JP7614666B2 - Magnetic field sensor and magnetic field detection method - Google Patents

Description

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 detection method using a gyro device having a single (one) mode-matched (resonant frequencies of two orthogonal axes are the same) two-dimensional oscillator.

Magnetic field sensors (also called magnetic sensors) for detecting the magnitude and direction of a magnetic field have been proposed. For example, the following Patent Document 1 discloses a magnetic field sensor that uses a semiconductor element such as a Hall sensor.

Special table 2016-510116 publication

Magnetic field sensors using semiconductor elements such as Hall sensors, as described in Patent Document 1, are temperature dependent and therefore not robust against temperature changes. For this reason, there is a risk that the accuracy of measuring the magnetic field may deteriorate due to temperature changes. Therefore, a magnetic field sensor that is robust against temperature changes is desired.

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

One aspect of the present invention is
a single two-dimensional vibrator that 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 further receives an input of a first current signal corresponding to the first rotational vibration mode and a second current signal corresponding to the second rotational vibration mode;
a first detection unit that detects an amplitude and a phase of a component corresponding to a first rotational vibration mode from a signal output from the two-dimensional oscillator;
a second detection unit that detects the amplitude and phase of a component corresponding to a second rotational vibration mode from a signal output from the two-dimensional oscillator;
a first oscillation circuit that outputs a first resonant frequency corresponding to a first rotational vibration mode based on the phase detected by the first detection unit;
a second oscillation circuit that outputs a second resonant frequency corresponding to a second rotational vibration mode based on the phase detected by the second detection unit;
The magnetic field sensor includes a magnetic field detection unit that detects a magnetic field based on the difference between the first resonant frequency and the second resonant frequency.

Another aspect of the present invention is
A drive signal corresponding to a first rotational vibration mode and a drive signal corresponding to a second rotational vibration mode, and a first current signal corresponding to the first rotational vibration mode and a second current signal corresponding to the second rotational vibration mode are input to the two-dimensional vibrator;
a first detection unit detects an amplitude and a phase of a component corresponding to a first rotational vibration mode from a signal output from the two-dimensional oscillator;
a second detection unit detects an amplitude and a phase of a component corresponding to a second rotational vibration mode from a signal output from the two-dimensional oscillator;
a first oscillation circuit outputs a first resonant frequency corresponding to a first rotational vibration mode based on the phase detected by the first detection unit;
a second oscillation circuit outputs a second resonant frequency corresponding to a second rotational vibration mode based on the phase detected by the second detection unit;
The magnetic field detection method includes a magnetic field detection unit that detects a magnetic field based on a difference between a first resonant frequency and a second resonant 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 temperature changes. Note that the effects exemplified in this specification should not be construed as limiting the content of the present invention.

FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to be referred to when explaining the technology on which the present invention is based. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. FIG. 1 is a diagram to which reference is made when describing an overview of one embodiment. 1 is a diagram for explaining a configuration example of a two-dimensional oscillator according to an embodiment; 1 is a block diagram showing an example of the configuration of a magnetic field sensor according to an embodiment; FIG. 11 is a diagram for explaining an example of an effect obtained by an embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The description will be made in the following order.
<Technology on which the present invention is based>
<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.

<Technology on which the present invention is based>
The inventor of this patent application has previously proposed a gyro device and a method for controlling the gyro device. The proposed content has been published as a patent document, JP 2020-169819 A. The content described in the patent document can be applied to this patent application. In general, the present invention is a magnetic field sensor that improves the gyro device described in the above patent document, that is, a magnetic field sensor that applies the principle of an FM (Frequency Modulation) gyroscope. Therefore, in order to facilitate understanding of the present invention, the content described in the above patent document, which is the premise of the present invention, will be briefly described. Note that the present invention does not necessarily need to include all of the content described in the above patent document, and may be an embodiment in which a part of it is used.

First, a general gyro device (gyroscope) will be described. In the following description, a small vibration type gyro device using MEMS (Micro Electro Mechanical Systems) will be described as an example. The gyro device detects the angular velocity of rotation (hereinafter, appropriately referred to as the rotational angular velocity). There are several known methods for detecting the rotational angular velocity _Ωz . As a first method, a method called AM (Amplitude Modulation) mode is known. In the AM mode, when vibration is applied in the drive axis (e.g., X-axis) direction, the angular velocity is obtained by measuring the amplitude (displacement) in the sense axis (e.g., Y-axis) direction that changes due to the Coriolis force. 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 resonant 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 the measurement is performed at a frequency far from the resonant frequency, there are problems such as a decrease in sensitivity. Furthermore, in the AM mode, there is a theoretical trade-off between sensitivity and measurement bandwidth, and it is impossible to achieve both high sensitivity and a wide bandwidth.

The second method is called force rebalancing, in which feedback control is applied so that the amplitude of the AM mode in the sense axis direction is always zero, and the rotational angular velocity is obtained from the magnitude of the feedback signal. In this case, a transducer in which the resonant frequencies of the drive axis and sense axis are matched (mode matched) can be used. However, there are problems such as the scale factor (magnitude of output relative to rotational angular velocity) fluctuating due to temperature, etc.

In consideration of the problems with the first and second methods described above, the embodiment described below employs driving of the gyro device in FM mode. The FM mode has the advantages of being more accurate and stable in sensitivity (scale factor), superior temperature characteristics in principle, and unlimited dynamic range compared to other methods.

Here, the basic principle of the FM mode will be explained. The principle of the FM mode itself is well known, so only a brief explanation will be given here. The FM mode gyro is composed of an oscillator (also called a resonator or resonator) that vibrates in two orthogonal (independent) axial directions. In the FM mode, an oscillator with the same resonance frequency on each axis (mode match) is used. In this state, when a rotational angular velocity is applied to the oscillator, it is known that the relationship expressed by the following formula 1 holds. In formula 1, λ represents the resonance frequency, ω represents the resonance frequency when no rotation is applied (the two axes have the same resonance frequency because of mode match), and _Ωz represents the rotational angular velocity applied to the oscillator.

Note that the vibrations mentioned below are not limited to linear vibrations (e.g., X-direction, Y-direction), and any vibration can be used as long as it is an orthogonal vibration mode that matches the mode. For example, in the case of a ring-type resonator, as shown in Figures 1 and 2, two orthogonal vibrations do not necessarily result in simple linear vibrations, but if the displacement state in each vibration mode is expressed in mode coordinates (generalized coordinates), it can be treated exactly the same as linear vibration. In the following, including these mode coordinates (generalized coordinates), one mode will be called the "X-axis (or X-direction)" and the mode perpendicular to this will be called the "Y-axis (or Y-direction)" (Note that modes 1 and 2 in Figures 1 and 2 show a state in which they are mathematically or vibrationally orthogonal).

The following equation 2 is derived from equation 1.

That is, as shown in Equation 2, when no rotation is applied, the resonant frequencies in the X-axis and Y-axis directions are the same, that is, mode-matched, but when rotation is applied, the resonant frequency λ splits into ω+ _Ωz and ω- _Ωz . If these two resonant frequencies are _λ1 and _λ2 , the difference (deviation) between the resonant frequencies λ1 _{and λ2} is proportional to the rotational angular velocity _Ωz , so if the two resonant frequencies _λ1 and _λ2 are detected, the rotational angular velocity _Ωz can be obtained using Equation 3 below.

Here, 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). In other words, when rotation is applied to a mode-matched oscillator, the natural vibration mode is not linear (vibration in the X or Y direction alone) but becomes rotational vibration (two-dimensional vibration in which the phase of the vibration in the X and Y directions is shifted by ±90 degrees (°)). Note that the actual rotation of the oscillator is a superposition of these CW and CCW modes.

"Methods for detecting components of each mode"
The FM mode has been described above. For example, control is performed to excite one oscillator (hereinafter, appropriately referred to as a two-dimensional oscillator) that is mode-matched to two dimensions in the above-mentioned FM mode. Therefore, in order to obtain the rotational angular velocity _Ωz , it is necessary to independently detect the CW mode (first rotational vibration mode) component and the CCW mode (second rotational vibration mode) component contained in the rotational vibration (output) of the two-dimensional oscillator. Therefore, next, a method of detecting the CW mode component and the CCW mode component separately from the output of the two-dimensional oscillator will be described.

Figure 3 is a diagram for explaining a general synchronous detection method. A signal having a certain amplitude and phase is input as an input signal (Signal) SI. The input signal SI is split and input to each of multipliers (mixers) 1 and 3. In the synchronous detection method, two signals with a phase shift of 90 degrees are used as reference signals, and these reference signals are multiplied by separate multipliers 1 and 3, and then filtered to obtain a demodulated output. For example, a cosine wave and a sine wave are used as reference signals, and the input signal SI is multiplied by the cosine wave by multiplier 1, and the input signal SI is multiplied by the sine wave by multiplier 3.

The signal output from multiplier 1 is input to LPF (Low Pass Filter) 2 and filtered. As a result of filtering by LPF 2, only components that have the same frequency and phase as the reference signal (cosine wave in this example) are output from LPF 2.

Meanwhile, the signal output from multiplier 3 is input to LPF 4 and filtered. As a result of filtering by LPF 4, only components that have the same frequency and phase as the reference signal (sine wave in this example) in multiplier 3 are output from LPF 4.

The input signal SI is demodulated using the 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.

This synchronous detection method is developed and applied to detect the CW mode components and CCW mode components. In the following explanation, we will explain an example of detecting only the CW mode components from a signal that combines CW mode and CCW mode generated in a two-dimensional transducer, but the CCW mode components can be detected by similar processing.

Figure 4 is a diagram for explaining a method for detecting CW mode components from an input signal SI. A signal output from a 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 notation including components in the X and Y directions, as shown in the figure.

The input signal SI is branched and input to each of multipliers 1 and 3. Signals CW-I (In phase) and CW-Q (Quadrature Phase) are used as reference signals, and multiplier 1 multiplies the input signal SI by the signal CW-I, while multiplier 3 multiplies the input signal SI by the signal CCW-I. As symbolically shown in Figure 4, signals CW-I and CW-Q have the same amplitude, frequency, and direction of rotation, but are out of phase with each other by 90 degrees.

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

Figure 5 is a diagram for explaining a detailed configuration example of the above-mentioned multipliers 1 and 3. Multiplier 1 includes, for example, multiplier 1a, multiplier 1b, and adder 1c. Multiplier 3 includes, for example, multiplier 3a, multiplier 3b, and adder 3c.

As described above, in the case of a two-dimensional oscillator, signals (amplitudes) in the X- and Y-axis directions (hereinafter referred to as signals SIX and SIY as appropriate) are input to multiplier 1 as input signal SI. Multiplier 1a multiplies signal SIX by the X-axis component of signal CW-I, and multiplier 1b multiplies signal SIY by the Y-axis component of signal CW-I. Adder 1c adds the outputs of multipliers 1a and 1b and outputs the result to LPF 2.

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

The above-mentioned method allows the detection of the CW mode components contained in the output of the two-dimensional oscillator, which will be described in more detail with reference to Figs. 6 to 9. 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 contains only the component of the signal CW-I, the output waveform of the multiplier 1a will be the waveform WA1a, and the output waveform of the multiplier 1b will be the waveform WA2a. The waveform of the signal obtained by adding the outputs of the multipliers by the adder 1c will be the waveform WA3a. When this signal waveform is passed through the LPF 2, the filtering process by the LPF 2 is equivalent to the process of obtaining the average, so the waveform of the obtained signal will be the waveform WA4a (DC component) similar to the waveform WA3a. In other words, if the input signal SI contains a component of the signal CW-I, that component can be detected by detection using the signal CW-I.

The example shown in Figure 7 is an example of detection using signal CW-I as a reference signal, but assumes that input signal SI is composed only of signal CW-Q, which is 90 degrees out of phase with signal CW-I. In this case, the output waveform of multiplier 1a is waveform WA1b, and the output waveform of multiplier 1b is waveform WA2b. The signal obtained by adding the outputs of these waveforms in adder 1c is 0 as shown, and therefore the output of LPF2 is also 0 as shown.

The example shown in Figure 8 is an example of detection using signal CW-I as a reference signal, assuming that the input signal SI contains only components of signal CCW-I, which has a counterclockwise rotation direction different from that of signal CW-I. In this case, the output waveform of multiplier 1a is waveform WA1c, and the output waveform of multiplier 1b is waveform WA2c. The waveform of the signal obtained by adding the outputs of each multiplier by adder 1c is waveform WA3c, which is symmetrical about 0. When the signal of waveform WA3a is passed through LPF2, the output becomes 0 as shown in the figure.

The example shown in Figure 9 is an example of detection using signal CW-I as a reference signal, but assumes that input signal SI is a counterclockwise signal with a different rotation direction from signal CW-I, and contains only components of signal CCW-Q that is 90 degrees out of phase with signal CCW-I. In this case, the output waveform of multiplier 1a is waveform WA1d, and the output waveform of multiplier 1b is waveform WA2d. The waveform of the signal obtained by adding the outputs of each multiplier by adder 1c is waveform WA3d, which is symmetrical about 0. When this signal of waveform WA3d is passed through LPF2, the output becomes 0 as shown in the figure.

In other words, if any two-dimensional vibration occurring within a two-dimensional oscillator (represented by a linear combination of CW-I, CW-Q, CCW-I, and CCW-Q) is synchronously detected using signal CW-I as the reference signal, only the component of signal CW-I contained in the output signal of the two-dimensional oscillator will be obtained. This also applies to the components detected when other signals are used as the reference signal. The above information can be summarized as shown in Table 1 below.

As shown in Table 1, if the output of the two-dimensional oscillator contains a CW-Q signal component, the reference signal can be detected as the CW-Q signal, while the output of other signal components will be 0. If the output of the two-dimensional oscillator contains a CCW-I signal component, the reference signal can be detected as the CCW-I signal, while the output of other signal components will be 0. If the output of the two-dimensional oscillator contains a CCW-Q signal component, the reference signal can be detected as the CCW-Q signal, while the output of other signal components will be 0. In other words, for example, if two detectors are provided and the reference signals in each detector are set to a combination of the CW-I and CW-Q signals, and a combination of the CCW-I and CCW-Q signals, respectively, the CW mode components and CCW mode components can be detected independently from the output of the two-dimensional oscillator.

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

Although not shown in the figure, the gyro device 10 may be equipped with a DA (Digital to Analog) converter and an AD (Analog to Digital) converter, and each process may be performed 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 generating unit 20 into an analog format. The AD converter is provided, for example, in the rear of the amplifiers 62a and 62b, and configured to convert the analog signal output from the two-dimensional vibrator 15 into a digital format.

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

The drive signal generating unit 20 supplies the two-dimensional vibrator 15 with a drive signal obtained by multiplexing a drive signal (first drive signal) corresponding to the CW mode and a drive signal (second drive signal) corresponding to the CCW mode. The two-dimensional vibrator 15 is excited by the drive signal supplied from the drive signal generating unit 20. In this example, a cosine wave (hereinafter referred to as a cos _cw signal) is used as the drive signal in the X-axis direction corresponding to the CW mode, and a -sine wave (hereinafter referred to as a -sin _cw signal) is used as the drive signal in the Y-axis direction. Note that the drive signal does not necessarily have to be a cosine wave or a -sine wave as long as the Y-direction signal is 90 degrees out of phase with the X-direction signal. In addition, a -cosine wave (hereinafter referred to as a -cos _CCW signal) is used as the drive signal in the X-axis direction corresponding to the CCW mode, and a -sine wave (hereinafter referred to as a -sin _CCW signal) is used as the drive signal in the Y-axis direction. In addition, the drive signal does not necessarily have to be a -cosine wave or -sine wave as long as the Y-direction signal is delayed in phase by 90 degrees from the X-direction signal. The drive signal generating unit 20 generates a drive signal corresponding to the CW mode based on a signal fed back from the first PLL circuit 40a, and generates a drive signal corresponding to the CCW mode based on a signal fed back from the second PLL circuit 40b. The drive signal generating unit 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 30a detects the amplitude _rcw and phase _θcw of the CW component included in the output of the two-dimensional oscillator 15. The first detector 30a will be described in detail later.

The first PLL circuit 40a includes a phase comparator 41a, a PID (Proportional Integral Differential) control unit 42a, and an oscillator 43a that can change the oscillation frequency of a VCO (Voltage Controlled Oscillator) or NCO (Numerical Controlled Oscillator). Although detailed illustration is omitted to avoid complicating the illustration, the output of the first PLL circuit 40a (which may be all of the output or a part of the output) is configured to be fed back to each of the drive signal generating unit 20 and the first detection unit 30a.

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

The second detection unit 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 unit 42b, and an oscillator 43b that can change the oscillation frequency of the VCO, NCO, etc. Although detailed illustration is omitted to prevent the illustration from becoming complicated, the output of the second PLL circuit 40b (which may be all of the output or a part of the output) is configured to be fed back to each of the drive signal generation unit 20 and the second detection unit 30b.

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

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 a signal output from the two-dimensional oscillator 15 is branched and input, an LPF 33a that performs filtering on the output of the detector 31a, an LPF 34a that performs filtering on the output of the detector 32a, and an amplitude/phase detection unit 35a that detects the amplitude _rcw and phase _θcw of the CW component included in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPFs 33a and 34a.

Detector 31a includes a multiplier 310a to which the component in the X-axis direction of the output from the two-dimensional oscillator 15 is input, a multiplier 311a to which the component in the Y-axis direction of the output from the two-dimensional oscillator 15 is input, and an adder 312a that adds the outputs of multipliers 310a and 311a. Detector 32a includes a multiplier 320a to which the component in the X-axis direction of the output from the two-dimensional oscillator 15 is input, a multiplier 321a to which the component in the Y-axis direction of the output from the two-dimensional oscillator 15 is input, and an adder 322a that adds the outputs of 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 cosine signal, the CW-Q component in the X-axis direction is a cosine signal, and the CW-Q component in the Y-axis direction is a -sine signal.

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 a signal from the two-dimensional oscillator 15 is branched and input, an LPF 33b that performs filtering on the output of the detector 31b, an LPF 34b that performs filtering on the output of the detector 32b, and an amplitude/phase detection unit 35b that detects the amplitude r _CCW and phase θ _CCW of the CCW component included in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPFs 33b and 34b.

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

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

Next, an operation example of the gyro device 10 will be described with reference to Figs. 10 to 12. The drive signal generating unit 20 generates a drive signal for the two-dimensional vibrator 15. After the _{cos cw} signal and the -sin _cw signal are multiplied by the multipliers 201 and 202, respectively, which are fed back from the PID control unit 52a, the output signal from the multiplier 201 is supplied to the adder 205, and the output signal from the multiplier 202 is supplied to the adder 206. After the -cos _CCW signal and the -sin _CCW signal are multiplied by the multipliers 203 and 204, respectively, which are fed back from the PID control unit 52b, the output signal from the multiplier 203 is supplied to the adder 205, and the output signal from the multiplier 204 is supplied to the adder 206. The adder 205 adds the output signal from the multiplier 201 and the output signal from the multiplier 203, and outputs the result. The output signal from the adder 205 is amplified by the amplifier 61a with an appropriate amplification factor, and then input as input _Xd to the two-dimensional oscillator 15. Meanwhile, the adder 206 adds the output signal from the multiplier 202 and the output signal from the multiplier 204, and outputs the result. The output signal from the adder 206 is amplified by the amplifier 61b with an appropriate amplification factor, and then input as input _Yd to the two-dimensional oscillator 15.

The two-dimensional oscillator 15 is excited by the inputs _Xd and _Yd , and outputs _Xs and _Ys are obtained from the two-dimensional oscillator 15. The outputs _Xs and _Ys from the two-dimensional oscillator 15 are amplified by the amplifiers 62a and 62b with appropriate amplification factors, and then the output _Xs is branched and input to the first and second detection units 30a and 30b, respectively, and the output _Ys is branched and input to the first and second detection units 30a and 30b, respectively.

The first detection unit 30a detects the CW component included in the output of the two-dimensional oscillator 15. Specifically, the detector 31a in the first detection unit 30a performs detection using the signal CW-I, and performs filtering on the result using the LPF 33a to detect the CW-I component included in the output of the two-dimensional oscillator 15, and supplies the detection result to the amplitude and phase detection unit 35a. Also, the detector 32a in the first detection unit 30a performs detection using the signal CW-Q, and performs filtering on the result using 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 and phase detection unit 35a. The amplitude and phase detection unit 35a detects the amplitude _rcw and phase _θcw of the CW component included in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPF 33a and the LPF 34a. That is, as described above, by performing synchronous detection using each of the signals CW-I and CW-Q as a reference signal, it is possible to detect only the CW component included in the output of the two-dimensional oscillator 15.

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 with a set phase θ _cw,set (in the following description, θ _cw,set =90°), and the PID controller 42a executes control to set the phase θ _cw to 90°, i.e., the resonant frequency f _cw, based on the comparison result. The oscillator 43a is controlled by the output from the PID controller 42a, and the oscillator 43a outputs signals sin _cw and cos _cw with the resonant frequency f _cw . These signals are fed back to the input side, and control is performed to maintain the resonant frequency of the drive signal corresponding to the CW mode at the resonant frequency f _cw . In addition, the signals sin _cw and cos _cw are fed back to the first detector 30a, and based on this, signals CW-I and CW-Q are generated as reference signals. In this example, the relationships sin=sin _cw , cos=cos _cw , and −sin=−1*sin _cw hold between the signal that is fed back and the reference signal.

The amplitude _rcw obtained by the first detector 30a is supplied to the first AGC unit 50a. An amplitude comparator 51a in the first AGC unit 50a compares the amplitude _rcw with a predetermined first set value Rset _,cw , and a PID controller 52a executes control so that the amplitude _rcw becomes the predetermined first set value Rset _,cw based on the comparison result. An output from the PID controller 52a is fed back to the drive signal generator 20, and a 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 the system that detects the CCW component included 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 result is filtered by the LPF 33b to detect the CCW-I component included in the output of the two-dimensional oscillator 15, and the detection result is supplied to the amplitude and phase detection unit 35b. Also, 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 the detection result is supplied to the amplitude and phase detection unit 35b. The amplitude and phase detection unit 35b detects the amplitude r _CCW and phase θ _CCW of the CCW component included in the output signal of the two-dimensional oscillator 15 based on the outputs from the LPF 33b and the LPF 34b. That is, as described above, by synchronously detecting the signals CCW-I and CCW-Q as reference signals, it is possible to detect only the CCW component included in the output of the two-dimensional oscillator 15.

The phase θ _CCW obtained by the second detector 30b is supplied to the second PLL circuit 40b. A phase comparator 41b in the second PLL circuit 40b compares the phase θ _CCW with 90°, and a PID controller 42b executes control to set the phase θ _CCW to 0, i.e., the resonant frequency f _CW, based on the comparison result. An oscillator 43b is controlled by the output from the PID controller 42b, and the oscillator 43b outputs signals sin _CCW and cos _CCW that are in phase with each other, in other words, have the resonant frequency f _{CCW. The resonant frequency f CCW is} fed back to the input side, and control is performed to maintain the resonant frequency of the drive signal corresponding to the CCW mode at the resonant frequency f _CCW . In addition, the signals sin _CCW and cos _CCW are fed back to the second detector 30b, and based on this, signals CCW-I and CCW-Q are generated as reference signals. In this example, the following relationships hold between the fed back signal and the reference signal: -sin=sin _ccw , cos=cos _ccw , -cos=-1*cos _ccw .

The amplitude r _CCW obtained by the second detection unit 30b is supplied to the second AGC unit 50b. An amplitude comparator 51b in the second AGC unit 50b compares the amplitude r _CCW with a second set value R _set,CCW , and a PID control unit 52b executes control such that the amplitude r _CCW becomes the second set value R _set,CCW based on the comparison result. An output from the PID control unit 52b is fed back to the drive signal generation unit 20, and a gain is controlled so that the amplitude of the drive signal corresponding to the CCW mode is maintained at the second set value R _set,CCW .

Figure 13 is a schematic diagram showing the signal flow in the gyro device 10. The thick lines in Figure 13 indicate the signal flow. The CCW component included in the output of the two-dimensional oscillator 15 is cut by the first detection unit 30a, and only the CW component loops through one system (the upper system in Figure 13). The CW component included in the output of the two-dimensional oscillator 15 is cut by the second detection unit 30b, and only the CCW component loops through the other system (the lower system in Figure 13).

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

14 is a diagram showing an example of the configuration of the angular velocity detection unit 70. The angular velocity detection unit 70 includes, for example, a subtractor 71 and a multiplier 72. The angular velocity detection unit 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, subtracts the two resonance frequencies using the subtractor 71, and multiplies the result by a constant (1/2 in the case of an ideal oscillator with an angular gain of 1) using the multiplier 72. That is, the angular velocity detection unit 70 detects the rotational angular velocity _Ωz by performing a calculation similar to that of the above-mentioned Equation 3. The gyro device 10 can detect the rotational angle by integrating this rotational angular velocity _Ωz .

The gyro device 10 described above is composed of a single two-dimensional oscillator, which allows the device to be made smaller and eliminates the need to match the characteristics and operating environment of the oscillators as occurs when multiple oscillators are used. Furthermore, the components corresponding to CW and CCW modes can be detected independently from the output of the two-dimensional oscillator, and the rotational angular velocity can be detected from these detection results, and ultimately the rotation angle can be detected.

<One embodiment>
[overview]
In this embodiment, a magnetic field sensor (magnetic field sensor 1000) in which temperature dependency is cancelled is realized by improving the above-mentioned gyro device 10. First, the principle of the magnetic field sensor will be roughly described with reference to Figs.

Figure 15 shows the circular motion of the two-dimensional oscillator 15 in the above-mentioned CW mode, and Figure 16 is a schematic diagram showing the circular motion of the two-dimensional oscillator 15 in the above-mentioned CCW mode. In Figures 15 and 16 (as well as Figures 17 and 18), the two-dimensional oscillator 15 is shown diagrammatically by a circular mass and four springs (a pair of springs in each of the X and Y directions) that support the mass.

The two-dimensional oscillator 15 normally (when no magnetic field is applied) vibrates at the same frequency f ₀ in each rotational vibration mode because the spring constants in the x-axis and y-axis are equivalent, in other words, degenerate. If the frequency of the rotational motion in the CW mode is f _cw and the frequency of the rotational motion in the CCW mode is f _ccw , then f _cw = f ₀ and f _ccw = f ₀ hold. Note that f ₀ is a frequency determined by the mass and spring constant of the mass. Degeneracy means that many modes have the same energy (i.e., resonant frequency), and in this example, the resonant frequency of the two-dimensional oscillator 15 is the same in each rotational vibration mode in the stationary coordinate system.

Here, as shown in FIG. 17, consider the case where there is a magnetic field ( _Bz ) during vibration in CW mode. A current i is passed through the two-dimensional oscillator 15 in synchronization with the vibration. Because of the presence of the magnetic field _Bz , passing the current i generates a Lorentz force F (F=I×BL). By synchronizing with the vibration, in other words, by passing the current i in the tangential direction of the rotation, as shown in FIG. 17, an inward Lorentz force F is always generated. Note that by changing the ratio of the magnitude of the current flowing in the X direction to the current flowing in the Y direction or the amount of current passed, it is possible to make the current flow equivalently in the tangential direction of the rotation.

The inward Lorentz force F is generated, which equivalently strengthens the restoring force of the spring. This increases the resonant frequency. This can be expressed as the following equation (4).

Also, as shown in FIG. 18, consider the case where a magnetic field (B _z ) is present during vibration in CCW mode. A current i is passed through the two-dimensional oscillator 15 in synchronization with the vibration. The direction of the current i passed in CCW mode is opposite to the direction of the current i passed in CW mode. Due to the presence of the magnetic field B _z , a Lorentz force F is generated when the current i is passed. By synchronizing with the vibration, in other words, by passing the current i in the tangential direction of the rotation, a Lorentz force F is always generated outward as shown in FIG. 18. Note that the current can be made to flow equivalently in the tangential direction of the rotation by changing the ratio of the magnitude of the current flowing in the X direction to the current flowing in the Y direction or the amount of current passed.

The generation of an outward Lorentz force F equivalently weakens the restoring force of the spring, which lowers the resonant frequency. This can be expressed as equation (5) below. Note that the direction of the Lorentz force may be the opposite to the above (i.e., an outward Lorentz force in CW mode, and an inward Lorentz force in CCW mode) as long as it acts in the opposite direction in CW mode and CCW mode.

The above changes can be expressed as equation (6) below.

As shown in formula (6), the degeneracy is broken by the presence of a magnetic field, and the frequency of vibration in each vibration mode becomes the one shown in formula (4) and formula (5). Here, f ₀ is dependent on temperature, 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 canceled. In addition, the current flowing through the two-dimensional oscillator 15 can be controlled. From the above, for example, the magnetic field can be measured by measuring the frequency difference and then removing the effect of the current i by calculation. As described above, the frequency difference is not affected by temperature changes, so that the magnetic field can be measured with high accuracy.

By the way, when the gyro device 10 is used as a magnetic field sensor, the magnetic field sensor also detects the angular velocity. When there is no magnetic field, the term kΩ, which is a frequency modulated by the angular velocity, appears (in the case of CW mode), as shown in the following equation (7).

When there is a magnetic field, it can be expressed by the above-mentioned equation (4), so the following equation (8) can be derived from equations (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).

The equation for Δf in equation (9) contains the angular velocity-dependent term 2kΩ and the term 2Δf(I,B) that depends on the magnetic field and current (a term that ultimately corresponds to the magnetic field itself through calculations). Figure 19 is a schematic diagram showing the spectrum of the waveforms corresponding to each term. The horizontal axis of Figure 19 indicates the signal frequency, and the vertical axis indicates the signal magnitude. The waveform that corresponds to the angular velocity-dependent term 2kΩ is waveform WA5, and the waveform that corresponds to the term 2Δf(I,B) that depends on the magnetic field and current is waveform WA6.

As shown in Fig. 19, the two waveforms generally overlap in the frequency domain, so that in this state, it is not possible to separate the angular velocity and the magnetic field, and it is not possible to detect both. Therefore, the magnitude of the controllable current i is modulated at a predetermined frequency. The predetermined frequency (the frequency of the modulation signal) is a frequency higher than the frequency of the angular velocity that is expected to be detected (e.g., 100 Hz). For example, the current i is modulated at a predetermined frequency _WB (i= _i0 sin( _WB , t)). Note that the first frequency and the second frequency may be the same or different.

As a result, the frequency fluctuation component due to the magnetic field (waveform WA6 in this example) is frequency-shifted to the higher frequency side, as shown diagrammatically in Figure 20. This can be expressed as the following equation (10).

The frequency fluctuation components due to the magnetic field can be detected by synchronous detection at frequency _WB . Since the magnitude of current i is known, only the magnetic field components can be detected by dividing by current i.

[An example of a two-dimensional oscillator]
Next, a two-dimensional oscillator 15A applicable to this embodiment will be described. The two-dimensional oscillator 15A is, for example, a two-dimensional oscillator 15 to which a configuration for passing a current is added. Fig. 21 shows an example of the configuration 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, there may be only one mass 151, but there may also be multiple masses 151. For example, the Q value can be increased by using four masses 151.

The two-dimensional oscillator 15A is a degenerate oscillator like the two-dimensional oscillator 15, and therefore has a symmetrical and equivalent configuration in each of the X and Y directions. This configuration generally includes a drive electrode, a shuttle connected to the mass 151 and driven by the drive electrode, and a sense electrode that detects the displacement of the shuttle.

For example, a drive electrode 151A is provided on the X+ side (the right side in Figure 21). The drive electrode 151A is connected to the shuttle 151B. When a voltage is applied to the comb-tooth electrode of the drive electrode 151A, the shuttle 151B is displaced, which also displaces the mass 151 connected to the shuttle 151B. The displacement of the shuttle 151B can be detected by detecting a change in electrostatic capacitance that occurs in the comb-tooth electrode of the sense electrode 151C. In addition, the shuttle 151B is provided with ports 151D and 151E for passing a current. For example, a control is performed to pass a current from port 151D to port 151E.

A drive electrode 152A is provided on the X-side (left side in Figure 21). The drive electrode 152A is connected to the shuttle 152B. When a voltage is applied to the comb-tooth electrode of the drive electrode 152A, the shuttle 152B is displaced, which also displaces the mass 151 connected to the shuttle 152B. The displacement of the shuttle 152B can be detected by detecting a change in electrostatic capacitance that occurs in the comb-tooth electrode of the sense electrode 152C. In addition, the shuttle 152B is provided with ports 152D and 152E for passing a current. For example, a control is performed to pass a current from port 152D to port 152E.

For example, a drive electrode 153A is provided on the Y+ side (upper side in Figure 21). Drive electrode 153A is connected to shuttle 153B. When a voltage is applied to the comb-tooth electrode of drive electrode 153A, shuttle 153B is displaced, which also displaces mass 151 connected to shuttle 153B. The displacement of shuttle 153B can be detected by detecting a change in electrostatic capacitance that occurs in the comb-tooth electrode of sense electrode 153C. In addition, shuttle 153B is provided with ports 153D and 153E for passing a current. For example, a control is performed to pass a current from port 153D to port 153E.

For example, a drive electrode 154A is provided on the Y-side (the lower side in Figure 21). The drive electrode 154A is connected to the shuttle 154B. When a voltage is applied to the comb-tooth electrode of the drive electrode 154A, the shuttle 154B is displaced, which also displaces the mass 151 connected to the shuttle 154B. The displacement of the shuttle 154B can be detected by detecting a change in electrostatic capacitance that occurs in the comb-tooth electrode of the sense electrode 154C. In addition, the shuttle 154B is provided with ports 154D and 154E for passing a current. For example, a control is performed to pass a current from port 154D to port 154E.

[Example of magnetic field sensor configuration]
Fig. 22 is a block diagram showing an example of the configuration of a magnetic field sensor (magnetic field sensor 1000) according to this embodiment. The magnetic field sensor 1000 includes, for example, all of the configurations of the gyro device 10 described above. Note that the same reference numerals are used for configurations that are the same or of the same quality as those of the gyro device 10, and duplicated descriptions are omitted as appropriate. Also, Fig. 22 shows only configurations that are closely related to the present invention, and illustrations of other configurations are omitted as appropriate.

The magnetic field sensor 1000 includes a two-dimensional vibrator 15A, a drive signal generating unit 20, a first detection unit 30a, a second detection unit 30b, a first PLL circuit 40a, and a second PLL circuit 40b. The magnetic field sensor 1000 further includes a first current signal generating unit 80a, a second current signal generating unit 80b, a signal source 82, a mix unit 85, an adder 86, a magnetic field detection unit 91, and an LPF 92 as an angular velocity detection unit.

The first current signal generating unit 80a generates a first current signal corresponding to the CW mode. The first current signal generating unit 80a has a first current signal converting unit 81a, a first gain modulating unit 82a, and a multiplier 83a. The first current signal converting unit 81a converts a signal (e.g., sin _cw , cos _cw of a resonant frequency f _cw ) output from the oscillator 43a of the first PLL circuit 40a into a current. The first gain modulating unit 82a generates a signal for amplitude modulation from a predetermined frequency signal (e.g., a sine wave signal of 100 Hz or more) generated by the signal source 82. This signal is multiplied by the current signal by the multiplier 83a to provide modulation, and the first current signal is generated. The current signal converting unit 81a and the multiplier 83a may be in the reverse order.

The second current signal generating unit 80b generates a second current signal corresponding to the CCW mode. The second current signal generating unit 80b has a second current signal converting unit 81b, a second gain modulating unit 82b, a multiplier 83b, and an inverting circuit 84. The second current signal converting unit 81b converts a signal (e.g., sin _ccw , cos _ccw of the resonant frequency f _cw ) output from the oscillator 43b of the second PLL circuit 40b into a current. The inverting circuit 84 inverts the current signal output from the second current signal converting unit 81b. As a result, the direction of the second current signal generated by the second current signal generating unit 80b becomes opposite to the direction of the first current signal. The second gain modulating unit 82b generates a signal for amplitude modulation from a predetermined frequency signal (e.g., a sine wave signal of 100 Hz or more) generated by the signal source 82. This signal is multiplied by the current signal by the multiplier 83b to provide modulation, and the second current signal is generated. The current signal converter 81b, the multiplier 83b, and the inverter circuit 84 may be arranged in a reverse order.

The mixer 85 mixes (multiplexes) the first current signal generated by the first current signal generator 80a and the second current signal generated by the second current signal generator 80b. The first current signal and the second current signal mixed by the mixer 85 are input to the two-dimensional oscillator 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. This provides Δf, which is the difference between the resonance frequency f _cw and the resonance frequency f _ccw . Δf is input to the magnetic field detector 91 and the second LPF 92.

The magnetic field detection unit 91 detects a magnetic field based on the resonant frequency f _cw and the resonant frequency f _ccw . The magnetic field detection unit 91 has a multiplier 91a and a first LPF 91b. The multiplier 91a multiplies Δf by a modulated signal from the signal source 82. The first LPF 91b performs a filtering process on the output of the multiplier 91a to pass only low-frequency signals (below the cutoff frequency). The magnetic field is detected by performing an appropriate calculation (e.g., a calculation to remove a current component) for detecting the magnetic field at a stage subsequent to the first LPF 91b.

The second LPF 92 performs a filtering process on the output of the adder 86, passing only low-frequency signals (below the cutoff frequency). This extracts only the signal components corresponding to the angular velocity. An appropriate calculation (for example, a calculation similar to the calculation performed by the angular velocity detection unit 70 in the gyro device 10 described above) is performed on the signal that has passed through the second LPF 92, thereby detecting the angular velocity.

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

The first detection unit 30a detects the phase θ _cw by performing the above-mentioned processing. The phase θ _cw is supplied to the first PLL circuit 40a. The PID control unit 42a executes control so that the phase θ _cw becomes the resonance frequency f _cw based on the comparison result by the phase comparator 41a. The resonance frequency f _cw output from the PID control unit 42a is supplied to the adder 86. The signal output from the oscillator 43a is fed back to the drive signal generation unit 20 and used to generate the drive signal. In addition, the signal output from the oscillator 43a is converted into a current signal by the first current signal conversion unit 81a. The converted current signal is amplitude modulated by the first gain modulation unit 82a and the multiplier 83a by the signal generated by the signal source 82, and the first current signal is generated. The second current signal is generated by performing the same processing in the CCW loop. The first current signal and the second current signal are mixed by the mix unit 85 and then input to the two-dimensional vibrator 15A.

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

The signal generated by the signal source 82 is multiplied by Δf by the multiplier 91a, so that the signal of the magnetic field component is shifted to the lower frequency side (the signal of the angular velocity component is shifted to the higher frequency side). Then, the signal of the magnetic field component shifted to the lower frequency side is detected by the first LPF 91b, and the magnetic field is detected using the signal of the detected magnetic field component.

In addition, the second LPF 92 detects the signal of the low-frequency angular velocity component for Δf, and the angular velocity is detected using the detected angular velocity component signal.

[Effects obtained by this embodiment]
As described above, according to the present embodiment, it is possible to provide a sensor that can detect not only angular velocity but also magnetic field. For example, the detection results of acceleration and angular velocity can be corrected by the sensing results of the magnetic field sensor. Since it is not necessary to add a magnetic field sensor as a separate device, the cost of the sensor can be reduced, and further, the sensor can be made smaller.

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

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

Figure 23C is a graph showing the results of Figure 23B on a log scale. As shown in Figure 23C, it can be seen that the results are linear over a wide range (in this example, a range of six digits). 1 nT (nanotesla) corresponds to a change of about 1 μHz. In the case of an FM gyro, a change of 1°/hr corresponds to 0.77 μHz. With an FM gyro, stability of about 1°/h is obtained. In other words, this shows that it is possible to adequately detect a magnetic field with stability of nT or less. According to this embodiment, a magnetic field sensor can be realized that is smaller than the geomagnetic field 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.

The signal generated by the signal source 82 may be not only a sine wave of a single frequency, but also other methods, such as a spectrum spread technique using a wideband signal. That is, the gain may be spread with a predetermined spreading code and then despread in a later stage to separate the magnetic field component signal and the angular velocity component signal.

The present invention is not limited to any specific method, such as shape or excitation method (electrostatic, electromagnetic, piezoelectric, etc.), as long as the vibrator is mode-matched in two dimensions.

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

The magnetic field sensor may be configured to include other circuit elements, etc., as long as the effects of the present invention are achieved. In addition, some of the processing in the magnetic field sensor may be performed by other devices, cloud servers, etc. In addition, the present invention may be configured as a sensor that detects only a magnetic field without detecting angular velocity.

The magnetic field sensor of the present invention may be incorporated into and used in other devices (e.g., various electronic devices such as game machines, imaging devices, smartphones, mobile phones, personal computers, etc., as well as moving objects such as automobiles, trains, airplanes, helicopters, small flying objects, space equipment, etc., robots, etc.).

The configurations, methods, steps, shapes, materials, and values given in the above-mentioned embodiments are merely examples, and different configurations, methods, steps, shapes, materials, and values may be used as necessary. Furthermore, the present invention can be realized by an apparatus, a method, or a system (such as a cloud system) consisting of multiple apparatuses, and the matters described in the multiple embodiments and variations can be combined with each other as long as no technical contradiction occurs.

10... Gyro device 15, 15A... Two-dimensional vibrator 30a... First detection unit 30b... Second detection unit 40a... First PLL circuit 40b... Second PLL circuit 42a, 42b... PID control unit 80a... First current signal generation unit 81a... First current signal conversion unit 82a... First gain modulation unit 83a... Multiplier 80b... Second current signal generation unit 81b... Second current signal conversion unit 82b... Second gain modulation unit 83b... Multiplier 91... Magnetic field detection unit 91a... Multiplier 91b... First LPF
92...Second LPF
1000...magnetic field sensor
CW: First rotational vibration mode
CCW: Second rotational vibration mode

Claims (8)

a single two-dimensional vibrator that 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 further receives a first current signal corresponding to the first rotational vibration mode and a second current signal corresponding to the second rotational vibration mode;
a first detection unit that detects an amplitude and a phase of a component corresponding to the first rotational vibration mode from a signal output from the two-dimensional oscillator;
a second detection unit that detects an amplitude and a phase of a component corresponding to the second rotational vibration mode from a signal output from the two-dimensional oscillator;
a first oscillation circuit that outputs a first resonant 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 resonant frequency corresponding to the second rotational vibration mode based on the phase detected by the second detection unit;
a magnetic field detection unit that detects a magnetic field based on a difference between the first resonant frequency and the second resonant frequency. 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 resonant frequency and the second resonant frequency. 3. The magnetic field sensor according to claim 2, further comprising a drive signal generating unit that generates a first drive signal corresponding to the first rotational vibration mode based on a signal fed back from the first oscillation circuit, and further generates a second drive signal corresponding to the second rotational vibration mode based on a signal fed back from the second oscillation circuit. a first current signal generating unit that generates the first current signal;
a second current signal generating unit that generates the second current signal,
the first current signal generating unit converts a signal fed back from the first oscillation circuit into a current signal and generates the first current signal by modulating the current signal;
The magnetic field sensor according to claim 3 , wherein the second current signal generating section converts a signal fed back from the second oscillation circuit into a current signal, and generates the second current signal by modulating the current signal. The magnetic field sensor according to claim 4 , wherein a frequency of the modulated signal is set to a value greater than a frequency of the angular velocity assumed to be detected by the angular velocity detection unit. The magnetic field sensor according to claim 2 , wherein the angular velocity detection unit detects the angular velocity based on a difference between the first resonant frequency and the second resonant frequency. The magnetic field sensor according to claim 1 , wherein the first current signal has a direction opposite to that of the second current signal. a drive signal corresponding to a first rotational vibration mode and a drive signal corresponding to a second rotational vibration mode, and a first current signal corresponding to the first rotational vibration mode and a second current signal corresponding to the second rotational vibration mode are input to a two-dimensional vibrator;
a first detection unit detects an amplitude and a phase of a component corresponding to the first rotational vibration mode from a signal output from the two-dimensional oscillator;
a second detection unit detects an amplitude and a phase of a component corresponding to the second rotational vibration mode from a signal output from the two-dimensional oscillator;
a first oscillation circuit outputs a first resonant frequency corresponding to the first rotational vibration mode based on the phase detected by the first detection unit;
a second oscillation circuit outputs a second resonant frequency corresponding to the second rotational vibration mode based on the phase detected by the second detection unit;
A magnetic field detection method, comprising: a magnetic field detection unit detecting a magnetic field based on a difference between the first resonant frequency and the second resonant frequency.

Images