A Low-Voltage Cylindrical Traveling Wave Ultrasonic Motor Incorporating Multilayered Piezoelectric Ceramics

In-plane bending traveling wave ultrasonic motors (USM), which are compact in structure and flexible in design, have been widely applied in biological engineering, optical engineering, and aerospace engineering. However, the high driving voltage and complicated driving circuit of this kind of USM restrict their further miniaturization and electromechanical integration in these applications and bring some potential safety hazards. To solve this problem, a low-voltage-driving traveling wave USM incorporating cofired multilayer piezoelectric ceramics was proposed in this work. Four cofired piezoelectric ceramics were strategically designed to excite two orthogonal third-order in-plane bending modes with the same frequency of the USM. The principles of traveling wave synthesis and low-voltage-driving of the USM were deduced, and the stator dynamic design and transient dynamic simulation were carried out by finite-element method. The microproperties of cofired piezoelectric multilayer ceramics, the vibration characteristics of the stator, and the mechanical output performance of the USM were tested by experiments. The results indicated that the motor can work as low as 5 $\text{V}_{\text {p-p}}$ . A long stroke with a maximum forward and reverse rotational speeds of 187.7 and 176.6 r/min were obtained, respectively, and a maximum stalling torque of 4.8 mN $\cdot$ m at 47.3 kHz under 15 $\text{V}_{\text {p-p}}$ was achieved. The results showed that the proposed USM is small, low in driving voltage, and high in torque output, which has promising applications in aerospace, biomedicine, and other fields that require a lightweight and integration of driving devices.