Connecting web-based IoT devices to a cloud-based manufacturing platform

Connecting Web-Based IoT Devices to a Cloud- Based Manufacturing Platform

Borja Ramis Ferrer, Wael M. Mohammed, Enbo Chen, Jose L. Martinez Lastra {borja.ramisferrer, wael.mohammed, enbo.chen, jose.lastra}@tut.fi

Tampere University of Technology, 33720 Tampere, Finland

Abstract— The Internet of Things (IoT) considers interconnected things e.g., devices that consumes web services through the internet. Such kind of devices may vary from smart phones, smart TVs, medical devices or industrial devices. Thanks to the development of the ICT field, many standards supports the existence of the IoT devices: HTTP (Hypertext Transferring Protocol), MQTT (Message Queue Telemetry Transport), and EtherCAT, among others. The challenge is to allow these devices to communicate with cloud applications wherein the mismatch of communication protocols may occur. In this context, this research work presents an approach for connecting industrial Remote Terminal Units (RTUs) with the Cloud Collaborative Manufacturing Networks (C2NET) project cloud-based platform for publishing the factory shopfloor data. In this manner, the C2NET platform exploits data that is generated by industrial equipment for further actions, such as the optimization of production plans. The presented approach is tested within the deployment of web-service enabled controllers in a real industrial case known as the FASTory line.

Keywords— Industry 4.0; cloud-based platform; internet of things; web services; cyber-physical systems.

I. INTRODUCTION

The term Industry 4.0 (I4.0) or the fourth industrial revolution, is a term that emerged during the past few years for referring to the implementation of systems that permit the management, maintenance and development of the whole value chain processes, which are executed by manufacturing systems [1]. The I4.0 is linked with the concept of the internet of everything because one of the key concepts for implementing systems aligned with such concepts is the connectivity of any resource that has an implication in the value chain. In fact, internet of things (IoT) or the industrial internet are also frequently used in this scope. To achieve such kind of interconnection of things, such as machines, software components, embedded devices and sensors, it is required to employ new Information and Communication Technologies (ICT) based solutions. ICT permit engineers not only to connect to resources involved in value chain processes, but also to collect useful information that may be used for monitoring the performance and efficiency of manufacturing systems.

In this context, the ongoing Cloud Collaborative Manufacturing Networks¹ (C2NET) project is working towards the development of a cloud-based platform for controlling and supervising the interactions of parties deployed in

1 http://c2net-project.eu/

manufacturing supply chains. In other words, the C2NET platform enables the interconnection and collaboration between suppliers, manufacturers and customers in order to enhance the efficiency of manufacturing. Although the discipline of collaborative networks (CNs) [2] is prior to the Industry 4.0 emergence, both are aligned in the sense that such industrial revolution requires systems to collaborate which is achievable through CNs. The collection of data generated from heterogeneous data sources is one of the major challenges to realise the I4.0 [3]. The fact is that interconnectivity of multiple sources that are manufactured by different vendors and employ dissimilar protocols obstructs the implementation of trivial message exchange. Thus, software engineers develop ICT- based solutions that are able to transform data in common formats that may be understood by interested parties.

This research work presents an approach for connecting web-based IoT devices to a cloud-based manufacturing platform i.e., the C2NET platform. This is the first step towards the manipulation of data generated by systems involved in supply chains for enhancing the execution of manufacturing processes. Basically, once the data that is generated at factory shop floor can be pushed to the cloud-based platform, implicit information may be concluded and, then, process may be optimized. As described in further sections of the manuscript, the implemented approach involves the deployment of industrial-based IoT devices with web service enabled functionalities. This permits the remote control and monitoring of manufacturing process as well as the consumption of events that are triggered at the shop floor level of factories.

The rest of the paper is structured as follows: Section II presents the present situation and practices in the industrial automation domain, including cloud-based applications, IoT devices and the current technologies, tools and standards. Then, Section III presents the approach for connecting web-based IoT devices to a cloud-based manufacturing platform i.e., the C2NET solution. This research work demonstrates the implementation of aforementioned approach, through a real case scenario, in Section IV. Finally, Section V concludes this manuscript.

II.STATE OF THE ART

A.Cloud-based applications

The development of collaboration networks and platforms [2], [4] is a trend on recent projects, such as the C2NET project

that works towards the implementation of platforms that integrate different and remote organisations. In this scope, not only the information is pushed and stored in the cloud, but also such kind of applications that, in turn, can be used or downloaded from the cloud.

Conceptually, having information and tools in the cloud assures efficient collaboration process and easy information access without limitation of physical location and devices [5].

To face the integration challenge for IoT and rapid manufacturing customization for industrial systems, cloud- based platform is playing a significant role to adapt to current manufacturing systems.

C2NET (Cloud Collaborative Manufacturing Networks) aims on developing a cloud-based platform for collaboration and optimization of process in industrial supply chains [6].

There are four main components in C2NET. Firstly, the Data Collection Framework (DCF) collects data from shop floor of factory throughout hubs i.e., the IoT Hub and the legacy Hub.

Secondly, the Optimizer (OPT) optimizes manufacturing and logistics assets. Thirdly, the Collaboration Tools (COT) provides support to the collaborative processes of the supply network. Fourthly, the User Collaborative Portal (UCP) provides user interfaces for application like mobile and web application [6]. All these components will achieve to boost business efficiency and effectiveness of SMEs (Contemporary Small and Medium-sized Enterprises), such as monitoring productions and auto-adaptive production plans.

There are also other projects and research works of cloud- based application. For example, the SAP Cloud Platform² is a business applications platform deployed on the cloud to build, extend, integrate and accelerate business application. It promises to decrease in app dev costs, development time and total cost of ownership in long term. Furthermore, the research work described in [7] proposes a cloud-based platform offering supply chain efficient inventory management as a service. The offered service aim on saving ordering costs and shortage costs as well as managing inventories efficiently.

B.Web-Based Industrial Devices for the Industry 4.0

The devices that are nowadays employed at manufacturing environments are the result of a continuous evolution of previous devices. This can be appreciated along the different stages of the industrial evolution. It was in the late 60s when first Programmable Logic Controllers (PLCs) started to be deployed in production systems for controlling processes following the principles of distributed systems [8]. Since then, new versions of PLCs, PCs and other types of industrial controllers have been deployed at factory shop floors for controlling and monitoring manufacturing processes.

Furthermore, the emergence of the industrial Internet of Things (IoT) demands the inter-connection of machines throughout large-spanned networks, mostly the Internet, so that the industrial equipment can be remotely controlled and monitored.

The current fourth industrial revolution, or Industry 4.0 [9], focuses on the integration of Cyber-Physical Systems (CPSs)

2 https://cloudplatform.sap.com/

3 http://www.inicotech.com/index.html

[10], [11]. In this context, small sized embedded devices may be used for interconnecting software components and machines. In the scope of the Industry 4.0, new embedded devices demonstrated to have more computation power of their predecessors. This enhancement, in combination with a quantitative enhancement of industrial operations performance, allows engineers to add more and new functionalities that can be handled by devices [12]. Then, connectivity, storage and exposure of industrial operations to both internal and external users is now possible. Basically, these are features that CPS must provide to the smart environments that are implemented for realising the Industry 4.0 concept [13]–[15].

For example, as presented in [16], Remote Terminal Units (RTUs) are industrial controllers that allow the implementation of the service oriented architecture paradigm [17] in order to control and monitor operations at shop floor level.

Conceptually, RTUs may act as a gateway between industrial equipment i.e., machines and systems deployed at higher levels of manufacturing systems e.g., SCADA systems. As a commercial example, the smart RTUs of INICO Technologies Ltd.³ e.g., implement the Device Profile for Web Services (DPWS) technology for providing aforementioned service functionality. One of the powerful benefits of this type of devices is the remote access characteristic, which permits users to configure, program and invoke operations with an internet connection as a unique requirement.

Moreover, there are other powerful IoT devices that, although emerged as an alternative for multiple purposes out of the industrial domain, can be expanded and/or modified in order to use them for within e.g., manufacturing systems’ equipment.

For example, among others, Raspberry Pi⁴ or Arduino⁵ are cheap devices that may perform tasks required in industrial environments as e.g., the ones described in [18]–[21].

C.Technologies, tools and standards for web-based solutions in the industry

This research work describes an approach for integrating IoT devices with a cloud-based platform. Due to the advances on ICT, software engineers can currently choose in-between a large set of standards that permit the implementation of web- based solutions. For example, these standards may be used for structuring messages of devices, transporting information from point-to-point or enhancing the security of platforms. The objective of this sub-section is to present briefly some of the technologies, tools and standards that are considered in the implementation of this research work.

Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributing and collaborating information on World-Wide-Wide web global network since 1990 [22]. The HTTPS (Hyper Text Transfer Protocol Secure) is a secure version of HTTP that communication are encrypted by Transport Layer Security (TLS) [23]. Moreover, the Secure Sockets Layer (SSL) [24] protects against man-in-the-middle attacks. Fundamentally, the HTTPS is the protocol which is

4 https://www.raspberrypi.org/

5 https://www.arduino.cc/

widely used for secure interaction between cloud platform and web-based devices [25].

Furthermore, MQTT⁶ (MQ Telemetry Transport or Message Queue Telemetry Transport) is a lightweight publish- subscribe-based protocol on top of the TCP/IP protocol.

Compared to HTTP, MQTT has some advantages, such as small code footprint, low bandwidth required, selectable quality of service and multiple distribution models (one to one, one to many, one to zero, etc.) [26]. Based on these features, MQTT mainly supports Facebook messenger⁷, and IoT platform (AllSeen⁸, Azure IoT⁹, Thing-Worx ¹⁰ etc.) and other applications on wireless networks with unreliable bandwidth and connections [27].

The W3C standard WebSocket is a full-duplex communication protocol over TCP connection which implements HTTP handshake mechanism. It is usually implemented for real-time communication between web client side (browser and mobile phone) and web server side [28].

On the other hand, the aforementioned protocol supports several data formats such XML (Extendable Markup Language) and JSON (JavaScript Object Notation). According to [29], JSON is the most common open-standard data format for asynchronous communication between a browser and a server nowadays. It is easy to convert from Javascript into JSON for transfers to server and vice versa. besides, it is based on a subset of the JavaScript Programming language [30].

Moreover, REST (Representational state transfer) [31] is an architectural style for interoperability, simplicity, scalability and modifiability of web service. Now, more and more Application Programming Interfaces (APIs) are REST- compliant for realizing distributed systems and are more and more important in the field of Cloud Computing, Internet of Things, and Micro-services [32].

Finally, the implementation of solutions as the one presented in this research work, must consider that the machines at shop floors connected to distributed control networks may employ different types of fieldbus protocols.

Therefore, the controllers that are attached directly to industrial equipment require the customization of their physical interfaces in order to perform a direct connection with industrial equipment. In this way, protocols as e.g., Modbus¹¹ or Profibus¹² can be used for the exchange of messages between controllers and machines. On the other hand, devices can be connected to higher-level networks throughout gateways which act as an interface between machines and Ethernet-based networks e.g., EtherCAT¹³. In this way, the common Ethernet ports are the common interface that IoT devices might use.

III.INTERNET OF THINGS DEVICES INTEGRATION

As mentioned previously, the web-based enabled devices a.k.a. IoT devices allow seamless and real-time communication throughout the internet. These devices may be configured to

6 http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html

7 https://www.messenger.com/

8 https://allseenalliance.org/

9 https://azure.microsoft.com

10 https://www.thingworx.com/

communicate with the controller or orchestrator for providing specific and required features. This case is not always applicable because the variation in the communication protocols. This research work presents a solution as third-party application for binding different protocols such as the ones presented in previous section. This application is expected to i) bind the shopfloor of manufacturing enterprises throughout the C2NET IoT hub and ii) to increase the privacy of the company since the application can work as a controlled gateway. Then, this section presents an approach for binding industrial devices for providing the sensors readings to the DCF of the C2NET platform. The architecture of the proposed solution is presented in the first subsection. Afterwards, the second subsection illustrates the interactions between parties.

A.Components Architecture

The complexity of the connection between IoT devices and the DCF can be simple if both components employ the same protocol. However, vendors tend to harmonize their own products. As an example, the INICO Technologies Ltd.

devices¹⁴ use RESTful and SOAP messages for publishing the data; others, like Beckhoff devices, use EtherCAT. Each vendor provides the compatibility options along their product.

However, the problem appears if the factory shopfloor employs two different devices from two different vendors. This incompatibility in the communication protocol creates a challenge to bind the IoT device at the factory shopfloor within the DCF.

In the C2NET project, the IoT devices are included in the architecture of the platform since the factories’ shopfloor publishes data that might be used for optimization of production plans. Fig. 1 shows the components diagram of the IoT data collection process. As appear in the figure, the DCF is represented as a cloud application. First, it contains the Resource Manager (RM) for managing data resources. Then, the Data Identification and Transformation (DIT) manipulates and prepares the uploaded data to be inserted in the C2NET databses following the Standard Tables (STables) schemas.

Besides, the DCF triggers event regarding the data that it receives. The user can configure these events during the configuration phases of the IoT resources. In this context, the Low Level Complex Event Processing (LLCEP) component detects the changes in the received data before persisted in the Database.

Furthermore, the DCF is connected to the data hubs via the Publish/Subscribe Messages Queue Broker (PSMQB). This broker uses the WebSocket standards for assuring two ways communication with the hubs. The PubSub broker is introduced by the C2NET architecture in order to allow supply chain companies to share the needed data. For example, such data can consist on sensor readings from the shopfloor that are served via IoT devices. This type of data is generated as short messages

11 http://modbus.org/

12 http://www.profibus.com/

13 https://www.ethercat.org/default.htm

14 http://www.inicotech.com/

which contain the minimal overheads. On the other hand, the company shares the Enterprise Resource Planning (ERP) data, which is known as legacy data. ERP data may be formed by orders, plans, offers, etc. that the company stores in local repositories. This data could be large which WebSocket could serve without any problems. Besides the size problem, the WebSocket allows full duplex communication and it employs the same security implementation of the already-available HTTP connection. In this matter, the C2NET implements the TLS protocol for ensuring a secured connection between the server and the client. The same implementation is used for both clients using web browser connection or hub that uses WebSocket connections.

Fig. 1 IoT devices Gateway involvement in the C2NET architecture

Until this point in the architecture, the aforementioned components are part of the C2NET platform and they are deployed in the cloud. The other components are deployed on the company side. Starting by the hub, the C2NET provides the users to use their own data hub. In this example, FiWare¹⁵ is used for building the IoT Hub. In the C2NET vision, the hub connects the data resources in the company premises to the DCF in the C2NET. The FiWare IoT hub uses the MQTT protocol for communicating with the IoT devices. On the other hand, the devices that are used in the factory shopfloor uses the RESTful. This created the need for inserting a binding application that binds the IoT devices and the IoT hub since the communication protocol is different between them. The concept of the IoT devices gateway includes the virtualization for the IoT devices.

B. Interactions

As the gateway allows the IoT devices and the IoT hub to communicate even though, the used protocols are different. As Fig. 2 depicts, the interaction starts with the user configuring the IoT hub in the DCF in the C2NET platform via a web-based

15 https://www.fiware.org/

interface. This configuration includes adding the IoT hub and adding properties for the IoT hub. In this context, the DCF virtualises the IoT devices that are connected to the hub. Each device is considered as a data resource. Then, the DCF sends this configuration to the hub via the PSMQB.

Fig. 2. IoT devices interactions

Afterwards, the IoT hub extracts the needed configuration that is related to the IoT Devices Gateway. It is important to mention that the IoT hub could be connected to device that supports the MQTT protocol. In this case, the IoT hub communicates directly to the IoT device since the protocol is the same. However, in this implementation, the configuration goes to the IoT Device Gateway. Fig. 3 shows the configuration for the Gateway. As depicted, the configuration includes IoT devices accessibility, the event alias that is required by the user and connectivity information with the IoT hub. In this approach, the connection with the IoT hub uses the MQTT protocol for exchanging the data. This appears as topics in the configuration where the hub subscribes to or publish on these topics.

Fig. 3. IoT devices Gateway configuration

Once the shown configuration reaches the IoT Devices Gateway, a REST request is sent to the IoT Device to retrieve their own description. This description is SWAGGER 2.0 API¹⁶ description that allows the gateway to exploit the IoT device services. In this matter, the IoT device Gateway subscribes to the events that are needed. In this case, it is the temperature events. At the same time, the IoT Devices Gateway creates a virtual device representing the actual devices including their events. Finally, once an event is triggered by the IoT Devices, the IoT Device Gateway receives the event and create an MQTT message according to the configuration that has been set before.

The creation of the MQTT messages includes the identification of the topic that is reserved for the event and the payload information that needs to be sent to the IoT Hub. Then, the IoT Hub reforms the message to suit the implementation of the WebSocket communication with the DCF.

IV.DEPLOYMENT ENVIRONMENT

The FASTory line is a production line located at Tampere University of Technology that is used for both research and education purposes. Such production system is composed by a set of ten alike workstations that include one robot and one conveyor segment. In addition, the production system includes a manual workstation wherein a human may operate and a workstation that is in charge of loading and unloading raw material into the pallets that flow throughout the system. In fact, besides the inner conveyor segments, there is another segment per workstation that may route pallets out of the cells in order to bypass them. The current FASTory line is shown in Fig. 4.

Fig. 4 The FASTory line

This production line was used before for assembling mobile phones. However, the end effectors of the SCARA robots were changed for pens and, now, the product is a drawing of a phone.

Each robot is capable of drawing three different parts of the phone: screen, keyboard and frame. In addition, each part can be of different type. This allows the order of more than 700 different variants of mobiles.

Furthermore, a set of web-service enabled RTUs have been deployed the production line for remote control and monitoring of processes. More precisely, the selected RTUs are the Inico

16 http://swagger.io/

17 http://www.inicotech.com/s1000_overview.html

Technologies Ltd. S1000 industrial controllers¹⁷. Each workstation includes a RTUs per each conveyor and robot. In addition, energy analyser units (i.e., E10¹⁸) are also connected for analysing the energy consumption of each cell. The deployment of such devices has been used for several research works as e.g., [33]–[35]. An example of such device deployment is shown in Fig. 5, which shows the lower part of the working cells. The IoT Devices are highlighted with red rectangles.

For this experiment, the controllers host different services that can be invoked through any kind of REST client via HTTP.

Particularly, the devices include services for performing transfer and draw operations. Meanwhile transfer operations permit routing the pallets from one conveyor segment to another; draw operations are used for ordering robots to draw certain type of mobile phone variant.

Fig. 5 Deployment of INICO Technologies Ltd. devices in the FASTory line

V.CONCLUSION

This research work resulted in the interconnection of IoT- based devices to a supply chain cloud-based platform within an approach to be exploited by the C2NET project solution. The challenge was to connect IoT devices with different communication protocols to the platform. As presented, the adopted approach fulfilled the requirement for connecting such kind of devices. This requires two third party mediators i.e., IoT hub and IoT Devices Gateway because the protocols between the cloud platform and IoT devices are not unified. The reason behind using the two mediators is that the hub is part of the C2NET architecture and it is developed to serve MQTT-based devices. On the other hand, the use-case uses RESTful-enabled devices. This required to develop a gateway for connecting these devices. This gateway could be included in the architecture of the project in the future.

As well, for the future work, a study case will be conducted for researching the proper communication protocol for such a requirement. Currently, the employment of IoT devices is

18 http://www.inicotech.com/e10_overview.html

growing meanwhile the manufacturing systems are evolving.

This study will lead to improved version of the approach for connecting the IoT devices, using the research work reported in this article. In many cases, some of the manufacturing systems requires real-time data exchange depending of the industry type. This issue could be resolved in the future work by using different protocols or adopting different techniques.

ACKNOWLEDGMENT

The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement n° 636909, correspondent to the project shortly entitled C2NET, Cloud Collaborative Manufacturing Networks.

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