A digital charge control strategy for reducing the hysteresis in piezoelectric actuators: Analysis, design, and implementation

Abstract

To reduce the cost, complexity and stroke loss due to sensing components in analog charge control, a digital charge control (DCC) strategy for reducing the hysteresis in piezoelectric actuators (PEAs) is presented. In this solution, a current sensor built into the amplifier is used to derive the charge by numerical integration instead of series sensing components. In such an approach the PEA can be directly connected to the amplifier, resulting in no stroke loss. To eliminate the sensed DC and low-frequency current errors, a high pass filter is further incorporated. By analyzing the operating mode and principles, the system and controller design procedures and rules are proposed for the case of impedance balance and then these are extended to the general situation. Based on this approach, an optimized DCC solution without using any passive components is proposed. Finally, the DCC solution is validated by using a single degree of freedom PEA-driven mechanism. To reduce the low-frequency vibration and phase lag, feedback and feedforward control is introduced. Experimental results prove the feasibility and effectiveness of the solution, in which the hysteresis can be reduced to less than 1% of the stroke in the best case. Trajectory tracking can be achieved well up to a frequency of 1000 Hz.