1,354,390 research outputs found
A magnetic network approach to the transient analysis of synchronous machines
No full textThe technique for the simulation of the dynamic behaviour of rotating machines presented in the paper is based on an equivalent circuit representation of the magnetic configuration. The circuit parameters are obtained by a preliminary automated sequence of magnetostatic FEM analyses and take into account the local magnetic saturations. The adopted solution technique is based on an invariant network topology approach: its application, presented for the operation analysis of a low-power synchronous generator, allows a great reduction of the calculation time in comparison with a commercial FEM code for the transient simulation
Planar Pushing Manipulation with a Group of Mobile Robots
No full textThis paper addresses the problem of collaborative manipulation of an object performed by a group of robots. In particular, the objective is achieved by means of pushing, implemented by a group of small wheeled mobile robots. The proposed method exploits the well known Voronoi-based coverage control method to deploy the robots in the environment according to a given probability density function. The shape of such a density function is defined, in a time varying manner, by a pushing policy function to enable planar manipulations, considering only the footprint of the manipulated object. The proposed method is validated by means of extensive simulations and real world scenario experiments with different sized robot groups and different manipulated objects
Automated Procedure for the Performance Improvement of a Low-power Single-phase Synchronous Motor
No full textThe performance of a low power line-start single-phase synchronous motor is evaluated via a mathematical model, elaborating the results of an automated sequence of magnetostatic FEM analyses. Such an approach remarkably speeds up the transient simulation with respect to a commercial FEM code for the transient analysis, allowing analysis of the influence of the parametric variations in a reasonable lapse of time. An optimization procedure based on such a technique could be profitably applied to a self-starting single-phase synchronous motor
Streamlining Object Pushing: Behavior Tree-Based Coordination of Control and Planning
No full textEfficiently navigating and manipulating objects in complex environments is a fundamental challenge in robotics. This paper presents a novel approach to streamline object-pushing tasks by integrating Behavior Trees (BT) to coordinate a control and planning framework. The proposed system optimizes the execution of tasks involving the pushing of objects while ensuring adaptability to varying scenarios.Our approach employs BTs to encapsulate high-level task specifications and decision-making processes, facilitating a flexible and intuitive representation of robot behavior. By seamlessly integrating BT technology with a coordinated control and planning system, we enable the robot to make real-time decisions and adapt to dynamic environments.We present experimental results demonstrating the effectiveness of our approach, highlighting its ability to improve task execution efficiency and adaptability
Analytical formulation for design and optimization of permanent magnet arrays
No full textRare earth permanent magnet arrays are extensively used in many electromagnetic devices. Their
preliminary design can be eased by the analytical approach presented in this paper. It allows a fast evaluation of the flux density distribution and of the winding flux linkage and induced emf as functions of the configuration parameters and therefore can be particularly profitable to optimise the electromagnetic configuration
PredictMed-epilepsy: A multi-agent based system for epilepsy detection and prediction in neuropediatrics
No full textBackground and objective: Epileptic seizures are associated with a higher incidence of Developmental Disabilities and Cerebral Palsy. Early evaluation and management of epilepsy is strongly recommended. We propose and discuss an application to predict epilespy (PredictMed-Epilepsy) and seizures via a deep-learning module (PredictMed-Seizures) encompassed within a multi-agent based healthcare system (PredictMed-MHS); this system is meant, in perspective, to be integrated into a clinical decision support system (PredictMed-CDSS). PredictMed-Epilespy, in particular, aims to identify factors associated with epilepsy in children with Developmental Disabilities and Cerebral Palsy by using a prediction-learning model named PredictMed. PredictMed-epilespy methods: We performed a longitudinal, multicenter, double-blinded, descriptive study of one hundred and two children with Developmental Disabilities and Cerebral Palsy (58 males, 44 females; 65 inpatients, 37 outpatients; 72 had epilepsy - 22 of intractable epilepsy, age: 16.6±1.2y, range: 12–18y). Data from 2005 to 2021 on Cerebral Palsy etiology, diagnosis, type of epilepsy and spasticity, clinical history, communication abilities, behaviors, intellectual disability, motor skills, and eating and drinking abilities were collected. The machine-learning model PredictMed was exploited to identify factors associated with epilepsy. The guidelines of the “Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis” Statement (TRIPOD) were followed. PredictMed-epilepsy results: Cerebral Palsy etiology [(prenatal > perinatal > postnatal causes) p=0.036], scoliosis (p=0.048), communication (p=0.018) and feeding disorders (p=0.002), poor motor function (p<0.001), intellectual disabilities (p=0.007), and type of spasticity [(quadriplegia/triplegia > diplegia > hemiplegia), p=0.002)] were associated with having epilepsy. The prediction model scored an average of 82% of accuracy, sensitivity, and specificity. Thus, PredictMed defined the computational phenotype of children with Developmental Disabilities/Cerebral Palsy at risk of epilepsy. Novel contribution of the work: We have been developing and we have prototypically implemented a Multi-Agent Systems (MAS) that encapsulates the PredictMed-Epilepsy module. More specifically, we have implemented the Patient Observing MAS (PoMAS), which, as a novelty w.r.t. the existing literature, includes a complex event processing module that provides real-time detention of short- and long-term events related to the patient's condition
Manipolazione sul Piano tramite spinta: uno studio su manipolazione non prensile con un singolo robot mobile e con robot mobili multipli
No full textQuesta tesi di dottorato studia la manipolazione di oggetti mediante la spinta: una tecnica di manipolazione appartenente alla classe delle manipolazioni non prensili. Le tecniche di questa classe sfruttano la geometria dell'oggetto da manipolare insieme alle sue dinamiche e all'ambiente circostante per raggiungere il compito da svolgere.
Partendo dalla letteratura attuale, il primo problema affrontato è la generazione di un piano di spinta ottimale per manipolare un oggetto poligonale tramite azioni di spinta sui suoi lati da parte di un singolo robot mobile. La soluzione proposta è un algoritmo di pianificazione a due livelli. Il primo livello valuta la fattibilità della manipolazione calcolando un percorso verso la posa target dell'oggetto, considerando sia le dimensioni del robot che dell'oggetto. Questo percorso iniziale viene quindi utilizzato come guida per la ricerca di una serie di traiettorie di spinta per il robot. Queste traiettorie sono ottenute attraverso un problema di ottimizzazione che genera la traiettoria più corta possibile che soddisfi i vincoli di spinta.
Il passo successivo è generare un algoritmo di controllo che assicuri che il movimento del robot durante la manipolazione soddisfi i vincoli di spinta. Ciò si ottiene utilizzando il controllo predittivo. Il controller utilizza un modello del sistema per prevedere lo stato futuro e ottimizzarne il comportamento. Con MPC è anche possibile imporre dei vincoli al movimento del sistema. In particolare, si è imposto un vincolo per mantenere un contatto stabile tra l'oggetto e il robot durante la manipolazione. Ciò si ottiene inizialmente includendo le forze di contatto negli ingressi del sistema per prevedere il movimento dell'oggetto spinto. Tuttavia, siccome la previsione del moto di un oggetto spinto è spesso inaffidabile a causa dell'indeterminatezza dei fattori coinvolti, e la formulazione del vincolo è non lineare, la complessità della soluzione dell'ottimizzazione risulta alta. È stata quindi progettata una versione migliorata dell'algoritmo di controllo trasformando il vincolo in una formulazione lineare equivalente, più facile da calcolare.
L'ultimo componente necessario affinché un singolo robot esegua una manipolazione spingendo è un algoritmo di monitoraggio. Il progetto proposto definisce una macchina a stati finiti per l'esecuzione delle traiettorie di spinta, il monitoraggio della manipolazione e la gestione dei casi limite e dei possibili guasti. Lo studio della manipolazione della spinta con il sistema multi-robot è stato suddiviso in due direzioni di ricerca. Quando sono disponibili solo pochi robot per completare l'attività di spinta planare assegnata, è necessario disporli con attenzione attorno all'oggetto in base all'attività assegnata. Una caratterizzazione della qualità di una configurazione di contatto è stata definita per aiutare questa decisione, validata con metodi statistici. È stata studiata anche l'ottimizzazione iterativa di una data configurazione per un task, proponendo quindi una procedura per ottimizzare una configurazione. L'ottimizzazione proposta si avvale della caratterizzazione e di altre forme di stima della qualità di una configurazione. Quando il numero di robot è maggiore e potrebbe essere necessario che i robot spingano l'uno sull'altro, è necessario un approccio diverso. È stata quindi proposta una legge di controllo gerarchico per affrontare questi casi. La legge di controllo si avvale di schemi di controllo consolidati per coordinare il gruppo di robot secondo una distribuzione di probabilità, definita in base alla spinta da applicare. Sono stati condotti esperimenti per validare la strategia su diverse forme e differenti numerosità dei gruppi di robot.This doctoral dissertation studies the manipulation of objects using pushing: a manipulation technique from the class of non-prehensile manipulations.
Techniques from this class exploit the geometry of the object to manipulate together with its dynamics and the surrounding environment to achieve the task at hand. Starting from present literature, the first problem approached was the generation of an optimal pushing plan for manipulating a polygonal object using pushing actions by a single mobile robot. The proposed solution is a two-layer planning algorithm. The first layer evaluates the feasibility of the manipulation by computing a path to the target pose of the object, considering the dimentions of both robot and object. This initial path is then used as a guide to search for a set of pushing trajectories for the robot. These trajectories are obtained through an optimization problem that generates the shortest possible trajectory that satisfies the pushing constraints.
The next step is to generate a control algorithm that ensures that the motion of the robot during the manipulation satisfies the pushing constraints. This is achieved using Model Predictive Control. The controller makes use of a model of the system to predict the future state and optimize its behaviour. With MPC it is also possible to impose a set of constraints on the system motion. In particular, the interest here is imposing a constraint to maintain a sticking contact between the object and the robot during the manipulation. This is achieved at first by including the contact forces in the inputs of the system in order to predict the motion of the pushed object. A constraint is then formulated to ensure that the motion of the robot and the object are compatible. However, since the prediction of the motion of a pushed object is often unreliable due to the indeterminacy of the factors involved, and the formulation of the constraint is nonlinear. This increases the complexity of the solution of the optimization algorithm and therefore its time requirements. An improved version of the control algorithm was then designed transforming the constraint into an equivalent linear formulation, easier to compute.
The last component necessary for a single robot to perform a manipulation by pushing is a monitoring algorithm. The proposed design defines a finite state machine for the execution of the pushing trajectories, monitoring the manipulation and handling edge cases and possible failures.
The study of pushing manipulation with multi-robot system was split in two research direction, differentiated by the size of the robot group. When only a few robots are available to complete the assigned planar pushing task, it is necessary to carefully displace them around the object according to the assigned task. A characterization of the quality of a grasp configuration was defined to aid this decision. Its validity has been studied with statistical analysis from simulation data. The iterative optimization of a given configuration for a task was also studied, therefore proposing a procedure to optimize a pushing configuration. The proposed optimization makes use of the characterization as well as other forms of estimation of the quality of a configuration. When the number of robots is higher and it may be necessary to have the robots push on each other to combine the efforts, a different approach is necessary. A hierarchical control law was then proposed to address these cases. The control law makes use of established control schemes to coordinate the group of robots as if they were a probability distribution, therefore capable to adapt to any object shape and size. Experiments were carried out to validate the strategy on different objects and different group numerosity
La linea di influenza “speciale”: uno strumento utile alla costruzione dell’oscillogramma delle tensioni all’interno della procedura per le verifiche a fatica dei ponti
No full textLa presente memoria introduce la linea di influenza “speciale” come uno strumento analitico utile per la costruzione dell’oscillogramma delle tensioni per le verifiche a fatica dei ponti. Essa rappresenta gli effetti globali del passaggio sul ponte di un intero veicolo a più assi a distanze prefissate. La l.d.i. “speciale” è definita come la sommatoria, ascissa per ascissa, delle linee di influenza tradizionali opportunamente traslate della distanza relativa dei singoli assi del veicolo viaggiante. La memoria presenta anche una procedura generale per le verifiche a fatica dei ponti, che è illustrata mediante l'applicazione alla verifica a danneggiamento di un dettaglio costruttivo della mezzeria delle travi longitudinali di un ponte ad arco in acciaio a via inferiore.The present paper introduces the so-called “special” influence line as a useful analytical tool for the determination of the stress history for the fatigue verifications of bridges. It represents the global
effects of the passage of a vehicle with several axles at given distances. It is defined as the sum of the traditional influence lines which are properly shifted by the relative distances between each axle
and the first one. The paper also presents a general procedure for the bridges fatigue verifications, which is illustrated with reference to the cumulative damage method of a constructional detail of
the mid-span cross-section of the longitudinal girders of an arch steel bridge
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