Preface

Precision positioning is widely required in both scientific research and industrial application. Taking advantage of high resolution, rapid response, and compact structure, piezoelectric actuators are broadly employed for achieving precision positioning, for example, in the fields of precision machining and measurement, nanomechanical testing, atomic force microscopy (AFM), micromanipulation, and so on. To satisfy the increasing requirements in precision positioning, great efforts have been made to improve the performances of piezoelectric actuators. For example, more and more novel principles have been proposed to design piezoelectric actuators. With the development in the piezoelectric material, driving principle, structure design, and control strategy, the speed, positioning resolution/accuracy, loading capacity, working bandwidth, and stroke of piezoelectric actuators have been significantly improved, further enhancing their applications. Over eight chapters, this book discusses recent achievements and developments in the field.

Chapter 1 focuses on tuning the magnetoelectric coefficient in sintered piezoelectric– magnetostrictive composites by introducing some individual phases. It examines the effects of these introduced phases on the magnetoelectric coefficient, coercive field, saturation magnetization, magnetic permeability, piezomagnetic coefficient, and more.

Chapter 2 focuses on the parasitic motion principle (PMP) of piezoelectric actuators. This type of piezoelectric actuator has received more attention in recent years because of its simple structure, control, and flexible design. The chapter defines PMP as well as discusses its application in the design of piezoelectric actuators. It also presents the similarities and differences of PMP with two other types of stepping principles. Finally, the chapter considers recent developments in structural design and performance improvements of PMP piezoelectric actuators and points out existing issues and future research directions.

Chapter 3 discusses inchworm-type piezoelectric actuators, examining their motion principles, classification (linear, rotary, and multi-DOF), and development. It also examines the future directions of these actuators.

Chapter 4 focuses on the stick-slip piezoelectric actuator, which is very promising for achieving both long working stroke and high positioning resolution. In this chapter, the authors summarize their recent studies on this topic both on the structural design and driving method. In terms of structural design, the authors present various flexure hinge mechanisms, especially asymmetrical flexure hinges, to improve the performances of stick-slip piezoelectric actuators, for example, their velocity and loading capacity. In terms of driving methods, they also present a non-resonant mode smooth driving method (SDM) to suppress the backward motion, and a resonant mode SDM to improve the output performances. The authors present many solutions for improving the performances of stick-slip piezoelectric actuators.

Chapter 5 models piezoceramic actuators for potential applications in future control. It develops a full electro-mechanical model of piezoceramic actuators based on previous studies and determines the parameters of this model. The output of the model agrees well with the experimental data, verifying the validity of the proposed model.

Chapter 6 proposes a coupled suspension system and piezoelectric model to predict the potential of harvested electric power in vehicle suspension systems. It investigates the performance of the piezoelectric material PZT-5H in respect to harvesting energy based on energy density and electric power density.

Chapter 7 presents the applications of piezoelectric actuators in microfluidic technology. It discusses some structures and operating principles of single-chamber and multi-chamber piezoelectric micropumps and demonstrates their application in a chip water-cooling system.

Chapter 8 focuses on the roles of piezoelectric ultrasonic motors (USMs) in the Industry 4.0 era. It discusses their novel working principles, illustrates examples for their effective utilization, and analyzes the key Industry 4.0 technologies for improving their performance.

I am very grateful for the help of several colleagues who contributed to this book, which we hope will assist students and researchers in their work, as well as contribute to new developments in the field of piezoelectric actuators.

> **Hu Huang** School of Mechanical and Aerospace Engineering, Jilin University, Changchun, China
