JPH1151657A - Excitation circuit for piezo-electric vibration type angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensitivity and stability as angular sensor by a method wherein a feedback loop of an oscillation circuit including a piezo-electric vibrator is arranged to drive an excitation side leg part by a signal via a voltage conversion circuit, a signal adjusting circuit and an amplification circuit and an amplification factor of the amplification circuit is controlled by an automatic oscillation control circuit. SOLUTION: At an excitation leg part, a signal electric charge generated by a distortion of a piezo-electric vibrator is very weak, hence, is converted to a voltage signal by a voltage conversion circuit 1 to allow efficiently detecting of the signal electric charge and inputted into a signal adjusting circuit 2. The voltage signal adjusted is inputted into an amplification circuit 3. The voltage signal is amplified so that a gain of a feedback loop of an oscillation circuit including the piezo-electric vibrator may become at least 1 in the resonance frequency at a vibration mode necessary for operation as angular velocity sensor to drive the piezo-electric vibrator. In addition, the amplification factor of the amplification circuit 3 is automatically controlled by an automatic amplitude control circuit 4 so that the vibration of the piezo-electric vibrator becomes sinusoidal with a fixed amplitude thereby enabling accurate detection of a vibration attributed to a Coriolis force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation circuit (excitation circuit) for reliably and stably exciting an excitation leg of a piezoelectric vibrator in an excitation circuit of a piezoelectric vibration type angular velocity sensor.

[0002]

2. Description of the Related Art In order to oscillate a piezoelectric vibrator, it is usually necessary that a phase and an amplification factor satisfy certain conditions. As a condition, it is necessary that the phase shift θ when the circuit loops through the feedback loop of the oscillation circuit including the piezoelectric vibrator is 0 ° or 360 °. On the other hand, regarding the amplification factor, the loop gain of the feedback loop of the oscillation circuit including the piezoelectric vibrator needs to be 1 or more. In addition, it is sufficient that only the natural frequency of the piezoelectric vibrator oscillates reliably, and the other frequencies are rather regarded as unnecessary waves (spurious).

[0003]

However, since the piezoelectric vibrator used in the piezoelectric vibration type angular velocity sensor has a feature necessary for detecting the angular velocity, the piezoelectric vibrator can be operated in a desired vibration mode. There is a problem that it is difficult to reliably and stably oscillate.

That is, the piezoelectric vibration type angular velocity sensor applies an AC voltage to at least one of the two legs to excite (oscillate), and the vibration due to the Coriolis force is generated from the other leg of the piezoelectric vibrator. The piezoelectric vibrator operates to detect. In other words, in a space having three axes of X, Y, and Z, while rotating the piezoelectric vibrator about the Y axis while vibrating the piezoelectric vibrator in parallel with the X axis, the Coriolis in the Z axis direction perpendicular to the X axis becomes A force is generated, and has a vibration component having a magnitude proportional to the Coriolis force in the Z-axis direction. Therefore, the magnitude of the Coriolis force can be detected by measuring the amount of electric charge generated by the vibration component in the Z-axis direction or detecting the amount of displacement of the vibration.

For this reason, the oscillation of one oscillating leg is transmitted to the other leg, and the leg is reliably and stably vibrated, and has a vibration component having a magnitude proportional to a weak Coriolis force. And this vibration component must be detected.
For this reason, the piezoelectric vibrator of the piezoelectric vibration type angular velocity sensor has extremely weak resonance characteristics, so the phase shift and impedance change at the resonance frequency are small, and many vibration modes other than the vibration mode for detecting the angular velocity are strongly generated. Therefore, it is difficult for the piezoelectric vibrator of the piezoelectric vibration type angular velocity sensor to reliably and stably oscillate in a target vibration mode.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a piezoelectric vibrator used in a piezoelectric vibrating angular velocity sensor, which comprises: This is for satisfying certain conditions (phase and amplification factor) for oscillating the piezoelectric vibrator and for selecting a vibration mode. In order to oscillate the excitation leg of the piezoelectric vibration type angular velocity sensor, the signal leg of the excitation leg is converted to the excitation leg by a signal passed through an independent voltage conversion circuit, signal adjustment circuit, and amplification circuit. By driving, a feedback loop of the oscillation circuit including the piezoelectric vibrator is formed. Further, the amplification factor of the amplifier circuit is controlled by the automatic amplitude control circuit. The problem can be solved by securing the phase shift and the amplification factor necessary for the oscillation of the excitation leg by such means and obtaining the desired vibration mode and vibration frequency.

[0007]

BACKGROUND ART A piezoelectric vibration type angular velocity sensor applies an AC voltage to at least one of two legs to excite (oscillate), and detects vibration due to Coriolis force from the other leg of the piezoelectric vibrator. The piezoelectric vibrator operates as follows. In other words, in a space having three axes of X, Y, and Z, when the piezoelectric vibrator is rotated about the Y axis while vibrating in parallel with the X axis, the Coriolis force is generated in the Z axis direction perpendicular to the X axis. Occurs
It has a vibration component in the Z-axis direction having a magnitude proportional to the Coriolis force. Therefore, the magnitude of the Coriolis force can be detected by measuring the amount of electric charge generated by the vibration component in the Z-axis direction or detecting the amount of displacement of the vibration.

[0008] Since the Coriolis force is determined in proportion to the magnitude of the angular velocity using the above-described operation principle, the amount of bending displacement due to the Coriolis force is indirectly determined by the piezoelectric effect of the piezoelectric element, the change in capacitance, and the like. If measured directly, the oscillator Y
The magnitude of the rotational angular velocity acting around the axial direction can be determined. By utilizing these features, a vibrating vibrator is mounted on a vehicle or aircraft as an angular velocity detecting element, and its running or flight trajectory is recorded, and yaw rate generated during turning is detected. I have. In addition, this angular velocity detection element is mounted on a robot,
It can also be applied to control its posture.

However, as described above, the angular velocity sensor uses the vibration of the leg on the excitation side to vibrate the leg on the detection side, and detects the magnitude of the angular velocity by the Coriolis force acting on the leg on the detection side. Therefore, unless the leg on the excitation side is reliably vibrated, the detection sensitivity of the angular velocity on the leg on the detection side is reduced. In the present invention, in order to surely vibrate the leg on the excitation side, the signal charge on the leg on the excitation side is driven by the signal via the independent voltage conversion circuit, the signal adjustment circuit and the amplifier circuit. Thus, the problem can be solved by forming a feedback loop of an oscillation circuit including a piezoelectric vibrator and controlling the amplification factor of the amplifier circuit by an automatic amplitude control circuit.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same reference numeral indicates the same object. FIG. 1 shows a block diagram of an excitation circuit 7 for oscillating the excitation leg of the angular velocity sensor of the present invention.

In an excitation circuit 7 for oscillating the excitation leg of the piezoelectric vibrator, a signal charge generated in the excitation leg is generated by an excitation signal passing through a voltage conversion circuit 1, a signal adjustment circuit 2, and an amplification circuit 3, and the piezoelectric vibration And an excitation circuit 7 for automatically controlling the amplitude of the excitation signal by feeding back a control signal generated by the automatic amplitude control circuit 4 from a signal from the amplification circuit 3 to the amplification circuit 3.

In short, the signal charges generated by the distortion of the piezoelectric vibrator in the excitation leg are extremely weak, and are converted into voltage signals by the independent voltage conversion circuit 1 so that the signal charges can be detected efficiently. This voltage signal is input to the signal adjustment circuit 2. Insufficient piezoelectric vibrator so that the signal adjustment circuit 2 causes a phase shift of 0 degree or 360 degrees when the feedback loop of the oscillation circuit including the piezoelectric vibrator circulates, so that the piezoelectric vibrator oscillates. The oscillation circuit compensates for the phase shift. In addition, by controlling the frequency characteristics of the phase shift and the gain, the oscillation conditions are not satisfied except for the oscillation mode necessary for operating as an angular velocity sensor, and oscillation in other unnecessary oscillation modes or self-excitation Oscillation is prevented.

The voltage signal adjusted by the signal adjustment circuit 2 is input to the amplification circuit 3. Amplifying circuit 3 amplifies the voltage signal so that a loop gain of a feedback loop of an oscillation circuit including a piezoelectric vibrator becomes 1 or more at a resonance frequency in a vibration mode necessary to operate as an angular velocity sensor, Drive the piezoelectric vibrator. Further, the amplification factor of the amplifier circuit 3 is automatically controlled by the automatic amplitude control circuit 4 so that the vibration of the piezoelectric vibrator becomes a sinusoidal vibration having a constant amplitude.

FIGS. 2 to 4 are block diagrams showing another embodiment of the present invention. The basic circuit configuration is the same as that of FIG. 1, but in FIG. 2, a drive circuit 5 is inserted between the amplifier circuit 3 and the piezoelectric vibrator. In short, by adding the drive circuit 5 between the amplifier circuit 3 and the piezoelectric vibrator, the amplifier circuit 5 does not need to drive the piezoelectric vibrator, and the capacity of the amplifier circuit 3 can be obtained. Further, by adding the independent driving circuit 5, a larger driving force can be obtained, and the oscillation of the piezoelectric vibrator can be more stabilized.

In FIG. 3, a filter 6 for cutting a DC component is inserted between the signal adjustment circuit 2 and the amplification circuit 3. In short, since the signal output from the voltage conversion circuit 1 is originally an AC component signal, the DC component signal is an unnecessary signal, which hinders amplification in the amplifier circuit 3. Since the excitation signal is very small and sensitive, the presence of a DC component in the AC component signal is an obstacle to obtaining a required amplification factor.

FIG. 4 shows a combination of the circuit configurations of FIGS. 2 and 3 described above. A filter 6 for cutting a direct current component is inserted between the signal adjustment circuit 2 and the amplification circuit 3 so that the amplification circuit 3 This is a circuit configuration in which a drive circuit 5 is inserted between piezoelectric vibrators. In short, the circuit configuration is such that the DC component of the signal from the voltage conversion circuit 1 is removed, the signal is amplified by the amplifier circuit 3, and the signal is driven by the drive circuit 5 to stably drive the piezoelectric vibrator. is there.

[0017]

According to the present invention, by vibrating the piezoelectric vibrator reliably, the vibration due to the Coriolis force proportional to the angular velocity, which is the detection signal, can be reliably detected. With this excitation circuit, the piezoelectric vibrator used in the angular velocity sensor can be designed so that the angular velocity detection performance is more important than the ease of oscillation, greatly improving the performance such as sensitivity and stability of the angular velocity sensor. Can be. Further, the yield of the angular velocity sensor can be significantly improved, and the manufacturing cost of the piezoelectric vibrator can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an oscillation circuit of a piezoelectric vibration type angular velocity sensor according to the present invention.

FIG. 2 is a block diagram of an excitation circuit according to another embodiment of the present invention, in which a drive circuit is inserted between an amplification circuit and a piezoelectric vibrator.

FIG. 3 is a block diagram of an excitation circuit according to another embodiment of the present invention in which a filter for cutting a DC component is inserted between a signal adjustment circuit and an amplification circuit.

FIG. 4 shows another embodiment of the present invention, in which a filter for cutting a DC component is inserted between a signal adjustment circuit and an amplification circuit;
It is a block of an excitation circuit in which a drive circuit is inserted between an amplifier circuit and a piezoelectric vibrator.

[Description of Signs] 1 Voltage conversion circuit 2 Signal adjustment circuit 3 Amplification circuit 4 Automatic amplitude control circuit 5 Drive circuit 6 Filter 7 Excitation circuit

Claims (4)

[Claims] 1. A piezoelectric vibrator having at least two legs, an AC voltage is applied to one leg to excite the piezoelectric vibrator, and the other piezoelectric vibrator is rotated by rotating the piezoelectric vibrator. In the excitation circuit of the piezoelectric vibration type angular velocity sensor which detects the angular velocity as the Coriolis force from the legs of the piezoelectric vibrating type angular velocity sensor, the signal charges of the excitation side legs are driven by the excitation signal via the voltage conversion circuit, the signal adjustment circuit, and the amplification circuit. And exciting the piezoelectric vibrator by controlling the amplification factor with a control signal fed back from the automatic amplitude control circuit to the amplifier circuit from a signal from the amplifier circuit, thereby exciting the piezoelectric vibrator. circuit. 2. The excitation circuit according to claim 1, wherein a driving circuit is inserted between the amplification circuit and the piezoelectric vibrator in the excitation circuit of the piezoelectric vibration type angular velocity sensor. . 3. The piezoelectric vibration type angular velocity according to claim 1, wherein a filter for cutting a direct current component is inserted between the signal adjustment circuit and the amplification circuit in the excitation circuit of the piezoelectric vibration type angular velocity sensor. Excitation circuit of the sensor. 4. An excitation circuit of the piezoelectric vibration type angular velocity sensor, wherein the filter for cutting a DC component is inserted between the signal adjustment circuit and the amplification circuit, and the filter is inserted between the amplification circuit and the piezoelectric vibrator. 2. The excitation circuit according to claim 1, further comprising a drive circuit.