Real-time performance analysis of a QoS based industrial embedded network

AFDX serves as a backbone network for transmission of critical avionic flows. This network is certified thanks to the WCTT analysis using Network Calculus (NC) approach. However, the pessimism introduced by NC approach often leads to an over-sized and eventually an underutilized network. The manufacturers envision to better use the available network resources by increasing occupancy rate of the AFDX network by allowing additional traffic from other critical and non-critical functions. Such harmonization of AFDX network with mixed criticality flows necessitates the use of QoS mechanism to satisfy the delay constraints in different classes of flow. In this thesis we study such QoS-aware network, in particular, based on DRR and WRR scheduling. We propose an optimal bandwidth distribution method that ensures the service required by critical flows while providing maximum service to other non-critical flows. We also propose an optimized NC approach to compute tight delay bounds. Our approach has led to computation of up to 40% tighter bounds, in an industrial AFDX configuration, as compared to the classical approach

Vers la convergence de réseaux dans l'avionique

AFDX est le standard Ethernet commuté utilisé pour la transmission des flux avioniques. Pour des raisons de certification, le réseau AFDX déployé à présent dans les avions civils est très peu chargé. Cette thèse vise à étudier la possibilité envisagée par les avionneurs d’utiliser la bande passante AFDX restante pour transporter des flux non-avioniques additionnels (vidéo, audio, service). Ces flux ne doivent pas affecter les délais de transmission des flux avioniques. Pour multiplexer des flux avioniques et non-avioniques des politiques d’ordonnancement sont nécessaires au niveau des systèmes d’extrémité (end systems) et des commutateurs. Dans cette thèse, nous considérons l’exemple de la transmission sur AFDX de flux vidéo provenant des caméras de surveillance de l’avion. Le multiplexage des flux avioniques et vidéo est réalisé par l’introduction d’une table d’ordonnancement au niveau des end systems émetteurs et d’une politique de type SPQ dans les ports de sortie du commutateur. Cette solution préserve les contraintes temps-réel des flux avioniques, mais peut introduire des variations sur les délais de bout-en-bout des flux vidéo. Une allocation appropriée des flux avioniques dans la table d’ordonnancement peut réduire le retard d’émission des flux vidéo et ainsi, limiter les variations de délai. Nous proposons deux stratégies d’allocation des flux avioniques dans la table d’ordonnancement : une heuristique simple et une allocation optimale. L’allocation optimale est dérivée en résolvant un problème d’optimisation par contraintes qui minimise le retard d’émission des flux vidéo. Dans le cas des end systems moins chargés, l’allocation par heuristique est proche de l’optimale

Integrating Offset in Worst Case Delay Analysis of Switched Ethernet Network With Deficit Round Robbin

International audienceIn order to handle mixed criticality flows in a realtime embedded network, switched Ethernet with Quality of Service (QoS) facilities has become a popular solution. Deficit Round Robin (DRR) is such a QoS facility. Worst-Case Traversal Time (WCTT) analysis is mandatory for such systems, in order to ensure that end-to-end delay constraints are met. Network Calculus is a classical approach to achieve this WCTT analysis. A solution has been proposed for switched Ethernet with DRR. It computes pessimistic upper bounds on end-to-end latencies. This pessimism is partly due to the fact that the scheduling of flows by end systems is not considered in the analysis. This scheduling can be modeled by offsets between flows. This modeling has been integrated in WCTT analysis of switched Ethernet with First In First Out (FIFO) scheduling. It leads to a significant reduction of delay upper bounds. The contribution of this paper is to integrate the offsets in the WCTT analysis for switched Ethernet with DRR and to evaluate the reduction on delay upper bounds, considering a realistic case study

Challenges for engineering students working with authentic complex problems

Engineers are important participants in solving societal, environmental and technical problems. However, due to an increasing complexity in relation to these problems new interdisciplinary competences are needed in engineering. Instead of students working with monodisciplinary problems, a situation where students work with authentic complex problems in interdisciplinary teams together with a company may scaffold development of new competences. The question is: What are the challenges for students structuring the work on authentic interdisciplinary problems? This study explores a three-day event where 7 students from Aalborg University (AAU) from four different faculties and one student from University College North Denmark (UCN), (6th-10th semester), worked in two groups at a large Danish company, solving authentic complex problems. The event was structured as a Hackathon where the students for three days worked with problem identification, problem analysis and finalizing with a pitch competition presenting their findings. During the event the students had workshops to support the work and they had the opportunity to use employees from the company as facilitators. It was an extracurricular activity during the summer holiday season. The methodology used for data collection was qualitative both in terms of observations and participants’ reflection reports. The students were observed during the whole event. Findings from this part of a larger study indicated, that students experience inability to transfer and transform project competences from their previous disciplinary experiences to an interdisciplinary setting

Exploring the practical use of a collaborative robot for academic purposes

This article presents a set of experiences related to the setup and exploration of potential educational uses of a collaborative robot (cobot). The basic principles that have guided the work carried out have been three. First and foremost, study of all the functionalities offered by the robot and exploration of its potential academic uses both in subjects focused on industrial robotics and in subjects of related disciplines (automation, communications, computer vision). Second, achieve the total integration of the cobot at the laboratory, seeking not only independent uses of it but also seeking for applications (laboratory practices) in which the cobot interacts with some of the other devices already existing at the laboratory (other industrial robots and a flexible manufacturing system). Third, reuse of some available components and minimization of the number and associated cost of required new components. The experiences, carried out following a project-based learning methodology under the framework of bachelor and master subjects and thesis, have focused on the integration of mechanical, electronic and programming aspects in new design solutions (end effector, cooperative workspace, artificial vision system integration) and case studies (advanced task programming, cybersecure communication, remote access). These experiences have consolidated the students' acquisition of skills in the transition to professional life by having the close collaboration of the university faculty with the experts of the robotics company.Postprint (published version