JP2007187606A - Vibrating gyroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibrating gyroscope removing detuning frequency noise without using a high order filter increasing a cost. <P>SOLUTION: The vibrating gyroscope electrically detects vibration due to Colrioli's force of an oscillator 11, synchronously detects the detection signal by using a drive signal resonating the oscillator 11, and obtains angle speed output S1 passing the detection output through a low pass filter 19. The vibrating gyroscope is provided with: a detuning frequency signal generator 21 for generating a signal S2 of a detuning frequency being a difference of a resonant frequency between a drive direction and a detection direction of the oscillator 11; a synchronous detection circuit 24 for sychronously detecting an angle speed output S0 by the detuning frequency signal S2; an integrator 25 for integrating output S4 of the synchronous detection circuit 24; a gain regulation circuit 22 for inputting the detuning frequency signal S2 and outputting to regulate the gain of the detuning frequency signal S2 by output S5 of the integrator 25; and a subtracting unit 23 for outputting as the angle speed output S0 by subtracting output S3 of the gain regulation circuit 22 from the angle speed output S1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibrating gyroscope that detects an input angular velocity.

FIG. 3A shows an example of the configuration of a vibrator used in a vibrating gyroscope. A vibrator 11 made of a piezoelectric body is formed in a prismatic shape in this example, and one end thereof is fixedly supported on a base 12. ing. Although not shown in FIG. 3A on the side surface of the vibrator 11, the drive electrodes 13 are respectively disposed on the side surfaces facing each other as shown in FIG. 3B, and the detection electrodes 14 are respectively disposed on the side surfaces orthogonal to these side surfaces. Has been placed.
By supplying a drive signal to the drive electrode 13, the vibrator 11 is resonantly driven. When an angular velocity is input around the axis of the vibrator 11 in this state, the vibrator 11 vibrates in a direction orthogonal to the drive vibration direction due to Coriolis force. This vibration is electrically extracted from the detection electrode 13.

FIG. 4 shows a general circuit configuration of the vibrating gyroscope. In the figure, reference numeral 15 denotes a drive circuit that generates a drive signal.
The detection signal extracted from the detection electrode 14 is input to the buffer 16 and subjected to impedance conversion, and the detection signal subjected to impedance conversion is input to the synchronous detection circuit 17. Since the vibration displacement of the vibrator 11 due to the Coriolis force occurs 90 degrees behind the drive signal, the detection signal is 90 degrees behind the drive signal. The detection signal input by the signal delayed in phase by 90 degrees is synchronously detected. In FIG. 4, reference numeral 18 denotes a phase circuit that delays the phase of the drive signal by 90 degrees and inputs it to the synchronous detection circuit 17.

The detection output of the synchronous detection circuit 17 has either a positive or negative waveform, and is smoothed by the low-pass filter 19 to become a DC voltage. The output of the low-pass filter 19 is amplified by the amplifier 20 and becomes an angular velocity output.
By the way, the detuning frequency FR, which is the difference (| FD−FE |) between the resonance frequency FD in the driving direction of the vibrator 11 and the resonance frequency FE in the detection direction for detecting vibration due to the Coriolis force, is a low-pass filter 19. Is set higher than the frequency of the angular velocity output determined by (frequency band of the detected angular velocity), but when vibration of a detuning equivalent frequency is applied to the vibrator 11 due to a disturbance or the like, for example, an angular velocity output having a relatively large detuning frequency FR. In other words, the vibration gyro as described above has a drawback that the angular velocity of the detuning frequency is output due to the influence of disturbance or the like.

On the other hand, there are a method of removing angular frequency output (detuned frequency noise) of the detuned frequency by sufficiently separating the detuned frequency (enlarge enough) and a method of removing the detuned frequency noise by a low-pass filter at the output stage Generally known. Japanese Patent Application Laid-Open No. H10-228561 describes that detuning frequency noise is removed by providing a bandpass filter in the detection circuit.
JP 2003-21516 A

However, if the detuning frequency is sufficiently increased, the vibration frequency in the driving direction and the vibration frequency in the detection direction are separated from each other, so that the effect of increasing the sensitivity due to resonance cannot be obtained. It will cause a decline. Further, in order to remove the detuning frequency noise by the low-pass filter at the output stage, a very high-order filter is required, that is, the cost is increased, and the vibration gyro is correspondingly expensive.
On the other hand, in the method described in Patent Document 1, a signal separated from the center frequency (resonance frequency in the driving direction) FD of the detection signal (amplitude modulation signal) before synchronous detection is removed by a bandpass filter. However, since it is removed by a filter, a high-order filter is required as in the method of removing the detuning frequency noise by the low-pass filter described above, and the cost is increased.

  In view of such circumstances, an object of the present invention is to provide a vibrating gyroscope capable of removing detuning frequency noise generated in an angular velocity output without using an expensive high-order filter.

According to the first aspect of the present invention, the vibration due to the Coriolis force of the vibrator is electrically detected, the detection signal is synchronously detected using the drive signal for resonantly driving the vibrator, and the detection output is low-pass filtered. In the vibration gyro configured to obtain the angular velocity output S1 by passing through, a separation frequency signal that generates a detuning frequency signal that is the difference between the resonance frequency in the driving direction of the vibrator and the resonance frequency in the detection direction in which vibration due to the Coriolis force is detected. A harmonic frequency signal generator, a synchronous detection circuit that synchronously detects the angular velocity output S0 with the detuning frequency signal generated by the detuning frequency signal generator, an integrator that integrates the output of the synchronous detection circuit, and a detuning frequency A gain adjustment circuit that receives a detuned frequency signal from the signal generator, adjusts the gain of the input detuned frequency signal with the output of the integrator, and outputs the angular velocity output S1. A subtractor for outputting as the angular velocity output S0 is provided by subtracting the output of Luo gain adjustment circuit.
In the invention of claim 2, in the invention of claim 1, the detuned frequency signal generator is constituted by a phase-locked loop having the angular velocity output S1 as an input signal.

  According to the present invention, detuning frequency noise generated in the angular velocity output can be removed without using a costly high-order filter, and thus a vibration gyro having good performance and low cost can be obtained. it can.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of an embodiment of a vibrating gyroscope according to the present invention. Parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this example, a detuning frequency signal generator 21, a gain adjustment circuit 22, a subtracter 23, a synchronous detection circuit 24, and an integrator 25 are provided in addition to the configuration shown in FIG.
The detuned frequency signal generator 21 has the same frequency as the detuned frequency noise generated in the output angular velocity output S1 through the synchronous detection circuit 17, the low-pass filter 19 and the amplifier 20 as in the conventional vibration gyro shown in FIG. The detuning frequency signal S2 is generated.

The detuning frequency signal S2 generated by the detuning frequency signal generator 21 is input to the gain adjustment circuit 22, and the gain adjustment circuit 22 adjusts the gain of the detuning frequency signal S2, and uses the adjusted signal as an output S3. Output. The subtracter 23 receives the angular velocity output S1 and the output S3 of the gain adjustment circuit 22, and the subtracter 23 outputs the result of subtracting the output S3 of the gain adjustment circuit 22 from the angular velocity output S1 as the angular velocity output S0.
The synchronous detection circuit 24 synchronously detects the angular velocity output S0 with the detuned frequency signal S2 generated by the detuned frequency signal generator 21, and the detected output S4 is input to the integrator 25 and integrated. The output S5 of the integrator 25 is input to the gain adjustment circuit 22, and the gain adjustment of the detuning frequency signal S2 described above is performed by the output S5 of the integrator 25.

The initial value (output S5) of the integrator 25 is 0. Therefore, the initial value of gain adjustment in the gain adjustment circuit 22 is 0, the output S3 of the gain adjustment circuit 22 is 0, and the angular velocity output S0 = S1. . The angular velocity output S0 is synchronously detected by the detuned frequency signal S2, but if the detuned frequency component included in the angular velocity output S1 is 0, the detected output S4 = 0, and the output S5 = 0 of the integrator 25 is obtained. Therefore, the gain of the gain adjustment circuit 22 is 0, and the output S3 = 0.
On the other hand, when the angular velocity output S1 includes a detuning frequency component, the initial value of the integrator 25 is 0, and the initial state of the output S3 of the gain adjustment circuit 22 is 0. Therefore, the angular velocity output S0 = S1, and the angular velocity output S0. Includes a detuning frequency component. When the angular velocity output S0 includes a detuning frequency component, the detection output S4 of the synchronous detection circuit 24 becomes a positive or negative full-wave rectified waveform, and this detection output S4 is integrated to obtain a value with a certain output S5 of the integrator 25. Become. Therefore, the gain of the gain adjustment circuit 22 becomes a certain value from 0, and the output S3 of the gain adjustment circuit 22 has a certain value. That is, the output S3 becomes a gain-adjusted detuning frequency signal, and the subtractor 23 performs angular velocity output S0 = S1-S3.

Thus, in this example, the gain adjustment circuit 22 performs the gain adjustment so that the detuning frequency component of the angular velocity output S0 becomes 0, and the output S3 is controlled, whereby the angular velocity output S0 is controlled. Thus, the angular velocity output S0 from which the detuning frequency component is removed, that is, the detuning frequency noise is removed is obtained.
In the above configuration, the detuning frequency signal generator 21 is preferably configured by a phase locked loop (PLL) having the angular velocity output S1 as an input signal. FIG. 2 shows a case where the detuned frequency signal generator 21 is constituted by a phase locked loop including a phase comparator (PC) 21a, a loop filter (LPF) 21b, and a voltage controlled oscillator (VCO) 21c. The controlled oscillator 21c has a sine wave output and is set in advance to a detuning frequency ± several Hz.

If the detuning frequency signal generator 21 is configured in a phase-locked loop as described above, when the angular velocity output S1 includes a detuning frequency component, the phase of the detuning frequency component and the phase of the detuning frequency signal S2 are included. Are controlled in phase with each other.
Further, even if the detuning frequency fluctuates due to factors such as manufacturing variations and temperature changes, such fluctuations in the detuning frequency automatically follow the fluctuation within the control range of the voltage controlled oscillator 21c. Even if there is, detuning frequency noise removal performance can be kept constant.
Note that the shape of the vibrator of the vibrating gyroscope is not limited to the shape shown in FIG. 3, and may be any other shape, and the present invention can be applied to any shape of vibrator. Can do. Further, the vibrator and its drive / detection system are not limited to the structure in which the drive / detection electrode is provided on the piezoelectric body, but the structure in which the drive and detection piezoelectric elements are attached to a constant elastic material such as an elimber. It may be a thing.

The block diagram which shows one Example of the vibration gyro by this invention. The figure for demonstrating one structural example of the detuning frequency signal generator in FIG. The figure for demonstrating one structure of the vibrator | oscillator of a vibration gyro. The block diagram which shows the conventional structure of a vibration gyro.

Claims (2)

The vibration due to the Coriolis force of the vibrator is electrically detected, the detection signal is synchronously detected using a drive signal for resonance driving the vibrator, and the angular velocity output S1 is obtained by passing the detection output through a low-pass filter. In the vibration gyro of the structure to obtain,
A detuning frequency signal generator that generates a signal of a detuning frequency that is a difference between a resonance frequency in the driving direction of the vibrator and a resonance frequency in a detection direction for detecting vibration due to Coriolis force;
A synchronous detection circuit for synchronously detecting the angular velocity output S0 with the detuned frequency signal generated by the detuned frequency signal generator;
An integrator for integrating the output of the synchronous detection circuit;
A gain adjustment circuit that receives a detuned frequency signal from the detuned frequency signal generator, adjusts the gain of the input detuned frequency signal with the output of the integrator, and
A vibration gyro comprising: a subtractor that subtracts the output of the gain adjustment circuit from the angular velocity output S1 and outputs the result as the angular velocity output S0. The vibrating gyroscope according to claim 1,
The detuning frequency signal generator is constituted by a phase-locked loop having the angular velocity output S1 as an input signal.

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