Angelo Cenedese - Academia.edu (original) (raw)

Papers by Angelo Cenedese

IEEE Transactions on Control of Network Systems, 2021

This work focuses on bearing rigidity theory, namely the branch of knowledge investigating the st... more This work focuses on bearing rigidity theory, namely the branch of knowledge investigating the structural properties necessary for multi-element systems to preserve the inter-unit bearings under deformations. The contributions of this work are twofold. The first one consists in the development of a general framework for the statement of the principal definitions and properties of bearing rigidity. We show that this approach encompasses results existing in the literature, and also provides a systematic approach for studying bearing rigidity on any differential manifold in SE(3) n , where n is the number of agents. The second contribution is the derivation of a general form of the rigidity matrix, a central construct in the study of rigidity theory. We provide a necessary and sufficient condition for the infinitesimal rigidity of a bearing framework as a property of the rank of the rigidity matrix. Finally, we present two examples of multi-agent systems not encountered in the literature and we study their rigidity properties using the developed methods.

Nuclear Fusion, Mar 27, 2015

Since the installation of an ITER-like wall, the JET programme has focused on the consolidation o... more Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

Drosophila melanogaster is a model organism in genetics thanks to the compactness of its genome a... more Drosophila melanogaster is a model organism in genetics thanks to the compactness of its genome and its relative simplicity. Recently, certain developmental patterns in Drosophila have been studied by mathematical models, with the aim of gaining deeper and quantitative insight into the morphogenesis of this insect. There is a need for accurate dynamical of the epithelial cell structure and organization within the fly wing, to further the understanding of a phenomenon known as planar cell polarity. The present study tackles the problem of retrieving such a salient structure using classical tools of dynamical system theory embedded with network and graph concepts. On the one hand the goal is to provide a visual detection and representation of the cell packaging that is accurate and fine. Particular care is also put in obtaining a model of this structure, whose main features are the compactness and simplicity.

IFAC-PapersOnLine, Jul 1, 2017

A broad class of natural and man-made systems exhibits rich patterns of cluster synchronization i... more A broad class of natural and man-made systems exhibits rich patterns of cluster synchronization in healthy and diseased states, where different groups of interconnected oscillators converge to cohesive yet distinct behaviors. To provide a rigorous characterization of cluster synchronization, we study networks of heterogeneous Kuramoto oscillators and we quantify how the intrinsic features of the oscillators and their interconnection parameters affect the formation and the stability of clustered configurations. Our analysis shows that cluster synchronization depends on a graded combination of strong intra-cluster and weak inter-cluster connections, similarity of the natural frequencies of the oscillators within each cluster, and heterogeneity of the natural frequencies of coupled oscillators belonging to different groups. The analysis leverages linear and nonlinear control theoretic tools, and it is numerically validated.

IFAC Proceedings Volumes, Sep 1, 2012

We consider the distributed unconstrained minimization of separable convex cost functions, where ... more We consider the distributed unconstrained minimization of separable convex cost functions, where the global cost is given by the sum of several local and private costs, each associated to a specific agent of a given communication network. We specifically address an asynchronous distributed optimization technique called Newton-Raphson Consensus. Beside having low computational complexity, low communication requirements and being interpretable as a distributed Newton-Raphson algorithm, the technique has also the beneficial properties of requiring very little coordination and naturally supporting time-varying topologies. In this work we analytically prove that under some assumptions it shows either local or global convergence properties, and corroborate this result by the means of numerical simulations.

We consider the convergence rates of two convex optimization strategies in the context of multi a... more We consider the convergence rates of two convex optimization strategies in the context of multi agent systems, namely the Newton-Raphson consensus optimization and a distributed Gradient-Descent opportunely derived from the first. To allow analytical derivations, the convergence analyses are performed under the simplificative assumption of quadratic local cost functions. In this framework we derive sufficient conditions which guarantee the convergence of the algorithms. From these conditions we then obtain closed form expressions that can be used to tune the parameters for maximizing the rate of convergence. Despite these formulae have been derived under quadratic local cost functions assumptions, they can be used as rules-of-thumb for tuning the parameters of the algorithms in general situations.

We study the problem of unconstrained distributed optimization in the context of multi-agents sys... more We study the problem of unconstrained distributed optimization in the context of multi-agents systems subject to limited communication connectivity. In particular we focus on the minimization of a sum of convex cost functions, where each component of the global function is available only to a specific agent and can thus be seen as a private local cost. The agents need to cooperate to compute the minimizer of the sum of all costs. We propose a consensus-like strategy to estimate a Newton-Raphson descending update for the local estimates of the global minimizer at each agent. In particular, the algorithm is based on the separation of timescales principle and it is proved to converge to the global minimizer if a specific parameter that tunes the rate of convergence is chosen sufficiently small. We also provide numerical simulations and compare them with alternative distributed optimization strategies like the Alternating Direction Method of Multipliers and the Distributed Subgradient Method.

arXiv (Cornell University), Nov 4, 2015

We address the problem of distributed unconstrained convex optimization under separability assump... more We address the problem of distributed unconstrained convex optimization under separability assumptions, i.e., the framework where each agent of a network is endowed with a local private multidimensional convex cost, is subject to communication constraints, and wants to collaborate to compute the minimizer of the sum of the local costs. We propose a design methodology that combines average consensus algorithms and separation of timescales ideas. This strategy is proved, under suitable hypotheses, to be globally convergent to the true minimizer. Intuitively, the procedure lets the agents distributedly compute and sequentially update an approximated Newton-Raphson direction by means of suitable average consensus ratios. We show with numerical simulations that the speed of convergence of this strategy is comparable with alternative optimization strategies such as the Alternating Direction Method of Multipliers. Finally, we propose some alternative strategies which trade-off communication and computational requirements with convergence speed.

Mitochondrial Dynamics (MD) has recently emerged as one of the most interesting topics in biology... more Mitochondrial Dynamics (MD) has recently emerged as one of the most interesting topics in biology since the intricate connection between energy production and MD regulates cells development and function. On the other hand, the impairment of such mechanism is strictly related to the emergence of various diseases, among which neurodegenerative disorders. In this work, we provide a simple, yet self-consistent, and well-posed mathematical model to describe the MD and the related phenomena through a population-dynamics approach, together with the ATP-energy turnover, which is an important step to unravel the underlying dynamics of the whole cell system and has a key role in its quality control. With the tools of system theory, we highlight the positiveness of the system and the presence of non-zero equilibria and compute bounds for the involved system state quantities. Furthermore, we consider a situation of impairment in the MD and design a control law, based on input-output linearization and state-feedback control able to allow a damaged system to compensate for the defect and behave as a nominal one. In this scenario, we test two different protocols that could be suggestive for treatment strategies.

In this paper we study cluster synchronization in a network of Kuramoto oscillators, where groups... more In this paper we study cluster synchronization in a network of Kuramoto oscillators, where groups of oscillators evolve cohesively and at different frequencies from the neighboring oscillators. Synchronization is critical in a variety of systems, where it enables complex functionalities and behaviors. Synchronization over networks depends on the oscillators' dynamics, the interaction topology, and coupling strengths, and the relationship between these different factors can be quite intricate. In this work we formally show that three network properties enable the emergence of cluster synchronization. Specifically, weak inter-cluster connections, strong intra-cluster connections, and sufficiently diverse natural frequencies among oscillators belonging to different groups. Our approach relies on system-theoretic tools, and is validated with numerical studies.

This work presents a generalized formulation of the Snake model defining new terms for the intern... more This work presents a generalized formulation of the Snake model defining new terms for the internal and the external energy functionals. These modifications conjugate features of the object contour as well as the inside of the shape. The obtained model is significantly more accurate spatially on the image plane and temporally on the frame sequence. In particular, the application to single cell analysis is in focus: In this context, we show how to cast the specific problem into the extended framework we propose. Shape descriptors and suitable metrics are then derived from the curve representation. The boundary identification produced through the classic formulation shows a poor and imprecise segmentation and leads to misleading metrics. The new model instead represents the boundary and the derived shape parameters in a way more consistent with the visual perception of shape evolution and deformation.

ABSTRACT Camera positioning units for surveillance applications are often mounted on mobile suppo... more ABSTRACT Camera positioning units for surveillance applications are often mounted on mobile supports or vehicles. In such circumstances, the motion of the supporting base affects the camera field of view, thus making the task of pointing and tracking a specific target problematic, especially when using low cost devices that are usually not equipped with rapid actuators and fast video processing units. Visual tracking capabilities can be improved if the camera field of view is preliminarily stabilized against the movements of the base. Although some cameras available on the market are already equipped with an optical image stabilization (OIS) system, implemented either in the camera lenses or in the image sensor, these are usually too expensive to be installed on low-end positioning devices. A cheaper approach to image stabilization consists of stabilizing the camera motion using the motors of the positioning unit and the inertial measurements provided by a low-cost MEMS Inertial Measurement Unit (IMU). This paper explores the feasibility of applying such image stabilization system to a low cost pan-tilt-zoom (PTZ) camera positioning unit driven by hybrid stepper motors (HSMs), in order to aid the task of pointing and tracking of a specific target on the camera image plane. In the proposed solution, a two-level cascaded control structure, consisting of inner inertial stabilizing control loop and an outer visual servoing control loop, is used to control the PTZ unit. Several tests are carried out on a real device mounted on a moving table actuated by a 6 degrees-of-freedom pneumatic hexapod. Realistic motions are recreated by using the data recordings taken aboard of a patrolling ship.

IFAC Proceedings Volumes, 2014

We consider the problem of building a transitional model of an initially uncalibrated camera netw... more We consider the problem of building a transitional model of an initially uncalibrated camera network. More specifically, we discuss a Hidden Markov Model (HMM) based strategy in which the model's state-space is defined in terms of a partition of the physical network coverage. Transitions between any two such states are described by the distribution of the underlying Markov Process. Extending previous work in (Cenedese et al., 2010), we show how it is possible to infer the model structure and parameters from coordinate free observations and we introduce a novel performance index for model validation. We moreover show the predictive power of this HMM approach in simulated and real settings that comprise Pan-Tilt-Zoom (PTZ) cameras.

2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2020

Cooperative robotics is a trending topic nowadays as it makes possible a number of tasks that can... more Cooperative robotics is a trending topic nowadays as it makes possible a number of tasks that cannot be performed by individual robots, such as heavy payload transportation and agile manipulation. In this work, we address the problem of cooperative transportation by heterogeneous, manipulatorendowed robots. Specifically, we consider a generic number of robotic agents simultaneously grasping an object, which is to be transported to a prescribed set point while avoiding obstacles. The procedure is based on a decentralized leader-follower Model Predictive Control scheme, where a designated leader agent is responsible for generating a trajectory compatible with its dynamics, and the followers must compute a trajectory for their own manipulators that aims at minimizing the internal forces and torques that might be applied to the object by the different grippers. The Model Predictive Control approach appears to be well suited to solve such a problem, because it provides both a control law and a technique to generate trajectories, which can be shared among the agents. The proposed algorithm is implemented using a system comprised of a ground and an aerial robot, both in the robotic Gazebo simulator as well as in experiments with real robots, where the methodological approach is assessed and the controller design is shown to be effective for the cooperative transportation task.

We will consider the three phases of the procedure and approach the methodological issues of inte... more We will consider the three phases of the procedure and approach the methodological issues of interest in order to compute the structure of interest in the image. 1) Detection. The first available image frame is analyzed searching for an underlying network structure, which is then extracted leveraging the use of a random walk model to navigate the network edges combined with a network agent to organize the retrieved information into a complex structure. The first frame is taken as a reference frame, also for the warping function w and the outcome of this procedure is a network graph (vertices, edges) with spatial information. 2) Tracking. The networked structure is then deformed in time starting from the information given by the reference frame and according to the visual data

2021 European Control Conference (ECC), 2021

Active Search and Tracking for search and rescue missions or collaborative mobile robotics relies... more Active Search and Tracking for search and rescue missions or collaborative mobile robotics relies on the actuation of a sensing platform to detect and localize a target. In this paper we focus on visually detecting a radio-emitting target with an aerial robot equipped with a radio receiver and a camera. Visualbased tracking provides high accuracy, but the directionality of the sensing domain often requires long search times before detecting the target. Conversely, radio signals have larger coverage, but lower tracking accuracy. Thus, we design a Recursive Bayesian Estimation scheme that uses camera observations to refine radio measurements. To regulate the camera pose, we design an optimal controller whose cost function is built upon a probabilistic map. Theoretical results support the proposed algorithm, while numerical analyses show higher robustness and efficiency with respect to visual and radio-only baselines.

2019 27th Mediterranean Conference on Control and Automation (MED), 2019

In this work, it is presented the development of a novel distributed algorithm performing robotic... more In this work, it is presented the development of a novel distributed algorithm performing robotic coverage, clustering and dispatch around an event in static-obstaclestructured environments without relying on metric information. Specifically, the aim is to account for the trade-off between local communication given by bearing visibility sensors installed on each agent involved, optimal deployment in closed unknown scenarios and focus of a group of agents on one point of interest. The particular targets of this study can be summarized as 1. the computation, under certain topological assumptions, of a lower bound for the number of required agents, which are provided by a realistic geometric model (e.g. a round shape) to emphasize physical limitations; 2. the minimization of the number of nodes and links maintaining a distributed approach over a connected communication graph; 3. the identification of an activation cluster around an event with a radial decreasing intensity, sensed by each agent; 4. the attempt to send the agents belonging to the cluster towards the most intense point in the scenario by minimizing a weighted isoperimetric functional.

NeuroImage, 2021

The functional architecture of the resting brain, as measured with the blood oxygenation level-de... more The functional architecture of the resting brain, as measured with the blood oxygenation level-dependent functional connectivity (BOLD-FC), is slightly modified during task performance. In previous work, we reported behaviorally relevant BOLD-FC modulations between visual and dorsal attention regions when subjects performed a visuospatial attention task as compared to central fixation (Spadone et al., 2015). Here we use magnetoencephalography (MEG) in the same group of subjects to identify the electrophysiological correlates of the BOLD-FC modulation found in our previous work. While BOLD-FC topography, separately at rest and during visual attention, corresponded to neuromagnetic Band-Limited Power (BLP) correlation in the alpha and beta bands (8-30 Hz), BOLD-FC modulations evoked by performing the visual attention task (Spadone et al. 2015) did not match any specific oscillatory band BLP modulation. Conversely, following the application of an orthogonal spatial decomposition that identifies common inter-subject co-variations, we found that attention-rest BOLD-FC modulations were recapitulated by multi-spectral BLP-FC components. Notably, individual variability of alpha connectivity between Frontal Eye Fields and visual occipital regions, jointly with decreased interaction in the Visual network, correlated with visual discrimination accuracy. In summary, task-rest BOLD connectivity modulations match multi-spectral MEG BLP connectivity.

IFAC-PapersOnLine, 2020

In aerial robotics, path following constitutes a popular task requiring a vehicle to pursue a giv... more In aerial robotics, path following constitutes a popular task requiring a vehicle to pursue a given trajectory. Resting upon the fulfillment of a desired time law, trajectory tracking techniques often turn out to be ineffective in presence of external disturbances, favoring the adoption of maneuver regulation strategies wherein the desired trajectory is parameterized in terms of the path-variable. In this scenario, this work proposes a new delay-compensating maneuver regulation controller for fully actuated aerial vehicles, whose aim is to guarantee the perfect tracking of a given path in the shortest time interval. The innovative aspect of such a solution relies on the introduction of a recovery term that compensates for possible delays in the task execution. The dual-quaternion formalism is adopted to model the dynamics of the aerial platforms allowing feedback linearization of the whole system, including both position and attitude, with a single controller. The tests conducted in Gazebo physics simulator show that the proposed controller outperforms the popular trajectory tracking PID regulators.