Energy conservation is crucial in wireless ad hoc sensor network design to increase network lifetime. Since communication consumes a major part of the energy used by a sensor node, efficient communication is important. Topology control aims at achieving more efficient communication by dropping links and reducing interference among simultaneous transmissions by adjusting the nodes’ transmission power. Since dropping links make a network more susceptible to node failure, a fundamental problem in wireless sensor networks is to find a communication graph with minimum interference and minimum power assignment aiming at an induced topology that can satisfy fault-tolerant properties. In this paper, we examine and propose linear integer programming formulations and a hybrid meta-heuristic GRASP/VNS (Greedy Randomized Adaptive Search Procedure/Variable Neighborhood Search) to determine the transmission power of each node while maintaining a fault-tolerant network and simultaneously minimize the interference and the total power consumption. Optimal biconnected topologies for moderately sized networks with minimum interference and minimum power are obtained using a commercial solver. We report computational simulations comparing the integer programming formulations and the GRASP/VNS, and evaluate the effectiveness of three meta-heuristics in terms of the tradeoffs between computation time and solution quality. We show that the proposed meta-heuristics are able to find good solutions for sensor networks with up to 400 nodes and that the GRASP/VNS was able to systematically find the best lower bounds and optimal solutions.
Communication problems are acknowledged as hazardous eventualities affecting operations negatively. However, a few systematic attempts have been made to understand the pattern of communication issues and their contribution to safety events. In this paper, we present the AVAC-COM communication model and taxonomy based on the cybernetics approach and a literature review. The model elements and taxonomy variables regard the actors, signals, coders, interference, direction and timing, predictability, decoders, and channels. To test the applicability and potential value of the AVAC-COM framework, we analysed 103 safety investigation reports from aviation published between 1997 and 2016 by the respective authorities of Canada, the United States, Australia, the United Kingdom and the Netherlands. The overall results of the 256 cases of communication flaws detected in the reports suggested that these regarded more frequently Human-Media and Human-Human interactions, verbal and local communications as well as unfamiliarity of the receivers with the messages transmitted. Further statistical tests revealed associations of the region, time period, event severity and operations type with various variables of the AVAC-COM taxonomy. Although the findings are only indicative, they showed the potential of the AVAC-COM model and taxonomy to be used to identify strong and weak communication elements and relationships in documented data such as investigation and hazard reports.
In the aviation sector, communication problems have contributed into 70% to 80% of safety occurrences. However, to date we haven’t depicted which communication aspects have affected aviation safety most frequently.Based on literature, we developed a tool which includes communication characteristics related to actors, signal, coder, channel, decoder, direction, timing, distance, predictability and interference. After achieving inter-rater reliability, the tool was used to analyse 103 safety investigation reports that correspond to events occurred in various regions and which included in total 256 communication problems. The results suggest that communication between humans and representation media, visual and audio signalling and decoding, air-transmitted messages, and verbal, unidirectional, local and synchronous communication contributed most frequently into safety events. Statistical tests showed that the frequencies of most of those characteristics were significantly different across regions, time periods, types of operations and event severity.The tool developed can be used by different organizations and industry sectors to distil and analyse data from mandatory and voluntary reports and identify weak communication areas. Depending on the findings, analysts might need to alert designers of technical systems, inform management of organizations, warn end-users about most frequent pitfalls, modify/enrich communication training and steer research efforts.
Brandweermensen lopen het meeste gevaar als ze onder tijdsdruk een gebouw moeten verkennen, of een brand moeten blussen terwijl de situatie nog niet goed kan worden overzien. Omvallende muren, instortende plafonds of gewoon gestruikeld over door de rook onzichtbare brokstukken leiden tot vermijdbare letsels of zelfs slachtoffers. Met name de inzet bij branden in stedelijke parkeergarages onder woontorens vormen een enorm risico. Het inzetten van onbemande, op afstand bestuurbare voertuigen voor verkenning en bluswerk is een oplossing die binnen de brandweer breed wordt gedragen. De brandweer moet deze innovatieve technologie echter zien te omarmen. Zij werken nu vanuit hun intuïtie en weten direct hoe te acteren op basis van wat zij waarnemen. Praktijkgericht onderzoek heeft echter uitgewezen dat scepsis over de inzet van blusplatforms bij incidenten plaats heeft gemaakt voor zeker vertrouwen. Een blusplatform, voorzien van juiste sensoren kan de Officier van Dienst (OVD) ondersteunen bij het nemen van een beslissing om al dan niet tot een ‘aanval’ over te gaan. Praktijktesten hebben echter laten zien dat de huidige blusplatforms nog niet optimaal functioneren om als volwaardig ‘teamlid’ te kunnen worden ingezet. Dit heeft enerzijds met technologische ontwikkelingen (sensoren en communicatieverbindingen) te maken, maar anderzijds moet de informatievoorziening (human-machine interfacing) naar de brandweer beter worden afgestemd. In dit project gaan Saxion, het instituut fysieke veiligheid, de universiteit Twente, het bedrijfsleven en vijf veiligheidsregio’s onderzoeken hoe en wanneer innovatieve blusplatforms op een intuïtieve manier kunnen worden ingezet door training én (kleine) productaanpassing zodat deze een volwaardig onderdeel kunnen zijn van het brandweerkorps. Een blusplatform kan letselschade en slachtoffers voorkomen, mits goed ingezet en vertrouwd door de mensen die daarvan afhankelijk zijn. Het vak van brandweer, als beroeps of vrijwilliger, is een van de gevaarlijkste die er is. Laten we er samen voor zorgen dat het iets veiliger kan worden.
The demand for mobile agents in industrial environments to perform various tasks is growing tremendously in recent years. However, changing environments, security considerations and robustness against failure are major persistent challenges autonomous agents have to face when operating alongside other mobile agents. Currently, such problems remain largely unsolved. Collaborative multi-platform Cyber- Physical-Systems (CPSs) in which different agents flexibly contribute with their relative equipment and capabilities forming a symbiotic network solving multiple objectives simultaneously are highly desirable. Our proposed SMART-AGENTS platform will enable flexibility and modularity providing multi-objective solutions, demonstrated in two industrial domains: logistics (cycle-counting in warehouses) and agriculture (pest and disease identification in greenhouses). Aerial vehicles are limited in their computational power due to weight limitations but offer large mobility to provide access to otherwise unreachable places and an “eagle eye” to inform about terrain, obstacles by taking pictures and videos. Specialized autonomous agents carrying optical sensors will enable disease classification and product recognition improving green- and warehouse productivity. Newly developed micro-electromechanical systems (MEMS) sensor arrays will create 3D flow-based images of surroundings even in dark and hazy conditions contributing to the multi-sensor system, including cameras, wireless signatures and magnetic field information shared among the symbiotic fleet. Integration of mobile systems, such as smart phones, which are not explicitly controlled, will provide valuable information about human as well as equipment movement in the environment by generating data from relative positioning sensors, such as wireless and magnetic signatures. Newly developed algorithms will enable robust autonomous navigation and control of the fleet in dynamic environments incorporating the multi-sensor data generated by the variety of mobile actors. The proposed SMART-AGENTS platform will use real-time 5G communication and edge computing providing new organizational structures to cope with scalability and integration of multiple devices/agents. It will enable a symbiosis of the complementary CPSs using a combination of equipment yielding efficiency and versatility of operation.
