A dynamic resonant frequency control method has been proposed for multimodal piezoelectric actuators. Resonant frequency matching is significant for piezoelectric actuators working in multiple vibration modes. In this case, a group of passive piezoelectric ceramics was used in the actuator design to overcome the resonant frequency ration shift caused by the actuator's machining error, abrasion, and boundary condition changes like load and temperature. A FET alternating current switch was employed to dynamic change the passive parts' electrical boundary condition between open and short, ensuing stiffness change and the continuous resonant frequency control. In this study, an RSIDM (resonant-type smooth impact drive mechanism) actuator prototype with passive PZT was fabricated and investigated. The first and third longitudinal modes' resonant frequency ratio was precisely adjusted to be 1: 2, and a quasi-sawtooth displacement was generated for liner inertia actuation.
