Expansion of Driving Frequency and Voltage Amplitude Limits and Suppression of Dynamic Characteristic Variations of Piezoelectric Stacked Actuators by Forced Liquid Cooling with Silicone Oil

Inhalt:
Piezoelectric stack actuators (PESAs) can generate a response with large force and high resolution. However, when they are continuously driven by applying a large voltage at high frequency, they undergo self-heating resulting in self-damage and dynamic characteristic variations. To avoid these problems, the driving voltage and frequency of PESA must be limited. In this study, we have proposed a forced liquid cooling method to increase the driving voltage and frequency of PESAs. The surface temperatures of PESA driven by large voltage at high frequency were measured using forced liquid cooling and natural heat dissipation. Silicone oil with high insulation resistance was chosen as the coolant. The voltage-displacement curves and frequency responses of PESA were measured. The measured surface temperature of PESA after applying an AC voltage with amplitudes of 10 – 50 Vpk at frequencies of 1 – 10 kHz increased with forced liquid cooling and suppressed to approximately one-tenth of that with natural heat dissipation. Heat transfer analysis also confirmed that the internal temperature of PESA was below the Curie temperature of 145deg C. Hysteresis curves were measured at 10 kHz showing a 15% increase in the displacement amplitude during natural heat dissipation with an increase of 3% during forced liquid cooling. The frequency responses showed that the resonant frequency decreased only during natural dissipation owing to the temperature increase. These results confirm that forced liquid cooling for PESA extends the drive amplitude and frequency limits and suppresses temperature-dependent dynamic variations thereby contributing to the realization of a wider range, higher response, and continuous PESA-equipped machine drive with higher precision.