Successful Experiment with Stabilization Technology for Wireless Communications for Manufacturing Systems

Abstract

The National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.) and Toyota Motor Corporation (TOYOTA) have succeeded in experimenting with stabilization technology for manufacturing systems using wireless communication, and to have realized a "non-stop line”. The "non-stop line" can be realized to detect the introduction of unregistered terminals by visualizing the radio, to suppress unplanned radio congestion, and avoiding sudden interference that occurs by coordinated control of different systems. This time, we have demonstrated these technologies at two operating TOYOTA plants.

Test at TOYOTA Takaoka Plant: Verification of the wireless environment real-time visualization technology developed by NICT can be carried out on the actual assembly line in operation, and we confirmed that unregistered terminals can be detected before affecting the wireless system on the production line.
Test at TOYOTA Motomachi Plant: We verified the SRF wireless platform that enables stable wireless communication through coordinated control between different wireless communication systems developed by NICT. As a result, we were able to confirm the effectiveness of this platform, such as establishing an appropriate communication route according to the degree of wireless congestion.

In the future, TOYOTA plans to gradually introduce this visualization technology to other factories in order to properly manage wireless systems at manufacturing sites. NICT will continue the demonstration experiment of this visualization technology at other TOYOTA plants, promote the research and development of the SRF wireless platform, and aim to put the stabilization technology of the wireless system to practical use at the plant.

Background

Figure 1 Image of an unregistered terminal (right) and visualization screen (left) of real-time visualization technology for wireless environment. By analyzing the information from the sensor installed in the yellow circle in the left figure, the radio wave reach range is indicated by the intensity and color, and the position of the unregistered terminal is specified.

Axis X, Y: Distance(m), Value above the circle: RSSI（Received Signal Strength Indicator)(dBm)

[Click picture to enlarge]

At manufacturing sites, the introduction of manufacturing systems using wireless communication is progressing year by year for the purpose of increasing the flexibility of production equipment in order to improve productivity, and it is expected that the number will increase further in the future. On the other hand, wireless communication technology is inseparable from personal life. At the manufacturing site, many people are working on manufacturing every day, but wireless communication associated with people such as mobile routers may unintentionally adversely affect the wireless system on the manufacturing line.

To avoid this situation, NICT and TOYOTA have been working together since 2015 to visualize the wireless environment at the manufacturing site. Figure 1 shows the result of using the sensor to visualize the range of radio waves from a terminal when a person moves around the site with a terminal that emits radio waves.

In addition, as many manufacturing systems become more wireless, there are concerns about communication instability due to interference between wireless systems and the impact on equipment operation. Since 2015, NICT has been carrying out activities of the Flexible Factory Project to promote wireless manufacturing at manufacturing sites, and by utilizing the knowledge gained through this activity, it stabilizes wireless communication by coordinated control of different types of wireless communication. We have been promoting research and development of SRF wireless platforms. In addition, in order to implement the results of research and development in society, in July 2017, we established the Flexible Factory Partner Alliance (FFPA) with companies that are highly interested in SRF wireless platforms, and have been promoting the standardization of technical specifications. Then, in September 2019, we published the technical specifications ver.1.0 for the SRF wireless platform.

Achievements

In this time, NICT and TOYOTA conducted a joint experiment on wireless system stabilization technology that supports the manufacturing site at two operating TOYOTA Plants, and succeeded in realizing a "non-stop line."

The first was to verify the effectiveness of real-time visualization technology for wireless environments, and conducted a joint experiment on the assembly line in operation at the TOYOTA Takaoka Plant (see Figure 1). This visualization technology visualizes how far the radio waves from the access point reach on the floor map on the management screen. In addition, when a wireless terminal such as a mobile router that has not been registered in advance is brought into the factory, it will be detected and an alert will be displayed to alert the administrator. From the end of 2019, we will install the necessary equipment, challenge the visualization of the entire building, and as a result of several months of effect verification, we can confirm that it is possible to visualize the radio wave range and detect unregistered terminals (see Appendix 1. for details).

In the future, TOYOTA plans to gradually introduce this visualization technology to other factories in order to properly manage wireless systems at manufacturing sites.

Figure 2 Result of experiment of SRF wireless platform.
Upper figure: Time change of delay.
Lower figure: Frequency of delay occurrence.

[Click picture to enlarge]

The second is the verification of the function of cooperative control of heterogeneous systems in the actual environment. At the Motomachi Site of TOYOTA, we conducted an experiment of the SRF wireless platform. Since this platform performs coordinated control with other wireless systems, it constantly monitors the wireless environment and dynamically selects the appropriate wireless link and communication method. In this experiment, we generated test communication in the same frequency band as that used on the production line, and evaluated the delay of this test communication (see Appendix 2. for details).

As a result, it was confirmed that the delay can be significantly reduced and the ratio of satisfying the delay of 100 msec or less can be improved to 100% by switching to the appropriate communication path under the control from the Field Manager (management server) (see Figure 2).

By guaranteeing a delay of 100 msec or less, more than 80% of manufacturing systems that use wireless communications can be operated stably. The results of this experiment demonstrated that the SRF wireless platform can be used to meet the required delay when a new wireless application is introduced into an actual production line.

By detecting unregistered terminals brought in by wireless visualization, unplanned wireless congestion can be suppressed, and sudden interference that still occurs can be avoided with the SRF wireless platform, "non-stop line" can be realized. By confirming the effectiveness of these technologies at the factory in operation, it is expected that stable operation of the manufacturing system using wireless communication technology will be possible at the manufacturing site where humans and machines coexist.

Future Prospects

In the future, NICT will gradually deploy real-time visualization technology for wireless environments to other sites of TOYOTA, and will continue demonstration experiments with the aim of putting them into practical use. In addition, regarding the SRF wireless platform, we will continue research and develop based on this experiment result, and establishment of a certification system with the aim of putting it into practical use as a platform that can utilize stable wireless communication in factories.

* A part of this work includes results of the project entitled "R&D on Technologies to Densely and Efficiently Utilize Radio Resources of Unlicensed Bands in Dedicated Areas," which is supported by the Ministry of Internal Affairs and Communications as part of the research program "R&D for Expansion of Radio Wave Resources (JPJ000254)".

Appendix

1. Real-time visualization technology for wireless environment

Real-time visualization technology for wireless environment collects and integrates beacon information from sensors for radio wave measurement, and draws the result of analyzing that information on the floor map on the management screen (see Figure 3). This technology visualizes the range of radio waves by estimating changes in radio wave strength in the floor based on beacon information collected from multiple sensors. Also, based on the BSSID information of the beacon, it is checked whether it is a registered terminal or not, and if it is an unregistered terminal, its position is specified from the signal strength (see Figure 4).

Figure 3 Functional configuration diagram of real-time visualization technology for wireless environment.
[Click picture to enlarge]

Figure 4 Management screen image of real-time visualization technology for wireless environment. The peak (yellow) of the radio field intensity on the visualization screen moves as the unregistered terminal moves upward.
[Click picture to enlarge]

2. SRF wireless platform

On the SRF wireless platform, Field Manager (management server) provides global control to coordinate radio resources between multiple wireless systems, and SRF Gateway (access point) / Device (wireless device) conducts local control to optimize communication efficiency within a single wireless system (see Figure 5). In this platform, based on the information from radio monitoring sensors, global control and local control cooperate with each other to control using channel and communication speed adaptively according to the conditions of other traffic. Consequently, this platform avoids interference in the radio link and reduces communication delay.

Figure 5 Functional configuration diagram of the SRF wireless platform.

Glossary

Smart Resource Flow (SRF) wireless platform

A system configuration for connecting a wide variety of wireless devices and equipment and operating them stably. Smart Resource Flow is a system engineering strategy that uses multi-layer system analysis to manage the smooth flow of manufacturing resources (people, equipment, equipment, materials, energy, communications, etc.). By monitoring the communication status of other applications coexisting in the same space and adaptively controlling the channel and communication speed used for communication, interference in the wireless section is avoided and communication delay is suppressed. The technical specifications of the SRF wireless platform were developed by FFPA.

https://www.ffp-a.org/news/index.html#20190924

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Flexible Factory Project

A multi-purpose wireless communication experiment project for factories in operation, led by NICT, established in June 2015 for the purpose of promoting wireless utilization in factories. Currently, in addition to NICT, 16 companies: OMRON Corporation, Advanced Telecommunications Research Institute International, NEC Corporation, Fujitsu Limited, FUJITSU KANSAI-CHUBU NET-TECH LIMITED, Sanritz Automation Co., Ltd., Murata Machinery, Ltd., Mobile Techno Corp., Panasonic Corporation, Internet Initiative Japan Inc., KOZO KEIKAKU ENGINEERING Inc., silex technology, Inc., DENSO CORPORATION, Toyota Technical Development Corporation, NTT DOCOMO INC., and PwC Consulting LLC. are joinning.

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Flexible Factory Partner Alliance (FFPA)

The Flexible Factory Partner Alliance aims to promote IoT at manufacturing sites by establishing standards, standardizing, and promoting the spread of cooperative control technology that realizes stable communication in an environment where multiple wireless systems coexist. A non-profit voluntary organization established in July 2017. As of the end of October 2020, there are nine member companies: OMRON Corporation, Advanced Telecommunications Research Institute International, National Institute of Information and Communications Technology, NEC Corporation, Fujitsu Limited, Sanritz Automation Co., Ltd., Murata Machinery, Ltd., Siemens K.K., and Telecom Engineering Center.

https://www.ffp-a.org/index.html

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SRF wireless platform technical specifications ver.1.0 issued

Technical specifications of communication standards established by FFPA to stabilize various wireless systems that are mixed and used for various purposes at manufacturing sites. This technical specification defines the functions and interfaces of the SRF wireless platform, and realizes a mechanism that allows wireless systems of various generations, standards, and manufacturers mixed in the manufacturing site to coexist and cooperate.

NICT Topics

- September 24, 2019 “FFPA Completes Technical Specifications to Stabilize Various Wireless Communication Systems Co-located in Factory Sites.”

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