle 152B. Displacement of the shuttle 152B can be detected by detecting a change in capacitance generated in the comb-tooth electrodes of the sense electrode 152C. Shuttle 152B is also provided with ports 152D and 152E for conducting current. For example, control is performed to flow current from the port 152D to the port 152E.

For example, a drive electrode 153A is provided on the Y+ side (upper side in FIG. 21). Drive electrode 153A is connected to shuttle 153B. A voltage is applied to the comb-teeth electrode of the drive electrode 153A to displace the shuttle 153B, thereby displacing the mass 151 connected to the shuttle 153B. Displacement of the shuttle 153B can be detected by detecting a change in capacitance generated in the comb-tooth electrodes of the sense electrode 153C. The shuttle 153B is also provided with ports 153D and 153E for current flow. For example, control is performed to flow current from the port 153D to the port 153E.

For example, a drive electrode 154A is provided on the Y-side (lower side in FIG. 21). Drive electrode 154A is connected to shuttle 154B. A voltage is applied to the comb-teeth electrode of the drive electrode 154A to displace the shuttle 154B, thereby displacing the mass 151 connected to the shuttle 154B. Displacement of the shuttle 154B can be detected by detecting a change in capacitance generated in the comb-tooth electrodes of the sense electrode 154C. Shuttle 154B is also provided with ports 154D and 154E for conducting current. For example, control is performed to flow current from the port 154D to the port 154E.

[Configuration example of magnetic field sensor]
FIG. 22 is a block diagram showing a configuration example of a magnetic field sensor (magnetic field sensor 1000) according to this embodiment. The magnetic field sensor 1000 has, for example, all the components of the gyro device 10 described above. The same reference numerals are given to the same or similar configurations as those of the gyro device 10, and redundant explanations will be omitted as appropriate. Moreover, in FIG. 22, only the configuration strongly related to the present invention is illustrated, and the illustration of other configurations is appropriately omitted.

The magnetic field sensor 1000 includes a two-dimensional oscillator 15A, a drive signal generator 20, a first detector 30a, a second detector 30b, a first PLL circuit 40a, and a second PLL circuit 40b. Further, the magnetic field sensor 1000 further includes a first current signal generator 80a, a second current signal generator 80b, a signal source 82, a mixer 85, an adder 86, a magnetic field detector 91, and an LPF 92 as an angular velocity detector. including.

The first current signal generator 80a generates a first current signal corresponding to the CW mode. The first current signal generator 80a has a first current signal converter 81a, a first gain modulator 82a, and a multiplier 83a. The first current signal converter 81a uses a signal (for example, sin _cw and cos _cw of the resonance frequency _fcw ) output from the oscillator 43a of the first PLL circuit 40a and converts the signal into a current. The first gain modulation section 82a generates a signal for amplitude modulation from a predetermined frequency signal (for example, a sine wave signal of 100 Hz or more) generated by the signal source 82. FIG. This signal is multiplied by the current signal in the multiplier 83a to give modulation and generate the first current signal. Note that the structural order of the current signal converter 81a and the multiplier 83a may be reversed.

The second current signal generator 80b generates a second current signal corresponding to CCW mode. The second current signal generator 80b has a second current signal converter 81b, a second gain modulator 82b, a multiplier 83b, and an inverter circuit 84. The second current signal converter 81b uses the signal (for example, sin _ccw and cos _ccw of the resonance frequency _fcw ) output from the oscillator 43b of the second PLL circuit 40b and converts the signal into a current. The inversion circuit 84 inverts the current signal output from the second current signal converter 81b. As a result, the direction of the second current signal generated by the second current signal generator 80b is opposite to the direction of the first current signal. The second gain modulating section 82b generates a signal for amplitude modulation from a predetermined frequency signal (for example, a sine wave signal of 100 Hz or higher) generated by the signal source 82 . This signal is multiplied by the current signal in the multiplier 83b to give modulation and generate a second current signal. Note that the current signal converter 81b, the multiplier 83b, and the inverting circuit 84 may be switched in their structural order.

The mixing section 85 mixes (multiplexes) the first current signal generated by the first current signal generating section 80a and the second current signal generated by the second current signal generating section 80b. The first current signal and the second current signal mixed by the mixing section 85 are input to the two-dimensional vibrator 15A.

The adder 86 calculates the difference between the resonance frequency f _cw (an example of the first resonance frequency) output from the PID 42a and the resonance frequency f _ccw (an example of the second resonance frequency) output from the PID 42b. As a result, Δf, which is the difference between the resonance frequency f _cw and the resonance frequency f _ccw , is obtained. Δf is input to each of the magnetic field detection section 91 and the second LPF 92 .

The magnetic field detector 91 detects the magnetic field based on the resonance frequency f _cw and the resonance frequency f _ccw . The magnetic field detector 91 has a multiplier 91a and a first LPF 91b. Multiplier 91a multiplies Δf by the modulated signal from signal source 82 . The first LPF 91b filters the output of the multiplier 91a so as to pass only low-frequency signals (below the cutoff frequency). After the first LPF 91b, the magnetic field is detected by performing an appropriate calculation (for example, calculation for removing the current component) for detecting the magnetic field.

The second LPF 92 filters the output of the adder 86 to pass only low-frequency (below the cutoff frequency) signals. Thereby, only the signal of the component corresponding to the angular velocity is extracted. Angular velocities are detected by performing appropriate calculations (for example, calculations similar to those performed by the angular velocity detector 70 in the gyro device 10 described above) on the signals that have passed through the second LPF 92 .

[Example of magnetic field sensor operation]
Next, an operation example of the magnetic field sensor 1000 will be described. The drive signal generated by the drive signal generator 20 excites the two-dimensional vibrator 15A. At this time, the x-direction and y-direction current signals (first current signal (Ix) and second current signal (Iy)) mixed by the mixing unit 85 are input to the two-dimensional vibrator 15A.

The phase _θcw is detected by performing the processing described above by the first detection unit 30a. The phase θ _cw is provided to the first PLL circuit 40a. The PID control unit 42a performs control so that the phase _θcw becomes the resonance frequency _fcw based on the comparison result of the phase comparator 41a. The resonance frequency f _cw output from the PID controller 42 a is supplied to the adder 86 . A signal output from the oscillator 43a is fed back to the drive signal generator 20 and used to generate the drive signal. A signal output from the oscillator 43a is converted into a current signal by the first current signal converter 81a. The converted current signal is amplitude-modulated by a first gain modulating section 82a and a multiplier 83a according to a signal generated by a signal source 82 to generate a first current signal. A second current signal is generated by performing similar processing in the CCW loop. After being mixed by the mixing unit 85, the first current signal and the second current signal are input to the two-dimensional vibrator 15A.

The resonance frequency f _cw output from the PID control section 42 b of the second PLL circuit 40 b is supplied to the adder 86 . The calculation performed by the adder 86 provides Δf, which is the difference between the resonance frequency f _cw and the resonance frequency f _ccw .

By multiplying Δf by the signal generated by the signal source 82 by the multiplier 91a, the signal of the magnetic field component is shifted to the low frequency side (the signal of the angular velocity component is shifted to the high frequency side). Then, the signal of the magnetic field component shifted to the low frequency side is detected by the first LPF 91b, and the magnetic field is detected using the detected signal of the magnetic field component.

In addition, the signal of the angular velocity component on the low frequency side is detected by the second LPF 92 with respect to Δf, and the angular velocity is detected using the detected signal of the angular velocity component.

[Effect obtained by this embodiment]
As described above, according to this embodiment, it is possible to provide a sensor capable of detecting not only the angular velocity but also the magnetic field. For example, detection results of acceleration and angular velocity can be corrected by sensing results of the magnetic field sensor. Since there is no need to add a magnetic field sensor as a separate device, the cost of the sensor can be reduced, and the size of the sensor can be reduced.

23A to 23C show an example (simulation result) of the effect obtained by this embodiment. FIG. 23A is a diagram showing the relationship between the magnetic field (horizontal axis) and the frequency of each mode of CW and CCW (vertical axis). In the figure, line LNA corresponds to CW mode, and line LNB corresponds to CCW mode. As shown in FIG. 23A, when a magnetic field is applied, the frequency of each mode changes (the magnitude is the same, but the direction of increase and decrease is opposite).

FIG. 23B is a graph when the results of FIG. 23A are viewed in terms of frequency difference. As shown in FIG. 23B, it can be seen that the frequency difference is approximately directly proportional to the magnetic field.

FIG. 23C is a graph showing the results of FIG. 23B on a log scale. As shown in FIG. 23C, it can be seen that the linearity is exhibited over a wide range (6-digit range in this example). 1 nT (nanotesla) is a change of about 1 μHz. For FM gyro, a change of 1°/hr corresponds to 0.77 μHz. The FM gyro has a stability of about 1°/h. That is, it indicates that the magnetic field can be sufficiently detected with a stability of nT or less. According to this embodiment, it is possible to realize a magnetic field sensor that is smaller than geomagnetism and has a wide dynamic range.

<Modification>
Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications are possible.

As the signal generated by the signal source 82, not only a single-frequency sine wave but also other methods such as spread spectrum technology using a wideband signal may be applied. That is, the signal of the magnetic field component and the signal of the angular velocity component may be separated by spreading the gain with a predetermined spreading code and then despreading the gain.

In the present invention, the shape, excitation method (electrostatic, electromagnetic, piezoelectric, etc.), etc. are not limited to a specific method, etc., as long as the vibrator is two-dimensionally mode-matched.

The circuit that processes the output of the two-dimensional oscillator 15 can also be configured with an integrated circuit such as an ASIC (Application Specific Integrated Circuit).

The magnetic field sensor may be configured to include other circuit elements or the like within the scope of the effects of the present invention. Also, part of the processing in the magnetic field sensor may be performed by another device, a cloud server, or the like. Further, the present invention may be configured as a sensor that detects only magnetic fields without detecting angular velocity.

The magnetic field sensor of the present invention can be applied to other devices (for example, various electronic devices such as game devices, imaging devices, smartphones, mobile phones, personal computers, automobiles, trains, airplanes, helicopters, small aircraft, space equipment, etc.) mobile body, robot, etc.).

The configurations, methods, processes, shapes, materials, numerical values, and the like given in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, and the like may be used as necessary. . In addition, the present invention can be realized by an apparatus, a method, and a system (cloud system, etc.) consisting of a plurality of apparatuses. can be combined with

10 Gyro devices 15, 15A Two-dimensional oscillator 30a First detector 30b Second detector 40a First PLL circuit 40b Second PLL circuit 42a, 42b PID controller 80a First current signal generator 81a First current signal converter 82a First gain modulator 83a Multiplier 80b Second current signal generator 81b... second current signal converter 82b... second gain modulator 83b... multiplier 91... magnetic field detector 91a... multiplier 91b... first LPF
92 2nd LPF
1000 Magnetic field sensor
CW: 1st rotational vibration mode
CCW・・・Second rotational vibration mode

Claims (9)

1. Driven by a drive signal corresponding to a first rotational vibration mode and a drive signal corresponding to a second rotational vibration mode, and further, a first current signal corresponding to the first rotational vibration mode and a second rotational vibration mode. a single two-dimensional oscillator to which the second current signal is input;
   a first detector that detects the amplitude and phase of a component corresponding to the first rotational vibration mode from the signal output from the two-dimensional vibrator;
   a second detector that detects the amplitude and phase of the component corresponding to the second rotational vibration mode from the signal output from the two-dimensional vibrator;
   a first oscillation circuit that outputs a first resonance frequency corresponding to the first rotational vibration mode based on the phase detected by the first detection unit;
   a second oscillation circuit that outputs a second resonance frequency corresponding to the second rotational vibration mode based on the phase detected by the second detection unit;
   A magnetic field sensor that detects a magnetic field based on the first resonance frequency and the second resonance frequency.
2. The magnetic field sensor according to claim 1, further comprising an angular velocity detection unit that detects an angular velocity of rotation based on the first resonance frequency and the second resonance frequency.
3. Based on the signal fed back from the first oscillation circuit, a first drive signal corresponding to the first rotational vibration mode is generated, and based on the signal fed back from the second oscillation circuit, the second drive signal is generated. The magnetic field sensor according to claim 2, further comprising a drive signal generator that generates a second drive signal corresponding to the rotational vibration mode.
4. a first current signal generator that generates the first current signal;
   a second current signal generator that generates the second current signal,
   The first current signal generation unit converts a signal fed back from the first oscillation circuit into a current signal and modulates the current signal to generate the first current signal,
   4. The second current signal generator according to claim 3, wherein the second current signal generator converts a signal fed back from the second oscillation circuit into a current signal, and modulates the current signal to generate the second current signal. magnetic field sensor.
5. The magnetic field sensor according to claim 4, wherein the frequency of the modulated signal is set to a value higher than the frequency of the angular velocity assumed to be detected by the angular velocity detector.
6. The magnetic field sensor according to any one of claims 1 to 5, wherein the magnetic field detection section detects the magnetic field based on a difference between the first resonance frequency and the second resonance frequency.
7. The magnetic field sensor according to any one of claims 2 to 5, wherein the angular velocity detector detects the angular velocity based on a difference between the first resonance frequency and the second resonance frequency.
8. 8. The magnetic field sensor according to any one of claims 1 to 7, wherein the direction of the first current signal is opposite to the direction of the second current signal.
9. A drive signal corresponding to a first rotational vibration mode, a drive signal corresponding to a second rotational vibration mode, a first current signal corresponding to the first rotational vibration mode, and the second rotational vibration mode are applied to the two-dimensional vibrator. a second current signal corresponding to a vibration mode is input;
   A first detection unit detects the amplitude and phase of a component corresponding to the first rotational vibration mode from the signal output from the two-dimensional oscillator,
   A second detection unit detects the amplitude and phase of a component corresponding to the second rotational vibration mode from the signal output from the two-dimensional oscillator,
   a first oscillation circuit outputting a first resonance frequency corresponding to the first rotational vibration mode based on the phase detected by the first detection unit;
   a second oscillation circuit outputting a second resonance frequency corresponding to the second rotational vibration mode based on the phase detected by the second detection unit;
   A magnetic field detection method, wherein a magnetic field detection unit detects a magnetic field based on the first resonance frequency and the second resonance frequency.

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