JP2536261B2 - Detection circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection circuit, and more particularly to a detection circuit for measuring the output of a vibrating gyro having, for example, a triangular prism shape.

(Prior Art) FIG. 5 is a block diagram showing an example of a conventional detection circuit which is the background of the present invention. The detection circuit 1 is used to measure the output of a vibrating gyro 2 having a triangular prism shape, for example.

Two piezoelectric elements 3 of the vibration gyro 2 and another piezoelectric element 4
An excitation signal generation circuit 5 is connected between the and. In this case, the signal generating circuit 5 is connected to the two piezoelectric elements 3 of the vibrating gyro 2 via the resistors 6, respectively. Further, the outputs of these piezoelectric elements 3 are input to the differential circuit 7. The output of the differential circuit 7 is detected by the synchronous detection circuit 8 in synchronization with the frequency of the excitation signal. Then, the detected signal is amplified by the DC amplifier circuit 9.

The vibration gyro 2 is flexibly vibrated by the excitation signal generation circuit 5 in a direction orthogonal to the main surface of the other piezoelectric element 4. At this time, the output from the differential circuit 7 becomes 0 by adjusting the signals generated from the difference in electrostatic capacitance between the two piezoelectric elements 3 to be the same.

When the vibrating gyro 2 rotates about its axis,
Coriolis force acts in a direction orthogonal to the vibration direction of the vibration gyro 2. Therefore, the vibration direction of the vibration gyro 2 is deviated from the vibration direction when there is no rotation. Therefore, a difference in output occurs between the two piezoelectric elements 3, and an output is obtained from the differential circuit 7. This output has a value according to the magnitude of the rotational angular velocity. Therefore, the rotational angular velocity applied to the vibration gyro 2 can be measured by synchronously detecting this output and measuring the DC-amplified output.

(Problems to be Solved by the Invention) However, the capacitance of the piezoelectric element is changed due to a change in the difference value due to the fact that the respective values themselves change from the initial value due to the ambient temperature and the change over time, and the change degree thereof is different, The output comes out from the differential circuit even when there is no rotation. This output causes a measurement error, which makes it impossible to accurately measure the rotational angular velocity.

It is possible to attach a filter or the like to the detection circuit in order to remove such an error due to the variation of the electrostatic capacitance, but if the filter or the like is attached, the circuit becomes complicated.

Therefore, a main object of the present invention is to provide a detection circuit which is a simple circuit and is less likely to cause a measurement error due to a change in ambient temperature or a change over time.

(Means for Solving the Problem) The present invention relates to a detection circuit for measuring the output of a vibration gyro including a vibrating body having a polygonal prism shape and a piezoelectric element formed on at least two non-parallel side surfaces of the vibrating body. Therefore, an excitation signal generation circuit for applying a main signal having an excitation frequency for exciting the vibrating body to the two piezoelectric elements and a sub-signal having a frequency n times or 1 / n times the frequency of the main signal are provided. A sub-signal transmission circuit for applying to the two piezoelectric elements,
A differential circuit for detecting the difference between the outputs from the two piezoelectric elements, a first detection circuit for detecting the output from the differential circuit in synchronization with the main signal, and a difference for synchronizing with the sub signal. A detection circuit including a second detection circuit for detecting the output from the driving circuit, and a combining circuit for combining the output from the first synchronous detection circuit and the output from the second synchronous detection circuit Is.

(Operation) When the vibrating body is flexurally vibrated by the main signal and the rotational angular velocity is applied to the vibrating body, an output including an output according to the rotational angular velocity and an error generated due to a difference in electrostatic capacitance of the piezoelectric element,
It is output from the differential circuit at the frequency of the main signal. Further, an output corresponding to an error caused by the difference in electrostatic capacitance of the piezoelectric element is output from the differential circuit at the frequency of the sub signal.

These mixed outputs are detected in synchronization with the frequency of the main signal, so that the sub signal component is canceled. Further, the mixed output is detected in synchronization with the frequency of the sub signal, so that the main signal component is canceled. And
The detected main signal component and sub-signal component are combined.

(Effect of the Invention) According to the present invention, by synthesizing the detected main signal component and the detected sub-signal component, the error caused by the difference in the capacitance of the piezoelectric element can be removed. Therefore, only the output corresponding to the rotational angular velocity can be obtained, and the rotational angular velocity can be accurately measured.

Further, according to the present invention, it is not necessary to attach a filter or the like in order to remove the error caused by the difference in the electrostatic capacitance of the piezoelectric element, and the circuit can be simplified.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. The detection circuit 10 is used to detect the output of the vibration gyro 12, for example. Vibration gyro 12 is 2A
As shown in FIG. 2 and FIG. 2B, for example, a vibrating body 14 having a regular triangular prism shape is included. The vibrating body 14 is formed of a material that generally causes mechanical vibration, such as elinvar, iron-nickel alloy, quartz, glass, crystal, and ceramic.

Piezoelectric elements 16a, 16b, and 16c are formed in the center of the three side surfaces of the vibrating body 14, respectively. Piezoelectric element 16
a includes a piezoelectric layer 18a made of, for example, porcelain, and the piezoelectric layer 18a
Electrodes 20a and 22a are formed on both main surfaces of a, respectively. The electrodes 20a and 22a are made of, for example, gold,
It is formed of an electrode material such as silver, aluminum, nickel, or a copper-nickel alloy (monel metal) by a thin film technique such as sputtering or vapor deposition or a printing technique depending on the material. Similarly, other piezoelectric elements 16b, 16c
Also includes piezoelectric layers 18b, 18c made of, for example, porcelain, and the electrodes 20b, 2 are formed on both main surfaces of the piezoelectric layers 18b, 18c.
2b and electrodes 20c, 22c are formed. Then, one of the electrodes 20a to 20c of the piezoelectric elements 16a to 16c is bonded to the vibrating body 14 with, for example, a conductive adhesive.

Further, the vicinities 14 near the node points are supported by support members 24 and 26 made of, for example, metal wires. The support members 24 and 26 are fixed to the vibrating body 14 near the node points by welding, for example.

A resistor 28 is connected to the piezoelectric element 16a, and a resistor 30 is connected to the piezoelectric element 16b. An oscillator circuit output source 34 is connected to these resistors 28 and 30 via a phase correction circuit 32. The phase correction circuit 32 and the oscillation circuit output source 34 form an excitation signal generation circuit 36. Furthermore, in another piezoelectric element 16c,
The oscillator circuit output source 34 is connected. Therefore, the piezoelectric element
When a main signal having the resonance frequency of the vibrating body 14 is applied between the piezoelectric elements 16c and 16a and 16b, the vibrating body 14 flexurally vibrates in a direction orthogonal to the main surface of the piezoelectric element 16c.

In addition, the piezoelectric elements 16a and 16b include a sub-signal transmission circuit.
38 is connected. In this embodiment, the sub-signal sending circuit 38 is connected to the oscillation circuit output source 34, and the sub-signal is sent out by dividing the frequency of the main signal. This sub signal is applied to the piezoelectric elements 16a and 16b.

Further, the two piezoelectric elements 16a and 16b are connected to the input side of the differential circuit 40. The output side of the differential circuit 40 is connected to the input side of the first synchronous detection circuit 42, and the output side thereof is connected to the DC amplification circuit 44. The first synchronous detection circuit 42 detects the output of the differential circuit 40 in synchronization with the main signal by the signal from the oscillation circuit output source 34.

Further, the output side of the differential circuit 40 is a second synchronous detection circuit.
It is connected to the input side of 46 and its output side is connected to the DC amplification circuit 44. The second synchronous detection circuit 46 receives a signal from the sub-signal sending circuit 38 and synchronizes with the sub-signal.
40 outputs are detected.

A main signal and a sub signal are applied to the piezoelectric elements 16a and 16b of the vibration gyro 12. At this time, the vibrating body 14 is flexibly vibrated by the main signal having the resonance frequency. Here, when a rotational angular velocity is applied to the vibrating gyro 12, Coriolis force acts to change the vibrating direction, and a difference occurs between the voltage generated in the piezoelectric element 16a and the voltage generated in the piezoelectric element 16b. Therefore, the differential circuit 40 can obtain an output at the same frequency as the main signal according to the rotational angular velocity. At this time, if there is a difference in capacitance between the piezoelectric elements 16a and 16b, the output from the differential circuit 40 also includes the output resulting from the difference in these capacitances.

Further, since the sub-signal does not have the resonance frequency of the vibrating body 14, an output corresponding to the Coriolis force cannot be obtained from the differential circuit 40, and the capacitances of the piezoelectric elements 16a and 16b have the same frequency as the sub-signal. The output resulting from the difference between That is, from the differential circuit 40, the output of the same frequency as the main signal and the output of the same frequency as the sub signal are obtained in a mixed form.

The output from the differential circuit 40 is the first synchronous detection circuit 42,
It is detected in synchronization with the main signal. In this case, as shown in FIG. 3, for example, the main signal is detected in synchronization with the positive portion. At this time, the sub-signals are canceled and only the main signal is detected. This main signal includes an output according to the rotational angular velocity and an output generated from the difference in electrostatic capacitance between the piezoelectric elements 16a and 16b.

Further, in the second synchronous detection circuit 46, the output from the differential circuit 40 is detected in synchronization with the sub signal. In this case, as shown in FIG. 4, for example, the sub signal is detected in synchronization with the positive portion. At this time, the main signal is canceled and only the sub signal is detected. This sub-signal contains the piezoelectric elements 16a, 16b.
Only the output resulting from the difference in the capacitance of is included.

The output from the first synchronous detection circuit 42 and the output from the second synchronous detection circuit 46 are combined by a DC amplification circuit 44 including a combination circuit and DC-amplified. At this time, the two outputs are combined so as to cancel the output generated from the difference in electrostatic capacitance between the piezoelectric element 16a and the piezoelectric element 16a. By doing so, only the output according to the rotational angular velocity is obtained from the DC amplification circuit 44. Therefore, this DC amplifier circuit
By measuring the output from 44, the rotational angular velocity applied to the vibration gyro 12 can be accurately measured.

In other words, if this detection circuit 10 is used, the measurement error does not increase even if the capacitances of the piezoelectric elements 16a and 16b change due to changes in temperature, changes with time, and the like. Therefore, the accuracy of the vibration gyro 12 can be improved and the resolution can be improved. Further, since the error due to the difference in electrostatic capacitance between the piezoelectric elements 16a and 16b can be ignored, the adjustment work can be reduced. Further, in this detection circuit 10, there is no need to attach a filter or the like to eliminate an error, and the circuit is simple.

In the above-described embodiment, a signal having a frequency of 1/2 of the frequency of the main signal is used as the sub signal, but the frequency of the sub signal is n times or 1 / n times the frequency of the main signal. A signal may be used. Even in this case, by detecting the output from the differential circuit 40 in synchronization with the main signal and the sub signal, it is possible to obtain only the output according to the rotational angular velocity.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2A is a perspective view showing a vibration gyro detected by the detection circuit shown in FIG. 1, and FIG. 2B is a line II B-II B in FIG. 2A.
FIG. FIG. 3 is a waveform diagram showing a state in which the synchronous detection is performed by the first synchronous detection circuit. FIG. 4 is a waveform diagram showing a state in which synchronous detection is performed by the second synchronous detection circuit. FIG. 5 is a block diagram showing an example of a conventional detection circuit which is the background of the present invention. In the figure, 10 is a detection circuit, 12 is a vibration gyro, 14 is a vibrating body, 16a, 16b and 16c are piezoelectric elements, 36 is an excitation signal generation circuit, 38 is a sub-signal transmission circuit, 40 is a differential circuit, and 42 is a second circuit. 1 is a synchronous detection circuit, 44 is a DC amplification circuit, and 46 is a second synchronous detection circuit.

Claims (1)

(57) [Claims] 1. A detection circuit for measuring the output of a vibrating gyroscope comprising a polygonal prism vibrating body and a piezoelectric element formed on at least two non-parallel side surfaces of the vibrating body. An excitation signal generation circuit for applying a main signal having an excitation frequency for excitation to the two piezoelectric elements, and a sub-signal having a frequency n times or 1 / n times the main signal to the two piezoelectric elements. A sub-signal sending circuit for applying, a differential circuit for detecting a difference between outputs from the two piezoelectric elements, and a first circuit for detecting an output from the differential circuit in synchronization with the main signal. Detection circuit, second detection circuit for detecting output from the differential circuit in synchronization with the sub-signal, output from the first synchronous detection circuit and output from the second synchronous detection circuit Synthesis circuit for synthesizing and Including,
Detection circuit.