Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Time-Sensitive Networking over Metropolitan Area Networks for Remote Industrial Control
    ( 2021)
    Tschöke, Simon
    ;
    Lynker, Frederic
    ;
    Buhr, Hauke
    ;
    Schreiner, Florian
    ;
    Willner, Alexander
    ;
    Vick, Axel
    ;
    Chemnitz, Moritz
    The benefits of the currently evolving IEEE Time-Sensitive Networking (TSN) standard have already been globally recognized. Whereas the application of TSN in a LAN is currently widely and globally tested, TSN in a Metropolitan Area Network (MAN) has not been a major focus until now. The possible benefits of utilizing co-located Edge Clouds in order to support multiple urban production sites with industrial realtime applications open a wide range of new business models. Therefore, we have analyzed the feasibility of transparently using PROFINET over TSN via a Dense Wavelength Division Multiplex (DWDM) link, where a machine park is controlled remotely by an Edge-based virtual Programmable Logic Controller (vPLC). As a result, we are able to setup a TSN connection over a MAN with a one-way delay of about 156.5 J.ms and a jitter of about 12 ns. This work can be extended to allow for dynamically provisioned TSN flows and multi-path Frame Replication and Elimination (FRER) for distributed hard real-time machine control and adoption to Ultra-Reliable Low-Latency Communication (URLLC) 5G campus networks.
  • Publication
    Networked Visual Servoing as Use-Case for Cloud-based Industrial Robot Control
    ( 2020)
    Vick, Axel
    ;
    Krause, Christian
    ;
    Krüger, Jörg
    Nowadays production industry and smart factory is dealing with methods of optimal resource load balancing and new types of flexible service-oriented strategies. It is seen crucial to adapt quickly to changes in manufacturing processes and new products or even integrate new hardware faster than the competition. Flexibility and Scalability can be improved by exchanging only a certain part of hardware and software without the need of touching all the other components. In this paper we present a methodical approach towards a typical use case in modern industrial robotic systems. The system consists of hardware components from different manufacturers which can be controlled and monitored separately by remote services. Those services can be combined to complex applications and integrate value added services. We show the independence and capability of exchangeable added value services running either centralized, decentralized, locally or remote. The experiments demonstrate how a process is improve by simply adding another service according to the Plug-and-Play paradigm. The service ensures the conditions of a computer vision system component to keep the reliability of the overall system workflow. In addition it will be demonstrated how system components could be virtualized in container-based cloud environments to save required on-board resources of the robotic system while keeping the whole system communication secure. Finally, results will be presented for different intercommunication scenarios.
  • Publication
    Variable-Latency Networked P-PI and MPC Controller Performance for Industrial Robots
    ( 2019)
    Vick, Axel
    ;
    Kilinc, Ali
    ;
    Guhl, Jan
    The controller design for industrial robot joint positioning is based on fixed cycle times and accurate modeling. Applying closed loop systems to decentralized control networks with variable connection properties would lead to unacceptable performance drops of the controlled mechanism. On the other hand service-oriented and networked control modules are providing full flexibility of location independent execution. But using wide-area connection like internet or wireless networks is yielding unpredictable latency and jitter conditions. That is not well handled by standard feedback controllers like PID or P-PI cascades. This paper presents the comparison of a modified MPC to a standard P-PI controller. That comparison reveals the strengths and weaknesses of each approach regarding controller performance under different communication conditions. Reusing the MPC control trajectory allows the robot to follow a small open-loop trajectory during latency deviation. That improves the performance criteria like overshoot and damping significantly. The overall robustness of the modified MPC is demonstrated empirically by extensive experiments with an laboratory industrial robot.
  • Publication
    Cognitive Edge for Factory
    ( 2019)
    Lambrecht, Jens
    ;
    Steffens, Ernst Joachim
    ;
    Geitz, Marc
    ;
    Vick, Axel
    ;
    Funk, Eugen
    ;
    Steigerwald, Wolfgang
    Mobile autonomous transport systems are a crucial part of flexible factory logistics enabling an adaptable industrial production. Whereas connectivity of these mobile robots is still mostly covered through Wifi, applicators suffer from interferences and unreliableness due to the harsh environmental conditions. We present a case study using 4G campus networks applying network slicing technology and edge computing in order to realize a distributed control scenario. Control algorithms are offloaded to the edge following a navigation as a service approach. Basic safety functions remain onboard while self-localization and mapping as well as motion planning run on either a factory edge, a nearby edge or on a public cloud. We present an evaluation of the overall architecture and focus on effects of offloading control functions towards the edge. Finally, we provide an outlook towards the usage of 5G.
  • Publication
    Visualizing trajectories for industrial robots from sampling-based path planning on mobile devices
    ( 2018)
    Guhl, Jan
    ;
    Vick, Axel
    ;
    Vonasek, Vojtech
    ;
    Krüger, Jörg
    Production lines are nowadays transforming into flexible modular and interconnected cells to react to rapidly changing product demands. The arrangement of the workspace inside the modular cells will vary according to the actual product being developed. Tasks like motion planning will not be possible to precompute. Instead, it has to be solved on demand. Planning the trajectories for the industrial robots with respect to changing obstacles and other varying environment parameters is hard to solve with classical path planning approaches. A possible solution is to employ sampling-based planning techniques. In this paper we present a distributed sampling-based path planner and an augmented reality visualization approach for verification of trajectories. Combining the technologies ensures a confirmed continuation of the production process under new conditions. Using parallel and distributed path planning speeds up the planning phase significantly and comparing different mobile devices for augmented reality representation of planned trajectories reveals a clear advantage for hands-free HoloLens. The results are demonstrated in several experiments in laboratory scale.
  • Publication
    Cloud-based active disturbance rejection control for industrial robots
    ( 2018)
    Briese, Clemens
    ;
    Vick, Axel
    ;
    Krüger, Jörg
    The classical design of industrial robot controllers relies strongly on constant and stable cycle times for any closed loop operation. Meanwhile, decentralizing robot control into independent services and rolling them out to virtual machines and cloud instances is an upcoming trend. The advantage of the distributed robot control lies in achieving full flexibility of location independent service execution. In contrast, the internet connectivity leads to unknown latency conditions and resulting unpredictable cycle times. That is not well handled by standard feedback controllers like PID or P-PI cascades. In addition to the time-critical aspect, the performance of a closed-loop control relies on the accuracy of the underlying model. Modeling is often labor-intensive and time-consuming. This paper presents four different implementations of a non-model based modified Switching Active Disturbance Rejection Control (ADRC) in a robotic use case. The comparison of these four concepts reveals the strengths and weaknesses of the ADRC approach regarding controller performance under the assumption of full dynamics compensation with tough communication conditions. By extending the Switching-ADRC approach by a gain-scheduler to smooth the switching between the linear and non-linear ADRC description and a static adjustment of control-parameters related to the measured round-trip time, the presented control-concept is able to stabilize the high-dynamic, partly unstable robot-system without model-information. The stability of the modified Switching-ADRC is demonstrated empirically by extensive experiments with a distributed industrial robot joint position control.
  • Publication
    Distributed Industrial Robot Control using Environment Perception and Parallel Path Planning Cloud Services
    ( 2018)
    Wassermann, Jonas
    ;
    Vonasek, Vojtech
    ;
    Vick, Axel
    Recent developments in connected industries and internet of things identified demands for flexible reconfiguration and reprogramming of robots and machine tools. The demand for reconfiguration comes from changes in production process ordering or individual products; the demand for reprogramming comes from changing workplace organization and material flow. Yet these reconfiguration and reprogramming is often characterized by constants for a specific use-case in terms of precomputed trajectories. In this paper, we present an approach of monitoring the robot's workspace and using an online replanning of motion. We present a toolchain that is available and ready to use for a big class of industrial robots that have a position setpoint control interface. The feasibility is demonstrated in small laboratory experiments with a modular industrial robot in a common human-robot interface scenario.
  • Publication
    Using OPC UA for Distributed Industrial Robot Control
    ( 2018)
    Vick, Axel
    ;
    Krüger, Jörg
    The production industry is confronted with a big change from classical factory planning to digitized and networked structures. The line-based or batch mass production of one and the same product over tens of years is developing to an end-user driven individualization with production cycles of less than one year. To react to the fast changing requirements on products and production infrastructure, machine tools and industrial robots as well as the complete intra-factory logistics, have to evolve to universal production tools with high connectivity, the cyber-physical production systems (CPPS). Current monolithic robot control architectures lack flexibility and scalability to support that short production cycles. This paper presents a distributed control architecture that is capable of reorganizing the production process on the fly. The control system uses OPC UA as communication layer and is capable of combining hardware control services together with high level control services and build individual software systems for each automation task. The system is highly scalable in terms of additional components, improved algorithms or location change. Experiments are implemented with an industrial robot with cameras and gripper in a human-robot collaborative pick and place use case.