JPH0820258B2 - Driving method of vibrating gyro - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for driving a vibrating gyro.

[Prior Art] The vibration gyro includes a tuning piece type, a tuning fork type, and the like. FIG. 3 shows a general tuning fork type vibration gyro. Reference numeral 1 is a tuning fork (that is, a vibrator), and 2 is a driving piezoelectric element attached to both right and left sides of the tuning fork 1. When an AC voltage is applied to the driving piezoelectric element 2 to excite the tuning fork 1 in the Y-axis direction in the left-right opposite directions, unless the tuning fork 1 rotates with respect to the Z-axis, the tuning fork 1
Simply continues the vibration in the Y-axis direction (shown by the arrow (a)), but when the tuning fork 1 rotates with respect to the Z-axis,
Coriolis force (indicated by arrow (b)) is generated in tuning fork 1,
The tuning fork 1 vibrates in the X-axis direction. Although details are omitted, if the vibration of the tuning fork 1 in the X-axis direction is detected, the Coriolis force can be detected, and the rotation applied to the vibration gyro can be detected.

There are two methods of driving the tuning fork 1 described above, that is, the separately excited vibration and the self excited vibration, but conventionally, either one of the separately excited vibration and the self excited vibration was adopted. The conventional method of separately excited vibration is to set the frequency of the separately excited vibration to the natural frequency of the tuning fork previously examined, and excite the tuning fork at the set constant natural frequency. The method of self-excited vibration is that a piezoelectric element for self-excited vibration is attached to the same vibrating surface as that of the piezoelectric element for driving 2 to form positive feedback. The input was made in phase to excite the tuning fork.

[Problems to be Solved by the Invention] In order to obtain a sufficient detection output, it is necessary to vibrate the tuning fork 1 with a sufficiently large amplitude.
The amplitude of the axial vibration becomes maximum when the excitation frequency is equal to the natural frequency of the tuning fork 1. For this reason, it is necessary to match the excitation frequency with the natural frequency of the tuning fork 1. However, in the conventional method of separately excited vibration, the natural frequency of the tuning fork 1 and the oscillation frequency of the external oscillation circuit change depending on the temperature. However, there is a problem that the natural frequency and the excitation frequency deviate from each other.

Further, in the conventional method of self-excited vibration, the driving piezoelectric element 2
Since there is a phase difference between the frequency of the excitation applied to and the frequency detected by the piezoelectric element for self-excited vibration, it is necessary to correct with a phase shifter when configuring positive feedback, but this phase shifter itself also changes with temperature. Therefore, there is a problem that accurate correction cannot be performed.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a vibration gyro that can always drive a vibrator at an excitation frequency that matches the natural frequency of the vibrator without being affected by temperature changes. .

[Means for Solving Problems] In order to solve the above problems, the present invention alternately vibrates the vibrator by repeating forced vibration and free vibration, and The frequency is detected, and at the time of the next forced vibration, the forced vibration of the vibrator is performed at the excitation frequency corrected so as to match the frequency of the detected vibration.

[Operation] In the vibration gyro having the above-described configuration, forced vibration and free vibration are alternately repeated, but naturally, at free vibration, the vibrator vibrates at the natural frequency of the vibrator. Further, in the case of forced vibration, it vibrates at the excitation frequency corrected so as to match the frequency of the vibration detected during free vibration (this is the natural frequency as described above). Therefore, even if the natural frequency of the vibrator changes due to temperature change, the vibrator is always excited at the actual natural frequency.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a vibrating gyro drive method of the present invention. Driving piezoelectric elements 2 are attached to both left and right sides of a tuning fork 1, and an exciting vibration detecting piezoelectric element 3 is attached to the same vibrating surface. Is attached. As shown in the figure, the circuit for driving the driving piezoelectric element 2 is a phased loop lock circuit (PL) including a phase comparator 4, a low-pass filter 5, an amplifier 6 and a voltage controlled oscillator 7.
L) 8, an automatic gain control device (AGC) 9, an analog switch 10, a holding circuit 11, and a rectangular wave oscillation circuit 12.

The vibration operation of the above configuration will be described. Second
The figure is a time chart of the drive circuit. The figure (a) shows the output of the rectangular wave oscillation circuit 12, and the figure (b) shows the vibration of the vibrator. Now, it is assumed that the driving piezoelectric element 2 is driven by the AC voltage having the oscillation frequency f of the voltage controlled oscillator 7 and the tuning fork 1 is forcibly vibrated at the frequency f. This period is the period indicated by period A in the time chart of FIG.
Outputs an output of level H, and the analog switch 10 is in the ON state. Therefore, as described above, the output having the frequency f of the voltage controlled oscillator 7 is applied to the driving piezoelectric element 2. After that, when the output of the rectangular wave oscillating circuit 12 becomes zero (the period indicated by B), the analog switch 10 is turned off by the L level signal from the rectangular wave oscillating circuit 12, and the driving voltage to the driving piezoelectric element 2 is changed. Be cut off. Therefore, the tuning fork 1 becomes free vibration. The frequency of this free vibration is the natural frequency, and this is f ₀ . During this free vibration period, the excitation vibration detecting piezoelectric element 3 detects the natural frequency f ₀ of the tuning fork, and the phase comparator 4 detects the natural frequency f ₀ and the oscillation frequency f of the voltage controlled oscillator 7. To compare. The output is an output according to the difference f−f ₀ = δf between the oscillation frequency f of the voltage controlled oscillator 7 and the natural frequency f ₀ , and the low pass filter 5
The unnecessary high frequency part is removed by and is amplified by the amplifier 5. However, since the holding circuit 11 is off, it is not held. When the next H-level rectangular wave of the rectangular wave oscillating circuit 12 comes, the holding circuit 11 is turned on by the signal and operates to hold the input signal from the PLL 8, that is, the signal of the phase difference δf. Then, the signal of the phase difference δf is input to the voltage controlled oscillator 7, and the analog switch 10 is switched on by the H level signal from the rectangular wave transmission circuit 12, and is forced again by the oscillation frequency of the voltage controlled oscillator 7. It becomes a vibration. In this case, the voltage controlled oscillator 7 outputs the phase difference data δf whose oscillation frequency is held in the holding circuit 11.
The output is output at a frequency that matches the natural frequency f ₀ . Therefore, the frequency of the forced vibration at this time is the actual natural frequency f ₀ of the tuning fork at that time. With respect to the amplitude of the forced vibration, the automatic gain control device 9 automatically adjusts the amplitude based on the output of the piezoelectric element 3 for detecting the excitation vibration, and keeps the amplitude constant. In this way, even if the natural frequency of the tuning fork changes due to the temperature change, the voltage controlled oscillator 7 changes the oscillation frequency following the change and excites the tuning fork at the actual natural frequency.

Note that various concrete driving circuit configurations for applying the method of the present invention are not limited to those of the embodiments.

Further, although the present invention has been described with respect to the tuning fork type vibration gyro, it is naturally applicable to other types such as a tuning piece type vibration gyro and an H type vibration gyro.

As described above, according to the method of the present invention, forced vibration and free vibration are alternately repeated to vibrate the vibrator, and the frequency of vibration of the vibrator is detected during the free vibration period. At the time of the next forced vibration, the forced vibration of the vibrator is performed at the excitation frequency corrected to match the detected vibration frequency, so the natural frequency of the vibrator is always matched without being affected by temperature changes. It became possible to drive the oscillator with the excitation frequency.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a block diagram of a drive circuit of a vibration gyro, FIG. 2 is a time chart, and FIG. 3 is a perspective view of a main part of a general vibration gyro. 1 ... Tuning fork (vibrator), 2 ... Driving piezoelectric element, 3 ... Excitation vibration detection piezoelectric element, 4 ... Phase comparator, 5 ... Low-pass filter, 6 ... Amplifier, 7 ... Voltage control Oscillator, 8 ... Phased loop lock circuit (PLL), 9 ... Automatic gain control device, 10 ... Analog switch, 12 ... Square wave oscillator circuit.

Claims (1)

[Claims] 1. A vibrator is vibrated by alternately repeating forced vibration and free vibration, and the frequency of vibration of the vibrator is detected during the period of free vibration, and the frequency of the detected vibration is detected at the time of the next forced vibration. A method for driving a vibration gyro, characterized in that forced vibration of a vibrator is performed at an excitation frequency corrected so as to coincide with each other.