CN105527015A - Flexible structure resonant frequency visualized detection system and method - Google Patents

Abstract

The invention discloses a flexible structure resonance frequency visualization detection system and method. The detection system includes a signal generator, a voltage amplifier, an actuator, a piezoelectric material sensor, an AC-DC self-excited boost conversion circuit, a light-emitting diode, and a luminance meter. The piezoelectric material as a sensor can well sense the structural vibration frequency, The brightness of the light-emitting diode increases with the enhancement of the structural vibration, and the frequency of the structural resonance can be quickly measured and judged.

Description

System and method for visual detection of resonance frequency of flexible structure

technical field

The invention relates to the fields of flexible structure damage detection and structure active vibration control, in particular to a flexible structure resonance frequency visualization detection system and method.

Background technique

The resonant frequency of a structure is important in many fields, including structural design, damage detection, and active vibration control. In damage detection or structural health monitoring, compared with other modal parameters, the resonant frequency as a modal parameter is less sensitive to noise interference and has stronger anti-noise ability.

The sensitive element of the piezoelectric sensor is made of piezoelectric material. When a piezoelectric material is subjected to a force, an electric charge is generated on its surface. After the charge is amplified by the charge amplifier and the measuring circuit and the impedance is transformed, it becomes an electric output proportional to the received external force. Piezoelectric sensors are used to measure force and non-electrical quantities that can be transformed into force. Piezoelectric sensors include piezoelectric ceramics, piezoelectric films and piezoelectric fiber composites, among which piezoelectric films can minimize the interference to the resonance frequency of the system because of the smallest mass.

Polyvinylidene Fluoride (PVDF) piezoelectric film has extremely fast response to changes in mechanical stress or strain, and has a wide frequency response range, so it is suitable for use as a sensing element.

Light-emitting diodes are used as indicator lights in circuits and instruments, or to form text or digital displays. Among them, organic light-emitting diodes (Organic Light-Emitting Diode, OLED) have the characteristics of uniform light-emitting surface and no flicker, and are more conducive to resonance than other point light sources. Frequency of visual testing studies. In this study, piezoelectric sensors are used to measure the structural vibration frequency. The output voltage of the dynamic strain signal measured only by piezoelectric sensors is not high. Therefore, a voltage amplifier circuit is required to drive light-emitting diodes to achieve the visualization of the resonant frequency.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a system and method for visually detecting the resonance frequency of a flexible structure.

The scheme that the present invention solves technical problem is as follows

The flexible structure resonance frequency visual detection system includes a signal generator, a voltage amplifier, an actuator, a piezoelectric sensor, an AC-DC self-excited boost conversion circuit, a light-emitting diode, and a luminance meter; the piezoelectric film sensor and actuator The device is set on the flexible structure to be detected, and the signal generator, voltage amplifier and actuator are connected in sequence. The piezoelectric film sensor is connected to the light-emitting diode through an AC-DC self-excited boost conversion circuit. The luminance meter is used for Detects the brightness of LEDs.

Preferably, the piezoelectric sensor is a piezoelectric film. The AC-DC self-excited boost conversion circuit is an AC-DC-voltage amplifier. The actuator is a laminated piezoelectric actuator. The light emitting diodes are planar organic light emitting diodes.

For the fixed boundary conditions and free boundary conditions of the flexible structure, the recommended installation positions of the actuator and the piezoelectric film sensor are as follows:

(1) Fixed-free boundary conditions: both the actuator and the piezoelectric sensor are installed near the fixed end;

(2) Free-free boundary conditions: the actuator is installed near the free end, and the piezoelectric sensor is installed at 1/4 of the total length of the structure near the free end or at 1/2 of the full length of the structure near the free end.

The invention also discloses a detection method of the detection system, the steps of which are as follows:

The signal generator is connected to the voltage amplifier and inputs the excitation signal to the actuator. The actuator excites the vibration response of the flexible structure. The piezoelectric film sensor attached to the flexible structure feels the vibration and causes the strain to change, and generates a changing voltage signal. The voltage signal The planar organic light-emitting diode is driven by an AC-DC self-excited boost conversion circuit. The brightness of the planar organic light-emitting diode can change with the change of the voltage signal. The luminance meter detects the brightness of the planar organic light-emitting diode, and the vibration frequency corresponding to the maximum brightness is the resonant frequency of the flexible structure.

Compared with the prior art, the present invention has the beneficial effects of:

1) Obtaining the resonant frequency in the prior art requires modal analysis. The present invention has the advantage of rapidly measuring the resonant frequency, and the value of the resonant frequency can be quickly obtained by observing the brightness of the plane organic light-emitting diode with the naked eye.

2) The existing modal analysis technology generally requires traditional sensors such as hammers and accelerometers and a back-end data acquisition and analysis system. The system structure of the present invention is simple, relatively low in cost requirements, and does not require oscilloscopes or signal acquisition equipment.

Description of drawings

Fig. 1 is the schematic structural diagram of embodiment 1 structural resonance frequency visualization detection system;

Fig. 2 is the schematic circuit diagram of embodiment 1;

Fig. 3 is an experimental diagram of OLED lighting near the second-order resonance frequency;

Figure 4 is an experimental diagram of OLED lighting near the third-order resonance frequency;

FIG. 5 is an experiment diagram of OLED luminescence near the fourth-order resonance frequency.

detailed description

As shown in Figure 1, the present invention discloses a flexible structure resonance frequency visual detection system including a signal generator, a voltage amplifier, an actuator, a piezoelectric sensor, an AC-DC self-excited boost conversion circuit, a light emitting diode, a brightness meter; the piezoelectric film sensor and the actuator are arranged on the flexible structure to be detected, the signal generator, the voltage amplifier and the actuator are connected in sequence, and the piezoelectric film sensor is passed through an AC-DC self-excited booster The voltage conversion circuit is connected with the light emitting diode, and the luminance meter is used to detect the brightness of the light emitting diode.

Preferably, the piezoelectric sensor is a piezoelectric film. The AC-DC self-excited boost conversion circuit is an AC-DC-voltage amplifier. The actuator is a laminated piezoelectric actuator. The light emitting diodes are planar organic light emitting diodes.

For the fixed boundary conditions and free boundary conditions of the flexible structure, the recommended installation positions of the actuator and the piezoelectric film sensor are as follows:

(1) Fixed-free boundary conditions: both the actuator and the piezoelectric sensor are installed near the fixed end;

(2) Free-free boundary conditions: the actuator is installed close to the free end, and the piezoelectric sensor is installed on the surface near the 1/4 of the total length of the structure to measure more resonant frequencies. The 1/2 of the free end can be optimized for measuring odd-order resonance frequencies.

The invention also discloses a detection method of the detection system, the steps of which are as follows:

The signal generator is connected to the voltage amplifier and inputs the excitation signal to the actuator. The actuator excites the vibration response of the flexible structure. The piezoelectric film sensor attached to the flexible structure feels the vibration and causes the strain to change, and generates a changing voltage signal. The voltage signal The planar organic light-emitting diode is driven by an AC-DC self-excited boost conversion circuit. The brightness of the planar organic light-emitting diode can change with the change of the voltage signal. The luminance meter detects the brightness of the planar organic light-emitting diode, and the vibration frequency corresponding to the maximum brightness is the resonant frequency of the flexible structure. Example 1:

As shown in Figure 1, it is a schematic structural diagram of this embodiment, in which the material of the cantilever beam is aluminum alloy, the model of the laminated piezoelectric actuator is AE0505D16, the model of the voltage amplifier is XE-500, and the model of the signal generator is DG400. FIG. 2 is a schematic circuit diagram of this embodiment.

From Figure 3-Figure 5, it can be found that as the frequency changes, the brightness of the OLED also changes with the same trend, and the brightness reaches the maximum at the resonance frequency. Fig. 3-Fig. 5 are the luminous experiment diagrams of OLED near the second to fourth order resonant frequency values of the test cantilever beam respectively. The brightness of the OLED is measured by a luminance meter, and the naked eye can distinguish obvious brightness differences. Figure 3 also shows the results of general light-emitting diodes at the resonant frequency value, which shows the advantages of visualization of planar organic light-emitting diodes. This experiment proves that the excitation frequency can be changed quickly by adjusting the signal generator, and the brightness change of the OLED can be observed to quickly determine the resonance frequency value.

Claims (7)

1. A flexible structure resonance frequency visual detection system is characterized in that comprising signal generator, voltage amplifier, actuator, piezoelectric sensor, AC-DC self-excited boost conversion circuit, light emitting diode, luminance meter; The piezoelectric film sensor and actuator are set on the flexible structure to be detected, and the signal generator, voltage amplifier and actuator are connected in sequence. The piezoelectric film sensor is connected with the AC-DC self-excited boost conversion circuit The light emitting diodes are connected, and the luminance meter is used to detect the brightness of the light emitting diodes. 2. The system for visual detection of resonance frequency of flexible structures according to claim 1, characterized in that said piezoelectric sensor is a piezoelectric film. 3. The system for visual detection of resonance frequency of flexible structures according to claim 1, characterized in that said actuator is a stacked piezoelectric actuator. 4. The system for visual detection of resonance frequency of flexible structures according to claim 1, characterized in that said light-emitting diodes are planar organic light-emitting diodes. 5. The flexible structure resonance frequency visual detection system according to claim 1, characterized in that for the two boundary conditions of the flexible structure, i.e. the fixed boundary condition and the free boundary condition, respectively suggest the installation position of the actuator and the piezoelectric film sensor The installation location is as follows: (1) Fixed-free boundary conditions: both the actuator and the piezoelectric sensor are installed near the fixed end; (2) Free-free boundary conditions: the actuator is installed near the free end, and the piezoelectric sensor is installed at 1/4 of the total length of the structure near the free end or at 1/2 of the full length of the structure near the free end. 6. The flexible structure resonance frequency visual detection system according to claim 1, characterized in that the AC-DC self-excited boost conversion circuit is an AC-DC-voltage amplifier. 7. A detection method of detection system as claimed in claim 1, characterized in that the steps are as follows: The signal generator is connected to the voltage amplifier and inputs the excitation signal to the actuator. The actuator excites the vibration response of the flexible structure. The piezoelectric film sensor attached to the flexible structure feels the vibration and causes the strain to change, and generates a changing voltage signal. The voltage signal The planar organic light-emitting diode is driven by an AC-DC self-excited boost conversion circuit. The brightness of the planar organic light-emitting diode can change with the change of the voltage signal. The luminance meter detects the brightness of the planar organic light-emitting diode, and the vibration frequency corresponding to the maximum brightness is the resonant frequency of the flexible structure.