1,720,972 research outputs found
World Automata: a compositional approach to model implicit communication in hierarchical Hybrid Systems
Get PDFWe propose an extension of Hybrid I/O Automata (HIOAs) to model agent systems and their implicit communication through perturbation of the environment, like localization of objects or radio signals diffusion and detection. The new object, called World Automaton (WA), is built in such a way to preserve as much as possible of the compositional properties of HIOAs and its underlying theory. From the formal point of view we enrich classical HIOAs with a set of world variables whose values are functions both of time and space. World variables are treated similarly to local variables of HIOAs, except in parallel composition, where the perturbations produced by world variables are summed. In such way, we obtain a structure able to model both agents and environments, thus inducing a hierarchy in the model and leading to the introduction of a new operator. Indeed this operator, called inplacement, is needed to represent the possibility of an object (WA) of living inside another object/environment (WA)
Modelling Implicit Communication in Multi-Agent Systems with Hybrid Input/Output Automata
Get PDFWe propose an extension of Hybrid I/O Automata (HIOAs) to model agent systems and their implicit communication through perturbation of the environment, like localization of objects or radio signals diffusion and detection. To this end we decided to specialize some variables of the HIOAs whose values are functions both of time and space. We call them world variables. Basically they are treated similarly to the other variables of HIOAs, but they have the function of representing the interaction of each automaton with the surrounding environment, hence they can be output, input or internal variables. Since these special variables have the role of simulating implicit communication, their dynamics are specified both in time and space, because they model the perturbations induced by the agent to the environment, and the perturbations of the environment as perceived by the agent. Parallel composition of world variables is slightly different from parallel composition of the other variables, since their signals are summed. The theory is illustrated through a simple example of agents systems
Fault Diagnosis of Hybrid Systems: an Onboard Camera Model
No full textIn this paper we apply a method for diagnosing faults on hybrid systems to a model of a camera mounted on a mobile robot. A hybrid system is a system mixing continuous and discrete behaviors that cannot be faithfully modeled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We use the well known framework of hybrid automata for modeling hybrid systems, and try do detect faults exploiting a Fault Diagnosis Game on them, with two players: the environment and the diagnoser. The environment controls the evolution of the system and chooses whether and when a fault occurs. The diagnoser observes the external behavior of the system and announces whether a fault has occurred or not. The case study we introduce here is a simplified model of a camera mounted on a mobile rover that has to take pictures of some defined locations of the environment. We add the possibility of a stuck fault on the camera motor to apply the theory and show its effectiveness
A game-theoretic approach to fault diagnosis and identification of hybrid systems
No full textPhysical systems can fail. For this reason the problem of identifying and reacting to faults has received a lot of attention in the control and computer science communities. In this paper we study the fault diagnosis problem for hybrid systems from a game-theoretical point of view. A hybrid system is a system mixing continuous and discrete behaviours that cannot be faithfully modelled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We model hybrid systems as Hybrid Automata and add distinguished actions to describe faults. We define a Fault Identification Game on them, using two players: the environment and the identifier. The environment controls the evolution of the system and chooses whether and when a fault occurs. The identifier observes the external behaviour of the system and announces whether a fault has occurred or not. Existence of a winning strategy for the identifier implies that faults can be detected correctly, while computing such a winning strategy corresponds to implementing an identifier for the system. We will show how to determine the existence of a winning strategy, and how to compute it, for all decidable classes of hybrid automata that admit a finite bisimulation quotient
A Game-Theoretic approach to Fault Diagnosis of Hybrid Systems
Get PDFPhysical systems can fail. For this reason the problem of identifying and reacting to faults has received a large attention in the control and computer science communities. In this paper we study the fault diagnosis problem for hybrid systems from a game-theoretical point of view. A hybrid system is a system mixing continuous and discrete behaviours that cannot be faithfully modeled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We use the well known framework of hybrid automata for modeling hybrid systems, and we define a Fault Diagnosis Game on them, using two players: the environment and the diagnoser. The environment controls the evolution of the system and chooses whether and when a fault occurs. The diagnoser observes the external behaviour of the system and announces whether a fault has occurred or not. Existence of a winning strategy for the diagnoser implies that faults can be detected correctly, while computing such a winning strategy corresponds to implement a diagnoser for the system. We will show how to determine the existence of a winning strategy, and how to compute it, for some decidable classes of hybrid automata like o-minimal hybrid automata
Deformation detection and tracking on continuous and deformable medical tools
No full textSoft robotics is an already established research field within the bio-inspired robotic community. The use of this material has the potentials to leads to machines that are more adaptable, capable, and safer than the existing ones. Different are the application domains where soft robots can be advantageous. Among them, one that seems very promising is related to Minimal Invasive Surgery. In order to advance toward the development of novel medical devices that act as a continuous, and that are capable to adapt their shape according to the needs, it is fundamental to provide them sensing ability. In this paper we present a novel method to measure deformations that occur over a continuum deformable device. Our approach uses a stretchable smart skin, and bases its sensing capabilities on a tomographic imaging technique that allow to have a distributed sensing independent from the underplaying design
Task Ontology Validation in Surgical Robotics
No full textIn this paper we present a method introducing the validation phase in the context of robotic-assisted surgery. We propose bere a method which, starting from medicai knowledge, is able to perform validation of a surgical robot, either telemanipulated or autonomous, during the task execution. This validation method takes into account the operator skills and can be used for training and for evaluating the safety of a surgical tool
A Smart Skin Based Measurement System for Abnormality Identification in Soft Tissue Palpation
No full textRecent advancements in robotic-assisted surgery have revolutionised the medical field by providing tools that
can be used to simplify operations, and recovery of the patients. However, the main drawback remains in the
lack of haptic feedback that these tools can provide. Hence, the use of such systems is limited in many surgical operations since the surgeon can only rely on visual information to evaluate tool-tissue interaction forces during surgery. In this paper we will focus on the palpation task to detect abnormalities. By using robotic systems, surgeons can no longer use long established techniques, such as manual tissue palpation, to identify and locate tissue abnormalities and hidden pathological lesions such as tumours. Although the problem has already been investigated in literature, the main objective of this paper is to attempt to tackle it from a different perspective with respect to the solutions available in literature. We propose a system that is a combination of a tomographic imaging technique and of a mechanical stimulation performed by a probe that applies a constant amount of force over the surface of a soft tissue. The measured values can be interpreted as an estimation of the stiffness of the underlying structure, thus giving us information about the presence of abnormalities. The experiments carried out using a simulated soft tissue show that the system can be used to detect the presence of inhomogeneity within a deformable structure by applying a constant pressure to the domain under investigation
Modeling Objects Moving in a Complex Environment with World Automata
No full textWe propose an extension of the Hybrid I/O Automaton (HIOA) model, where each automaton lives in a generic environment (called world), and interacts with it. We call this object as World Automaton (WA). Each WA occupies a specific position in the world and each position has properties that influence the automaton behavior. Furthermore, the automaton is able to affect the properties of the underlying world. We build our extension in such a way that a WA itself can be an environment for other WAs, thus allowing for nested world
Modeling and Verification of a Robotic Surgical System using Hybrid Input/Output Automata
No full textThe area of robotic surgical systems has to deal with several important safety aspects to ensure that the patient and the Operating Room staff are safe. A robotic surgical system has to fulfill specific safety requirements and to ensure that the system reacts like its specification. To this end, a verification process is necessary. In this paper an architecture for robotic surgery is modeled using the framework of Hybrid Input/Output Automata (HIOAs). A case study based on a surgical robotic operation scenario is presented and modeled using HIOAs. Exploiting the modularity and compositionality theory of HIOAs, the verification of the system is performed
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