Tullio Facchinetti

Real-Time Modeling for Direct Load Control in Cyber-Physical Power Systems

This paper presents an innovative approach to use real-time scheduling techniques for the automation of electric loads in Cyber-Physical Power Systems. The goal is to balance the electric power usage to achieve an optimized upper bound on the power peak load, while guaranteeing specific constraints on the physical process controlled by the electric loads. Timing parameters derived from the scheduling discipline of real-time computing systems are used to model electric devices. Real-time scheduling algorithms can be exploited to achieve the upper bound by predictably and timely switching on/off the devices composing the electrical system. The paper shows the relevance of electric load balancing in power systems to motivate the use of real-time techniques to achieve predictability of electric loads scheduling. Real-Time Physical Systems (RTPS) are introduced as a novel modeling methodology of a physical system based on real-time parameters. They enable the use of traditional real-time system models and scheduling algorithms, with adequate adaptations, to manage loads activation/deactivation. The model of the physical process considered in this work is characterized by uncertainties that are compensated by a suitable feedback control policy, based on the dynamic adaptation of real-time parameter values. A number of relevant relationships between real-time and physical parameters are derived.

Real-time resource reservation protocol for wireless mobile ad hoc networks

Wireless communication technology is spreading quickly in almost all the information technology areas as a consequence of a gradual enhancement in quality and security of the communication, together with a decrease in the related costs. This facilitates the development of relatively low-cost teams of autonomous (robotic) mobile units that cooperate to achieve a common goal. Providing real-time communication among the team units is highly desirable for guaranteeing a predictable behavior while operating autonomously in unstructured environments. This paper proposes a MAC protocol for wireless communication that supports dynamic resource reservation for small teams of cooperative robots. The protocol uses a slotted time-triggered medium access transmission control that is collision-free, even in the presence of hidden nodes. The transmissions are scheduled according to the earliest deadline first scheduling policy. An adequate admission control guarantees the timing constraints of the team communication requirements, including when new nodes dynamically join or leave the team. The paper describes the protocol focusing on the consensus procedure that supports coherent changes in the global system. Finally, a set of simulation results are shown that illustrate the effectiveness of the proposed protocol.

Coordinating distributed autonomous agents with a real-time database: the CAMBADA project

Interest on using mobile autonomous agents has been growing, recently, due to their capacity to cooperate for diverse purposes, from rescue to demining and security. However, such cooperation requires the exchange of state data that is time sensitive and thus, applications should be aware of data temporal coherency. In this paper we describe the architecture of the agents that constitute the CAMBADA (Cooperative Autonomous Mobile roBots with Advanced Distributed Architecture) robotic soccer team developed at the University of Aveiro, Portugal. This architecture is built around a real-time database that is partially replicated in all team members and contains both local and remote state variables. The temporal coherency of the data is enforced by an adequate management system that refreshes each database item transparently at a rate specified by the application. The application software accesses the state variables of all agents with local operations, only, delivering both value and temporal coherency.

Non-preemptive interrupt scheduling for safe reuse of legacy drivers in real-time systems

Low-level support of peripheral devices is one of the most demanding activities in a real-time operating system. In fact, the rapid development of new interface boards causes a tremendous effort at the operating system level for writing and testing low-level drivers for supporting the new hardware. The possibility of reusing legacy drivers in real-time systems would offer the great advantage of keeping the rate of changes with a small programming effort. Since typical legacy drivers are written to execute in a non-preemptive fashion, a suitable operating system mechanism is needed to protect real-time application tasks from unpredictable bursty interrupt requests. In this paper, we present a novel approach suitable for scheduling interrupt service routines. Main features of the method include: high priority of the handler, non preemptive execution, bandwidth reservation for the application tasks, and independence of the interrupt service policy from the scheduling policy adopted for the application tasks.

Dynamic resource reservation and connectivity tracking to support real-time communication among mobile units

Wireless communication technology is spreading quickly in almost all the information technology areas as a consequence of a gradual enhancement in quality and security of the communication, together with a decrease in the related costs. This facilitates the development of relatively low-cost teams of autonomous (robotic) mobile units that cooperate to achieve a common goal. Providing real-time communication among the team units is highly desirable for guaranteeing a predictable behavior in those applications in which the robots have to operate autonomously in unstructured environments. This paper proposes a MAC protocol for wireless communication that supports dynamic resource reservation and topology management for relatively small networks of cooperative units (10–20 units). The protocol uses a slotted time-triggered medium access transmission control that is collision-free, even in the presence of hidden nodes. The transmissions are scheduled according to the earliest deadline first scheduling policy. An adequate admission control guarantees the timing constraints of the team communication requirements, including when new nodes dynamically join or leave the team. The paper describes the protocol focusing on the consensus procedure that supports coherent changes in the global system. We also introduce a distributed connectivity tracking mechanism that is used to detect network partition and absent or crashed nodes. Finally, a set of simulation results are shown that illustrate the effectiveness of the proposed approaches.

Electric loads as Real-Time tasks: An application of Real-Time Physical Systems

This paper describes the application of Real-Time Physical Systems (RTPS) as a novel approach to model the physical process of Cyber-Physical Systems (CPS), with specific focus on Cyber-Physical Energy Systems (CPES). The proposed approach is based on the real-time scheduling theory which is nowadays developed to manage concurrent computing tasks on processing platforms. Therefore, the physical process is modeled in terms of real-time parameters and timing constraints, so that real-time scheduling algorithms can be applied to manage the timely allocation of resources. The advantage is to leverage the strong mathematical background of real-time systems in order to achieve predictability and timing correctness on the physical process behind the considered CPS. The paper provides an introduction to the possible application of RTPS to energy systems. The analogy between real-time computing systems and energy systems is presented; moreover, the relationship between RTPS and related research fields is traced. Finally, the introduced techniques are proposed to optimize the peak load of power consumption in electric power systems. This method is suitable for systems spanning from small networks to smart grids.

Towards the powerline alternative in automotive applications

The power line technology has received an increasing attention in the last decades due to its inherent benefits, mainly related to the reduction of cabling and associated costs. Power line communication (PLC) was first employed in power utilities and since the 80s in home automation, too. However, its use in the automotive field received relatively little attention. This paper revisits the related work in using PLC technology for communication within the automotive domain and outlines its possible benefits. Then, it focuses on the issues that need to be addressed when introducing the PLC in the automotive domain. The final goal of this work is to carry out a practical assessment of the PLC technology in the referred domain that may open the way for future use in industrial scale.

Requirements for building an ontology for autonomous robots

IEEE Ontologies for Robotics and Automation Working Group were divided into subgroups that were in charge of studying industrial robotics, service robotics and autonomous robotics. This paper aims to present the work in-progress developed by the autonomous robotics (AuR) subgroup. This group aims to extend the core ontology for robotics and automation to represent more specific concepts and axioms that are commonly used in autonomous robots.,For autonomous robots, various concepts for aerial robots, underwater robots and ground robots are described. Components of an autonomous system are defined, such as robotic platforms, actuators, sensors, control, state estimation, path planning, perception and decision-making.,AuR has identified the core concepts and domains needed to create an ontology for autonomous robots.,AuR targets to create a standard ontology to represent the knowledge and reasoning needed to create autonomous systems that comprise robots that can operate in the air, ground and underwater environments. The concepts in the developed ontology will endow a robot with autonomy, that is, endow robots with the ability to perform desired tasks in unstructured environments without continuous explicit human guidance.,Creating a standard for knowledge representation and reasoning in autonomous robotics will have a significant impact on all R&A domains, such as on the knowledge transmission among agents, including autonomous robots and humans. This tends to facilitate the communication among them and also provide reasoning capabilities involving the knowledge of all elements using the ontology. This will result in improved autonomy of autonomous systems. The autonomy will have considerable impact on how robots interact with humans. As a result, the use of robots will further benefit our society. Many tedious tasks that currently can only be performed by humans will be performed by robots, which will further improve the quality of life. To the best of the authors’knowledge, AuR is the first group that adopts a systematic approach to develop ontologies consisting of specific concepts and axioms that are commonly used in autonomous robots.

Real-Time Modeling and Control of Electric Vehicles Charging Processes

This paper presents a method for the real-time management of electric vehicles (EVs) charging processes. The proposed method aims to limit the peak load and to increase the number of rechargeable EVs with respect to the scenario in which no coordination action is performed, while achieving given constraints on the power distribution system. The approach is based on a tight interaction between a scheduling algorithm and a power-flow evaluation procedure. The scheduling algorithm finds the best charging periods for each EV. The power flow procedure checks the achievement of electrical constraints and evaluates the operational parameters of the grid. Simulations are carried out on a real electricity distribution system of a medium-sized Italian city. The results show that the proposed approach increases the number of rechargeable EVs up to 33%. At the same time, the peak load is reduced by 25%. The scheduling algorithm requires an average of 50 ms to evaluate each charge request on an ordinary computer, therefore allowing its use in real-time conditions.

Feedback scheduling of real-time physical systems with integrator dynamics

This paper addresses the application of real-time scheduling for the reduction of the peak load of power consumption generated by electric loads in a power system. The considered physical processes are characterized by integrator dynamics and modeled as sporadic real-time activities. To enable the applicability in realistic scenarios, modeling approximations and uncertainties on physical parameters are explicitly included in the model. A feedback control strategy is proposed to guarantee the requirements on physical values under control in presence of modeling and measurement uncertainties. To compensate for such uncertainties, the value of timing parameters used by the scheduler are dynamically adapted. Formal results have been derived to put into relationship the values of quantities describing the physical process with real-time parameters used to model and to schedule the activation of loads.