A two-DOF ultrasonic motor, which could output linear motions with two degrees of freedom by using only one longitudinal-bending hybrid sandwich transducer, was proposed and tested. The motion in horizontal (X) direction was achieved by the hybrid of the second longitudinal and fifth bending vibrations of the motor, while the motion in vertical (Y) direction was gained by the composition of two orthogonal fifth bending vibrations. The proposed ultrasonic motor was designed and the principles for the two-DOF driving were analyzed. Then, the simulation analyses of the motor were accomplished to verify the described principles. Finally, a prototype was fabricated and its mechanical output characteristics were tested. The results indicated that the maximum no-load velocities of the motor in horizontal and vertical directions were 572 mm/s and 543 mm/s under preload of 100 N and voltage of 300 Vp-p, respectively. The maximum output forces in horizontal and vertical directions were 24 N and 22 N when the preload was 200 N. The simulation and experiment results verified the feasibility of the proposed two-DOF ultrasonic motor.

A non-resonant-type piezoelectric motor with a precise driving ability was proposed. The operating principle of the proposed motor is different from the previous non-resonant piezoelectric motors using either the clamping and feeding mechanism (inchworm mechanism) or the inertia drive mechanism. An oblique linear motion formed by the hybrid of two bending motions of a sandwich transducer was used to push the runner step-by-step. Two square-wave voltages were applied to the horizontal and vertical PZT elements to obtain the desired oblique linear motion. The mechanism of the proposed piezoelectric motor was illustrated in detail. Then, transient analyses were performed by ANSYS software to simulate the motion trajectory and to find the response characteristics of the motor. Finally, a prototype was fabricated to verify the mechanism and to test the mechanical output characteristics of the proposed motor. Under the input square-wave voltages of 500 Vp-p, the prototype achieved a step displacement of 5.96 μm, a maximum no-load velocity of 59.64 μm/s and a maximum thrust of 30 N. This paper provides a new mechanism for the design of a non-resonant piezoelectric motor with long stroke and precise driving ability.

The backward motion is an intrinsic feature of the conventional piezoelectric stick-slip actuator (PSSA), limiting the output speed and applications. Various methods have been proposed for restraining the backward motion. Each method has its pros and cons for the practical application of driving a precision motion stage. A novel method for restraining the backward motion is proposed in this article, in which a passive damping foot is utilized to hold the runner when the active driving foot slips on the runner. An actuator is developed based on this mechanism. The structural dimensions of the actuator are determined with an analytic model and a finite element model. A prototype of the proposed actuator is fabricated and tested by experiments. The experiments validate the operating principle of the actuator for restraining the backward motion, which is eliminated (the backward ratio is less than 1%) when the passive damping foot has an appropriate clamping force. The proposed method is very valuable for designing a PSSA with no backward motion, and it can broaden the applications for precision manipulations.

Imitating the behavioral traits or structures of biological organisms can provide new ideas and operating principles for designing microactuators. Inspired by the locomotion of koalas, a lightweight self-locomotion piezoelectric actuator (SLPA) is developed. Based on the hybrid of the longitudinal and bending vibration modes, the proposed SLPA is able to obtain linear locomotion. The configuration of the SLPA is designed based on a thin metal plate with miniature size of 19.5 × 19.5 × 1.1 mm ³ . The operating principle is verified through the finite element analysis simulation. The experimental results show that the prototype achieves maximum speed of 61.68 mm/s and slope angle of 20° when the excitation frequency and voltage are 19.75 kHz and 50 V _p-p , which demonstrates the validity of the proposed SLPA climbing on slopes and the effectiveness of the proposed operating principle. Furthermore, the step displacement resolution of 2.2 μ m is obtained by the proposed SLPA under the resonant working state. Finally, a simple optical focusing system is established to verify the feasibility of potential application of micropiezoelectric actuator.