Positioning systems play an important role in industrial and scientific applications, making their performance improvements and functional expansions crucial. Positioning systems generally consist of mechanisms, actuators, controllers, and sensors, with performances and functions depending on their integration. Accordingly, positioning technologies focus on these elements and their integration into the system. Actuators are fundamental and critical elements that characterize positioning systems. Electromagnetic actuators are the most widely used because of their high basic performance, and piezoelectric actuators are often used for fine movement. In addition, research on new actuators with unique characteristics is actively being pursued. In component integration, control technology plays a crucial role in effectively utilizing the characteristics of elements and addressing their drawbacks. With the recent advances in digital technology facilitating nonlinear representations and structural modifications, various control methods have been proposed and evaluated to benefit from these advances. In addition to proposing modeling methods, the effects of manufacturing processes on system performance have been evaluated.

This special issue contains 18 papers covering the design and characteristics of mechanisms and actuators, control technology, system design, and modeling, along with three review papers on positioning technology and its applications. We would like to express our sincere gratitude to the authors for their excellent contributions to the special issue. We also thank the reviewers for their incisive efforts in editing this special issue. We hope that this special issue will help readers enhance their knowledge and understanding of positioning technology and its applications, thereby contributing to its progress.

The demand for sensing in robotics and automation has increased due to the decrease in the labor force. Recent advances in computational performance have advanced the widespread use of image processing technology in various applications. This special issue aims to provide researchers with an opportunity to access the latest research and case studies on advanced image processing, computer vision, and sensing techniques for robotics and automation. The topics of interest in this special issue are as follows:

1) Theory and algorithms: Image processing, computer vision, pattern recognition, object detection, image understanding, media understanding, machine learning, deep learning, 3D measurement, simultaneous localization and mapping (SLAM), multispectral image processing, visualization, virtual reality (VR) / augmented reality (AR) / mixed reality (MR), and datasets for image processing;

2) Industrial applications: Factory automation, machine vision, visual inspection, monitoring, surveying, logistics;

3) Sensing techniques for robotics and automation: Robot vision, advanced driver-assistance systems (ADAS), autonomous driving, robotic picking, assembly, and palletizing;

4) Image processing hardware and software: Image acquisition devices, image sensors, image processing systems, sensor information processing;

5) Man machine interface: Visualization, human interface devices.

This special issue features 20 research articles that highlight the latest advancements in advanced image processing techniques for robotics and automation (Part 1: 10 articles, Part 2: 10 articles). We extend our heartfelt gratitude to all the contributors, reviewers, and editorial staff for their dedication and support in realizing this special issue.

The demand for sensing in robotics and automation has increased because of a decrease in the labor force. Recent advances in computational performance have bolstered the widespread use of image processing technology across various applications. This special issue aims to provide researchers with the opportunity to access the latest research and practical case studies on advanced image processing, computer vision, and sensing techniques for robotics and automation. The topics of interest in this special issue are as follows:

1) Theory and algorithms: Image Processing, Computer Vision, Pattern Recognition, Object Detection, Image Understanding, Media Understanding, Machine Learning, Deep Learning, 3D Measurement, Simultaneous Localization and Mapping (SLAM), Multispectral Image Processing, Visualization, Virtual Reality (VR) / Augmented Reality (AR) / Mixed Reality (MR) , Datasets for Image Processing;

2) Industrial applications: Factory automation, machine vision, visual inspection, monitoring, surveying, logistics;

3) Sensing techniques for robotics and automation: Robot vision, advanced driver-assistance systems (ADAS), autonomous driving, robotic picking, assembly, and palletizing;

4) Image processing hardware and software: Image acquisition devices, image sensors, image processing systems, sensor information processing;

5) Man machine interface: Visualization, human interface devices.

We extend our heartfelt gratitude to all the contributors, reviewers, and editorial staff for their dedication and support in realizing this special issue.

The development of machining and measurement systems is increasingly driven by the demands of digital transformation (DX) and green transformation (GX). Addressing the critical challenges across various fields, including design, manufacturing, inspection, maintenance, and recycling, has become essential to meet the requirements of labor reduction, skill-free operation, and efficiency improvement throughout the entire production process. In addition, it is crucial to ensure social prosperity while managing resource consumption by integrating solutions to these challenges. Consequently, the fundamental performance of production-support tools, such as machine tools, assembly machines, industrial robots, and measuring instruments, must be enhanced. It is equally important to enable the seamless flow of design, evaluation, and operational information throughout the value cycle. This special issue features seven papers highlighting the latest advancements in production systems in the following areas:

- Design and analysis methods for machining fixtures

- Machine tool design, simulation, and evaluation methods

- Measurement and monitoring of machining processes

We extend our heartfelt gratitude to the authors for their valuable contributions, and to the reviewers for their meticulous efforts.

The 15th Best Paper Award 2024 ceremony was held at Gakushikaikan, Tokyo, Japan, on September 20, 2024, attended by the winners and IJAT Editorial Committee members. The Best Paper was severely selected from among 58 papers published in Vol.17 (2023). The Best Paper Award winner received a certificate along with an honorarium of JPY100,000 (nearly US$1,000). We extend our heartfelt congratulations to the winners and sincerely wish them continued success in their future endeavors.

Title: Study on a Novel Peeling of Nano-Particle (PNP) Process for Localized Material Removal on a 4H-SiC Surface by Controllable Magnetic Field

Authors: Thitipat Permpatdechakul, Panart Khajornrungruang, Keisuke Suzuki, and Shotaro Kutomi

Int. J. of Automation Technology, Vol.17 No.4 pp. 410-421, 2023

This is the seventh special issue on Design and Manufacturing for Environmental Sustainability. As the first special issue on the topic was issued in 2009, the topic has a fifteen-year history in this journal. Environmental sustainability was recognized as important for manufacturing even at that time, which is why the special issue was started in this journal. The seriousness of this topic has been increasing not only in Europe but also in Japan and other countries. A recent critical trend has been the way in which companies’ attitudes toward this issue, including their positions on carbon neutrality, a circular economy, and biodiversity, determine their value. Furthermore, particularly striking trend is the promotion of various policies to realize a circular economy, including the adoption of international standards for a circular economy and new eco-design regulations in Europe. These movements indicate the need to transform production and consumption in society as a whole beyond the boundaries of individual companies and industries.

The seventh special issue contains seven well-written papers. The papers cover the following topics:

- Circular economy

- Life cycle design and management

- Environmentally conscious design of products and services

- Low-energy and low-emission manufacturing

- Closed-loop supply chain management

- Sustainable consumption and production

From the fifteen-year history of this special issue, we have been able to learn viewpoints specific to the series in this journal.

Most of the papers, revised and enhanced in response to the editor’s invitation, were originally presented at EcoDesign 2023, the 13th International Symposium on Environmentally Conscious Design and Inverse Manufacturing, held in Nara, Japan.

The editor sincerely thanks the authors and reviewers for their contributions in making this special issue possible. We hope that these articles encourage further research on design and manufacturing for environmental sustainability.

Geometry processing is a software technology that facilitates the appropriate and efficient conversion and processing of digital geometric data, including sampled points, curves, surfaces, images, and volumetric data, based on the intended application. It is a versatile technology and is increasingly adopted in diverse fields that rely on digital technologies and for the popularization of digital transition. Geometry processing is based on a robust and extensive mathematical framework that has been extensively investigated. As the scope of potential applications expands, the practical applications of these theories have increased accordingly. Geometry processing is currently employed for shape acquisition, analysis, design, and inspection in various fields, such as manufacturing, social infrastructure, medicine, natural science, and art. As the range of applications expands, several issues have emerged that require further investigation, such as increasing the accuracy and managing large-scale data.

The objective of this special issue is to provide new insights into geometric-processing capabilities. This issue comprises five papers that present novel aspects of this technology and two comprehensive reviews pertaining to aesthetic curves and related topics, as well as the applications of X-ray computed tomography (CT) in manufacturing. The papers included in this issue are as follows:

- Aesthetic curves and related geometries

- Object recognition from laser-scanned point cloud

- CAD data compression via wavelet transform

- Application of structure-from-motion

- Image analysis using Delaunay graphs

- Surface extraction from X-ray CT scan data

- Automation of manufacturing using X-ray CT scanning

The data types and methods used for geometry processing are diverse and depend on the scenarios. In this issue, we present a diverse range of studies pertaining to geometry processing that encompasses both fundamental concepts and applied studies.

We are grateful to all the contributors, reviewers, and editorial staff for their dedication and support in realizing this issue.

Recently, manufacturing technologies have progressed owing to high industrial demand. For example, in the automobile and aircraft industries, manufacturing processes require technologies that allow for high machining rates of lightweight and/or difficult-to-cut materials. Fabricating medical equipment involves the machining of biocompatible materials with high mechanical strength. Information devices require high-quality ultraprecision manufacturing processes. Furthermore, measurement and characterization technologies are also essential for manufacturing. Along with the evolution of manufacturing technologies, scientific studies have been performed on manufacturing phenomena and process control based on physical and/or mathematical aspects.

This special issue was promoted by the International Conference on Leading Edge Manufacturing/Materials & Processing (LEM&P2023) held from June 12, 2023 to June 16, 2023 at Rutgers University in New Brunswick, sponsored by the Japan Society of Mechanical Engineers. This conference was co-located with the Manufacturing Science Engineering Conference (MSEC), ASME, and North American Manufacturing Research Conference (NAMRC), SME.

This special issue includes nine papers that describe the innovations and detailed progress in the following areas:

- Characterization of materials

- Fundamental study and modeling of material removal process

- Manufacturing control and optimization

- Manufacturing processes for new hard materials

- Micro-/Nano-scale manufacturing

- Tool manufacturing and performance

- Metrology and evaluation

- Surface characterization

This special issue includes technical and scientific discussions that suggest new key technologies for future manufacturing. We hope that this will help readers understand manufacturing processes and improve their operations.

We thank the authors and reviewers for their generous cooperation and the editing staff for their contributions.

Cutting technologies are utilized in many industrial sectors, such as automobile, aircraft, and medical-device manufacturing as well as dies and molds. Thus, the requirements for higher geometric accuracy, better surface integrity, and longer component service lifetimes have substantially increased. In addition, maintaining high machining efficiency while simultaneously reducing power consumption and CO₂ emissions during machining is important for sustainable development.

This special issue features 11 papers on the most recent advances in cutting technologies for metals and composite materials.

- Reverse finishing characteristics of drilling surfaces

- Machining error simulation for end milling

- Visualization of cutting phenomena using a single-crystal diamond tool

- Milling of TiB₂ particle-reinforced high-modulus steel

- Electrodischarge-assisted turning of carbon fiber-reinforced polymers

- Suppression of chatter vibration during double-insert turning

- Prediction of surface roughness components during turning

- Microtome blades for high-precision tissue sectioning

- Boiling of coolant near the cutting edge in high-speed machining

- Residual stress during drilling of aluminum alloy

- Effect of strain hardening on burr control during drilling

This issue provides an understanding of recent developments in cutting technologies, aiming to inspire further research in this field.

We deeply appreciate the careful work of all the authors and thank the reviewers for their diligent efforts.

The demand for high-precision and high-efficient machining of high-performance materials and components has increased in various industries such as optical, automotive, communication, life sciences, and medical sciences. Certain difficult-to-machine materials can be reliably machined using deterministic precision cutting processes. However, hard and brittle materials such as ceramics, carbides, hardened steel molds, glassy materials, or semiconductor materials, require precision abrasive technologies with super abrasives like diamond, cBN, or new tool materials for machining. However, machining high-precision components and their molds/dies using abrasive processes is considerably more difficult due to their complex and non-deterministic nature and textured surfaces. Furthermore, high-energy processes such as laser technology can assist abrasive technologies in ensuring higher precision and efficiency. Precision grinding and polishing processes are primarily used to generate high-quality and functional components, typically made of difficult-to-machine materials. Thus, the surface quality achievable by precision grinding and polishing processes becomes more important for reducing machining time and costs.

This special issue features 10 papers on the most recent advances in precision abrasive technologies. These papers cover the following topics:

- Ultrasonic grinding of micro holes using cemented WC tools

- Drilling holes in CFRP aircraft using cBN electroplated ball end mill

- In situ evaluation of drill wear using tool images

- Grinding belt based on modified information entropy

- Radial directional vibration-assisted grinding of Al₂O₃ ceramics

- Chatter vibration suppression using fixed superabrasive polishing stone

- Free abrasive finishing of internal channels with different cross-sectional geometries

- High-quality machining of cemented carbide using PCD ball end mills

- Fixed-abrasive machining with magnetic brush for Ti-6Al-4V ELI alloy

- High-efficient polishing of polymer surfaces using catalyst-referred etching

This ...<more>

The Internet of Things is playing an important role, organizing all things that use data and connecting them to the Internet. It has been made possible by the rapid progress in smart and real-time measurement technologies, the miniaturization and speeding up of sensor technologies as well as intelligent data processors, and by the spread of cloud technology, which accumulates huge amounts of data. To establish smart and precision manufacturing, not only the improvement of conventional ultraprecision machining techniques but also the development of the novel, high-performance machining techniques has been made. On-machine and in-process measurement are gaining in importance for emerging machining technologies as well as conventional ones. Advanced techniques of machining and metrology as well as feedback for compensation manufacturing have been required for plasticity to on-machine and in-process conditions.

This special issue focuses on metrology and manufacturing measurement and instrumentation for the progress of state-of-the-art on-machine and in-process measurement systems and sensor technologies. It consists of contributions related to, but not limited to, the following topics:

- On-machine, in-process measurement and process monitoring

- Practical application of on-machine, in-process measurement

- Machine tool metrology

- Intelligent micro- and nano-metrology

- Multi-sensor fusion and multi-sensor cooperation

- Form and dimensional measurement and instrumentation

- 3D-surface texture and its micro-characteristics

- Machine learning, AI aided measurement

We would like to sincerely thank all the authors for their contributions, and we sincerely hope that the papers in this special issue further contribute to the development of our future society from a new horizon of metrology.

In recent years, the field of manufacturing has become increasingly diversified and complex to meet various requirements, such as improved manufacturing accuracy, productivity, environmental friendliness, and automation/intelligence in manufacturing sites. Consequently, the fusion of different fields as well as interdisciplinary research has become indispensable for the creation of innovative manufacturing technologies that can realize advanced production systems.

This special issue comprises seven outstanding research papers that focus on advanced precision engineering in manufacturing systems, covering the following topics:

- Advanced cutting technologies

- Advanced machine tools and elements

- Surface finishing technologies

- Non-traditional machining and additive manufacturing

- Nano-scale surface finishing

- Advanced surface processing

All research papers were originally presented at the 19th International Conference on Precision Engineering (ICPE2022), held in Nara, Japan, in 2022. The editors hope that the research papers included in this special issue will offer valuable insights to readers for their future research in the field of manufacturing technology.

Each paper underwent a rigorous peer-review process, and the editors would like to express their deep appreciation for the efforts and excellent work of all the authors and anonymous reviewers who contributed to the realization of this special issue. Finally, it is our sincere hope that the papers in this special issue will further contribute to the advancement of our future society.

The social demands for manufacturing systems are constantly changing with the times. In recent years, environmental and social issues have been complicating these demands. For example, all industrial sectors need to consider environmentally responsible ways to achieve sustainable development goals in a time of paradigm shifts. The demands in the manufacturing field include high productivity, high quality, low energy consumption, and help for aging operators. To meet these various demands for manufacturing systems, we must create innovative manufacturing technologies to realize advanced production systems.

This special issue focuses on state-of-the-art machine tools and manufacturing technologies to accelerate production engineering innovation. This issue consists of eleven research papers covering the following fields.

- Advanced structure and drive systems in machine tools

- Industrial robot applications

- Advanced cutting technologies

- Evaluation and calibration technologies of motion error

- Surface finishing technologies

- Grinding of hard and brittle materials

All of these research contributions were presented at IMEC2022, a joint event with JIMTOF2022, held in Tokyo, Japan in 2022.

I would like to sincerely thank all the authors for their contributions, and I sincerely hope that the papers in this special issue further contribute to the development of our future society.

Additive manufacturing (AM) has undergone rapid development in the past decade. Owing to its capacity to produce complex and functional parts in various industries, it has been recognized as a remarkable scientific and industrial technique. It is used to enhance weight-saving production and reduce the number of parts, with metal-based AM techniques in particular being recognized as the most promising AM techniques developed thus far. This is because of their high potential for direct production through the selective solidification of metal materials from three-dimensional, computer-aided design data. The medical, aerospace, and part molding industries are some of the many expected to reap particular benefit from the ability to produce high-quality models with reduced manufacturing costs and lead times.

The objective of this special issue is to collect recent research works focused on recent trends in AM. This issue includes 7 papers covering the following topics:

- Metal-based powder bed fusion using a laser beam (PBF-LB/M)

- Wire and arc-based AM (WAAM)

- Fused deposition modeling (FDM)

This special issue is expected to help readers understand the recent trends in AM, leading in turn to further research on AM.

We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.

With the advancement of information technologies such as the Internet of Things and artificial intelligence, cyber-physical systems are being introduced into society. At the core of these systems is the digital twin, a computer model (twin) of a physical entity built in cyberspace for simulation-based prediction.

Currently, the digital twin mainly targets artificial objects, such as aircraft engines and factories. However, if it can be extended to humans, it could lead to the realization of human-machine cooperative systems and health promotion services, thereby solving social issues stemming from the aging of society. However, humans are the weakest link in the system, and many technical problems remain to be solved, such as realizing the measurement, modeling, and prediction of human behavior, if the human digital twin is to become reality.

This special issue contains 9 papers on developing essential technologies for the human digital twin and constructing human-machine systems for specific applications. The topics covered include learning algorithms, motion measurement and analysis techniques, human perception, system development, and platform software for system development. These clearly show that cross-disciplinary efforts are essential to the realization of the human digital twin.

We thank the authors of the papers submitted for this special issue. We are confident that the information provided by the authors is suggestive and informative for both specialists and non-specialists alike. We also sincerely appreciate the efforts of the reviewers. Their contributions helped to make this special issue possible. We hope that this special issue will catalyze sharing across the boundaries of research fields along the path to realizing a human digital twin.

Artificial intelligence (AI) techniques have been behind disruptive innovations in every industry. Based on AI techniques, large amounts of data can be converted into actionable insights and predictions. Manufacturers have frequently faced different kinds of challenges, such as unexpected machinery failures or defective product deliveries. Still, the adoption of AI techniques is expected to improve operational efficiency, enable the launch of new products, customize product designs, and plan future financial actions. Recently, manufacturers have been using AI techniques to improve the quality of their products, achieve greater speed and visibility across supply chains, and optimize inventory management.

Given that the attention and interest in AI techniques has been growing rapidly, it is time that the current state of the art of their practical applications be presented. The main aim of this special issue is to bring together the latest AI research and practical case studies of AI techniques in production engineering.

This special issue features 10 papers related to not only operation automation but also sophisticated skill transfer in manufacturers. Their subjects cover various advancements, such as failure diagnosis, product estimation, process planning, operation planning, and workpiece fixturing in the area of machining. Moreover, the authors boldly strive to apply AI technologies even to complex systems in manufacturing fields such as laser-assisted incremental forming, injection molded direct joining, and parts assembling.

We thank the authors for their interesting papers submitted for this special issue, and we are sure that both general readers and specialists will find the information the authors provide both interesting and informative. Moreover, we deeply appreciate the reviewers for their incisive efforts. Without these contributions, this special issue would not have been possible. We truly hope that this special issue triggers further research on AI techniques in production engineering.

Abrasive processing technologies support both the creation of new products and progressive production processes as finishing processing in various industries, such as the automotive, telecommunications, semiconductor, healthcare, energy, and aerospace industries. In this era of major changes, known as the Fourth Industrial Revolution, advanced abrasive processing technologies that produce cutting-edge devices, machinery, and equipment for a smart society are needed. The subjects related to abrasive processing are extremely diverse, including function generation processing and ICT fusion processing, in addition to the continuing basic subjects, including high-efficiency processing, difficult-to-cut material processing, ultra/high-precision processing, etc. The field of abrasive processing has recently been expanding from removal processing to additional types of processing, such as additive manufacturing. As a result, its importance is increasing as a technology indispensable for advanced industries such as healthcare and the production of power semiconductors, cutting-edge semiconductors, etc. On the other hand, new abrasive processing technologies, such as grinding wheel surface property analysis and highly efficient surface finishing methods, have developed along with the advancement of the elemental technologies that support abrasive processing using the latest measurement methods and ultra-precision technology. Furthermore, new research, such as work on energy-assisted or reaction-assisted grinding, has been conducted through the fusion of the materials science and physical chemistry fields. This special issue contains seven papers that cover the following topics.

- Abrasive jet processing

- Analysis of the surface profile of a grinding wheel

- Drilling of glass with a diamond tool

- Reaction-assisted grinding

- Barrel finishing

- High-speed polishing

We deeply appreciate the authors for their careful work and thank the reviewers for their incisive efforts in producing this special issue. We hope that it will help readers understand the latest research on abrasive pro...<more>

This is the sixth special issue on Design and Manufacturing for Environmental Sustainability. As the first special issue on this topic was issued in 2009, the topic has thirteen years of history in this journal. Environmental sustainability was recognized as important for manufacturing even at that time. This is why the special issue was started in this journal. The seriousness of this topic has been increasing not only in Europe but also in Japan and other countries. One critical trend as of late has been the way that the attitude of companies regarding this issue, including their positions on carbon neutrality, circular economy, and biodiversity, has come to determine the value of the company in the eyes of, for example, environment, society, and governance (ESG) finance. Nowadays, we cannot say sustainability or business; we should pursue businesses that contribute to sustainability.

This sixth special issue includes eighteen well-written papers, with one more paper to follow. This series of special issues has focused on topics related to ecodesign, recycling, remanufacturing, low-energy and low-emission manufacturing, and circular economy. The papers in this special issue are also deeply related to these topics. As a result of the thirteen-year history of the special issue, we have been able to learn some viewpoints specific to the series in this journal. This has led this special issue to consist of four subcategories, although they are not explicitly represented in the table of contents. The first subcategory consists of seven papers, from the first paper by K. Halada et al. to the seventh paper by A. Yoshimura et al. These papers are related to design, including evaluation, business, remanufacturing, and materials. Among others, the important viewpoint common to these papers is the “flow” of product lifecycles and materials. The second category starts with the eighth paper by C. Ye et al. and ends with the eleventh paper by Y. Yamashita et al. These papers deal with manufacturing issues in the context of the environmental sustainability. For example, the eighth paper deals with the crushing of ...<more>

The continued effects of the global spread of COVID-19 have reaffirmed that restrictions on the movement of people and products have geopolitical consequences. In addition, the impacts involved in the decarbonization of the global environment have further strengthened the growing demand for the building of a sustainable society. These factors have had no small impact on the global economy and on global manufacturing as well. In this context, the demand for the realization of new manufacturing technologies that can respond to changes in social and economic environments has been growing.

This special issue focuses on recent advances in manufacturing technologies that maximize product quality and reduce costs, with an emphasis on the machinery industry. This special issue of the IJAT contains 12 papers. These include works on cutting technology, machining metrology, advanced machine tools, gear manufacturing technology, additive manufacturing, and more. The first five papers are proposals for new cutting technologies and elucidations of cutting phenomena. The next three papers are new proposals for machining measurements. The next two papers are on precision positioning technologies and a rack gear compensation technology. The last two papers are theoretical investigations into the basic phenomenon of additive manufacturing and its applications.

These papers were originally presented at the 10th International Conference on Leading Edge Manufacturing in the 21st Century (LEM21), held in Kitakyushu, Japan in 2021. The papers have been revised and expanded at the request of the editors.

The editors would like to thank all authors for their comprehensive efforts in making this special issue possible, and would like to thank the anonymous reviewers for their hard work. We wish them all the best in their future research in this field of manufacturing technology.

Actuators are components that are essential to the moving, manipulating, or deforming of objects. Historically, conventional electromagnetic motors as well as pneumatic and hydraulic actuators have been developed to sophistication. In the past several decades, however, many other kinds of actuators based on novel principles have also been proposed. These have employed physical or/and chemical effects, such as piezoelectric, electrostatic, or giant magnetostrctive effects, as well as thermal expansion, phase transformation, or ion mobility in polymers. Not only the novel actuators but also conventional ones have been continually evolving in astounding ways. These actuators have been embedded not only in conventional machines but also in smart ones, such as artificial muscles for robots and power assist systems, electric vehicles, and machine tools. By combining the actuators with the Internet of Things (IoT), they are also used to test equipment. In addition, there is no doubt that the technologies involved in the development of novel actuators and the improvement of their efficiency are key to the achievement of Sustainable Development Goals (SDGs), as actuators currently consume a huge aggregate amount of energy. In sum, actuators have the potential to be central to the development of innovative machines.

This special issue features one review, six research papers, and three technical papers on the most recent advances in various types of actuators. These papers cover topics that include magnetic levitation technologies for precision motion control, electromagnetic motors, fluid power actuators, electrostatic actuators embedded in micro-electromechanical systems, and an ultrasonic motor, plus their applications.

All the papers were refereed through careful peer reviews. I believe that this special issue will help the readers to enhance their understanding and knowledge of actuators and their applications. I would like to express my sincere appreciation to the excellent contributions of all the authors, and I appreciate the incisive efforts of reviewers in producing this special issue.

A Fourth Industrial Revolution has been proposed, and various research and development activities geared toward the realization of smart factories have become extremely active. In smart factories developed individually within companies, the direction of the development activities is changing drastically. Regarding common technologies, research activities and feasible case study activities that are collaborations among industry, academia, and government and that show consideration and awareness of ecosystems are becoming active.

It has been five years since the IJAT last published a special issue on smart manufacturing. Smart factory technologies are becoming more and more important in the industrial world, not as a temporary boom, but as a steady development. Research on smart factory technologies is progressing, as they are considered to be important technologies in the industrial world, along with Digital Transformation (DX) technologies, among others.

This special issue addresses the latest in advanced research on smart factories. We have received many submissions from researchers at universities, public research institutes, and companies, and we are pleased to publish eight papers. The latest research being published mainly concerns the following five topics:

- Smart and digital twinning of machine tools

- Smart and digital twinning of production systems

- Optimization of production systems using scheduling algorithms

- Optimization of production systems including worker operations

- Optimization of energy consumption for production systems

The results of these studies will serve as a reference for further smart factory technologies in the future.

We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts. Without these contributions, this special issue could not have been created. We also hope that this special issue will trigger leading to further advances in smart factories.

The concept of Self-Optimizing Machining Systems (SOMS) has been proposed against the background of Industry 4.0 and the Digital Twin concept, based on cyber-physical systems. In order to improve manufacturing productivity, quality, and efficiency, each component technology related to the machining process, such as CAD/CAM, process modeling/simulation, process monitoring/control, and workpiece assessment, as well as the machine tools themselves, has been developed independently to date. However, series of processes, including the interactions among these component technologies, have finally determined the machining performance and the quality of the products. SOMS deals with the information links among these components comprehensively and plays the important role of combining these links and functionalities to optimize the overall machining system. Nevertheless, an intensive implementation and combination of these technologies has yet to become state-of-the-art in industry, while further research and development for SOMS is required for Industry 4.0 and Digital Twin.

This special issue focuses on the research trends of SOMS, especially the interaction links among machine tools, process monitoring, and work assessment. From researchers who are active on the front lines of manufacturing engineering, the latest achievements related to the development of SOMS are presented in 6 papers. On one hand, the development of sensor-integrated components is indispensable for SOMS to monitor the status of a process and feed it back to a related component in order to control the machining process and its environment. On the other hand, it can be said that visual simulation, virtual metrology, and other epoch-making, on-machine technologies for evaluating machined surfaces, as well as process optimization based on machined surface information, are strongly required.

We hope this special issue will contribute to future research and development for researchers and engineers in the field of manufacturing and machining systems.