Application Cases

Experiment Name: Study on Electrically Induced Vibration Characteristics of Piezoelectric Actuators

Research Direction: Piezoelectric Actuators

Test Objective:
This study aims to analyze the vibration characteristics of piezoelectric actuators under electrical excitation. Taking a bimorph piezoelectric cantilever beam as the object, the forced vibration differential equation of the piezoelectric cantilever beam under voltage excitation was derived based on the energy method and the thermodynamic equilibrium equation. Using a self-built electrically induced vibration test system, the harmonic response and transient response of the piezoelectric beam under AC voltage excitation of different amplitudes were tested. The rationality of the theoretical analysis was verified through experiments, and the effects of excitation voltage and damping on the harmonic response and transient response were discussed. The results indicate that the harmonic response of the piezoelectric cantilever beam is nonlinear, exhibiting spring-softening characteristics. The resonant frequency of the piezoelectric beam decreases with increasing excitation voltage amplitude. Under AC voltage excitations of 6 V, 9 V, and 12 V, the resonant frequencies of the piezoelectric beam are 55.6 Hz, 54.8 Hz, and 54.4 Hz, respectively. When the excitation voltage frequency equals the natural frequency of the piezoelectric beam, its transverse amplitude reaches a peak. When the excitation voltage frequency gradually moves away from the natural frequency, the amplitude decreases rapidly. When the excitation frequency is close to the resonance frequency, the beam exhibits a "beating vibration" phenomenon. Damping has the most significant effect on suppressing the resonance of the piezoelectric beam.

Piezoelectric actuators are widely used in fields such as precision positioning of high-strain materials, design of multilayer devices, large-scale manufacturing processes of portable electronic devices, ultrasonic motors for microrobots, and smart structures due to their advantages of large output displacement, high sensitivity, anti-electromagnetic interference, and strong fracture toughness. Since the operation of piezoelectric actuators is closely related to their vibration characteristics, it is of great significance to deeply understand the vibration characteristics of piezoelectric structures under voltage excitation.

Testing Equipment: ATA-4052 high-voltage power amplifier, frequency characteristic analyzer, multifunctional signal generator, laser displacement sensor, dynamic signal acquisition system, and computer.

Experimental Procedure:
Before the test, an initial transient excitation was applied to the fixed specimen, and its free vibration transient response curve was recorded. The average value was taken after multiple measurements. Finally, the damping ratio of the piezoelectric cantilever beam was determined to be approximately 0.03 using the decay coefficient method. The first-order natural frequency of the piezoelectric cantilever beam was measured using a frequency characteristic analyzer to be 55.513 Hz. A multifunctional signal generator was used to input the electrical excitation signal. Voltage was applied to the upper and lower surface electrodes of the piezoelectric cantilever beam through a power amplifier and wires. Harmonic response tests were conducted in the resonance frequency range of the piezoelectric cantilever beam. Transient response tests were performed in the resonance, near-resonance, and far-from-resonance frequency ranges of the piezoelectric beam. During the test, a laser displacement sensor was used to measure the vibration displacement of the free end of the piezoelectric cantilever beam, and the signals were acquired and transmitted to a computer for display.

Experimental Results:
Based on the energy method and the thermodynamic equilibrium equation, the forced vibration differential equation of the piezoelectric bimorph cantilever beam under voltage excitation was derived. The vibration response of the bimorph piezoelectric cantilever beam under voltage excitation was tested. The theoretical and experimental results are in good agreement. The experimental results show that the vibration response of the piezoelectric beam exhibits spring-softening characteristics. Under AC voltage excitations of 6 V, 9 V, and 12 V, the resonance frequencies are 55.6 Hz, 54.8 Hz, and 54.4 Hz, respectively. Considering the nonlinear phenomena in engineering practice, to increase the driving efficiency of the piezoelectric actuator, it is necessary to appropriately decrease the excitation voltage frequency while increasing the excitation voltage amplitude to maintain resonance. Damping has the most significant suppression effect on the resonance response. Under 9 V resonance frequency voltage excitation, at t = 5 s, the amplitude of the piezoelectric beam with ζ = 0.03 is approximately 62.0% lower than that with ζ = 0.01. The conclusions drawn in this paper can provide theoretical and practical guidance for improving the driving efficiency of piezoelectric actuators.

Figure: Experimental Amplitude-Frequency Characteristic Curve

Figure: Comparison of Experimental and Theoretical Amplitude-Frequency Characteristics

Aigtek ATA-4052 High-Voltage Power Amplifier:

Figure: Specifications of the ATA-4052C High-Voltage Power Amplifier