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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Enabling Seamless HRC Integration: The AI- PRISM Reference Architecture</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Miguel A. Mateo-Casalí</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Josep Rueda</string-name>
          <email>jrueda@ikerlan.es</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Samuel Olaiya Afolaranmi</string-name>
          <email>samuel.afolaranmi@tuni.fi</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Jose Luis Martinez</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Lastra</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Davide Boscaini</string-name>
          <email>dboscaini@fbk.it</email>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Laura Moya-Ruiz</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Francisco Fraile</string-name>
          <email>ffraile@cigip.upv.es</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Future Automation Systems and Technologies Laboratory (FAST-Lab), Tampere University</institution>
          ,
          <addr-line>Tampere, Finland 4</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>IKERLAN Technology Research Centre, Basque Research and Technology Alliance (BRTA)</institution>
          ,
          <addr-line>Arrasate, Basque Country</addr-line>
          ,
          <country country="ES">Spain</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Research Centre on Production Management and Engineering (CIGIP), Universitat Politècnica de València</institution>
          ,
          <addr-line>Camino de Vera s/n, 46022, Valencia</addr-line>
          ,
          <country country="ES">Spain</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>This article addresses the challenges of deploying AI solutions for human-robot collaboration (HRC) in the context of industry 5.0, introducing the AI-PRISM framework as a solving proposal. This framework presents a high-level reference architecture which is designed to provide efficient and adaptive robotic systems in industrial environments, using Kubernetes clusters managed through Rancher to ensure reliability and easy maintenance and monitorization. The four tiers identified in this architecture start from the lower levels with the physical devices in the Device Tier, followed by the Ambient Network Tier to ensure that real-time communication required in any human-robot collaboration environment. The Fog Tier involves more processing capacity and resources, but keeping almost real-time responses, therefore, modules related with reasoning, perception and simulation are here. The Enterprise Tier focuses on Continuous Integration and Deployment (CI/CD), allowing to deploy components, and non real-time modules. In addition to the Reference Architecture components, the AI-PRISM Open-Access Platform is a web-based gateway, that provides stakeholders access to tools, technologies, and resources, encouraging collaboration, experimentation and testing in AI-based collaborative robotics.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Human-robot collaboration (HRC) is a prominent feature of modern Industry 5.0 applications [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
HRC technologies maintain human involvement in workplaces by leveraging robotics to alleviate
mental and physical stress. Artificial Intelligence (AI) can enhance the perception and reasoning
capabilities of robotic agents to achieve paramount performance and accuracy. However, the
deployment of AI models in industrial environments poses significant challenges, particularly in
scenarios with strict timing constraints, where models are deployed in environments with high
processing power, and results must reach actuators (cobots) immediately.
      </p>
      <p>
        To address these challenges, it is necessary to adopt architectural frameworks that allow the
correct and efficient management of IT resources, and that are able to leverage edge computing and
real time communications in an effective manner to reduce latency and ensure overall performance
[
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Besides timing constraints, the correct functioning of the system requires frequent updates of
different software components (including AI models), and at the same time,
ensure that these continuous updates do not cause any interruptions in the HRC processes. Adherence
to standards and compliance with the regulatory frameworks and industry best practices, particularly
on security and data protection, are also important aspects to consider. Moreover, the rapid
advancements in collaborative robotics have led to a wide range of physical equipment (robots,
sensors, camera, edge devices) that is available to build HRC applications. This implies that it is
important to incorporate standardized interfaces and protocols to ensure interoperability. Finally,
network and connectivity for HRC must be considered, as bandwidth optimization and proper
bandwidth management are necessary to cope with the transmission of data. As a response to these
challenges, this paper presents the reference architecture of the AI Powered Human-Centered Robot
Interactions for Smart Manufacturing (AI-PRISM) project. The AI-PRISM project is focused project is
focused on enhancing smart manufacturing through AI powered, HRC applications, and the AI-PRISM
reference architecture provides a high-level architectural representation of AI enhanced HRC systems
which can lead to more adaptive, efficient, and scalable robotic systems in industrial environments.
      </p>
      <p>Throughout section 2 the AI-PRISM Reference Architecture will be explained, detailing its parts.
Within each tier, the different modules that can be deployed and its role, justifying its position, will
be included.</p>
    </sec>
    <sec id="sec-2">
      <title>2. AI-PRISM Reference Architecture</title>
      <p>The AI-PRISM project provides a reference architecture that provides a structured solution for the
technical implementation. This architecture offers a framework or guidance for the technical elements
and the internal communications of AI-PRISM HRC applications, and a framework for the concrete
implementation of the different demonstrators and project industrial scenarios or pilots. One of the
most important aspects of the architecture is the definition of connections between hardware
components, communication networks, execution environments and software components. Figure 1
provides a detailed breakdown of each software component, including an in-depth description of the
functional components mapped to the AI-PRISM reference architecture (AI-PRISM-RA) and
indications of anticipated input and output interfaces.</p>
      <p>
        The AI-PRISM-RA is based on architectures and reference models established under the
ISO/IEC/IEE 42010 standard for system and software engineering architecture descriptions [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. This
standard provides different definitions and structures for complex architectures. An illustrative
example of the use of this standard is the Industrial Internet Architecture Framework (IIRA), as well
as other relevant reference architectures and models for digital manufacturing [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ].
      </p>
      <p>The AI-PRISM project elaborates its architecture around four different tiers, the Edge tier,
Environment tier, Fog tier, and Enterprise tier. Each of these tiers encompasses different hardware
components providing computational resources to execute the different software components of
AIPRISM HRC applications. AI-PRISM adopts a distributed cluster architecture, in which edge devices
and other computational resources are treated as independent Kubernetes clusters [5], managed
centrally by a cluster management and control component. This component facilitates the installation,
management and monitoring of clusters and containers, offering an easy-to-use interface to discover
and install components and applications from the AI-PRISM repository. This Kubernetes based
independent cluster architecture not only enables continuous updates using Continuous Integration
and Delivery (CI/CD) infrastructure, but it also provides a layer of reliability in case of failure as it is
possible to move workloads from one cluster to another as a fallback mechanism. Furthermore,
AIPRISM components are independent microservices. With this design, modules can be tested prior to
deployment and, in case of failure, can be easily reverted or restarted without compromising the rest
of the modules.</p>
      <sec id="sec-2-1">
        <title>2.1. Edge Tier</title>
        <p>The Edge Tier groups all the different devices that play a role in the interaction with the ambient, or
human-robot collaboration environment. It includes sensors, robots, other manufacturing equipment,
and the controller that commands them. Each device or set of devices is coupled with a controller.
This conjunction of devices and their controller are meant to perform a task, for example, a couple of
cameras and their controller performing a 3D reconstruction of the environment.</p>
        <p>Within this tier, the follwing modules can be found:
(i) Ambient and Human Sensing Infrastructure, which encompasses all the equipment capable
of perceiving the environment, such as cameras, sensors, and robots equipped with
sensors.
(ii) Base Hardware, covering all non-sensorial hardware like actuators and robots, as well as the
hardware that will host the execution of controllers to direct all the mentioned devices in
this Device Tier.
(iii) ROS Framework includes the set of modules facilitating communication among other
modules based on ROS. Additionally, it's crucial to consider two additional components
which are integrated into the ROS framework using ad-hoc modules: a. Non-ROS
Modules, which operate independently of the ROS Framework and ooffer adiverse range
of complementary functions.
b. Programmable Logic Controllers (PLCs) in the industrial network. These PLCs
are programmable logic devices that play a pivotal role in industrial automation by
managing communication and controlling equipment within manufacturing
environments, contributing to the seamless operation of the overall system.</p>
        <p>All these modules and infrastructure, along with ROS Framework and Non-ROS modules,
constitute the "Device Tier", are managed through the central cluster management component, built
on top of Rancher [5], an open-source tool designed to supervise computational unit clusters in
Kubernetes. Users can deploy containers on individual units, assign workloads to an entire cluster,
and monitor performance through an intuitive interface provided by Rancher. It's worth highlighting
that, by allocating a workload to a device cluster, any residual computational capacity can contribute
to additional tasks, enhancing both performance and reliability compared to non-clustered
distributions. While the primary function of each device is to manage its specific set, it doesn't remain
underutilized, as it can collaborate with other devices in their tasks or perform common functions not
directly related. Furthermore, the Edge Tier plays a crucial role in executing critical workloads,
emphasizing the adaptability of Kubernetes cluster architecture to dynamically scale with low latency.
In this context, the ROS Framework addresses the hardware interoperability challenge, ensuring that
the Kubernetes infrastructure is compatible with various types of robots and edge devices used in
HRC (Human-Robot Collaboration).</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Ambient Network Tier</title>
        <p>The Ambient Network encloses all the infrastructure that conforms the real-time communication
network between the different Edge Tier devices ensuring that their time sensitive needs are met, as
well as the tools to monitor and control the traffic inside said network. The Ambient Tier relies on a
SDN (Software-Defined Networking) controller which allows configuring the low-level behavior of
each device therefore allowing us to disregard the low-level functionalities during the development
of new applications. This tier also connects Edge devices with those modules executed in the Fog Tier.</p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. Fog Tier</title>
        <p>The Fog Tier groups those AI-PRISM modules that are deployed between the Edge Tier and the Cloud
Tier. Some modules, traditionally, with real-time constraints or with minimal computational
requirements will be running on a controller on the same workspace, while other modules with no
real-time constraints as well as data storage services will be running on a cloud environment.
Therefore, two kinds of communication platforms can be found in the Fog cluster: the ROS DDS
communication, which connects the devices with real-time requirements; and the IIoT Platform,
which is used to share data between these resource expensive modules. In the same way as in the
Device Tier, the deployment and management of modules into clusters is carried out using Rancher
considering that this Fog Cluster, as stated before, will be running these two clearly differentiated
kinds of modules.</p>
        <p>This tier encompasses various modules to form a cohesive system that enhances the capabilities
of the Tier:
(i) Data Platform Service, a fundamental component, plays a crucial role in efficiently managing
the data collected from the edge through the IIoT Platform. Its primary functions include
storing and making this data easily accessible to other modules, ensuring a flow of
information within the system, as well as controlling the quality of service of
communications through the SDN network APIs.
(ii) Simulation Modules, providing users with tools to simulate scenarios, facilitating tests of the
developed components. This feature empowers users to optimize solutions by subjecting
them to different test scenarios, improving their adaptability and performance in
realworld applications.
(iii) Perception Modules, another integral part of this tier, leverage data acquired through the
sensing infrastructure of the Device Tier. These modules are responsible for creating a
digital reconstruction of the working environment, providing a representation of the
actors. Additionally, Perception Modules excel in describing actors within the
environment, identifying objects from CAD models, and using neural networks for
specialized tasks, showcasing the advanced cognitive capabilities of the system.
(iv) Reasoning Modules contribute to the dynamism of the collaborative environment by
coordinating available agents. These modules command actions based on ongoing tasks
and awareness derived from the environment, ensuring synchronized system operation.
(v) Collaboration Modules refers to the modules that while ensuring safe interactions between
human and robot agents in the ambient, provide interfaces between the human workers
and the robotic agents allowing the human to teach the system a task that is desired to be
executed by the robot through demonstration. This teaching can be done by observing the
human user or by graving the robotic arm and guiding it through the process while we
track the motion. Then the robot executes said action, which could be collaborative in such
a way that the human could instruct the robot by using commands, which could include
any kind of human-robot interaction, like shouting a verbal directive or physically
interrupting the robot motion. And, in the same manner, the robot can provide information
about its current state to the user using acoustic or visual indicators.</p>
        <p>In the same way that there is a centralized management of the deployed modules in the Device
Tier, the fog cluster or clusters are also managed through Rancher, keeping a centralized control of
the whole distributed architecture.</p>
      </sec>
      <sec id="sec-2-4">
        <title>2.4. Enterprise Tier</title>
        <p>The Enterprise Tier groups the components that enable CI/CD (Continuous Integration and
Continuous Deployment) of solutions, and the components that enable open access of the AI PRISM
solutions to external collaborators. These components can be found in the cloud cluster where the
AI-PRISM partners, who are connected to said cluster, will have access to the AI-PRISM tools allowing
them to deploy the desired components to their working environment, and they will also be
contributing to the aforementioned solutions if any relevant module or piece of data can be used to
improve the AI-PRISM capabilities. The Open Access Platform services provide a layer of
hyperconnectivity enabling virtual access to remote resources and are described in detail in the next section.</p>
      </sec>
      <sec id="sec-2-5">
        <title>2.4.1. AI-PRISM Open-Access Platform</title>
        <p>The AI-PRISM Open-Access Platform (also known as the Network suite) is a web-based platform
through which AI-PRISM technologies, modules, components, and infrastructure can be accessed.
The platform acts as the gateway for the AI-PRISM stakeholders (industry experts, researchers,
developers, manufacturers etc.) to access AI-PRISM tools and utilize the available resources. Through
the platform services, end-users can gain remote access to various AI-PRISM offerings (software,
algorithms, and datasets), industrial infrastructure (industrial facilities and testing sites) and resources
such as robotic systems and industrial equipment. The platform consists of a set of components that
aid the orchestration and management of access to AI-PRISM offerings to interested parties and
stakeholders. These components, also called “engines” includes user interface (UI) engine (for
accessing the platform), user access control engine (for managing the users’ rights and access),
training and certification engine (for teaching and education), planning and scheduling engine (for
handling user visits to testing sites and matching users to resources), contracts and finance engine
(for managing financial agreement between stakeholders) and virtual pilot engine. The services
provided by the platform through the different engines enhances the visibility of the available
AIPRISM technologies and resources.</p>
        <p>The Open-Access Platform ensures access and facilitates the findability of tools and resources
needed by the AI-PRISM stakeholders. For instance, System Admins can utilize the platform to
discover a series of AI tools, ascertain and deploy modules compatible with their local infrastructure.
Also, shopfloor operators working with collaborative robots can utilize the platform to access the
AIPRISM simulation environment to model the human-robot work layout as a means of assessing the
collaborative interactions and monitoring the efficiency of the workflows. With this, the open-access
platform facilitates the collaboration between infrastructure providers and the end-users, who utilize
the available infrastructure and resources to test and validate the different AI-PRISM technologies to
assess their performance and functionality. In addition, the end-users can leverage the available
resources to develop new AI based collaborative robotics and human-centered solutions that can
enhance their business operations. This collaboration increases the exploitation potential of the newly
developed solution and brings added value such early experimentation, possibility to test the solutions
before investing money as well as certification and training. The collaboration also ensures that the
infrastructure providers can benefit through equipment utilization, capitalization of unused resources
and acceleration of upskilling for their workforce. In general, the AI-PRISM Open Access Platform
encourages the development of new AI-based collaborative robotics solutions, facilitates knowledge
sharing and transfer, enhances upskilling of workforce regarding the application of AI in
manufacturing, and promotes the ethical use of AI.</p>
      </sec>
      <sec id="sec-2-6">
        <title>2.5. Edge Tier</title>
        <p>In conclusion, the AI-PRISM reference architecture presents a seamless solution to the challenges of
deploying AI-driven human-robot collaboration (HRC) systems in industrial environments. By
leveraging a distributed cluster architecture and adopting standardized frameworks such as
Kubernetes, ROS, and PLC, AI-PRISM ensures efficient management of hardware components,
communication networks, and software modules. AI-PRISM provides a structured approach to
deploying and managing HRC applications, addressing latency, reliability, and scalability issues
case-by-case through its Edge, Ambient Network, Fog, and Enterprise tiers. In addition, the AI
PRISM open-access platform facilitates collaboration and knowledge sharing among stakeholders,
enhancing the development and adoption of AI-based solutions while ensuring ethical practices and
regulatory compliance. The AI-PRISM reference architecture offers a promising path towards a more
adaptable, efficient, and scalable robotic system in industrial environments, stepping into the era of</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>Acknowledgements</title>
      <p>AI-PRISM has received funding from the European Union’s Horizon Europe research and innovation
programme under grant agreement No 101058589.</p>
    </sec>
    <sec id="sec-4">
      <title>Declaration on Generative AI</title>
      <p>The author(s) have not employed any Generative AI tools.</p>
    </sec>
  </body>
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