A sunflower-morphology-inspired miniature multi-DOF resonant piezoelectric actuator using combined elastic structure...

Achieving compact structures, simplified excitation schemes, and low activation thresholds while maintaining high efficiency and precision remains challenging for multi-degree-of-freedom (multi-DOF) piezoelectric actuators. To address these limitations, a sunflower-inspired miniature resonant piezoelectric actuator (PBPA) is proposed. The actuator adopts a combinatorial plate-beam elastic structure as its base, characterized by integrating a circular plate at the bottom of a square beam. This structural configuration significantly reduces the longitudinal stiffness, enabling longitudinal-bending-bending modal coupling within an appropriate frequency range. Consequently, this design not only reduces the overall size of the actuator but also lowers its activation threshold. By applying three sets of simple excitation signals, the actuation end is able to generate multi-dimensional oscillatory trajectories. A prototype with dimensions of 30.6 × 41 × 41 mm³ and a mass of 5.51 g is fabricated and assembled into a multi-DOF actuation apparatus. Experimental results demonstrate omnidirectional motion of the spherical slider, with maximum rotational speeds of 22.06 rad/s in the horizontal direction and 4.19 rad/s in the vertical direction under excitation voltages of 50 and 120 V_p-p, respectively. Despite its small size, the PBPA achieves a maximum payload-to-weight ratio of 20.32. Using pulse excitation, the maximum resolution reaches 26.3 μrad and remains at the milliradian level even under payloads exceeding 100 g. Additionally, the actuator exhibits low power consumption (< 1 W) and stable thermal performance. The PBPA is further validated through laser trajectory tracking and camera image acquisition, demonstrating its potential for precision manipulation tasks. Overall, this study provides a promising structural strategy for miniature multi-DOF piezoelectric actuators.