RESONANT FREQUENCY VIBRATIONAL TEST

Abstract

This invention relates to a resonant frequency vibrational test and a method of subjecting a component to such a resonant frequency vibrational test.

Claims

1.-14. (canceled)

15. A method of subjecting a component to a resonant frequency vibrational test in which the component is excited in vibration by an exciter on the basis of an exciter input signal, the method comprising: providing, based on measuring the vibration of the component, a target frequency signal indicative of a frequency control signal which is the phase difference between the vibration of the exciter and the vibration of the component, the vibration of the component being measured by a motion sensor; and exciting the exciter in vibration with a smoothed exciter input signal, the exciter input signal having been adjusted by the target frequency signal.

16. The method of claim 15, comprising: providing, based on measuring the vibration of the component, a target magnitude signal indicative of a magnitude control signal which is the magnitude difference between the vibration of the component and a desired magnitude value, and exciting the exciter in vibration with the smoothed exciter input signal, the exciter input signal having been adjusted by the target frequency signal and the target magnitude signal.

17. The method of claim 15, comprising: providing, based on measuring the vibration of the component, a smoothed target magnitude signal indicative of a magnitude control signal which is the magnitude difference between the vibration of the component and a desired magnitude value, and exciting the exciter in vibration with the smoothed exciter input signal, the exciter input signal having been adjusted by the target frequency signal and the target magnitude signal.

18. The method of claim 15, in which the smoothed exciter input signal is provided by: smoothing the target frequency signal, and using the smoothed target frequency signal to adjust the exciter input signal.

19. The method of claim 15, in which the smoothed exciter input signal is provided by a Hopf oscillator driven by the target frequency signal.

20. The method of claim 15, in which the frequency control signal is smoothed by a method selected from rolling average or by a low-pass filter.

21. The method of claim 15, in which the exciter input signal is continuously adjusted by the target frequency signal.

22. The method of claim 21, in which the target frequency signal is adjusted by a frequency control according to the frequency control signal.

23. The method of claim 21, in which the target frequency signal is adjusted by a proportional integral control, according to the smoothed frequency control signal

24. The method of claim 21, in which the frequency control provides a smoothed target frequency signal.

25. The method of claim 21, in which the proportional integral control provides a smoothed target frequency signal.

26. The method of claim 15, in which the frequency control signal is based on the phase difference, obtained by Fourier series terms, between the vibration of the component and the vibration of the exciter.

27. A method of subjecting a component to a resonant frequency vibrational test in which the component is excited in vibration by an exciter on the basis of an exciter input signal, the method comprising: providing, based on measuring the vibration of the component, a target frequency signal indicative of a frequency control signal which is the phase difference between the vibration of the exciter and the vibration of the component, the vibration of the component being measured by a motion sensor; providing, based on measuring the vibration of the component, a target magnitude signal indicative of a magnitude control signal which is the magnitude difference between the vibration of the component and a desired magnitude value; and exciting the exciter in vibration with the smoothed exciter input signal, the exciter input signal having been adjusted by the target frequency signal and the target magnitude signal; in which the smoothed exciter input signal is provided by: smoothing the target frequency signal, and using the smoothed target frequency signal to adjust the exciter input signal; in which the smoothed exciter input signal is provided by a Hopf oscillator driven by the target frequency signal; in which the exciter input signal is continuously adjusted by the target frequency signal; in which the target frequency signal is adjusted by a proportional integral control, according to the smoothed frequency control signal; and in which the proportional integral control provides a smoothed target frequency signal.

28. An apparatus configured to subject a component to a resonant frequency vibrational test, in which the apparatus comprises: a signal generator configured to provide an exciter input signal; an exciter configured to be excited in vibration on the basis of the exciter input signal; a first motion sensor configured to measure the vibration of the exciter; a second motion sensor configured to measure the vibration of the component; an analyzing system configured to determine a frequency control signal, on the basis of the measurements of i) the vibration of the component and ii) the vibration of the exciter; a signal processor configured to adjust the target frequency signal derived from the frequency control signal and to provide the target frequency signal to the signal generator.

29. The apparatus of claim 28, in which the signal generator is configured to provide a smoothed exciter input signal, based on a target frequency signal; and the analyzing system is configured to determine a smoothed frequency control signal, on the basis of the measurements of i) the vibration of the component and ii) the vibration of the exciter.

30. The apparatus of claim 28, in which the signal generator is a Hopf oscillator.

31. The apparatus of claim 28, in which the signal processor is configured to continuously adjust the target frequency signal.

32. The apparatus of claim 28, in which the analyzing system is further configured to determine a magnitude control signal, on the basis of i) the measurements of the vibration of the component and ii) a desired magnitude value; and the signal processor is further configured to adjust the target magnitude signal derived from the magnitude control signal and to provide the target magnitude signal to the signal generator.

33. The apparatus of claim 32, in which the analyzing system is further configured to determine a smoothed magnitude control signal, on the basis of i) the measurements of the vibration of the component and ii) a desired magnitude value.

Description

[0014] An embodiment of the invention will now be described, by way of example only:

[0015] FIG. 1 shows a block diagram illustrating a method in accordance to the invention;

[0016] FIG. 2 shows a system for the resonant frequency vibrational test:

[0017] The system 1 for conducting a resonant frequency vibrational test illustrated in the block diagram of FIG. 1 comprises an electrodynamic exciter 10, a power amplifier 20, a control unit which can be a computer 30 and an acquisition card 40. FIG. 2 illustrates an example of component under test made of an beam-like assembly 50 having one end secured to the exciter. The other end is unsecured so to be moveable during the test. A first motion sensor 52 positioned at the moving armature measures the excitation signal a.sub.b(t).

[0018] A second motion sensor 51, positioned at an end of the component, measures the response signal a.sub.c(t). The position of the motion sensor is notably based on the standard used, which depends on the component to be tested. The power amplifier 20 is required when using an electrodynamic exciter 10.

[0019] The exciter input signal is generated through a Hopf oscillator. The signal v(k) is generated according to the target frequency f(i) and target voltage magnitude V(i) input signals. It is only after its conversion via a Digital to Analog Converter (DAC) at f.sub.s sampling frequency that the exciter input signal v(t) is sent to the exciter.

[0020] The initial frequency f(i) is set in a resonance zone of the component while the voltage is set high enough to put the component in motion during the first cycle.

[0021] Vibrations induced in an armature of the exciter and the component are measured via the two motion sensors providing a.sub.b(t) and a.sub.c(t) signals, respectively. An Analog to Digital Converter (ADC) transforms a.sub.b(t) and a.sub.c(t) into discrete signals a.sub.b(k) and a.sub.c(k) at frequency f.sub.s. t and k refer to respective time and sample number. After cycle i, phase lag ϕ(i) and magnitude Z(i) are evaluated from Fourier coefficients at f.sub.c exact actual cycle frequency. Phase lag and magnitude are possibly filtered to still improve smoothing, by e.g. averaging or low-pass filtering.

[0022] The frequency and magnitude target signals f(i) and V(i) are updated at f.sub.c through a proportional integral control for the phase and the magnitude. The latter are based on ∈.sub.ϕ(i) the difference between ϕ(i) and the theoretical phase at resonance and on ∈.sub.Z(i) the difference between Z(i) and the desired magnitude Z.sub.d specified by the user.

[0023] The Hopf oscillator then adapts smoothly to changes of target signals f(i) and V(i). The oscillator can be tuned via γ parameter to adjust the speed of convergence to its stable limit cycle. This upstream smoothening of the exciter input signal v(k) distinguishes Hopf oscillator from other digital oscillators.