Membrane Mirrors With Bimorph Shape Actuatorsĭeformable mirrors of a proposed type would be equipped with relatively-large-stroke microscopic piezoelectric actuators that would be used to maintain their reflective surfaces in precise shapes. With the excitation voltage of 100 Vpp applying an electric field across the thickness of the bimorph, the tip displacement of the actuator in the axial oscillation and tangential torsional modes are 85 μm and 15 μm, respectively. The spiral-shaped piezoelectric bimorph is fabricated by a precise laser cutting process and consists of two turns with effective length of 60 mm, width of 2.5 mm, and thickness of 1.6 mm, respectively. Simulation results show that compared with the straight piezoelectric bimorph, the spiral-shaped piezoelectric bimorph with two turns has higher inherent frequencies (from 204.79 Hz to 504.84 Hz in terms of axial oscillation mode, and from 319.77 Hz to 704.48 Hz in terms of tangential torsional mode). To obtain a higher resonant frequency, straight piezoelectric bimorph was rolled into spiral-shaped piezoelectric bimorph with identical effective length in this study, which is verified in COMSOL simulations. Higher resonant frequency brings about stronger flight energy, and the flight amplitude can be compensated by displacement-amplification mechanism, such as lever. Piezoelectric cantilever is suitable as an actuator for micro-flapping-wing aircraft. Huang, Fang Sheng Feng, Zhi Hua Ma, Yu Ting Pan, Qiao Sheng Zhang, Lian Sheng Liu, Yong Bin He, Liang Guo High-frequency performance for a spiral-shaped piezoelectric bimorph ![]() Adjustments to the distribution of stiffness along the radius of the bimorph could prevent this and allow for improved deflection without the risk of reaching higher modes. These higher node shapes sharply reduced the volume change and negatively impacted the velocity of the jet at those frequencies. Those with lower stiffness allowed for greater displacement of the surface, initially increasing the volume change, but exhibited higher mode shapes at certain frequency ranges. Bimorphs with higher stiffness exhibited a more desirable (0,1) mode shape, which produced a high volume change inside of the actuator cavity. Results from a bimorph of alternate stiffness were also compared. Phase-locked jet velocities and maps of displacement of the surface of the bimorph were compared between actuators of varying diameter. Knowledge of these could aid in refining the geometry of the cavity to improve efficiency. The velocity performance of synthetic jet actuators is dependent on this volume change and the associated internal pressure changes. The design of piezoelectric bimorphs for synthetic jet actuators could be improved by greater understanding of the deflection of the bimorphs both their mode shapes and the resulting volume change inside the actuator. ![]() ![]() Exploration of Piezoelectric Bimorph Deflection in Synthetic Jet Actuators
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