JPH08145685A - Acoustic gyro - Google Patents

Abstract

PURPOSE: To obtain an acoustic gyro in which deterioration of the accuracy and stability of output due to superposition of low or high frequency component are prevented. CONSTITUTION: Outputs from microphones 31, 32 are amplified through amplifiers 53, 54 and passed through band-pass filters 55, 56 where low and high components are removed. Basic wave outputs from the filters 55, 56 are converted through comparators 57, 58 into rectangular waves which are fed to a phase comparator 59 producing a gyro output corresponding to the phase difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic gyro, and more particularly to a phase difference detection in an acoustic gyro that detects the angular velocity of rotation by utilizing Coriolis force generated when a fluid vibrating by sound undergoes rotational motion. It relates to the improvement of the circuit.

[0002]

2. Description of the Related Art An acoustic gyro, for example, Japanese Patent Application Laid-Open No. 2-25.
According to the technique described in Japanese Patent No. 9414, a detection channel (duct) formed in the upper part of a case has two chambers that are filled with a fluid such as air and divided by a partition wall provided inside an acoustically closed case. It is configured to be connected or communicated. Then, the sound pressure at two points on both sides of the center of the detection channel is detected by a sound pressure detector (for example, a pair of microphones) attached to the case, and the output of this sound pressure detector is input to the phase difference detection circuit. The output corresponding to the phase difference is obtained.

In this conventional example, when a sound source is driven, two chambers are differentially given a volume change having equal absolute values and opposite signs, and this oscillating volume change causes a change in internal volume of a detection channel. Oscillating flow occurs in the air. Here, since the case is one in which two rooms are connected by a detection channel to form one acoustic resonance system, when the sound source is driven by, for example, a sine wave output when the case is stationary. The air inside the detection channel vibrates in the connecting direction (longitudinal direction) of the detection channel. Then, during this vibration, the sound pressures generated at the two points of the detection channel are equal to each other.

Further, the acoustic neutral point where the sound pressure becomes 0 inside the detection channel is the center of the detection channel when the volumes of the two rooms are equal, and the sound pressure becomes zero at this center. Therefore, normally, the acoustic neutral point is located off the center of the detection channel by making the volumes of the two rooms different. As a result, sound pressure remains at two points on the detection channel, and the remaining sound pressure is detected by the microphone.

When the case is rotating, a differential pressure is generated at the above-mentioned two points of the detection channel by the Coriolis force. As a result of the differential pressure being divided into the sound pressures at two points at rest and being added or subtracted, the sound pressures at the two points undergo a phase change according to the rotational angular velocity of the case. Then, the phase difference of the sound pressure caused by such Coriolis force is detected by the phase difference detection circuit, and based on this phase difference, from the relationship between the angular velocity and the output signal previously obtained by experiments, the case rotation is detected. Seeking the angular velocity.

Here, in the conventional configuration, the sine wave signal obtained from the microphone that detects the sound pressure having the phase difference caused by the Coriolis force is amplified by the amplifier in the phase difference detection circuit, and then the rectangular wave signal is obtained. The signal is input to the phase comparator, and the gyro output corresponding to the phase difference is obtained.

[0007]

In the acoustic gyro having the above-described conventional structure, however, the sine wave signal actually output from the microphone as described above includes low frequency components and high frequency components in addition to the fundamental frequency component. Are irregularly superimposed. Therefore, in the configuration that obtains the gyro output based on this sine wave signal, the sine wave signal is distorted or fluctuated due to the superposition of the low frequency component, so that an irregular phase difference occurs at the rising and rising edges of the rectangular wave, and the high frequency component However, there is a problem in that chattering occurs in the rectangularization due to the superposition of, and an output corresponding to the phase difference cannot be obtained. As a result, there is a problem in that the accuracy or stability of the output of the acoustic gyro decreases.

An object of the present invention is to provide an acoustic gyro which can prevent the deterioration of the output accuracy and stability due to the superposition of the low frequency component and the high frequency component as described above.

[0009]

SUMMARY OF THE INVENTION An acoustic gyro of the present invention comprises a case having two chambers connected by a detection channel, a sound source for driving a fluid filled in the case, and a detection channel in the detection channel. The sound pressure detector includes a pair of sound pressure detectors that detect sound pressures at two points respectively, and a phase difference detection circuit that detects a phase difference between outputs of the pair of sound pressure detectors. In the acoustic gyroscope for detecting a rotational angular velocity, the phase difference detection circuit has a bandpass filter for removing a low frequency component and a high frequency component in the output.

The phase difference detection circuit includes, for example, an amplifier that amplifies the two outputs of the pair of sound pressure detectors, a bandpass filter that removes the low frequency component and the high frequency component from the two amplified outputs, respectively. It is composed of a comparator that converts each of the two outputs of the bandpass filter into a rectangular wave, and a phase comparator that detects the phase difference between the two converted rectangular waves.

[0011]

In the acoustic gyro of the present invention configured as described above, only the fundamental wave component is used by providing the phase difference detection circuit with a bandpass filter for removing low frequency components and high frequency components other than the fundamental wave. The gyro output can be obtained by detecting the phase difference.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 and 2 show an acoustic gyro according to an embodiment of the present invention. This acoustic gyro uses an acoustically closed case 1, and the inside of the case 1 is filled with a fluid such as air.

Inside the case 1, there are formed a partition wall 11 having a through hole at a substantially central portion, and a plate-shaped partition wall 12 integrally connected to the upper end of the partition wall 11. The partition wall 11 divides the inside of the case 1 into a chamber 13 having a volume V1 and a chamber 14 having a volume V2. A speaker 2 serving as a sound source is attached to the through hole of the partition wall 11. A detection channel 15 having a length of 1 is formed between the partition wall 12 and the upper surface of the case 1 to connect or communicate the two chambers 13 and 14 with each other.

A pair of microphones 31 and 32 are mounted on the upper surface of the case 1 at a distance d. The microphones 31 and 32 detect the sound pressures at points Q1 and Q2 on both sides of the detection channel 15, respectively. The phase difference between the outputs of the microphones 31 and 32 is shown in FIG.
As shown in FIG. 5, the phase difference detection circuit 43 is input, and the phase difference detection circuit 43 generates an output according to the phase difference between these inputs.

In the acoustic gyroscope of this embodiment, for example, when the speaker 2 is driven by the signal from the oscillator 45 shown in FIG. 1, the chambers 13 and 14 have volume changes of equal absolute values and opposite signs. Given differentially. An oscillating flow is generated in the air inside the detection channel 15 due to the oscillating volume change provided by the speaker 2.

Here, the acoustic gyro of this embodiment is
The chambers 13 and 14 partitioned by the partition wall 11 are connected by the detection channel 15 to form an acoustic resonance system, and the resonance angular velocity ω in this acoustic resonance system is given by the equation (1).

[0018]

[Equation 1]

However, L is the acoustic inertance of the detection channel 15, and is represented by L = ρl / S (ρ: density of air inside case 1, S: cross-sectional area of detection channel 17). In addition, C1 and C2 are defined as room 1 of volumes V1 and V2, respectively.
Assuming acoustic compliance of 3 and 14, Co = C1
・ It becomes C2 / (C1 + C2). The acoustic compliances C1 and C2 are C1 = V1 / γPo and C2, respectively.
= V2 / γPo (γ: specific heat ratio of air, Po: static pressure inside air of case 1). Further, C ′ is a compliance that represents the output impedance of the sound source, and indicates the degree to which the cone portion of the speaker 2 that is the sound source receives the sound pressure and bends.

When the speaker 2 is driven by the sine wave output having the angular frequency ω while the case 1 is stationary, the air inside the detection channel 15 is u
It vibrates in the length direction of the detection channel 15 at a speed of (t) = Ucosωt (where t: time, U: speed amplitude).

During the above vibration, the detection channel 15
, The sound pressures generated at points Q1 and Q2 are equal to each other and p
(T), which is expressed by equation (2) when the points Q1 and Q2 are located at the center of the detection channel 15 in the longitudinal direction, for example. The acoustic neutral point at which the driving sound pressure of the detection channel 15 becomes 0 is the center of the detection channel 15 if V1 = V2, and p (t) at this acoustic neutral point.
= 0.

[0022]

[Equation 2]

On the other hand, when the case 1 rotates about the vertical line ZZ at an angular velocity Ω, Δp (t) = 2ρdΩu (t) = 2ρdΩ due to the Coriolis force at the points Q1 and Q2.
A differential pressure of U cos ω (t) is generated. Then, this differential pressure is added / subtracted to the sound pressures at the points Q1 and Q2 in the stationary state by being divided into ½ each. That is, if the sound pressures at the points Q1 and Q2 when the case 1 is rotating are p1 (t) and p2 (t), respectively, these are given by equations (3) and (4). In these equations, A,
θ is equations (5) and (6), respectively.

[0024]

(Equation 3)

[0025]

[Equation 4]

[0026]

(Equation 5)

[0027]

(Equation 6)

In this way, the phase difference corresponding to the rotation of the case 1 is detected from the outputs of the microphones 31 and 32. And based on this phase difference, in the same way as in the past,
The rotational angular velocity of Case 1 is obtained.

FIG. 3 shows an embodiment of the phase difference detection circuit 43 in the acoustic gyro of the embodiment configured as described above. In FIG. 3, the output signals of the microphones 31 and 32 attached to the case of the acoustic gyro are input to the amplifiers 53 and 54 and amplified respectively. The amplified output is input to the bandpass filters 55 and 56, and low frequency components and high frequency components other than the fundamental wave are removed. The outputs of the filters 55 and 56 are the comparator 5
It is input to 7, 58 and made into a rectangular wave. Then, the rectangular wave signal is input to the phase comparator 59, and a gyro output corresponding to the phase difference is obtained.

The amplifiers 53 and 54 are composed of an operational amplifier 100 and resistors 101 and 102, for example, as shown in FIG. Then, the input signal is changed to {(R101
+ R102) / R101} times. However, R1
01 and R102 are resistance values of the resistors 101 and 102, respectively.

The bandpass filters 55 and 56 are
For example, as shown in FIG. 5, it is composed of resistors 103 to 111, operational amplifiers 115 to 117, and capacitors 112 to 114. Then, a sine wave in which frequency components other than the fundamental wave are sufficiently removed is output. Here, the bandpass filter 5
The center frequency f of 5 and 56 is f = 1 / (2 × π × R10
3 × C113), and the bandwidth is determined by the resistance ratio of the resistors 108 and 109. However, R103 is the resistance value of the resistor 103, and C113 is the electrostatic capacitance of the capacitor 113.

The comparators 57 and 58, to which the outputs of the band pass filters 55 and 56 are input, convert the input signal into a rectangular wave with the reference voltage as a reference. The two rectangular wave outputs thus created are fed to the phase comparator 59 as described above.
Is input to and a gyro output according to the phase difference is obtained.

FIG. 6 shows another configuration example of the bandpass filter. This bandpass filter includes operational amplifiers 118 to 120, resistors 121 to 127, and a capacitor 13
It is composed of 0 and 131. Where resistors 126 and 127
Is Rf, the electrostatic capacitances of the capacitors 130 and 131 are Cf, and the center frequency f is f = 1 / (2 × π × Rf ×
Cf). The bandwidth is determined by the resistance ratio of the resistors 124 and 125, and the filter output gain is R124 / R1.
21. Note that R124 and R121 are resistance values of the resistors 124 and 121, respectively.

Here, as shown in FIG. 7, the band pass filter has a frequency-frequency which has a peak of amplitude at the fundamental frequency Fn and can sufficiently remove components in a frequency band closer to the fundamental frequency Fn. Those having amplitude characteristics are preferable. Such a bandpass filter is, for example,
A band elimination filter having a frequency-amplitude characteristic as shown in FIG. 8 and a known subtraction circuit can be easily combined.

[0035]

As described above, according to the present invention, the phase difference detection circuit is provided with the bandpass filter for removing the frequency components other than the fundamental wave. Therefore, the output distortion or fluctuation in the phase difference detection circuit is prevented. Moreover, chattering at the time of making a rectangular wave can be prevented. Therefore, it is possible to prevent the output accuracy and stability from being deteriorated due to the superposition of the low frequency component and the high frequency component.

[Brief description of drawings]

FIG. 1 is a plan view of an acoustic gyro according to an embodiment of the present invention.

2A is a sectional view taken along line AA in FIG.
(B) is a sectional view taken along line BB.

FIG. 3 is a circuit diagram of a configuration example of a phase difference detection pad of the acoustic gyro of the embodiment.

4 is a circuit diagram of a configuration example of an amplifier that configures the circuit of FIG.

5 is a circuit diagram of a configuration example of a bandpass filter that constitutes the circuit of FIG.

FIG. 6 is a circuit diagram of another configuration example of a bandpass filter that constitutes the circuit of FIG.

FIG. 7 is a graph showing frequency-amplitude characteristics of a bandpass filter.

FIG. 8 is a graph showing frequency-amplitude characteristics of a band elimination filter that constitutes a bandpass filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Case 2 ... Speakers 11, 12 ... Partition walls 31, 32 ... Microphone 43 ... Phase comparator 45 ... Oscillator 55, 56 ... Bandpass filter 59 ... Phase comparator

Claims (2)

[Claims] 1. A case having two chambers connected by a detection channel, a sound source driving a fluid filled in the case, and a pair of sounds respectively detecting sound pressures at two points in the detection channel. In the acoustic gyro that has a pressure detector and a phase difference detection circuit that detects the phase difference between the outputs of the pair of sound pressure detectors, and the acoustic gyro that detects the rotational angular velocity of the case based on the phase difference, An acoustic gyro, wherein the phase difference detection circuit has a bandpass filter for removing low-frequency components and high-frequency components in the output. 2. The amplifier for amplifying the two outputs of the pair of sound pressure detectors, and the band for removing the low-frequency component and the high-frequency component from the amplified two outputs, respectively. A sound comprising a pass filter, a comparator for converting each of the two outputs of the band pass filter into a rectangular wave, and a phase comparator for detecting a phase difference between the two converted rectangular waves. Expression gyro.