SU1244529A1 - Device for performing vibration testing - Google Patents

Abstract

The invention relates to a technique for vibration testing of products and is intended primarily for determining the resonant frequencies and recording the amplitude-frequency characteristics of dynamically complex products. The aim of the invention is the higher accuracy of vibro-testing of dynamically complex products. This goal is achieved by using a new system for controlling the sweep rate of an excitation frequency of a building containing N vibration measuring transducers installed at various points of the product, means of measuring the phase shift between the vibrations of the moving part of the vibration exciter and the product at the control points and blocks, realizing a cyclical interrogation of the vibration measuring transducers and including in the control circuit that vibration measuring channel, in which the phase shift is closer to / 2. 1 il. V (/) I u 01 th; o

Description

one

The invention relates to test technology, namely, devices for vibration testing, and can be used mainly in determining the resonant frequencies and recording the amplitude-frequency characteristics of dynamically complex products.

The purpose of the invention is to improve the accuracy of vibration testing of dynamically complex products. Using a new system for controlling the sweep rate of the excitation frequency containing N vibration measuring transducers installed at various points of the product, means for measuring the phase shift between the vibrations of the moving part of the vibration exciter and the product at points of the centrol and blocks implementing cyclic polling of vibration measuring transducers and including in the control circuit that vibration measuring channel in which the phase shift is closer

to l / 2.

The drawing shows a structural diagram of the proposed device For vibration tests.

The device for vibration tests contains a generator 1 with blocks of compression, a frequency sweep and a converter with an input frequency (these blocks are not shown), connected to the last control inputs of the first and second accompanying filters 2 and 3 and the recorder drive 4 connected to the generator 1 through the power amplifier 5, the vibration exciter .6, vibration measuring transducers 7 and 8, installed on the subwoofer part of the vibration exciter 6 and the tested product 9. The vibration measuring transducer -7 through the matching amplifier 10 and matching The feed filter 2 is connected to the control input of the generator 1 compression unit. The frequency sweep control system includes a first phase detector 11 connected in series, the inputs of which are connected to the outputs of the accompanying filters 2 and 3, an absolute magnitude detector 12, analog multiplier. 13, the second input of which is connected to the output of the frequency scanner of the generator 1, the first zero detector 14 connected to the output of the detector of absolute magnitude 12, the second zero detector 15, element 16 And whose inputs are connected to the outputs

 s

1244529 .2

null detectors 14 and 15, a key 17, the control input of which is connected to the output of element 16 I, and the information input through an amplifier-limiting device 5 is 18 to an output converter

five

0

5 0 5 0 5

0

frequency generator 1, voltage converter 19 is the frequency connected by the input to the output of the analog multiplier 13, counter 20, whose inputs are connected to the outputs of the converter 19 and the key 17, and the output to the inputs of the digital-to-analog converter 21 (DAC) interpolator 22, the output connected with the control input of the oscillator frequency scanner 1, the differentiator 23 connected to the output of the second accompanying filter 3, and the output to the input of the second null detector 15. The device also contains the first and second analog switches 24 and 25, the moves of which are connected via matching amplifiers 26 to the outputs of N vibration measuring transducers 8, and the codes are connected to information inputs of the second and third accompanying filters 3 and 27, respectively, multiplexer 28, register 29, decoder timer 31 and Control input of the analog switch 24 together with the control The input of the multiplexer 28 is connected to the output of the register 29 o in parallel. The control input of the analog switch 25 together with the information input of the register 29 is parallel to the output of the decoder 30. connected to the input to the timer 31 o The output of the second accompanying filter 3 through multiplexer 28 is connected to the information input of the recorder 4, and the high voltage output of the third accompanying filter 27 is connected through the second phase detector 32 connected in series, the second input of which is connected to the output of the first accompanying filter 2, and the second absolute value detector 33 is connected to the input of the comparison unit 34. The second last input is connected to the output of the first absolute value detector 12, and the output is connected to the control input of the register 29

The device works as follows

The electrical signal from the output of generator 1 after power amplifier 5 is converted by vibration exciter 6 into mechanical oscillations of its mobile.

parts whose amplitude is stabilized by the feedback circuit formed by the vibro-measuring converter 7, matching amplifier 10 and the first accompanying filter 2 tunable by the signal of generator 1 together with the second accompanying filter 3 in order to select the main harmonic of the vibration during the sweep frequency range. Swings The vibration measuring transducers 8 installed on the tested product 9 generate signals for its response to mechanical vibrations, which (signals) after the matching of the amplifier 26 simultaneously arrive at the corresponding inputs of the analog switches 24 and 25. The switch state 24 along with the state The multiplexer 28 is determined by the contents of the register 29, in which the channel number is recorded, where the absolute value of the phase difference and A / 2 is minimal. Switch 25 is cyclically controlled by the decoder 30 with a time frequency When the switch 24 turns on, the signal from the corresponding matching amplifier 26 goes through the accompanying filter 3 to the information input of the multiplexer 28, and in the corresponding channel of the recorder 4 with a paper driving drive from the generator 1 a product response value of 4 th is recorded. point on the applied mechanical vibrations. At the same time, the phase detector 11 converts the magnitude of the phase shift of the vibration of the vibration exciter 6 and the response of the product 9 to the appropriate signal level, which, after being converted by the detector 12 to a uni-polar view, enters one input of the multiplier 13. If the signal value at the first input of the multiplier 13 at the maximum with phase matching, taking into account proportionality, set equal to one, then in the frequency response area far from the resonance one, the magnitude of the signal at the output of the multiplier 13 will be determined by the state of its second input This input receives a signal from the output of the oscillator frequency scanner 1, proportional to the frequency of its output signal. This signal is converted into pulses of the corresponding frequency by converter 19 and causes an increase in the state of counter 20, which

after digital-to-analog conversion in block 21 and interpolation to prevent frequency jumps in block 22, it enters the input of the oscillator frequency scanner 1, causing a corresponding increase in the frequency of its output signal. At the same time, the magnitude of this increment (frequency sweep rate) is chosen as the maximum for the vibration test system used. The increase in speed with increasing frequency of vibration is determined by an increase in the output frequency of converter 19 and a corresponding decrease in the decay time of transients in a mechanical system. At this time, the key 17 is closed, the potential from the output of element 16 And the pulses generated by the amplifier-limiter 18, not pass to the input of counter 20

When approaching the resonant AFC region, the phase detector 11 monitors the reduction of the phase error from 90, the potential of its output decreases, which causes the second input to decrease the output signal of the multiplier 13 and the corresponding decrease in the output frequency of the converter 19 o The sweep frequency of the oscillator 1 frequency decreases in accordance with phase response as long as the shift

 phases will not take the value of 90 °, which corresponds to the moment of resonance in the product. In this case, the zero potential at the output of the phase detector I1, arriving at the input of the multiplier 13, is set. induces the potential of its output to zero, which causes the output pulse to be stopped by the transducer 19. The frequency sweep process stops at the resonance frequency at the time of the establishment of oscillations associated with the attenuation of transients in the mechanical system. The null detector 14 generates a signal at one input of element 16 I. However, the output state of the latter does not change due to the absence of a signal of the null detector 15 at the second input. The moment of the establishment of oscillations at the resonant frequency and the value of the resonant frequency can be judged by the termination of the growth of the response level,

.Registering co. output recording heterodyne accompanying filter 3 in the corresponding channel recorder

4: the differentiator 23 forms in this case a zero output potential. At the same time, the null detector 15 forms the resolving level at the second input of element 16 I, and from its output this level, arriving at the control input of the key 17, permits the passage of pulses to the input of counter 20, thereby leaving the output frequency of the generator 1 from the resonant value at a speed proportional to the current value of the frequency of vibration. The further scanning process is carried out with increased speed in accordance with the described algorithm of the device operation. At the same time, the switch 25 cyclically controlled from the decoder 30 sequentially through matching amplifiers 26 connects vibration-measuring transducers 8 to the input of the heterodyne accompanying filter 27. Phase Detector 32 converts the magnitude of the phase shift of the vibration of the vibrator 6 and the response of the product 9 at points to corresponding levels of signals that Transformations of absolute magnitude by the detector 33 to the polar view are received at one input of comparator 34, while at its other input there is a signal from the detector 13 absolute value, which is proportional to the absolute value of the difference / 2, and the phase shift of the forced oscillations of the product 9 at the above point. If the signal from detector 33 is not greater than from detector 12, then a pulse appears at the output of comparator unit 34, which is fed to the control input of the register 29 and the reloading of the new control channel number, the code of which is present on the information the input of the register 29. After switching the switch 24, the control channel of the device functions as described above,

Claims (1)

Invention Formula A device for vibration testing, containing a master oscillator with blocks of compression, a frequency sweep and an output frequency converter, connected to the latter by control inputs, accompanying filters and a recorder drive connected to The output of the generator through the image amplifier is a vibration exciter, vibration measurement transducers mounted on the moving part of the VC and the tested product, the first vibration measurement transducer through the first matching amplifier and accompaniment filter is connected to the control input of the compression unit, and the system controls the speed of the frequency sweep, including phase-connected phase detector, whose inputs are connected to the outputs of the first and second accompanying filters, detector a single value, analog multiplier, the second input of which is connected to the output of the frequency scanner, the first zero detector, whose input is connected to the detector output of an absolute value, the second zero detector, element I, the inputs of which are connected to the outputs of the zero detector, key, control the input input of which is connected to the output of the element I, and the information input through effort-r, the tel-limiter - with the output frequency converter, serially connected voltage converter - the frequency, the input of which is connected to the output a tax multiplier, a counter connected by the Control input to the key output, a digital-to-analog converter and an interpolator whose output is connected to the control input of the frequency scanner, and a differentiator whose input is connected to the output of the second accompanying filter and the output to the second null detector, which is different in order to increase the accuracy of vibration tests of dynamically complex products, it is equipped with first and second analog switches, multiplexer, register, decoder, timer, third they are accompanied by a filter, a second phase detector, a second absolute value detector and a comparison unit, the information inputs of each analog switch are connected through matching amplifiers to the outputs of N vibration-measuring converters installed on the tested product, the outputs of the first and second analog switches are connected to information inputs the second and third accompanying filters, respectively, the control input of the first analog switch, together with the control input cartoon the plexer is connected to the register output, the control input of the second analog switch, together with the information input of the register is connected to the output of the decoder connected to the timer, the output of the second accompanying filter is multiplexed by V. Shechter, Editor M. Petrov Tekhred I.Popovich Proofreader M. Demchik 3907/45 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5. Production and printing company, Uzhgorod, st. Project, 4 44529 .8 the sor is connected to the information input of the recorder, and the output of the third accompanying filter is connected through the second phase detector 5 connected in series, the second input of which is connected to the output of the first tracking filter, and the second absolute value detector is connected to the input of the comparator, the second input of which is connected 10 to the output the first detector of absolute magnitude, and the output with the control input of the register.