Application Cases

Experiment Title: Structural Dynamic Characteristic Testing and Analysis

Testing Purpose:To verify that the piezoelectric MFC actuator, within a wide frequency band that includes its natural frequency, is driven by harmonic excitation to produce mechanical forces that affect its input-output relationship. This leads to the phenomenon of the steady-state hysteresis curve of the piezoelectric MFC actuator flipping and becoming approximately linear when the driving voltage frequency is in the range of 20-50Hz. In this paper, an experimental setup for testing the structural dynamic characteristics of the piezoelectric MFC actuator is constructed. Using a harmonic sweep signal with a frequency range of 20-50Hz, the inherent structural dynamic characteristics of the piezoelectric MFC actuator under both external excitation and self-excitation modes are tested. The main reasons for the flipping and approximate linearity of the piezoelectric MFC actuator's steady-state hysteresis curve are analyzed and explained by combining the dynamic equation of a single-degree-of-freedom system.

Testing Equipment:ATA-2041 High Voltage Amplifier, Exciter, Vibration Meter Controller, Piezoelectric MFC Actuator, etc.

Experiment Process:

Figure 1: Schematic diagram and physical diagram of the experimental setup for testing the structural dynamic characteristics of the piezoelectric MFC actuator: (a) Block diagram, (b) Physical diagram.

The block diagram and physical diagram of the experimental setup for testing the structural dynamic characteristics of the piezoelectric MFC actuator are shown in Figure 1(a) and Figure 1(b), respectively. The experimental process involves first using a real-time simulation system to generate a harmonic sweep signal with a driving voltage frequency range of 20-50Hz. This signal is amplified by the high voltage amplifier and applied to the piezoelectric MFC actuator. The output displacement of the piezoelectric MFC actuator, which is generated in a self-excited manner and has structural dynamic characteristics, is measured by a laser Doppler vibrometer and is real-time collected by the computer through the real-time simulation system. Afterward, the piezoelectric MFC actuator is stopped, and the harmonic sweep signal is amplified by the exciter power amplifier and applied to the exciter. The structural dynamic characteristics of the piezoelectric MFC actuator are tested using the external excitation method, in which the exciter drives the motion of the piezoelectric MFC actuator. The external excitation method uses the vibration of the exciter to excite the structural dynamic characteristics of the piezoelectric MFC actuator. This method can effectively avoid the influence of the hysteresis and creep characteristics of the piezoelectric ceramic rectangular rod on the output displacement of the piezoelectric MFC actuator, allowing for the separate analysis of the influence of the structural dynamic characteristics on the input-output relationship.

Figure 2: Structural dynamic characteristic spectrum of the piezoelectric MFC actuator: (a) External excitation method, (b) Self-excitation method.

Experimental Results:

Using the experimental setup for testing the structural dynamic characteristics of the piezoelectric MFC actuator shown in Figure 1(b), the structural dynamic characteristic spectra of the piezoelectric MFC actuator under external excitation and self-excitation are shown in Figure 2(a) and Figure 2(b), respectively. According to Figure 2, the natural frequencies of the piezoelectric MFC actuator under external excitation and self-excitation are 38.8Hz and 39.6Hz, respectively, with a difference of 0.8Hz. The test results indicate that the natural frequency of the piezoelectric MFC actuator is independent of the excitation method, and both testing methods can effectively excite the structural dynamic characteristics of the piezoelectric MFC actuator. Based on Figure 2(a), within the driving voltage frequency range of 20-50Hz for the exciter, the external excitation method, by avoiding the influence of the hysteresis and creep characteristics of the piezoelectric ceramic rectangular rod on the output displacement of the piezoelectric MFC actuator, can consider only the influence of the structural dynamic characteristics of the flexible beam on the input-output relationship of the piezoelectric MFC actuator. The amplitude and phase changes of the output displacement of the piezoelectric MFC actuator are caused by the amplitude and phase lag changes related to the system's natural frequency.

High Voltage Amplifier Recommendation: ATA-2041

Figure: Specifications of the ATA-2041 High Voltage Amplifier

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