JP2002031533A - Gyro sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve temperature compensation at stable and easy-to-adjust measuring sensitivity by means of a relatively simple arrangement of a two-axis disc type vibrating gyro sensor self-excited for vibration under a steady state in a predetermined main vibration mode. SOLUTION: A differential frequency between the oscillating frequency of self-excited vibration and a natural frequency in another vibration mode is controlled to be held approximately constant relative to temperature changes, by causing the circuit constant of an oscillating circuit for the self-excited vibration to vary depending on temperature. Alternatively, the driving voltage of the oscillating circuit is controlled according to temperature for fine adjustment of the temperature compensation. In one embodiment, the oscillating circuit is a reverse amplification circuit and a feedback circuit determining its gain includes a temperature sensing element; or the temperature sensing element is used in a voltage dividing circuit which an AGC circuit includes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensation technique for measuring sensitivity in a vibration gyro sensor for detecting a rotational angular velocity.

[0002]

2. Description of the Related Art Vibrating gyro sensors, which have recently appeared, have been increasingly used for robot technology, virtual reality technology, and the like, including detection of camera shake, detection of movement of an automobile, and the like. At the same time, including the sensor vibrator, drive and detection circuit, multi-axis (one sensor can detect angular velocities around multiple rotation axes), stable performance, miniaturization, simplification, There is a need for further cost reduction, rationalization and simplification of configuration and adjustment.

[0003] It is important to achieve both a multi-axis sensor and a stabilization of characteristics in a use environment, in particular, a reduction in a change in sensor sensitivity to a use temperature. Factors affecting the sensor sensitivity include the stability of the frequency of the vibrating body and the stability of the operation of the drive / detection circuit. For this reason, the structure and material of the sensor vibrator and the material of the piezoelectric element used for driving (including the manufacturing method) are examined to minimize the change in the vibration state, and the temperature change is characterized by the characteristics such as the amplification factor of the detection circuit. Various sensor circuit methods have been devised to compensate for the change, but they have not always produced satisfactory results.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique for easily and reliably performing temperature compensation of sensor sensitivity with a simple circuit configuration in a two-axis vibration gyro sensor. .

[0005]

In order to achieve the above object, the configuration of the gyro sensor according to the present invention has the following features.

(1) A disk-shaped vibrator having a load mass at a position distant from the plate surface on the central axis is piezoelectrically driven in a concave-convex direction by a ring-shaped electrode film provided on its surface to set a main vibration mode. And providing, in the surface, vibration of the disk in another mode caused by Coriolis force acting on the additional mass when the disk-type vibrator rotates around two orthogonal axes parallel to the plate surface. In a two-axis gyro sensor configured to piezoelectrically detect two sets of sector electrodes to detect a rotational angular velocity with respect to the two axes, a circuit constant in an oscillation circuit for performing the main vibration is a function of temperature. By giving a temperature change to the oscillation frequency of the main vibration mode, and following the temperature change of the natural frequency of the other vibration mode, the difference between these two frequencies is controlled to be substantially constant with respect to the temperature change, and the angular velocity Further comprising a temperature compensation circuit for performing temperature compensation of the measurement sensitivity.

The configuration of the gyro sensor according to the present invention may further have at least one of the following features. (2) Further adjusting the temperature compensation by controlling the drive voltage of the oscillation circuit based on the temperature.

(3) The oscillation circuit is an inverting amplifier circuit as a whole, and the feedback circuit for determining the gain includes a temperature sensitive element.

(4) In the AGC circuit included in the oscillation circuit, the drive voltage is controlled by temperature using a temperature-sensitive element in a voltage dividing circuit involved in determining the drive voltage.

(5) A circuit having different functions with respect to temperature is connected to the drive electrode and the reference electrode of the sensor vibrator.

[0011]

1 and 2 are diagrams for explaining a first embodiment of a gyro sensor according to the present invention. FIG. 1 is a two-axis detection type sensor vibrator to which the present invention is applied, and FIG. It shows a circuit diagram for the driving and detection. FIG. 1A is a plan view of a sensor vibrator, FIG. 1B is a cross-sectional view, FIG. 1C shows a schematic shape of a fundamental vibration, and FIG. 1D shows a general shape of a Coriolis force. First, the sensor vibrator will be described with reference to FIG. It can be said that the structure of the sensor vibrator is basically known.

In FIGS. 1 (a) and 1 (b), reference numeral 1 denotes a vibrating disk, which is made of a constant elastic metal material such as an elinvar in order to reduce the temperature change of the natural frequency. 2 is PZT
And the like, are formed in a small disk shape by a piezoelectric porcelain plate, and have film-shaped electrodes for driving and detecting the sensor on both sides, and are adhered concentrically to one surface of the vibration disk 1 by an adhesive layer 3. . Reference numeral 4 denotes a metal ball as a load mass, which is welded to a ring-shaped seat provided at the center of the other surface of the vibrating disk 1. The vibrating disk 1, the piezoelectric porcelain plate 2, and the load mass 4 operate as an integrated sensor vibrator. These thicknesses are exaggerated for the sake of illustration. Reference numeral 5 denotes a silicon rubber support for supporting the sensor vibrator on the printed circuit board 6. Since the nodes of the sensor vibrator form a concentric circle of about 0.6 times the outer diameter of the vibrating disk 1, eight columns 5 are arranged at equal intervals along the circumference.

A reference electrode R is provided on the entire surface of one side of the piezoelectric ceramic plate 2 (on the side of the vibrating disk). A ring-shaped feedback electrode F and a drive electrode D are provided on the other surface, and four fan-shaped detection electrodes X1, X2, Y1, and Y2 are provided on the inner side. The polarization of the piezoelectric porcelain plate 2 is such that a piezoelectric effect is generated between the reference electrode R and each of the other electrodes for expansion and contraction parallel to the plate surface of the porcelain plate in the thickness direction.

FIG. 1 (c) shows a vibration mode of a main vibrating mode (oscillation mode) of the sensor vibrating body which is excited by the oscillating circuit. FIG.
Symmetric about the axis. The thick line is a neutral state, and the thin line is a state displaced to one side. That is, the reference electrode R and the drive electrode D
When a voltage is applied to the piezoelectric ceramic plate 2, the piezoelectric ceramic plate 2 expands or contracts, and the vibrating disk 1 is deformed to be convex or concave upward. The potential changes in the negative direction, and gives information to the oscillation circuit to maintain the self-excited oscillation.

FIG. 1D shows a vibration mode (detection mode) corresponding to the angular velocity detection. When the sensor vibrator rotates around the X-axis (or Y-axis), the load mass 4 that is vibrating up and down has a magnitude proportional to the angular velocity, the vibration velocity, and the mass. A Coriolis force acts in the orthogonal direction, and the load mass 4 is synchronized with the fundamental vibration (the phase is different by approximately 90 °) in the Y direction (or the X direction).
Move to Therefore, as shown in the figure, a waveform deformation (asymmetric with respect to the Z axis) component occurs in addition to the fundamental vibration. Since the expansion and contraction of the piezoelectric ceramic plate 2 with respect to this deformation is opposite on both sides of the center, the electrodes X1 and X2 (or the electrodes Y1 and Y2)
Produces a voltage of the opposite sign. Note that the natural frequency in the detection mode is the same for a cross section including any of the X and Y axes because the disk-shaped sensor vibrator is substantially axially symmetric.

In order to increase the amplitude of the detection mode, it is advantageous to make the natural frequency of the vibration close to the oscillation frequency of the main vibration mode (oscillation mode). However, if the frequencies of both modes are matched and resonated, degeneration occurs, and although the sensitivity is maximized, the temperature characteristics and the frequency response of the sensor sensitivity deteriorate, so a slight frequency difference (for example, when the excitation frequency is about 31 kHz, about 250 Hz) The difference). However, since each frequency has a different vibration mode, each temperature characteristic is different. Therefore, the difference does not become constant over the entire operating temperature range, changes considerably, and as a result, the sensitivity of the sensor to temperature becomes unstable as it is. This phenomenon is strongly related to the present invention.

The circuit of FIG. 2 and its operation will be described. The circuit connected to the upper half of the figure, that is, to the right of the feedback electrode F, the reference electrode R, and the drive electrode D is an oscillation circuit. The oscillation circuit as a whole amplifies the voltage detected on the feedback electrode F (relative to the reference electrode R) and supplies the amplified voltage to the drive electrode D and the reference electrode R, and the fundamental vibration is generated by the difference voltage between the drive electrode D and the reference electrode R. Acts as self-excited vibration. In the lower half of the figure, a circuit connected to the right of the detection electrodes X1, X2, Y1, Y2 is a detection circuit. The detection circuit has two sets of an X detection circuit and a Y detection circuit because the present embodiment is a two-axis gyro sensor.

The X detection circuit detects an angular velocity component of rotation about an axis parallel to the X axis. Since charges having different signs are generated in the electrodes X1 and X2 in proportion to the angular velocity components, each potential is amplified by the preamplifiers 31 and 32, and then a differential voltage is generated by the differential amplifier 41, which is basically controlled by a synchronous detection circuit. Detect and convert to DC at timing synchronized with vibration. LP detection output
Through F61, the DC amplifier 71 obtains a detection output Xout as a DC voltage proportional to the angular velocity component in the X-axis direction. This technique is basically known. Detection output Yout
Has the same configuration, and the preamplifier 3
3, 34, differential amplifier 42, synchronous detection circuit 52, LPF
The operation of the DC amplifier 72 is the same.

In the oscillation circuit, 11, 13, 21, 2
2 is an operational amplifier, R1 to R16 are ordinary resistance elements, RT1 and RT2 are temperature-sensitive resistance elements such as thermistors, and C1 to C5 are capacitance elements. Circuit 10 surrounded by a frame
Inside constitutes an inverting amplifier. An AGC circuit 12 controls the gain of the inverting amplifier 10. The temperature-sensitive feedback resistor circuit 8 and the temperature-sensitive voltage dividing circuit 9 surrounded by a frame are each a temperature-sensitive circuit part which forms the core of the temperature compensation technology of the present invention.

Turning now to the description of the temperature compensation technique of the present invention. In the present embodiment, it is possible to adjust the temperature compensation effect in two stages, fine and coarse. In the coarse adjustment, it works together with the inverting amplifier 10 to invert and amplify the detection voltage waveform of the feedback electrode F to give a voltage output to the reference electrode R, and to adjust the gain of the operational amplifier 21 operating as a non-inverting amplifier including the temperature-sensitive resistance element RT1. The temperature-sensitive feedback resistor 8 changes the gain as a function of temperature, and the gain changes with temperature.

The oscillation frequency of the fundamental vibration changes slightly (for example, several tens of Hz) with the change in the gain (the cause of the change is not necessarily sufficiently clarified,
This may be because the load impedance when the circuit is viewed from the electrode terminal of the vibrating body changes due to the change in the circuit constant giving the gain change. Alternatively, the amplitude of the vibrating body may change due to a change in gain, which may be due to the non-linearity of vibration with respect to the amplitude. ), The oscillation frequency of the fundamental vibration is changed depending on the temperature to follow the temperature change of the natural frequency of the detected vibration mode (this depends on the characteristics of the constituent materials of the vibrating body, and does not compensate for the circuit). The slight difference between the frequencies of the two modes is maintained at a substantially constant value within a wide temperature range. Thus, the temperature change of the sensitivity is corrected.

Fine adjustment of the temperature characteristics of the sensor sensitivity, that is, fine adjustment, is performed as follows. The detected voltage of the angular velocity is proportional to the Coriolis force, and the Coriolis force is proportional to the amplitude of the fundamental vibration. Therefore, when the drive voltage is increased to increase the amplitude, the detection sensitivity is also increased. By utilizing this, a temperature change is applied to the drive voltage applied to the drive electrode D to perform sensitivity correction that cannot be corrected by the coarse adjustment. In a specific example, the power supply voltage dividing circuit that determines the drive voltage amplitude in the AGC circuit that stabilizes the drive voltage includes the temperature-sensitive resistance element RT2, and the drive voltage is temperature-divided as the temperature-sensitive voltage divider 9. , A secondary correction is performed.

Although an example of the embodiment of the present invention has been described above, it is needless to say that various other embodiments can be obtained while maintaining the spirit of the present invention. The same applies to the container of the sensor vibrator and the support / connection structure in the container. Further, the driving circuit of the above embodiment has a feedback electrode F,
Although there are three terminals of the reference electrode R and the drive electrode D, the idea of the temperature compensation of the sensitivity by the change of the oscillation frequency due to the change of the circuit constant and the change of the drive voltage in the two-terminal oscillation circuit generally used for the excitation of the vibrator is also considered. Clearly applicable.

The material of the vibrating body is not necessarily a composite of metal and piezoelectric porcelain, and the entire main part may be made of a piezoelectric porcelain such as a bimorph type, quartz or other piezoelectric crystal material. The electrode configuration can also be changed according to the characteristics of the sensor vibrator. The circuit configuration may be different from that shown in FIG. The temperature sensing element is not limited to the thermistor resistance element, but may use the temperature characteristics of another element such as a semiconductor active element. .

[0025]

(1) The configuration in which the oscillation frequency of the main vibration mode is controlled to follow the frequency of the detection mode without compensating the temperature characteristics of each of the two detection circuits corresponding to the two axes. The detection sensitivity of both axes can be compensated for at the same temperature at once, and there is an effect that the temperature compensation of the gyro sensor can be achieved by a relatively simple circuit configuration and an easy adjustment method.

(2) Further, by finely adjusting the sensitivity by changing the drive voltage of the oscillation circuit depending on the temperature, the fine adjustment can be performed easily and independently of the coarse adjustment. (3) By making the feedback circuit constant of the amplifier a function of temperature, there is an advantage that a temperature compensation effect can be achieved with a simple configuration. (4) There is an effect that giving a temperature change to the AGC circuit can be easily implemented with a simple configuration.

(5) By connecting a circuit having different temperature functions to the reference electrode and the drive electrode, it is possible to easily adjust the temperature compensation.

[Brief description of the drawings]

1A and 1B show a sensor vibrator according to a first embodiment of the gyro sensor of the present invention, wherein FIG. 1A is a plan view, FIG. 1B is a cross-sectional view, FIG. d) shows the general shape of the deflection due to the Coriolis force.

FIG. 2 is a circuit diagram of the gyro sensor according to the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vibration disk 2 Piezoelectric porcelain plate 3 Adhesive layer 4 Load mass 5 Silicon support column 6 Printed circuit board 8 Temperature-sensitive feedback resistor circuit 9 Temperature-sensitive voltage dividing circuit 10 Inverting amplifier 11, 13, 21, 22 Operational amplifier 12 AGC circuit 31 , 32, 33, 34 Preamplifier 41, 42 Differential amplifier 51, 52 Synchronous detection circuit 61, 62 LPF 71, 72 DC amplifier D Drive electrode F Feedback electrode R Reference electrode X1, X2, Y1, Y2 Detection electrode X, Y, Z coordinate axes RT1, RT2 Thermosensitive resistance elements C1, C2, C3, C4, C5 Capacitance elements R1, R2, R3, R4, R5, R6, R7, R8, R
9, R10, R11, R12, R13, R14, R1
5, R16 resistance element

Claims (5)

[Claims] 1. A disk type vibrator having a load mass at a position distant from an upper central axis plate surface is piezoelectrically driven by a ring-shaped electrode film provided on its surface in a concave and convex direction to provide a main vibration mode. A vibration in a detection mode of the disk caused by Coriolis force acting on the additional mass when the disk-type vibrator rotates around two orthogonal axes parallel to the plate surface; Detected piezoelectrically by a set of sector electrodes,
In a two-axis gyro sensor configured to detect a rotational angular velocity about the two axes, a temperature change is given to an oscillation frequency of the main oscillation mode by setting a circuit constant of an oscillation circuit for performing the main oscillation as a function of temperature. A temperature compensation circuit for following the temperature change of the natural frequency of the other vibration mode, controlling the difference between these two frequencies substantially constant with respect to the temperature change, and performing temperature compensation of the measurement sensitivity of the angular velocity. A gyro sensor characterized by the following. 2. The gyro sensor according to claim 1, further comprising a circuit for controlling a drive voltage of said oscillation circuit based on a temperature to further adjust said temperature compensation. 3. The gyro sensor according to claim 1, wherein the oscillating circuit is an inverting amplifier circuit as a whole, and a feedback circuit for determining a gain includes a temperature-sensitive element. 4. The driving voltage is controlled by temperature using a temperature sensing element in a voltage dividing circuit involved in determining a driving voltage in an AGC circuit included in the oscillation circuit. Or 3 gyro sensors. 5. The gyro sensor according to claim 1, wherein a circuit giving a different function with respect to temperature is connected to the drive electrode and the reference electrode of the sensor vibrator.