An Inchworm Type Piezoelectric Actuator Working in Resonant State

An inchworm type piezoelectric actuator with four driving feet is proposed and tested. The proposed actuator has merits of easy fabrication and miniaturization structure by using a boned-type structure. Horizontal vibration mode and vertical vibration mode are produced synchronously with a certain temporal phase, and their superimposition makes the driving feet produce elliptical movements. The actuators can achieve bidirectional motion easily by exchanging the two driving signals. The resonance frequencies of the two modes are tuned to be close at 41.35 kHz by adjusting the structural dimensions. The mode shapes and trajectories of driving feet are investigated to verify the driving principle. The vibration amplitudes of driving feet in driving direction are trimmed to be nearly the same via changing the phase difference. The design and analysis are accomplished by finite element method. The vibration characteristics of the prototype are verified by a scanning laser Doppler vibrometer. The fabricated piezoelectric actuator achieves a maximum speed of 1641 mm/s and a maximum thrust of 120 gf.