JP2004212111A - Angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a variation between a resonance frequency at the drive-electrode side of a vibrator and that at a detection-electrode side by a relatively, simple circuit configuration. <P>SOLUTION: When angular velocity is added to the vibrator 30 vibrating in a specific direction by a drive circuit 40, Coriolis force operates; vibration in a direction orthogonally crossing the vibration in the specific direction is generated; and charge generated by the vibration is detected in detection electrodes 32a, 32b. The detected charge is converted to voltage by an angular velocity detection circuit 60 for outputting an angular velocity detection signal S64. In the signal S64, a phase is delayed by 90° by a phase shift circuit 71 and an output signal S71 is outputted. In a synchronous detection circuit 72, the signal S71 is synchronized and detected for outputting a detection signal S72, based on an output voltage S41 in an I/V conversion circuit 41. The signal S72 is smoothed at a smoothing section 82 for outputting a DC detection signal Sout corresponding to the angular velocity. The phase of input or output at the smoothing section 82 is adjusted by a phase adjustment means 81. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention improves the angular velocity detection accuracy by reducing variations in frequency response due to manufacturing errors and the like in, for example, a vibration type angular velocity sensor configured by using a piezoelectric vibrator such as a crystal resonator or a silicon vibrator. The present invention relates to an angular velocity sensor that is operated.
[0002]
[Prior art]
Conventionally, as a technique relating to this kind of angular velocity sensor, for example, there is a technique described in the following document.
[0003]
[Patent Document 1]
Japanese Patent No. 2781161
[Patent Document 2]
JP-A-11-44540
[Patent Document 3]
JP-A-2001-82964
[Patent Document 4]
JP-A-10-59556
[0004]
FIG. 2 is a schematic configuration diagram of a conventional angular velocity sensor described in Patent Documents 1 and 2 and the like, and FIG. 3 is an operation waveform diagram of FIG.
[0005]
When a piezoelectric vibrator (for example, a tuning-fork type crystal vibrator) is used as the vibrator 1 of the angular velocity sensor, a positive drive electrode 2a for excitation, a negative drive electrode 2b, And a + side detection electrode 3a for detecting Coriolis force, a-side detection electrode 3b, and the like. The drive circuit 10 including an oscillation circuit that supplies a drive signal Sd of an alternating current (hereinafter, referred to as “AC”) voltage for exciting the vibrator 1 is connected to the + drive electrode 2 a and the − drive electrode 2 b. . Further, a Coriolis force detection circuit 20 that outputs a detection signal Sout of a direct current (hereinafter referred to as “DC”) voltage proportional to the angular velocity ω applied to the vibrator 1 is connected to the + side detection electrode 3 a and the − side detection electrode 3 b. Is done.
[0006]
The vibrator 1 has a mass m, and when the drive signal Sd is applied from the drive circuit 10 to the negative drive electrode 2b, the vibrator 1 vibrates at a predetermined frequency in the B direction along the X axis. When an angular velocity ω is applied around the Y axis, a Coriolis force F (= 2 mvω, where v is the vibration velocity of the vibrator 1) is generated in the Z axis direction orthogonal to the X axis. Since the Coriolis force F is determined in proportion to the magnitude of the angular velocity ω, the Coriolis force F is detected as the amount of distortion displacement of the vibrator 1 by the + side detection electrode 3a, the − side detection electrode 3b and the Coriolis force detection circuit 20. Thus, the magnitude of the angular velocity ω of the vibrator 1 can be obtained.
[0007]
That is, in the drive circuit 10, the output current of the + drive electrode 2a is converted into a voltage by the current / voltage (hereinafter, referred to as "I / V") conversion circuit 11, and this voltage is converted into an automatic gain control (hereinafter, "AGC"). The drive signal Sd is supplied to the negative drive electrode 2b through a buffer amplifier (not shown) (hereinafter, this “amplifier” is referred to as an “amplifier”) or the like, and the vibrator 1 vibrates. I do.
[0008]
When an angular velocity? Is output. This output current is converted into a voltage by an I / V conversion circuit 21 in the Coriolis force detection circuit 20 to generate an angular velocity detection signal S21. The angular velocity detection signal S21 is sent to the phase shift circuit 22.
[0009]
The phase shift circuit 22 includes, for example, a resistor and a capacitor. The angular velocity detection signal S21 output from the I / V conversion circuit 21 has a phase delayed by 90 ° from the drive signal Sd due to the characteristics of the vibrator 1. Therefore, in order to synchronize with the drive signal Sd, the phase of the angular velocity detection signal S21 is delayed by 90 ° by the phase shift circuit 22 composed of a resistor and a capacitor, and the angular velocity detection signal S22 with this phase delay is sent to the synchronous detection circuit 23.
[0010]
In the synchronous detection circuit 23, the direction to which the angular velocity ω is added (that is, the rotational direction, the waveform of the angular velocity detection signal S21 in FIG. 3 indicates clockwise rotation, and when the phase of this waveform is shifted by 180 °, the clock rotates to the left). In order to know this, based on the output voltage of the I / V conversion circuit 11, a phase-delayed angular velocity detection signal S22 output from the phase shift circuit 22 is synchronously detected, and a detection signal S23 having the same polarity as shown in FIG. Is output. The detection signal S23 has a high-frequency component removed by a low-pass filter (hereinafter referred to as "LPF") 24, and a DC detection signal Sout proportional to the angular velocity ω applied to the vibrator 1 is output.
[0011]
Applications of such an angular velocity sensor include, for example, mounting it on a vehicle, an aircraft, or the like, recording the running or flight trajectory, and detecting a yaw rate generated at the time of turning. An angular velocity sensor is mounted on a robot and applied to such attitude control. Recently, it is also used for detecting a vehicle position in a very common car navigation or the like, or detecting a camera shake of a video camera or the like.
[0012]
[Problems to be solved by the invention]
However, conventional angular velocity sensors as described in Patent Documents 1 and 2 have the following problems.
[0013]
In the angular velocity sensor, the frequency response of the phase of the vibrator 1 depends on the frequency difference ΔF = Fs−Fd between the resonance frequency Fd of the drive electrodes 31a and 31ba and the resonance frequency Fs of the detection electrodes 32a and 32b. Further, the frequency difference ΔF is governed by the processing accuracy of the outer shape of the vibrator 1, and high processing accuracy is required. Conventionally, the frequency difference ΔF has been adjusted by cutting the outer shape of the vibrator 1 by laser trimming, sandblasting, or the like, but it has been difficult to suppress this variation.
[0014]
The vibrator signals output from the detection electrodes 3a and 3b of the vibrator 1 are minute currents and are easily affected by a change in ambient temperature, a change in power supply voltage, and the like. If there is a variation, there arises a problem that the accuracy of the DC detection signal Sout decreases.
[0015]
According to the technique of Patent Document 4, in order to correct a surface shake or a camera shake of a video camera or the like (this frequency range is about 0.5 Hz to 30 Hz), an angular velocity sensor detects an angular speed signal at the time of the surface shake or the camera shake and performs correction. Correction control of the lens angle is performed by the servo. However, if the frequency difference ΔF has a variation as described above, there arises a problem that a signal for correcting a surface shake or a camera shake shifts and a correction direction or the like malfunctions.
[0016]
Further, in the angular velocity sensor described in Patent Document 3, a planar vibrator (ie, a silicon vibrator) formed on a silicon substrate is used as a vibrator, and an AC voltage is applied to apply electrostatic voltage between electrodes on the silicon substrate. Is generated, and the planar vibrator is vibrated by the electrostatic force. When an angular velocity is applied to the vibrating plane vibrator, a Coriolis force is generated in a direction orthogonal to the vibration direction, and the plane vibrator vibrates in the direction of the Coriolis force. The signal is detected to detect the magnitude of the angular velocity. The above-described problem also occurs in the angular velocity sensor using such a silicon vibrator or other angular velocity sensors.
[0017]
An object of the present invention is to solve the problems of the prior art and to provide an angular velocity sensor capable of correcting variations in the frequency difference ΔF with a relatively simple circuit configuration.
[0018]
[Means for Solving the Problems]
In order to solve the above problems, in the angular velocity sensor according to the present invention, a drive circuit that outputs an AC drive signal, and an oscillator signal that is excited by the drive signal and changes in amplitude according to the magnitude and direction of the angular velocity are output. A vibrator, an angular velocity detection circuit that converts the vibrator signal into an angular velocity detection signal, a synchronous detection circuit that synchronously detects the angular velocity detection signal based on the drive signal and outputs a detection signal of the same polarity, A smoothing circuit for smoothing a signal and outputting a DC detection signal corresponding to the angular velocity; a smoothing circuit connected to an input side or an output side of the smoothing circuit; a first resonance frequency of the drive circuit side and a first resonance frequency of the angular velocity detection circuit side; Phase adjusting means for adjusting the phase of the detection signal or the DC detection signal so as to cancel the frequency difference from the second resonance frequency.
[0019]
Here, for example, the phase adjusting means is configured by an LPF including a resistor and a capacitor. Alternatively, the phase adjusting means is constituted by an LPF comprising a resistor and a capacitor, and the resistor is constituted by a variable resistor or the capacitor is constituted by a variable capacitor. Further, the synchronous detection circuit is configured by a circuit that generates the detection signal by multiplying the driving signal by the angular velocity detection signal.
[0020]
In the present invention, by adopting such a configuration, the vibrator vibrates when a drive signal is output from the drive circuit. When the vibrator is vibrating in a specific direction at a predetermined frequency according to a drive signal of a drive circuit, when an angular velocity is applied to the vibrator, Coriolis proportional to the magnitude of the angular velocity in a direction orthogonal to the vibration direction. A force is generated, and an oscillator signal is output from the oscillator. The transducer signal is converted into an angular velocity detection signal by the angular velocity detection circuit and sent to the synchronous detection circuit.
[0021]
The synchronous detection circuit synchronously detects the angular velocity detection signal based on the drive signal and outputs a detection signal having the same polarity. This detection signal is smoothed by a smoothing circuit, and a DC detection signal corresponding to the angular velocity is output. The phase of the detection signal on the input side or the DC detection signal on the output side of the smoothing circuit is adjusted by the phase adjustment means, and the frequency difference between the first resonance frequency on the drive circuit side and the second resonance frequency on the angular velocity detection circuit side is obtained. Is suppressed.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
1A to 1E are configuration diagrams of a main part of an angular velocity sensor according to a first embodiment of the present invention. FIG. 1A is an overall circuit diagram, and FIG. FIG. 9C is a circuit diagram of the smoothing circuit 80, FIG. 9D is a circuit diagram of the smoothing unit 82, and FIG. 9E is a circuit diagram of another configuration of the smoothing unit 82. It is.
[0023]
The angular velocity sensor shown in FIG. 1A is based on, for example, the same principle as that of FIG. 2 and includes a vibrator (for example, a piezoelectric vibrator such as a tuning-fork type crystal vibrator) 30. At a predetermined position of the vibrator 30, a positive drive electrode 31a and a negative drive electrode 31b for exciting the vibrator 30, and a charge corresponding to (for example, proportional to) the angular velocity applied to the vibrator 30 are detected. A positive side detection electrode 32a and a negative side detection electrode 32b for outputting a vibrator signal are provided.
[0024]
The + drive electrode 31a and the − drive electrode 31b are driven by an oscillation circuit for supplying an AC voltage drive signal Sd for exciting the vibration of the vibrator 30 in a specific direction to the − drive electrode 31b. The circuit 40 is connected. The positive detection electrode 32a and the negative detection electrode 32b are connected to a Coriolis force detection circuit 50 that outputs a detection signal Sout of a DC voltage proportional to the angular velocity ω applied to the vibrator 30.
[0025]
The drive circuit 40 has an I / V conversion circuit 41 connected to the + drive electrode 31a. The I / V conversion circuit 41 is a circuit that converts an output current of the + drive electrode 31a into a voltage and outputs an output voltage S41, and is configured by a current amplifier or the like. Although not shown, the output terminal of the I / V conversion circuit 41 has an LPF for removing a high-frequency component of the output voltage S41, and increases the gain when the vibrator 30 is in a start-up period. In the case of (1), the AGC circuit 42 is connected via a startup compensation circuit or the like for reducing the gain. The AGC circuit 42 is a circuit that receives an output voltage S41 sent via an LPF, a start-up compensation circuit, and the like (not shown), and controls the gain based on the control voltage S45. It is connected to the negative drive electrode 31b via a buffer amplifier or the like.
[0026]
The Coriolis force detection circuit 50 connected to the + side detection electrode 32a and the − side detection electrode 32b has an angular velocity detection circuit 60 connected to the + side detection electrode 32a and the − side detection electrode 32b. The angular velocity detection circuit 60 is a circuit that inputs a vibrator signal (that is, electric charge) output from the detection electrodes 32a and 32b due to the vibration of the vibrator 30 and converts the signal into an angular velocity detection signal S64. , A synchronous detection circuit 72 is connected via a phase shift circuit 71. The phase of the angular velocity detection signal S64 is delayed by 90 ° from the output voltage S41 of the I / V conversion circuit 41 due to the characteristics of the vibrator 30. Therefore, in order to synchronize with the output voltage S41, a phase shift circuit 71 is provided to delay the phase of the angular velocity detection signal S64 by 90 °.
[0027]
The phase shift circuit 71 is composed of, for example, an LPF as shown in FIG. 1B, and is connected to an input node 71 a connected to the output side of the angular velocity detection circuit 60 and to the input side of the synchronous detection circuit 72. And an output node 71d. A resistor 71b is connected between the input node 71a and the output node 71d, and the output node 71d is connected to a ground potential node (hereinafter, referred to as "GND") via a capacitor 71c.
[0028]
The synchronous detection circuit 72 synchronizes the output signal S71 of the phase shift circuit 71 based on the output voltage S41 of the I / V conversion circuit 41 to know the direction (rotation direction) of the vibrator 30 to which the angular velocity ω is applied. This is a circuit for detecting and outputting a detection signal S72 of the same polarity, and is configured by a multiplication circuit and the like. The smoothing circuit 80 is connected to the output terminal of the synchronous detection circuit 72. The smoothing circuit 80 is a circuit that smoothes the detection signal S72 and outputs a DC detection signal Sout72 corresponding to the angular velocity ω applied to the vibrator 30. For example, as shown in FIG. 81 and a smoothing section 82.
[0029]
The phase adjusting means 81 adjusts the phase of the detection signal S72 so as to cancel the phase difference ΔF between the first resonance frequency Fd on the drive electrodes 31a and 31b and the second resonance frequency Fs on the detection electrodes 32a and 32b. (For example, after a delay), and outputs the adjusted detection signal S81. The circuit includes, for example, an LPF including a resistor 81b and a capacitor 81c. One end of a resistor 81b is connected to an input node 81a connected to an output node 71d of the phase shift circuit 71. The other end of the resistor 81 is connected to GND via a capacitor 81c. Is connected to the input side of the smoothing unit 82 via
[0030]
The smoothing unit 82 is a circuit that smoothes the adjusted detection signal S81 and outputs a DC detection signal Dout, and is configured by, for example, a circuit as illustrated in FIG. 1D or 1E. In the smoothing unit 82 shown in FIG. 1D, an input node 82a connected to an output node 81d of the phase adjustment unit 81, an input node 82b connected to GND, and an output node 82e outputting a DC detection signal Dout. , GND connected to the output node 82f. The input node 82a is connected to the anode of a diode 82c, and the cathode of the diode 82c is connected to the output node 82e and to the nodes 82b and 82f via the capacitor 82d. In the smoothing unit 82, when the adjusted detection signal S81 is input from the node 82a, the charge of the detection signal S81 is accumulated in the capacitor 82d through the diode 82c, and the accumulated charge of the capacitor 82d is discharged to the node 82e. Thereby, the detection signal S81 is smoothed.
[0031]
In the smoothing unit 82 shown in FIG. 1E, the input node 82a is connected to the input node 82a via the capacitor 82g, and the output node 82e is connected to the input node 82a via the choke coil 82h. Output node 82e is connected to output node 82f via capacitor 82i. In the smoothing unit 82, when the adjusted detection signal S81 is input from the input node 82a, the AC component of the detection signal S81 flows to the input node 82b through the capacitor 82g, and the DC component of the detection signal S81 passes through the choke coil 82h. It flows to the output node 82e. The remaining AC component that has passed through the choke coil 82h flows to the capacitor 82i side. Thereby, the detection signal S81 is smoothed.
[0032]
4A and 4B are operation waveform diagrams of FIG. 1, wherein FIG. 4A is a waveform diagram of the angular velocity ω (t), and FIG. 4B is a frequency response waveform diagram of the detection signal S72. It is.
[0033]
Hereinafter, the operation (A) of the drive circuit 40 and the operation (B) of the Coriolis force detection circuit 50 in the angular velocity sensor of FIG. 1 will be described with reference to the operation waveform diagrams of FIGS. 4 (a) and 4 (b). .
[0034]
(A) Operation of drive circuit 40
When the power supply voltage is applied, the AC drive signal Sd output from the AGC circuit 42 is given to the negative drive electrode 31b of the vibrator 30, and the vibrator 30 starts to vibrate. When the vibrator 30 starts oscillating, the output current of the + drive electrode 31a is converted into a voltage by the I / V conversion circuit 41, and the output voltage S41 is output. The gain of the output voltage S41 is controlled by an AGC circuit 42 by a control voltage S45 through an LPF and a start-up compensation circuit (not shown), and the AC drive signal Sd is supplied to the negative side drive of the vibrator 30 through a buffer amplifier and the like (not shown). It is supplied to the electrode 31b. In a stable period after the vibrator 30 starts to vibrate, the vibrator 30 vibrates in a specific direction at a constant frequency by an AC drive signal Sd output from the AGC circuit 42 via a buffer amplifier (not shown) or the like.
[0035]
When the vibrator 30 continues to vibrate in a specific direction at a constant frequency by the AC drive signal Sd, the output voltage S41 of the I / V conversion circuit 41 is supplied to the synchronous detection circuit 72 via a buffer amplifier or the like (not shown).
[0036]
(B) Operation of Coriolis force detection circuit 50
When an angular velocity ω is applied to the vibrator 30 vibrating in a specific direction at a constant frequency, a Coriolis force F acts on the vibrator 30, and the vibrator 30 is vibrated in a direction orthogonal to the vibration direction of the specific direction. Vibration is generated, and charges generated in the vibrator 30 due to the vibration are detected by the detection electrodes 32a and 32b, and the detected vibrator signal (current) is output from the detection electrodes 32a and 32b. This output current is converted into a voltage by the angular velocity detection circuit 60, and an angular velocity detection signal S64 is output and sent to the phase shift circuit 71.
[0037]
The phase shift circuit 71 delays the phase of the angular velocity detection signal S64 by 90 ° and sends the output signal S71 to the synchronous detection circuit 72. The synchronous detection circuit 72 multiplies the output voltage S41 of the I / V conversion circuit 41 by the output signal S71 of the phase shift circuit 71, for example, in order to know the direction (rotation direction) to which the angular velocity ω is added. The output signal S71 is synchronously detected to output a detection signal S72 having the same polarity.
[0038]
Here, the angular velocity ω applied to the vibrator 30 is not constant and varies with time t when there is a surface shake or a hand shake. For example, as shown in FIG. 4A, when the angular velocity ω changes sinusoidally due to a surface shake or a camera shake, the angular velocity ω is expressed by the following equation (1).
ω (t) = ω_max・ Sin 2πf_ωt (1)
Where ω_max  ; Maximum angular velocity
f_ω    ; Shake frequency
[0039]
On the other hand, if the frequency difference ΔF between the resonance frequency Fd of the drive electrodes 31a and 31b and the resonance frequency Fs of the detection electrodes 32a and 32b varies due to a manufacturing error or the like, the phase of the angular velocity ω (t) is shifted, as shown in FIG. ). The frequency characteristic of the phase θ in the detection signal S72 output from the synchronous detection circuit 72 is, as shown in FIG._ωIs, for example, 50 Hz, the phase θ greatly varies around (−7 °) (θ ± α °), and the detection accuracy of the Coriolis force detection circuit 50 decreases.
[0040]
Thus, in the present embodiment, the phase adjustment is performed by the phase adjusting means 81 in order to suppress the variation ± α ° of the phase θ within a predetermined range (for example, ± 3 °). In this phase adjusting means 81, an LPF composed of a resistor 81b having a resistance value R and a capacitor 81c having a capacitance value C provides a cutoff frequency f_oThe high frequency component of the detection signal S72 is cut off to suppress the variation ± α ° to, for example, ± 3 °.
[0041]
That is, when the phase adjustment is performed by the LPF including the RC, the phase θ is represented by the following equation (2).
θ = tan^-1 (f_ω/ F_o) (2)
here,
f_o = 1 / (2πRC) (3)
Also, in order to perform only phase adjustment with the LPF and not affect the amplitude (ie, sensitivity), the cutoff frequency f_oIs preferably selected under the condition of the following equation (4).
f_o  > 10 × f (4)
[0042]
F in the equation (4) is a frequency value set in a standard in consideration of surface shake, hand shake, and the like. Therefore, if the high frequency component of the detection signal S72 is cut off by the phase adjusting unit 81 in which the resistance value R and the capacitance value C are set to predetermined values based on the expressions (2) to (4), the phase adjusting unit 81 The variation ± α ° of the phase θ of the adjusted detection signal S81 output from the controller can be suppressed to, for example, ± 3 °.
[0043]
The adjusted detection signal S81 is smoothed by the smoothing unit 82, and a DC detection signal Sout proportional to the angular velocity ω is output. In order to further improve the accuracy of the DC detection signal Sout, the sensitivity, the zero-point voltage, the temperature change, and the like may be corrected by a circuit (not shown).
[0044]
As described above, the first embodiment has the following effects (i) and (ii).
[0045]
(I) Even if the frequency difference ΔF between the resonance frequency Fd of the drive electrodes 31a and 31b and the resonance frequency Fs of the detection electrodes 32a and 32b varies due to a manufacturing error or the like, the detection output from the synchronous detection circuit 72 is performed. Since the phase adjustment unit 81 cuts off the high-frequency component of the signal S72 and adjusts the phase, the variation ± α ° of the phase θ of the detection signal S72 is suppressed within a predetermined range (eg, ± 3 °). . As a result, the detection accuracy of the DC detection signal Sout output from the smoothing unit 82 can be improved.
[0046]
(Ii) Since the phase adjusting means 81 is composed of an RC LPF, the setting of the resistance value R of the resistor 81b and the capacitance value C of the capacitor 81c makes it possible to easily make the variation ± α ° of the phase θ of the detection signal S72 within a predetermined range. Can be suppressed.
[0047]
(Second embodiment)
FIG. 5 is a configuration diagram of an angular velocity sensor according to the second embodiment of the present invention, and the same reference numerals are given to the same components as those in FIG. 1 illustrating the first embodiment.
[0048]
In the angular velocity sensor, in the angular velocity sensor drive circuit 40 of FIG. 1, the I / V conversion circuit 41 is configured by a current amplifier, and a circuit for generating a control voltage S45 to be applied to the AGC circuit 42 is provided. . Further, in the Coriolis force detection circuit 50 of FIG. 1, the angular velocity detection circuit 60 includes I / V conversion circuits 61 and 62, a differential amplifier 63 and an inverting amplifier 64. Other configurations are the same as those in FIG.
[0049]
That is, in the drive circuit 40 of FIG. 5, the I / V conversion circuit 41 connected to the + drive electrode 31a of the vibrator 30 includes an operational amplifier (hereinafter, referred to as “op-amp”) 41a, a feedback resistor 41b, and a feedback capacitor. 41c. The positive input terminal of the operational amplifier 41a is connected to the fixed potential node AG, and the negative input terminal is connected to the positive drive electrode 31a. A feedback resistor 41b and a feedback capacitor 41c are connected in parallel between the negative input terminal and the output terminal of the operational amplifier 41a. A rectifier circuit 43 is connected to an output terminal of the operational amplifier 41a via a buffer amplifier or the like (not shown), and a reference power supply circuit 44 is provided.
[0050]
The rectifier circuit 43 is a circuit that rectifies the output voltage S41 provided via a buffer amplifier or the like (not shown) and outputs a DC voltage S43 (or a DC current). The reference power supply circuit 44 generates a constant voltage with respect to a change in power supply voltage, temperature change, and the like, and based on the constant voltage, a reference voltage S44 (or a reference current ), And a comparison circuit 45 is connected to this output terminal and the output terminal of the rectifier circuit 43. The comparison circuit 45 compares the DC voltage S43 (or DC current) with the reference voltage S44 (or reference current), integrates the voltage difference (or current difference), and outputs a control voltage S45. The output terminal is connected to the control terminal of the AGC circuit 42.
[0051]
In the Coriolis force detection circuit 50 of FIG. 5, the angular velocity detection circuit 60 includes an I / V conversion circuit 61 connected to the + side detection electrode 32a and an I / V conversion circuit 62 connected to the − side detection electrode 32b. The differential amplifier 63 and the inverting amplifier 64 are connected to these output terminals. The I / V conversion circuits 61 and 62 are circuits for converting vibrator signals (currents) having opposite phases to the detection electrodes 32a and 32b when the acceleration ω is applied to the vibrator 30, so that the signals are converted into voltages. Like the I / V conversion circuit 41, the I / V conversion circuit 61 includes a current amplifier including an operational amplifier 61a, a feedback resistor 61b, and a feedback capacitor 41c. Similarly, the I / V conversion circuit 62 also includes a current amplifier including an operational amplifier 62a, a feedback resistor 62b, and a feedback capacitor 62c.
[0052]
The differential amplifier 63 is a circuit that amplifies the difference between the output voltages of the two I / V conversion circuits 61 and 62, and has a function of canceling an in-phase signal such as crosstalk due to the AC drive signal Sd of the drive circuit 40. Have. The differential amplifier 63 has an input resistor 63a connected to the output terminal of the I / V conversion circuit 61, and an input resistor 63b connected to the output terminal of the I / V conversion circuit 62. Is connected to the fixed potential node AG via the resistor 63c and to the + input terminal of the operational amplifier 63d. The output side of the input resistor 63b is connected to the negative input terminal of the operational amplifier 63d, and is connected to the output terminal of the operational amplifier 63d via a feedback resistor 63e.
[0053]
The inverting amplifier 64 connected to the output terminal of the differential amplifier 63 is a circuit that inverts and amplifies the output signal of the differential amplifier 63 and outputs the angular velocity detection signal S64 to the phase shift circuit 71. The inverting amplifier 64 is connected to the output terminal of the operational amplifier 63d. It has an input resistor 64a connected. The output side of the input resistor 64a is connected to the negative input terminal of the operational amplifier 64b, and is connected to the output terminal of the operational amplifier 64b via the feedback resistor 64c. The + input terminal of the operational amplifier 64b is connected to the fixed potential node AG.
[0054]
Next, the operation of the angular velocity sensor of FIG. 5 will be described.
[0055]
The vibrator 30 starts oscillating by applying the power supply voltage. The current output from the + drive electrode 31a of the vibrator 30 is converted into a voltage by the I / V conversion circuit 41, and the output voltage S41 is output. This output voltage S41 is converted into a DC voltage S43 (or DC current) by a rectifier circuit 43 via a buffer amplifier or the like (not shown) and sent to a comparison circuit 45. The comparison circuit 45 compares the reference voltage S44 (or the reference current) output from the reference power supply circuit 44 with the DC voltage S43 (or the DC current) output from the rectification circuit 43, and outputs the control voltage S45 to the AGC circuit 42. Output to The gain of the output voltage S41 of the I / V conversion circuit 41 is controlled by the AGC circuit 42 via an LPF (not shown), a start-up compensation circuit, and the like. The AGC circuit 42 supplies an AC drive signal Sd to the negative drive electrode 31b via a buffer amplifier or the like (not shown), and the vibrator 30 vibrates in a specific direction at a constant frequency.
[0056]
When an angular velocity ω is applied to the vibrator 30 vibrating in a specific direction at a constant frequency, a Coriolis force F acts on the vibrator 30, and the vibrator 30 vibrates in a direction orthogonal to the vibrating direction of the specific direction. Is born. Electric charges generated in the vibrator 30 due to the vibration are detected by the detection electrodes 32a and 32b, and the detected vibrator signal (current) is output from the detection electrodes 32a and 32b. This output current is converted into a voltage by I / V conversion circuits 61 and 62 in the angular velocity detection circuit 60, and output voltages of these I / V conversion circuits 61 and 62 are differentially amplified by a differential amplifier 62. The output voltage of the differential amplifier 63 is inverted and amplified by the inverting amplifier 64, and the angular velocity detection signal S64 is output.
[0057]
When the vibrator 30 vibrates in a specific direction at a constant frequency by the AC drive signal Sd, the output voltage S41 is supplied to the synchronous detection circuit 72 via a buffer amplifier (not shown) or the like. On the other hand, the angular velocity detection signal S64 output from the inverting amplifier 64 has a phase delayed by 90 ° in the phase shift circuit 71, and the output signal S71 is sent to the synchronous detection circuit 72. In the synchronous detection circuit 72, similarly to the first embodiment, based on the output voltage S41 supplied from the I / F conversion circuit 41, the output signal S71 of the phase shift circuit 71 is synchronously detected and a detection signal S72 of the same polarity is detected. Output.
[0058]
As in the first embodiment, the phase of the detection signal S72 is adjusted by cutting off the high-frequency component by the phase adjustment unit 81, and is smoothed by the smoothing unit 82, and the DC detection signal Sout corresponding to the angular velocity ω is output. .
[0059]
As described above, in the second embodiment, in addition to the effects of the first embodiment, the following effects (a) and (b) are also obtained.
[0060]
(A) Since a constant reference voltage S44 (or reference current) is generated by the reference power supply circuit 44 and compared with the DC voltage S43 (or DC current) by the comparison circuit 45, the control voltage S45 is generated. The AGC circuit 42 operates so that the oscillator current Ix input to the I / V conversion circuit 41 becomes constant even when the power supply voltage, the ambient temperature, and the like change. Since the vibrator current Ix and the vibration speed are proportional, maintaining the vibrator current Ix constant is the key to a high-precision angular velocity sensor circuit. The Coriolis force F can accurately detect the angular velocity ω by keeping the transducer current Ix constant. Thereby, the detection accuracy of the DC detection signal Sout can be improved.
[0061]
(B) The angular velocity detection circuit 60 differentially amplifies the outputs of the two I / V conversion circuits 61 and 62 with a differential amplifier 63, inverts and amplifies this with an inversion amplifier 64, and outputs an angular velocity detection signal S64. Therefore, detection accuracy and stability are good.
[0062]
(Third embodiment)
FIGS. 6A to 6C are circuit diagrams of the phase adjusting means according to the third embodiment of the present invention. Elements common to those in FIG. 1C are denoted by the same reference numerals. ing.
[0063]
This phase adjusting means shows another example of the circuit configuration of the phase adjusting means 81 shown in FIG. 1 or FIG. 5, and has a configuration in which the resistance value R or the capacitance value C can be adjusted.
[0064]
That is, the phase adjusting means in FIG. 6A has a configuration capable of adjusting the resistance value R, and a plurality of (n) resistors 81b-1 to 81b are provided between the input node 81a and the output node 81d. −n are connected in parallel, and switch means 81 g-1 to 81 g -n composed of transistors and the like are connected in series to the respective resistors 81 b-1 to 81 b-n. Each of the switch means 81g-1 to 81g-n is turned on and off by a buffer 81f driven by switch switching data stored in a memory 81e. The output node 81d is connected to GND via the capacitor 81c.
[0065]
In the phase adjusting means shown in FIG. 6A, a variation ± α ° of the phase θ of the detection signal S72 output from the synchronous detection circuit 72 is measured, and the variation is controlled within a predetermined range. The switch means 81g-1 to 81g-n are switched according to the switch switching data stored in 81e, so that the resistance value R can be adjusted. Thereby, the variation ± α ° of the phase θ can be easily and accurately suppressed within a predetermined range.
[0066]
The phase adjusting means in FIG. 6B has a configuration capable of adjusting the resistance value R, similarly to FIG. 6A, and a plurality of (n) are provided between the input node 81a and the output node 81d. The resistors 81b-1 to 81b-n are connected in series, and the resistors 81b-1 to 81b-n are further connected in parallel with switch means 81g-1 to 81g-n each formed of a transistor or the like. ing. Each of the switch means 81g-1 to 81g-n is turned on and off by a buffer 81f driven by switch switching data stored in a memory 81e. The output node 81d is connected to GND via the capacitor 81c.
[0067]
In the phase adjusting means of FIG. 6B, similarly to FIG. 6A, the variation ± α ° of the phase θ of the detection signal S72 output from the synchronous detection circuit 72 is measured, and the variation is determined by a predetermined value. In order to control the resistance R within the range, the switch means 81g-1 to 81g-n are switched according to the switch switching data stored in the memory 81e, and the resistance value R can be adjusted. Thereby, the variation ± α ° of the phase θ can be easily and accurately suppressed within a predetermined range.
[0068]
6C has a configuration capable of adjusting the capacitance value C. The input node 81a is connected to the output node 81d via the resistor 81b, and the output node 81d is connected to the GND. , A plurality (n) of capacitors 81c-1 to 81c-n are connected in parallel, and each of the capacitors 81c-1 to 81c-n is connected to switch means 81g-1 to 81g composed of a transistor or the like. −n are connected in series. Each of the switch means 81g-1 to 81g-n is turned on and off by a buffer 81f driven by switch switching data stored in a memory 81e.
[0069]
In the phase adjusting means of FIG. 6C, the variation ± α ° of the phase θ of the detection signal S72 output from the synchronous detection circuit 72 is measured in the same manner as in FIG. In order to control the capacitance value within the range, the switch means 81g-1 to 81g-n are switched according to the switch switching data stored in the memory 81e, and the capacitance value C can be adjusted. Thereby, the variation ± α ° of the phase θ can be easily and accurately suppressed within a predetermined range.
[0070]
(Modification)
The present invention is not limited to the above embodiment, and various modifications are possible. For example, there are the following modifications (1) to (5).
[0071]
(1) The vibrator 30 has been described by taking a piezoelectric vibrator such as a tuning fork type crystal vibrator as an example. However, other types such as a vibrating piece type other than the tuning fork type, an H type, a ring type, or the like may be used. It is also possible to use a piezoelectric material other than quartz as the child material. Furthermore, the number, arrangement position, and the like of the drive electrodes 31a and 31b and the detection electrodes 32a and 32b can be appropriately changed.
[0072]
(2) As the vibrator 30, a vibrator having another structure such as a silicon vibrator other than the piezoelectric vibrator may be used. When using a vibrator having another structure, the circuit configuration of the angular velocity detection circuit 60 in FIG. 1 is changed in accordance with the structure of the vibrator, and the I / V conversion circuit 41 in FIG. If a change such as replacement with another circuit is made, the effect as in the embodiment can be obtained.
[0073]
(3) To simplify the circuit configuration of the angular velocity detection circuit 60, the number of elements of the circuit is reduced by omitting the inverting amplifier 64 in FIG. 5 and replacing the differential amplifier 63 with an inverting differential amplifier. Can be reduced. Further, the angular velocity detection circuit 60 in FIG. 5 can be constituted by one I / V conversion circuit or the like. In this case, for example, one of the two detection electrodes 32a or 32b provided on the vibrator 30 is connected to a fixed potential node, and the electric charge output from the other electrode is converted into a voltage by one I / V conversion circuit. Then, the angular velocity detection signal S64 may be generated. Thus, the circuit configuration of the angular velocity detection circuit 60 can be further simplified.
[0074]
(4) The synchronous detection circuit 72 may be configured by another circuit in addition to the multiplication circuit. For example, the output voltage S41 is converted into a square wave signal, the output signal S71 of the phase shift circuit 71 is detected based on the square wave signal, and the polarity of the detected signal is switched to generate a detection signal S72 having the same polarity. A circuit configuration or the like that generates the data may be employed.
[0075]
(5) Even if the phase adjusting means 81 provided on the input side of the smoothing section 82 is provided on the output side of the smoothing section 82 to adjust the phase of the output of the smoothing section 82, almost the same as in the above embodiment. Function and effect are obtained. Further, the phase adjusting means 81 and the smoothing section 82 may be constituted by circuits other than those shown.
[0076]
【The invention's effect】
As described in detail above, according to the present invention, even if the frequency difference varies due to a manufacturing error or the like, the phase is adjusted by the phase adjusting means, so that the variation in the phase of the detection signal falls within a predetermined range. Be suppressed. As a result, the detection accuracy of the DC detection signal can be improved with a relatively simple circuit configuration. Further, when the phase adjusting means is constituted by a fixed RC LPF or a variable RC LPF, by setting the resistance value R of the resistor and the capacitance value C of the capacitor to predetermined values, the phase variation of the detected signal can be reduced. It can be easily suppressed within a predetermined range. Furthermore, if the configuration is such that the detection signal is generated by multiplying the drive signal and the angular velocity detection signal, the phase shift due to the temperature change can be simply and accurately canceled, and the detection accuracy can be further improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a main part of an angular velocity sensor according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a conventional angular velocity sensor.
FIG. 3 is an operation waveform diagram of FIG.
FIG. 4 is an operation waveform diagram of FIG.
FIG. 5 is a configuration diagram of an angular velocity sensor according to a second embodiment of the present invention.
FIG. 6 is a circuit diagram of a phase adjusting unit according to a third embodiment of the present invention.
[Explanation of symbols]
30 vibrator
40 drive circuit
41 I / V conversion circuit
42 AGC circuit
50 Coriolis force detection circuit
60 angular velocity detection circuit
71 Phase shift circuit
72 Synchronous detection circuit
80 smoothing circuit
81 Phase adjustment means
82 smoothing part

Claims (4)

A drive circuit that outputs an AC drive signal,
A vibrator that is excited by the drive signal and outputs a vibrator signal whose amplitude changes according to the magnitude and direction of the angular velocity,
An angular velocity detection circuit that converts the vibrator signal into an angular velocity detection signal,
A synchronous detection circuit that synchronously detects the angular velocity detection signal and outputs a detection signal of the same polarity based on the drive signal;
A smoothing circuit that smoothes the detection signal and outputs a DC detection signal according to the angular velocity;
The detection signal or the DC detection is connected to an input side or an output side of the smoothing circuit so as to cancel a frequency difference between a first resonance frequency on the drive circuit side and a second resonance frequency on the angular velocity detection circuit side. Phase adjusting means for adjusting the phase of the signal;
An angular velocity sensor comprising: 2. The angular velocity sensor according to claim 1, wherein said phase adjusting means is constituted by a low-pass filter including a resistor and a capacitor. 2. The angular velocity sensor according to claim 1, wherein the phase adjusting unit is configured by a low-pass filter including a resistor and a capacitor, and the resistor is configured by a variable resistor or the capacitor is configured by a variable capacitor. 4. The angular velocity sensor according to claim 1, wherein the synchronous detection circuit is configured to generate the detection signal by multiplying the drive signal and the angular velocity detection signal. 5.

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