Gyro sensor

Abstract

A gyro sensor according to the present invention comprises a vibrator, a drive electrode, a detection electrode, a detection feedback electrode, an adjustment electrode, a drive circuit, a detection circuit, a detection feedback circuit, a tone signal generation circuit, and an adjustment circuit. The detection circuit outputs an angular velocity signal on the basis of a detection signal that is outputted from the detection electrode. The detection feedback circuit outputs a feedback signal that is based on the angular velocity signal to the detection feedback electrode. The adjustment circuit controls the resonance frequency of the vibrator. The detection feedback circuit superimposes a tone signal on the feedback signal. The adjustment circuit outputs an adjustment signal that corresponds to the tone signal to the adjustment electrode.

Description

Gyro sensor

[0001] The present disclosure relates to a gyro sensor, and more particularly to a gyro sensor including a vibrator.

[0002] Conventionally, there is known a gyroscope that realizes a mode-matched state in which angular velocity detection sensitivity is maximized by controlling the bias voltage so that the intensity of the signal output (zero-rate output) when no angular velocity is applied is maximized (see Patent Document 1).

[0003] US Patent Application Publication No. 2009 / 0064781

[0004] In a gyroscope (gyro sensor) such as that described in Patent Document 1, there is a problem in that when an angular velocity is applied to the gyroscope, the gyroscope cannot be brought into a mode-matched state.

[0005] A gyro sensor according to one aspect of the present disclosure includes a vibrator, multiple electrodes, and a control unit. The multiple electrodes include a drive electrode, a detection electrode, a detection feedback electrode, and an adjustment electrode, and are arranged to face the vibrator to form a capacitance between the vibrator and the multiple electrodes. The control unit is electrically connected to the multiple electrodes. The control unit includes a drive circuit, a detection circuit, a detection feedback circuit, a tone signal generation circuit, and an adjustment circuit. The drive circuit outputs a drive signal to the drive electrode that induces a drive vibration of the vibrator. The detection circuit outputs an angular velocity signal indicating the angular velocity based on a detection signal output from the detection electrode that detects a detection vibration generated in the vibrator when the drive vibration is induced by an angular velocity applied to the vibrator. The detection feedback circuit outputs a feedback signal based on the angular velocity signal output from the detection circuit to the detection feedback electrode. The tone signal generation circuit outputs a tone signal having a frequency lower than the frequency of the drive signal to the detection feedback circuit. The adjustment circuit outputs an adjustment signal to the adjustment electrode that controls the resonant frequency of the vibrator. The detection feedback circuit superimposes the tone signal on the feedback signal and outputs the superimposed tone signal to the detection feedback electrode, and the adjustment circuit outputs the adjustment signal to the adjustment electrode according to the tone signal superimposed on the detection signal via the feedback signal output to the detection feedback electrode.

[0006] According to the present disclosure, it is possible to provide a gyro sensor that can be brought into a mode-matched state regardless of whether an angular velocity is applied or not.

[0007] Fig. 1 is a schematic block diagram of a gyro sensor according to an embodiment of the present disclosure. Fig. 2 is a waveform diagram of a feedback signal output by a detection feedback circuit included in the gyro sensor. Fig. 3 is a waveform diagram of a first demodulation signal output by a first demodulation circuit included in the gyro sensor. Fig. 4 is a waveform diagram of a second demodulation signal output by a second demodulation circuit included in the gyro sensor. Fig. 5A is a schematic block diagram of a gyro sensor according to a first modification. Fig. 5B is a schematic block diagram of another gyro sensor according to the first modification. Fig. 6 is a schematic block diagram of a gyro sensor according to a second modification.

[0008] A gyro sensor 1 according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the embodiment and modified examples described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiment and modified examples. Various modifications other than the embodiment and modified examples are possible depending on the design, etc., as long as they do not deviate from the technical concept of the present disclosure.

[0009] (1) Overview First, a gyro sensor 1 according to this embodiment will be described with reference to FIG.

[0010] The gyro sensor 1 is a sensor that detects an angular velocity applied from the outside.

[0011] The gyro sensor 1 includes a vibrator 2 , a plurality of electrodes 3 , and a control unit 4 .

[0012] The plurality of electrodes 3 include a drive electrode 31 , a detection electrode 32 , a detection feedback electrode 33 and an adjustment electrode 34 , and are arranged to face the vibrator 2 to form a capacitance between them.

[0013] The control unit 4 is electrically connected to the plurality of electrodes 3 .

[0014] The control unit 4 includes a drive circuit 41 , a detection circuit 42 , a detection feedback circuit 43 , a tone signal generation circuit 44 , and an adjustment circuit 45 .

[0015] The drive circuit 41 outputs a drive signal S1 to the drive electrode 31 to induce drive vibration of the vibrator 2 .

[0016] The detection circuit 42 outputs an angular velocity signal S4 indicating the angular velocity based on the detection signal S3 output from the detection electrode 32 that detects the detected vibration. The detected vibration is vibration generated in the vibrator 2 in a state in which drive vibration is induced by the angular velocity applied to the vibrator 2.

[0017] The detection feedback circuit 43 outputs a feedback signal S10 based on the angular velocity signal S4 output from the detection circuit 42 to the detection feedback electrode 33.

[0018] The tone signal generating circuit 44 outputs to the detection feedback circuit 43 a tone signal S6 having a frequency f3 lower than the frequency f1 of the drive signal S1.

[0019] The adjustment circuit 45 outputs an adjustment signal S13 for controlling the resonance frequency f2 of the vibrator 2 to the adjustment electrode 34.

[0020] The detection feedback circuit 43 superimposes the tone signal S6 on the feedback signal S10 and outputs the superimposed signal to the detection feedback electrode 33.

[0021] The adjustment circuit 45 outputs an adjustment signal S13 to the adjustment electrode 34 via a feedback signal S10 output to the detection feedback electrode 33, the adjustment signal S13 corresponding to the tone signal S6 superimposed on the detection signal S3.

[0022] Here, the amplitude of the detected vibration is largest when the frequency f1 of the drive signal S1 matches the resonant frequency f2 of the vibrator 2. In other words, when the frequency f1 matches the resonant frequency f2, the detected vibration can be detected with the highest sensitivity. This state is called a mode match state. On the other hand, due to manufacturing errors of the gyro sensor 1 or the like, the frequency f1 and the resonant frequency f2 may not match. This state is called a mode mismatch state. In the mode mismatch state, the amplitude of the detected vibration is lower than in the mode match state. Furthermore, in the mode mismatch state, a phase difference θd occurs between the drive vibration and the detected vibration. At this time, the amplitude of the tone signal S6 superimposed on the detection signal S3 is not affected by the angular velocity applied to the vibrator 2, but depends on the phase difference θd.

[0023] According to the above configuration, by reducing the phase difference θd by the adjustment signal S13 corresponding to the tone signal S6 superimposed on the detection signal S3, the gyro sensor 1 can be put into a mode-matched state regardless of whether an angular velocity is applied to the vibrator 2 or not.

[0024] (2) Configuration and Operation of Gyro Sensor The configuration and operation of the gyro sensor 1 according to the embodiment will be described below.

[0025] As shown in FIG. 1, the gyro sensor 1 includes a vibrator 2, a plurality of electrodes 3, and a control unit 4.

[0026] The vibrator 2 is made of a material containing, for example, single crystal silicon or polycrystalline silicon, etc. The shape of the vibrator 2 is, for example, a disk shape or a rectangular plate shape.

[0027] The plurality of electrodes 3 are arranged around the vibrator 2 at intervals from the vibrator 2. Each of the plurality of electrodes 3 has a facing surface facing the vibrator 2.

[0028] The plurality of electrodes 3 includes a drive electrode 31, a detection electrode 32, and a detection feedback electrode 33. The plurality of electrodes 3 further includes an adjustment electrode 34 that is different from the drive electrode 31, the detection electrode 32, and the detection feedback electrode 33. In other words, the adjustment electrode 34 is an electrode that is different from the drive electrode 31, the detection electrode 32, and the detection feedback electrode 33. The plurality of electrodes 3 further includes a monitor electrode 35 that is different from the drive electrode 31, the detection electrode 32, and the detection feedback electrode 33.

[0029] The control unit 4 is, for example, a single ASIC (Application Specific Integrated Circuit). The control unit 4 is not limited to a single ASIC, and may be a circuit including one or more ICs, or may be a microcomputer.

[0030] 1, the control unit 4 includes a drive circuit 41, a detection circuit 42, a detection feedback circuit 43, a tone signal generation circuit 44, an adjustment circuit 45, and a failure determination circuit 46. The control unit 4 also includes a low-pass filter 47 and an angular velocity calculation unit 48.

[0031] The drive circuit 41 is electrically connected to the drive electrode 31 and the monitor electrode 35 .

[0032] The drive circuit 41 outputs a drive signal S1 to the drive electrode 31. The drive signal S1 is an AC signal. As an example, the waveform of the drive signal S1 is a sine wave. However, the waveform of the drive signal S1 may also be a square wave.

[0033] When the drive signal S1 is output to the drive electrode 31, the capacitance between the vibrator 2 and the drive electrode 31 changes, causing the vibrator 2 to vibrate periodically. In other words, the drive signal S1 induces periodic vibration in the vibrator 2. Hereinafter, the vibration of the vibrator 2 caused by the drive signal S1 will be referred to as drive vibration. As an example, the frequency f1 of the drive signal S1 is set to 40 kHz.

[0034] Furthermore, when drive vibration is generated by the drive signal S1, the capacitance between the vibrator 2 and the monitor electrode 35 changes, and a monitor signal S2 is output from the monitor electrode 35 to the drive circuit 41. In other words, the monitor electrode 35 outputs the monitor signal S2 corresponding to the drive signal S1 to the drive circuit 41.

[0035] The drive circuit 41 corrects the drive signal S1 so that the amplitude of the monitor signal S2 falls within a predetermined range.

[0036] Here, when a driving vibration is generated in the vibrator 2, if the gyro sensor 1 tilts and an angular velocity about an axis in the thickness direction of the vibrator 2 is applied to the vibrator 2, the vibrator 2 resonates due to the Coriolis force. Hereinafter, the resonance of the vibrator 2 due to the Coriolis force will be referred to as the detection vibration. In other words, the angular velocity applied to the vibrator 2 causes a detection vibration in the vibrator 2 in a state where a driving vibration is induced. The frequency of the detection vibration is equal to the frequency f1 of the driving vibration.

[0037] The amplitude of the detection vibration is largest when the frequency f1 of the drive signal S1 matches the resonant frequency f2 of the vibrator 2 in the direction in which the detection vibration is generated. In other words, when the frequency f1 matches the resonant frequency f2, the detection vibration can be detected with the highest sensitivity. This state is called a mode match state. In the mode match state, the phase of the drive vibration matches the phase of the detection vibration. On the other hand, due to manufacturing errors of the gyro sensor 1, etc., the frequency f1 and the resonant frequency f2 may not match. This state is called a mode mismatch state. In the mode mismatch state, the amplitude of the detection vibration is lower than in the mode match state. In the mode mismatch state, a phase difference θd occurs between the drive vibration and the detection vibration.

[0038] When a detection vibration occurs, the capacitance between the vibrator 2 and the detection electrode 32 changes, and the detection electrode 32 outputs a detection signal S3 to the detection circuit 42.

[0039] 1, the detection circuit 42 includes a first demodulation circuit 421 and a second demodulation circuit 422. The first demodulation circuit 421 and the second demodulation circuit 422 are electrically connected to the detection electrode 32. A detection signal S3 is output from the detection electrode 32 to the first demodulation circuit 421 and the second demodulation circuit 422, respectively.

[0040] The first demodulation circuit 421 demodulates a signal (in-phase signal) that is in phase with the drive signal S1 from among the signals included in the detection signal S3 to generate a first demodulation signal S4, which is output as the above-mentioned angular velocity signal to the low-pass filter 47, the detection feedback circuit 43, and the adjustment circuit 45, which will be described later. The in-phase signal is a signal having an amplitude that corresponds to the angular velocity applied to the vibrator 2. The first demodulation signal (angular velocity signal) S4 obtained by demodulating the in-phase signal is a signal that corresponds to the amplitude of the in-phase vibration.

[0041] The second demodulation circuit 422 demodulates a signal (quadrature signal) that is shifted in phase by 90° from the drive signal S1 from among the signals included in the detection signal S3, and outputs the demodulated signal S5 to the detection feedback circuit 43 and the adjustment circuit 45. The quadrature signal is included in the detection signal S3 when the gyro sensor 1 is in a mode mismatch state, and is not included in the detection signal S3 when the gyro sensor 1 is in a mode match state.

[0042] As shown in FIG. 1, the detection feedback circuit 43 includes a first modulation circuit 431, a second modulation circuit 432, a first summing circuit 433, and a second summing circuit 434.

[0043] The first demodulation signal S4 is output from the first demodulation circuit 421 to the first adder circuit 433. The tone signal S6 is also output from the tone signal generation circuit 44 to the first adder circuit 433. The tone signal S6 is an AC signal having a frequency f3 that is lower than the frequency f1 of the drive signal S1. The frequency f3 is, for example, a 3 kHz sine wave.

[0044] The first adder circuit 433 adds (superimposes) the tone signal S6 to the first demodulation signal S4 to generate a first added signal S7, and outputs the first added signal S7 to the first modulation circuit 431.

[0045] The first modulation circuit 431 modulates the first sum signal S7 with the drive signal S1 having the frequency f1 to generate a first modulated signal S8, and outputs the first modulated signal S8 to the second sum circuit 434.

[0046] The second modulation circuit 432 modulates the second demodulation signal S5 with the drive signal S1 of frequency f1 to generate a second modulation signal S9, and outputs the result to the second addition circuit 434.

[0047] The second adder circuit 434 outputs a feedback signal S10 obtained by adding the second modulated signal S9 to the first modulated signal S8 to the detection feedback electrode 33. In other words, the feedback signal S10 includes a first modulated signal S8 obtained by modulating, with the drive signal S1, a first summed signal S7 obtained by superimposing the tone signal S6 on the first demodulated signal S4. In this case, the influence on the detection result of the angular velocity applied to the vibrator 2 can be reduced compared to the case where the tone signal S6 is superimposed on the second demodulated signal S5.

[0048] The feedback signal S10 is a signal having an amplitude corresponding to the angular velocity applied to the vibrator 2. Furthermore, the tone signal S6 output from the tone signal generation circuit 44 is superimposed on the feedback signal S10. Here, a waveform W1 of the feedback signal S10 is shown in FIG. 2. As shown in FIG. 2, the feedback signal S10 oscillates at the frequency f1 of the drive signal S1, and also at the frequency f3 of the tone signal S6.

[0049] By outputting the feedback signal S10 to the detection feedback electrode 33, the detection vibration generated when an angular velocity is applied to the vibrator 2 is suppressed. This allows the gyro sensor 1 to detect a larger angular velocity. In other words, the dynamic range of the gyro sensor 1 is expanded. Furthermore, the responsiveness of the gyro sensor 1 can be improved.

[0050] Furthermore, as described above, the tone signal S6 of frequency f3 is superimposed on the feedback signal S10, and therefore the tone signal S6 is superimposed on the detection signal S3 output to the detection circuit 42 by the detected vibration via the feedback signal S10.

[0051] Therefore, the first demodulation signal S4 obtained by the first demodulation circuit 421 demodulating the in-phase signal that is in phase with the drive signal S1 and is included in the detection signal S3 is a signal in which vibration of frequency f3 (first tone vibration) is superimposed on a signal whose intensity corresponds to the amplitude of the in-phase signal, i.e., corresponds to the angular velocity applied to the vibrator 2. Here, the amplitude of the first tone vibration depends on the cosine cos θd of the phase difference θd. In other words, the amplitude of the first tone vibration increases as the phase difference θd decreases, and is maximum in a mode-matched state where the phase difference θd is 0. As an example, FIG. 3 shows a waveform W2 of the first demodulation signal S4 in a mode-matched state.

[0052] Furthermore, the second demodulation circuit 422 demodulates the quadrature signal included in the detection signal S3, which is shifted in phase by 90° from the drive signal S1, to produce a second demodulated signal S5. The resulting signal has an intensity corresponding to the amplitude of the quadrature signal, and a superimposed oscillation of frequency f3 (second tone oscillation). The amplitude of the second tone oscillation depends on the sine of the phase difference θd (sin θd). That is, the smaller the phase difference θd, the smaller the amplitude of the second tone oscillation. The amplitude of the second tone oscillation is minimized (zero) in a mode-matched state where the phase difference θd is zero. In other words, the amplitude of the second tone oscillation is greater than zero in a mode-mismatched state where the phase difference θd is not zero. In other words, in a mode-mismatched state, the second demodulated signal S5 generates a second tone oscillation derived from the tone signal S6. As an example, FIG. 4 shows a waveform W3 of the second demodulated signal S5 in a mode-matched state and a waveform W4 of the second demodulated signal S5 in a mode-mismatched state. 4, in the mode-matched state, the detection signal S3 does not contain a quadrature signal, so the intensity of the second demodulated signal S5 is 0, and the amplitude of the second tone vibration is also 0. On the other hand, in the mode-mismatched state, the detection signal S3 contains a quadrature signal, so the intensity of the second demodulated signal S5 exceeds 0, and a phase difference θd occurs, causing the second tone vibration of frequency f3.

[0053] When the gyro sensor 1 is in a mode mismatch state, the adjustment circuit 45 performs a mode match operation to put the gyro sensor 1 into a mode match state.

[0054] The adjustment circuit 45 includes a third demodulation circuit 451 and an output circuit 452 .

[0055] The third demodulation circuit 451 demodulates the signal in phase with the tone signal S6 of frequency f3 from among the signals included in the first demodulation signal S4 output from the first demodulation circuit 421, and outputs the resulting third demodulation signal S11 to the output circuit 452. In other words, the third demodulation signal S11 is a DC signal whose intensity corresponds to the amplitude of the first tone vibration. Therefore, the intensity of the third demodulation signal S11 depends on the cosine cos θd.

[0056] The third demodulation circuit 451 demodulates the signal in phase with the tone signal S6 from among the signals included in the second demodulation signal S5 output from the second demodulation circuit 422, and outputs the demodulated signal S12 to the output circuit 452. That is, the fourth demodulation signal S12 is a DC signal whose intensity corresponds to the amplitude of the second tone vibration. Therefore, the intensity of the fourth demodulation signal S12 depends on the sine sin θd.

[0057] The output circuit 452 outputs an adjustment signal S13 generated based on the third demodulation signal S11 and the fourth demodulation signal S12 to the adjustment electrode 34. Specifically, the output circuit 452 calculates a value (adjustment value) by dividing the intensity of the fourth demodulation signal S12 by the intensity of the third demodulation signal S11. As described above, the intensity of the third demodulation signal S11 depends on the cosine cos θd, and the intensity of the fourth demodulation signal S12 depends on the sine sin θd. Therefore, the adjustment value depends on the tangent tan θd of the phase difference θd.

[0058] The output circuit 452 generates an adjustment signal S13 such that the adjustment value approaches 0, i.e., the phase difference θd approaches 0°, and outputs the signal to the adjustment electrode 34. More specifically, the output circuit 452 outputs the adjustment signal S13 to the adjustment electrode 34 such that the absolute value of the adjustment value is equal to or less than a predetermined value. The adjustment signal S13 is a DC voltage signal. When the adjustment signal S13 is output to the adjustment electrode 34, the resonant frequency f2 of the vibrator 2 decreases. In other words, when the resonant frequency f2 is higher than the frequency f1, outputting the adjustment signal S13 to the adjustment electrode 34 causes the resonant frequency f2 to approach the frequency f1 and the phase difference θd to approach 0°. In other words, when the resonant frequency f2 in the gyro sensor 1 is higher than the frequency f1, the output circuit 452 outputs the adjustment signal S13 to the adjustment electrode 34. In this way, the adjustment circuit 45 performs mode matching operation based on an adjustment value that depends on the phase difference θd without being affected by the angular velocity applied to the vibrator 2, so the gyro sensor 1 can be in a mode matching state regardless of whether an angular velocity is applied to the vibrator 2 or not.

[0059] The failure determination circuit 46 determines that a failure has occurred when the strength of the adjustment signal S13 falls outside the reference range. More specifically, the failure determination circuit 46 determines that a failure has occurred in the gyro sensor 1 when the strength of the adjustment signal S13 is greater than an upper threshold value or less than a lower threshold value.

[0060] The low-pass filter 47 removes the first tone vibration at frequency f3 from the first demodulated signal S4.

[0061] The angular velocity calculation unit 48 calculates the angular velocity applied to the vibrator 2 based on the first demodulation signal S4 from which the first tone vibration has been removed by the low-pass filter 47. The calculation result of the angular velocity by the angular velocity calculation unit 48 is output to a presentation device (user interface) or the like that presents information about the angular velocity to the user, via a communication unit arranged downstream of the angular velocity calculation unit 48.

[0062] (3) Modifications The above embodiment is merely one of various embodiments of the present disclosure. The above embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the embodiment are listed below. The above embodiment and the modifications described below can be applied in appropriate combinations. In the modifications described below, components common to the above embodiment are designated by the same reference numerals, and their description will be omitted.

[0063] (3.1) Modification 1 A gyro sensor 1A according to modification 1 will be described below with reference to FIG. 5A.

[0064] The gyro sensor 1A differs from the gyro sensor 1 according to the above embodiment in that any one of the drive electrode 31, the detection electrode 32, and the detection feedback electrode 33 also serves as the adjustment electrode 34. In other words, in the gyro sensor 1A, the adjustment electrode 34 is the drive electrode 31, the detection electrode 32, or the detection feedback electrode 33. In the gyro sensor 1A shown in FIG. 5A , the detection electrode 32 functions as the adjustment electrode 34. That is, in the gyro sensor 1A, the output circuit 452 is configured to output the adjustment signal S13 generated based on the third demodulation signal S11 and the fourth demodulation signal S12 to the drive electrode 31, the detection electrode 32, or the detection feedback electrode 33. This allows the number of electrodes 3 to be reduced, simplifying the configuration of the gyro sensor 1.

[0065] FIG. 5B is a schematic block diagram of another gyro sensor 1A1 of Modification 1. In FIG. 5B, the same components as those in the gyro sensor 1A shown in FIG. 5A are assigned the same reference numerals. The gyro sensor 1A further includes a switch 91 provided between the output circuit 452 and the drive electrode 31, a switch 92 provided between the output circuit 452 and the detection electrode 32, and a switch 93 provided between the output circuit 452 and the detection feedback electrode 33. The control unit 4 controls the switches 91 to 93 on and off so that one of the switches 91 to 93 is turned on and the other two are turned off, whereby the output circuit 452 outputs an adjustment signal S13 to one of the drive electrode 31, the detection electrode 32, or the detection feedback electrode 33. This allows the number of electrodes 3 to be reduced, simplifying the configuration of the gyro sensor 1.

[0066] (3.2) Modification 2 A gyro sensor 1B according to modification 2 will be described below with reference to FIG.

[0067] The gyro sensor 1B differs from the gyro sensor 1 according to the above embodiment in that the detection electrode 32 or the monitor electrode 35 also serves as the adjustment electrode 34. In other words, in the gyro sensor 1B, the adjustment electrode 34 is the detection electrode 32 or the monitor electrode 35. That is, the detection electrode 32 or the monitor electrode 35 functions as the adjustment electrode 34 shown in FIG. 1 , and the gyro sensor 1B does not include the adjustment electrode 34 of the gyro sensor 1 shown in FIG. 1 . That is, in the gyro sensor 1B, the output circuit 452 is configured to output the adjustment signal S13 generated based on the third demodulation signal S11 and the fourth demodulation signal S12 to the detection electrode 32 or the monitor electrode 35.

[0068] More specifically, when the resonant frequency f2 of the vibrator 2 in the direction in which the detection vibration is generated is higher than the frequency f1 of the drive vibration, the adjustment electrode 34 serves as the detection electrode 32. That is, the detection electrode 32 functions as the adjustment electrode 34 shown in FIG. 1 . When the adjustment signal S13 is output to the detection electrode 32, the resonant frequency f2 of the vibrator 2 decreases. That is, when the resonant frequency f2 is higher than the frequency f1, outputting the adjustment signal S13 to the detection electrode 32, which serves as the adjustment electrode, causes the resonant frequency f2 to approach the frequency f1, and the phase difference θd to approach 0°. In the gyro sensor 1B, the resonant frequency f2 is higher than the frequency f1, and the output circuit 452 outputs the adjustment signal S13 to the detection electrode 32.

[0069] When the resonant frequency f2 of the vibrator 2 in the direction in which the detection vibration is generated is lower than the frequency f1 of the drive vibration, the adjustment electrode 34 serves as the monitor electrode 35. That is, the monitor electrode 35 functions as the adjustment electrode 34 shown in FIG. 1. When the adjustment signal S13 is output to the monitor electrode 35, the frequency f1 of the drive vibration decreases. That is, when the resonant frequency f2 is lower than the frequency f1, outputting the adjustment signal S13 to the adjustment / monitor electrode 35 causes the frequency f1 to approach the resonant frequency f2 and the phase difference θd to approach 0°. In the gyro sensor 1B, the resonant frequency f2 is lower than the frequency f1, and the output circuit 452 outputs the adjustment signal S13 to the monitor electrode 35.

[0070] In this way, the gyro sensor 1B can be in a mode-matched state whether the resonant frequency f2 is higher or lower than the frequency f1. Furthermore, similar to the first modification, the second modification shown in FIG. 6 also allows the number of electrodes 3 to be reduced, thereby simplifying the configuration of the gyro sensor 1.

[0071] Whether the detection electrode 32 or the monitor electrode 35 is to be used as the adjustment electrode 34 is determined based on the measurement results of the resonance frequency f2 during the manufacture of the gyro sensor 1, for example.

[0072] (4) Summary As described above, the gyro sensor (1) of the first aspect includes a vibrator (2), a plurality of electrodes (3), and a control unit (4). The plurality of electrodes (3) includes a drive electrode (31), a detection electrode (32), a detection feedback electrode (33), and an adjustment electrode (34), and are arranged to face the vibrator (2), thereby forming a capacitance between the vibrator (2). The control unit (4) is electrically connected to the plurality of electrodes (3). The control unit (4) includes a drive circuit (41), a detection circuit (42), a detection feedback circuit (43), a tone signal generation circuit (44), and an adjustment circuit (45). The drive circuit (41) outputs a drive signal (S1) to the drive electrode (31) that induces drive vibration of the vibrator (2). The detection circuit (42) outputs an angular velocity signal (S4) indicating an angular velocity based on a detection signal (S3) output from the detection electrode (32) that detects the detection vibration. The detection vibration is a vibration generated in the vibrator (2) when drive vibration is induced by an angular velocity applied to the vibrator (2). The detection feedback circuit (43) outputs a feedback signal (S10) based on the angular velocity signal (S4) output from the detection circuit (42) to the detection feedback electrode (33). The tone signal generation circuit (44) outputs a tone signal (S6) having a frequency (f3) lower than the frequency (f1) of the drive signal (S1) to the detection feedback circuit (43). The adjustment circuit (45) outputs an adjustment signal (S13) for controlling the resonant frequency (f2) of the vibrator (2) to the adjustment electrode (34). The detection feedback circuit (43) superimposes the tone signal (S6) on the feedback signal (S10) and outputs the result to the detection feedback electrode (33). The adjustment circuit (45) outputs an adjustment signal (S13) to the adjustment electrode (34) according to the tone signal (S6) superimposed on the detection signal (S3) via a feedback signal (S10) output to the detection feedback electrode (33).

[0073] According to this aspect, by reducing the phase difference (θd) by the adjustment signal (S13) corresponding to the tone signal (S6) superimposed on the detection signal (S3), the gyro sensor (1) can be brought into a mode-matched state regardless of whether an angular velocity is applied to the vibrator (2).

[0074] In the gyro sensor (1) of the second aspect, in the first aspect, the detection circuit (42) includes a first demodulation circuit (421) that demodulates a signal included in the detection signal (S3) that is in phase with the drive signal (S1) and outputs the demodulated signal (S4) as an angular velocity signal (S4) to the detection feedback circuit (43). The feedback signal (S10) includes a modulated signal (S8) obtained by modulating a signal (S7) obtained by superimposing a tone signal (S6) on the first demodulated signal (S4) with the drive signal (S1).

[0075] According to this aspect, the influence on the detection result of the angular velocity applied to the vibrator (2) can be reduced compared to the case where a tone signal (S6) is superimposed on a demodulated signal (S5) obtained by demodulating an orthogonal signal included in the detection signal (S3) that is shifted in phase by 90° from the drive signal (S1).

[0076] In the gyro sensor (1) of the third aspect, in the second aspect, the first demodulation circuit (421) further outputs the first demodulation signal (S4) to the adjustment circuit (45). The detection circuit (42) further includes a second demodulation circuit (422) that outputs a second demodulation signal (S5) to the adjustment circuit (45) by demodulating signals included in the detection signal (S3) whose phase is shifted by 90° from the phase of the drive signal (S1). The adjustment circuit (45) includes a third demodulation circuit (451) and an output circuit (452). The third demodulation circuit (451) outputs a third demodulation signal (S11) by demodulating signals included in the first demodulation signal (S4) that are in phase with the tone signal (S6), and outputs a fourth demodulation signal (S12) by demodulating signals included in the second demodulation signal (S5) that are in phase with the tone signal (S6). The output circuit (452) outputs an adjustment signal (S13) generated based on the third demodulation signal (S11) and the fourth demodulation signal (S12) to the adjustment electrode (34).

[0077] According to this aspect, by reducing the phase difference (θd) using the adjustment signal (S13), the gyro sensor (1) can be brought into a mode-matched state regardless of whether an angular velocity is applied to the vibrator (2).

[0078] In the gyro sensor (1) of the fourth aspect, in the first to third aspects, the adjustment electrode (34) is an electrode different from the drive electrode (31), the detection electrode (32), and the detection feedback electrode (33).

[0079] According to this aspect, it is possible to reduce the influence of the adjustment signal (S13) on the drive signal (S1), the detection signal (S3), and the feedback signal (S10).

[0080] In the gyro sensor (1) of the fifth aspect, in the first to third aspects, the adjustment electrode (34) is the drive electrode (31), the detection electrode (32), or the detection feedback electrode (33).

[0081] According to this aspect, the number of electrodes (3) can be reduced, and the configuration of the gyro sensor (1) can be simplified.

[0082] In the gyro sensor (1) of the sixth aspect, in the first to third aspects, the plurality of electrodes (3) further includes a monitor electrode (35) that outputs a monitor signal (S2) corresponding to the drive signal (S1) to the drive circuit (41), different from the drive electrode (31), the detection electrode (32), and the detection feedback electrode (33). When the resonant frequency (f2) is higher than the frequency (f1) of the drive signal (S1), the adjustment electrode (34) is the detection electrode (32). When the resonant frequency (f2) is lower than the frequency (f1) of the drive signal (S1), the adjustment electrode (34) is the monitor electrode (35).

[0083] According to this aspect, the gyro sensor (1) can be brought into a mode-matched state whether the resonant frequency (f2) is higher or lower than the frequency (f1).

[0084] In the seventh aspect of the gyro sensor (1), in the first to sixth aspects, the control unit (4) further includes a failure determination circuit (46) that determines that a failure has occurred in the gyro sensor (1) when the intensity of the adjustment signal (S13) falls outside the reference range.

[0085] According to this aspect, the reliability of the gyro sensor (1) can be improved.

[0086] The second to seventh aspects are not essential components of the gyro sensor (1) and can be omitted as appropriate.

[0087] REFERENCE SIGNS LIST 1 Gyro sensor 2 Vibrator 3 Electrode 4 Control unit 31 Drive electrode 32 Detection electrode 33 Detection feedback electrode 34 Adjustment electrode 35 Monitor electrode 41 Drive circuit 42 Detection circuit 43 Detection feedback circuit 44 Tone signal generation circuit 45 Adjustment circuit 46 Fault determination circuit 421 First demodulation circuit (demodulation circuit) 422 Second demodulation circuit 451 Third demodulation circuit 452 Output circuit f1 Frequency f2 Resonance frequency f3 Frequency S1 Drive signal S10 Feedback signal S11 Third demodulation signal S12 Fourth demodulation signal S13 Adjustment signal S2 Monitor signal S3 Detection signal S4 First demodulation signal (demodulation signal, angular velocity signal) S5 Second demodulation signal (demodulation signal) S6 Tone signal S7 Signal S8 Modulation signal θd phase difference

Claims

1. A device comprising: a vibrator; a plurality of electrodes including a drive electrode, a detection electrode, a detection feedback electrode, and an adjustment electrode, and arranged to face the vibrator to form a capacitance between the vibrator and the plurality of electrodes; and a control unit electrically connected to the plurality of electrodes, wherein the control unit comprises: a drive circuit that outputs a drive signal to the drive electrode that induces a drive vibration of the vibrator; a detection circuit that outputs an angular velocity signal indicating the angular velocity based on a detection signal output from the detection electrode that detects a detection vibration generated in the vibrator when the drive vibration is induced by an angular velocity applied to the vibrator; a detection feedback circuit that outputs a feedback signal based on the angular velocity signal output from the detection circuit to the detection feedback electrode; a tone signal generation circuit that outputs a tone signal having a frequency lower than the frequency of the drive signal to the detection feedback circuit; and an adjustment circuit that outputs an adjustment signal to the adjustment electrode that controls the resonance frequency of the vibrator, wherein the detection feedback circuit superimposes the tone signal on the feedback signal and outputs it to the detection feedback electrode, the adjustment circuit outputs the adjustment signal to the adjustment electrode in accordance with the tone signal superimposed on the detection signal via the feedback signal output to the detection feedback electrode.

2. The gyro sensor according to claim 1, wherein the detection circuit comprises a first demodulation circuit that demodulates a signal included in the detection signal that is in phase with the drive signal and outputs a first demodulated signal to the detection feedback circuit as the angular velocity signal, and the feedback signal includes a modulated signal obtained by modulating a signal obtained by superimposing the tone signal on the first demodulated signal with the drive signal.

3. The gyro sensor according to claim 2, wherein the first demodulation circuit outputs the first demodulated signal to the adjustment circuit; the detection circuit further comprises a second demodulation circuit that outputs a second demodulated signal to the adjustment circuit, the second demodulated signal being obtained by demodulating signals included in the detection signal that are out of phase with the drive signal by 90°; and the adjustment circuit comprises: a third demodulation circuit that outputs a third demodulated signal by demodulating signals included in the first demodulated signal that are in phase with the tone signal, and a fourth demodulated signal by demodulating signals included in the second demodulated signal that are in phase with the tone signal; and an output circuit that outputs the adjustment signal generated based on the third demodulation signal and the fourth demodulation signal to the adjustment electrode.

4. The gyro sensor according to any one of claims 1 to 3, wherein the adjustment electrode is an electrode different from the drive electrode, the detection electrode, and the detection feedback electrode.

5. The gyro sensor according to any one of claims 1 to 3, wherein the adjustment electrode is the drive electrode, the detection electrode, or the detection feedback electrode.

6. A gyro sensor according to any one of claims 1 to 3, wherein the plurality of electrodes further includes a monitor electrode that is different from the drive electrode, the detection electrode, and the detection feedback electrode and outputs a monitor signal corresponding to the drive signal to the drive circuit, and when the resonance frequency is higher than the frequency of the drive signal, the adjustment electrode is the detection electrode, and when the resonance frequency is lower than the frequency of the drive signal, the adjustment electrode is the monitor electrode.

7. The gyro sensor according to any one of claims 1 to 3, wherein the control unit further comprises a failure determination circuit that determines that a failure has occurred in the gyro sensor when the strength of the adjustment signal falls outside a reference range.

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