A frequency-switching dual-DOF piezoelectric ultrasonic actuator based on multiple coupled resonance modes design and optimization

Enabling multi-degree-of-freedom (multi-DOF) motion within limited space is a key challenge for expanding the application of piezoelectric ultrasonic actuators. Existing schemes achieve multi-DOF motion through combinations of multiple stators or multimodal coupling, whereas they suffer from difficulties in miniaturization and complex multiple voltage input. This paper proposes a frequency-switching dual-DOF piezoelectric ultrasonic actuator based on designing multiple coupled resonance modes. By employing a cross-shape stator structure and geometric parameters optimization, two groups of coupled resonance modes are excited at different frequencies, producing elliptical motion trajectories in two DOFs. Dynamic simulations verify the principle of frequency-switching dual-DOF actuation. Experimental results demonstrate that the prototype achieves dual coupled modes at 113 kHz and 142 kHz for the X and Y axis, respectively. The maximum speed and resolution can be 320.62 mm s⁻¹ and 0.47 μm. Moreover, the piezoelectric ultrasonic actuator can manipulate objects in the XOY plane with dual-DOF simply by frequency switching. This work provides a new design scheme with simple signal control and high integration for multi-modal multi DOFs ultrasonic actuation design.