JPH09243376A - Piezoelectric vibrating gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-accuracy piezoelectric vibrating gyro which is small in stationary-state output and changes little in temperature. SOLUTION: A drive detecting circuit for exciting and detecting the vibration of the vibrator 13 of a piezoelectric vibrating gyro comprises a differential amplifier 9, a synchronous detecting circuit 10, a low-pass filter 11, a bias temperature compensating circuit 14, an oscillating circuit 12, and a drive circuit 13, the bias temperature compensating circuit 14 causing the change in temperature in accordance with temperature change of a stationary-state output of the piezoelectric vibrating gyro (unnecessary voltage output when the gyro is not turning) to cancel out a bias level so as to make the stationary-state output of the piezoelectric vibrating gyro smaller and to reduce the rate of temperature change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a piezoelectric vibrator in a gyroscope used for attitude control of a moving body such as a ship or an automobile, equipment mounted on the moving body, navigation system of an automobile, and the like. The present invention relates to a so-called piezoelectric vibrating gyro, and particularly to a configuration of an electric circuit for driving and detecting a piezoelectric vibrator used in a piezoelectric vibrating gyro or the like.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyro is a gyroscope which utilizes a mechanical phenomenon in which a Coriolis force is generated in a direction perpendicular to the vibrating direction when a rotating angular velocity is applied to a vibrating object. In a vibration system configured to be capable of exciting and detecting in two directions orthogonal to each other, when one of the vibrations is excited and the vibrator itself is rotated about a line where two vibrating surfaces intersect, By the action of the Coriolis force mentioned above, a force acts in the direction perpendicular to this vibration,
The other vibration is excited. Since the magnitude of this vibration is proportional to the magnitude of the vibration on the input side and the rotational angular velocity, when the input voltage is kept constant, the magnitude of the output voltage proportional to the magnitude of this vibration causes The size can be calculated.

FIG. 9 is a structural schematic view of a piezoelectric vibrator used in a conventional piezoelectric vibrating gyro, and shows the operating principle of the vibrating gyro. The X-direction surface of the quadrangular prism vibrator 1 made of a constant elastic metal such as Elinvar, and Y
Piezoelectric elements 21 and 22 are provided on the respective surfaces in the direction. When a voltage is applied to the piezoelectric element 21 provided on the surface in the X direction and a rotational angular velocity (indicated by ω around the Z direction as an axis in the drawing) is applied in a state where vibration in the X direction is excited,
Vibration in the Y direction is excited by the Coriolis force, and this vibration in the Y direction is detected by the piezoelectric element 22 provided on the surface in the Y direction.

FIG. 1 is a perspective view showing the structure of a piezoelectric ceramic vibrator used in a piezoelectric vibrating gyro relating to the present invention, and FIG. 2 is a sectional view thereof. Six strip-shaped interdigital electrodes 41 to 46 are provided on the outer periphery of a cylindrical piezoelectric ceramic vibrator 3 (hereinafter, simply referred to as a vibrator), and the space between the electrodes is as shown in FIG. The polarization treatment is applied in the direction of the broken arrow. Interdigital electrodes 42, 44, 46
Are connected on the oscillator and are used by connecting to a reference potential as a common terminal. Here, the interdigital electrodes 41, 4
The flexural vibration of the vibrator 3 can be excited or detected by the piezoelectric effect of 3, 45 and the common terminals located on both sides of each. Here, the electrode 41 is used as a drive terminal, and an AC voltage is applied between the electrode 41 and the common terminal (reference potential) to excite bending vibration in the X direction (the direction of vibration to be excited is defined as the X direction). When a rotational angular velocity (with the axis of the oscillator as the axis) is applied in this state, vibration in the Y direction (direction perpendicular to the excitation direction) is excited by the Coriolis force,
An output voltage proportional to the rotational angular velocity can be obtained from the outputs from the electrodes 43 and 45.

FIG. 8 shows an example of a drive detection circuit of a conventional piezoelectric vibrating gyro. Electrode 4 of oscillator 3
The common terminal connecting 2, 44 and 46 is connected to the reference potential. The first detection terminal (electrode 43) and the second detection terminal (electrode 45) are connected to the differential amplifier 9 and the oscillation circuit 1.
2 are connected. The oscillator circuit 12 is connected to the drive terminal 41 of the vibrator 3 via the drive circuit 13 to form a self-excited oscillation loop, and an AC voltage having a frequency following the resonance frequency of the vibrator 3 is applied to the drive terminal 41. When applied, the bending vibration in the X direction is excited. Since the detection electrodes 43 and 45 are arranged symmetrically with respect to bending vibration in the X direction, the differential amplifier 9 cancels the output of the X direction component. Since the outputs of the detection electrodes 43 and 45 are in opposite phase with respect to the bending vibration excited by the Coriolis force, the output of the differential amplifier 9 is the output of the Y direction component, that is, the AC voltage proportional to the rotational angular velocity. Only output. The output of the differential amplifier 9 is synchronously detected by the synchronous detection circuit 10, and the low pass filter 1
As a result of being rectified by 1, a DC voltage proportional to the rotational angular velocity is output to the output terminal 19.

Here, considering the output voltage (output at rest) of the output terminal 19 in the state where the rotational angular velocity is not applied, ideally, as described above, the output terminals 43 and 45.
Output is the same, the output at rest is zero, but in reality,
The output terminals 43 and 4 are affected by the processing accuracy of the vibrator 3.
It is usual that an output difference occurs in 5 and does not become zero.

[0007]

As described above, in the conventional piezoelectric vibrating gyro, the output in the stationary state does not become zero, and further, the detection accuracy of the piezoelectric vibrating gyro is deteriorated due to the change of the ambient temperature. There was a problem. Conventionally, it has been difficult to stably reduce the output at rest including the temperature change.

It is an object of the present invention to cancel a static output and a temperature change of the static output caused by a problem such as machining accuracy of a vibrator by an electric circuit, so that the static output is small, and the static output is small. The purpose is to obtain a small and highly accurate piezoelectric vibrating gyro with a small temperature change.

[0009]

[Means for Solving the Problems]

(1) When a rotational angular velocity is applied to a vibrating object (hereinafter, this exciting vibration direction is referred to as X direction), a direction perpendicular to the exciting direction (hereinafter, this vibrating direction is referred to as Y direction). ), A gyroscope using a mechanical phenomenon of generating a Coriolis force in a gyroscope that is configured to be capable of excitation and detection in the X and Y directions orthogonal to each other using piezoelectric characteristics. In a scope, a so-called piezoelectric vibration gyro, a piezoelectric vibration gyro drive detection circuit for exciting and detecting the vibration of the vibrator of the piezoelectric vibration gyro, a differential amplifier, a synchronous detection circuit,
Comprised of a low-pass filter, bias temperature compensation circuit, oscillation circuit, and drive circuit, the output of the piezoelectric vibration gyro at rest (unwanted output voltage when no rotation angular velocity is given, that is, when there is no rotation) changes with temperature. Accordingly, the bias temperature compensating circuit changes the bias level with respect to the temperature and cancels the bias level, thereby reducing the temperature change of the output of the piezoelectric vibration gyro at rest, thereby obtaining a piezoelectric vibration gyro.

(2) The bias temperature compensating circuit described in (1) above is composed of two temperature sensitive elements such as a diode, a temperature sensitive resistor, or a thermistor, a resistor, and an operational amplifier. The temperature element has a positive polarity from the circuit reference potential (zero-point potential) and is configured to output a voltage according to temperature. The second temperature sensing element has a negative polarity from the circuit reference potential. , The output voltage according to the temperature is configured to be output, the output voltage of these temperature sensitive elements is configured to be added and output via a resistor or the like, and the output voltage of this temperature sensitive element is It is configured to be added via a resistor or the like and input to the operational amplifier. By selecting the resistance value between the output of this temperature sensitive element and the input of the operational amplifier, the ratio of addition of the output of the first temperature sensitive element and the output of the second temperature sensitive element is changed, and the bias of the operational amplifier is changed. A bias temperature compensation circuit for a piezoelectric vibrating gyro, which is characterized in that the temperature change of the output can be changed with an arbitrary positive / negative slope.

Using the piezoelectric vibrating gyro drive detecting circuit to which the bias temperature compensating circuit of the present invention described above is used, first, the output temperature change at rest of the vibrating gyro in the initial state (when there is no bias temperature compensation). Is measured and adjusted so that the Bayesian voltage is compensated with a polarity and a gradient according to the magnitude, a piezoelectric vibrating gyro with a small change in output temperature at rest can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, description will be made with reference to examples.

(Embodiment) FIG. 1 is a perspective view showing an example of a piezoelectric ceramic vibrator for a piezoelectric vibration gyro, and FIG.
FIG. 2 is a cross-sectional view showing an electrode arrangement and a polarization direction of the vibrator of FIG. 1. The vibrator 3 is a cylinder made of piezoelectric ceramic such as PZT. Six strip-shaped interdigital electrodes 4 on the outer periphery of the vibrator 3.
1 to 46 are provided, and a polarization process is performed between the electrodes in the arrow direction shown in FIG. Interdigital electrodes 42, 4
4, 46 are connected on the vibrator and are connected to the reference potential as common terminals. Here, the cross finger electrode 4
The bending effect of the vibrator 3 can be excited or detected by the piezoelectric effect of 1, 43, 45 and the common terminals on both sides thereof. Here, using the electrode 41 as a drive terminal, an AC voltage is applied between the electrode 41 and the reference potential to excite bending vibration in the X direction. When a rotational angular velocity is applied around the axial direction of the vibrator in this state, vibration in the Y direction is excited by the action of the Coriolis force, and the output of the electrodes 43 and 45 can provide an output voltage proportional to the rotational angular velocity. it can.

FIG. 3 is a block diagram for explaining the drive detection circuit of the piezoelectric vibrating gyroscope in one embodiment of the present invention. The electrodes 42, 44 and 46 of the vibrator 3 are connected to the reference potential as common terminals. The first detection terminal (electrode 43) and the second detection terminal (electrode 45) are connected to the differential amplifier 9 and the oscillation circuit 12. The oscillator circuit 12 is connected to the drive terminal (electrode 41) of the vibrator via the drive circuit 13 to form a self-excited oscillation loop, and an AC voltage having a frequency that follows the resonance frequency of the vibrator is applied to the drive terminal ( It is applied to the electrode 41) to excite bending vibration in the X direction. Since the detection electrodes 43 and 45 are symmetrical with respect to the bending vibration in the X direction, the differential amplifier 9 cancels the output of the X direction component. With respect to the bending vibration excited by the Coriolis force, the outputs of the detection electrodes 43 and 45 have opposite phases, so the output of the differential amplifier 9 is the output of the Y-direction component,
That is, only the AC voltage proportional to the rotation angular velocity is output. The output of the differential amplifier 9 is synchronously detected by the synchronous detection circuit 10 and rectified by the low-pass filter 11, so that a DC voltage proportional to the rotational angular velocity is output to the output terminal 19. The output of the output terminal 19 is the bias temperature compensation circuit 1
4, the bias voltage is canceled in accordance with the temperature change of the stationary output output to the output terminal 19 to reduce the stationary output, and then the output is output to the output terminal 20.

Next, the operation of the bias temperature compensation circuit will be described with reference to FIG.
The circuit example will be described.

One end of the first temperature sensitive element 51 (a diode is used as an element having a temperature sensitive function in this embodiment) has a reference potential Vc higher than the reference level Vref of the circuit.
It is connected from c via a resistor 61, and the other end of the first temperature sensitive element 51 has a reference level Vr.
ef is connected. One end of the second temperature sensitive element 52 is
It is connected to the reference potential Vee lower than the reference level via the resistor 62. The potential Vin of the terminal 19, the outputs VT1 and VT2 of the temperature sensitive element, the bias voltage adjusting resistor 66.
The output Vos is from resistors 68, 63 and 6 respectively.
It is input to the inverting terminal of the operational amplifier 7 via 4, 65 and is fed back by the resistor 67 to form an adding circuit, which is output to the output terminal 20 of the bias temperature compensation circuit by each voltage. The voltage V0

V0 = Vref− (Vin / R68 + VT1 / R63 + VT2 / R64 + Vos / R66) × R67 (1)

As shown in FIG. 5, the outputs VT1 and VT2 of the temperature sensitive element have a characteristic that they are substantially the same voltage with respect to Vref and have a potential difference in the opposite direction and change with temperature. As can be seen from the equation (1), when the resistors 63 and 64 have the same resistance value (R), they do not have the temperature characteristics of the bias voltage, and R of 63> R of 64 or R of 63 <R < By setting R to 64, the temperature characteristic of the bias voltage can be corrected in the positive or negative direction. Here, as shown in FIG. 6, Vin, that is, the temperature change of the output at rest before temperature correction is measured, and the resistance value of the resistor 64 is selected according to this to cancel the temperature change of Vin. Furthermore, by adjusting the resistor 64,
Offset of V0 from Verf
If R is adjusted to zero by changing R, a piezoelectric vibration gyro with a small output at rest and a small temperature change can be obtained. FIG. 7 shows a temperature change of the output of the piezoelectric vibrating gyro at rest after the bias voltage temperature compensation.

In this embodiment, the case where the diode is used as the temperature sensitive element has been described, but the temperature sensitive resistance,
It is clear that the bias voltage can be adjusted by the same principle even if another temperature sensitive element such as a thermistor is used.

[0020]

When a piezoelectric vibration gyro is constructed and adjusted using the bias voltage temperature compensation circuit of the piezoelectric vibration gyro of the present invention, a highly accurate piezoelectric vibration gyro with a small output at rest and a small temperature change can be obtained. . The industrial value of obtaining a compact and highly accurate piezoelectric vibrating gyro is great.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a vibrator for a piezoelectric vibrating gyroscope of the present invention.

FIG. 2 is a cross-sectional view showing an electrode arrangement and a polarization direction of the vibrator shown in FIG. 1 (arrows in the figure indicate polarization directions of the vibrator).

FIG. 3 is a block diagram showing an embodiment of a drive detection circuit for a piezoelectric vibration gy according to the present invention.

FIG. 4 is a circuit diagram for explaining in detail one embodiment of a bias temperature compensation circuit in the drive detection circuit of the piezoelectric vibration gy according to the present invention.

5 is a diagram showing a temperature change of an output of a temperature sensitive element of the bias temperature compensation circuit shown in FIG. 6 in the piezoelectric vibration gyro of the present invention.

FIG. 6 is a graph showing an example of a change in output temperature at rest before performing bias temperature compensation of the piezoelectric vibration gyro of the present invention.

7 is a diagram showing a change in output temperature of the piezoelectric vibrating gyro at rest when the bias temperature compensation circuit is adjusted according to a change of output at rest in the piezoelectric vibrating gyro of the present invention.

FIG. 8 is a block diagram showing an example of a conventional drive detection circuit for a piezoelectric vibration gyro.

FIG. 9 is a perspective view of a piezoelectric vibrator for explaining the operation principle of a conventional piezoelectric vibration gyro.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quadratic prism vibrator 21,22 Piezoelectric element 3 Piezoelectric ceramic vibrator 41, 42, 43, 44, 45, 46 Interdigital electrode 51, 52 Temperature sensitive element 61, 62, 63, 64, 65, 66, 67 Resistor 7 Operational Amplifier 9 Differential Amplifier 10 Synchronous Detection Circuit 11 Low Pass Filter 12 Oscillation Circuit 13 Drive Circuit 14 Bias Temperature Compensation Circuit 19 Output Terminal 20 Output Terminal After Bias Temperature Compensation Circuit

Claims (2)

[Claims] 1. A drive detection circuit for exciting and detecting vibration of a vibrator of a piezoelectric vibration gyro, a differential amplifier,
It is composed of a synchronous rectifier, a low-pass filter, a bias temperature compensation circuit, an oscillation circuit, and a drive circuit, and by changing the bias level by the bias temperature compensation circuit so as to cancel the temperature change of the static output of the piezoelectric vibrating gyro. A piezoelectric vibrating gyro, wherein the temperature change of the output of the piezoelectric vibrating gyro at rest is reduced. 2. The bias temperature compensation circuit according to claim 1, comprising two temperature sensitive elements, a resistor, and an operational amplifier, and the first temperature sensitive element of the two temperature sensitive elements is a circuit element. The second temperature sensing element is configured to output a voltage according to temperature with a positive polarity with respect to the reference potential, and the second temperature sensing element outputs a voltage according to temperature with a negative polarity with respect to the reference potential of the circuit. The output voltages of these temperature-sensitive elements are added via a resistor and input to an operational amplifier, and the resistance between the output of the temperature-sensitive element and the input of the operational amplifier is By selecting a value, the ratio of the addition of the first temperature-sensitive element output and the second temperature-sensitive element output is changed, and the temperature change of the bias output of the operational amplifier is changed to any positive or negative value. Piezoelectric vibration characterized by being configured to change with inclination Gyro bias temperature compensation circuit.