JP2006329634A - Device for detecting angular velocity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting angular velocity capable of suppressing the deterioration of detection sensitivity of angular velocity and reducing an offset voltage. <P>SOLUTION: The device comprises a vibration control circuit 6 producing a drive signal for vibrating a vibrator, a gyroscope sensor 101 for vibrating the vibrator on the basis of the drive signal, a sensor IF circuit 3 for outputting the detected signal indicating detected Coriolis force by detecting the Coriolis force caused by applying the angular velocity in the vibrator, a second synchronized detection circuit 5 producing the angular velocity signal F indicating the angular velocity by synchronizing-detecting the detection signal based on the specific reference signal, a switched-capacitor circuit for storing initial value information based on the angular velocity signal F while the angular velocity is not applied in the vibrator, and a phase controller 10 for producing the reference signal by varying the phase of the drive signal so as to lower the level of the angular velocity signal F accordingly to the initial value information and outputting to the second synchronizing-detection circuit 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an angular velocity detection device that measures an angular velocity by measuring a Coriolis force when an angular velocity due to an external force is applied to a vibrating body that is vibrated at a predetermined cycle.

  In recent years, angular velocity detection devices using gyro sensors have been used in suspension and airbag control devices in automobiles, inertial navigation systems in aircraft, camera shake correction devices for cameras, and the like. As this type of angular velocity detection device, angular velocity detection using a vibrating gyro sensor that measures the angular velocity by measuring the Coriolis force when an angular velocity due to an external force acts on a mass body vibrated with a predetermined amplitude and period. An apparatus is known (for example, refer to Patent Document 1).

  FIG. 11 is a conceptual diagram for explaining a configuration of an angular velocity detection device according to the background art. A gyro sensor 101 shown in FIG. 11 has a vibration body 102 made of a substantially rectangular parallelepiped conductor and a vibration in the X-axis direction when the X-axis is parallel to one side of the vibration body 102 as shown in FIG. Drive electrodes 103 and 104 disposed opposite to each other with the body 102 interposed therebetween, and detection electrodes 105 and 106 disposed opposite to each other with the vibrating body 102 interposed in the Y-axis direction orthogonal to the X-axis. Yes. The driving electrodes 103 and 104 and the detection electrodes 105 and 106 are respectively arranged so as to face one surface of the vibrating body 102 with an interval, and electrostatic capacitances C103, C104, C105, and C106 are respectively provided between the driving body 103 and the vibrating body 102. Is formed.

  FIG. 12 is an explanatory diagram for explaining the operation of the gyro sensor 101. In the gyro sensor 101 shown in FIG. 11, when the driving voltage Vd1 having the resonance frequency of the vibrating body 102 is applied to the driving electrode 103 and the driving voltage Vd2 having a phase opposite to that of the driving voltage Vd1 is applied to the driving electrode 104. A periodic electrostatic force is generated between the vibrating body 102 and the driving electrodes 103 and 104, and the vibrating body 102 vibrates along the X-axis direction. In this state, when an angular velocity R is applied to the gyro sensor 101 about an axis perpendicular to the paper surface, a Coriolis force is generated in the Y-axis direction, and the vibrating body 102 is displaced in the Y-axis direction according to the Coriolis force. When the vibrating body 102 is displaced in the Y-axis direction, the capacitances C105 and C106 between the vibrating body 102 and the detection electrodes 105 and 106 change. Accordingly, the capacitances C105 and C106 change according to the angular velocity applied to the gyro sensor 101.

  FIGS. 13 and 14 are explanatory diagrams for explaining the operating principle of the angular velocity detection device using the gyro sensor 101. FIG. In FIG. 13, a current-voltage conversion circuit 112 that outputs a detection signal Vo obtained by converting a current Iin flowing out from the vibration body 102 into a voltage signal is connected to the vibration body 102. Then, the driving voltages Vd1 and Vd2 are applied to the driving electrodes 103 and 104, and a periodic electrostatic force is generated between the vibrating body 102 and the driving electrodes 103 and 104. Vibrates along the direction. The frequencies of the driving voltages Vd1 and Vd2 are set to the resonance frequency of the vibrating body 102, and the vibrating body 102 vibrates at the resonance frequency.

  FIG. 14 shows the signal waveform of the driving voltage Vd1 and the amount of displacement of the vibrating body 102 in the driving vibration direction (X-axis direction) when the vibrating body 102 vibrates in this way. In this case, the phase of the signal waveform of the driving voltage Vd1 and the amount of displacement of the vibrating body 102 are different by 90 degrees.

  Carrier signals Vc1 and Vc2 having predetermined frequencies for detecting the capacitances C105 and C106 are applied to the detection electrodes 105 and 106, respectively. As shown in FIG. 14, the carrier signal Vc1 and the carrier signal Vc2 are signals that are 180 degrees out of phase with each other. When an angular velocity is applied to the vibrating body 102, a Coriolis force acts on the vibrating body 102, and the Coriolis force is generated, that is, displaced in the Y-axis direction.

First, as shown in FIG. 13A, in the state where the vibrating body 102 is positioned between the detection electrodes 105 and 106 (state 1), the facing distance between the vibrating body 102 and the detection electrodes 105 and 106 is as follows. Since they are equal, the capacitance C105 and the capacitance C106 are equal. As a result, the current I ₁₀₅ flowing through the capacitance C105 according to the carrier signal Vc1 and the current I ₁₀₆ flowing through the capacitance C106 according to the carrier signal Vc2 are equal to each other, so that the current I ₁₀₅ and the current I ₁₀₆ are canceled out. Thus, the current Iin becomes substantially zero, and the detection signal Vo output from the current-voltage conversion circuit 112 also becomes substantially zero.

Next, as illustrated in FIG. 13B, in the state where the vibrating body 102 is displaced in the direction of the detection electrode 105 due to the Coriolis force (state 2), the distance between the vibrating body 102 and the detection electrode 105 is the vibration body 102. Therefore, the electrostatic capacity C105 is larger than the electrostatic capacity C106. Then, a difference occurs between the current _{I 105} and the current _{I 106,} current corresponding to the difference between the current _{I 105} and the current _{I 106} is obtained as a current Iin, the detection signal output from the current-voltage conversion circuit 112 Vo rises.

  Next, as shown in FIG. 13C, the vibration body 102 returns to a state (state 3) located between the detection electrodes 105 and 106, and the detection signal Vo is substantially zero as in the state 1. Become.

Next, as illustrated in FIG. 13D, in the state where the vibrating body 102 is displaced in the direction of the detection electrode 106 due to the Coriolis force (state 4), the distance between the vibrating body 102 and the detection electrode 106 is the vibration body 102. Therefore, the capacitance C106 is larger than the capacitance C105. Then, a difference occurs between the current _{I 105} and the current _{I 106,} current corresponding to the difference between the current _{I 105} and the current _{I 106} is obtained as a current Iin, the detection signal output from the current-voltage conversion circuit 112 Vo rises.

  As described above, when the vibrating body 102 vibrates and the states 1 to 4 are repeated, the detection signals in which the carrier signals Vc1 and Vc2 are modulated by the displacement amount due to the Coriolis force of the vibrating body 102 as shown in FIG. Obtained as Vo.

  Furthermore, by synchronously detecting the detection signal Vo based on the carrier signal Vc1, a carrier signal component is removed from the detection signal Vo to generate a signal Vx1, and by synchronously detecting the signal Vx1 based on the driving voltage Vd1 The signal Vx2 indicating the angular velocity applied to the vibrating body 102 is detected.

  By the way, if the resonance frequency of the vibrating body 102 fluctuates due to the influence of the environment such as the ambient temperature or variations in processing accuracy of the vibrating body 102, the phase of the detection signal Vo obtained from the vibrating body 102 is shifted, and the signal Vx1 The phase also shifts. Then, when the signal Vx1 is synchronously detected based on the driving voltage Vd1, a shift occurs in the relationship between the phase of the signal Vx1 and the phase of the driving voltage Vd1, and the offset voltage is added to the signal Vx2 after the synchronous detection. As a result, the detection accuracy of the angular velocity is lowered.

Therefore, in the angular velocity detection device according to the background art, for example, the angular velocity detection device described in Patent Document 1, the voltage of the angular velocity signal indicating the angular velocity in a state where the angular velocity is not applied to the vibrating body, that is, the offset voltage is supplied to the sample hold circuit. The offset voltage is corrected by subtracting the offset voltage held in the sample hold circuit from the voltage of the angular velocity signal obtained at the time of measuring the angular velocity.
JP 2001-241951 A

  By the way, in the angular velocity detection device configured as described above, when performing synchronous detection, there is a relationship between the phase of the detection signal obtained from the vibrating body and the phase of the driving voltage that is a reference for synchronous detection. Since the synchronous detection is performed with the shift, the signal component indicating the angular velocity to be detected is attenuated, resulting in a disadvantage that the sensitivity of detecting the angular velocity is lowered.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an angular velocity detection device capable of reducing an offset voltage while suppressing a decrease in angular velocity detection sensitivity.

  In order to achieve the above object, an angular velocity detection device according to the present invention includes a vibration control unit that generates a drive signal for vibrating a vibrating body at a constant frequency, and a drive signal generated by the vibration control unit. Based on a drive unit that vibrates the vibrating body, a detection unit that detects Coriolis force generated by applying an angular velocity to the vibrating body, and outputs a detection signal indicating the detected Coriolis force, A synchronous detection unit that generates an angular velocity signal indicating an angular velocity applied to the vibrating body from a detection signal output from the detection unit by performing synchronous detection based on a reference signal that indicates vibration timing; and an angular velocity applied to the vibrating body A storage unit for storing initial value information based on an angular velocity signal generated by the synchronous detection unit in a state in which no is applied, and initial value information stored by the storage unit And a phase adjustment unit that generates the reference signal by changing the phase of the drive signal generated by the vibration control unit so as to reduce the level of the angular velocity signal and outputs the reference signal to the synchronous detection unit. It is characterized by providing.

  In the above-described angular velocity detection device, the phase adjustment unit changes the phase of the drive signal using a switched capacitor circuit to generate the reference signal.

  Further, in the above-described angular velocity detection device, the phase adjustment unit changes the phase of the drive signal using a shift register to generate the reference signal.

In the angular velocity detection device having such a configuration, the Coriolis force generated by applying the angular velocity to the vibrating body is detected by the detection unit, and the detection signal detected by the detection unit is used as a reference signal indicating the vibration timing of the vibrating body. Based on the synchronous detection based on this, an angular velocity signal indicating the angular velocity applied to the vibrating body is generated. Then, the angular velocity signal generated by the synchronous detector in the state where the angular velocity is not applied to the vibrating body, that is, the initial value information based on the offset voltage is stored in the storage unit, and the angular velocity signal according to the stored initial value information Since the reference signal is generated by changing the phase of the drive signal generated by the vibration control unit so as to reduce the level of the reference, the reference voltage is generated so as to reduce the offset voltage generated in a state where the angular velocity is not applied to the vibrating body. The phase of the signal can be changed, and the offset voltage can be reduced while suppressing a decrease in angular velocity detection sensitivity due to a phase shift of the reference signal.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a block diagram showing an example of the configuration of the angular velocity detection device according to the first embodiment of the present invention. An angular velocity detection device 1 shown in FIG. 1 includes an oscillation source 2, a sensor interface circuit (hereinafter abbreviated as a sensor IF circuit) 3 (detection unit), a first synchronous detection circuit 4, and a second synchronous detection circuit 5 (synchronous detection unit). ), A vibration control circuit 6 (vibration control unit), an amplitude control unit 7, a switch SW1, an output conversion circuit 9, a phase adjustment unit 10, and an amplification circuit 11. The configuration of the gyro sensor 101 is the same as that of the gyro sensor 101 shown in FIG. In this case, the driving electrodes 103 and 104 correspond to an example of a driving unit in the claims.

  FIG. 2 is a circuit diagram showing an equivalent circuit of the gyro sensor 101. In the equivalent circuit of the gyro sensor 101 shown in FIG. 2, the capacitances C103, C104, C105, and C106 are connected to the vibrating body 102, and the driving voltages Vd1 and Vd2 output from the vibration control circuit 6 are the capacitances. By being supplied to C103 and C104, the vibrating body 102 vibrates along the X-axis direction. Then, when an angular velocity is applied to the vibrating body 102 to generate Coriolis force and the vibrating body 102 is displaced along the Y-axis direction, the capacitances C105 and C106 change.

  Returning to FIG. 1, the oscillation source 2 supplies a carrier signal Vc1 having a predetermined frequency for capacitance detection, for example, a frequency of 100 kHz, to the capacitance C105 (detection electrode 105) and the first phase detection unit 41. At the same time, a carrier signal Vc2 (second detection signal) having a phase opposite to that of the carrier signal Vc1 is supplied to the capacitance C106 (detection electrode 106). The frequencies of the carrier signals Vc1 and Vc2 are set higher than the resonance frequency of the vibrating body 102.

  The carrier signals Vc1 and Vc2 output from the oscillation source 2 are supplied to the capacitances C105 and C106, and the carrier signals Vc1 and Vc2 are modulated by changes according to the Coriolis forces of the capacitances C105 and C106. A is output to the sensor IF circuit 3 as A.

  The vibration control circuit 6 supplies a drive voltage Vd1 having a resonance frequency (natural frequency) of the vibrating body 102 to the capacitance C103 (drive electrode 103), and drives the capacitance C104 (drive electrode 104). A driving voltage Vd2 having a phase opposite to that of the voltage Vd1 is supplied. Thereby, the vibration control circuit 6 vibrates the vibrating body 102 along the X-axis direction at the resonance frequency. The resonance frequency of the vibrating body 102 is 2 kHz, for example. Further, the vibration control circuit 6 outputs the driving voltage Vd1 to the amplitude control unit 7.

  The amplitude control unit 7 is a circuit unit that converts the driving voltage Vd1 output from the vibration control circuit 6 into a signal level that can be processed by the phase adjustment unit 10 and outputs the signal level to the phase adjustment unit 10 as, for example, a signal. An amplifier circuit is used.

  The sensor IF circuit 3 is a circuit unit that converts the signal A output from the gyro sensor 101 into a signal format that can be processed by the first synchronous detection circuit 4, and outputs the signal A to the first synchronous detection circuit 4 as a detection signal B. For example, a signal conversion circuit such as a signal amplification circuit or a current-voltage conversion circuit is used.

  The first synchronous detection circuit 4 is a circuit unit that synchronously detects the detection signal B output from the sensor IF circuit 3 based on the carrier signal Vc1 output from the oscillation source 2, and includes a first phase detection unit 41 and a low-pass filter. (Hereinafter abbreviated as LPF) 42. The first phase detection unit 41 is, for example, a multiplier, which multiplies the detection signal B and the carrier signal Vc1 and outputs the result as a signal C to the LPF 42. The LPF 42 smoothes the signal C and outputs it as the signal D to the second synchronous detection circuit 5.

  The second synchronous detection circuit 5 is a circuit unit that performs synchronous detection on the signal D output from the first synchronous detection circuit 4 based on the signal J output from the phase adjustment unit 10 and having the same frequency as the driving voltage Vd1. The second phase detector 51 and the LPF 52 are provided. The second phase detector 51 is, for example, a multiplier, which multiplies the signal D and the signal J and outputs the result as the signal E to the LPF 52. The LPF 52 smoothes the signal E and outputs it as the angular velocity signal F to the switch SW1.

  The switch SW1 is a changeover switch having connection terminals T1, T2, and T3. The connection terminal T1 is connected to the second synchronous detection circuit 5, the connection terminal T2 is connected to the output conversion circuit 9, and the connection terminal T3 is an amplifier circuit. 11 is connected. The connection between the connection terminal T1 and the connection terminals T2 and T3 is switched according to the control signal Ssw1 output from the output conversion circuit 9.

  The output conversion circuit 9 stores the signal level of the angular velocity signal F generated by the second synchronous detection circuit 5 in the state where the angular velocity is not applied to the gyro sensor 101 as initial value information, and the signal stored as the initial value information. The level is converted into a signal format that can be processed by the subsequent phase adjustment unit 10 and output.

  FIG. 3 is a block diagram showing an example of the configuration of the output conversion circuit 9. The output conversion circuit 9 shown in FIG. 3 includes a switch control unit 91, a sample hold circuit 92 (storage unit), a VCO (Voltage Controlled Oscillator) 93, and a switch SW2. The switch SW2 is a changeover switch having connection terminals T4, T5, T6, the connection terminal T4 is connected to the sample hold circuit 92, the connection terminal T5 is connected to the connection terminal T2 of the switch SW1, and the connection terminal T6 is connected to the VCO 93. It is connected. The connection between the connection terminal T4 and the connection terminals T5 and T6 is switched according to the control signal Ssw2 output from the switch control unit 91.

  The sample and hold circuit 92 is a sample and hold circuit that holds the signal level of the angular velocity signal F generated by the second synchronous detection circuit 5 as initial value information when no angular velocity is applied to the gyro sensor 101. The VCO 93 outputs a signal VCO_Out having a frequency corresponding to the signal level of the angular velocity signal F held by the sample hold circuit 92 to the phase adjustment unit 10.

  The switch control unit 91 applies acceleration to the gyro sensor 101, for example, immediately after the angular velocity detection device 1 is activated or when an offset voltage correction instruction is received from a user by an operation switch (not shown) or the like. A control circuit that performs an operation in a normal operation phase that performs an operation in a phase adjustment phase for correcting an offset voltage in a state in which the offset voltage is corrected and outputs an angular velocity signal F that is an angular velocity detection signal to the outside when the offset voltage is corrected Thus, for example, a comparator or a logic circuit that detects the voltage of the angular velocity signal F is used.

  The phase adjustment unit 10 generates the reference signal J by changing the phase of the signal I output from the amplitude control unit 7 according to the frequency of the signal VCO_Out output from the VCO 93, and supplies the reference signal J to the second phase detection unit 51. Output.

  FIG. 4 is a circuit diagram illustrating an example of the phase adjustment unit 10. The phase adjustment unit 10 shown in FIG. 4 includes a switched capacitor circuit 12, an operational amplifier 13, resistors R1 and R2, and a capacitor C2. The switched capacitor circuit 12 includes switches SW3 and SW4 and a capacitor C1. The signal I output from the amplitude control unit 7 is supplied to the inverting input terminal of the operational amplifier 13 via the resistor R1 and also supplied to the non-inverting input terminal of the operational amplifier 13 via the switched capacitor circuit 12. The

  The output terminal of the operational amplifier 13 is connected to the inverting input terminal via the resistor R2, and the non-inverting input terminal of the operational amplifier 13 is connected to the ground via the capacitor C2. The resistance values of the resistors R1 and R2 are set to be equal, and the gain of the amplifier circuit is set to 1. Then, the output signal of the operational amplifier 13 is output to the second phase detector 51 as the reference signal J.

  As a result, the phase adjustment unit 10 changes the phase of the signal I by a change amount corresponding to the equivalent resistance value of the switched capacitor circuit 12 and outputs it as the reference signal J to the second phase detection unit 51. Has been.

  The switched capacitor circuit 12 is a so-called switched capacitor circuit in which a pseudo resistance value changes according to the frequency of the signal VCO_Out output from the VCO 93, and includes switches SW3 and SW4 and a capacitor C1. The switch SW3 is a changeover switch having connection terminals T7, T8, and T9. The connection terminal T7 is connected to one terminal of the capacitor C1, the connection terminal T8 is connected to the amplitude control unit 7, and the connection terminal T9 is connected to the ground. It is connected. The switch SW4 is a changeover switch having connection terminals T10, T11, and T12. The connection terminal T10 is connected to the other terminal of the capacitor C1, and the connection terminal T11 is connected to the non-inverting input terminal of the operational amplifier 13. The connection terminal T12 is connected to the ground.

  Then, the connection between the connection terminal T7 and the connection terminals T8 and T9 and the connection between the connection terminal T10 and the connection terminals T11 and T12 are switched according to the signal VCO_Out. In this case, the equivalent resistance value Rsw of the switched capacitor circuit 12 is given by the following equation (1).

Rsw = 1 / (f × C) (1)
Where f: frequency of signal VCO_Out C: capacitance of capacitor C1.

  As a result, the phase adjustment unit 10 changes the phase of the signal I by a change amount corresponding to the frequency of the signal VCO_Out output from the VCO 93 and outputs it as the reference signal J to the second phase detection unit 51. .

  Next, the operation of the angular velocity detection device 1 configured as described above will be described. FIG. 5 is a signal waveform diagram for explaining the operation of the angular velocity detection device 1. First, driving voltages Vd1 and Vd2 of 2 kHz, for example, are supplied from the vibration control circuit 6 to the gyro sensor 101, and the vibrating body 102 vibrates. Then, carrier signals Vc1 and Vc2 of, for example, 100 kHz are supplied from the oscillation source 2 to the gyro sensor 101, and the carrier signals Vc1 and Vc2 are modulated by a change according to the Coriolis force of the capacitances C105 and C106, and the sensor IF The signal A is output to the circuit 3, and the signal IF is subjected to conversion processing of a signal format such as current-voltage conversion by the sensor IF circuit 3 and is output to the first phase detection unit 41 as the signal B.

  Next, the first phase detector 41 multiplies the carrier signal Vc1 and the signal B to generate the signal C, and the signal C is further smoothed by the LPF 42 to generate the signal D. As a result, the first synchronous detection circuit 4 removes the signal components of the carrier signals Vc1 and Vc2 from the signal B to generate the signal D, which is output to the second phase detector 51.

  In this case, the signal D includes a signal component D1 that is a signal component indicating Coriolis force, and an unnecessary signal component D2 that is generated when the vibrating body 102 vibrates along the driving vibration direction (X-axis direction). It is. The signal component D1 and the signal component D2 are signals that are 90 degrees out of phase. In this case, since the driving voltage Vd1 and the signal component D1 have the same phase, the driving voltage Vd1 and the signal component D2 are signals whose phases are shifted by 90 degrees.

  On the other hand, the drive voltage Vd1 output from the vibration control circuit 6 is amplitude-adjusted by the amplitude control unit 7 and output to the phase adjustment unit 10 as the signal I, and the signal I is directly output from the phase adjustment unit 10 as the signal J to the second phase. It is output to the detection unit 51.

  FIG. 6 is a signal waveform diagram for explaining the operation of the second synchronous detection circuit 5. FIG. 6 shows a signal waveform when no acceleration is applied to the gyro sensor.

  FIG. 6A shows a state where the signal component D2 and the reference signal J are 90 degrees out of phase, that is, there is no phase shift due to a change in the resonance frequency of the vibrating body 102, and therefore no offset voltage is generated. It is a signal waveform diagram in an ideal state. FIG. 6B is a signal waveform diagram in the case where a phase shift due to, for example, a change in the resonance frequency of the vibrating body 102 occurs in the signal D and the phase of the signal component D2 shifts and an offset voltage is generated. FIG. 6C is a signal waveform showing a state in which the phase of the reference signal J is changed by the phase adjusting unit 10 and the signal component D2 and the reference signal J are 90 degrees out of phase and the offset is corrected. FIG.

  Referring to FIG. 6A, first, in a state where the signal component D2 and the reference signal J are 90 degrees out of phase, the second phase detector 51 multiplies the signal component D2 and the reference signal J to obtain a signal. E is generated. Then, as shown in FIG. 6A, the signal E has a signal waveform in which the area on the positive voltage side is equal to the area on the negative voltage side. For this reason, when the signal E is smoothed by the LPF 42 and the angular velocity signal F is generated, the angular velocity signal F is zero in voltage, that is, unnecessary because the vibrator 102 vibrates along the driving vibration direction (X-axis direction). The signal component D2 is removed, and the offset voltage becomes zero.

  However, if the phase of the signal D shifts due to a phase shift due to fluctuations in the resonance frequency of the vibrating body 102 and the phase of the signal component D2 shifts, as shown in FIG. 6B, the signal component D2 and the reference signal J As a result, the area of the positive voltage side is not equal to the area of the negative voltage side. Therefore, when the signal E is smoothed by the LPF 42 and the angular velocity signal F is generated, the angular velocity signal F does not become zero and an offset voltage is generated.

  Next, referring to FIG. 3, in accordance with control signals Ssw1 and Ssw2 output from switch control unit 91, connection terminal T1 and connection terminal T2 of switch SW1 are connected, and connection terminal T4 of switch SW2 is connected. Terminal T5 is connected. Thereby, the angular velocity signal F output from the second synchronous detection circuit 5, that is, the offset voltage is output to the sample hold circuit 92 and is held by the sample hold circuit 92.

  Next, the connection terminal T4 and the connection terminal T6 of the switch SW2 are connected according to the control signal Ssw2 output from the switch control unit 91. As a result, the offset voltage held by the sample hold circuit 92 is supplied to the VCO 93. A signal VCO_Out having a frequency corresponding to the offset voltage is output from the VCO 93 to the phase adjustment unit 10.

  Next, according to the frequency of the signal VCO_Out, the switching frequency of the switches SW1 and SW2 in the switched capacitor circuit 12 changes, and the equivalent resistance of the switched capacitor circuit 12 changes. Then, the phase of the reference signal J is changed by the phase adjusting unit 10 with a change amount corresponding to the frequency of the signal VCO_Out.

  In this case, the phase adjustment unit 10 causes the reference signal J to offset the offset voltage generated based on the shift amount where the phase difference between the signal component D2 and the reference signal J is shifted from 90 degrees. The relationship between the input voltage and the output frequency in the VCO 93 and the capacitances of the capacitors C1 and C2 are set in advance so as to change the phase. Therefore, as shown in FIG. 6C, the phase of the reference signal J is changed by the phase adjustment unit 10 so that the phase difference between the signal component D2 and the reference signal J becomes 90 degrees.

  Next, the signal component D2 whose phase is shifted by 90 degrees by the phase adjustment unit 10 and the reference signal J are multiplied by the second phase detection unit 51 to generate a signal E. Then, as shown in FIG. 6C, the signal E has a signal waveform in which the area on the positive voltage side is equal to the area on the negative voltage side. Therefore, when the signal E is smoothed by the LPF 42 and the angular velocity signal F is generated, the angular velocity signal F is corrected to zero voltage, that is, the offset voltage is zero.

  Further, the phase of the reference signal J is changed by the phase adjustment unit 10 so that the phase difference between the signal component D2 and the reference signal J is 90 degrees. The phase of the reference signal J is adjusted to the same phase.

  Next, when the switch controller 91 detects the voltage value of the angular velocity signal F and detects that the voltage of the angular velocity signal F is zero, that is, the offset voltage is zero, the switch controller 91 switches the switch SW1 to A control signal Ssw1 for connecting the connection terminal T1 and the connection terminal T3 is output, the connection terminal T1 and the connection terminal T3 are connected, and the process proceeds to the normal operation phase.

  Next, returning to FIG. 5, the signal component D <b> 1 obtained by applying acceleration to the gyro sensor 101 and the reference signal J output from the phase adjustment unit 10 are multiplied by the second phase detection unit 51. Thus, the signal E is generated and the signal E is smoothed by the LPF 52, that is, the signal component D1 is synchronously detected based on the reference signal J, and the angular velocity signal F is generated. In this case, since the phase of the signal component D1 and the phase of the reference signal J are adjusted to the same phase by the phase adjustment unit 10, the efficiency of synchronous detection in the second synchronous detection circuit 5 can be improved. The detection sensitivity of the angular velocity signal F can be improved.

  Then, the angular velocity signal F output from the second synchronous detection circuit 5 is output to the amplifier circuit 11 as the angular velocity signal G by the switch SW1, amplified by the amplifier circuit 11, and as the angular velocity detection signal Sout detected by the gyro sensor 101. Output to the outside.

  As a result, the phase difference between the signal component D2 included in the signal D obtained from the vibrating body and the reference signal J serving as a reference for synchronous detection is offset from 90 degrees when no angular velocity is applied to the vibrating body. Even when a voltage is generated, the offset voltage is held by the sample-and-hold circuit 92, the phase of the reference signal J is changed by a change amount corresponding to the offset voltage, and the level of the signal component D2 and the reference signal J is changed. Since the offset voltage can be reduced by setting the phase difference to 90 degrees, it is possible to reduce the offset voltage and improve the detection accuracy of the angular velocity while suppressing a decrease in the detection sensitivity of the angular velocity.

  Note that the switches SW1 and SW2 are switched according to the control signals Ssw1 and Ssw2 from the switch control unit 91, but may be switched by a user operation.

(Second Embodiment)
Next, an angular velocity detection device according to the second embodiment of the present invention will be described. FIG. 7 is a block diagram showing an example of the configuration of the angular velocity detection device 1a according to the second embodiment of the present invention. The angular velocity detection device 1a shown in FIG. 7 is different from the angular velocity detection device 1 shown in FIG. 1 in the following points. That is, the angular velocity detection device 1a shown in FIG. 7 includes an output conversion circuit 9a instead of the output conversion circuit 9, a phase adjustment unit 10a instead of the phase adjustment unit 10, and a binarization unit 14 and an oscillator OSC1. Furthermore, it differs in the point provided.

  The binarization unit 14 is provided between the amplitude control unit 7 and the phase adjustment unit 10a, binarizes the signal I output from the amplitude control unit 7, and outputs the signal I 'to the phase adjustment unit 10a. The binarization unit 14 is configured using, for example, a comparator, compares the reference voltage 0V with the signal I, and outputs the signal I ′ as positive polarity, for example, + 5V, if the signal I is a positive potential, If the signal I is a negative potential, the signal I ′ is output as a negative polarity, for example, −5V. The oscillator OSC1 is an oscillation circuit made of, for example, a crystal oscillator, and outputs a periodic signal CLK to the phase adjustment unit 10a.

  FIG. 8 is a block diagram showing an example of the configuration of the output conversion circuit 9a. The output conversion circuit 9a differs from the output conversion circuit 9 shown in FIG. 3 in that an AD converter 94 and a memory 95 (storage unit) are provided instead of the sample hold circuit 92, the VCO 93, and the switch SW2. As the memory 95, for example, a register circuit, a RAM (Random Access Memory) that is a rewritable storage element, an EEPROM (Electrically Erasable and Programmable Read Only Memory), or the like is used.

  The AD converter 94 is, for example, a 4-bit AD converter, converts the angular velocity signal F output from the second synchronous detection circuit 5 from analog to digital, and stores it in the memory 95 as a digital value. Regardless of the 4-bit AD converter 94, an AD converter having a resolution of the number of bits corresponding to the offset voltage correction accuracy required in the specifications in the angular velocity detection device 1a is used. The memory 95 stores the digital value of the angular velocity signal F and outputs it as a digital signal ADC_Out to the phase adjustment unit 10a.

  FIG. 9 is a circuit diagram showing an example of the configuration of the phase adjustment unit 10a. The phase adjustment unit 10a illustrated in FIG. 9 includes a shift register including flip-flops FF1, FF2, and FF3, and a selector SEL1. The periodic signal CLK output from the oscillator OSC1 is input to the clock input terminals of the flip-flops FF1, FF2, and FF3. Thus, a shift register is configured to shift and delay the signal I ′ in synchronization with the periodic signal CLK output from the oscillator OSC1. FIG. 9 shows an example in which the digital signal ADC_Out is 2 bits for the sake of simplicity.

  The selector SEL1 selects one of the signals output from the flip-flops FF1, FF2, and FF3 according to the digital signal ADC_Out output from the memory 95, and outputs the selected signal as the reference signal J to the second phase detection unit 51. . The selector SEL1 is configured to select the signal I ′ having a larger delay due to the flip-flops FF1, FF2, and FF3 as the value of the digital signal ADC_Out is larger.

  Since other configurations and operations are the same as those of the angular velocity detection device 1 shown in FIG. 1, description thereof is omitted, and characteristic operations of the present embodiment will be described below. FIG. 10 is a signal waveform diagram for explaining the operation of the angular velocity detection device 1a. In the signal waveform diagram shown in FIG. 10, the level of an unnecessary signal component D2 generated when the vibrating body 102 vibrates along the driving vibration direction (X-axis direction) and the signal I generated from the driving voltage Vd1. The phase difference is not 90 degrees, for example 45 degrees. For this reason, an offset voltage is generated in the angular velocity signal F output from the second synchronous detection circuit 5 in the initial state.

  Next, in response to the control signal Ssw1 from the switch control unit 91, the connection terminal T1 and the connection terminal T2 in the switch SW1 are connected, and the angular velocity signal F, that is, the offset voltage is converted into a digital value by the AD converter 94, and the memory 95. Then, the digital signal ADC_Out obtained by converting the offset voltage into a digital value is output from the memory 95 to the phase adjustment unit 10a. FIG. 10 shows an example in which the digital signal ADC_Out is a 3-bit signal and the offset voltage is “010”.

  On the other hand, the signal I output from the amplitude control unit 7 is binarized by the binarization unit 14 to be a signal I ′. Then, in the phase adjustment unit 10a, the signal I ′ is directly input to the selector SEL1 and the flip-flop FF1 as the signal I (0), and is delayed by one clock in the periodic signal CLK by the flip-flop FF1 as the signal I (1). The signal is output to the selector SEL1 and the flip-flop FF2, further delayed by one clock in the periodic signal CLK by the flip-flop FF2, and output to the selector SEL1 and the flip-flop FF3 as the signal I (2). Delayed by one clock in CLK and output to the selector SEL1 as a signal I (3).

  As a result, the selector SEL1 receives the signal I (0) which is the signal I ′ as it is, the signal I (1) obtained by delaying the signal I ′ by one clock in the periodic signal CLK, and the signal I ′ as the periodic signal. A signal I (2) delayed by two clocks in CLK and a signal I (3) obtained by delaying signal I ′ by three clocks in periodic signal CLK are input.

  The selector SEL1 receives the digital signal ADC_Out output from the memory 95 as a selection signal. For example, if the digital signal ADC_Out is 2 bits and “10”, the selector SEL1 selects the signal I (2) and outputs it as the reference signal J to the second phase detector 51.

  Then, the reference signal J is delayed by two clocks in the periodic signal CLK in accordance with the digital signal ADC_Out indicating the offset voltage, and the phase difference between the signal component D2 and the reference signal J is 90 degrees, so that the second synchronous detection is performed. In the circuit 5, the angular velocity signal F is zeroed, that is, the offset voltage is corrected to zero. In this case, the phase adjustment unit 10a changes the phase of the reference signal J so that the phase difference between the signal component D2 and the reference signal J is 90 degrees, and thus the phase of the signal component D1 indicating Coriolis force The phase of the reference signal J is adjusted to the same phase.

  In this case, the phase adjustment unit 10a cancels the reference signal J with respect to the offset voltage generated based on the shift amount where the phase difference between the signal component D2 and the reference signal J is shifted from 90 degrees. The frequency of the periodic signal CLK and the signal selected by the selector SEL1 according to the digital signal ADC_Out are set in advance so as to change the phase.

  Next, when the switch controller 91 detects the voltage value of the angular velocity signal F and detects that the voltage of the angular velocity signal F is zero, that is, the offset voltage is zero, the switch controller 91 switches the switch SW1 to A control signal Ssw1 for connecting the connection terminal T1 and the connection terminal T3 is output, the connection terminal T1 and the connection terminal T3 are connected, and the process proceeds to the normal operation phase.

  Other operations are the same as those of the angular velocity detection device 1 shown in FIG. As a result, the phase difference between the signal component D2 included in the signal D obtained from the vibrating body and the reference signal J serving as a reference for synchronous detection is offset from 90 degrees when no angular velocity is applied to the vibrating body. Even when a voltage is generated, the offset voltage is stored in the memory 95, and the phase of the reference signal J is changed by a change amount corresponding to the offset voltage, so that the phase difference between the signal component D2 and the reference signal J is obtained. Since the offset voltage can be reduced by setting the angle to 90 degrees, it is possible to reduce the offset voltage while suppressing the decrease in the angular velocity detection sensitivity due to the phase shift of the reference signal, and to improve the angular velocity detection accuracy.

It is a block diagram which shows an example of a structure of the angular velocity detection apparatus which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the equivalent circuit of the gyro sensor shown in FIG. FIG. 2 is a block diagram illustrating an example of a configuration of an output conversion circuit illustrated in FIG. 1. It is a circuit diagram which shows an example of a structure of the phase adjustment part shown in FIG. It is a signal waveform diagram for demonstrating operation | movement of the angular velocity detection apparatus shown in FIG. FIG. 6 is a signal waveform diagram for explaining the operation of the second synchronous detection circuit shown in FIG. 1. It is a block diagram which shows an example of a structure of the angular velocity detection apparatus which concerns on the 2nd Embodiment of this invention. FIG. 8 is a block diagram illustrating an example of a configuration of an output conversion circuit illustrated in FIG. 7. It is a circuit diagram which shows an example of a structure of the phase adjustment part shown in FIG. It is a signal waveform diagram for demonstrating operation | movement of the angular velocity detection apparatus shown in FIG. It is a conceptual diagram for demonstrating the structure of the angular velocity detection apparatus which concerns on background art. It is explanatory drawing for demonstrating operation | movement of a gyro sensor. It is explanatory drawing for demonstrating the principle of operation of the angular velocity detection apparatus using a gyro sensor. It is explanatory drawing for demonstrating the principle of operation of the angular velocity detection apparatus using a gyro sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Angular velocity detection apparatus 3 Sensor IF circuit 4 1st synchronous detection circuit 5 2nd synchronous detection circuit 6 Vibration control circuit 7 Amplitude control part 9, 9a Output conversion circuit 10, 10a Phase adjustment part 12 Switched capacitor circuit 14 Binary-ization Unit 41 First phase detection unit 42, 52 LPF
51 Second phase detection unit 91 Switch control unit 92 Sample hold circuit 94 AD converter 95 Memory 101 Gyro sensor 102 Vibrating body 103, 104 Driving electrode 105, 106 Detection electrode C1, C2 Capacitors C103, C104, C105, C106 Electrostatic Capacitance F Angular velocity signal FF1, FF2, FF3 Flip-flop SEL1 selector

Claims (3)

A vibration control unit that generates a drive signal for vibrating the vibrating body at a constant frequency;
A drive unit that vibrates the vibrating body based on the drive signal generated by the vibration control unit;
Detecting a Coriolis force generated by applying an angular velocity to the vibrating body, and outputting a detection signal indicating the detected Coriolis force;
A synchronous detection unit that generates an angular velocity signal indicating an angular velocity applied to the vibrating body from a detection signal output from the detection unit by performing synchronous detection based on a reference signal indicating the vibration timing of the vibrating body;
A storage unit for storing initial value information based on an angular velocity signal generated by the synchronous detection unit in a state where no angular velocity is applied to the vibrating body;
According to the initial value information stored by the storage unit, the reference signal is generated by changing the phase of the drive signal generated by the vibration control unit so as to reduce the level of the angular velocity signal, and the synchronization is performed. An angular velocity detection device comprising: a phase adjustment unit that outputs to a detection unit. The angular velocity detection device according to claim 1, wherein the phase adjustment unit changes the phase of the drive signal using a switched capacitor circuit to generate the reference signal. The angular velocity detection device according to claim 1, wherein the phase adjustment unit generates a reference signal by changing a phase of the drive signal using a shift register.

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