SU1679208A1 - Ultrasonic vibration indicator - Google Patents

Abstract

The invention relates to a measurement technique and can be used in modal testing of elements of complex structures. The purpose of the invention is to improve the accuracy due to adaptive change of the bandwidth depending on the spectral composition of the signal. The use of a wideband receiving transducer and the frequency control circuit of the master oscillator allows adaptively changing the bandwidth depending on the spectral composition of the signal from the object under study, which improves the accuracy of measuring the parameters of its vibration. 3 il.

Description

The invention relates to a measurement technique and can be used in modal testing of elements of complex structures.

The aim of the invention is to improve the accuracy due to the adaptive change of the bandwidth depending on the spectral composition of the signal.

Figure 1 shows the functional diagram of the ultrasonic phase vibration meter; 2 shows plots of signals at the outputs of the first integrator, a digital-analog converter and a differentiator; on fig.Z - frequency characteristics of the first, second and third receiving converters.

The ultrasonic phase vibration meter contains a series-connected master oscillator 1, an emitting transducer 2, interacting with the object under study 3. a first receiving transducer 4 tuned to a frequency, a second 5 and a third 6 receiving transducers, whose inputs are acoustically connected to the input of the first receiving transducer 4 , first integrator 7, analog-to-digital converter (ADC) 8, digital-to-analog converter (DAC) 9, differentiator 10, notch filter 11, second integrator 12. adder 13. el unit 14 NAND, frequency detector 15, information processing unit 16 and phase detector 17.

The master oscillator 1 is connected by a control input to the output of the differentiator 10, the output to the input of the radiating transducer 2 and to the first input of the phase detector 17.

The first receiving transducer 4 is connected by an output to the input of the notch filter 11, to the first input of the NAND 14 element, to the input of the first integrator 7 and to the first input of the adder 13 connected by the control input to the output of the second in (L

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of the tegrator 12 and to the second input of the element AND-HEN 14, the second and third inputs to the outputs of the second 5 and the third 6 receiving transducers, respectively, and the output to the input of the private detector 15. The output of the AND-14 element is connected to the second input of the phase detector 17, the output of which is connected to the first input of the information processing unit 16 connected by the second input to the output of the frequency detector. The output of the first integrator is connected via series-connected ADC 8 and DAC 9 to the input of the differentiator 10.

Ultrasonic phase vibration meter works as follows. .

Before starting work on master oscillator 1, the code of the number corresponding to the frequency close to fife is set. Each frequency W corresponds to the number u, recorded in the program of operation of the master oscillator 1. From the output of the master oscillator 1, a signal with a frequency close to (Oo) goes to the radiating transducer 2, which converts the electrical signal into mechanical oscillations of the ultrasonic frequency.

The emitted ultrasonic signal, reflected from the object under study 3, is received by the receiving transducers 4,5 and 6. In the calibration stage of the vibrator transducer, when the object under study 3 is stationary, the reflected signal has the same frequency as the emitted by the emitting transducer 2. From the output of the first the receiving transducer 4, tuned to the same frequency (UQ as the radiating transducer 2, the electrical signal is fed to the input of the first integrator 7.

Since a change in the frequency of the master oscillator 1 in one direction or another causes an increase or decrease in the signal at the output of the first integrator 7 (see Fig. 2, a) depending on the approach or distance from the frequency a) o, the output signal of the DAC 9 (see Fig. 2, b) adequately corresponds to the voltage level converted by the ADC 8 to the corresponding number. The step-changing signal from the output of the DAC 9 (see Fig. 2, b) is fed to the input of the differentiator 10. Where it is converted into pulses of positive or negative polarity (see Fig. 2, c). The pulses arriving at the control input of the master oscillator 1 from the output of the differentiator 10 increase the number ni entered into the programmer of the master oscillator by one in the case when these pulses have a positive polarity. It will be

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occur when the output of the first integrator 7 increases, which indicates that the frequency of the master oscillator 1 approaches the resonant frequency Sho, to which the radiating converter 2 and the first converter 4 are tuned. When the frequency rf is reached, which corresponds to the maximum value of the output signal of the first integrator 7 the polarity of the positive pulses at the output of the differentiator 10 is changed to negative, and the change in the frequency of the signal at the output of the master oscillator 1 is stopped. The master oscillator 1 from this moment runs at the frequency Sho, since the first negative pulse from the output of the differentiator 10 blocks it.

After performing this calibration operation, the process of direct measurement of the vibration displacement of the object under study 3 begins. Here we can consider two processes. The first is the process when the oscillation of the object under study 3 is in the low frequency range, then the frequency modulation of the reflected signal is small, and therefore the frequency deviation of this signal is small Sd 2 ttfg "Q. In this case, the connection of the second 5 and third 6 receiving transducers , built-in respectively on the frequency of CB + Q and Sho - O; optional Since the degree of frequency deviation of the reflected signal is unknown a priori, and its spectral composition is not known, in any case, the signal from the output of the first receiving transducer 4 is fed to a notch filter 11 tuned to the frequency (OO. Since the frequency deviation is small and the largest fraction of energy contains in the main harmonic (DO, the power of the signal passing through the notch filter 11 is insufficient for the output signal of the second integrator 12 to close the NAND element 14. Since in this case the NAND 14 element is open then the signal from the output of the first receiving converter 4 freely passes to the second input of the phase detector 17. The first input of which receives the reference signal from the output of the master oscillator 1. The device operates in the mode of measuring vibration displacements. The output signal of the phase detector 17 goes to the first input of block 16 processing information.

Suppose that the oscillation frequency of the object under study 3 has increased to that value when the deviation of the reflected signal Sd - Q.B in this case, the spectral composition of the reflected signal is saturated with side components. The proportion of energy attributable to the main harmonic of the soybeans becomes the same order as the lateral components. In this case, the energy content of the harmonic components at the output of the notch filter 11 is significantly higher, and the signal at the output of the second integrator 12 reaches the response threshold of the AND-NE element 14, which closes to pass the signal to the second input of the phase detector 17. At the same time, 10 output the signal of the second integrator 12, which arrives at the control input of the adder 13, is sufficient in absolute value for its operation. Since the passbands of the receiving transducers 15, 4, 5, 6 intersect at a level of 0.707 (see Fig. 3), there is no need to tune them to the mechanical resonance frequency. The broadband signal from the output of the receiving transducers 4, 5, 6 through 20 adder 13 is fed to the input of the frequency detector 15, where the envelope carrying information on the velocities of the object under study 3 is extracted from the frequency-modulated signal. This signal goes to the second input block 16 information processing.

The use of the invention makes it possible to increase the control accuracy by using a wideband receiving converter with an adaptively variable bandwidth depending on the spectral composition of the signals from the object under study.

Claims (1)

Formula 35 Ultrasonic phase vibration meter containing sequentially electro-acoustically connected master oscillator, a radiating transducer and a first receiving transducer, a phase detector, an NAND element, a differentiator and a first integrator and an analog-digital converter connected in series, the output of the master oscillator is connected to the first input of the phase detector, characterized in that increase accuracy, it is equipped with a second and third receiving converters, connected in series by a notch filter and a second integrator, adder, frequency detector, b the information processing unit and digital-to-analog converter connected by the input to the output of the analog-digital converter, the output to the input of the differentiator, the output of which is connected to the control input of the master oscillator, the input of the first integrator is connected to the first input of the NAND element, to the input notch filter to the output of the first receiving converter and to the first information input of the adder connected by the control input to the output of the second integrator and to the second input of the AND-NOT element. the second and third information inputs to the outputs of the second and third receiving transducers, respectively, the output to the frequency detector input, the output of the NAND element is connected to the second input of the phase detector, the output of which is connected to the first input of the information processing unit connected to the second input of the frequency the detector. (/ 0.707 sz „ 63 & "about / s FIG. 2