JP3627643B2 - Vibrating gyro - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration gyro and, for example, to a vibration gyro that detects an angular velocity from an output of a bimorph vibrator used for camera shake correction, a navigation system, or the like.
[0002]
[Prior art]
FIG. 12 is an external perspective view showing an example of a bimorph vibrator used in a vibrating gyroscope. In FIG. 12, a bimorph vibrator 1 is formed by attaching two piezoelectric elements with their polarization directions opposite to each other so that the cross section becomes a quadrangle. When this vibrator 1 is driven to vibrate in the vertical vibration mode in the vertical direction (X-axis direction) and rotated at an angular velocity (Ω) in the longitudinal direction (Z-axis direction), the driving direction is determined by the Coriolis force. Vibration occurs in the transverse vibration mode synchronized with the vertical direction (Y-axis direction).
[0003]
Since the amplitude of the lateral vibration is proportional to the angular velocity, the value of the angular velocity is detected using this. Although not shown, the vibrator 1 is provided with left and right electrodes on one main surface and full-surface electrodes on the other main surface, and L (left) and R (right) signals are output from the left and right electrodes. . In such a vibrator 1, it is necessary to individually adjust the balance, null voltage (also referred to as offset voltage, neutral point voltage), and sensitivity.
[0004]
FIG. 13 is a block diagram of an angular velocity detection circuit for obtaining the output of the vibrator 1 shown in FIG. In FIG. 13, the difference between the two outputs of the vibrator 1 is amplified by the differential amplifier circuit 21, the amplitude waveform is detected by the synchronous detection circuit 22, smoothed by the smoothing circuit 23 to become a direct current voltage, and the direct current by the DC amplifier 24. Amplified. This signal contains a null voltage. When the signal is amplified by the DC amplifier 24, the null voltage is also amplified. For example, the DC component is cut by the DC cut circuit 25 constituted by a filter, for example, and the low-frequency AC signal corresponding to the change in the remaining angular velocity is amplified. The signal is further amplified by the circuit 26 and output as an analog signal. Here, the analog signal is converted into a digital signal by the A / D converter 27 and is given to the microprocessor 28 as an angular velocity detection signal to suppress camera shake and control for navigation.
[0005]
[Problems to be solved by the invention]
In the angular velocity detection circuit shown in FIG. 13, the L component and R component signals are output from the vibrator 1, and the differential signal is output by the differential amplifier circuit 21. Ideally, the null voltage should be 0V. However, if the left and right balance is shifted, the voltage of the shifted component is output as a null voltage. When the gain of the DC amplifier 24 is increased in order to amplify the signal component, the DC amplifier is saturated by the included null voltage, so that the upper limit of the absolute amplification degree of the DC amplifier is determined.
[0006]
Further, in order to cut the DC component by the DC cut circuit 25, for example, if a high-pass filter that passes only a signal of 0.1 Hz or higher is to be configured, a combination of a 20 μF large-capacity capacitor and a 1 MΩ resistor The high-pass filter is required, and the apparatus becomes large.
[0007]
Furthermore, in the circuit shown in FIG. 13, the output of the differential amplifier circuit 21 may be output with the left and right signal components out of phase or with the left and right signal components shifted in amplitude. Since the left and right signal components are sin waves, if the amplitude is shifted, only the amplitude of the differential output needs to be changed. However, if the left and right signal components are shifted in phase, the phase shifts relative to the reference signal. There is also a problem that the output signal is output.
[0008]
As another conventional example, Japanese Patent Publication No. 6-13970 discloses a vibrator in which the phase difference angle formed by the vector of the output voltage due to the angular velocity at the time of rotation of the vibrator and the vector of the null voltage at rest is 90 degrees. It is described that an angular velocity is detected from a phase difference of a combined vector of an output voltage and a null voltage by giving a drive signal to the detection side.
[0009]
However, in this example, the amplitude of the transducer output has linearity, but the phase difference-sensitivity relationship is basically not linear, and the nonlinearity tends to fluctuate due to the influence of the null phase. There is. For this reason, it is desirable to digitize the amplitude value of the Coriolis force.
[0010]
As such an example, Japanese Patent Application Laid-Open No. 62-150116 describes that the sample and hold is performed at the time when the angular velocity signal due to the drive of oscillation becomes maximum and minimum.
[0011]
Japanese Patent Application Laid-Open No. 7-260493 describes that a difference in passing current of piezoelectric elements is detected and sample-and-hold is performed at a timing when the displacement speed of the vibrator to be detected becomes zero. However, it does not describe how to digitally process the sampled and held signal.
[0012]
Therefore, a main object of the present invention is to provide an angular velocity detection circuit in a vibration gyro that samples and holds the Coriolis force regardless of the position of the Coriolis force phase, amplifies it, and digitizes it.
[0013]
Another object of the present invention is to provide an angular velocity detection circuit in a vibration gyro capable of detecting and correcting a null voltage.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 is a vibration gyro that detects vibration caused by Coriolis force generated in the Y-axis direction when the vibrator is excited in the X-axis direction and rotated around the Z-axis, and is output from the vibrator. Driving means for generating a reference signal based on the first and second signals and exciting the vibrator, and a differential signal including Coriolis force based on the first and second signals output from the vibrator A signal extracting means for extracting the signal, a timing signal generating means for generating a timing signal for sampling and holding the Coriolis force based on the reference signal output from the driving means, and the extracted differential signal based on the timing signal. A voltage-time axis conversion unit that samples and holds and outputs a small voltage change of the differential signal on the time axis and outputs it as an angular velocity detection signal is configured. The sample point is preferably in the vicinity of the peak value in terms of efficiency, but needless to say, the sample point is established without being specified in any phase.
[0015]
In the invention according to claim 2, the vibrator according to claim 1 includes a first electrode and a second electrode, each of which has a slight difference in amplitude and phase and outputs the first and second signals, and a full-surface electrode. And the driving means adds the first and second signals and outputs as a reference signal, a level control means for making the level of the reference signal output from the addition means constant, and level control Phase adjusting means for adjusting the phase of the reference signal output from the means and outputting the reference signal to the entire surface electrode.
[0016]
In the invention according to claim 3, the voltage-time axis conversion means according to claim 1 or 2 is configured to sample and hold the differential signal including the Coriolis force based on the timing signal, and the output signal of the sample hold means. Integrating means for integrating, and comparing means for comparing the integrated signals at a predetermined level and expanding and outputting to the time axis.
[0017]
In the invention according to claim 4, the voltage-time axis conversion means according to claim 1 or 2 samples the differential signal including the Coriolis force based on the timing signal and linearly decreases the peak value by the droop characteristic. And means for comparing the linearly decreasing signal at a predetermined level and outputting the expanded time axis.
[0018]
In the invention according to claim 5, the means for generating a timing signal for making the sampling point by the sample hold means different between a specific phase of the Coriolis force and another phase at another wavelength is compared with the sample hold value by the sample hold means. Then, the null differential voltage is inferred, and a predetermined level of the comparison means is controlled based on the inferred null differential voltage.
[0019]
In the invention according to claim 6, the timing signal generating means according to any one of claims 1 to 5 detects a leading edge and a trailing edge of the reference signal, counts the clock signal, and outputs a timing signal when a predetermined count value is reached. Is output.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram of a vibration gyro according to an embodiment of the present invention. In FIG. 1, the vibrator 1 is provided with a left electrode 1L, a right electrode 1R, and a full-surface electrode 1C, and a voltage + V is applied to the left electrode 1L and the right electrode 1R via resistors R1 and R2. . + V is usually a medium positive potential or a reference potential. From the left electrode 1L and the right electrode 1R, the L signal, which is the first signal, and the R signal, which is the second signal, are output including the Coriolis force, respectively. This is given to a certain differential amplifier circuit 3. The adder circuit 2 adds the L signal and the R signal and outputs an L + R signal. In this way, by adding the L signal and the R signal by the adder circuit 2, the Coriolis force is eliminated and a stable feedback signal is obtained.
[0021]
The above feedback signal is given as a reference signal to the AGC circuit 4 which is a level control means, and becomes a driving voltage having a constant level. This driving voltage is applied to the entire electrode of the vibrator 1 via the phase shift circuit 5 which is a phase adjusting means. 1C. The phase shift circuit 5 adjusts the phase of the output of the adder circuit 2 and adjusts so that the phase difference between the output of the adder circuit 2 and the driving voltage applied to the entire surface electrode 1C oscillates stably at a desired frequency. In this embodiment, the phase difference is almost zero. The vibrator 1, the adder circuit 2, the AGC circuit 4, and the phase shift circuit 5 constitute an oscillation circuit. The adder circuit 2, the AGC circuit 4, and the phase shift circuit 5 constitute drive means for exciting the vibrator 1.
[0022]
The reference signal output from the adder circuit 2 is supplied to a rectangular wave forming circuit 6 composed of a comparator, for example, and a rectangular wave is formed and supplied to the microprocessor 7 as a timing extraction signal. Note that the rectangular wave forming circuit 6 may be supplied with the driving voltage of the output of the phase shift circuit 5 as a reference signal, as shown by the dotted line in FIG.
[0023]
The microprocessor 7 discriminates the leading edge and the trailing edge of the timing extraction signal, counts the time from the leading edge to the trailing edge of the timing extraction signal with a reference pulse, and identifies the frequency based on the counted value. Therefore, the microprocessor 7 can easily determine the relationship between the frequency and phase of the reference signal output from the adder circuit 2. Further, the microprocessor 7 outputs a timing signal for sample hold based on the timing extraction signal to the VT conversion circuit 8 as voltage-time axis conversion means. That is, the rectangular wave forming circuit 6 and the microprocessor 7 constitute a timing signal generating means.
[0024]
The differential amplifier circuit 3 to which the L signal and the R signal output from the vibrator 1 are given outputs the differential signal as the output to the VT conversion circuit 8. The VT conversion circuit 8 diffuses a minute voltage change ΔE into a large time region ΔT. This is because the output of the differential amplifier circuit 3 has a low level and needs to be amplified. In the conventional DC amplifier circuit, as explained in the conventional example, it is saturated by the null voltage, so the upper limit of the amplification factor is determined. It solves the problem that it has been.
[0025]
On the other hand, in the embodiment of the present invention, the output voltage of the differential amplifier circuit 3 of a small level is diffused in the large time region ΔT, and it is compared with a predetermined level by a comparator to output a digital signal. For this reason, the VT conversion circuit 8 is provided with a sample hold circuit 81 as sample hold means, an integration circuit 82 as integration means, and a comparator 83 as comparison means. The sample hold circuit 81 samples and holds the output of the differential amplifier circuit 3 based on the timing signal from the microprocessor 7 and supplies it to the integration circuit 82. The integration circuit 82 integrates the sampled and held signal and outputs it to the comparator 83. The comparator 83 compares the integrated output with a predetermined level and outputs it to the microprocessor 7 as a digital signal having a duty ratio corresponding to Coriolis.
[0026]
2 and 3 are waveform diagrams of respective parts of the angular velocity detection circuit shown in FIG.
Next, a signal output from the vibrator 1 will be described with reference to FIG. The L signal (a) and R signal (b) output from the vibrator 1 have a slight difference in amplitude and phase. When the difference between the L signal (a) and the R signal (b) is taken, LR (c) is obtained, and when the sum is taken, L + R (d) is obtained.
[0027]
In LR (c), the zero-cross point moves as the phase shift between the L signal and the R signal increases. This LR signal is also called a null differential voltage. The LR signal is output with the Coriolis force superimposed, and is output as differential + Coriolis. Coriolis force has the property that it cannot be separated from the differential voltage even if it is desired to be separated. This is because the Coriolis force is not output as an actual signal as shown in FIG. In the following description, it is assumed that the LR signal means differential + Coriolis force. The Coriolis force (e) is in phase with L + R (d), and the Coriolis force is also maximized and minimized in the vicinity of the L + R maximum and minimum points. When the vibrator 1 is rotated left and right, the amplitude of the Coriolis force (e) changes, and the phases of the L signal (a) and the R signal (b) change with respect to L + R (d).
[0028]
As described above, the L signal (a) and the R signal (b) shown in FIG. 2 output from the left electrode 1L and the right electrode 1R of the vibrator 1 are added by the adder circuit 2, and the L + R signal ( d) is given as a reference signal to the AGC circuit 4 to make the level constant. Further, after the phase of the reference signal is adjusted by the phase shift circuit 5, the oscillation circuit continues to oscillate by supplying the reference signal to the entire surface electrode 1C of the vibrator 1. The L + R signal output from the adder circuit 2 is formed into a rectangular wave by the rectangular wave forming circuit 6 and applied to the microprocessor 7 as a timing extraction signal.
[0029]
Here, as shown in FIG. 2, the Coriolis force (e) becomes maximum and minimum in the vicinity of the maximum and minimum points of the L + R signal (d) as the reference signal. This phase depends on the phase of the oscillation circuit and the phase shift caused by the detection resistor. The reference signal can be arbitrarily adjusted by the phase shift circuit 5. Note that the L signal (a) and the R signal (b) shown in FIG. 2 may be used independently as long as the reference signal has a stable phase and frequency. However, since the Coriolis force is superimposed on the L signal and the R signal, when a rectangular wave is used, it is not preferable because a phase shift from the differential occurs or the duty fluctuates.
[0030]
On the other hand, the differential amplifier circuit 3 outputs an LR signal that is the difference between the L signal and the R signal. The LR signal is given to the VT conversion circuit 8 and sampled and held by the sample and hold circuit 81. Here, as shown in FIG. 2 (f), the microprocessor 7 detects the rising edge which is the leading edge and the trailing edge which is the trailing edge of the reference signal formed in the rectangular wave, and is generated in the microprocessor 7. A count value of one cycle of the reference signal is calculated using a reference clock signal as shown in FIG. FIG. 2 (h) shows the timing for outputting a timing signal for sample-holding at a timing of, for example, a quarter of the reference signal.
[0031]
3A shows the reference signal, FIG. 3B shows the timing signal of the sample and hold, and the sample and hold circuit 81 shows the LR signal as shown in FIG. 3C based on this timing signal. Hold the sample. It is most efficient to sample and hold at the peak point of the Coriolis force, but it is not always necessary to sample and hold at the peak point, and sample holding may be performed near the peak point. This sample-and-hold voltage depends on the angular velocity and is integrated by the integration circuit 82, and the signal waveform linearly slopes downward with time as shown in FIG. The LR signal is sampled and held again based on the next timing signal.
[0032]
The integrated signal output from the integrating circuit 82 is supplied to the comparator 83, compared with a predetermined level, converted into a digital signal having a duty ratio corresponding to the Coriolis force shown in FIG. 3 (e), and the microprocessor as an angular velocity detection signal. 7 is output. The microprocessor 7 counts this digital signal with the reference clock and calculates the angular velocity.
[0033]
As shown in FIG. 4, the V-T conversion circuit 8 increases the time constant for the same angular velocity voltage change ΔE by increasing the time constant by reducing the leakage current of the integration circuit 83 to increase the hold time. The region ΔT1 becomes larger as ΔT2, and the resolution or sensitivity increases. Therefore, the time domain can be arbitrarily expanded by arbitrarily setting the time from a certain sample-hold timing to the next sample-hold timing.
[0034]
In this case, the hold time can exceed one period of the reference signal. This means that the conventional synchronous detection-integration-DC amplification is a voltage level amplification, but in this embodiment, it is an expansion at the time axis level. In the conventional example, the DC amplifier has an upper limit of the absolute amplification degree due to the power supply voltage, whereas the present invention basically means that an infinite amplification degree can be obtained.
[0035]
By expanding the time domain in this way, the LR signal in the meantime can be discarded. The driving frequency of the bimorph vibrator is several kHz to 100 kHz. In camera shake correction and car navigation systems, the upper limit of the angular velocity signal only needs to be a signal of 50 Hz or less. Since it may be discarded, this embodiment means that expansion of 1000 times or more is possible.
[0036]
FIG. 5 is a block diagram of another embodiment of the present invention. In the example shown in FIG. 1, the reference signal is converted into a rectangular wave and the sample / hold timing signal is generated by the software processing of the microprocessor 7, but the example shown in FIG. The reference signal is supplied to the timing signal generation circuit 9, and a timing signal for sample and hold is generated by a hardware configuration and supplied to the sample and hold circuit 81. That is, the timing signal generation circuit 9 implements the software processing of the microprocessor 7 shown in FIG. 1 in a hardware configuration, and includes a detection circuit that detects the leading edge and the trailing edge of the reference signal, and the leading edge to the trailing edge. And a logic circuit that outputs a timing signal based on the count value of the counter. As a result, the timing signal generation circuit 9 alone constitutes timing signal generation means.
[0037]
The digital output output from the comparator 83 may be input to the microprocessor 7 similar to that shown in FIG. 1 and subjected to software processing, or the digital signal is counted with a reference clock by a hardware circuit and an angular velocity signal is output. It may be.
[0038]
FIG. 6 is a circuit diagram showing a sample hold circuit used in still another embodiment of the present invention. In the embodiment shown in FIG. 1 and FIG. 5, the VT conversion circuit 8 samples and holds the sample voltage by the sample and hold circuit 81, and integrates the sample voltage by the integration circuit 82. By using the droop characteristic of the circuit, an integrating circuit is not required.
[0039]
For this reason, the sample and hold circuit 81 shown in FIG. 6 is conventionally known and includes an input buffer BA1, an output buffer BA2, transistors TR1 and TR2, FETs, a resistor R1, and a capacitor C. When a timing signal is applied from the microprocessor 7 to the emitter of the transistor TR1, the transistors TR1 and TR2 and the FET are sequentially turned on, and the signal input via the input buffer BA1 is stored in the capacitor C. When the FET is cut off, the charging voltage of the capacitor C leaks through the resistor R1 connected between the source and gate of the FET.
[0040]
7 and 8 are diagrams showing sample hold signals and droop characteristics by the sample hold circuit shown in FIG. Without the resistor R1 shown in FIG. 6, it is a very general sample-and-hold circuit, and converts the signal level at a slope determined by the leakage current i of the following equation.
[0041]
ΔV / ΔT = i (leak) / C
However, if the resistance R1 shown in FIG. 6 is provided to adjust the sensitivity amplification degree, the linear slope characteristic similar to that obtained by the integration circuit is provided by the droop characteristic as shown in FIG. 7C. Can do. The slope of the slope becomes gentler as the resistance R1 is increased. In that case, it is necessary to widen the interval between the timing pulses of the sample and hold.
[0042]
By comparing the sample and hold output shown in FIG. 7C with a predetermined level by the comparator 83 shown in FIG. 1, a digital signal that is the output of the comparator 83 can be outputted as shown in FIG.
[0043]
FIG. 8 is a waveform diagram when the vibrator 1 is shaken and the Coriolis force is moving. As the Coriolis force peak moves, the sample hold output also follows it as shown in FIG. The duty ratio of the digital output of the comparator 83 shown in FIG. This duty ratio becomes an angular velocity signal.
[0044]
9 and 10 are block diagrams showing a vibrating gyroscope according to still another embodiment of the present invention. The embodiment shown in FIG. 9 and FIG. 10 differs in that the first and second wavelengths of Coriolis force are sampled and held, and the respective sample and hold values are compared to estimate the null differential voltage. The analog differential voltage level analogized is D / A converted in the microprocessor 7, and the null voltage is removed by the offset adjustment circuit 10 as shown in FIG. 9, or the comparator 83 is turned on as shown in FIG. It controls the level.
[0045]
FIG. 11 is a waveform diagram showing sample hold points. As shown in FIG. 11, the rising position of the sample and hold signal is detected not at the same 90 degree phase (F1 ′) but at a point (F2) that is further shifted by 90 degrees after the 90 degree phase (F1) of the reference signal. . It is conceivable that the differential shape changes depending on the temperature or the like, but if the value is obtained, the null voltage can always be monitored and controlled from the following equation.
[0046]
F1 and F2 in FIG. 11 can be expressed by the following equations.
F1 = A {(sin ωt + α) + (B sin ωt)}
F2 = A (cos ωt + α)
A is the amplitude of the LR signal. When Coriolis force B is 0, it is expressed by the following equation.
[0047]
F1²+ F2²= A²
By calculating the above equation, the magnitude of the differential amplitude can be known, and the null voltage can be known from the value of A.
[0048]
The operation of FIG. 10 will be described below with reference to FIG.
In FIG. 11, point F1 is the Coriolis force maximum point, and point F2 is the Coriolis force zero point. The comparator output time T2 corresponding to the sampling at the point F2 is constant regardless of the presence of the Coriolis force.
[0049]
First, since the Coriolis force is zero immediately after the vibration gyro is activated, the initial values A (0) and α, which are the initial values of A and α of the differential inputs from T1 (0) and T2 (0) which are T1 and T2 immediately after activation. (0) is calculated (step 1).
[0050]
Next, based on the magnitude of T2 (0), the microprocessor 7 causes the duty ratio of T2 (0) to be 1: 1 through a D / A converter (included in the microprocessor 7). The level of the comparator 83 is adjusted, and T2 (t1) is measured again (step 2).
[0051]
In this state, T1 (t2) is measured. T1 (t2) varies with the Coriolis force. The D / A converter again adjusts the level of the comparator 83 so that this fluctuation is eliminated. That is, the Coriolis force is adjusted to zero. Then, T2 (t3) fluctuates around the duty ratio 1: 1 according to the fluctuation of the level of the comparator 83, the null voltage is canceled, and an output reflecting only the Coriolis force is obtained. A (t2) and α (t2) are calculated again from T1 (t2) and T2 (t1) at this time (step 3).
[0052]
The above (Step 2) and (Step 3) are intermittently performed, and the size of T2 is monitored at a certain interval. When the null voltage fluctuates due to a temperature change or the like, the comparator offset level is adjusted by an action (step 2) each time. At this time, it is not always necessary to obtain A and α. However, when T2 greatly fluctuates due to an abnormal input such as an external impact, and A and α take peculiar values, the past A and α By determining the magnitude of deviation from the value, the offset level adjustment can be skipped.
[0053]
9 also functions in substantially the same manner as in the case of controlling the comparator 83 only in that the D / A converter controls the offset adjustment circuit 10 instead of the comparator 83.
[0054]
In the conventional example, null voltages are output as an integrated signal for synchronous detection, and thus no means for correcting these null voltages has been provided. For this reason, it is possible that the angular velocity output and the null voltage cannot be distinguished by rotation at a constant angular velocity.
[0055]
On the other hand, in this embodiment, although the condition is that the difference between the Coriolis forces of two signals detected in succession is very small, the null voltage is controlled to always be zero by their midpoint potential. It is possible to cancel the influence of the temperature change of the null voltage.
[0056]
9 and 10 may be applied to the embodiment shown in FIG.
[0057]
Moreover, although the above-mentioned embodiment demonstrated the case where this invention was applied to the bimorph vibrator | oscillator, it is not restricted to this, The vibrator | oscillator which stuck the piezoelectric element to the metal square pillar or the triangular prism, or a cylindrical piezoelectric element The present invention can be applied to any piezoelectric vibration gyro that outputs an L / R signal such as a sound piece type vibrator using a device or a vibrator having a tuning fork structure and can take an excitation voltage or a sum voltage.
[0058]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0059]
【The invention's effect】
As described above, according to the present invention, a differential signal including a Coriolis force extracted from a vibrator by generating a reference signal based on the first and second signals output from the vibrator to excite the vibrator. An angular velocity detection signal can be output by sampling and holding the signal with a timing signal, expanding a minute voltage change of the sample and hold value on the time axis, and comparing the output with a predetermined level. Therefore, it is possible to eliminate the need for redundant circuits for digitization such as synchronous detection as in the prior art, and to reduce the cost.
[0060]
More preferably, the circuit configuration of the VT conversion means can be simplified by changing the slew rate of the sample and hold means as the VT conversion means and providing an amplification function.
[0061]
More preferably, the sample hold value is compared at a specific phase point of the first wavelength of the Coriolis force and a phase point different from that to estimate the null differential voltage, and the difference based on the estimated null differential voltage is obtained. By applying an offset to the motion signal or controlling the level of the comparison means, it is possible to perform control so that the null potential is always 0, and cancel the influence of the temperature change of the null voltage.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an angle detection circuit according to an embodiment of the present invention.
2 is a waveform diagram of each part of the angular velocity detection circuit shown in FIG. 1. FIG.
3 is a waveform diagram of each part of the angular velocity detection circuit shown in FIG. 1. FIG.
4 is a diagram showing a relationship between a time constant of an integrating circuit of the VT conversion circuit shown in FIG. 1 and resolution or sensitivity.
FIG. 5 is a block diagram showing an angular velocity detection circuit according to another embodiment of the present invention.
FIG. 6 is a circuit diagram of a sample and hold circuit used in still another embodiment of the present invention.
7 is a waveform diagram for explaining the operation of the sample and hold circuit shown in FIG. 6; FIG.
8 is a waveform diagram for explaining the operation of the sample and hold circuit shown in FIG. 6. FIG.
FIG. 9 is a block diagram showing an angular velocity detection circuit according to still another embodiment of the present invention, showing an example of removing a null voltage.
FIG. 10 is a block diagram showing an angular velocity detection circuit according to still another embodiment of the present invention, and shows an example of controlling the level of a comparator.
11 is a waveform diagram for explaining the operation of the embodiment shown in FIGS. 9 and 10. FIG.
FIG. 12 is an external perspective view of a bimorph vibrator as a background of the present invention and to which the present invention is applied.
FIG. 13 is a block diagram of a conventional angular velocity detection circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oscillator, 2 Adder circuit, 3 Differential amplifier circuit, 4 AGC circuit, 5 Phase shift circuit, 6 Rectangular wave formation circuit, 7 Microprocessor, 8 VT conversion circuit, 9 Timing signal generation circuit, 10 Null voltage adjustment Circuit, 81 Sample hold circuit, 82 Integration circuit, 83 Comparator.

Claims (6)

A vibratory gyroscope for detecting vibration caused by Coriolis force generated in the Y-axis direction when the vibrator is excited in the X-axis direction and rotated around the Z-axis,
Driving means for generating a reference signal based on the first and second signals output from the vibrator and exciting the vibrator;
Signal extraction means for extracting a differential signal including Coriolis force based on the first and second signals output from the vibrator;
Timing signal generating means for generating a timing signal for sample-holding the Coriolis force based on a reference signal output from the driving means, and generating the timing signal from the differential signal extracted by the signal extracting means A vibration gyro provided with voltage-time axis conversion means that samples and holds based on a timing signal generated from the means, expands a minute voltage change of the differential signal on the time axis, and outputs it as an angular velocity detection signal. The vibrator includes first and second electrodes that output the first and second signals, each having a slight amplitude and phase difference, and a whole surface electrode,
The driving means includes
Adding means for adding the first and second signals and outputting as a reference signal;
Level control means for making the level of the reference signal output from the adding means constant;
The vibration gyro according to claim 1, further comprising: a phase adjusting unit that adjusts a phase of the reference signal output from the level control unit and outputs the reference signal to the entire surface electrode. The voltage-time axis conversion means includes:
Sample and hold means for sample and holding the differential signal including Coriolis force based on the timing signal;
Integrating means for integrating the output signal of the sample and hold means;
The vibration gyro according to claim 1, further comprising: a comparison unit that compares the signal integrated by the integration unit at a predetermined level and outputs the signal after expanding the time axis. The voltage-time axis conversion means includes:
Sample and hold means for sampling the differential signal including Coriolis force based on the timing signal, and linearly reducing the peak value by droop characteristics;
The vibration gyro according to claim 1, further comprising: a comparison unit that compares a signal that decreases linearly by the sample and hold unit at a predetermined level and outputs the signal while expanding the signal on a time axis. Means for generating a timing signal for differentiating a sampling point by the sample hold means with a specific phase of Coriolis force and another phase at another wavelength;
4. A means for comparing a sample and hold value obtained by the sample and hold means to estimate a null differential voltage, and controlling a predetermined level of the comparison means based on the estimated null differential voltage. 4. The vibrating gyroscope according to 4. 6. The timing signal generation means detects a leading edge and a trailing edge of the reference signal, counts a clock signal, and outputs the timing signal at a predetermined count value. The vibrating gyroscope according to any one of the above.

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