JP3783893B2 - Piezoelectric vibration angular velocity meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibration type angular velocity meter that detects a rotational angular velocity.
[0002]
[Prior art]
Angular velocity meters are used for navigation systems for aircraft, ships, automobiles, etc. and their attitude control, and are used for camera shake and vibration detection of still cameras and video cameras. In many cases, it is required to detect an angular velocity. There exists a piezoelectric vibration type angular velocity meter as an angular velocity meter used for such a use. When an angular velocity is applied to a vibratory vibratory angular velocity meter, a Coriolis force is applied in the form of the outer product of the vibration direction and the angular velocity. It is an angular velocity meter that utilizes the phenomenon that occurs.
[0003]
In such a piezoelectric vibration angular velocity meter, a drive circuit for vibrating the vibrator and a detection circuit for detecting vibration generated by Coriolis force are provided, and these are combined to constitute an angular velocity meter. FIG. 3 shows the configuration of a conventional piezoelectric vibration angular velocity meter having such a drive and detection circuit. The detection circuit 4 constituting the piezoelectric vibration angular velocity meter is used for measuring an output signal from the detection electrode 103 of the vibrator 100 made of, for example, a rectangular parallelepiped piezoelectric body.
[0004]
The vibrator 100 is formed between a driving piezoelectric body 100-1 extending in the direction of the rotation center 1, a detecting piezoelectric body 100-2, and the two piezoelectric bodies 100-1 and 100-2. The ground electrode 104, the driving electrode 101 formed on the outer lower surface of the driving piezoelectric body 100-1, and the outer upper surface of the detecting piezoelectric body 100-2 are divided into two parts on the left and right with respect to the central axis 1. The detection electrodes 103L and 103R and the feedback electrode 102 formed by extending the center between the two detection electrodes in parallel with the two detection electrodes.
[0005]
The vibrator 100 is driven to drive between the driving electrode 101 formed on the outer lower surface of the driving piezoelectric body 100-1 and the feedback electrode 102 formed on the outer upper surface of the detecting piezoelectric body 100-2. The two detection electrodes 103L and 103R formed on the outer upper surface of the detection piezoelectric body 100-2 are connected to the inverting (−) input terminal and the non-inverting terminal of the differential circuit 200, respectively. Connected to the (+) input terminal, the differential circuit 200 is configured to detect an output difference from the two detection electrodes 103L and 103R.
[0006]
The output of the differential circuit 200 is input to the synchronous detection circuit 400 and detected. The output of the differential circuit 200 is theoretically 0 when the vibrator is not rotated, but when the vibrator 100 is rotated, the in-phase excitation signal is canceled out, and only the reverse-phase AC Coriolis signal is obtained. A synchronous switching signal is input from the phase adjustment circuit 500 to the synchronous detection circuit 400 so that detection can be performed in synchronization with this Coriolis signal phase. The phase adjustment circuit 500 is connected to the self-excited drive circuit 300 and is a circuit for generating a switching signal having the same phase as the Coriolis signal phase by shifting the phase of the excitation signal by approximately 90 degrees. The output of the synchronous detection circuit 400 is input to the smoothing circuit 600 and converted into a DC signal with little ripple.
[0007]
Such a conventional detection circuit 4 operates as follows when there is no rotation. By applying an alternating voltage (excitation signal) having a mechanical resonance frequency of the driving piezoelectric body 100-1 to the driving electrode 101 by the self-excited driving circuit 300, the vibrator 100 is driven in the excitation direction (the vertical direction of the vibrator 100). 4 is excited (bent) in a direction indicated by v in FIG. A signal having a mechanical resonance frequency associated with the vibration is detected from the detection electrodes 103R and 103L formed on the outer upper surface of the detection piezoelectric body 100-2. The detection signal at this time is detected by the detection electrode 103R. , 103L, the amplitude and phase are the same, and in principle, the output of the differential circuit 200 is zero. Therefore, the output of the synchronous detection circuit 400 is also 0, and the output of the smoothing circuit 600 is also 0.
[0008]
When the vibrator 100 rotates around the rotation center 1, a Coriolis force Fc is applied in a direction perpendicular to the excitation direction v of the vibrator 100 and the rotation center 1 of the vibrator 100 (left-right direction in the drawing of FIG. 1). The vibrator 100 vibrates with a slight shift in the left and right directions from the excitation direction when there is no rotation. This shifted amount is detected as a Coriolis signal from the two detection electrodes 103R and 103L.
[0009]
By the way, the two detection electrodes 103L and 103R are symmetrical with respect to the rotation center 1, and when one electrode side is extended, the other electrode side is contracted, and polarization charges which are opposite to each other due to the piezoelectric effect are applied to the detection electrodes 103L and 103R. Induced. Therefore, the Coriolis signals detected from the two left and right detection electrodes 103L and 103R are AC signals having the same amplitude and opposite mechanical resonance frequencies.
[0010]
In principle, one of the Coriolis signals from the two detection electrodes 103L and 103R has a 90-degree advance phase and the other has a 90-degree delay phase with respect to the excitation signal. Therefore, when the rotational angular velocity Ω is constant, the Coriolis signal is output from the differential circuit 200 with an amplitude value proportional to the rotational angular velocity with a phase difference of 90 degrees with respect to the excitation signal. By smoothing and measuring this output by the smoothing circuit 600, the rotational angular velocity Ω can be detected.
[0011]
In the detection circuit 4 of such a conventional piezoelectric vibration angular velocity meter, the output of the differential circuit 200 does not become zero at the time of non-rotation due to the external environment or the aging of the piezoelectric body forming the vibrator 100, and an error signal is generated. Even if it occurs, the Coriolis signal is output with a phase difference of about 90 degrees with respect to such an error signal, so that the differential circuit is detected by detecting in synchronization with the phase of the Coriolis signal. The error signal after output can be rectified so that the positive part and the negative part are always symmetrical. Therefore, this error signal is canceled out by the smoothing circuit 600, which has the advantage that the influence on the accurate rotational angular velocity measurement can be reduced.
[0012]
[Problems to be solved by the invention]
However, the amplitudes of the feedback signals that are fed back from the detection electrodes 103R and 103L due to variations in characteristics among the individual piezoelectric members forming the vibrator 100, changes with time, changes in capacitance accompanying changes in the external environment, and the like. Since the phases are not necessarily the same in reality, the error signals of the two at the time of no rotation may not have a phase difference of exactly 90 degrees from the Coriolis signal phase, and pass through the synchronous detection circuit 400 and the smoothing circuit 600. Even in this case, the error signal may not be completely canceled. For this reason, there is a case where a more accurate measurement of the rotational angular velocity Ω cannot be performed.
[0013]
The present invention has been made in view of such a problem, and is a piezoelectric vibration angular velocity meter that is not easily affected by variations in characteristics among individual vibrators, changes in the external environment, and the like, and that can detect a rotational angular velocity more accurately. Is intended to provide.
[0014]
[Means for Solving the Problems]
In order to achieve such an object, in the present invention, a rectangular parallelepiped piezoelectric body extending in the longitudinal direction and a pair of symmetrically disposed on the longitudinally extending surface of the piezoelectric body with respect to the longitudinal central axis. Drive electrodes and a pair of detection electrodes, a pair of excitation drive means for independently applying excitation drive signals to the pair of drive electrodes, and a center axis in the longitudinal direction based on a difference between detection signals by the pair of detection electrodes The piezoelectric vibration angular velocity meter includes an angular velocity detection unit configured to detect the rotational angular velocity and a phase adjustment unit that adjusts the phase of the excitation drive signal applied by at least one of the pair of drive units. In addition, the pair of excitation drive means supplies the excitation drive signal to one drive electrode of the pair of drive electrodes and obtains a feedback signal from the detection electrode corresponding to the one drive electrode; Including a second excitation drive means different from the first excitation drive means for providing an excitation drive signal to the other drive electrode of the first drive electrode and obtaining a feedback signal from the detection electrode corresponding to the other drive electrode. The adjusting means and the phase adjusting means adjust the amplitude and phase so that the difference between the detection signals from the pair of detection electrodes is substantially zero when the rotational angular velocity around the longitudinal central axis is zero .
[0015]
In the piezoelectric vibration angular velocity meter having such a configuration, the vibrations on the left and right sides of the piezoelectric body are unbalanced due to variations in characteristics between individual vibrators and changes in the external environment. If there is a difference in the detected signal, the amplitude and phase adjustment means are operated to automatically adjust the amplitude and phase so that the difference becomes zero.
[0016]
In addition, the piezoelectric body can be divided into two parts with a horizontal plane passing through the central axis in the longitudinal direction as a center line, and the piezoelectric body can be integrally joined with a ground electrode interposed therebetween. In this case, a pair of drive electrodes are provided on the outer surface of one of the two piezoelectric pairs divided into two to form a drive piezoelectric body, and a pair of detection electrodes are disposed on the outer surface of the other piezoelectric body. The piezoelectric body for detection is configured. In addition, the amplitude adjusting means and the phase adjusting means are considerably adjusted so that the piezoelectric body is not adjusted when the rotation of the angular acceleration around the central axis in the longitudinal direction is given and there is a difference between the detection signals from the left and right detection electrodes. It preferably has a slow response. As a result, the amplitude and phase are not adjusted when the vibrator is actually rotated to detect the angular velocity, but the angular velocity can be accurately detected, and the adjustment is performed while the vibrator is not rotating.
[0017]
Preferably, the first excitation drive means is an excitation drive / amplitude adjustment means also serving as an amplitude adjustment means, and the second excitation drive means is an excitation drive / phase adjustment means also serving as a phase adjustment means. In addition, it is preferable to have a differential unit that outputs a difference between detection signals from the pair of detection electrodes, and the output of the differential unit is input to the amplitude adjustment unit and the phase adjustment unit.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a configuration of a vibrator 10 used in a piezoelectric vibration angular velocity meter according to the present invention. This vibrator 10 has a rectangular parallelepiped driving piezoelectric body 10-1 extending in the direction of the central axis 1 in the longitudinal direction (note that the piezoelectric vibration angular velocity meter detects a rotational angular velocity component around this central axis) and a detection. The piezoelectric body 10-2, the ground electrode 14 formed between the two piezoelectric bodies 10-1 and 10-2, and the lower surface of the driving piezoelectric body 10-1 are symmetrical with respect to the central axis 1. A pair of left and right drive electrodes 11L, 11R (collectively referred to as drive electrodes 11) and a detection piezoelectric body 10-2 divided into left and right objects with respect to the central axis 1 are divided. A pair of left and right detection electrodes 13L and 13R (both electrodes are collectively referred to as detection electrode 13) is formed.
[0019]
A piezoelectric vibration angular velocity meter according to the present invention is configured by combining the drive detection circuit shown in FIG. This drive detection circuit first has a differential circuit 20 to which detection signals from the left and right detection electrodes 13L and 13R formed on the upper surface of the detection piezoelectric member 10-2 are input. At this time, the left detection electrode 13L is connected to the inverting (−) input terminal of the differential circuit 200, and the right detection electrode 13R is connected to the non-inverting (+) input terminal. The difference between the detection signals of the detection electrodes 13L and 13R is output.
[0020]
The output of the differential circuit 20 is input to the synchronous detection circuit 40 and detected. As will be described later, when the vibrator 10 does not rotate in the ideal state, the output of the differential circuit 20 is zero, and when the vibrator 10 rotates, the in-phase excitation signal is canceled and the anti-phase component Only AC Coriolis signal. A synchronous switching signal is input from the synchronous adjustment circuit 30 to the synchronous detection circuit 40 so that the detection can be performed in synchronization with the Coriolis signal phase. The synchronization adjusting circuit 30 is connected to a line connected to the right detection electrode 13R, and is a circuit for generating a switching signal having the same phase as the Coriolis signal phase by shifting the phase of the detection excitation signal by approximately 90 degrees. The output signal synchronously detected by the synchronous detection circuit 40 in this way is input to the smoothing circuit 50 and converted into a DC signal with little ripple.
[0021]
On the other hand, as shown in FIG. 2, an automatic amplitude adjustment circuit 60 and an automatic phase adjustment circuit 70 that also serve as an excitation drive circuit are connected to the drive electrodes 11L and 11R, respectively. Further, the detection signals from the detection electrodes 13L and 13R are fed back to both the circuits 60 and 70, respectively, and the detection electrodes 13L and 13R also function as feedback electrodes. In this way, a loop is formed between the drive electrode 11L on the left side of the vibrator 10 and the detection electrode 13L via the excitation drive / automatic amplitude adjustment circuit 60. From the excitation drive / automatic amplitude adjustment circuit 60, the loop is formed. When a drive signal having a frequency of the natural frequency of the vibrator 10 is applied to the drive electrode 11L, an excitation driving force having this frequency acts on the left side of the vibrator 10. Similarly, a loop is formed between the drive electrode 11R on the right side of the vibrator 10 and the detection electrode 13R via the excitation drive / automatic phase adjustment circuit 70, and vibration is generated from the excitation drive / automatic phase adjustment circuit 70. When a driving signal having a frequency of the natural frequency of the child 10 is applied to the driving electrode 11R, an excitation driving force having this frequency acts on the right side of the vibrator 10. As a result, the vibrator 10 vibrates at this frequency, and the piezoelectric power generated by this vibration is detected by the detection electrodes 13L and 13R and input to the circuits 60 and 70. Therefore, the vibrator 10 is self-excited at the above frequency. Vibrate.
[0022]
As described above, the detection signals of the detection electrodes 13L and 13R are input to the differential circuit 20 and the difference between the two signals is output from the differential circuit 20 when self-excited vibration is caused in this way. Is sent to both circuits 60 and 70. Here, the automatic amplitude adjusting circuit 60 receives this difference signal, detects the difference in amplitude in the detection signals of the left and right detection electrodes 13L, 13R, and the left drive electrode 11L so that the difference in amplitude is zero. The drive signal applied to is adjusted. Further, the automatic phase adjustment circuit 70 receives the difference signal, detects the phase difference in the detection signals of the left and right detection electrodes 13L and 13R, and applies the right drive electrode 11R to zero the phase difference. The drive signal to be adjusted is adjusted. As a result, the left and right imbalance of the vibrator 10 can be adjusted. The amplitude difference and the phase difference can be detected by a two-phase lock-in detection method or the like.
[0023]
The left and right imbalance adjustment based on the automatic adjustment of the amplitude and phase by both the circuits 60 and 70 is caused by variation among the individual vibrators 10, changes with time, changes in capacitance accompanying changes in the external environment, and the like. This is to adjust the unbalance. For this reason, it is necessary to perform the detection without adding the angular velocity to be detected, and the responsiveness of the automatic amplitude adjusting circuit 60 and the automatic phase adjusting circuit 70 is made dull. Specifically, automatic adjustment is performed by both circuits 60 and 70 for post-differential amplitude fluctuations at a frequency of 0.1 Hz or less. Adjustments are not allowed.
[0024]
The operation of the piezoelectric vibration angular velocity meter configured as described above will be described below. First, the operation in an ideal state where there is no left / right imbalance of the vibrator will be described. As described above, the rotational angular velocity around the central axis 1 of the vibrator 10 in a state where the vibrator 10 is in self-excited vibration by the drive from the excitation drive / automatic amplitude adjustment circuit 60 and the excitation drive / automatic phase adjustment circuit 70. When is zero (no rotation), in the ideal state, the detection signals from the left and right detection electrodes 13L and 13R have the same amplitude and the same phase. Therefore, the output of the differential circuit 20 is 0, and the output that has passed through the synchronous detection circuit 40 and the smoothing circuit 50 is 0.
[0025]
In a state where the vibrator 10 is vibrating by self-excited vibration, when an angular velocity is applied to the vibrator 10 around the central axis 1 (when rotating), the vibrator 10 is coriolis in the lateral direction (a direction perpendicular to the self-excited vibration direction). Since the force is received, the vibration direction slightly changes in the horizontal direction from the vibration at no rotation. When such a Coriolis force is applied, the signals from the left and right detection electrodes 13L and 13R are compared with the non-rotation signals, one of which is a phase that is 90 degrees advanced and the other is a signal that is a phase that is 90 degrees delayed ( That is, signals having the same amplitude and opposite phases are added. For this reason, in addition to the non-rotating signal, the differential circuit 20 receives signals having a phase difference of 90 degrees (signal generated by Coriolis force) from the left and right detection electrodes 13L and 13R. The Here, since the vibration at the time of non-rotation has the same amplitude and the same phase, the operation circuit 20 cancels out the signals. However, since the signals added by the Coriolis force are in the opposite phase, they are added to each other in the differential circuit 20 and output. The That is, only the signal corresponding to the Coriolis force is output from the differential circuit 20, and the angular velocity around the central axis 1 of the transducer 10 can be detected by passing this output through the synchronous detection circuit 40 and the smoothing circuit 50. it can.
[0026]
Next, a case in which the state is not an ideal state, that is, a case in which variation among individual vibrators, a change in capacitance due to a change with time and a change in external environment, or the like occurs will be described. In the conventional self-excited circuit, when the vibration state changes due to changes in the external environment or changes over time, that is, the signals from the left and right detection electrodes 13L and 13R have different amplitudes and phases when there is no rotation in the self-excited state. When such an imbalance occurs, the output of the differential circuit 20 does not become zero. In addition, since the phase of the output does not become 90 degrees with respect to the excitation signal, the differential residual is synchronously detected and the smoothed output does not become 0, thereby causing a detection error.
[0027]
For this reason, in this circuit, the output of the differential circuit 20 during non-rotation is input to the automatic amplitude adjustment circuit 60 and the automatic phase adjustment circuit 70 as a monitor signal. The automatic amplitude adjustment circuit 60 automatically changes the amplitude of the applied voltage for driving the vibrator 10 so that the difference in amplitude becomes zero based on the monitor signal. At the same time, the automatic phase adjustment circuit 70 automatically changes the phase of the applied voltage for driving the vibrator so that the phase difference becomes 0 based on the monitor signal. As a result, even when the state of the vibrator changes due to changes in the external environment or changes over time, the amplitude and phase of the two drive voltages applied to drive the vibrator are automatically changed to make no rotation. In some cases, the output of the differential amplifier is always set to zero. Therefore, since the output that has passed through the synchronous detection circuit 40 and the smoothing circuit 50 is always zero when there is no rotation, the detection error can be reduced.
[0028]
At this time, the responsiveness of each of the automatic amplitude adjusting circuit 60 and the automatic phase adjusting circuit 70 is dulled as described above so that the above correction is not performed until the output of the differential amplifier 20 changes during rotation. ing. That is, when the output of the differential amplifier 20 changes slowly, such as a change with time, the above two adjustment circuits are activated and are not activated for a rapid change. As a result, the two adjustment circuits do not operate for fast changes in angular velocity that alternately repeat clockwise and counterclockwise rotation around the rotation axis, and cancel the signal due to the angular velocity that should be detected. There is no.
[0029]
Further, since the output of the differential circuit 20 always has an accurate phase difference of 90 degrees with respect to the excitation signal at the time of rotation, for example, the synchronous detection switching signal is sent from the synchronous adjustment circuit 30 to the timing of the excitation signal and the 90-degree phase delay. The Coriolis signal can be extracted without reducing the efficiency even if there is a change in the external environment or a change with time. Further, since no residual differential stress is generated, errors can be reduced, and highly accurate angular velocity detection is possible.
[0030]
【The invention's effect】
As described above, according to the present invention, a pair of detection electrodes can be used at the time of non-rotation due to unbalanced vibrations on the left and right sides of the piezoelectric body due to variations in characteristics between vibrators and changes in the external environment. When there is a difference between the signals detected by the above, the amplitude adjustment means and the phase adjustment means are activated and the amplitude and phase are automatically adjusted so that the difference is zero. Thus, it is possible to always detect the rotational angular velocity with high accuracy without being affected by variations in the characteristics and changes in the external environment.
[0031]
It should be noted that the amplitude adjusting means and the phase adjusting means are considerably adjusted so that the piezoelectric body is not adjusted when there is a difference between the detection signals from the left and right detection electrodes due to the rotation of the angular acceleration around the central axis in the longitudinal direction. It is preferable to have a slow response, whereby the amplitude and phase are not adjusted when the vibrator actually rotates to detect angular velocity, and can be adjusted without affecting the angular velocity detection accuracy.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a vibrator constituting a piezoelectric vibration angular velocity meter of the present invention.
FIG. 2 is a block diagram showing a configuration of a piezoelectric vibration angular velocity meter of the present invention.
FIG. 3 is a block diagram showing a configuration of a conventional piezoelectric vibration angular velocity meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Vibrator 11 Drive electrode 13 Detection electrode 14 Ground electrode 20 Differential circuit 40 Synchronous detection circuit 50 Smoothing circuit 60 Automatic amplitude adjustment circuit 70 Automatic phase adjustment circuit

Claims (5)

A rectangular parallelepiped piezoelectric body extending in the longitudinal direction;
A pair of drive electrodes and the pair of detection electrodes which are disposed symmetrically respectively with respect to the longitudinal central axis on the surface extending in the longitudinal direction of the piezoelectric,
A pair of excitation drive means for independently applying an excitation drive signal to the pair of drive electrodes;
Angular velocity detection means configured to detect a rotational angular velocity about the central axis in the longitudinal direction based on a difference between detection signals by the pair of detection electrodes;
Amplitude adjusting means for adjusting the amplitude of the excitation drive signal applied by at least one of the pair of drive means;
Phase adjustment means for adjusting the phase of the excitation drive signal applied by at least one of the pair of drive means,
The pair of excitation drive means provides the excitation drive signal to one drive electrode of the pair of drive electrodes and obtains a feedback signal from the detection electrode corresponding to the one drive electrode; Second excitation drive means different from the first excitation drive means for providing the excitation drive signal to the other drive electrode of the pair of drive electrodes and obtaining a feedback signal from the detection electrode corresponding to the other drive electrode. Including
Said amplitude adjusting means and said phase adjusting means adjusts the amplitude and the phase so that the rotation angular velocity around the longitudinal central axis is substantially zero difference detection signal by said pair of detection electrodes when the zero A piezoelectric vibration angular velocity meter characterized by that.   The piezoelectric body is divided into upper and lower parts centering on a horizontal plane passing through the central axis in the longitudinal direction, and is integrally joined with a ground electrode interposed therebetween, and either one of the two piezoelectric parts divided in this way The pair of drive electrodes are disposed on the outer surface of the first piezoelectric element to form a driving piezoelectric body, and the pair of detection electrodes are disposed on the outer surface of the other piezoelectric body to constitute the piezoelectric detecting element. The piezoelectric vibration angular velocity meter according to claim 1, wherein   The amplitude adjusting unit and the phase adjusting unit are configured such that when the piezoelectric body is given a rotation with non-zero acceleration around the longitudinal central axis and a difference between detection signals by the pair of detection electrodes is generated, 3. The piezoelectric vibration angular velocity meter according to claim 1, wherein the piezoelectric vibration angular velocity meter has a slow response so as not to adjust the phase. The first excitation drive means is an excitation drive / amplitude adjustment means that also serves as the amplitude adjustment means, and the second excitation drive means is an excitation drive / phase adjustment means that also serves as the phase adjustment means. The piezoelectric vibration angular velocity meter according to any one of claims 1 to 3. 2. A differential means for outputting a difference between detection signals of the pair of detection electrodes, and an output of the differential means is inputted to the amplitude adjusting means and the phase adjusting means. The piezoelectric vibration angular velocity meter according to any one of claims 4 to 5.

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