High-authority piezoelectric actuation system synthesis through mechanical resonance and electrical tailoring

In this research, a new approach is proposed to enhance the effectiveness of piezoelectric actuators. Through mechanical tailoring, the resonant frequencies of the actuation system (this includes the piezoelectric actuator and the related mechanical and electrical elements for actuation) can be tuned to the required actuation frequencies. This obviously will increase the authority (both stroke and force) of the actuation system. However, the resonant actuation system can be hard to control and nonrobust, due to its narrow operating bandwidth. This issue can be resolved through electric circuit tailoring. With the aid of a network of inductance, resistance, and negative capacitance, the actuation resonant peak can be significantly broadened and flattened. In this case, one can achieve a high authority actuation system without the negative effects of resonant problems. The electrical networks can also achieve a fail-safe system due to its passive shunting character. The proposed concept is evaluated using a PZT tube actuator for trailing edge flap control of rotorcraft blades. Promising results are demonstrated, showing that the treatment can indeed create a high-authority and robust actuation system that satisfies the performance requirements of the example application. Also, the proposed concept is verified by experiments using an equivalent circuit model with a synthetic inductor and a negative impedance converter of capacitance.