Augmented Reality for Industry 4.0: Architecture and User Experience Andreas Jakl, Lucas Schöffer, Matthias Husinsky and Markus Wagner Institute of Creative Media Technologies, St. Pölten University of Applied Sciences, Austria Email: [first].[last]@fhstp.ac.at Abstract—For Industry 4.0 – the Internet of Things (IoT) To provide guidance for these challenges, we have developed in an industrial manner – new methodologies for support and two prototypes: “Web-Based AR Remote Support” and “Real collaboration of employees are needed. One of these method- Time Machine Data Overlay”. ologies combines existing work practices with support through technologies like Augmented Reality (AR). Therefore, usability concepts for appropriate hardware as well as the data transfer II. S TATE - OF - THE -A RT FOR AR IN I NDUSTRY need to be analyzed and designed within applicable industry standards. AR applications for industry got serious research attention In this paper, we present two different use cases (Real-Time since the early 1990’s. [2], [3], [4] provided general surveys on Machine Data Overlay and Web-Based AR Remote Support) in AR technologies and frameworks. For industry, AR assistant the context of collaboration and support of employees. Both use systems are successfully applied to support humans in training cases are focusing on three main requirements: 1) Effective data for or during assembly and maintenance processes, as well as transmission; 2) Devices certified for industrial environments; quality inspection. By decreasing the mental load, the human and 3) Usability targeted towards industrial users. Additionally, we present an architecture recommendation for combining both error rate decreases while speed is increased at the same use cases as well as a discussion of the benefits and the limitations time [5], [6], [7], [8]. of our approaches leading to future directions. The advantages of mobile AR for visual analytics for in- dustrial IoT (IIoT) data in a networked environment have been Index Terms—Augmented Reality Architecture, Collaboration, widely recognized [9], [4], [10], [11]. AR technologies provide Interactive Visualization, Real-Time Data Display, Industry 4.0 means to visualize and auralize cyber-physical production systems (e.g., machines and their digital twin [12]) on-site I. I NTRODUCTION in a context-sensitive way [13], for collaborative robotics [14] and during planning processes [7]. UX design and ergonomics Many current Augmented Reality use cases target com- for humans is another topic of great importance for successful mercial and industrial areas. These have the biggest market implementation in the field [15], [16]. potential of the enterprise segment according to the forecast Remote support and collaboration in industrial settings by Goldman Sachs [1]. As such, companies are using pilot have been discussed for example in [17], [18]. The previous projects to evaluate both the real-world usability, as well as work indicates the demand for AR in industrial scenarios; it the integration into existing work practices. presents concepts and solutions for specific issues. However, Typical scenarios involve remote assistance and monitoring. we found a gap in research concerning the architecture of such These use cases yield a very measurable return on investment, solutions – especially while still maintaining a good overall thereby easing the creation of a business case to offset the user experience. research and development costs. Sending specialized engineers to remote locations to fix issues with broken machines is more III. O UR A PPROACHES expensive than developing and providing means for efficient Based on the requirements of two Industry 4.0 companies, remote collaboration using an on-site generalist, interacting we have developed two separate prototypes to address their with the remote specialist. real-life issues. In this section, we first summarize the indi- However, the main challenge is designing and creating a vidual learnings regarding the challenges highlighted in the suitable software architecture and user interface. Thus, we introduction. Then, we abstract the architecture to provide our explicitly focus on the following in this paper: recommendations for a generic framework, following best- 1) Efficient data transmission for mobile scenarios, involv- practices learned through the individual projects. ing collaboration and / or real-time machine data display. The first prototype allows placing holographic dashboards 2) Software should run on durable and cheap devices that in the real world to visualize real-time machine data retrieved are certified for industrial environments. Most current through industry standard protocols (Real-Time Machine Data AR devices are targeted for home or entertainment use. Overlay). The second enables a remote expert to draw support 3) Usability targeted towards industrial users, to reduce annotations on the AR camera view of an on-site generalist required training time to a minimum. (Web-Based AR Remote Support). 38 Augmented Reality for Industry 4.0: Architecture and User Experience In the scenario of an untethered MR headset in a factory, data transmission quality and speed can be an issue. As such, a relay server has two advantages: it acts as an additional security layer, as there is no need to expose the OPC UA endpoints to mobile clients in the wireless network. Moreover, it only sends the necessary data to the mobile client to reduce data traffic. Dürkop et. al [20] analyzed the overheads and data transfer rates of industry protocols with cellular network protocols. Even though the binary variant of the OPC protocol was the most efficient of the analyzed machine-to-machine protocols, it still had a rather large protocol overhead. To reduce this overhead, we added the intermediate Node.js server, as we Fig. 1. Real-time machine data holographic dashboard showing the temper- could strictly isolate the information required by the head ature of a pipe. mounted display. 2) Devices / AR Headset: The most critical part of the application runs within the actual headset. On the technical Company IT AR Headset side, it needs to register with the server and update its internal database of accessible OPC Node IDs. These are shown in OPC UA Manager Interaction Handling menus, allowing the user to freely place dashboards in the real Server Persistence Manager world. Each dashboard mainly needs to store the connected Virtual World Node ID and the current dataset in addition to a world anchor. … To be used within industry environments, careful checks Data Placeable OPC IDs: 123 Physical World need to be performed if the headset fulfills necessary safety Live Value: 25°C Anchors World Anchor standards. The HoloLens already complies to several stan- Machine Data Chart Placeable dards: ANSI Z87.1, CSA Z94.3 and EN 166 [21]. OPC IDs: 125, 126 Historical Values: 42°C, 44°C, … 3) Usability / Physical World & Persistence: A key con- World Anchor sideration of AR in industrial scenarios is the structure of the real-world environment. The underlying computer vision Fig. 2. Possible architecture of an Augmented Reality app, overlaying real- algorithms from Google ARCore and Microsoft HoloLens time machine data to actual machines. use a Simultaneous Localization and Mapping (SLAM) based approach to create a geometrical reconstruction of the world while at the same time estimating camera localization. Even A. Real-Time Machine Data Overlay though the commercial algorithms are not available, a state- In Fig. 1, a user placed an information dashboard on a pipe. of-the-art open source implementation is ORB-SLAM [22]. Data is retrieved from an OPC Unified Architecture (OPC This is a good reference for understanding the underlying UA) server. The HoloLens app can show a list of available algorithms and helped us optimizing the use cases. One of the nodes, whose dashboards can be placed on real-world struc- main steps is detecting key-points in the live camera image. tures. Interaction is performed with the standardized HoloLens Established approaches detect corners based on the contrast in select gesture using two fingers. The user interface is mainly circular surroundings of individual pixels [23]. composed of Holographic Buttons from the MR Toolkit [19]. Based on this limitation, AR applications should not en- These are built with semi-transparent elements, which make courage placing dashboards on feature-less walls (e.g., single- it easier to retain the view of the real world below the virtual colored with little structure). A better approach is directly objects. The location of placed items persists across sessions. placing the items on machines, typically having a more The overlay of the most important information directly complex structure. In addition, early research from Boeing [5] on the machines in a manufacturing hall allows identifying recommends placing instructions close to the work area. potential issues with a quick glimpse. The main challenge is The world anchor is managed through the Microsoft MR combining usability with efficient data transfer (see Fig. 2). toolkit and essentially forms the connection of the virtual The architecture is based on three separate parts: 1) Com- objects to the physical world. Nevertheless, a persistence man- pany IT containing data storage and processing servers; 2) ager component within the app needs to ensure the persistence Mixed Reality (MR) headset handling user interaction and data across sessions, and potentially also across multiple users visualization (VIS); and 3) Actual physical world anchoring simultaneously viewing the same scene with different headsets. of VIS objects. To avoid instability, virtual objects are recommended to be 1) Data Transmission / Company IT: Common interoper- placed at a maximum distance of 3 m from an anchor [24]. ability standards for machine data monitoring are OPC UA Special attention needs to be paid to the legibility of the and Message Queuing Telemetry Transport (MQTT). dashboards. Research shows that diegetic and spatial user 39 Augmented Reality for Industry 4.0: Architecture and User Experience 1) Devices & Installation: In our scenario, the customer Remote Support AR Assistance Client Virtual World … is willing to install new software on his mobile device, if it Interaction Handling Support Annotation Interaction Handling helps him to get quick and efficient support. However, the Drawing World Anchor Company IT Support Annotation effort for that installation has to be low. After installation, the Persistence Manager Drawing World Anchor app should be usable without the need for configuration. Server The supporter was defined as an expert with special knowl- Physical World Anchors edge on certain machines or technical devices. He maybe ICE / Connection Setup travels a lot (e.g., doing installations). There’s a chance that he has no possibility or time to install software when the customer calls for quick help. Fig. 3. Possible architecture of a web-based AR support system. To satisfy these requirements, we designed a system where the supporter gets an individual hyperlink (via E-Mail) from the customer. After opening the link, the supporter receives interfaces are the most natural and preferred metaphors for the real-time video stream from the customer within his web virtual scenarios [25]. However, a limitation of many of to- browser. There, he can add visual feedback, environmentally day’s headsets is the rather low display resolution (HoloLens: linked to the Augmented Reality POI. 720p [26]). With an ideal placement of dashboards 2 m away from the user (as recommended by Microsoft guidelines to 2) Data Transmission: The underlying technology for the ensure good focus [27]), small text objects easily become data transmission of the stream and the graphical annotations difficult to read. Thus, the dimension of a dashboard showing is WebRTC. WebRTC is a web standard for building peer-to- a numeric live value is 0.2 m by 0.1 m in our prototype. peer connections between two browsers or between a browser and another application that supports an implementation of To put usability first, billboard functionality is used for user WebRTC. During the stream, there is no need for an additional oriented dashboard visualization. The downside is that parts node or logical overhead in-between (e.g., a streaming server). of the dashboard might appear to be “inside” the physical object. However, due to the semi-transparent material and To establish the connection, the customer’s app automati- the deactivated occlusion with the spatial map, that effect cally registers with a signaling server and receives a session is hardly noticeable in our prototype. To optimize anchoring ID. The app then generates the individual hyperlink, which in- the virtual dashboard on the real-world object, the prototype cludes the new session ID. The customer sends that hyperlink additionally allows re-positioning through hand-based drag to the supporter (e.g., via E-Mail). By opening the hyperlink, gestures. Manual label placement allows contextual relevance the supporter’s web browser also connects to the signaling for users and avoids challenges of automated placement [28]. server. Thus, the two peers exchange their Interactive Con- nectivity Establishment (ICE) information via the signaling server and establish a direct peer-to-peer connection. Next, the B. Web-Based AR Remote Support customer streams the environment to the supporter by using The purpose of remote support via AR is that two persons the rear camera of his mobile device. At the same time, the – a customer who needs help on a certain technical problem device performs environmental understanding on the captured and a remote expert (supporter) who provides a solution on video input using ARCore, attempting to find key-points. that issue – can exchange visual information (see Fig. 3). 3) Usability & Collaboration: For drawing on a video The initial starting point is a video stream of the customer’s stream, there are two different concepts: (a) The drawings can environment. The customer shows the point of interest (POI, be integrated in real-time into the currently active stream. This describes the object where the actual problem is located) could cause inaccuracies when the customer moves the device to the supporter. In industrial environments this could be a while the supporter is drawing. (b) Pause the video stream in malfunctioning machine. AR technology allows the supporter the supporter’s browser during drawing. to give the customer interactive visual feedback (e.g., by Based on these two general approaches, the focus of the making annotations), which is anchored to the POI and stays project on accurate annotations and usage within industry in place. environments leads to approach (b): whenever the supporter For our system we identified two core requirements during performs a tap on the streamed video, the last frame freezes the conceptual phase: first, the supporter should have no need in the browser. The supporter then has the possibility to to install additional software. Second, no special hardware draw annotations on the frozen frame. At the same time, the should be required – neither from the customer nor from the customer can continue to move his phone without influencing supporter. We decided to use mobile devices (smartphones or the supporter’s view. tablets) for the customer, as these are widespread and available At the same time, a transparent plane is created as AR in industry-certified variants that can be used in environments element in the environment of the customer. By setting an like production halls. anchor (using the detected environmental key-points), the Overall, the system should be universally applicable, as well plane stays at the designated location near the POI. The as easily available for a huge potential target group. annotation will later appear on that plane. 40 Augmented Reality for Industry 4.0: Architecture and User Experience Remote Support AR Assistance Client AR Headset Interaction Handling Interaction Handling Interaction Handling Company IT OPC UA Server Persistence Manager Manager Virtual World ICE … Physical World Support Annotation Anchors Machine Data Chart Placeable Fig. 4. Possible architecture of an combined approach. On completion, the supporter confirms his annotations. hand, smartphone-based AR works on industry-ready phones, The annotation data is directly sent to the customer. There, which are easier to carry and cheaper to roll out to employees it is used to create an image texture, which is added to in service and production. Overall, implementing a common the previously generated plane. The supporter’s annotation shared persistence back-end with specialized clients for the becomes visible on the plane and is anchored to the POI. The different scenarios gives the best of both worlds. annotations appear in the customer’s environment. IV. R ECOMMENDATIONS FOR AR A PP A RCHITECTURE V. C ONCLUSION AND F UTURE D IRECTIONS These two individual use cases are tightly related to each other. Combined, they lead to a complete use case, while We presented two different use cases (see Sec. III) in the still retaining the unique architectural challenges of each part. context of collaboration and support of employees (Real- While our approach A describes the initial dashboard view Time Machine Data Overlay and for Web-Based AR Remote for live machine data, approach B then allows connecting to Support), meeting the future challenges of Industry 4.0. Based a remote expert / supporter in case issues become evident. on the two approaches and considering our lessons learned, we In Fig. 4 we show an architecture unifying both use cases. proposed a future design approach for a combined architecture It exhibits two main differences: 1) The client’s responsibil- (see Sec. IV). ity is focused only on interaction handling – allowing the Since our prototypes have only been evaluated at a very low users to add new dashboards, or to draw annotations; 2) level (non-documented discussions with domain experts), it is The persistence is centralized in the server. This creates a necessary to perform a design study [32] and evaluation [33] shared database, allowing improved multi-user support, as well for the proposed architecture. Therefore, this approach needs as a more seamless transition between both use cases. For to be designed and developed in a user-centered process [34] example, improvements suggested by the supporter could be where future system users are fully included in the evaluation immediately seen in the real-time machine data dashboards. cycle. Additionally, a usability study is needed to evaluate This centralized architecture is based on the most recent the integrated visualizations as well as the general workflow developments to share anchors between users and platforms. concept regarding industry employees. While SLAM-algorithms from researchers have already been The insights generated through our two prototypes, com- optimized for collaborative SLAM [29], commercial imple- bined with previously gathered experience of collaborative and mentations are currently also adding support for environment multi-device scenarios [35], will provide a profound base for data sharing between multiple clients (Google Cloud An- these planned further research activities. However, to cover all chors [30], Apple Shared Experiences [31]). These new APIs the new upcoming challenges for Industry 4.0 more research will be a key enabler for future improvements to our system. is needed involving the employees directly into the design and Based on the initial observations from our prototypes, we conception loop to not get overwhelming by the new created see the distinction between different specialized clients as technologies. an important factor. 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