A growing demand for actuators with a volume of less than 1 mm3 has driven researchers to produce a varied range of micro/milli-scale designs. By examining the underlying physics of the actuator operation we are able to demonstrate why piezoelectric ultrasonic actuators have the greatest potential to meet this need. Moreover, it allows us to create a new classification system for piezoelectric ultrasonic actuators, affording us a better understanding of the core characteristics of each class of actuator, which class is most suited to various applications, and highlights potential areas of future research.

https://users.monash.edu/~lyeo/Dr_Leslie_Yeo/Publications_files/sdarticle-1.pdf

Piezoelectric ultrasonic micro/milli-scale actuators

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

A Two-DOF Ultrasonic Motor Using a Longitudinal–Bending Hybrid Sandwich Transducer

Precision positioning systems with large working stroke (millimeter or more) and micro/nano-scale positioning resolution are widely required in both scientific research and industries. For this kind of applications, piezoelectric materials based actuators show unique advantages and have been widely employed. To overcome the demerit of the limited working stroke for single piezoelectric element, various stepping motion principles have been proposed in the past years, and accordingly, stepping piezoelectric actuators with various structures have been designed and evaluated. This review is aimed to summarize the recent developments and achievements in stepping piezoelectric actuators with large working stroke. Especially, the emphasis is on three main types of stepping piezoelectric actuators, i.e., inchworm type, friction-inertia type, and parasitic type. The motion principles of these three types of piezoelectric actuators and the corresponding developments of various actuators are discussed respectively, followed by pointing out the existing problems in these three types of piezoelectric actuators and proposing some potential research directions in this topic. It is expected that this review is helpful for relevant researchers to understand stepping motion principles as well as piezoelectric actuators, and to successfully select and design stepping piezoelectric actuators for specific applications.

Stepping piezoelectric actuators with large working stroke for nano-positioning systems: A review

Piezoelectric Actuators and Motors: Materials, Designs, and Applications

Piezoelectric actuators have been commercialized in various areas such as information technology, robotics, bio-, medical engineering, ecological and energy engineering. This paper reviews their recent application developments and foresees the future of piezoelectric actuators.

Piezoelectric actuators : 2006 Expansion from IT/robotics to ecological/energy applications

This paper proposes a compact ultrasonic motor with low manufacturing costs, a simpler driving circuit, and scalability. The stator of the motor presented in this paper consists of a hollow metal cylinder, whose outside surface was flattened on two sides at 90 degrees to each other, on which two rectangular piezoelectric plates were bonded. Because the cylinder has a partially square/partially circular outside surface, the stator has two degenerated bending modes that are orthogonal to each other. A wobbling motion is generated on the cylinder when only one piezoelectric plate is excited at a frequency between the two orthogonal bending modes. A rod through a pair of ferrules was used as the rotor of this motor. The prototype motor, whose stator was 2.4 mm in diameter and 10 mm in length, operated at 69.5 kHz, was experimentally characterized, and a maximum torque of 1.8 mNm was obtained.

A piezoelectric motor using two orthogonal bending modes of a hollow cylinder

A miniaturized metal tube ultrasonic motor, the dimensions of which are 1.6 mm in diameter and 6 mm in length, was developed. Two flattened surfaces with 90 degrees were ground on the outer surface of the stator. Two PZT-based piezoelectric ceramics were bonded onto these flat surfaces. The asymmetrical surface of the stator developed the split of the two degenerated orthogonal bending modes, resulting in a wobble motion. The working frequency of the 1.6-mm motor with 6 mm in length was 130 kHz. A torque of 0.5 mNm was reached at a maximum power of 45 mW with a speed of 45 rad/sec. The maximum efficiency was 16%.

A 1.6-mm, metal tube ultrasonic motor

This paper reviews recent developments of micro ultrasonic rotary motors using piezoelectric resonant vibrations. Following the historical background, four ultrasonic motors recently developed at Penn State University are introduced; windmill, PZT tube, metal tube, and shear-type motors. Driving principles and motor characteristics are described in comparison with the conventional ultrasonic motors. Motors with 1.5 mm in diameter and 0.8 mN⋅m in torque have been actually developed.

/pdf/micro-piezoelectric-ultrasonic-motors-1n4wc64oep.pdf

Micro Piezoelectric Ultrasonic Motors

The smallest discrete piezoelectric ultrasonic motor using bulk ceramics was developed. We are proposing basically a two-part motor: stator and rotor. The stator of the present motor consists of a hollow metal brass tube with outer diameter of 1.6 mm, inner diameter of 0.8 mm and length of only 4 mm with 2 PZT plates bonded onto it. Owing to the asymmetrical stator surface, two degenerated orthogonal bending modes were slightly split, resulting in a wobbling motion. Thus, the motor can be driven by a single driving source. The rotor is a spring, which is basically different from previous designs, pressed at both ends to the stator by a pair of ferrules. Consequently, the length of the whole motor assembly was reduced significantly; a final motor length of only 5 mm was obtained. The working frequency under zero load was approximately 227–233 kHz. Although the size is small, relatively high power was obtained under an optimized load condition: torque of 0.06 mNm, maximum power of 3.2 mW with a speed of 118 rad/s, and maximum efficiency of 11% under 48 Vrms at 221 kHz.

http://iopscience.iop.org/article/10.1143/JJAP.43.1429/pdf

A piezoelectric micromotor with a stator of Φ = 1.6 mm and l = 4 mm using bulk PZT

This paper demonstrates a new type of compact ultrasonic motor that operates using a wobbling mode of motion. The motor was driven by a piezoelectric composite stator that consisted of a hollow metal cylinder whose outside surface was flattened on two sides at 90° to each other, upon which two rectangular piezoelectric plates were bonded. A wobbling motion was generated at both ends and at the center of the stator upon application of a sinusoidal voltage to each piezoelectric plate (which were phase shifted by 90° with each other). Results showed that the flexural displacement at the stator's center was ∼ 4 × that at its ends. Consequently, the stator could drive a rotor using a center wobbling motion. Our prototype motor had a significantly higher driving force than conventional end driven stators. The prototype was 4.7 mm in diameter and 20 mm in length, having a rotor 20 mm in diameter. The prototype operated at 46 kHz, had a maximum torque output of ∼ 50 mNm, and had a no-load rotational speed of 70 r...

Serra Cagatay

Papers

A piezoelectric motor using two orthogonal bending modes of a hollow cylinder

A 1.6-mm, metal tube ultrasonic motor

Micro Piezoelectric Ultrasonic Motors

A piezoelectric micromotor with a stator of Φ = 1.6 mm and l = 4 mm using bulk PZT

A 'center-wobbling' ultrasonic rotary motor using a metal tube-piezoelectric plate composite stator