Multi-Agent Systems

This Special Issue ""Multi-Agent Systems"" gathers original research articles reporting results on the steadily growing area of agent-oriented computing and multi-agent systems technologies. After more than 20 years of academic research on multi-agent systems (MASs), in fact, agent-oriented models and technologies have been promoted as the most suitable candidates for the design and development of distributed and intelligent applications in complex and dynamic environments. With respect to both their quality and range, the papers in this Special Issue already represent a meaningful sample of the most recent advancements in the field of agent-oriented models and technologies. In particular, the 17 contributions cover agent-based modeling and simulation, situated multi-agent systems, socio-technical multi-agent systems, and semantic technologies applied to multi-agent systems. In fact, it is surprising to witness how such a limited portion of MAS research already highlights the most relevant usage of agent-based models and technologies, as well as their most appreciated characteristics. We are thus confident that the readers of Applied Sciences will be able to appreciate the growing role that MASs will play in the design and development of the next generation of complex intelligent systems. This Special Issue has been converted into a yearly series, for which a new call for papers is already available at the Applied Sciences journal’s website: https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems_2019

Optimization-based coordination strategies for connected and autonomous vehicles

Automated vehicles (AV) are expected to reach the consumer market within the next decade.Once AVs become ubiquitous, they could resolve difficult traffic situations through communication-based cooperation.Intersections are of particular interest in this context, as they form bottlenecks in the traffic system and are responsible for a large share of all accidents.Rather than relying on traffic lights, road signs and rules, AVs could employ cooperative strategies to decide how an intersection should be crossed safely and efficiently.However, designing efficient coordination strategies for AVs at intersections is challenging, as computationally hard problems are involved, with a safety-critical dependence on both wireless communication and imprecise sensing.This thesis treats control algorithms for cooperative coordination of CAVs at intersections.The proposed algorithms are based on Optimal Control (OC) formulations of the coordination problem and aim at finding the optimal control commands for each vehicle through a two-stage approximation procedure.In the first stage, the order in which the vehicles cross the intersection is determined using a heuristic based on Mixed-Integer Quadratic Programming (MIQP).In the second stage, the optimal control commands for each vehicle are found under a fixed crossing order.Two algorithms are presented that solves the problem of the second stage in a communication efficient, distributed fashion.In the first algorithm, the problem is decomposed into one master-problem and one sub-problem for each vehicle.The master-problem is solved using a Sequential Quadratic Programming (SQP) algorithm, where most computations are performed in parallel on-board the vehicles. In the second algorithm, the problem is solved using a Primal-Dual Interior Point (PDIP) method. The computations involved are separable so that the largest part can be performed in parallel on-board the vehicles, a lesser part in parallel on lead-vehicles for each lane, and a small part at a central network node. The two-stage approximation procedure is used in a Model Predictive Controller (MPC), and conditions for persistent feasibility and stability are derived.Performance of the MPC-based closed-loop controller is assessed in simulation, and compared to traffic-lights and alternative coordination algorithms.The results demonstrate that the two-stage approach outperforms existing alternatives, with almost zero average travel-time delay and a marginal increase in energy consumption compared to cruising at constant speed.An MPC controller based on the SQP algorithm is verified experimentally at a test-track with three real vehicles.The results demonstrate that efficient coordination is practically realizable through communication-based optimization and MPC.In particular, the experiments show that the MPC algorithm performs well under adverse conditions with significant sensor noise, communication impairments and external perturbations

Certification Considerations for Adaptive Systems

Advanced capabilities planned for the next generation of aircraft, including those that will operate within the Next Generation Air Transportation System (NextGen), will necessarily include complex new algorithms and non-traditional software elements. These aircraft will likely incorporate adaptive control algorithms that will provide enhanced safety, autonomy, and robustness during adverse conditions. Unmanned aircraft will operate alongside manned aircraft in the National Airspace (NAS), with intelligent software performing the high-level decision-making functions normally performed by human pilots. Even human-piloted aircraft will necessarily include more autonomy. However, there are serious barriers to the deployment of new capabilities, especially for those based upon software including adaptive control (AC) and artificial intelligence (AI) algorithms. Current civil aviation certification processes are based on the idea that the correct behavior of a system must be completely specified and verified prior to operation. This report by Rockwell Collins and SIFT documents our comprehensive study of the state of the art in intelligent and adaptive algorithms for the civil aviation domain, categorizing the approaches used and identifying gaps and challenges associated with certification of each approach

An agile and adaptive holonic architecture for manufacturing control

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. 2004. Faculdade de Engenharia. Universidade do Port

Supply Chain

Traditionally supply chain management has meant factories, assembly lines, warehouses, transportation vehicles, and time sheets. Modern supply chain management is a highly complex, multidimensional problem set with virtually endless number of variables for optimization. An Internet enabled supply chain may have just-in-time delivery, precise inventory visibility, and up-to-the-minute distribution-tracking capabilities. Technology advances have enabled supply chains to become strategic weapons that can help avoid disasters, lower costs, and make money. From internal enterprise processes to external business transactions with suppliers, transporters, channels and end-users marks the wide range of challenges researchers have to handle. The aim of this book is at revealing and illustrating this diversity in terms of scientific and theoretical fundamentals, prevailing concepts as well as current practical applications

Design and evaluation of safety-critical applications based on inter-vehicle communication

Inter-vehicle communication has a potential to improve road traffic safety and efficiency. Technical feasibility of communication between vehicles has been extensively studied, but due to the scarcity of application-level research, communication\u27s impact on the road traffic is still unclear. This thesis addresses this uncertainty by designing and evaluating two fail-safe applications, namely, Rear-End Collision Avoidance and Virtual Traffic Lights

Distributed dispatchers for partially clairvoyant schedulers

This work focuses on the empirical evaluation of distributed dispatching strategies on shared and distributed memory architectures for hard real-time systems. The dispatching model accommodates process parameter variability and analyzes the effect of variable execution times.;Hard real-time systems are modeled in the E-T-C scheduling framework and dispatched if a valid schedule exists. We examine the dispatchability of Partially Clairvoyant schedules of different sizes and varying deadlines under reasonable assumptions. The effect of scaling up the number of processors used by the dispatcher is also studied. The results validate the superiority of the distributed strategies over sequential dispatching and scalability of the distributed strategies. Certain system limitations which lead to Loss of Dispatchability in the experiments were pointed out.;The model finds applications in diverse areas like safety critical systems, robotics and machine control, real-time data management, and this approach is targeted at powering up the controllers