Gyroscope sensor

Abstract

This gyroscope sensor comprises a vibrator, a plurality of electrodes, and a control unit. The control unit has a drive circuit, a conversion circuit, a first demodulation circuit, a detection feedback circuit, a detection processing circuit, a test signal generation unit, and a diagnostic circuit. The test signal generation unit outputs a test signal for failure diagnosis to the conversion circuit. The frequency of the test signal is outside the response range of a detection loop circuit including the vibrator, the conversion circuit, the first demodulation circuit, and the detection feedback circuit.

Description

Gyro sensor

[0001] The present disclosure relates generally to gyro sensors, and more particularly to a gyro sensor that performs fault diagnosis using a test signal.

[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] 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, and a detection control electrode. The multiple electrodes are arranged to face the vibrator and form a capacitance between the vibrator and the control unit. The control unit is connected to the drive electrode, the detection electrode, and the detection control electrode. The control unit includes a drive circuit, a conversion circuit, a demodulation circuit, a detection feedback circuit, a detection processing circuit, a test signal generation unit, and one or more diagnostic circuits. The drive circuit outputs a drive signal to the drive electrode to induce drive vibration of the vibrator. The conversion circuit converts the detection signal output from the detection electrode. The demodulation circuit is connected downstream of the conversion circuit and generates a demodulated detection signal by demodulating a signal component in phase with the drive signal from the detection signal converted by the conversion circuit. The detection feedback circuit is inserted between the demodulation circuit and the detection control electrode and generates a voltage to be applied to the detection control electrode based on the demodulated detection signal. The detection processing circuit is connected downstream of the demodulation circuit and generates an angular velocity signal representing the angular velocity of the vibrator based on the demodulated detection signal. The test signal generation unit has an output terminal connected to an electrical path between the detection electrode and the conversion circuit and outputs a test signal for fault diagnosis to the conversion circuit via the output terminal. The one or more diagnostic circuits are connected downstream of the conversion circuit and generate a fault diagnosis signal representing the result of fault diagnosis of the control unit based on the test signal. The frequency of the test signal is outside the response range of a detection loop circuit including the vibrator, the conversion circuit, the demodulation circuit, and the detection feedback circuit.

[0005] The present disclosure has the advantage of reducing the possibility that the test signal will affect the angular rate signal.

[0006] Fig. 1 is a block diagram showing the circuit configuration of a gyro sensor according to one embodiment, and Fig. 2 is a block diagram showing the circuit configuration of a test signal generating unit of a gyro sensor according to a modified example.

[0007] (Embodiment) A capacitive 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. Furthermore, each figure described in the embodiment described below is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0008] In this disclosure, "applying a voltage" to an object means applying a voltage between the object and a structure maintained at a reference potential (eg, ground).

[0009] The term "terminal" as used herein may be any component that can be electrically connected to another component. The term "terminal" may be a component such as a connector for connecting an electric wire, or may be a part of a conductor such as a wire, a printed wiring, or a metal wiring in a semiconductor.

[0010] In Fig. 1, the drive signal D1 is a carrier wave. In Fig. 1, the detection signal S1, the test signal T1, the signal ST1, and the signal ST2 are each signals that can be superimposed (modulated) on a carrier wave. The detection signal S1, the test signal T1, the signal ST1, and the signal ST2 may be transmitted superimposed on a carrier wave, but Fig. 1 does not show the carrier waves that carry these signals.

[0011] The signal ST1 is a signal obtained by adding the detection signal S1 and the test signal T1. The signal ST2 is a signal obtained by converting the signal ST1 as a current signal into a voltage signal. The demodulated signal ST3 is a signal of the signal ST2 that is in phase with the drive signal D1. The demodulated signal ST4 is a signal of the signal ST2 that is out of phase with the drive signal D1.

[0012] In the following description, the three diagnostic circuits 6 in FIG. 1 will also be referred to as a first diagnostic circuit 61, a second diagnostic circuit 62, and a third diagnostic circuit 63, respectively.

[0013] (Overview) As shown in FIG. 1 , the gyro sensor 1 of this embodiment includes a vibrator 10, multiple electrodes 2, and a control unit U1. The multiple electrodes 2 include a drive electrode 21, a detection electrode 22, and a detection control electrode 23. The multiple electrodes 2 are arranged to face the vibrator 10 and form capacitance between them. The control unit U1 is connected to the drive electrode 21, the detection electrode 22, and the detection control electrode 23. The control unit U1 includes a drive circuit 31, a conversion circuit 41, a demodulation circuit 42 (hereinafter also referred to as the first demodulation circuit 42), a detection feedback circuit 43, a detection processing circuit 33, a test signal generation unit 34, and one or more diagnostic circuits 6. The drive circuit 31 outputs a drive signal D1 to the drive electrode 21 to induce drive vibration in the vibrator 10. The conversion circuit 41 converts a detection signal S1 output from the detection electrode 22. The first demodulation circuit 42 is connected downstream (output side) of the conversion circuit 41 and generates a demodulated detection signal by demodulating a signal component in phase with the drive signal D1 from the detection signal S1 converted by the conversion circuit 41. The detection feedback circuit 43 is inserted between the first demodulation circuit 42 and the detection control electrode 23 and generates a voltage to be applied to the detection control electrode 23 based on the demodulated detection signal. The detection processing circuit 33 is connected downstream of the first demodulation circuit 42 and generates an angular velocity signal representing the angular velocity of the vibrator 10 based on the demodulated detection signal. The test signal generation unit 34 has an output terminal 344 connected to the electrical path between the detection electrode 22 and the conversion circuit 41 and outputs a test signal T1 for fault diagnosis to the conversion circuit 41 via the output terminal 344. One or more diagnostic circuits 6 are connected downstream of the conversion circuit 41 and generate a fault diagnosis signal representing the result of the fault diagnosis of the control unit U1 based on the test signal T1. The frequency of the test signal T1 is outside the response range of the detection loop circuit L1 including the vibrator 10, the conversion circuit 41, the first demodulation circuit 42, and the detection feedback circuit 43.

[0014] According to this embodiment, the test signal T1 is attenuated by circulating through the detection loop circuit L1. This reduces the possibility that the test signal T1 will affect the angular velocity signal. In other words, it reduces the possibility that the test signal T1 will interfere with the detection of the angular velocity. Furthermore, the test signal T1 before attenuation can be used to perform a fault diagnosis of the control unit U1.

[0015] For example, the test signal T1 reaches the first diagnostic circuit 61 and the third diagnostic circuit 63 among the one or more diagnostic circuits 6. However, even if the test signal T1 is output to the detection control electrode 23, the vibrator 10 is insensitive to the frequency of the test signal T1 (i.e., the vibrator 10 does not vibrate in response to the test signal T1), and therefore the detection signal S1 output from the detection electrode 22 does not include a signal component of the test signal T1. In other words, as an example, the test signal T1 is attenuated to such an extent that it can be considered to be at zero level in the vibrator 10.

[0016] As a comparative example of this embodiment, a configuration in which the configuration disclosed in Patent Document 1 is applied to the gyro sensor 1 of FIG. 1 is assumed. In the comparative example, components corresponding to those of this embodiment are assigned the same reference numerals. In the comparative example, the test signal T1 output to the detection feedback circuit 43 must be output from the vibrator 10 to the conversion circuit 41 and the second demodulation circuit 51 (described later) to the second diagnostic circuit 62. Therefore, in the comparative example, the vibrator 10 must vibrate in response to the test signal T1, and a vibrator 10 with a wide response range must be selected for transmission of the test signal T1. In contrast, in the gyro sensor 1 of this embodiment, there is no need to set the response range of the vibrator 10 itself wide in order to transmit the test signal T1, and therefore, design freedom is greater than in the comparative example (Patent Document 1).

[0017] Furthermore, in the gyro sensor 1 of this embodiment, increasing the sensitivity to angular velocity by reducing the feedback amount of the detection loop circuit L1 does not prevent the test signal T1 from reaching the three diagnostic circuits 6. Therefore, this embodiment can provide a gyro sensor 1 that is highly sensitive to angular velocity.

[0018] (Details) The gyro sensor 1 of this embodiment will be described in more detail below.

[0019] (1) Overall Configuration As shown in FIG. 1, the gyro sensor 1 includes a vibrator 10, a plurality of electrodes 2 (eight in FIG. 1), and a control unit U1.

[0020] The plurality of electrodes 2 includes two drive electrodes 21 , two detection electrodes 22 , two detection control electrodes 23 , and two quadrature correction electrodes 24 .

[0021] The control unit U1 has a drive circuit 31, a first connection circuit 32, a detection processing circuit 33, a test signal generation unit 34, a conversion circuit 41, a first demodulation circuit 42, a detection feedback circuit 43, a second demodulation circuit 51, a second connection circuit 52, a quadrature feedback circuit 53, and multiple (three in Figure 1) diagnostic circuits 6.

[0022] In the gyro sensor 1, a signal in phase with the drive signal D1, out of the detection signal S1 output from the detection electrode 22, is fed back to the vibrator 10 through a detection loop circuit L1. The detection loop circuit L1 includes the vibrator 10, a conversion circuit 41, a first demodulation circuit 42, and a detection feedback circuit 43.

[0023] In the gyro sensor 1, a signal having a predetermined phase different from the phase of the drive signal D1 out of the detection signal S1 output from the detection electrode 22 is fed back to the vibrator 10 through the quadrature loop circuit L2. The quadrature loop circuit L2 includes the vibrator 10, a conversion circuit 41, a second demodulation circuit 51, a second connection circuit 52, and a quadrature feedback circuit 53.

[0024] Of the detection signal S1, a signal having a predetermined phase different from the phase of the drive signal D1 is also called a quadrature signal or an unwanted signal. The phase difference between the drive signal D1 and the quadrature signal is, for example, 90 degrees. In the following description, a case where the phase difference between the drive signal D1 and the quadrature signal is 90 degrees will be described as an example. However, the phase difference is not limited to 90 degrees.

[0025] (2) 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.

[0026] 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.

[0027] The plurality of electrodes 2 preferably correspond to each other in pairs. The plurality of electrodes 2 in this embodiment include two corresponding drive electrodes 21, two corresponding detection electrodes 22, two corresponding detection control electrodes 23, and two quadrature correction electrodes 24.

[0028] 1, the two corresponding electrodes 2 are shown as being adjacent to each other, but it is preferable that the two corresponding electrodes 2 are arranged on opposite sides of the center of the vibrator 10. In other words, it is preferable that the vibrator 10 is arranged between the two corresponding electrodes 2.

[0029] (3) Drive Circuit The drive circuit 31 is connected to the two drive electrodes 21. The drive circuit 31 outputs (applies) a drive signal D1 to each of the two drive electrodes 21. The drive signal D1 is a voltage signal. The waveform of the drive signal D1 is, for example, a sine wave or a rectangular wave. The drive circuit 31 outputs the drive signals D1 to the two drive electrodes 21 in opposite phases to each other.

[0030] When a drive signal D1 is output to at least one of the two drive electrodes 21, the vibrator 10 periodically vibrates (expands and contracts) due to an electrostatic force between the vibrator 10 and the at least one drive electrode 21. This vibration is referred to as drive vibration in the present disclosure.

[0031] The frequency of the drive signal D1 is, for example, 1 MHz or more and 10 MHz or less.

[0032] (4) Conversion Circuit When the vibrator 10 rotates, the Coriolis force causes the vibrator 10 to resonate. The distance between the vibrator 10 and the two detection electrodes 22 changes depending on the angular velocity of the vibrator 10, and the capacitance between the vibrator 10 and the two detection electrodes 22 also changes. The two detection electrodes 22 output a detection signal S1 that corresponds to the magnitude of the capacitance. The detection signal S1 is a signal that corresponds to the magnitude of the angular velocity of the vibrator 10.

[0033] The frequency (peak frequency) of the detection signal S1 is equal to the frequency of the drive signal D1. In this disclosure, "equal" does not necessarily mean completely equal, but also includes cases where they differ to a practically acceptable extent. For example, if the difference between the frequency of the detection signal S1 and the frequency of the drive signal D1 is within 0.2% of either value, the frequency of the detection signal S1 and the frequency of the drive signal D1 may be considered "equal" and the present disclosure may be applied.

[0034] The conversion circuit 41 is connected to the two detection electrodes 22. The conversion circuit 41 is a circuit that converts the detection signal S1 output from each of the two detection electrodes 22. The conversion circuit 41 may be, for example, a circuit that performs CV conversion (conversion from capacitance to voltage) or IV conversion (conversion from current to voltage) of the detection signal S1. The conversion circuit 41 of this embodiment includes a transimpedance amplifier 411 and performs IV conversion of the detection signal S1.

[0035] The test signal generating unit 34 is connected to the electrical path between the conversion circuit 41 and the two detection electrodes 22. The signal input to the conversion circuit 41 is a signal ST1 obtained by adding together the detection signals S1 output from the two detection electrodes 22 and the test signal T1 output from the test signal generating unit 34. In other words, the conversion circuit 41 converts the signal ST1 that includes the detection signal S1. The conversion circuit 41 outputs the converted signal ST2 (voltage signal).

[0036] Since the conversion circuit 41 includes the transimpedance amplifier 411, it is possible to simplify the configuration of the connection between the test signal generation unit 34 and the conversion circuit 41. Specifically, it is possible to add the detection signal S1 and the test signal T1 simply by connecting the detection electrode 22 and the output terminal 344 of the test signal generation unit 34 without using an adder.

[0037] (5) Test Signal Generator The test signal generator 34 generates a test signal T1 and outputs it to the conversion circuit 41. The test signal T1 is, for example, a square wave or a sine wave. The frequency of the test signal T1 is, for example, 10 kHz or more and 100 kHz or less.

[0038] The test signal generating section 34 outputs the test signal T1 together with the carrier wave to the conversion circuit 41. That is, the signal output from the test signal generating section 34 is a signal in which the test signal T1 is superimposed on the carrier wave.

[0039] The carrier wave is the drive signal D1 generated by the drive circuit 31. That is, the test signal generation unit 34 outputs a signal in which the test signal T1 is superimposed on the drive signal D1 to the conversion circuit 41. This makes it easy to demodulate the test signal T1 in circuits subsequent to the conversion circuit 41.

[0040] The test signal generating section 34 includes a circuit 341 , two resistors 342 , two capacitors 343 , and two output terminals 344 .

[0041] The circuit 341 includes, for example, an oscillator that generates a rectangular wave test signal T1, and superimposes (AM modulates) the test signal T1 on a drive signal D1 that is a carrier wave.

[0042] A first end of a series circuit of a resistor 342 and a capacitor 343 is connected to each of the two output terminals of the circuit 341. A second end of the series circuit is connected to an output terminal 344. The test signal T1 superimposed on the drive signal D1 passes through the series circuit and is output from the output terminal 344.

[0043] The capacitor 343 cuts the DC component of the test signal T1, thereby preventing the conversion circuit 41 and the test signal generating unit 34 from sharing the same DC bias.

[0044] (6) First Demodulation Circuit The input terminal of the first demodulation circuit 42 is connected to the output terminal of the conversion circuit 41. The first demodulation circuit 42 includes a mixer 421. The first demodulation circuit 42 demodulates the signal ST2 output from the conversion circuit 41 using the drive signal D1. As a result, the first demodulation circuit 42 demodulates the signal component in phase with the drive signal D1 from the signal ST2 output from the conversion circuit 41 to generate a demodulated signal ST3.

[0045] The demodulated signal ST3 includes a "demodulated detection signal" and a "demodulated test signal." The demodulated detection signal is a signal obtained by demodulating a signal component of the detection signal S1 that is in phase with the drive signal D1. The demodulated test signal is a signal obtained by demodulating a signal component of the test signal T1 that is in phase with the drive signal D1.

[0046] Hereinafter, the "demodulated detection signal" will also be referred to as the detection signal S1, and the "demodulated test signal" will also be referred to as the test signal T1. When the gyro sensor 1 is operating normally, the detection signal S1 output from the detection electrode 22 and the test signal T1 output from the test signal generation unit 34 are in phase with the drive signal D1, and therefore these detection signal S1 and test signal T1 match the detection signal S1 and test signal T1 included in the demodulated signal ST3. When an abnormality occurs in the gyro sensor 1 and the signal ST2 contains a signal that is out of phase with the drive signal D1, the detection signal S1 output from the detection electrode 22 and the test signal T1 output from the test signal generation unit 34 will not match the detection signal S1 and test signal T1 included in the demodulated signal ST3. Hereinafter, when it is necessary to clarify which detection signal S1 or test signal T1 is being referred to, the source of the detection signal S1 or test signal T1 will be described.

[0047] (7) First Connection Circuit The first connection circuit 32 includes a VI converter 321 and an AD converter 322. The VI converter 321 converts a voltage signal into a current signal. The VI converter 321 includes, for example, a transconductance amplifier. The AD converter 322 converts an analog signal into a digital signal.

[0048] An input terminal of the VI converter 321 is connected to an output terminal of the first demodulation circuit 42. An output terminal of the VI converter 321 is connected to an analog input terminal of the AD converter 322.

[0049] The demodulated signal ST3 output from the first demodulation circuit 42 is converted into a current signal by the VI converter 321 and then converted into a digital signal by the AD converter 322 .

[0050] (8) Detection Processing Circuit The input terminal of the detection processing circuit 33 is connected to the digital output terminal of the AD converter 322. The detection processing circuit 33 generates an angular velocity signal representing the angular velocity of the vibrator 10 based on the demodulated signal ST3. More specifically, the digital signal output from the AD converter 322 is the demodulated signal ST3 in digital format, and is input to the detection processing circuit 33. The demodulated signal ST3 includes a signal demodulated from the test signal T1 and a signal demodulated from the detection signal S1. The signal demodulated from the detection signal S1 is a signal corresponding to the magnitude of the angular velocity of the vibrator 10 and corresponds to the angular velocity signal.

[0051] The detection processing circuit 33 removes the test signal component from the digital signal output from the first connection circuit 32 using a low-pass filter or the like, and extracts the angular velocity signal component, thereby generating an angular velocity signal.

[0052] (9) First Diagnostic Circuit The first diagnostic circuit 61 includes a band-pass filter (BPF) 611 and a comparator (CP) 612 .

[0053] An input terminal of the bandpass filter 611 is connected to the digital output terminal of the AD converter 322. The bandpass filter 611 receives the demodulated signal ST3 via the input terminal and extracts the test signal T1 from the demodulated signal ST3.

[0054] The comparator 612 evaluates the magnitude of the amplitude of the test signal T1 extracted by the band-pass filter 611. Specifically, the comparator 612 determines whether the amplitude is within a predetermined range. If the amplitude is within the predetermined range, the comparator 612 outputs a first signal, and if the amplitude is outside the predetermined range, the comparator 612 outputs a second signal. The first signal is a signal indicating that the circuit from the test signal generation unit 34 to the first diagnostic circuit 61 is in a normal state. The second signal is a signal indicating that the circuit from the test signal generation unit 34 to the first diagnostic circuit 61 is in an abnormal state. For example, if the gain of the circuit is abnormal, the comparator 612 outputs the second signal.

[0055] The circuitry from the test signal generating unit 34 to the first diagnostic circuit 61 includes the test signal generating unit 34, the conversion circuit 41, the first demodulation circuit 42, the first connection circuit 32, and the first diagnostic circuit 61. That is, the first diagnostic circuit 61 uses the test signal T1 to determine whether or not there is an abnormality in these circuits.

[0056] The comparator 612 outputs the determination result (the first signal or the second signal) to, for example, a storage device. The storage device stores the determination result. The storage device stores the determination result together with information on the time when the determination was made, for example.

[0057] (10) Detection Feedback Circuit The detection feedback circuit 43 includes a chopper circuit 431, a VI converter 432, a circuit 433, and a transimpedance amplifier 434. The detection feedback circuit 43 is inserted between the first demodulation circuit 42 and the detection control electrode 23. That is, the input terminal and the output terminal of the detection feedback circuit 43 are connected to the first demodulation circuit 42 and the detection control electrode 23, respectively.

[0058] The demodulated signal ST3 output from the first demodulation circuit 42 is input to the detection feedback circuit 43. The detection feedback circuit 43 generates voltages to be applied to the two detection control electrodes 23 based on the demodulated signal ST3.

[0059] The chopper circuit 431, used in conjunction with the circuit 433, reduces noise from the VI converter 432 that is superimposed on the demodulated signal ST3 output from the first demodulation circuit 42. The VI converter 432 converts the demodulated signal ST3, which is output as a voltage signal from the chopper circuit 431, into a current signal. The circuit 433 includes a modulator that performs amplitude modulation (AM) on the demodulated signal ST3 using the drive signal D1 as a carrier wave. The transimpedance amplifier 434 converts the demodulated signal ST3, modulated by the drive signal D1, from a current signal to a voltage signal.

[0060] The output terminal of the transimpedance amplifier 434 is connected to the two detection control electrodes 23. The output terminal of the transimpedance amplifier 434 is also connected to the third diagnostic circuit 63.

[0061] When a voltage is applied from the detection feedback circuit 43 to the two detection control electrodes 23, the amplitude of the resonant vibration of the vibrator 10, which corresponds to the angular velocity of the vibrator 10, decreases. As a result, the amplitude of the detection signal S1 decreases relative to the magnitude of the angular velocity of the vibrator 10. Therefore, the gyro sensor 1 can detect larger angular velocities. In other words, the dynamic range of the gyro sensor 1 is expanded.

[0062] (11) Third Diagnostic Circuit The third diagnostic circuit 63 includes a demodulation circuit 634 , a low-pass filter (LPF) 631 , and a comparator 632 .

[0063] The input terminal of the demodulation circuit 634 is connected to the output terminal of the transimpedance amplifier 434. The demodulation circuit 634 demodulates the signal output from the detection feedback circuit 43 using the drive signal D1.

[0064] The input terminal of the low-pass filter 631 is connected to the output terminal of the demodulation circuit 634. The low-pass filter 631 extracts the test signal T1 from the signal demodulated by the demodulation circuit 634.

[0065] The comparator 632 evaluates the magnitude of the amplitude of the test signal T1 extracted by the low-pass filter 631. Specifically, the comparator 632 determines whether the amplitude is within a predetermined range. If the amplitude is within the predetermined range, the comparator 632 outputs a first signal. If the amplitude is outside the predetermined range, the comparator 632 outputs a second signal. The first signal is a signal indicating that the circuit from the test signal generation unit 34 to the third diagnostic circuit 63 is in a normal state. The second signal is a signal indicating that the circuit from the test signal generation unit 34 to the third diagnostic circuit 63 is in an abnormal state. For example, if the gain of the circuit is abnormal, the comparator 632 outputs the second signal.

[0066] The circuits from the test signal generating unit 34 to the third diagnostic circuit 63 include the test signal generating unit 34, the conversion circuit 41, the first demodulation circuit 42, the detection feedback circuit 43, and the third diagnostic circuit 63. That is, the third diagnostic circuit 63 uses the test signal T1 to determine whether or not there is an abnormality in these circuits.

[0067] The comparator 632 outputs the determination result (the first signal or the second signal) to, for example, a storage device. The storage device stores the determination result. The storage device stores the determination result together with information about the time when the determination was made, for example.

[0068] (12) Second Demodulation Circuit The second demodulation circuit 51 includes a phase shifter 511 and a mixer 512 .

[0069] The phase shifter 511 shifts the phase of the drive signal D1 and outputs it to the mixer 512. More specifically, the phase shifter 511 shifts the phase of the drive signal D1 by 90 degrees and outputs it to the mixer 512.

[0070] The input terminal of the mixer 512 is connected to the electrical path between the conversion circuit 41 and the first demodulation circuit 42. The signal ST2 is input from the conversion circuit 41 to the mixer 512. The mixer 512 demodulates the signal ST2 using the signal input from the phase shifter 511. As a result, the second demodulation circuit 51 generates a demodulated signal ST4 by demodulating the signal component of the signal ST2 output from the conversion circuit 41 that has a different phase from the drive signal D1.

[0071] (13) Second Connection Circuit The second connection circuit 52 includes an amplifier 521 and an AD converter 522 .

[0072] The input terminal of the amplifier 521 is connected to the output terminal of the second demodulation circuit 51. The amplifier 521 amplifies the demodulated signal ST4 output from the second demodulation circuit 51. The output terminal of the amplifier 521 is connected to the analog input terminal of the AD converter 522. The AD converter 522 converts the demodulated signal ST4 output from the amplifier 521 from an analog signal to a digital signal.

[0073] (14) Second Diagnostic Circuit The second diagnostic circuit 62 includes a band-pass filter 621 and a comparator 622 .

[0074] The input terminal of the bandpass filter 621 is connected to the digital output terminal of the AD converter 522. The bandpass filter 621 receives the demodulated signal ST4 via the input terminal. The bandpass filter 621 extracts the signal component of the test signal T1 from the demodulated signal ST4. Note that if the circuitry from the test signal generating unit 34 to the second diagnostic circuit 62 is normal, the demodulated signal ST4 does not include the signal component of the test signal T1.

[0075] The comparator 622 evaluates the magnitude of the amplitude of the signal component of the test signal T1 extracted by the band-pass filter 621. Specifically, the comparator 622 determines whether the amplitude is greater than a threshold. If the amplitude is smaller than the threshold, the comparator 622 outputs a first signal, and if the amplitude is equal to or greater than the threshold, the comparator 622 outputs a second signal. The first signal is a signal indicating that the circuit from the test signal generation unit 34 to the second diagnostic circuit 62 is in a normal state. The second signal is a signal indicating that the circuit from the test signal generation unit 34 to the second diagnostic circuit 62 is in an abnormal state. For example, if the gain of the circuit is abnormal, the comparator 622 outputs the second signal.

[0076] The circuitry from the test signal generating unit 34 to the second diagnostic circuit 62 includes the test signal generating unit 34, the conversion circuit 41, the second demodulation circuit 51, the second connection circuit 52, and the second diagnostic circuit 62. That is, the second diagnostic circuit 62 uses the test signal T1 to determine whether or not there is an abnormality in these circuits.

[0077] The comparator 622 outputs the determination result (the first signal or the second signal) to, for example, a storage device. The storage device stores the determination result. The storage device stores the determination result together with information on the time when the determination was made, for example.

[0078] (15) Quadrature Feedback Circuit The quadrature feedback circuit 53 includes a low-pass filter 531 .

[0079] The demodulated signal ST4 output from the second connection circuit 52 is input to the quadrature feedback circuit 53. The quadrature feedback circuit 53 generates voltages to be applied to the two quadrature correction electrodes 24 based on the demodulated signal ST4.

[0080] The input terminal of the low-pass filter 531 is connected to the output terminal of the second connection circuit 52. The output terminal of the low-pass filter 531 is connected to the two quadrature correction electrodes 24. The low-pass filter 531 removes high-frequency components, including the test signal components, from the demodulated signal ST4.

[0081] The quadrature feedback circuit 53 applies voltage to the two quadrature correction electrodes 24, thereby suppressing the second-order mode motion of the vibrator 10. The second-order mode motion causes the detection signal S1 to include a signal component (quadrature signal) that is out of phase with the drive signal D1.

[0082] (16) Locations where the diagnostic circuits are connected Each of the three diagnostic circuits 6 is connected to the subsequent stage (output side) of the conversion circuit 41. The subsequent stage of the first demodulation circuit 42 specifically includes the following first to third electrical paths. The first electrical path is from the conversion circuit 41 to the detection processing circuit 33 via the first demodulation circuit 42 and first connection circuit 32. The second electrical path is from the conversion circuit 41 to the two detection control electrodes 23 via the first demodulation circuit 42 and detection feedback circuit 43. The third electrical path is from the conversion circuit 41 to the two quadrature correction electrodes 24 via the second demodulation circuit 51, second connection circuit 52, and quadrature feedback circuit 53.

[0083] The first diagnostic circuit 61 has two input terminals 613 connected to the electrical path between the first demodulation circuit 42 and the detection processing circuit 33 .

[0084] The third diagnostic circuit 63 has an input terminal 633 connected to the electrical path between the detection feedback circuit 43 and the two detection control electrodes 23 .

[0085] The second demodulation circuit 51 has an input terminal 513 connected to the electrical path between the conversion circuit 41 and the first demodulation circuit 42. The second demodulation circuit 51 generates a quadrature signal by demodulating a signal component of the detection signal S1 converted by the conversion circuit 41 that has a different phase from the drive signal D1. The quadrature signal is included in the demodulated signal ST4.

[0086] The quadrature feedback circuit 53 is inserted between the second demodulation circuit 51 and the two quadrature correction electrodes 24. The quadrature feedback circuit 53 generates a voltage to be applied to the quadrature correction electrodes 24 based on the quadrature signal generated by the second demodulation circuit 51.

[0087] The second diagnostic circuit 62 has an input terminal 623 connected to the electrical path between the second demodulation circuit 51 and the quadrature feedback circuit 53 .

[0088] Each of the first to third diagnostic circuits 61 to 63 generates a fault diagnosis signal representing the result of the fault diagnosis of the control unit U1 based on the test signal T1. The first and second signals described above are examples of fault diagnosis signals.

[0089] (17) Detection Loop Circuit As described above, the detection loop circuit L1 includes the vibrator 10, the conversion circuit 41, the first demodulation circuit 42, and the detection feedback circuit 43. The gain of the detection loop circuit L1 is the rate of change in the magnitude of a signal when the signal makes one circuit around the detection loop circuit L1. The gain of the detection loop circuit L1 is determined by the circuit configuration and the Q value of the vibrator 10, etc. Furthermore, the gain of the detection loop circuit L1 depends on the frequency.

[0090] The frequency of the test signal T1 is outside the response range of the detection loop circuit L1. Preferably, the response range of the detection loop circuit L1 is a range in which the gain of the detection loop circuit L1 is 0 dB or less. In other words, in this case, the response range of the detection loop circuit L1 is a range in which the gain of the detection loop circuit L1 is greater than 0 dB.

[0091] In this embodiment, it is assumed that the test signal T1 is a signal of a single frequency. If the gain in the detection loop circuit L1 is 0 dB or less at the frequency of the test signal T1, the frequency of the test signal T1 is outside the response range of the detection loop circuit L1. On the other hand, if the gain in the detection loop circuit L1 is greater than 0 dB at the frequency of the test signal T1, the frequency of the test signal T1 is within the response range of the detection loop circuit L1.

[0092] When the test signal T1 includes signals of multiple frequencies, the gain of the detection loop circuit L1 is maximized at a specific frequency of the test signal T1. If the gain of the detection loop circuit L1 is 0 dB or less at the specific frequency, the frequency of the test signal T1 is outside the response range of the detection loop circuit L1. On the other hand, if the gain of the detection loop circuit L1 is greater than 0 dB at the specific frequency, the frequency of the test signal T1 is within the response range of the detection loop circuit L1.

[0093] It is more preferable that the "outside the response range of the detection loop circuit L1" be a range in which the gain of the detection loop circuit L1 is -3 dB or less. In this case, the test signal T1 attenuates more rapidly, thereby reducing the possibility that the test signal T1 will affect the angular velocity signal.

[0094] (18) Test Signal The frequency of the drive signal D1 is assumed to be, for example, 1 MHz or more and 10 MHz or less. The drive signal D1 drives the vibrator 10 to vibrate.

[0095] The frequency of the test signal T1 is assumed to be, for example, 10 kHz or more and 100 kHz or less. If the frequency of the test signal T1 is within this range, it is easy to design the vibrator 10 to be insensitive to the test signal T1. Furthermore, if the frequency of the test signal T1 is within this range, the frequency of the test signal T1 is significantly different from the frequency of the angular velocity signal, which is a DC component, so the test signal T1 can be easily extracted by the band-pass filters 611, 621 and the low-pass filter 631 of each of the three diagnostic circuits 6. Therefore, the performance required of the band-pass filters 611, 621 and the low-pass filter 631 is also relatively low.

[0096] In the configuration of the comparative example described above, the test signal T1 needs to be a low-frequency signal in order to vibrate the vibrator 10 with the test signal T1, and a low-pass filter with a low cutoff frequency is required to extract the test signal T1 from a signal that includes the test signal T1 and the angular velocity signal, which reduces the response speed when detecting the test signal T1. The gyro sensor 1 of this embodiment solves this problem by setting the frequency of the test signal T1 to a frequency outside the response range of the detection loop circuit L1.

[0097] (19) Modification of Test Signal Generator A test signal generator 34A according to a modification is shown in Fig. 2. Components similar to those of the test signal generator 34 in Fig. 1 are given the same reference numerals and will not be described again.

[0098] 2, the test signal generating unit 34A includes two T-type network resistors 345 instead of the two resistors 342. The test signal T1 generated by the circuit 341 passes through the two T-type network resistors 345 and is output from two output terminals 344.

[0099] Each of the two T-type resistor networks 345 includes resistors R1, R2, and R3. The resistors R1 and R3 are connected in series at a connection point N1. A resistor R2 is inserted between the connection point N1, which is the electrical path between the resistors R1 and R3, and ground. A series circuit made up of the resistors R1 and R3 connected in series is inserted between the output terminal of the circuit 341 and the capacitor 343. Note that the ground referred to here includes an AC (alternating current) ground and a reference potential in the control unit U1.

[0100] According to this modified example, the resistance values ​​of the resistors R1, R2, and R3 used can be reduced, reducing the effect of the parasitic capacitance of the resistors R1, R2, and R3, and thereby allowing the test signal generating unit 34A to output a relatively small current signal as the test signal T1.

[0101] (20) Other Modifications Other modifications of the embodiment are listed below. The following modifications may be realized in appropriate combination. The following modifications may also be realized in appropriate combination with the above-described modifications. Hereinafter, the configuration of the above-described embodiment will be referred to as a basic example.

[0102] The conversion circuit 41 may further include a current buffer inserted between the transimpedance amplifier 411 and the two detection electrodes 22 .

[0103] It is not essential that the gyro sensor 1 includes two each of the drive electrodes 21, the detection electrodes 22, the detection control electrodes 23, and the quadrature correction electrodes 24. The number of each of the drive electrodes 21, the detection electrodes 22, the detection control electrodes 23, and the quadrature correction electrodes 24 may be one, or three or more.

[0104] The transimpedance amplifier 411 of the conversion circuit 41 may be a differential transimpedance amplifier.

[0105] The location where the diagnostic circuit 6 is installed is not limited to the location shown in the basic example, as long as it is located after the conversion circuit 41. The number of diagnostic circuits 6 may be one, two, four or more.

[0106] In the basic example, the test signal T1 is output to the third diagnostic circuit 63 and is attenuated to such an extent that it can be regarded as a zero level in the vibrator 10. As another example, the test signal T1 may be attenuated to such an extent that it can be regarded as a zero level in the detection feedback circuit 43. In this case, the third diagnostic circuit 63 may be omitted, or the input terminal 633 of the third diagnostic circuit 63 may be connected to an electrical path within the detection feedback circuit 43.

[0107] The block diagrams shown in FIGS. 1 and 2 are merely examples of the configuration of the gyro sensor 1 according to the present disclosure, and circuits may be added or omitted as appropriate.

[0108] The control unit U1 does not necessarily have to include the quadrature loop circuit L2, and therefore does not necessarily have to include the second demodulation circuit 51, the second connection circuit 52, the second diagnostic circuit 62, and the quadrature feedback circuit 53.

[0109] The entity executing the gyro sensor 1 or the method of using the gyro sensor 1 according to the present disclosure may include a computer system. The computer system is primarily composed of a processor and memory as hardware. At least a portion of the functions of the entity executing the gyro sensor 1 or the method of using the gyro sensor 1 according to the present disclosure are realized by the processor executing a program stored in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided by being recorded on a non-transitory recording medium readable by the computer system, such as a memory card, optical disk, or hard disk drive. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits, such as ICs and LSIs, are referred to by different names depending on the degree of integration, and include integrated circuits called system LSIs, very large-scale integration (VLSI), or ultra-large-scale integration (ULSI). Furthermore, a field-programmable gate array (FPGA), which is programmed after the LSI is manufactured, or a logic device capable of reconfiguring the connections within the LSI or the circuit partitions within the LSI, can also be employed as a processor. Multiple electronic circuits may be integrated into a single chip or distributed across multiple chips. Multiple chips may be integrated into a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits, including a semiconductor integrated circuit or a large-scale integrated circuit.

[0110] Furthermore, it is not essential for the gyro sensor 1 that multiple functions are concentrated in one housing, and multiple components of the gyro sensor 1 may be distributed across multiple housings.

[0111] Conversely, in the embodiment, at least some of the functions of the gyro sensor 1 that are distributed across multiple housings may be integrated into one housing.

[0112] (Summary) The above-described embodiments and the like disclose the following aspects.

[0113] A gyro sensor (1) according to a first aspect includes a vibrator (10), a plurality of electrodes (2), and a control unit (U1). The plurality of electrodes (2) include a drive electrode (21), a detection electrode (22), and a detection control electrode (23). The plurality of electrodes (2) are arranged to face the vibrator (10) and form a capacitance between the vibrator (10). The control unit (U1) is connected to the drive electrode (21), the detection electrode (22), and the detection control electrode (23). The control unit (U1) includes a drive circuit (31), a conversion circuit (41), a demodulation circuit (42), a detection feedback circuit (43), a detection processing circuit (33), a test signal generation unit (34; 34A), and one or more diagnostic circuits (6). The drive circuit (31) outputs a drive signal (D1) to the drive electrode (21) to induce drive vibration of the vibrator (10). The conversion circuit (41) converts the detection signal (S1) output from the detection electrode (22). The demodulation circuit (42) is connected downstream of the conversion circuit (41) and generates a demodulated detection signal by demodulating a signal component in phase with the drive signal (D1) from the detection signal (S1) converted by the conversion circuit (41). The detection feedback circuit (43) is inserted between the demodulation circuit (42) and the detection control electrode (23) and generates a voltage to be applied to the detection control electrode (23) based on the demodulated detection signal. The detection processing circuit (33) is connected downstream of the demodulation circuit (42) and generates an angular velocity signal representing the angular velocity of the vibrator (10) based on the demodulated detection signal. The test signal generation unit (34; 34A) has an output terminal (344) connected to the electrical path between the detection electrode (22) and the conversion circuit (41) and outputs a test signal (T1) for fault diagnosis to the conversion circuit (41) via the output terminal (344). One or more diagnostic circuits (6) are connected downstream of the conversion circuit (41) and generate a fault diagnosis signal representing the result of fault diagnosis of the control unit (U1) based on a test signal (T1). The frequency of the test signal (T1) is outside the response range of a detection loop circuit (L1) including a vibrator (10), the conversion circuit (41), a demodulation circuit (42), and a detection feedback circuit (43).

[0114] According to the above configuration, the test signal (T1) is attenuated by circulating through the detection loop circuit (L1). This reduces the possibility that the test signal (T1) will affect the angular velocity signal. Furthermore, the test signal (T1) before attenuation can be used to diagnose a fault in the control unit (U1).

[0115] In addition, in the gyro sensor (1) according to the second aspect, in the first aspect, the test signal generating unit (34; 34A) outputs a signal in which the test signal (T1) is superimposed on the drive signal (D1) to the conversion circuit (41).

[0116] According to the above configuration, the drive signal (D1) is used to modulate the test signal (T1), so that the test signal (T1) can be easily demodulated.

[0117] In the gyro sensor (1) according to the third aspect, in the first or second aspect, the conversion circuit (41) includes a transimpedance amplifier (411).

[0118] According to the above configuration, the connection between the test signal generating section (34; 34A) and the conversion circuit (41) can be made simple in configuration.

[0119] In addition, in the gyro sensor (1) according to the fourth aspect, in any one of the first to third aspects, the test signal generating unit (34; 34A) includes a capacitor (343) that cuts the DC component of the test signal (T1).

[0120] According to the above configuration, it is possible to prevent the conversion circuit (41) and the test signal generation unit (34; 34A) from sharing a DC bias.

[0121] In addition, in the gyro sensor (1) according to the fifth aspect, in any one of the first to fourth aspects, the test signal generating section (34A) includes a T-type network resistor (345) through which the test signal (T1) passes.

[0122] According to the above configuration, the test signal generating section (34A) can output a relatively small current signal as the test signal (T1).

[0123] In addition, in the gyro sensor (1) according to the sixth aspect, in any one of the first to fifth aspects, one diagnostic circuit (61) of the one or more diagnostic circuits (6) has an input terminal (613) connected to an electrical path between the demodulation circuit (42) and the detection processing circuit (33).

[0124] According to the above configuration, the diagnostic circuit (61) can diagnose faults in the upstream (input side) of the detection processing circuit (33).

[0125] In addition, in the gyro sensor (1) according to the seventh aspect, in any one of the first to sixth aspects, another diagnostic circuit (63) of the one or more diagnostic circuits (6) has an input terminal (633) connected to an electrical path between the detection feedback circuit (43) and the detection control electrode (23).

[0126] According to the above configuration, the diagnostic circuit (63) can diagnose failures in the stage preceding the detection control electrode (23).

[0127] In addition, in a gyro sensor (1) according to an eighth aspect, in any one of the first to seventh aspects, the plurality of electrodes (2) further includes a quadrature correction electrode (24). The demodulation circuit (42) is a first demodulation circuit (42). The control unit (U1) further includes a second demodulation circuit (51) and a quadrature feedback circuit (53). The second demodulation circuit (51) has an input terminal (513) connected to an electrical path between the conversion circuit (41) and the first demodulation circuit (42). The second demodulation circuit (51) generates a quadrature signal by demodulating a signal component of the detection signal (S1) converted by the conversion circuit (41) that has a phase different from that of the drive signal (D1). The quadrature feedback circuit (53) is inserted between the second demodulation circuit (51) and the quadrature correction electrode (24). The quadrature feedback circuit (53) generates a voltage to be applied to the quadrature correction electrode (24) based on the quadrature signal. A further diagnostic circuit (62) of the one or more diagnostic circuits (6) has an input terminal (623) connected to the electrical path between the second demodulation circuit (51) and the quadrature feedback circuit (53).

[0128] According to the above configuration, the diagnostic circuit (62) can diagnose failures in the stage preceding the quadrature feedback circuit (53).

[0129] The configurations other than the first aspect are not essential for the gyro sensor (1) and can be omitted as appropriate.

[0130] 1 Gyro sensor 2 Electrode 6, 61, 62, 63 Diagnostic circuit 10 Vibrator 21 Drive electrode 22 Detection electrode 23 Detection control electrode 24 Quadrature correction electrode 31 Drive circuit 33 Detection processing circuit 34, 34A Test signal generation unit 41 Conversion circuit 42 Demodulation circuit (first demodulation circuit) 43 Detection feedback circuit 51 Second demodulation circuit 53 Quadrature feedback circuit 343 Capacitor 344 Output terminal 345 T-type network resistor 411 Transimpedance amplifier 513 Input terminal 613, 623, 633 Input terminal D1 Drive signal L1 Detection loop circuit S1 Detection signal T1 Test signal U1 Control unit

Claims

1. A device comprising: a vibrator; a plurality of electrodes including a drive electrode, a detection electrode, and a detection control electrode, the electrodes being arranged to face the vibrator and forming a capacitance between the vibrator and the plurality of electrodes; and a control unit connected to the drive electrode, the detection electrode, and the detection control electrode, the control unit comprising: a drive circuit which outputs a drive signal to the drive electrode to induce drive vibration of the vibrator; a conversion circuit which converts the detection signal output from the detection electrode; a first demodulation circuit connected to a stage downstream of the conversion circuit and which generates a demodulated detection signal by demodulating a signal component in phase with the drive signal from the detection signal converted by the conversion circuit; a detection feedback circuit which is inserted between the first demodulation circuit and the detection control electrode and which generates a voltage to be applied to the detection control electrode based on the demodulated detection signal; a detection processing circuit which is connected to a stage downstream of the first demodulation circuit and which generates an angular velocity signal representing the angular velocity of the vibrator based on the demodulated detection signal; and a test signal generation unit which has an output terminal connected to an electric path between the detection electrode and the conversion circuit and which outputs a test signal for fault diagnosis to the conversion circuit via the output terminal. A gyro sensor comprising: one or more diagnostic circuits connected downstream of the conversion circuit and configured to generate a fault diagnosis signal representing a result of fault diagnosis of the control unit based on the test signal, wherein the frequency of the test signal is outside the response range of a detection loop circuit including the vibrator, the conversion circuit, the first demodulation circuit, and the detection feedback circuit.

2. The gyro sensor according to claim 1, wherein the test signal generating section outputs a signal obtained by superimposing the test signal on the drive signal to the conversion circuit.

3. The gyro sensor according to claim 1, wherein the conversion circuit includes a transimpedance amplifier.

4. The gyro sensor according to claim 1, wherein the test signal generating section includes a capacitor that cuts off a DC component of the test signal.

5. The gyro sensor according to claim 1, wherein the test signal generating section includes a T-type network resistor through which the test signal passes.

6. The gyro sensor according to claim 1, wherein one of the one or more diagnostic circuits has an input terminal connected to an electric path between the first demodulation circuit and the detection processing circuit.

7. The gyro sensor according to claim 1, wherein another of the one or more diagnostic circuits has an input terminal connected to an electric path between the detection feedback circuit and the detection control electrode.

8. A gyro sensor as described in claim 1, wherein the plurality of electrodes further include a quadrature correction electrode, and the control unit further comprises: a second demodulation circuit having an input terminal connected to an electrical path between the conversion circuit and the first demodulation circuit, and generating a quadrature signal by demodulating a signal component of the detection signal converted by the conversion circuit that has a different phase from the drive signal; and a quadrature feedback circuit inserted between the second demodulation circuit and the quadrature correction electrode, and generating a voltage to be applied to the quadrature correction electrode based on the quadrature signal, and yet another diagnostic circuit of the one or more diagnostic circuits has an input terminal connected to the electrical path between the second demodulation circuit and the quadrature feedback circuit.

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