Gyro sensor

Abstract

A drive circuit applies, to a drive electrode, a drive signal 2 corrected in response to a monitoring signal. A detection circuit generates, on the basis of a detection signal, an angular velocity signal corresponding to an angular velocity applied to a vibrator. A detection feedback circuit applies, to a detection feedback electrode, a detection feedback signal generated on the basis of the angular velocity signal. A correction circuit corrects the detection feedback signal in response to a monitoring signal.

Description

Gyro sensor

[0001] The present disclosure relates generally to gyro sensors, and more particularly to gyro sensors having a feedback loop for controlling detected vibrations of a vibrator.

[0002] The sensing device (gyro sensor) described in Patent Document 1 detects angular velocity. The sensing device includes a MEMS (Micro Electro Mechanical Systems) gyroscope (vibrator), a rate feedback loop (detection feedback circuit), a quadrature feedback loop, and a test signal generator. The MEMS gyroscope is coupled to the rate feedback loop and the quadrature feedback loop. The test signal generator generates a test signal. The test signal is injected into the rate feedback loop, then fed back to the MEMS gyroscope, and finally detected from the quadrature feedback loop. This allows the sensing device to monitor the entire system.

[0003] US Patent Application Publication No. 2014 / 250970

[0004] When the characteristics of the detection feedback circuit change, the angular velocity signal output from the gyro sensor changes accordingly, which may result in a decrease in the accuracy of angular velocity detection. The characteristics of the detection feedback circuit referred to here include, for example, the gain of the detection feedback circuit.

[0005] A gyro sensor according to one aspect of the present disclosure includes a vibrator, multiple electrodes, and a control unit. The multiple electrodes are arranged to face the vibrator and form a capacitance between them. The control unit is electrically connected to the multiple electrodes. The multiple electrodes include a drive electrode, a monitor electrode, a detection electrode, and a detection feedback electrode. A drive signal is applied to the drive electrode to cause the vibrator to vibrate as a drive vibration. The monitor electrode outputs a monitor signal generated by the drive vibration of the vibrator. The detection electrode outputs a detection signal generated by a detection vibration of the vibrator caused by application of an angular velocity to the vibrator. A detection feedback signal is applied to the detection feedback electrode to control the detection vibration of the vibrator. The control unit includes a drive circuit, a detection circuit, a detection feedback circuit, and a correction circuit. The drive circuit applies the drive signal corrected in response to the monitor signal to the drive electrode. The detection circuit generates an angular velocity signal corresponding to the angular velocity applied to the vibrator based on the detection signal. The detection feedback circuit applies the detection feedback signal generated based on the angular velocity signal to the detection feedback electrode, and the correction circuit corrects the detection feedback signal in response to the monitor signal.

[0006] The present disclosure has an advantage in that it is possible to suppress a decrease in the accuracy of detecting angular velocity due to a change in the characteristics of the detection feedback circuit.

[0007] Fig. 1 is a block diagram of a gyro sensor according to an embodiment, Fig. 2 is a waveform diagram showing a modulation signal of the gyro sensor, and Fig. 3 is an explanatory diagram showing processing of the gyro sensor.

[0008] (Embodiment) A gyro sensor 1 according to an embodiment will be described below with reference to the drawings. However, the embodiment described below is merely one of various embodiments of the present disclosure. The embodiment described below can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved.

[0009] In this disclosure, applying a voltage signal to an object means applying a voltage signal between the object and a structure maintained at a reference potential (eg, ground).

[0010] (Overview) As shown in FIG. 1 , a gyro sensor 1 of this embodiment includes a vibrator 10, multiple electrodes 2, and a control unit 3. The multiple electrodes 2 are arranged to face the vibrator 10 and form a capacitance between them. The control unit 3 is electrically connected to the multiple electrodes 2. The multiple electrodes 2 include drive electrodes 21 and 22, monitor electrodes 23 and 24, detection electrodes 25 and 26, and detection feedback electrodes 27 and 28. Drive signals D1 and D2 are applied to the drive electrodes 21 and 22 to vibrate the vibrator 10 as drive vibrations. The monitor electrodes 23 and 24 output monitor signals M1 and M2 generated by the drive vibration of the vibrator 10. The detection electrodes 25 and 26 output detection signals S1 and S2 generated by the detection vibration of the vibrator 10 when an angular velocity is applied to the vibrator 10. Detection feedback signals F1 and F2 are applied to the detection feedback electrodes 27 and 28 to control the detection vibration of the vibrator 10. The control unit 3 has a drive circuit 31, a detection circuit 32, a detection feedback circuit 4, and a correction circuit 5. The drive circuit 31 applies drive signals D1 and D2 corrected in accordance with monitor signals M1 and M2 to the drive electrodes 21 and 22. The detection circuit 32 generates an angular velocity signal A1 corresponding to the angular velocity applied to the vibrator 10 based on the detection signals S1 and S2. The detection feedback circuit 4 applies detection feedback signals F1 and F2 generated based on the angular velocity signal A1 to the detection feedback electrodes 27 and 28. The correction circuit 5 corrects the detection feedback signals F1 and F2 in accordance with the monitor signals M1 and M2.

[0011] According to the above configuration, the correction circuit 5 corrects the detection feedback signals F1 and F2 in accordance with the monitor signals M1 and M2, thereby making it possible to deal with changes in the characteristics of the detection feedback circuit 4. For example, the correction circuit 5 corrects the detection feedback signals F1 and F2 so as to cancel out changes in the characteristics of the detection feedback circuit 4. Therefore, it is possible to prevent the angular velocity detection accuracy of the gyro sensor 1 from being reduced due to changes in the characteristics of the detection feedback circuit 4.

[0012] The characteristic of the detection feedback circuit referred to here is, for example, the gain of the detection feedback circuit. When the gain of the detection feedback circuit 4 decreases, the magnitude of the angular velocity signal A1 increases, and when the gain of the detection feedback circuit 4 increases, the magnitude of the angular velocity signal A1 decreases. The correction circuit 5 cancels out changes in the gain of the detection feedback circuit 4, so that the gyro sensor 1 can detect the angular velocity with high accuracy even if the gain of the detection feedback circuit 4 changes.

[0013] Furthermore, the monitor signals M1 and M2 are signals synchronized with the drive signals D1 and D2. Therefore, the correction circuit 5 can easily perform signal processing on the monitor signal M3 (a signal corresponding to the monitor signals M1 and M2), which will be described later. Compared to correcting the detection feedback signals F1 and F2 in response to a signal other than the monitor signals M1 and M2, the correction circuit 5 can easily perform signal processing.

[0014] (Details) The gyro sensor 1 of this embodiment will be described in more detail below.

[0015] (1) Vibrator and Multiple Electrodes The vibrator 10 is formed of a material containing, for example, single crystal silicon or polycrystalline silicon, etc. The shape of the vibrator 10 is, for example, a disk shape or a rectangular plate shape.

[0016] The plurality of electrodes 2 are arranged around the vibrator 10 at intervals between them. Each of the plurality of electrodes 2 has a facing surface facing the vibrator 10.

[0017] The plurality of electrodes 2 preferably correspond to each other in pairs. The plurality of electrodes 2 in this embodiment include corresponding drive electrodes 21 and 22, corresponding monitor electrodes 23 and 24, corresponding detection electrodes 25 and 26, and corresponding detection feedback electrodes 27 and 28.

[0018] A drive signal D1 is applied to the drive electrode 21. A drive signal D2 is applied to the drive electrode 22. The drive signals D1 and D2 are AC signals of opposite phases. The frequencies of the drive signals D1 and D2 match the resonance frequency of the vibrator 10. When the drive signals D1 and D2 are applied to the drive electrodes 21 and 22, respectively, the vibrator 10 vibrates (expands and contracts) periodically due to the electrostatic force between the vibrator 10 and the drive electrodes 21 and 22. This vibration is referred to as drive vibration in this disclosure.

[0019] The monitor electrodes 23 and 24 face the vibrator 10 in the direction of the drive vibration of the vibrator 10. The detection electrodes 25 and 26 face the vibrator 10 in a direction perpendicular to the direction of the drive vibration of the vibrator 10.

[0020] When the vibrator 10 is driven to vibrate, the distance between the vibrator 10 and the monitor electrode 23 changes, causing the capacitance between the vibrator 10 and the monitor electrode 23 to change, and the monitor electrode 23 outputs a monitor signal M1 corresponding to the change in capacitance.

[0021] When the vibrator 10 is driven to vibrate, the distance between the vibrator 10 and the monitor electrode 24 changes, causing the capacitance between the vibrator 10 and the monitor electrode 24 to change, and the monitor electrode 24 outputs a monitor signal M2 corresponding to the change in capacitance.

[0022] The monitor signals M1 and M2 are AC signals. The frequencies of the monitor signals M1 and M2 match the resonance frequency of the vibrator 10. The component of the monitor signal M2 corresponding to the drive vibration of the vibrator 10 is in opposite phase to the component of the monitor signal M1 corresponding to the drive vibration of the vibrator 10.

[0023] When an angular velocity is applied to the vibrator 10 while the vibrator 10 is being driven to vibrate, the Coriolis force causes the vibrator 10 to resonate (vibrate in detection). The distance between the vibrator 10 and the detection electrodes 25, 26 changes in response to the angular velocity applied to the vibrator 10, causing a change in the capacitance between the vibrator 10 and the detection electrodes 25, 26. The detection electrode 25 outputs a detection signal S1 corresponding to the change in capacitance. The detection electrode 26 outputs a detection signal S2 corresponding to the change in capacitance. The detection signals S1, S2 are signals corresponding to the magnitude of the angular velocity applied to the vibrator 10. The detection signals S1, S2 are modulated signals. The component of the detection signal S2 corresponding to the angular velocity applied to the vibrator 10 is in opposite phase to the component of the detection signal S1 corresponding to the angular velocity applied to the first vibrator 10.

[0024] The detection feedback circuit 4 applies a detection feedback signal F1 to the detection feedback electrode 27. The detection feedback circuit 4 applies a detection feedback signal F2 to the detection feedback electrode 28. The detection feedback signals F1 and F2 are AC signals of opposite phases to each other.

[0025] By applying the detection feedback signals F1 and F2 to the detection feedback electrodes 27 and 28, the amplitude of the resonant vibration of the vibrator 10, which corresponds to the angular velocity applied to the vibrator 10, decreases. This reduces the amplitude of each of the detection signals S1 and S2. The magnitude of the amplitude of the detection signals S1 and S2 corresponds to the angular velocity applied to the vibrator 10. Therefore, by reducing the amplitude of each of the detection signals S1 and S2, the gyro sensor 1 can detect larger angular velocities. In other words, the dynamic range of the gyro sensor 1 is expanded. Furthermore, by reducing the amplitude of each of the detection signals S1 and S2, the response speed of the gyro sensor 1 is increased.

[0026] (2) Control Unit As shown in FIG. 1, the control unit 3 includes a drive circuit 31, a detection circuit 32, an angular velocity calculation unit 33, a detection feedback circuit 4, a correction circuit 5, a failure determination circuit 61, and an output unit 62.

[0027] The drive circuit 31 is electrically connected to the drive electrodes 21 and 22. The drive circuit 31 outputs (applies) drive signals D1 and D2 to the drive electrodes 21 and 22. As an example, the waveforms of the drive signals D1 and D2 are rectangular waves. However, the waveforms of the drive signals D1 and D2 may also be sinusoidal waves.

[0028] The drive circuit 31 is electrically connected to the monitor electrodes 23 and 24. The drive circuit 31 acquires monitor signals M1 and M2 from the monitor electrodes 23 and 24.

[0029] The drive circuit 31 corrects the drive signals D1 and D2 in accordance with the monitor signals M1 and M2. That is, the drive circuit 31 generates the drive signals D1 and D2 by feeding back the monitor signals M1 and M2. The drive circuit 31 corrects the drive signals D1 and D2 so that the amplitudes of the monitor signals M1 and M2 are between a predetermined upper limit and a predetermined lower limit.

[0030] If the difference between the predetermined upper limit and the predetermined lower limit is sufficiently small, the monitor signals M1 and M2 are signals with stable amplitudes. That is, in this case, the monitor signals M1 and M2 are signals controlled by the drive circuit 31 so that their amplitudes remain constant over time. Therefore, the correction circuit 5 can detect changes in the gain of the detection feedback circuit 4 by comparing the amplitude of a monitor signal M3 (a signal corresponding to the monitor signals M1 and M2) (described below) input to the detection feedback circuit 4 with a reference value, and can correct the detection feedback signals F1 and F2 in accordance with the change in gain.

[0031] The detection circuit 32 is electrically connected to the detection electrodes 25 and 26. The detection circuit 32 acquires detection signals S1 and S2 from the detection electrodes 25 and 26.

[0032] The detection circuit 32 includes a demodulation circuit 320. The demodulation circuit 320 demodulates the detection signals S1 and S2 using the drive signals D1 and D2. The demodulation circuit 320 generates an angular velocity signal A1 by demodulating the detection signals S1 and S2. As an example, the angular velocity signal A1 is a differential signal between a demodulated signal of the detection signal S1 and a demodulated signal of the detection signal S2. However, the demodulation circuit 320 may output one of the demodulated signal of the detection signal S1 and the demodulated signal of the detection signal S2 as the angular velocity signal A1.

[0033] The angular velocity signal A1 is a DC signal. The angular velocity calculation unit 33 calculates the angular velocity applied to the vibrator 10 based on the angular velocity signal A1. As an example, the angular velocity calculated by the angular velocity calculation unit 33 is proportional to the magnitude of the angular velocity signal A1.

[0034] 1, the detection feedback circuit 4 includes an adder circuit 41, a modulator circuit 42, a first filter circuit 43, and a phase shifter 44. The correction circuit 5 includes a second filter circuit 51, a decision circuit 52, and an adjustment circuit 53.

[0035] The adder circuit 41 acquires the angular velocity signal A1 from the detection circuit 32. The adder circuit 41 also acquires the monitor signal M3.

[0036] The monitor signal M3 is a differential signal between the monitor signals M1 and M2. The monitor signal M3 is a signal with double the amplitude of the monitor signal M1 or M2. As an example, the monitor signal M3 is generated by the drive circuit 31. The adder circuit 41 acquires the monitor signal M3 from the drive circuit 31.

[0037] In this embodiment, the monitor signal input to the adder circuit 41 of the detection feedback circuit 4 is the monitor signal M3. As described above, the monitor signal input to the detection feedback circuit 4 does not have to be exactly the same as the monitor signals M1 and M2 output from the monitor electrodes 23 and 24. For example, the monitor signal may be a signal obtained by changing the amplitude of the monitor signal M1 or M2 by a certain percentage, or a signal obtained by removing noise from the monitor signal M1 or M2. The monitor signal input to the detection feedback circuit 4 may be any signal that has the same frequency as the monitor signals M1 and M2 and has a known amplitude.

[0038] The adder circuit 41 generates a sum signal K1 by adding the angular velocity signal A1 (DC signal) and the monitor signal M3 (AC signal).

[0039] The modulation circuit 42 generates a modulated signal H1 by modulating the added signal K1 using the drive signals D1 and D2.

[0040] 2, the modulated signal H1 includes a modulated signal of the angular velocity signal A1, a DC component (DC signal M4) corresponding to the amplitude of the monitor signal M3, and an AC component corresponding to the monitor signal M3. ０ Then, the frequency of the modulated signal H1 for the angular velocity signal A1 is f ０ , the frequency of the AC component corresponding to the monitor signal M3 is 2×f ０ This becomes:

[0041] The first filter circuit 43 generates the detection feedback signal F1 by removing the component corresponding to the monitor signal M3 from the modulated signal H1. More specifically, the first filter circuit 43 includes a band-pass filter, and the band-pass filter removes the AC component and DC component corresponding to the monitor signal M3 from the modulated signal H1, and extracts the component corresponding to the angular velocity signal A1. That is, the first filter circuit 43 removes the frequency f of the modulated signal of the angular velocity signal A1. ０ Extract the components.

[0042] The detection feedback signal F 1 generated by the first filter circuit 43 is output to the detection feedback electrode 27 and the phase shifter 44 .

[0043] The phase shifter 44 generates a detection feedback signal F2 by shifting the phase of the detection feedback signal F1 by 180 degrees. The detection feedback signal F2 generated by the phase shifter 44 is output to the detection feedback electrode 28.

[0044] The second filter circuit 51 extracts a DC component (DC signal M4) corresponding to the magnitude of the amplitude of the monitor signal M3 from the modulated signal H1. More specifically, the second filter circuit 51 includes a low-pass filter, and extracts the DC component (DC signal M4) by the low-pass filter.

[0045] The determination circuit 52 determines the amount of correction for the detection feedback signals F1 and F2 based on the DC component (DC signal M4) obtained from the second filter circuit 51.

[0046] The determination circuit 52 includes, for example, a register, and the register performs a process of determining the correction amounts of the detection feedback signals F1 and F2.

[0047] The adjustment circuit 53 corrects the detection feedback signals F1 and F2 in accordance with the correction amount determined by the determination circuit 52.

[0048] More specifically, the determination circuit 52 determines the amount of correction for the gain of the detection feedback circuit 4. Therefore, the correction circuit 5 (the adjustment circuit 53 thereof) corrects the gain of the detection feedback circuit 4 in accordance with the monitor signal M3. The adjustment circuit 53 outputs a correction signal G1 to the detection feedback circuit 4 for correcting the gain.

[0049] The adjustment circuit 53 corrects the gain of the circuit between the input terminal to which the angular velocity signal A1 is input and the output terminal from which the detection feedback signals F1 and F2 are output in the detection feedback circuit 4. That is, the adjustment circuit 53 corrects the gain of at least one of the adder circuit 41, the modulation circuit 42, and the first filter circuit 43.

[0050] Next, the process by which the determination circuit 52 determines the correction amount will be described in detail.

[0051] The magnitude of the DC signal M4 is proportional to the amplitude of the monitor signal M3. The determination circuit 52 determines the amount of correction by comparing the magnitude of the DC signal M4 obtained from the second filter circuit 51 with at least one reference value. In other words, the correction circuit 5 corrects the detection feedback signals F1 and F2 based on the amplitude of the monitor signal M3.

[0052] The following describes the relationship between the amplitude of the monitor signal M3 and at least one reference value, but in reality, the decision circuit 52 determines the amount of correction by comparing the magnitude of the DC signal M4 with a value corresponding to the at least one reference value.

[0053] The correction circuit 5 reduces the gain of the detection feedback circuit 4 when the amplitude of the monitor signal M3 is greater than the first reference value R1 (see FIG. 3).

[0054] When the amplitude of the monitor signal M3 is smaller than a second reference value R2 (see FIG. 3), the correction circuit 5 increases the gain of the detection feedback circuit 4. The second reference value R2 is a value equal to or smaller than the first reference value R1.

[0055] The second reference value R2 is set to a value smaller than the first reference value R1, and a predetermined value larger than the second reference value R2 and smaller than the first reference value R1 is set to a third reference value R3. For example, the correction circuit 5 corrects the gain of the detection feedback circuit 4 so that the amplitude of the monitor signal M3 becomes the third reference value R3.

[0056] Alternatively, the correction circuit 5 corrects the gain of the detection feedback circuit 4 so that the amplitude of the monitor signal M3 is greater than the second reference value R2 and less than the first reference value R1. In this case, the correction circuit 5 may maintain the gain of the detection feedback circuit 4 without correcting it when the amplitude of the monitor signal M3 is equal to or less than the second reference value R2 and equal to or greater than the first reference value R1.

[0057] Here, the amplitude of the monitor signal M3 and the magnitude of the DC signal M4 correspond to the magnitude of the gain of the detection feedback circuit 4. The greater the gain of the detection feedback circuit 4, the greater the amplitude of the monitor signal M3 and the magnitude of the DC signal M4.

[0058] Furthermore, the greater the gain of the detection feedback circuit 4, the smaller the angular velocity calculated by the angular velocity calculation unit 33. Therefore, the more the gain of the detection feedback circuit 4 deviates from the design value, the lower the accuracy of angular velocity detection in the gyro sensor 1.

[0059] Therefore, the correction circuit 5 corrects the gain of the detection feedback circuit 4 in response to the monitor signal M3 so that the gain of the detection feedback circuit 4 becomes a value between a predetermined upper limit gain and a predetermined lower limit gain. As an example, the upper limit gain is 1.05 times the lower limit gain. The magnitude of the gain of the detection feedback circuit 4 can be calculated by the determination circuit 52 of the correction circuit 5 based on the magnitude of the DC signal M4, for example, using a predetermined arithmetic expression.

[0060] Next, the failure determination circuit 61 (see FIG. 1) will be described.

[0061] The failure determination circuit 61 determines whether the detection feedback circuit 4 has a failure based on the monitor signal M3 input to the detection feedback circuit 4 .

[0062] When the amplitude of the monitor signal M3 is greater than the upper threshold T1, the failure determination circuit 61 determines that a failure has occurred in the detection feedback circuit 4. The upper threshold T1 is greater than the first reference value R1.

[0063] When the amplitude of the monitor signal M3 is smaller than the lower threshold T2, the fault determination circuit 61 determines that a fault has occurred in the detection feedback circuit 4. The lower threshold T2 is smaller than the second reference value R2. When the amplitude of the monitor signal M3 is equal to or smaller than the upper threshold T1 and equal to or larger than the lower threshold T2, the fault determination circuit 61 determines that a fault has not occurred in the detection feedback circuit 4.

[0064] When the fault determination circuit 61 determines that a fault has occurred in the detection feedback circuit 4, it is considered that the fault has occurred in a circuit between the input terminal of the detection feedback circuit 4 to which the monitor signal M3 is input and the fault determination circuit 61. In other words, the fault determination circuit 61 detects a fault occurring in the adder circuit 41 and the modulator circuit 42 of the detection feedback circuit 4.

[0065] The decision circuit 52 may also decrease the gain of the detection feedback circuit 4 when the amplitude of the monitor signal M3 is greater than the upper threshold T1, and may also increase the gain of the detection feedback circuit 4 when the amplitude of the monitor signal M3 is smaller than the lower threshold T2.

[0066] The output unit 62 outputs the determination result of the fault determination circuit 61. The output unit 62 may include, for example, a display device and display the determination result on the display device. The output unit 62 may also include, for example, an audio device such as a speaker and output the determination result as sound (which may include voice) from the audio device. The output unit 62 may also include, for example, a communication module and transmit the determination result from the communication module to an external device.

[0067] (Modifications of the embodiment) Modifications of the embodiment are listed below. The following modifications may be realized in appropriate combination.

[0068] The plurality of electrodes 2 may include only one of the driving electrodes 21 and 22 .

[0069] The plurality of electrodes 2 may include only one of the monitor electrodes 23 and 24 .

[0070] The plurality of electrodes 2 may include only one of the detection electrodes 25 and 26 .

[0071] The plurality of electrodes 2 may include only one of the detection feedback electrodes 27, 28.

[0072] The detection feedback circuit 4 may receive the monitor signal M1 or M2 instead of the monitor signal M3.

[0073] (Summary) The above-described embodiments and the like disclose the following aspects.

[0074] A gyro sensor (1) according to a first aspect includes a vibrator (10), a plurality of electrodes (2), and a control unit (3). The plurality of electrodes (2) are arranged to face the vibrator (10) and form a capacitance between the vibrator (10) and the control unit (3). The control unit (3) is electrically connected to the plurality of electrodes (2). The plurality of electrodes (2) include drive electrodes (21, 22), monitor electrodes (23, 24), detection electrodes (25, 26), and detection feedback electrodes (27, 28). Drive signals (D1, D2) are applied to the drive electrodes (21, 22) to vibrate the vibrator (10) as drive vibrations. The monitor electrodes (23, 24) output monitor signals (M1, M2) generated by the drive vibrations of the vibrator (10). The detection electrodes (25, 26) output detection signals (S1, S2) generated by the detection vibration of the vibrator (10) when an angular velocity is applied to the vibrator (10). The detection feedback electrodes (27, 28) receive detection feedback signals (F1, F2) for controlling the detection vibration of the vibrator (10). The control unit (3) has a drive circuit (31), a detection circuit (32), a detection feedback circuit (4), and a correction circuit (5). The drive circuit (31) applies drive signals (D1, D2) corrected in accordance with monitor signals (M1, M2) to the drive electrodes (21, 22). The detection circuit (32) generates an angular velocity signal (A1) corresponding to the angular velocity applied to the vibrator (10) based on the detection signals (S1, S2). A detection feedback circuit (4) applies detection feedback signals (F1, F2) generated based on an angular velocity signal (A1) to detection feedback electrodes (27, 28). A correction circuit (5) corrects the detection feedback signals (F1, F2) in response to monitor signals (M1, M2).

[0075] According to the above configuration, the correction circuit (5) corrects the detection feedback signals (F1, F2) in response to the monitor signals (M1, M2), thereby making it possible to deal with changes in the characteristics of the detection feedback circuit (4), thereby suppressing a decrease in the accuracy of angular velocity detection due to changes in the characteristics of the detection feedback circuit (4).

[0076] In the gyro sensor (1) according to the second aspect, in the first aspect, the correction circuit (5) corrects the gain of the detection feedback circuit (4) in response to the monitor signals (M1, M2).

[0077] According to the above configuration, the detection feedback signals (F1, F2) can be changed by correcting the gain.

[0078] In addition, in the gyro sensor (1) according to the third aspect, in the second aspect, the correction circuit (5) corrects the gain of the detection feedback circuit (4) in accordance with the monitor signals (M1, M2) so that the gain of the detection feedback circuit (4) becomes a value between a predetermined upper limit gain and a predetermined lower limit gain.

[0079] According to the above configuration, it is possible to suppress a decrease in the accuracy of detecting angular velocity in the gyro sensor (1).

[0080] In addition, in the gyro sensor (1) according to the fourth aspect, in the second or third aspect, the correction circuit (5) reduces the gain of the detection feedback circuit (4) when the amplitude of the monitor signal (M1, M2) is greater than the first reference value (R1).

[0081] According to the above configuration, it is possible to suppress a decrease in the accuracy of detecting angular velocity in the gyro sensor (1).

[0082] In addition, in a gyro sensor (1) according to a fifth aspect, in the fourth aspect, the control unit (3) further includes a fault determination circuit (61). The fault determination circuit (61) determines a fault in the detection feedback circuit (4) based on monitor signals (M1, M2) input to the detection feedback circuit (4). The fault determination circuit (61) determines that a fault has occurred in the detection feedback circuit (4) when the amplitude of the monitor signals (M1, M2) is greater than an upper threshold (T1) that is greater than a first reference value (R1).

[0083] According to the above configuration, it is possible to detect abnormalities that cannot be dealt with by gain correction alone.

[0084] In addition, in the gyro sensor (1) according to the sixth aspect, in any one of the second to fifth aspects, the correction circuit (5) increases the gain of the detection feedback circuit (4) when the amplitude of the monitor signal (M1, M2) is smaller than the second reference value (R2).

[0085] According to the above configuration, it is possible to suppress a decrease in the accuracy of detecting angular velocity in the gyro sensor (1).

[0086] In addition, in a gyro sensor (1) according to a seventh aspect, in the sixth aspect, the control unit (3) further includes a fault determination circuit (61). The fault determination circuit (61) determines a fault in the detection feedback circuit (4) based on monitor signals (M1, M2) input to the detection feedback circuit (4). The fault determination circuit (61) determines that a fault has occurred in the detection feedback circuit (4) when the amplitude of the monitor signals (M1, M2) is smaller than a lower limit threshold (T2) that is smaller than a second reference value (R2).

[0087] According to the above configuration, it is possible to detect abnormalities that cannot be dealt with by gain correction alone.

[0088] In addition, in the gyro sensor (1) according to an eighth aspect, in any one of the first to seventh aspects, the control unit (3) further includes a failure determination circuit (61). The failure determination circuit (61) determines whether the detection feedback circuit (4) has a failure based on the monitor signals (M1, M2) input to the detection feedback circuit (4).

[0089] According to the above configuration, the gyro sensor (1) can correct the detection feedback signals (F1, F2) and also determine whether there is a failure.

[0090] In addition, in a gyro sensor (1) according to a ninth aspect, in any one of the first to eighth aspects, the detection circuit (32) includes a demodulation circuit (320) that generates an angular velocity signal (A1) by demodulating the detection signal (S1, S2). The detection feedback circuit (4) further includes an adder circuit (41) that generates a sum signal (K1) by adding the angular velocity signal (A1) and the monitor signal (M1, M2), a modulation circuit (42) that generates a modulated signal (H1) by modulating the sum signal (K1), and a first filter circuit (43) that generates detection feedback signals (F1, F2) by removing components corresponding to the monitor signal (M1, M2) from the modulated signal (H1). The correction circuit (5) includes a second filter circuit (51) that extracts a DC component corresponding to the magnitude of the amplitude of the monitor signal (M1, M2) from the modulation signal (H1), a decision circuit (52) that decides the amount of correction for the detection feedback signal (F1, F2) based on the DC component acquired from the second filter circuit (51), and an adjustment circuit (53) that corrects the detection feedback signal (F1, F2) in accordance with the amount of correction decided by the decision circuit (52).

[0091] According to the above configuration, it is possible to reduce the possibility that the angular velocity signal (A1) will affect the determination of the correction amount by the determination circuit (52).

[0092] The configurations other than the first aspect are not essential for the gyro sensor (1) and can be omitted as appropriate.

[0093] REFERENCE SIGNS LIST 1 gyro sensor 2 electrode 3 control unit 4 detection feedback circuit 5 correction circuit 10 vibrator 21, 22 drive electrodes 23, 24 monitor electrodes 25, 26 detection electrodes 27, 28 detection feedback electrodes 31 drive circuit 32 detection circuit 41 addition circuit 42 modulation circuit 43 first filter circuit 51 second filter circuit 52 decision circuit 53 adjustment circuit 61 fault determination circuit 320 demodulation circuit A1 angular velocity signal D1, D2 drive signal F1, F2 detection feedback signal H1 modulation signal K1 addition signal M1, M2 monitor signal R1 first reference value R2 second reference value S1, S2 detection signal T1 upper threshold T2 lower threshold

Claims

1. A gyro sensor comprising: a vibrator; a plurality of electrodes arranged to face the vibrator and forming electrostatic capacitance between them; and a control unit electrically connected to the plurality of electrodes, wherein the plurality of electrodes include: a drive electrode to which a drive signal is applied for vibrating the vibrator as a drive vibration; a monitor electrode for outputting a monitor signal generated by the drive vibration of the vibrator; a detection electrode for outputting a detection signal generated by detection vibration of the vibrator when an angular velocity is applied to the vibrator; and a detection feedback electrode to which a detection feedback signal for controlling the detection vibration of the vibrator is applied, wherein the control unit has: a drive circuit that applies the drive signal corrected in accordance with the monitor signal to the drive electrodes; a detection circuit that generates, based on the detection signal, an angular velocity signal corresponding to the angular velocity applied to the vibrator; a detection feedback circuit that applies the detection feedback signal generated based on the angular velocity signal to the detection feedback electrode; and a correction circuit that corrects the detection feedback signal in accordance with the monitor signal.

2. The gyro sensor according to claim 1, wherein the correction circuit corrects the gain of the detection feedback circuit in response to the monitor signal.

3. The gyro sensor according to claim 2, wherein the correction circuit corrects the gain of the detection feedback circuit in response to the monitor signal so that the gain of the detection feedback circuit becomes a value between a predetermined upper limit gain and a predetermined lower limit gain.

4. The gyro sensor according to claim 2, wherein the correction circuit reduces the gain of the detection feedback circuit when the amplitude of the monitor signal is greater than a first reference value.

5. The gyro sensor according to claim 4, wherein the control unit further has a failure determination circuit that determines whether the detection feedback circuit has a failure based on the monitor signal input to the detection feedback circuit, and the failure determination circuit determines that a failure has occurred in the detection feedback circuit when the amplitude of the monitor signal is greater than an upper threshold value that is greater than the first reference value.

6. The gyro sensor according to claim 2, wherein the correction circuit increases the gain of the detection feedback circuit when the amplitude of the monitor signal is smaller than a second reference value.

7. The gyro sensor according to claim 6, wherein the control unit further has a failure determination circuit that determines whether the detection feedback circuit has a failure based on the monitor signal input to the detection feedback circuit, and the failure determination circuit determines that a failure has occurred in the detection feedback circuit when the amplitude of the monitor signal is smaller than a lower limit threshold that is smaller than the second reference value.

8. The gyro sensor according to claim 1, wherein the control unit further comprises a failure determination circuit that determines whether the detection feedback circuit has a failure based on the monitor signal input to the detection feedback circuit.

9. The gyro sensor according to claim 1, wherein the detection circuit includes a demodulation circuit that generates the angular velocity signal by demodulating the detection signal, the detection feedback circuit further includes an addition circuit that generates an addition signal by adding the angular velocity signal and the monitor signal, a modulation circuit that modulates the addition signal to generate a modulated signal, and a first filter circuit that generates the detection feedback signal by removing a component corresponding to the monitor signal from the modulated signal, and the correction circuit includes a second filter circuit that extracts a DC component corresponding to the magnitude of the amplitude of the monitor signal from the modulated signal, a decision circuit that decides a correction amount for the detection feedback signal based on the DC component acquired from the second filter circuit, and an adjustment circuit that corrects the detection feedback signal in accordance with the correction amount decided by the decision circuit.

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