Application Cases

Experiment Name: Application of Power Amplifier in the Fabrication and Vibration Characteristic Testing of a Two-Dimensional Elliptical Ultrasonic Vibrator

Experiment Objective: To detect and verify whether the actual resonant frequency of the fabricated piezoelectric ceramic vibrator matches the design frequency.

Experimental Content:
By dividing the electrodes on a large piece of piezoelectric ceramic, the effect of arranging four piezoelectric ceramic pieces in parallel is achieved. The electrode material is Ag. The power amplifier drives the piezoelectric ceramic, which is coated on the surface of the ceramic by a plating method. The piezoelectric ceramic and the 304 stainless steel substrate are bonded using epoxy resin adhesive to facilitate vibration transmission.

Experimental Procedure:
The circuit diagram used for resonance characteristic analysis is shown in the figure. The frequency characteristic analyzer provides a swept-frequency output signal and can measure the voltage across the piezoelectric ceramic vibrator and the current through it. The power amplifier (ATA-4052) amplifies the input signal and applies it to the vibrator circuit. The piezoelectric ceramic vibrator is connected in series with a 1-ohm standard resistor. The frequency sweep range is 20 kHz to 30 kHz. When only two alternating electrodes are energized, the B4 mode of the vibrator is excited. When all four electrodes are energized simultaneously, the L1 mode of the vibrator is excited.

Figure: Circuit diagram for resonance characteristic analysis of the elliptical ultrasonic vibrator

Experimental Results:
From the figures, it can be observed that the resonant frequency of the B4 mode of the vibrator is 24.10 kHz, and the anti-resonant frequency is 24.22 kHz. For the L1 mode, the resonant frequency is 24.01 kHz, and the anti-resonant frequency is 24.24 kHz. The difference between the resonant frequencies of the two vibration modes is approximately 0.09 kHz, which is within an acceptable tolerance range when using this ultrasonic vibrator. Furthermore, because the difference between the resonant frequencies of the two oscillation modes is small, maximum amplitude for both longitudinal and bending vibrations can be achieved at nearly the same frequency, leading to the maximized amplitude of the synthesized elliptical vibration.

On the other hand, the difference between the anti-resonance points of the two vibration modes is approximately 0.02 kHz, which is very small. When the ultrasonic vibrator is excited at the resonance point, although the impedance is minimal and the amplitude is maximized, operating near the resonant frequency imposes a relatively large load on the piezoelectric ceramic, potentially leading to its cracking or fracture. When excited at the anti-resonance point, the impedance increases and power consumption is minimized. Therefore, the frequency of the excitation signal is typically chosen to be near the anti-resonance point, and a difference of 0.02 kHz meets the requirements. Thus, it is determined that the vibrator shown in the figure will produce the optimal ultrasonic elliptical trajectory when excited at a frequency of 24.22 kHz.

Figure: Impedance characteristic curve of the L1 mode

Figure: Impedance characteristic curve of the B4 mode

The difference between the anti-resonance points of the two vibration modes is approximately 0.02 kHz, which is very small. When the ultrasonic vibrator is excited at the resonance point, although the impedance is minimal and the amplitude is maximized, operating near the resonant frequency imposes a relatively large load on the piezoelectric ceramic, potentially leading to its cracking or fracture. When excited at the anti-resonance point, the impedance increases and power consumption is minimized. Therefore, the frequency of the excitation signal is typically chosen to be near the anti-resonance point, and a difference of 0.02 kHz meets the requirements. Thus, it is determined that the vibrator shown in the figure will produce the optimal ultrasonic elliptical trajectory when excited at a frequency of 24.22 kHz.

Figure: Comparison of impedance characteristics of L1 mode and B4 mode

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