JPH11248408A - Dynamic strain measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic strain measuring instrument which can detect the dynamic strain of an object to be measured with high accuracy and can be reduced in cost. SOLUTION: A dynamic strain measuring instrument detects the dynamic strain of an object to be measured with high accuracy by lowering the gain of a DC component VS contained in a detect signal generated from a strain sensor 10 and, at the same time, effectively amplifying the AC component νS contained in the detect signal by making a constant current to flow to a strain gauge 12 constituting the strain sensor 10 and can make temperature compensation on the AC component νS by using the DC component VS. Therefore, the configuration of the measuring instrument can be simplified and, at the same time, the manufacturing cost of the instrument can be reduced, because it becomes unnecessary to provide, for example, a temperature sensor in parallel with the strain sensor 10 for making the temperature compensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dynamic strain measuring device, and more particularly to a dynamic strain measuring device for detecting dynamic strain on the surface of a turbine blade of a jet engine in real time.

[0002]

2. Description of the Related Art As a conventional dynamic strain measuring apparatus, for example, there is one as shown in FIG. In FIG. 5, a constant current source is connected to a strain gauge of a strain sensor, and dynamic strain of the strain gauge is detected by a detection signal of the strain sensor. The detection signal of the strain sensor includes an AC component and a DC component. Are superimposed.

[0003] That is, passing a constant current I _g to the resistance R _g of the strain gauge, if a dynamic strain to the strain gauge occurs, the resistance value variation [Delta] R _g of the strain gauge occurs, the AC component (dynamic strain signal voltage) I _g · ΔR _g is generated. In the detection circuit,
DC component V _s (= I _g · R _g ) and AC component v _s (= I _g · Δ
R _g) and a detection signal both components is superimposed (input voltage) is input. Such a detection signal requires signal processing for separating a DC component from an AC component.

[0004]

However, in such a conventional dynamic distortion measuring apparatus, when processing a detection signal in which a DC component and an AC component are superimposed,
When such a detection signal is amplified, not only the AC component (dynamic distortion signal voltage) but also the DC component is amplified. Therefore, when the amplification factor (gain) applied to the detection signal is increased, the DC component increases. There was a problem that it was amplified and eventually became unusable.

[0005] The resistance change ΔR _g due to dynamic strain of the strain gauge is extremely small and covers a wide frequency range. In such a case, in order to process the detection signal, a circuit element (such as an operational amplifier) to be used is required to have a wide frequency band and high precision, but a wideband and high precision operational amplifier is generally used. There is a problem that the circuit for signal processing is costly.

On the other hand, if a relatively inexpensive operational amplifier is cascaded in multiple stages in order to form a circuit for processing the detection signal, an offset (offset) and the like are amplified together. There is a problem that the number of stages must be reduced as much as possible.

The present invention has been made in view of such a conventional problem. A constant current is applied to the resistance of the strain gauge to reduce the gain of the DC component included in the detection signal of the strain sensor, while changing the AC. It is an object of the present invention to provide a dynamic strain measurement device that effectively amplifies components, enables high-precision dynamic strain measurement, and can perform temperature compensation of an AC component using a DC component. .

[0008]

According to a first aspect of the present invention, there is provided a dynamic strain measuring apparatus including a strain sensor including a strain gauge.
A signal processing unit that separates a DC component and an AC component included in a detection signal of the distortion sensor from each other; and a temperature compensation unit that performs temperature compensation of the AC component based on the separated DC component. Is a dynamic strain measuring device.

According to the first aspect of the invention, the change in the resistance value of the strain gauge 12 of the strain sensor 10 appears as an AC component of the detection signal of the strain sensor 10, Contains an AC component and a DC component.

The signal processing means 21 separates a DC component and an AC component included in the detection signal of the distortion sensor 10. The temperature compensating means 26 performs temperature compensation of the AC component using the DC component separated by the signal processing means 21. By performing the temperature compensation, the accuracy of the AC component is increased. In addition, for example, a temperature sensor for performing the temperature compensation does not need to be provided in parallel with the strain sensor 10, so that the configuration is simplified and the cost is reduced. it can.

According to a second aspect of the present invention, there is provided a strain sensor including a strain gauge.
0 in the dynamic strain measuring device provided with the strain sensor 1
A signal processing unit 21 for separating a DC component and an AC component included in the detection signal of 0, and the signal processing unit 21 includes:
Non-inverting amplifier 22, differentiating circuit 23, and capacitor C
₁ , the DC component and the AC component are inputted to a plus terminal of the non-inverting amplifier 22,
And grounded to the negative terminal side via the capacitor C _1, together with lowering the gain of the DC component, taken out the DC component from the negative terminal side of said non-inverting amplifier 22, the output signal from the non-inverting amplifier 22 Is input to the differentiating circuit 23.

According to the second aspect of the present invention, the detection signal of the distortion sensor 10 is input to the plus terminal of the non-inverting amplifier 22 constituting the signal processing means 21. As a result, not only the AC component but also the DC component included in the detection signal is amplified at a predetermined amplification factor.
Capacitor C ₁ to the negative terminal side is plugged in,
Since the capacitor C ₁ to the functions to lower the gain of the DC component, even when the high gain, the DC component compared to the AC component is that no to greatly amplified, output from the non-inverting amplifier 22 The signal will be valid. Next, the output signal from the non-inverting amplifier 22 is input to the differentiating circuit 23. The differentiating circuit 23 can obtain only the amount of change in the output signal, that is, only the AC component of the output signal. The amount of dynamic strain can be measured by the AC component.

According to a third aspect of the present invention, which has been made to solve the above problem, the differentiating circuit 23 is configured by connecting a resistor R and a capacitor C ₂ in series. _3. The dynamic strain measuring apparatus according to claim 2, wherein the capacitors C2 are respectively selected based on a predetermined time constant.

According to the third aspect of the invention, the signal output from the non-inverting amplifier 22 is input to the differentiating circuit 23. If a resistor or the like is selected according to a predetermined time constant, only an AC component having a required frequency band can be separated from a signal component input to the differentiating circuit 23. The amount of dynamic strain can be measured by the AC component.

According to a fourth aspect of the present invention, there is provided a strain sensor including a strain gauge.
0 in the dynamic strain measuring device provided with the strain sensor 1
A signal processing unit 21 for separating a DC component and an AC component included in the detection signal of 0, and the signal processing unit 21 includes:
The non-inverting amplifier 22, a differential amplifier 24 and has a capacitor C _1, and inputs the DC and AC components to the positive terminal of the noninverting amplifier 22, the non-inverting amplifier 2
2 is grounded via the capacitor C ₁ to lower the gain of the DC component, and the DC component is extracted from the negative terminal side of the non-inverting amplifier 22, and the positive terminal of the differential amplifier 24 is The output signal from the non-inverting amplifier 22 is input to the non-inverting amplifier 22 while the non-inverting amplifier 22
A dynamic distortion measuring device characterized by inputting a DC component extracted from a negative terminal side of the dynamic distortion measuring device.

According to the invention described in claim 4, the output signal from the inverting amplifier 22 is input to the positive terminal of the differential amplifier 24, the DC component extracted by the capacitor C ₁ of the differential amplifier 24 Input to the negative terminal side. The signal relating to the DC component is canceled by the differential amplifier 24,
Only the variation of the output signal, that is, only the AC component of the output signal can be obtained. The amount of dynamic strain can be measured by the AC component.

According to a fifth aspect of the present invention, a DC component extracted from the negative terminal of the non-inverting amplifier 22 is supplied to the negative terminal of the differential amplifier 24 by a voltage hologram. The dynamic strain measuring apparatus according to claim 4, wherein the dynamic strain is input through the interface (25).

According to the fifth aspect of the invention, the output signal from the non-inverting amplifier 22 is input to the positive terminal of the differential amplifier 24, and the DC component extracted from the negative terminal of the non-inverting amplifier 22 is , Are input to the minus terminal side of the differential amplifier 24 via the voltage follower 25. The signal relating to the DC component is canceled by the differential amplifier 24, and the amount of change in the output signal, that is, the signal relating to the AC component of the output signal can be obtained. Since the voltage follower 25 is inserted, the DC component can be extracted without affecting the negative terminal side of the non-opposite amplifier, and the extracted DC component is input to the negative terminal side of the differential amplifier 24. be able to.

The invention according to claim 6, which has been made to solve the above problem, is characterized in that the differentiating circuit 23 or the differential amplifier 24 is based on a DC component taken out from the minus terminal side of the non-inverting amplifier 22. The dynamic strain measuring device according to claim 2, further comprising a temperature compensating unit that performs temperature compensation of an output signal from the dynamic strain measuring device.

According to the sixth aspect of the present invention, the output signal from the differentiating circuit 23 or the differential amplifier 24
The AC component can be amplified, and the amount of dynamic distortion can be measured by the AC component.

At this time, the temperature compensating means 26 performs temperature compensation of the output signal from the differentiating circuit 23 or the differential amplifier 24 using the DC component taken out by the capacitor C ₁ . By performing the temperature compensation, the accuracy of the output signal from the differentiating circuit 23 or the differential amplifier 24 is improved. In addition, for example, there is no need to provide a temperature sensor and a strain sensor for performing the temperature compensation. And cost can be reduced.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a circuit diagram of a signal processing unit according to the first embodiment of the present invention. FIG. 2 is a schematic configuration block diagram of the dynamic strain measurement device. FIG.
FIG. 2 is a schematic configuration block diagram of a data processing unit.

The DC component V _s and the AC component ν _{s in} FIG. 1 represent equivalent circuits of the strain sensor 10 according to the present embodiment.
This equivalent circuit includes a constant current circuit for driving the strain sensor 10.

As shown in FIG. 1 to FIG. 3 and FIG. 5, the dynamic strain measuring device includes a strain gauge 12 constituting a strain sensor 10 for measuring a dynamic strain and outputting a detection signal, and a constant current to the strain gauge. a constant current source to flow, the output was detected signal of the strain gauge, a signal processing unit (non-inverting amplifier means) 21 for separating the AC component [nu _s into a DC component V _s, balancing temperature based on the DC component V _s A temperature compensator 26, which is a balance adjuster for generating a detection signal and outputting the signal to a data processing unit 37 to be described later; collecting and storing dynamic strain sensitivity in advance; and detecting a balance adjustment temperature based on the stored dynamic strain sensitivity. And a data processing unit 37 for calculating dynamic strain sensitivity at a temperature corresponding to the signal and correcting the dynamic strain detection signal to calculate corrected dynamic strain data.

The signal processing means 21 includes a non-inverting amplifier (non-inverting amplifier circuit) 22, a differentiating circuit 23, and a capacitor C
Have _one . The DC component V _s and the AC component v _s are input to the plus terminal of the non-inverting amplifier 22. The negative terminal of the non-inverting amplifier 22 is connected to the resistor R ₁ and the capacitor C ₁
Grounded. Further, the negative terminal of the noninverting amplifier 22, the resistance R ₂ of the negative feedback circuit is connected. Also, from the point A between the resistor R ₁ and capacitor C ₁ DC component V _s is extracted, the extracted DC component V _s is inputted to the temperature compensation means 26. Temperature compensation means 2
6, based on the DC component V _s, and is configured to generate a balancing temperature detection signal S _BT.

An output signal which is an output voltage from the non-inverting amplifier 22 is input to a differentiating circuit 23. Differentiating circuit 23
Become a resistor R and a capacitor C ₂ connected in series, the voltage of the resistor R is the derivative of the output signal, i.e. proportional to the output signal of the AC component [nu _s. Resistor R and the capacitor C ₂ is selected based on a predetermined time constant.

The data processing unit 37 has an AC component v _s
Dynamic strain performed (dynamic strain detection signal) voltage converted converted motion distortion detection signal S _SV and the DC component V _s (balance adjustment temperature detection signal) voltage converted converted balancing the temperature detection signal S analog / digital conversion of _BTV It detected data D A / D converter 45 to output as _S and the temperature detection data D _T
And the input AC component ν _s (dynamic distortion detection signal)
An interface unit 46 that outputs a converted dynamic distortion detection signal S _SV having a voltage range that can be input to the D converter 45
When performs interface operation between the A / D converter 45 and the temperature compensating means 26, balancing the temperature detection signal S _BT the A / D converter 45 corresponding to the DC component V _s inputted
Interface unit 47 which outputs as conversion balance adjustment temperature detection signal S _BTV having a voltage range that can be input to
And has a calculation function, a storage function, and a monitor display function, and outputs corrected dynamic strain data DSC based on dynamic strain detection data D _S , temperature detection data D _T, and a relationship between previously stored temperature and dynamic strain sensitivity. And an operation display unit 48.

Next, the operation will be described. A constant current is applied to the strain gauge 12 of the strain sensor 10 and the strain gauge 1
When 2 to dynamic distortion occurs, the detection signal output from the strain sensor 10 will contain a and an AC component [nu _s due to a change in the resistance value of the strain gauge 12 and the DC component V _s.

In FIG. 1, the input voltage of the non-inverting amplifier 22 is
Pressure is AC component ν_s, DC component V_s, Then
From the output terminal of the amplifier 22, the output voltage [(1 + R_Two/
R₁) Ν _s+ V_s] Is obtained. Output voltage [(1 + R_Two/ R₁)
ν_s+ V_s] Is applied to the differentiating circuit 23, and the DC component is
And the AC component ν_sOutput voltage (1 + R_Two/
R₁) Ν_sCan be obtained. ν_sIs small
(R_Two/ R₁) Can be adjusted to
AC component of magnitude ν_sCan be obtained.

The amount of dynamic distortion can be measured from the AC component v _s obtained in this manner. The signal processing means 21, which is the circuit of FIG. 1, can have a simple configuration, and it is not necessary to obtain a large gain in a subsequent stage, and a stable output can be obtained.

When the strain gauge 12 is used for dynamic strain measurement, the extracted DC component V _s can be used as a temperature signal due to the temperature dependence of the gauge resistance itself. Using the extracted DC component V _s , the temperature dependency of the AC component ν _s , which is a dynamic distortion signal, can be compensated, and a highly accurate dynamic distortion sensor can be realized.

In the signal processing means 21 which is the circuit of FIG.
The capacitor C ₁ connected to the non-inverting amplifier 22 functions to extract the DC component V _s , and the AC component v _s
It has functions to lower the gain of the DC component V _s compared to.

The temperature compensating means 26 on the basis of the DC component V _s to generate a balancing temperature detection signal SBT, and outputs to the data processing unit 37.

The interface of the data processing unit 37
The input AC component ν _s(Dynamic distortion detection signal
Signal) to the A / D converter 45.
Conversion dynamic distortion detection signal S_SVOutput to A / D converter 45
I do.

At the same time, the interface unit 47
The input balance adjustment temperature detection signal SBT is output to the A / D converter 45 as a conversion balance adjustment temperature detection signal _SBTV having a voltage range that can be input to the A / D converter 45.

The A / D converter 45, calculation display unit as a conversion motion distortion detection signal S _SV and performs analog / digital conversion of the conversion balance adjustment temperature detection signal S _BTV dynamic distortion detection data D _S and the temperature detection data D _T 48.

Next, the operation of the operation display section 48 will be described. In this case, the detected temperature T and the dynamic strain sensitivity A
It is assumed that the relationship is stored in the calculation display unit 48 in advance. Here, the dynamic strain sensitivity A is a temperature correction coefficient for temperature-correcting the obtained dynamic strain X to obtain a true dynamic strain Z, and has, for example, a relationship of Z = A · X.

Next, the operation display section 48 displays the temperature detection data D
Find the dynamic strain sensitivity A at a temperature T corresponding to _T, when the corresponding dynamic strain sensitivity A is stored, used as it is, when the corresponding dynamic strain sensitivity A is not stored, a dynamic strain Calculate the sensitivity A.

[0039] Next the operation and display unit 48 estimates the true dynamic strain amount Z on the basis of the dynamic strain sensitivity A retrieved or calculated dynamic strain detection data D _S. Then, the operation display unit 48
As shown in FIG. 3, the estimated value of the true dynamic distortion amount Z is displayed on a monitor (not shown), and is output as corrected dynamic distortion data DSC.

Next, the calculation display section 48 determines whether or not to continue the measurement, and terminates the processing when the measurement is completed. In this determination, if the measurement is to be continued, this process is repeated.

FIG. 4 shows a second embodiment of the present invention. In the present embodiment, a differential amplifier 24 is used instead of the differentiating circuit 23 according to the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

The output voltage of the non-inverting amplifier 22 [(1 + R ₂
/ R ₁ ) v _s + V _s ] is connected to the differential amplifier 24 via the resistor R _3.
Is input to the plus terminal. Further, the DC component V _s taken out by the capacitor C ₁ is voltage follower 25
And is input to the negative terminal of the differential amplifier 24 via a resistor R _5. The positive terminal of the differential amplifier 24 is grounded via a resistor R _4, and the negative feedback circuit of the differential amplifier 24 is provided with a resistor R ₆ . Also, each resistor has
The relationship of R ₃ = R ₅ and R ₄ = R ₆ holds.

Accordingly, the output voltage of the non-inverting amplifier 22
DC component V of_sAre canceled and the output of the differential amplifier 24 is
Are the AC components ν_sOutput voltage [(1 + R_Two/ R₁) ・
(R _Four/ R_Three) Ν_s] Is obtained. This AC component ν_sPertain to
The amount of dynamic distortion can be measured from the output voltage.

In the second embodiment, the voltage follower 25
Since put, DC component V _s can be taken out without affecting the negative terminal side of the non-opposite amplifier 22, The differential DC component V _s retrieved amplifier 24
Can be input to the minus terminal side of.

[0045]

According to the dynamic strain measuring apparatus of the present invention, a constant current is applied to a strain gauge constituting a strain sensor,
While reducing the gain of the DC component included in the detection signal generated from the distortion sensor, the AC component is effectively amplified to enable highly accurate detection of the amount of dynamic distortion, and the DC component is used to compensate the temperature of the AC component. For example, it is not necessary to provide a temperature sensor and a strain sensor for performing temperature compensation, so that the configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a signal processing unit according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration block diagram of a dynamic strain measurement device according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration block diagram of a data processing unit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a signal processing unit according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a signal processing unit according to a conventional example.

[Explanation of symbols]

C _1, C ₂ ... capacitors _{R, R 1, R 2,} R 3, R 4, R 5, R 6 ... resistance V _s ... DC component [nu _s ... AC component 10 ... strain sensor 12 ... strain gauge 21 ... signal processing Means 22 Non-inverting amplifier 23 Differentiating circuit 24 Differential amplifier 25 Voltage follower 26 Temperature compensating means 37 Data processing unit 45 A / D converter 46 Interface unit 47 Interface unit 48 Operation display unit

Claims (6)

[Claims] 1. A dynamic strain measuring device provided with a strain sensor including a strain gauge, wherein: a signal processing means for separating a DC component and an AC component included in a detection signal of the strain sensor; Temperature compensating means for compensating the temperature of the AC component based on the dynamic strain. 2. A dynamic strain measuring apparatus provided with a strain sensor including a strain gauge, comprising: a signal processing unit for separating a DC component and an AC component included in a detection signal of the strain sensor; , A non-inverting amplifier, a differentiating circuit, and
Having a capacitor, inputting the DC component and the AC component to the plus terminal of the non-inverting amplifier, grounding the minus terminal side of the non-inverting amplifier via the capacitor, and reducing the gain of the DC component; A dynamic distortion measuring device, wherein the DC component is extracted from a minus terminal side of the non-inverting amplifier, and an output signal from the non-inverting amplifier is input to the differentiating circuit. 3. The differential circuit according to claim 2, wherein a resistor and a capacitor are connected in series, and the resistor and the capacitor are respectively selected based on a predetermined time constant. The dynamic strain measurement device according to the above. 4. A dynamic strain measurement device provided with a strain sensor including a strain gauge, comprising: a signal processing unit that separates a DC component and an AC component included in a detection signal of the strain sensor; A non-inverting amplifier, a differential amplifier, and a capacitor, the DC component and the AC component are input to a positive terminal of the non-inverting amplifier, and a negative terminal side of the non-inverting amplifier is grounded via the capacitor. Lowering the gain of the DC component, extracting the DC component from the negative terminal side of the non-inverting amplifier, and inputting the output signal from the non-inverting amplifier to the positive terminal side of the differential amplifier, A dynamic distortion measuring apparatus characterized in that a DC component extracted from a negative terminal side of the non-inverting amplifier is input to a negative terminal side of the dynamic amplifier. 5. The operation according to claim 4, wherein a DC component extracted from a negative terminal side of said non-inverting amplifier is input to a negative terminal side of said differential amplifier via a voltage follower. Strain measuring device. 6. A temperature compensating means for performing temperature compensation of an output signal from the differentiating circuit or the differential amplifier based on a DC component taken out from a minus terminal side of the non-inverting amplifier. The dynamic strain measurement device according to claim 2.