20XX
A. Cenedese, G.A. Susto, M. Terzi.
A Parsimonious Approach for Activity Recognition with Wearable Devices: an Application to Cross-country Skiing. European Control Conference 2016 (ECC'16) [submitted], 20XX
Abstract:
With the aim of monitoring the human activity,
wearable devices provide an enhanced usability and a seamless
human experience with respect to other portable devices (e.g.
smartphones) in critical tasks as well as in leisure and sport
activities. At the same time, though, wearable devices are more
resource-constrained in terms of computational capability and
memory, which calls for the design of algorithmic solutions
that explicitly take into account these issues. In this paper, a
parsimonious approach for activity recognition with wearable
devices is presented. The methodology is based on Relevant
Vector Machines (RVMs), a sparse machine learning framework
for classification, and allows to tackle the activity recognition
problem by identifying the two phases of Event Identification
and Gesture Recognition. The performance of the presented
methodology is tested on the interesting case study of cross-
country skiing (classic style): such a dataset presents three
different classes of gestures in addition to non-gesture activities
and has been obtained by recording the training sessions
of a heterogeneous set of executors in different environment
conditions.
[ abstract ] [
BibTeX]
A. Cenedese, M. Michielan, F. Tramarin, S. Vitturi.
An Energy Efficient Ethernet Strategy Based on Traffic Prediction and Shaping. IEEE Transactions on Communications [submitted], 20XX
Abstract:
Recently, different communities in computer science, telecommunication and control systems have devoted a huge effort towards the design of energy efficient solutions for data transmission and network management. This paper collocates along this research line and presents a novel energy efficient strategy conceived for Ethernet networks. The proposed strategy combines the statistical properties of the network traffic with the opportunities offered by the IEEE 802.3az amendment to the Ethernet standard, called Energy Efficient Ethernet (EEE). This strategy exploits the possibility of predicting the incoming traffic from the analysis of the current data flow, which typically presents a self-similar behavior. Based on the prediction, Ethernet links can then be put in a low power consumption state for the intervals of time in which traffic is expected to be of low intensity. Theoretical bounds are derived that detail how the performance figures depend on the parameters of the designed strategy and scale with respect to the traffic load. Furthermore, simulations results, based on both real and synthetic traffic traces, are presented to prove the effectiveness of the strategy, which leads to considerable energy savings at the cost of only a limited bounded delay in data delivery.
[ abstract ] [
BibTeX]
S. Borile, A. Pandharipande, D. Caicedo, A. Cenedese, L. Schenato.
An identification approach to lighting control. European Control Conference 2016 (ECC'16) [submitted], 20XX [
pdf] [
BibTeX]
G. Bianchin, A. Cenedese, M. Luvisotto, G. Michieletto.
Distributed Fault Detection in Sensor Networks via Clustering and Consensus. 54th Conference on Decision and Control (CDC15) - [accepted], 20XX
Abstract:
In this paper we address the average consensus problem in a Wireless Sensor-Actor Network with the particular focus on autonomous fault detection. To this aim, we design a distributed clustering procedure that partitions the network into clusters according to both similarity of measurements and communication connectivity. The exploitation of clustering techniques in consensus computation allows to obtain the detection and isolation of faulty nodes, thus assuring the convergence of the other nodes to the exact consensus value. More interestingly, the algorithm can be integrated into a Kalman filtering framework to perform distributed estimation of a dynamic quantity in presence of faults. The proposed approach is validated through numerical simulations and tests on a real world scenario dataset.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, G. Michieletto.
Distributed Strategies for Rotation Synchronization in SO(2) for a Camera Network. European Control Conference 2016 (ECC'16) [submitted], 20XX
Abstract:
Smart camera networks are probably one of the
more interesting examples of sensor-actor networks for the
opportunities of controlled sensing they offer. In such systems,
the problem of autonomous rotation synchronization of the
camera nodes is crucial and finds some of its motivations in
the possible dynamic change of topology (e.g. in smartphone
camera networks) or in the complexity of the network (e.g. in
large scale surveillance networks). In this work, the focus is on
the orientation estimation problem in planar camera systems, a
typical situation that occurs with perimeter surveillance systems
where rotation synchronization can be formalized in terms of
the minimization of a suitable cost function in SO(2) w.r.t. the
node absolute poses: this problem can be solved through a
distributed consensus strategy driven by noisy relative mea-
surements. To this aim, the analytic solution to the problem
and two distributed iterative schemes are derived, establishing
a connection between the convergence to the optimal rotation
estimation and the theory of the stochastic matrices that
describe the network highlighting the role of the topological
links that define the neighborhood of a camera node. The
theoretical findings are compared and validated with respect
to the convergence behavior also considering different network
topologies by means of numerical simulations.
[ abstract ] [
BibTeX]
G. Baggio, A. Cenedese, G. Michieletto.
On the Rotation Estimation Problem for Camera Networks. IEEE Robotics and Automation Letters and ICRA [submitted], 20XX [
BibTeX]
A. Cenedese, C. Favaretto.
On the synchronization of spatially coupled oscillators. 54th Conference on Decision and Control (CDC15) - [accepted], 20XX
Abstract:
Over the past decade, considerable attention has
been devoted to the problem of emergence of synchronization
patterns in a network of coupled oscillators, which can be
observed in a variety of disciplines, both in the biological and
in the engineering fields. In this context, the Kuramoto model
is a classical model for describing synchronization phenomena
that arise in large-scale systems that exploit local information
and interactions. In this work, an extension of such a model is
presented, that considers also the spatial distances among the
oscillator nodes. In particular, coupling strength and spatial
conditions are derived, needed to reach phase cohesiveness
and frequency synchronization, both in the scenario when a
single population of agents is present and when two different
populations interact. These theoretical findings are confirmed
by extensive numerical Monte Carlo simulations and statistical
analysis.
[ abstract ] [
url] [
BibTeX]
2015
A. Cenedese, M. Fagherazzi, P. Bettini.
A Novel Application of Selective Modal Analysis to Large-Scale Electromagnetic Devices. IEEE Transactions on Magnetics, 2015
Abstract:
In the analysis and design of large-scale dynamical systems, model reduction techniques aim at yielding a reasonable trade-off
between the contrasting needs of reducing the number of states and of reaching a good approximation of the overall system behavior.
In the specific case of complex electromagnetic devices, a large number of state variables represent physical quantities in the overall
system. This work collocates along this line of research and aims at studying Model Order Reduction techniques that maintain the
mathematical formalism of system theory but at the same time keep consistency with the physics of the phenomena of interest.
[ abstract ] [
url] [
BibTeX]
A. Pandharipande, M. Rossi, D. Caicedo, L. Schenato, A. Cenedese.
Centralized lighting control with luminaire-based occupancy and light sensing. Proc. of the IEEE Int. Conf. on Industrial Informatics 2015 (INDIN 2015), pp. CD-007153, 2015
Abstract:
We consider control of multiple luminaires with a
central controller and distributed occupancy and light sensors
co-located at the luminaires. The sensors periodically provide
local occupancy state and illumination information to the central
controller. Using this sensor feedback, the central controller
determines the dimming levels of the luminaires so as to adapt
artificial light output to changing daylight levels and occupancy
conditions, in an energy efficient way. We propose a multi-
variable feedback controller and compare its performance with
a simple stand-alone proportional-integral controller. We show
via simulations in an open-plan office lighting system that the
proposed controller has better performance in terms of achieving
the reference set-points.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, G.A. Susto, G. Belgioioso, G.I. Cirillo, F. Fraccaroli.
Home Automation Oriented Gesture Classification From Inertial Measurements. IEEE Transactions on Automation Science and Engineering, vol. 12(4), pp. 1200--1210, 2015
Abstract:
In this paper, a Machine Learning (ML) approach is presented that exploits accelerometers data to deal with gesture recognition (GR) problems. The proposed methodology aims at providing high accuracy classi?cation for Home Automation systems, which are generally user independent, device independentand device orientation independent, an heterogeneous scenario that was not fully investigated in previous GR literature. The approach illustrated in this work is composed of three main steps: event identi?cation, feature extraction and ML-based classi?cation; elements of novelty of the proposed approach are:
1. a pre-processing phase based on Principal Component Analysis to increase the performance in real-world scenario conditions;
2.the development of parsimonious novel classi?cation techniques based on Sparse Bayesian Learning.
This methodology is tested on two datasets of 4 gesture classes (horizontal, vertical, circles and eight-shaped movements) and on a further dataset with 8 classes. In order to authentically describe a real-world Home Automation environment, the gesture movements are collected from more than 30 people who freely perform any gesture. It results a dictionary of 12 and 20 different movements respectivelyin the case of the 4-class and the 8-class databases.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, M. Fagherazzi, P. Bettini.
Model Reduction Techniques for the Analysis and the Design of Large-Scale Electromagnetic Devices. Proceedings of the Conference on the Computation of Electromagnetic Fields (COMPUMAG 2015), pp. PC4 - 7, 2015
Abstract:
In the analysis and design of large-scale dynamical systems, simpler models are often preferred to full system models due to
their better suitability with computer simulations and real-time constraints. Model reduction techniques aim at yielding a reasonable
trade-off between the contrasting needs of reducing the number of states and of reaching a good approximation of the overall system
behavior. In the specific case of complex electromagnetic devices (as fusion machines) a large number of state variables represent
physical quantities in the overall system, such as currents, voltages, magnetic flux densities and so on. Since it would be important
not to loose this valuable feature while reducing the order of the system, we focus on the Selective Modal Analysis (SMA) technique
which allows to preserve this meaning resorting to a state selection according to the contribution of the single states to the model
modes. The application of various MOR techniques to the numerical models of the ITER machine is discussed.
[ abstract ] [
url] [
BibTeX]
D. Varagnolo, F. Zanella, A. Cenedese, G. Pillonetto, L. Schenato.
Newton-Raphson Consensus for Distributed Convex Optimization. IEEE Transactions on Automatic Control, 2015
Abstract:
We address the problem of distributed unconstrained convex optimization under separability assumptions, i.e., the framework where a network of agents, each endowed with local private multidimensional convex cost and subject to communication constraints, 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 time-scales ideas. This strategy is proven, 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.
[ abstract ] [
url] [
pdf] [
BibTeX]
M. Rossi, A. Pandharipande, D. Caicedo, L. Schenato, A. Cenedese.
Personal lighting control with occupancy and daylight adaptation. Energy and Buildings, vol. 105pp. 263–-272, 2015
Abstract:
Personal control with occupancy and daylight adaptation is considered in
a lighting system with multiple luminaires. Each luminaire is equipped
with a co-located occupancy sensor and light sensor that respectively
provide local occupancy and illumination information to a central
controller. Users may also provide control inputs to indicate a desired
illuminance value. Using sensor feedback and user input, the central
controller determines dimming values of the luminaires using an
optimization framework. The cost function consists of a weighted sum of
illumination errors at light sensors and the power consumption of the
system. The optimum dimming values are determined with the constraints
that the illuminance value at the light sensors are above the reference
set-point at the light sensors and the dimming levels are within
physical allowable limits. Different approaches to determine the
set-points at light sensors associated with multiple user illumination
requests are considered. The performance of the proposed constrained
optimization problem is compared with a reference stand-alone controller
under different simulation scenarios in an open-plan office lighting
system.
[ abstract ] [
url] [
BibTeX]
2014
G. Belgioioso, A. Cenedese, G.I. Cirillo, F. Fraccaroli, G.A. Susto.
A Machine Learning based Approach for Gesture Recognition from Inertial Measurements. IEEE 53rd Conference on Decision and Control, pp. 4899--4904, 2014
Abstract:
The interaction based on gestures has become a
prominent approach to interact with electronic devices. In this
paper a Machine Learning (ML) based approach to gesture
recognition (GR) is illustrated; the proposed tool is freestanding
from user, device and device orientation. The tool has been
tested on a heterogeneous dataset representative of a typical
application of gesture recognition. In the present work two novel
ML algorithms based on Sparse Bayesian Learning are tested
versus other classification approaches already employed in
literature (Support Vector Machine, Relevance Vector Machine,
k-Nearest Neighbor, Discriminant Analysis). A second element
of novelty is represented by a Principal Component Analysis-
based approach, called Pre-PCA, that is shown to enhance
gesture recognition with heterogeneous working conditions.
Feature extraction techniques are also investigated: a Principal
Component Analysis based approach is compared to Frame-
Based Description methods.
[ abstract ] [
url] [
pdf] [
BibTeX]
A. Masiero, A. Cenedese.
Affinity-based Distributed Algorithm for 3D Reconstruction in Large Scale Visual Sensor Networks. Proceedings of the American Control Conference (ACC2014), pp. 4671--4676, 2014
Abstract:
In recent years, Visual Sensor Networks (VSNs) have emerged as an interesting category of distributed sensor- actor systems to retrieve data from the observed scene and produce information. Indeed, the request for accurate 3D scene reconstruction in several applications is leading to the development of very large systems and more specifically to large scale motion capture systems. When dealing with such huge amount of data from a large number of cameras it becomes very hard to make real time reconstruction on a single machine.
Within this context, a distributed approach for reconstruc- tion on large scale camera networks is proposed. The approach is based on geometric triangulation performed in a distributed fashion on the computational grid formed by the camera net- work organized into a tree structure. Since the computational performance of the algorithm strongly depends on the order in which cameras are paired, to optimize the efficiency of the reconstruction a pairing strategy is designed that relies on an affinity score among cameras. This score is computed from a probabilistic perspective by studying the variance of the 3D target reconstruction error and resorting to a normalized cut graph partitioning.
The scaling laws and the results obtained in simulation suggest that the proposed optimization strategy allows to obtain a significant reduction of the computational time.
[ abstract ] [
url] [
pdf] [
BibTeX]
M. Michielan, A. Cenedese, F. Tramarin, S. Vitturi.
An Energy Efficient Traffic Shaping Algorithm for Ethernet-Based Multimedia Industrial Traffic. Work-in-Progress/Industry Practice ETFA 2014 - IEEE Int. Conf. on Emerging Technology & Factory Automation, pp. PF-006912, 2014
Abstract:
Industrial communication systems, like the very
popular real-time Ethernet networks, are ever more used to carry
multimedia traffic, i.e. that generated by applications employing
complex sensors such as, for example, video cameras. Ethernet
networks, however, revealed to be quite inefficient in terms of
energy saving since the power consumption of a link between any
two devices does not decrease significantly during the (statistically
long) idle periods, i.e. the intervals of time in which the link is not
crossed by traffic. In this paper we present a novel traffic shaping
technique that aims at saving energy when the multimedia
industrial traffic has self similar characteristics. In particular,
the proposed method combines the statistical properties of the
traffic, with the opportunities offered by the recent amendment
to the Ethernet standard, called Energy Efficient Ethernet (EEE),
to design a strategy based on the analysis of current traffic levels
and the prediction of the incoming data flow. Simulation results
are presented to prove the effectiveness of the strategy which
leads to considerable energy savings at the expense of only a
limited bounded delay in frame delivery.
[ abstract ] [
url] [
BibTeX]
R. Lucchese, A. Cenedese, R. Carli.
An Hidden Markov Model based transitional description of camera networks. Proceedings of the 19th IFAC World Congress, pp. 7394-7399, 2014
Abstract:
We consider the problem of building a transitional model of an initially uncalibrated camera network. More specifically, we discuss an Hidden Markov Model (HMM) based strategy in which the model’s statespace is defined in terms of a partition of the physical network coverage. Transitions between any two such states are modeled 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 introduce a novel performance index that is used 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.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, F. Zanella.
Channel Model Identification in Wireless Sensor Networks Using a Fully Distributed Quantized Consensus Algorithm. Proceedings of the 19th IFAC World Congress, pp. 10349-10355, 2014
Abstract:
In this paper, we consider the problem of designing a distributed strategy to estimate the channel parameters for a generic Wireless Sensor-Actor Network. To this aim, we present a distributed least-square algorithm that complies with the constraint of transmitting only integer data through the wireless communication, which often characterizes Wireless Sensor-Actor Network embedded architectures. In this respect, we propose a quantized consensus strategy that mitigates the effects of the rounding operations applied to the wireless exchanged floating data. Moreover, the approach is based on a symmetric random gossip strategy, making it suitable for the actual deployment in multiagent networks. Finally, the effectiveness of the proposed algorithm and of its implementation as an open-source application is assessed and the employment of the procedure is illustrated through the application to radio-frequency localization experiments in a real world testbed.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Efficient algorithms for the reconstruction and prediction of atmospheric turbulence in AO systems. Proceedings of the European Control Conference (ECC14), pp. 2430 - 2435, 2014
Abstract:
Technological advances and the ever-growing human quest for improving
the resolution of telescope observations are motivating the design of
larger and larger ground telescopes: indeed, the larger is the telescope
lens diameter, the better is the diffraction limited resolution of the
telescope. Unfortunately, the terrestrial atmospheric turbulence, if not
properly compensated, negatively affects the telescope observations,
limiting its real resolution. Adaptive Optics (AO) systems are used in
large ground telescopes in order to compensate the effect of the
atmosphere, and hence to make the real telescope resolution be
determined by the diffraction properties of the lens.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Nonstationary multiscale turbulence simulation based on local PCA. ISA Transactions, 2014
Abstract:
Turbulence simulation methods are of fundamental importance for
evaluating the performance of control strategies for Adaptive Optics
(AO) systems. In order to obtain a reliable evaluation of the
performance a statistically accurate turbulence simulation method has to
be used. This work generalizes a previously proposed method for
turbulence simulation based on the use of a multiscale stochastic model.
The main contributions of this work are: first, a multiresolution local
PCA representation is considered. In typical operating conditions, the
computational load for turbulence simulation is reduced approximately by
a factor of 4, with respect to the previously proposed method, by means
of this PCA representation. Second, thanks to a different low
resolution method, based on a moving average model, the wind velocity
can be in any direction (not necessarily that of the spatial axes).
Finally, this paper extends the simulation procedure to generate, if
needed, turbulence samples by using a more general model than that of
the frozen flow hypothesis.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, A. Zanella, L. Vangelista, M. Zorzi.
Padova Smart City: an Urban Internet of Things Experimentation. Proceedings of the 2014 IEEE 15th International Symposium onA World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2014
Abstract:
“Smart City” is a powerful paradigm that applies the most advanced communication technologies to urban environments,
with the final aim of enhancing the quality of life in cities and provide a wide set of value-added services to both citizens
and administration. A fundamental step towards the practical realization of the Smart City concept consists in the development
of a communication infrastructure capable of collecting data from a large variety of different devices in a mostly uniform and
seamless manner, according to the Internet of Things (IoT) paradigm. While the scientific and commercial interest in IoT has been
constantly growing in the last years, practical experimentation of IoT systems has just begun. In this paper, we present and discuss
the Padova Smart City system, an experimental realization of an urban IoT system designed within the Smart City framework
and deployed in the city of Padova, Italy. We describe the system architecture and discuss the fundamental technical choices at
the base of the project. Then, we analyze the data collected by the system and show how simple data processing techniques can
be used to gain insights on the functioning of the monitored system, public traffic lighting in our specific case, as well as other
information concerning the urban environment.
[ abstract ] [
url] [
pdf] [
BibTeX]
A. Masiero, A. Cenedese.
Structure-based approach for optimizing distributed reconstruction in Motion Capture systems. Proceedings of the 19th IFAC World Congress, pp. 10914-10919, 2014
Abstract:
The diffusion of visual sensor networks, and in particular of smart camera networks, is motivating an increasing interest on the research of distributed solutions for several vision problems. Specifically, in this paper we propose a distributed solution to the problem of reconstructing target positions in large Motion Capture (MoCap) systems. Real time reconstruction by means of centralized procedures is practically unfeasible for very large systems, while the use of distributed computation allows to significantly reduce the computational time required for reconstruction, thus allowing the development of real time solutions.
Then the proposed distributed reconstruction procedure is optimized by exploiting information about the structure of the system: the visibility matrix states which objects in the scene are somehow measurable by a sensor (sensor-object matrix). Often, the typical localization of data from real application scenarios induces an underlying structure on the visibility matrix, that can be exploited to improve the performance of the system in understanding the surrounding environment. Unfortunately, usually these data are not properly organized in the visibility matrix: for instance, listing the sensors in a pseudo-random order can hide the underlying structure of the matrix. This paper considers the problem of recovering such underlying structure directly from the visibility matrix and designs an algorithm to perform this task.
Our simulations show that the distributed reconstruction algorithm optimized by means of the estimation of the structure of the visibility matrix allows a particularly relevant computational time reduction with respect to the standard (centralized) reconstruction algorithm.
[ abstract ] [
url] [
BibTeX]
2013
G. Marchiori, A. Cenedese, P. Merlo, F. Villone, E. Al.
Implementation and testing of a shape control system in RFX-mod Tokamak discharges. Proceedings of the 40th EPS Conference on Plasma Physics, 2013
Abstract:
In past years the Reversed Field Pinch RFX-mod has also been operated as a low current Tokamak to perform experiments of active control of MHD modes particularly harmful to a prospective reactor. The stabilization of m=2, n=1 mode has been achieved for 150 kA plasma currents in circular shape discharges at q(a)<2. In order to test the system capability of stabilizing such modes in improved confinement regimes, the possibility of producing D- shaped plasma discharges has been explored. Preliminary experiments were carried out in open loop in 2011. In the meantime a completely new plasma position and shape control system was designed and its performances simulated with the finite element 2D MHD equilibrium code MAXFEA. According to the simulation results, feedback control of the D- shape configuration was capable of meeting the design requirements. As a first step, the recent experimental campaign in Tokamak configuration was partially dedicated to demonstrate the possibility of a stable feedback controlled operation with an elongated plasma. In the paper the identification of the transfer function between a dedicated Field Shaping (FS) coil current distribution and the plasma elongation, the design of the control system, its implementation and successful testing are described.
[ abstract ] [
url] [
BibTeX]
R. Antonello, R. Oboe, D. Pilastro, S. Viola, I. Kazuaki, A. Cenedese.
IMU-based image stabilization in a HSM-driven camera positioning unit. Proceedings of the IEEE International Conference on Mechatronics (ICM 2013), pp. 156--161, 2013
Abstract:
Camera positioning units are widely used in surveillance and they are sometimes mounted on floating supports, e.g.
on patrolling ships or buoys. The support motion, in turn, induces an apparent motion in the image plane, which can create troubles to the image processing, especially when a specific feature must be tracked (e.g. a distant ship, getting close to a forbidden area). Low cost devices are often characterized by low frame rate and low image resolution, for which traditional image stabilization techniques usually results to be rather ineffective. Additionally, low-end camera units are usually driven by hybrid stepper motors and, being conceived to work in an harsh environment, they do not mount any optical image stabilization (OIS) system, either in the camera lenses or in the image sensor. In this paper, the image acquired by a pan–tilt camera positing unit mounted on a moving support is stabilized by exploiting the camera attitude information provided by a MEMS-based IMU with an embedded magnetometer. In particular, two independent integral control loops are designed for the pan and tilt motors in order to compensate for the yaw and pitch motions of the support. As for the roll motion, since it relates to an unavailable degree of freedom in the positioning unit, it can be compensated only on the captured image. The proposed solution is experimentally tested 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 and a costal buoy. Experimental results show that the proposed solution is capable of keeping the camera pointing at a fixed target with a good accuracy, thus making higher-level image processing easier and more effective.
[ abstract ] [
url] [
BibTeX]
R. Antonello, R. Oboe, A. Ramello, I. Kazuaki, A. Cenedese, N. Felicini.
IMU–aided image stabilization and tracking in a HSM–driven camera positioning unit. Proceedings of the IEEE International Symposium on Industrial Electronics (ISIE 2013), 2013
Abstract:
Camera positioning units for surveillance applica- tions 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.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Multiscale modeling for the simulation of not completely frozen flow turbulence. 3rd Adaptive Optics for Extreme Large Telescopes conference (AO4ELT3), 2013
Abstract:
Models typically used to simulate the
influence of atmospheric turbulence on ground telescope observations are
usually based on the frozen flow hypothesis. However, the frozen flow
model of the atmosphere is valid at time scales of the order of
tens/hundreds of milliseconds. This paper generalizes a previous model
for turbulence simulation to ensure reliable tests of AO system
performance in realistic working conditions. The proposed method relies
on the use of two simulation models: First, the part of turbulence that
shows a coherent flow at short time scales is simulated by means of a
multiscale autoregressive-moving average model, which allows to
efficiently simulate (with computational complexity O(n)) the coherent
evolution of the turbulence. Secondly, an approach similar to that
considered for dynamic textures, is used to simulate aberrations caused
by processes that evolve on much longer time scales. The proposed
procedure is tested on simulations.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Multiscale phase screens synthesis based on local PCA. Proceedings of the IEEE International Conference on Control & Automation (ICCA 2013), 2013
Abstract:
Motivated by the increasing importance of Adap- tive Optics (AO) systems for improving the real resolution of large ground telescopes, and by the need of testing the AO system performance in realistic working conditions, in this paper we address the problem of simulating the turbulence effect on ground telescope observations at high resolution. The multiscale approach presented here generalizes that in [3]: First, a relevant computational time reduction is obtained by exploiting a local spatial principal component analysis (PCA) representation of the turbulence. Furthermore, differently from [3], the turbulence at low resolution is modeled as a moving average (MA) process. While in [3] the wind velocity was restricted to be directed along one of the two spatial axes, the approach proposed here allows to evolve the turbulence indifferently in all the directions. In our simulations the pro- posed procedure reproduces with good accuracy the theoretical statistical characteristics of the turbulent phase.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Multiscale phase screens synthesis based on local PCA. Applied Optics, vol. 52(33), pp. 7987--8000, 2013
Abstract:
Motivated by the increasing importance of adaptive optics (AO) systems
for improving the real resolution of large ground telescopes, and by the
need of testing the AO system performance in realistic working
conditions, in this paper we address the problem of simulating the
turbulence effect on ground telescope observations at high resolution.
The procedure presented here generalizes the multiscale stochastic
approach introduced in our earlier paper [Appl. Opt. 50, 4124 (2011)],
with respect to the previous solution, a relevant computational time
reduction is obtained by exploiting a local spatial principal component
analysis (PCA) representation of the turbulence. Furthermore, the
turbulence at low resolution is modeled as a moving average (MA)
process, while previously [Appl. Opt. 50, 4124 (2011)] the wind velocity
was restricted to be directed along one of the two spatial axes, the
use of such MA model allows the turbulence to evolve indifferently in
all the directions. In our simulations, the proposed procedure
reproduces the theoretical statistical characteristics of the turbulent
phase with good accuracy.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
On the computation of Kalman gain in large adaptive optics systems. Proceedings of the 21st Mediterranean Conference on Control & Automation (MED13), pp. 1374-1379, 2013
Abstract:
In large ground telescopes the Adaptive Optics (AO) system aims at compensating the atmosphere effect on telescope measurements, and, the use of optimal filtering is fundamental for such task. This work is motivated by two important characteristics of new AO systems: on one hand, because of the request of very high measurement resolutions, the size of new telescopes, and of their sensors, is quickly increasing in the last decades, thus imposing to the AO systems the analysis of larger amount of data. On the other hand, the optimal filter has to be periodically updated according to temporal changes in atmosphere characteristics. Hence, it is of fundamental importance the use of computationally efficient algorithms for the update of the optimal filter gain.
This paper proposes some changes to a recently presented method for the efficient computation, in the frequency domain, of the Kalman gain for large AO systems [15]. The proposed changes, which mainly aim at correcting some issues due to the conversion spatial–frequency domain, and viceversa, allow to compute a better approximation of the optimal Kalman gain, and, consequently, significantly improve the performance of the AO system.
[ abstract ] [
url] [
BibTeX]
A. Cenedese, A. Beghi, A. Masiero.
On the estimation of atmospheric turbulence layers for AO systems. Proceedings of the ECC13 conference, pp. 4196-4201, 2013
Abstract:
In current and next generation of ground tele- scopes, Adaptive Optics (AO) are employed to overcome the detrimental effects induced by the presence of atmospheric turbulence, that strongly affects the quality of data transmission and limits the actual resolution of the overall system. The analysis as well as the prediction of the turbulent phase affecting the light wavefront is therefore of paramount importance to guarantee the effective performance of the AO solution.
In this work, a layered model of turbulence is proposed, based on the definition of a Markov-Random-Field whose pa- rameters are determined according to the turbulence statistics. The problem of turbulence estimation is formalized within the stochastic framework and conditions for the identifiability of the turbulence structure (numbers of layers, energies and velocities) are stated. Finally, an algorithm to allow the layer detection and characterization from measurements is designed. Numerical simulations are used to assess the proposed procedure and validate the results, confirming the validity of the approach and the accuracy of the detection.
[ abstract ] [
url] [
BibTeX]
Aavv, A. Cenedese.
Overview of the JET results with the ITER-like wall. Nuclear Fusion, vol. 53(10), pp. 1--19, 2013
Abstract:
Following the completion in May 2011 of the shutdown for the
installation of the beryllium wall and the tungsten divertor, the first
set of JET campaigns have addressed the investigation of the retention
properties and the development of operational scenarios with the new
plasma-facing materials. The large reduction in the carbon content (more
than a factor ten) led to a much lower Z_{eff}
(1.2–1.4) during L- and H-mode plasmas, and radiation during the
burn-through phase of the plasma initiation with the consequence that
breakdown failures are almost absent. Gas balance experiments have shown
that the fuel retention rate with the new wall is substantially reduced
with respect to the C wall. The re-establishment of the baseline H-mode
and hybrid scenarios compatible with the new wall has required an
optimization of the control of metallic impurity sources and heat loads.
Stable type-I ELMy H-mode regimes with H_{98,y2} close to 1 and ?_{N} ~ 1.6
have been achieved using gas injection. ELM frequency is a key factor
for the control of the metallic impurity accumulation. Pedestal
temperatures tend to be lower with the new wall, leading to reduced
confinement, but nitrogen seeding restores high pedestal temperatures
and confinement. Compared with the carbon wall, major disruptions with
the new wall show a lower radiated power and a slower current quench.
The higher heat loads on Be wall plasma-facing components due to lower
radiation made the routine use of massive gas injection for disruption
mitigation essential.
[ abstract ] [
url] [
BibTeX]
Aavv, A. Cenedese.
Preservation of micro-architecture and angiogenic potential in a pulmonary acellular matrix obtained using intermittent intra-tracheal flow of detergent enzymatic treatment. Biomaterials, vol. 34(28), pp. 6638-–6648, 2013
Abstract:
Tissue engineering of autologous lung tissue aims to become a
therapeutic alternative to transplantation. Efforts published so far in
creating scaffolds have used harsh decellularization techniques that
damage the extracellular matrix (ECM), deplete its components and take
up to 5 weeks to perform. The aim of this study was to create a lung
natural acellular scaffold using a method that will reduce the time of
production and better preserve scaffold architecture and ECM components.
Decellularization of rat lungs via the intratracheal route removed most
of the nuclear material when compared to the other entry points. An
intermittent inflation approach that mimics lung respiration yielded an
acellular scaffold in a shorter time with an improved preservation of
pulmonary micro-architecture. Electron microscopy demonstrated the
maintenance of an intact alveolar network, with no evidence of collapse
or tearing. Pulsatile dye injection via the vasculature indicated an
intact capillary network in the scaffold. Morphometry analysis
demonstrated a significant increase in alveolar fractional volume, with
alveolar size analysis confirming that alveolar dimensions were
maintained. Biomechanical testing of the scaffolds indicated an increase
in resistance and elastance when compared to fresh lungs. Staining and
quantification for ECM components showed a presence of collagen,
elastin, GAG and laminin. The intratracheal intermittent
decellularization methodology could be translated to sheep lungs,
demonstrating a preservation of ECM components, alveolar and vascular
architecture. Decellularization treatment and methodology preserves lung
architecture and ECM whilst reducing the production time to 3 h. Cell
seeding and in vivo experiments are necessary to proceed towards
clinical translation.
[ abstract ] [
url] [
BibTeX]
F. Zanella, A. Cenedese.
Teseo: a multi-agent tracking application in wireless sensor networks. International Journal of Systems Engineering, Applications and Development, vol. 7(1), pp. 42--55, 2013
Abstract:
In this work the design and implementation of an application to track multiple agents in a indoor Wireless Sensor Actor Network (WSAN) is proposed. We developed a tracking algorithm that falls into the category of the radio frequency localization/tracking methods, that exploit the strength of the wireless communications among fixed and mobile agents to establish the position of the mobile ones. The algorithm resorts to an Extended Kalman Filter to process the agents measurements and reach a desired level of tracking performance. The tracking application, namely Teseo, is composed by a low-level NesC management software for the agents side and a Java graphical interface provided to users connected to mobile agents. A detailed description of the operations performed by Teseo is given, accompanied both by simulations to validate the tracking algorithm and experiments on a real testbed to test Teseo.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Turbulence modeling and Kalman prediction for the control of large AO systems. Proceedings of the 52nd IEEE International Conference on Decision and Control (CDC2013) - accepted, 2013
Abstract:
Measurements of large ground telescopes are af- fected by the presence of the terrestrial atmospheric turbulence: local changes of the atmospheric refraction index (e.g. due to wind and temperature variations) cause a non flat surface of the wavefront of light beams incoming on the telescope, thus degrading the quality of the observed images. Adaptive Optics (AO) systems are of fundamental importance to reduce such atmospheric influence on ground telescopes and thus to obtain high resolution observations. The goal of the AO system is that of estimating and compensating the atmospheric turbulence effect by properly commanding a set of deformable mirrors.
Because of delays in the closed loop system, the Kalman filter plays an important role in ensuring an effective control perfor- mance by providing good atmosphere predictions. However, the need of periodically updating the Kalman filter gain because of changes in the atmosphere characteristics, the increase of telescopes and sensors resolutions and the high sampling rate impose quite strict restrictions to the computational load for computing the Kalman gain.
Motivated by the above considerations, some strategies have been recently considered in the system theory and astronomical communities for the efficient computation of the Kalman gain for large AO systems. Specifically, this paper presents some changes to a recently proposed procedure: the proposed approach, which exploits some results in the control theory of distributed systems, computes an approximation of the optimal gain in the frequency domain exploiting the spatial homogeneity of the system. Then, the control strategy takes advantage of some information on the turbulent phase dynamic, that is estimated from the turbulence measurements. Performances of the proposed method are investigated in some simulations.
[ abstract ] [
url] [
BibTeX]
2012
A. Masiero, A. Cenedese.
A Kalman filter approach for the synchronization of motion capture systems. Proc. of the IEEE Conference on Decision and Control (CDC 2012), 2012
Abstract:
The request for very accurate 3D reconstruction in several applications is leading to the development of very large motion capture systems. A good synchronization of all the cameras in the system is of fundamental importance to guarantee the effectiveness of the 3D reconstruction.
In this work, first, an approximation of the reconstruction error variance taking into account of synchronization errors is derived. Then, a Kalman filter approach is considered to estimate the cameras synchronization errors. The estimated delays can be used to compensate the synchronization error effect on the reconstruction of target positions. The results obtained in some simulations suggest that the proposed strategy allows to obtain a significant reduction of the 3D reconstruction error.
[ abstract ] [
url] [
BibTeX]
Aavv, A. Cenedese.
Amniotic fluid stem cells restore the muscle cell niche in a HSA-Cre, SmnF7/F7 mouse model. Stem Cells, 2012
Abstract:
Mutations in the survival of motor neuron gene (SMN1) are
responsible for spinal muscular atrophy (SMA), a fatal neuromuscular
disorder. Mice carrying a homozygous deletion of Smn exon 7 directed to
skeletal muscle (HSA-Cre, Smn^{F7/F7} mice) present
clinical features of human muscular dystrophies for which new
therapeutic approaches are highly warranted. Herein we demonstrate that
tail vein transplantation of mouse amniotic fluid stem (AFS) cells
enhances the muscle strength and improves the survival rate of the
affected animals. Secondly, after cardiotoxin injury of the Tibialis Anterior,
only AFS-transplanted mice efficiently regenerate. Most importantly,
secondary transplants of satellite cells (SC) derived from treated mice
show that AFS cells integrate into the muscle stem cell compartment, and
have long term muscle regeneration capacity indistinguishable from that
of wild type-derived SC. This is the first study demonstrating the
functional and stable integration of AFS cells into the skeletal muscle,
highlighting their value as cell source for the treatment of muscular
dystrophies.
[ abstract ] [
url] [
pdf] [
BibTeX]
A. Cenedese, P. Bettini.
Assessment of the diagnostics for shape control in fusion machines. Proc. of the IEEE Conference on Decision and Control (CDC 2012), 2012
Abstract:
In fusion devices, the accurate reconstruction of the boundary location and shape from magnetic diagnostics is of paramount importance for the efficient control of the plasma evolution and the safe running of the experiment. In addition to a good and consistent performance in the reconstruction, the task must be performed in real time as the input for the shape controller and more in general for the scenario optimization. To this aim, a statistical procedure for the evaluation of the reconstruction capability of different magnetic sensor sets is presented, which can drive the choice for an optimal set to be used for the reconstruction of plasma location and boundary shape during real time operation. In addition, an algorithm to approximately solve the free boundary problem and estimate the plasma shape starting from the magnetics is devised. Beyond representing a first step towards the definition of a boundary reconstruction code for plasma shape control, this tool is also used to cross validate and confirm the statistical analysis on the diagnostics.
[ abstract ] [
url] [
pdf] [
BibTeX]
F. Zanella, D. Varagnolo, A. Cenedese, G. Pillonetto, L. Schenato.
Asynchronous Newton-Raphson Consensus for Distributed Convex Optimization. 3rd IFAC Workshop on Distributed Estimation and Control in Networked Systems (NecSys'12), 2012
Abstract:
We consider the distributed unconstrained minimization of separable convex costfunctions, where the global cost is given by the sum of several local and private costs, eachassociated to a specific agent of a given communication network. We specifically address anasynchronous distributed optimization technique called Newton-Raphson consensus. Besidehaving low computational complexity, low communication requirements and being interpretableas a distributed Newton-Raphson algorithm, the technique has also the beneficial properties ofrequiring very little coordination and naturally support time-varying topologies. In this workwe analytically prove that under some assumptions it shows local convergence properties, andcorroborate this result by means of numerical simulations.
[ abstract ] [
url] [
pdf] [
BibTeX]
G. Gennari, G. Raccanelli, R. Frezza, A. Cenedese, F. D'Alessi.
EP2160883 - METHOD FOR COORDINATING A PLURALITY OF SENSORS. B1 Patent specification (17.10.2012), 2012 [
url] [
BibTeX]
G. Gennari, G. Raccanelli, R. Frezza, A. Cenedese, F. D'Alessi.
EP2163094 - METHOD AND SYSTEM FOR MONITORING AN ENVIRONMENT. B1 Patent specification (07.11.2012), 2012 [
url] [
BibTeX]
P. Bettini, A. Cenedese.
Iterative Axisymmetric Identification Algorithm (IAIA) for real-time reconstruction of the plasma boundary of ITER. 27th Symposium on Fusion Technology (SOFT2012), 2012
Abstract:
A new boundary reconstruction procedure is presented and validated against ITER nominal equilibria. An approxima- tion of the plasma with an equivalent filamentary current model is employed, which is computed iteratively and allows to describe a wide variety of plasma current distributions (from the peaked ones, to the pedestal current ones). One of the specific features of the procedure is how the filaments are switched on and how the total current is distributed over the entire set, being the filaments independently considered: this allows more degrees of freedom to the model to adapt to particular current distributions, yielding better performances with a negligible additional computational burden. The code also implements a special points search making it well suited for both diverted (be they top or bottom x-point) and limiter configurations. In addition also the reconstruction in presence of noise has been explored.
[ abstract ] [
pdf] [
BibTeX]
P. Bettini, A. Cenedese.
Iterative Axisymmetric Identification Algorithm (IAIA) for real-time reconstruction of the plasma boundary of ITER. Fusion Engineering and Design, vol. Published online2012
Abstract:
A new boundary reconstruction procedure is presented and validated
against ITER nominal equilibria. An approximation of the plasma with an
equivalent filamentary current model is employed, which is computed
iteratively and allows to describe a wide variety of plasma current
distributions (from the peaked ones, to the pedestal current ones). One
of the specific features of the procedure is how the filaments are
switched on and how the total current is distributed over the entire
set, being the filaments independently considered: this allows more
degrees of freedom to the model to adapt to particular current
distributions, yielding better performances with a negligible additional
computational burden. The code also implements a special points search
making it well suited for both diverted (be they top or bottom x-point)
and limiter configurations. In addition also the reconstruction in
presence of noise has been explored.
[ abstract ] [
url] [
BibTeX]
R. Alberton, R. Carli, A. Cenedese, L. Schenato.
Multi-agent perimeter patrolling subject to mobility constraints. Proceedings of American Control Conference ACC2012, 2012
Abstract:
In this paper we study the problem of real-time optimal distributed
partitioning for perimeter patrolling in the context of multi-camera
networks for surveillance. The objective is to partition a given segment
into non-overlapping sub-segments, each assigned to a different camera
to patrol. Each camera has both physical mobility range and limited
speed, and it must patrol its assigned sub-segment by sweeping it back
and forth at maximum speed. Here we first review the solution for the
centralized optimal partitioning. Then we propose two different
distributed control strategies to determine the extremes of the optimal
patrolling areas of each camera. Both these strategies require only
local communication with the neighboring cameras but adopt different
communication schemes, respectively, symmetric gossip and asynchronous
asymmetric broadcast. The first scheme is shown to be provably
convergent to the optimal solution. Some theoretical insights are
provided also for the second scheme whose effectiveness is validated
through numerical simulations.
[ abstract ] [
url] [
pdf] [
BibTeX]
F. Zanella, A. Cenedese.
Multi-agent tracking in wireless sensor networks: implementation. 1st WSEAS International Conference on Information Technology and Computer Networks (ITCN12), pp. 180--185, 2012
Abstract:
In this work the design and implementation of an application to track multiple agents in a indoor Wireless Sensor Actor Network (WSAN) is proposed. The adopted embedded hardware for the network nodes is theTmote Sky, an ultra low power IEEE 802.15.4 compliant wireless device, which has become a reference in the academia for the early development of algorithms and applications for Wireless Sensor Actor Networks (WSANs). These devices are based on the TinyOS operative system and are programmed in NesC a C-derived language specifically developed for embedded systems. NesC has become indispensable for low-level management ofindividual agents while Java was chosen to provide the user with a simple and intuitive graphical interface with whom showing and coordinating the tracking.
[ abstract ] [
url] [
BibTeX]
F. Zanella, A. Cenedese.
Multi-agent tracking in wireless sensor networks: model and algorithm. 1st WSEAS International Conference on Information Technology and Computer Networks (ITCN12), pp. 174--179, 2012
Abstract:
In this work an algorithm to track multiple agents in an indoor Wireless Sensor Actor Network (WSAN) is proposed. The algorithm falls into the category of the radio frequency localization methods, since it exploits the strength of the wireless communications among nodes to establish the position of a set of mobile nodes within a network of fixed nodes placed in known locations. In this sense, a radio channel model is introduced that allows to estimate the distances among nodes to attain localization and tracking (range-based approach). Moreover, to compensate for the scant robustness of power measurements, the loss effects induced by wireless communication,the intrinsic uncertainty of unstructured environments, the algorithm resorts to an Extended Kalman Filter to process the node measurements and reach a desired level of localization performance. Finally, the design phase is validated through the implementation and the experiments on a real testbed.
[ abstract ] [
url] [
BibTeX]
F. Zanella, D. Varagnolo, A. Cenedese, G. Pillonetto, L. Schenato.
Multidimensional Newton-Raphson consensus for distributed convex optimization. 2012 American Control Conference, 2012
Abstract:
In this work we consider a multidimensional distributed optimization technique that is suitable for multiagents systems subject to limited communication connectivity. In particular, we consider a convex unconstrained additive problem, i.e. a case where the global convex unconstrained multidimensional cost function is given by the sum of local cost functions available only to the specific owning agents. We show how, by exploiting the separation of time-scales principle,the multidimensional consensus-based strategy approximates a Newton-Raphson descent algorithm. We propose two alternative optimization strategies corresponding to approximations of the main procedure. These approximations introduce tradeoffs between the required communication bandwidth and the convergence speed/accuracy of the results. We provide analytical proofs of convergence and numerical simulations supporting the intuitions developed through the paper.
[ abstract ] [
url] [
pdf] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Nonstationary turbulence simulation with an efficient multiscale approach. Proc. of the IEEE Multi-Conference on Systems and Control (MSC12), 2012
Abstract:
This paper considers the problem of simulating the turbulence effect on ground telescope observations. The approach presented here is an evolution of a recently proposed approach [3]. The main contributions with respect to [3] are: First, the Haar transform at the basis of the multiscale model in [3] is shown to be equivalent to a local PCA representation. This equivalence allows to reduce the computational complexity of the simulation algorithm by neglecting the components in the signal with lower energy. Furthermore, the simulation of nonstationary turbulence is obtained by properly changing the values of the multiscale model: Such change is eased by the invariance of the PCA spatial basis with respect to the change of turbulence statistical characteristics. The proposed approach is validated by means of some simulations.
[ abstract ] [
url] [
BibTeX]
A. Masiero, A. Cenedese.
On triangulation algorithms in large scale camera network systems. American Control Conference (ACC2012), pp. 4096–-4101, 2012
Abstract:
Geometric triangulation is at the basis of the estimation of the 3D position of a target from a set of camera measurements. The problem of optimal estimation (minimizing the L2 norm) of the target position from multi-view perspective projective measurements is typically a hard problem to solve. In literature there are different types of algorithms for this purpose, based for example on the exhaustive check of all the local minima of a proper eigenvalue problem [2], or branch- and-bound techniques [3]. However, such methods typically become unfeasible for real time applications when the number of cameras and targets become large, calling for the definition of approximate procedures to solve the reconstruction problem.
In the first part of this paper, linear (fast) algorithms, computing an approximate solution to such problems, are described and compared in simulation. Then, in the second part, a Gaussian approximation to the measurement error is used to express the reconstruction error’s standard deviation as a function of the position of the reconstructed point. An upper bound, valid over all the target domain, to this expression is obtained for a case of interest. Such upper bound allows to compute a number of cameras sufficient to obtain a user defined level of position estimation accuracy.
[ abstract ] [
pdf] [
BibTeX]
F. Zanella, D. Varagnolo, A. Cenedese, G. Pillonetto, L. Schenato.
The convergence rate of Newton-Raphson consensus optimization for quadratic cost functions. IEEE Conference on Decision and Control (CDC 2012), 2012
Abstract:
We consider the convergence rates of two peculiar2 convex optimization strategies in the context of multi agent3 systems, namely the Newton-Raphson consensus optimization4 and a distributed Gradient-Descent opportunely derived from5 the first. To allow analytical derivations, the convergence6 analyses are performed under the simplificative assumption of7 quadratic local cost functions. In this framework we derive8 sufficient conditions which guarantee the convergence of the9 algorithms. From these conditions we then obtain closed form10 expressions that can be used to tune the parameters for11 maximizing the rate of convergence. Despite these formulae12 have been derived under quadratic local cost functions13 assumptions, they can be used as rules-of-thumb for tuning14 the parameters of the algorithms in general situations.
[ abstract ] [
url] [
pdf] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
Turbulence Modeling and Estimation for AO systems. Proc. of the SPIE Conference on Astronomical Telescopes and Instrumentation, 2012
Abstract:
Nowadays, the adaptive optics (AO) system is of fundamental importance to reduce the effect of atmospheric turbulence on the images formed on large ground telescopes. In this paper the AO system takes advantage of the knowledge of the current turbulence characteristics, that are estimated by data, to properly control the deformable mirrors. The turbulence model considered in this paper is based on two assumptions: considering the turbulence as formed by a discrete set of layers moving over the telescope lens, and each layer is modeled as a Markov-Random-Field. The proposed Markov-Random-Field approach is exploited for estimating the layers’ characteristics. Then, a linear predictor of the turbulent phase, based on the computed information on the turbulence layers, is constructed. Since scalability and low computational complexity of the control algorithms are important requirements for real AO systems, the computational complexity properties of the proposed model are investigated. Interestingly, the proposed model shows a good scalability and an almost linear computational complexity thanks to its block diagonal structure. Performances of the proposed method are investigated by means of some simulations.
[ abstract ] [
url] [
BibTeX]
2011
A. Beghi, A. Cenedese, A. Masiero.
A multiscale stochastic approach for phase screens synthesis. APPLIED OPTICS, vol. 50pp. 4124--4133, 2011
Abstract:
Simulating
the turbulence effect on ground telescope observations is of
fundamental importance for the design and test of suitable control
algorithms for adaptive optics systems. In this paper we propose a
multiscale approach for efficiently synthesizing turbulent phases at
very high resolution. First, the turbulence is simulated at low
resolution, taking advantage of a previously developed method for
generating phase screens. Then, high-resolution phase screens are
obtained as the output of a multiscale linear stochastic system. The
multiscale approach significantly improves the computational efficiency
of turbulence simulation with respect to recently developed methods.
Furthermore, the proposed procedure ensures good accuracy in reproducing
the statistical characteristics of the turbulent phase.
[ abstract ] [
url] [
BibTeX]
A. Beghi, A. Cenedese, A. Masiero.
A multiscale stochastic approach for phase screens synthesis. Proceedings of the 2011 American Control Conference ACC 2011, pp. 3084--3089, 2011
Abstract:
Simulating the turbulence effect on ground tele-
scope observations is of fundamental importance for the design
and test of suitable control algorithms for adaptive optics
systems. In this paper we propose a multiscale approach for
efficiently synthesizing turbulent phases at very high reso-
lutions: First, the turbulence is simulated at low resolution
taking advantage of a previously developed method for gen-
erating phase screens, [2]. Then, high resolution phase screens
are obtained as the output of a multiscale linear stochastic
system. The multiscale approach significantly improves the
computational efficiency of turbulence simulation with respect
to recently developed methods [1],[2],[8]. Furthermore, the
proposed procedure ensures good accuracy in reproducing the
statistical characteristics of the turbulent phase.
[ abstract ] [
BibTeX]
R. Antonello, A. Cenedese, R. Oboe.
Active damping applied to HSM-driven mechanical loads with elasticity. Proceedings of the 18th IFAC World Congress, 2011
Abstract:
Hybrid Stepper Motors (HSM), together with the microstepping driving technique,
are widely used in many motion control applications, given their low cost and high reliability.
On the other hand, being controlled in an open loop fashion, they cannot achieve high levels
of performance, this mainly due to the absence of a load-side position sensor. In this paper,
we address the problem of controlling the motion of a mechanical load, driven by a HSM,
in presence of a flexible mechanical transmission between motor and load. This is a typical
industrial scenario, in which the problem of the oscillations arising from the excitation of the
mechanical resonance by various disturbances (including torque ripple) is usually addressed by
severely limiting the overall dynamic performance. In this paper, we propose the use of an
active damping strategy, which allows for the improvement of the dynamic response and an
excellent rejection of the oscillations caused by the torque ripple. The proposed technique does
not require the re-design of the existing equipments, since it is based on an enhancement of the
standard microstepping, in which the angle of the stator flux is properly modulated, to produce
a compensating torque and, in turn, damp the oscillatory modes. Such modulation is based
on the proper processing of the measurements obtained from a load-side MEMS accelerometer,
which can be easily fitted into existing setups. Experimental results confirm the effectiveness of
the proposed solution.
[ abstract ] [
url] [
pdf] [
BibTeX]
R. Carli, A. Cenedese, L. Schenato.
Distributed Partitioning Strategies for Perimeter patrolling. Proceedings of the American Control Conference (ACC11), 2011
Abstract:
In this work we study the problem of real-time
optimal distributed partitioning for perimeter patrolling in the
context of multi-camera networks for surveillance. The objec-
tive is to partition a line of fixed length into non-overlapping
segments, each assigned to a different camera to patrol. Each
camera has both physical mobility range and limited speed,
and it must patrol its assigned segment by sweeping it back
and forth at maximum speed. Here we propose three different
distributed control strategies to determine the extremes of the
patrolling areas of each camera. All these strategies require only
local communication with the neighboring cameras but adopt
different communication schemes: synchronous, asynchronous
symmetric gossip and asynchronous asymmetric gossip. For the
first two schemes we provide theoretical convergence guaran-
tees, while for the last scheme we provide numerical simulations
showing the effectiveness of the proposed solution.
[ abstract ] [
pdf] [
BibTeX]
F. Zanella, D. Varagnolo, A. Cenedese, G. Pillonetto, L. Schenato.
Newton-Raphson consensus for distributed convex optimization. IEEE Conference on Decision and Control (CDC 2011), 2011
Abstract:
In this work 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 time-scales 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.
[ abstract ] [
pdf] [
BibTeX]
Aavv, A. Cenedese.
Overview of JET results. Nuclear Fusion, vol. 51(9), 2011
Abstract:
Since the last IAEA Conference JET has been in operation for one year
with a programmatic focus on the qualification of ITER operating
scenarios, the consolidation of ITER design choices and preparation for
plasma operation with the ITER-like wall presently being installed in
JET. Good progress has been achieved, including stationary ELMy H-mode
operation at 4.5?MA. The high confinement hybrid scenario has been
extended to high triangularity, lower ?^{*} and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ?^{*} and ?^{*}
and optimized to simultaneously achieve, under stationary conditions,
ITER-like values of all other relevant normalized parameters. A
dedicated helium campaign has allowed key aspects of plasma control and
H-mode operation for the ITER non-activated phase to be evaluated.
Effective sawtooth control by fast ions has been demonstrated with ^{3}He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q_{95}
values. Complete ELM suppression has, however, not been observed, even
with an edge Chirikov parameter larger than 1. Pellet ELM pacing has
been demonstrated and the minimum pellet size needed to trigger an ELM
has been estimated. For both natural and mitigated ELMs a broadening of
the divertor ELM-wetted area with increasing ELM size has been found. In
disruption studies with massive gas injection up to 50% of the thermal
energy could be radiated before, and 20% during, the thermal quench.
Halo currents could be reduced by 60% and, using argon/deuterium and
neon/deuterium gas mixtures, runaway electron generation could be
avoided. Most objectives of the ITER-like ICRH antenna have been
demonstrated; matching with closely packed straps, ELM resilience,
scattering matrix arc detection and operation at high power density
(6.2?MW?m^{?2}) and antenna strap voltages (42?kV). Coupling measurements are in very good agreement with TOPICA modelling.
[ abstract ] [
url] [
BibTeX]
S. Bittanti, A. Cenedese, S. Zampieri.
Preprints of the 18th IFAC World Congress. 2011 [
BibTeX]
M. Munaro, A. Cenedese.
Scene specific people detection by simple human interaction. Proceedings of the HICV Workshop in the ICCV 2011, 2011
Abstract:
This paper proposes a generic procedure for training a
scene specific people detector by exploiting simple human
interaction. This technique works for any kind of scene im-
aged by a static camera and allows to considerably increase
the performances of an appearance-based people detector.
The user is requested to validate the results of a basic detec-
tor relying on background subtraction and proportions con-
straints. From this simple supervision it is possible to select
new scene specific examples that can be used for retraining
the people detector used in the testing phase. These new ex-
amples have the benefit of adapting the classifier to the par-
ticular scene imaged by the camera, improving the detec-
tion for that particular viewpoint, background, and image
resolution. At the same time, positions and scales, where
people can be found, are learnt, thus allowing to consider-
ably reduce the number of windows that have to be scanned
in the detection phase. Experimental results are presented
on three different scenarios, showing an improved detection
accuracy and a reduced number of false positives even when
the ground plane assumption does not hold.
[ abstract ] [
pdf] [
BibTeX]
R. Antonello, A. Cenedese, R. Oboe.
Torque Ripple Minimization in Hybrid Stepper Motors Using Acceleration Measurements. Proceedings of the 18th IFAC World Congress, 2011
Abstract:
Hybrid stepper motors (HSMs) are commonly used in many cost-sensitive industrial
and consumer applications. With the use of micro-stepping techniques, they could theoretically
achieve a very high resolution in positioning of mechanical loads, even without position sensors.
However, it is well known that HSMs are affected by a large torque ripple, due to cogging and
phase unbalancing. This, in turn, may cause large vibrations on the load, especially in those
systems with flexible elements (e.g. transmission belts). Several solutions have been proposed
to alleviate this problem, but most of them make use of a load-side position sensor, by means of
which it is possible to determine a position-dependent torque ripple profile, to be compensated
during operations. Introducing a high resolution sensor on the load side, however, makes the
cost of the system higher, thus vanishing the advantage of having a low cost open-loop actuator.
Additionally, it is not always possible to accommodate a new position sensor on an existing
mechanical system. In this paper, we propose a new system to compensate for the first two
harmonics of the torque ripple in HSMs, based on the use of a load-side MEMS accelerometer,
which can be easily fitted into existing systems, without any major modifications. The automated
procedure developed minimizes the torque ripple by acting on the offset and amplitude of the
phase currents. Experimental results on systems with and without load elasticity are reported,
proving the effectiveness of the proposed approach.
[ abstract ] [
url] [
pdf] [
BibTeX]
R. Antonello, A. Cenedese, R. Oboe.
Use of MEMS Gyroscopes in Active Vibration Damping for HSM-driven Positioning Systems. IECON 2011 - 37th Conf. of the IEEE Industrial Electronics Society, 2011
Abstract:
Hybrid Stepper Motors (HSM) are the workhorses
in many low-end motion control systems, given their low cost and
high reliability. The resolution of the positioning systems using
this type of motors has been increased with the introduction
of the microstepping driving technique, even if, being operated
in open loop, HSM cannot provide the actual control of the
load position. Recently, the authors have proposed an innovative
control scheme [1], based on the use of a load side acceleration
sensor, that implements the active damping of a HSM-driven
mechanical load, in presence of a flexible mechanical transmission
between motor and load. This is a typical industrial scenario, in
which the problem of the oscillations arising from the excitation
of the mechanical resonance by various disturbances (including
torque ripple) is usually addressed by severely limiting the overall
dynamic performance. In this paper, we propose the extension
of the proposed technique, with the use of a MEMS gyroscope
to implement an active damping control strategy, which allows
for the improvement of the dynamic response and an excellent
rejection of the oscillations caused by the torque ripple. The
proposed technique does not require the re-design of the existing
equipments, since it is based on the real time modulation of the
orientation of the stator flux, aimed at producing a compensating
torque and, in turn, damping the oscillatory modes. Experimental
results, obtained with a HSM-driven camera positioning unit,
confirm the effectiveness of the proposed solution.
[ abstract ] [
url] [
pdf] [
BibTeX]