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Aichi Science and Technology Foundation

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We have developed a non-contact power transmission rotary joint for industrial robots! ~The electric field method has achieved improved durability, lighter weight, and higher efficiency~

Aichi Prefecture and the Aichi Science and Technology Foundation, a public interest incorporated foundation, have been carrying out the Aichi Knowledge Hub Priority Research Project Phase IV *1 , a research and development project between industry, academia and government, since fiscal year 2022.

As part of the research theme of "Project Core Industry *2 ," "Contactless power transmission for completely wireless smart factories" *3 , a research team including Professor Masaya Tamura of Toyohashi University of Technology and Kondo Manufacturing Co., Ltd. (Gamagori City) has developed a contactless power transmission rotary joint *4 for industrial robots using an electric field method.

Conventional rotary joints supply power and exchange signals via a contact-type slip ring*5, which means they have the disadvantage of being susceptible to noise and wear caused by the robot's sudden movements. The newly developed electric field-type non-contact power transmission rotary joint overcomes these drawbacks and is suitable for reducing weight, making it expected to be used in a variety of industrial robotics fields.


1. Background of development

Currently, in Japan, smart factories are being developed by connecting people, machines, and systems with the Internet of Things (IoT). This has begun to produce significant results at production sites, such as improving quality by collecting quality data and reducing costs by optimizing production plans and manufacturing. While data management, system control, monitoring, etc. have been digitalized with the introduction of IoT and AI, the industrial robots that play a central role in the work still have the problem of disconnections due to continuous operation.

If contactless power transmission could be introduced to power industrial robots, not only could the above issues be resolved, but everything from data management to power supply could be digitized, improving work efficiency and productivity through 24-hour continuous operation. Now that manufacturing bases are beginning to return to Japan, this is an extremely important technology.


2. Overview of development

Industrial robots are used in many applications, such as transporting workpieces (objects to be processed) and in product assembly processes. In particular, robot hands are used for tasks such as gripping workpieces, but when the wrist axis rotates, the wiring cables connected to the hand are swung around, which can cause the cables to break. Therefore, a rotary joint is installed between the robot and the hand to eliminate the need for wiring cables, preventing breakage.

Currently, the mainstream rotary joint is the contact type using a slip ring, and power supply and signal exchange are carried out through the slip ring. However, this method has drawbacks, such as being susceptible to noise due to the sudden movements of the robot, and a shortened service life due to wear. Research and development of contactless power transmission (wireless power supply) is being carried out as a way to overcome these drawbacks, but one of the challenges is to reduce the weight of the transmission mechanism.

There are two types of non-contact short-distance power transmission methods: magnetic field and electric field. This time, we developed a non-contact power transmission rotary joint that uses the electric field method, which is highly durable and suitable for weight reduction (see Figures 1 and 2). This product is composed of two thin electrodes on the transmitting side and two thin electrodes on the receiving side, and by improving the structure and arrangement of the electrodes and the material of the rotary joint body, we have achieved not only weight reduction but also high efficiency. As a result, we have achieved a rotary joint that is 30% lighter and 10% more efficient than the magnetic field method, with a total weight of 500g and an RF-RF efficiency of 99%. Furthermore, we have built a wireless power transfer system using this rotary joint, achieving a power transfer efficiency of 73%, a DC voltage of 24V, and an output of 12W.

Details of this technology will be presented at the 2024 IEEE Wireless Power Technology Conference and Expo, an international conference starting on Wednesday, May 8, 2024, at the Obaku Plaza Kihada Hall and Mokshi Hall on the Kyoto University Uji Campus in Uji, Kyoto Prefecture.




Figure 1 Comparison of the principles and characteristics of various short-distance power supply methods




Figure 2: Rotary joint equipped with jointly developed power transmitter and receiver



3. Expected results and future developments

The non-contact power transmission rotary joint developed this time has a simple and lightweight structure, is easy to maintain, and can be manufactured inexpensively, which is an attractive feature, and it is expected to be applied to many robots involved in product manufacturing in factories. In the future, we plan to work on miniaturizing peripheral circuits such as the high-frequency power supply that generates the transmitted power and the rectifier circuit in order to commercialize this developed product.

Meanwhile, in this project theme, in parallel with the development of the above-mentioned short-distance transmission contactless power supply system for industrial robots, we are also developing a long-distance transmission contactless power supply system for in-factory sensors. If this long-distance transmission system is completed in the future, it will establish the basic technology for contactless power transmission (wireless power supply) that can be applied to various electrical and electronic devices, from robots involved in product manufacturing in factories to sensors that manage the work environment, and it is expected that this will contribute to the realization of smart factories as shown in Figure 3.


Figure 3: A smart factory with wireless technology




4. Contribution to society, local industries, and citizens

Contribution to Society

Everything from data management to power supply can be done wirelessly, improving work efficiency and productivity by enabling 24-hour continuous operation.

Contribution to local industries

Strengthening the foundation for supporting Aichi Prefecture's advanced manufacturing industry as a research and development base for contactless power transmission

Contribution to the citizens of the prefecture

As innovative industrial robots are developed and their popularity spreads, they will become a symbol of Aichi Prefecture.

5. Contact Information

[Regarding the overall Priority Research Project]

Aichi Center for Industrial Science and Technology Planning and Collaboration Department Planning Office

Person in charge: Sato, Hiwatari, Murakami

Address: 1267-1 Akiai, Yasaka-cho, Toyota City

Phone: 0561-76-8306

 

Public Interest Foundation for Science and Technology Collaboration, Knowledge Hub Priority Research Project Management Department

In charge: Shinjo, Yoshida, Murase

Address: 1267-1 Akiai, Yasaka-cho, Toyota City

Phone: 0561-76-8380

 

[About this development]

Toyohashi University of Technology

Person in charge: Public Relations Section, General Affairs Division, Okazaki and Miyata

Address: 1-1 Hibarigaoka, Tenpaku-cho, Toyohashi City

Phone: 0532-44-6506

 

Kondo Manufacturing Co., Ltd. Koda Factory

Person in charge: Mechatronics Equipment Sales Division Sales Section Manager Ono

Address: 11-1 Fukazo Ipponki, Koda-cho, Nukata-gun

Phone: 0564-65-0428

 

 

【Glossary】

*1 Aichi Knowledge Hub Priority Research Project

This is a joint research and development project between industry, academia, and government that aims to solve problems faced by major industries in the prefecture, develop and commercialize new technologies, and provide new services through open innovation that utilizes research seeds from universities and other institutions, with the Aichi Knowledge Hub, a research and development center that supports high-added-value manufacturing, at its core. The project carried out the "Focused Research Project I" from 2011 to 2015, the "Focused Research Project II" from 2016 to 2018, the "Focused Research Project III" from 2019 to 2021, and will begin the "Focused Research Project IV" in August 2022.


 

Overview of the "Fourth Phase of Priority Research Projects"

Implementation period

From 2022 to 2024

Participating organizations

15 universities, 7 research and development institutes, etc. 88 companies (including 59 small and medium-sized enterprises)

(As of March 2024)

Project name

Core Industry Project

・Project DX

・Project SDGs

 

*2 Core Industry Project

overview

We will work on technological development that will contribute to the further advancement of Aichi's core industries, which continue to lead the world and create the future.

Research theme

[Research and development field] Automotive, aerospace, and other mechanical systems (hardware)

1. Contactless power transmission for completely wireless smart factories

② Innovative materials development combined with MBD to realize ultra-efficient electronics

[Research and Development Field] Highly efficient processing and 3D printing

3) Innovation in large jigs for manufacturing aircraft parts through the evolution of CF-HM metal 3D modeling technology

④ Creating value and innovation in the manufacturing field through the advancement of additive manufacturing technology

[Research and Development Field] Next-generation materials, analysis and evaluation

⑤ Establishment of a 3D visualization method for next-generation molecular design of coatings/topical agents

⑥ Construction of an advanced visualization and measurement platform for realizing a carbon-neutral society

⑦ Development of technology and equipment for detecting coliform bacteria using artificial siderophore technology

⑧ Development of fiber recycling technology and effective utilization methods for high-performance composite material CFRP

9. Research and development of environmentally friendly building materials using hollow nanoparticles

Participating organizations

7 universities, 3 research and development institutes, etc. 35 companies (including 22 small and medium-sized enterprises) (as of March 2024)

 

 

*3 Contactless power transmission for completely wireless smart factories

overview

In order to achieve the goal of creating smart factories, we will develop in parallel a contactless power supply system for industrial robots, which uses short-distance transmission, and a contactless power supply system for sensors in factories, which uses long-distance transmission.

Research Leader

Masaya Tamura, Professor, Toyohashi University of Technology

Business Leader

Kondo Manufacturing Co., Ltd. Managing Director Yasumasa Kondo

Participating Institutions

(In alphabetical order)

[Companies]

Kondo Manufacturing Co., Ltd. (Gamagori City), Comex Co., Ltd. (Koda Town, Nukata District), Sohoade Co., Ltd. (Okazaki City), Power Wave Co., Ltd. (Toyohashi City), Murata Manufacturing Co., Ltd. (Nagaokakyo City, Kyoto Prefecture)

[University]

Toyohashi University of Technology (Toyohashi City)

[Public research institutes]

Aichi Industrial Science and Technology Center (Toyota City), Science and Technology Foundation (Toyota City)

 

*4 Rotary joint

A rotary joint that transmits electricity and signals.

 

*5 Slip ring

It is divided into a stationary body side (stator) and a rotating body side (rotor), and the stator has brushes.

A rotor with a ring structure that transmits power and electrical signals from a stationary body to a rotating body.

Rotating parts.

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