Wideband and hysteresis-free regulation of piezoelectric actuator based on induced current for high-speed scanning probe microscopy

A novel closed-loop regulation of a piezoelectric actuator is presented to implement wideband and hysteresis-free motion required for high-speed operation of scanning probe microscopy. Velocity of the actuator's displacement detected via the induced current and its integration giving the displacement were used to actively compensate the resonances and hysteresis. The validity of the idea was demonstrated using a prototype circuit composed of operational amplifiers and multilayered piezoelectric actuators. The fundamental resonance of the actuator at 260 kHz was completely eliminated from the actuator's displacement with an appropriate velocity feedback. With an additional displacement feedback the gain error was suppressed within ±5 dB over a frequency range from dc to 1 MHz, while a -45 deg. bandwidth was also maintained as wide as 250 kHz. In addition, intrinsic hysteresis of the actuator measured with an 8 kHz sinusoidal signal was suppressed to below 1%. Responses in displacement of the actuator to burst oscillation and square wave inputs exhibited clear improvement from the uncompensated responses