A rotary piezoelectric motor using bending vibrators

• A new idea for constructing rotary piezoelectric motor by utilizing multi-bending vibrators is proposed.
• Two second-order bending vibrations, which are orthogonal in space, are superimposed in the vibrator to produce elliptical movements on the two driving tips.
• The proposed piezoelectric motor has an outstanding merit as its mechanical output ability can be easily adjusted.
• The symmetrically setting of the PZT elements in the vibrator results in uniform elliptical movements on the two feet.

This study intends to present and verify a new idea for constructing rotary piezoelectric motor that utilize multi-bending vibrators to achieve high output power. The vibrator in the proposed motor contains two exponential shape horns located on the two leading ends; two groups of PZT elements are clamped between the two horns by a flange with double head bolt. Two second-order bending vibrations, which are orthogonal in space, are excited by the two groups of PZT elements respectively and then superimpose in the vibrator to produce elliptical movements at the two driving tips. Six vibrators are fabricated and tested using a scanning laser Doppler vibrometer; four of them with closer resonance frequencies are selected to construct the rotary motor. The output abilities of motor with single vibrator, two vibrators and four vibrators are measured respectively; a maximum no-load speed of 298 r/min and a maximum torque of 9.3 N m are achieved under four vibrators driving. It is easy for the proposed motor to change its mechanical output characteristics by changing the number of the vibrators and the diameters of the rotors, which states its practicability.