20XX
M. Fabris, G. Michieletto, A. Cenedese.
A Proximal Point Approach for Distributed System State Estimation. IFAC World Congress (IFAC2020) - [accepted], 20XX
Abstract:
System state estimation constitutes a key problem in several applications involving
multi-agent system architectures. This rests upon the estimation of the state of each agent in
the group, which is supposed to access only relative measurements w.r.t. some neighbors state.
Exploiting the standard least-squares paradigm, the system state estimation task is faced in this
work by deriving a distributed Proximal Point-based iterative scheme. This solution entails the
emergence of interesting connections between the structural properties of the stochastic matrices
describing the system dynamics and the convergence behavior toward the optimal estimate. A
deep analysis of such relations is provided, jointly with a further discussion on the penalty
parameter that characterizes the Proximal Point approach.
[ abstract ] [
BibTeX]
G. Michieletto, N. Lissandrini, A. Antonello, R. Antonello, A. Cenedese.
Dual Quaternion Delay Compensating Maneuver Regulation for Fully Actuated UAVs. IFAC World Congress (IFAC2020) - [accepted], 20XX
Abstract:
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. In addition, the dual-quaternion
formalism is adopted to model the dynamics of the aerial
platforms allowing feedback linearize the whole system,
including both position and attitude, with a single
controller. The tests conducted in Gazebo physic simulator
show that the proposed controller outperforms the popular
trajectory tracking PID regulators.
[ abstract ] [
BibTeX]
G. Michieletto, A. Cenedese, D. Zelazo.
[Undisclosed]. IEEE Transactions on Control of Network Systems [provisionally accepted], 20XX [
BibTeX]
G. Michieletto, A. Cenedese, A. Et.
[Undisclosed]. IEEE Transactions of Automation Science and Engineering [submitted], 20XX [
BibTeX]
2020
G. Michieletto, A. Cenedese, L. Zaccarian, A. Franchi.
Hierarchical non-linear control for multi-rotor asymptotic stabilization based on zero-moment direction. Automatica, vol. 1172020
Abstract:
We consider the hovering control problem for a class of multi-rotor aerial platforms with generically oriented propellers. Given
the intrinsically coupled translational and rotational dynamics of such vehicles, we first discuss some assumptions for the
considered systems to reject moment disturbances and to balance the gravity force, which are translated into a geometric
characterization of the platforms that is usually fulfilled by both standard models and more general configurations. Hence,
we propose a control strategy based on the identification of a zero-moment direction for the applied force and the dynamic
state feedback linearization around this preferential direction, which allows to asymptotically stabilize the platform to a static
hovering condition. Stability and convergence properties of the control law are rigorously proved through Lyapunov-based
methods and reduction theorems for the stability of nested sets. Asymptotic zeroing of the error dynamics and convergence to
the static hovering condition are then confirmed by simulation results on a star-shaped hexarotor model with tilted propellers.
[ abstract ] [
url] [
BibTeX]
2019
N. Lissandrini, G. Michieletto, R. Antonello, M. Galvan, A. Franco, A. Cenedese.
Cooperative Optimization of UAVs Formation Visual Tracking. Robotics, vol. 8(3), pp. 1--22 (Article Number 52), 2019
Abstract:
The use of unmanned vehicles to perform tiring, hazardous, repetitive tasks, is becoming a reality out of the academy laboratories, getting more and more interest for several application fields from the industrial, to the civil, to the military contexts. In particular, these technologies appear quite promising when they employ several low-cost resource-constrained vehicles leveraging their coordination to perform complex tasks with efficiency, flexibility, and adaptation that are superior to those of a single agent (even if more instrumented). In this work, we study one of said applications, namely the visual tracking of an evader (target) by means of a fleet of autonomous aerial vehicles, with the specific aim of focusing on the target so as to perform an accurate position estimation while concurrently allowing a wide coverage over the monitored area so as to limit the probability of losing the target itself. These clearly conflicting objectives call for an optimization approach that is here developed: by considering both aforementioned aspects and the cooperative capabilities of the fleet, the designed algorithm allows controling in real time the single fields of view so as to counteract evasion maneuvers and maximize an overall performance index. The proposed strategy is discussed and finally assessed through the realistic Gazebo-ROS simulation framework.
[ abstract ] [
url] [
BibTeX]
L. Varotto, M. Fabris, G. Michieletto, A. Cenedese.
Distributed Dual Quaternion Based Localization of Visual Sensor Networks. European Control Conference (ECC 2019), 2019
Abstract:
In this paper we consider the localization problem for a visual sensor network. Inspired by the alternate attitude and position distributed optimization framework discussed in [1], we propose an estimation scheme that exploits the unit dual quaternion algebra to describe the sensors pose. This representation is beneficial in the formulation of the optimization scheme allowing to solve the localization problem without designing two interlaced position and orientation estimators, thus improving the estimation error distribution over the two pose components and the overall localization performance. Furthermore, the numerical experimentation asserts the robustness of the proposed algorithm w.r.t. the initial conditions.
[ abstract ] [
url] [
BibTeX]
G. Michieletto, A. Cenedese, A. Franchi.
Force-Moment Decoupling and Rotor-Failure Robustness for Star-Shaped Generically-Tilted Multi-Rotors. IEEE Conference on Decision and Control (CDC2019), pp. 2132--2137, 2019
Abstract:
Aerial robotics is increasingly becoming an attractive field of research thanks to the peculiar mixture of theoretical issues to be solved and technological challenges to be faced. In particular, recent developments have seen the multiplication of multi-rotor platforms that aim at improving the maneuverability of classical quadrotors in standard and harsh flying conditions, thus opening the field to comprehensive studies over the structural multi-rotor properties of actuation, decoupling, and robustness, which strongly depend on the mechanical configuration of the systems. This work collocates along this line of research by considering star-shaped generically-tilted multi-rotors (SGTMs), namely platforms with more than four possibly tilted propellers (along two tilting orthogonal axes). For these platforms, we investigate how the structural choices over the number of propellers and the tilting angles affect the force-moment decoupling features and, by recalling the robustness definition that refers to the hovering capabilities of the platform, we provide a robustness analysis and an hoverability assessment for SGTMs having five to eight actuators against the loss of one and two propellers.
[ abstract ] [
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BibTeX]
G. Michieletto, A. Cenedese.
Formation Control for Fully Actuated Systems: a Quaternion-based Bearing Rigidity Approach. European Control Conference (ECC 2019), 2019
Abstract:
This work deals with formations of mobile agents with six independently controllable degrees of freedom able to retrieve relative bearing measurements w.r.t. some neighbors in the group. Exploiting the bearing rigidity framework, two control objectives are here addressed: ( i) the stabilization of these fully actuated multi-agent systems towards desired configurations, and (i i) their coordinated motion along directions guaranteeing the system shape maintenance. The proposed approach relies on a new formulation of the bearing rigidity theory based on the adoption of the unit quaternion formalism to describe the agents attitude. Through this representation choice, the formation dynamics is linear w.r.t. the input control velocities and the rigidity theory suggests the design of a distributed control scheme for both control goals whose efficacy is confirmed by numerical simulations.
[ abstract ] [
url] [
BibTeX]
M. Fabris, G. Michieletto, A. Cenedese.
On the Distributed Estimation from Relative Measurements: a Graph-Based Convergence Analysis. European Control Conference (ECC 2019), 2019
Abstract:
The state estimation of a multi-agent system
resting upon noisy measurements constitutes a problem re-
lated to several applicative scenarios, such as, for example,
robotic localization and navigation, resource balancing and task
allocation, cooperative manipulation and coordinated control.
Adopting the standard least-squares approach, in this work
we derive both the (centralized) analytic solution to this issue
and two distributed iterative schemes, which allow to establish
a connection between the convergence behavior of consensus
algorithm towards the optimal estimate and the theory of the
stochastic matrices that describe the network system dynamics.
This study on the one hand highlights the role of the topological
links that define the neighborhood of agent nodes, while on the
other allows to optimize the convergence rate by easy parameter
tuning. The theoretical findings are validated considering dif-
ferent network topologies by means of numerical simulations.
[ abstract ] [
url] [
BibTeX]
A. Franchi, P. Robuffo Giordano, G. Michieletto.
Online Leader Selection for Collective Tracking and Formation Control: the Second Order Case. IEEE Transactions on Control of Network Systems, pp. 1-1, 2019
Abstract:
In this work, we deal with a double control task for a group of interacting agents having a second-order dynamics. Adopting the leader-follower paradigm, the given multi-agent system is required to maintain a desired formation and to collectively track of a velocity reference provided by an external source to a single agent. We prove that it is possible to optimize the group performance by persistently selecting online the leader among the agents. To do this, we first define a suitable error metric able to capture the tracking performance of the multi- agent group while maintaining a desired formation through a (even time-varying) communication-graph topology. Then we show that this depends on the algebraic connectivity and on the maximum eigenvalue of the Laplacian matrix of a special directed graph induced by the identity of the chosen leader. By exploiting these theoretical results, we finally design a fully- distributed adaptive procedure able to periodically select online the optimum leader among the neighbors of the current one. The effectiveness of the proposed solution against other possible strategies is confirmed by numerical simulations.
[ abstract ] [
BibTeX]
2018
A. Antonello, G. Michieletto, R. Antonello, A. Cenedese.
A Dual Quaternion Feedback Linearized Approach for Maneuver Regulation of Rigid Bodies. IEEE Control Systems Letters, vol. 2(3), pp. 327 -- 332, 2018
Abstract:
The adoption of the dual quaternion formalism to represent the pose (position and orientation) of a rigid body allows to design a single controller to regulate both its position and its attitude. In this work, we adopt such a pose representation to develop an exponentially stable maneuver regulation control law, ensuring robust path following in the presence of disturbances. The designed solution relies on the feedback linearized model of the dual quaternion based dynamics of the rigid body. Numerical results confirm the effectiveness of the proposed maneuver regulation approach when compared with trajectory tracking in a noisy scenario.
[ abstract ] [
url] [
BibTeX]
G. Michieletto, M. Ryll, A. Franchi.
Fundamental actuation properties of multirotors: Force–moment decoupling and fail–safe robustness. IEEE Transactions on Robotics, vol. 34(3), pp. 702--715, 2018
Abstract:
In this paper, we shed light on two fundamental actuation capabilities of multirotors. The first is the degree of coupling between the total force and total moment generated by the propellers. The second is the ability to robustly fly completely still in place after the loss of one or more propellers, in the case of mono-directional propellers. These are formalized through the definition of some algebraic conditions on the control allocation matrices. The theory is valid for any multirotor, with arbitrary number, position, and orientation of the propellers. As a show case for the general theory, we demonstrate that standard star-shaped hexarotors with collinear propellers are not able to robustly fly completely still at a constant spot using only five of their six propellers. To deeply understand this counterintuitive result, it is enough to apply our theory, which clarifies the role of the tilt angles and locations of the propellers. The theory is also able to explain why, on the contrary, both the tilted star-shaped and the Y-shaped hexarotors can fly with only five out of six propellers. The analysis is validated with both simulations and extensive experimental results showing recovery control after rotor losses.
[ abstract ] [
url] [
BibTeX]
G. Michieletto, S. Milani, A. Cenedese, G. Baggio.
Improving Consensus-based Distributed Camera Calibration via Edge Pruning and Graph Traversal Initialization. Proceedings of the 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp. 3166--3170, 2018
Abstract:
Over the past few years, a huge number of distributed camera calibration strategies have been proposed for video surveillance and monitoring systems involving mobile terminals. Many of the proposed solutions rely on consensus-based algorithms, which aim at estimating the configuration of the network via a message passing protocol. In this paper we propose an improved consensus-based distributed camera calibration strategy that exploits a robust initialization, together with a pruning protocol to remove faulty links which could propagate excessively-noisy information through the network reducing the convergence time. The proposed solution seems to improve the state-of-the-art strategies in terms of accuracy, convergence speed, and computational complexity.
[ abstract ] [
url] [
BibTeX]
F. Branz, M. Duzzi, L. Olivieri, F. Sansone, G. Michieletto, R. Antonello, A. Cenedese, A. Francesconi.
Laboratory validation of close navigation, rendezvous and docking technologies for nanosats. Proceedings of the 4S Symposium, 2018
Abstract:
Over the last decades, small satellites have
become very appealing among the space community for their low complexity and
high flexibility. Many proposed mission concepts foresee the employment of
miniature spacecraft for a variety of applications, many of which are
economically unfeasible with traditional vehicles. This is due to the fact that
the development of miniaturized and standardized space vehicles may
considerably reduce the design, manufacturing and lunch costs involved. Furthermore,
the reduced unitary mass of small satellites allows launches of multiple
vehicles equipped with independent functionalities, thus achieving increased
flexibility and redundancy. In the future, one additional opportunity could be
given by the capability to assemble spacecraft in orbit to form reconfigurable
structures. This would further boost the number of possibilities in terms of
applications and operations. Nevertheless, the novelty of such concept and the
intrinsic complexity of its practical realization still require a considerable
research effort. In fact, only few navigation and docking technologies for nano- and micro satellites
have been designed and proved in relevant environment. In this framework, the
authors focus on the development and validation of critical technologies for
close navigation, rendezvous and docking suitable for nanosatellites.
This
paper presents a laboratory experiment for the validation on a complete rendezvous,
navigation and docking package compatible with the common CubeSat standard. The
experiment is conducted on a low friction table, with one free moving vehicle
(chaser) that approaches and docks to a fixed target interface. The test
facility allows three degrees of freedom to the nanosat mock-up. The vehicle is
equipped with an autonomous package that features (1) a camera-based vision
system for relative navigation, (2) a set of independent electro-magnetic coils
for final alignment and soft docking, (3) a single-actuator hard docking system
for structural connection between the chaser and the target, (4) a dedicated
electronics package for motion control and system status monitoring. The mobile
platform is also equipped with a set of flat air bearing with a dedicated
high-pressure pneumatic circuit for frictionless in-plane motion.
This paper
describes the docking package, the CubeSat mock-up and the test facility in
details, with reference to the main design considerations. Numerical
simulations have been conducted to foresee the dynamical behaviour of the
system and to select the appropriate control algorithm. An intensive
experimental campaign aims at the validation of numerical results and at the
functional verification and performance estimation for each subsystem and for
the system as a whole. The numerical and experimental results are presented and
compared, allowing to draw useful conclusions for the future development steps.
[ abstract ] [
BibTeX]
A. Antonello, G. Michieletto, R. Antonello, A. Cenedese.
Maneuver Regulation vs. Trajectory Tracking for Fully Actuated UAVs: A Dual Quaternion Approach. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS2018), pp. poster 02/10 #13, 2018
Abstract:
Maneuver regulation emerges as an optimal strategy to perform robust path following in presence of disturbances, exploiting vehicle controllability and improving performances w.r.t. trajectory tracking. In this work we consider
maneuver regulation for a fully-actuated aerial platform in a
dual quaternion framework, which yields the additional benefit
of addressing the attitude and position control problem with
a single state controller. To this aim, the nonlinear dynamics
is first derived in a dual quaternion setup and then feedback
linearized to enable the design of a stable maneuver regulator.
This controller is compared with a standard PD scheme, w.r.t.
the capability of following a desired trajectory, and is then
further improved through the definition of a strategy to compensate for the cumulative delay due to external disturbances.
[ abstract ] [
url] [
BibTeX]
2017
G. Michieletto, M. Ryll, A. Franchi.
Control of statically hoverable multi-rotor aerial vehicles and application to rotor-failure robustness for hexarotors. International Conference on Robotics and Automation (ICRA), pp. 2747--2752, 2017
Abstract:
Standard hexarotors are often mistakenly considered ‘by definition’ fail-safe multi-rotor platforms because of
the two additional propellers when compared to quadrotors.
However this is not true, in fact, a standard hexarotor cannot
statically hover with ‘only’ five propellers. In this paper we
provide a set of new general algebraic conditions to ensure
static hover for any multi-rotor platform with any number
of generically oriented rotors. These are elegantly formulated
as the full-rankness of the control moment input matrix,
and the non-orthogonality between its null-space and the row
space of the control force input matrix. Input saturations and
safety margins are also taken into account with an additional
condition on the null-space of control moment input matrix. A
deep analysis on the hoverability properties is then carried
out focusing on the propeller loss in a hexarotor platform.
Leveraging our general results we explain why a standard
hexarotor is not robust and how it can be made robust thanks
to a particular tilt of the rotors. We finally propose a novel
cascaded controller based on a preferential direction in the
null-space of the control moment input matrix for the large
class of statically hoverable multi-rotors, which goes far beyond
standard platforms, and we apply this controller to the case of
failed tilted hexarotor.
[ abstract ] [
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BibTeX]
A. Cenedese, M. Luvisotto, G. Michieletto.
Distributed Clustering Strategies in Industrial Wireless Sensor Networks. IEEE Transactions on Industrial Informatics, vol. 13(1), pp. 228-237, 2017
Abstract:
Wireless sensor networks (WSNs) can provide numerous benefits in industrial automation. By removing the cable infrastructure, the wireless architecture enables the possibility for nodes in a network to dynamically and autonomously group into clusters according to the communication features and the data they collect. This capability allows to leverage the flexibility and robustness of industrial WSNs in supervisory intelligent systems for high-level tasks, such as, for example, environmental sensing, condition monitoring, and process automation. In this paper, a clustering strategy is studied that partitions a sensor network into a nonfixed number of nonoverlapping clusters according to the communication network topology and measurements distribution: To this aim, both a centralized and a distributed algorithm are designed that do not require a cluster-head structure or other network assumptions. As a validation, these strategies are tested on a real dataset coming from a structured environment and the effectiveness of the clustering procedure is also investigated to perform anomalies detection in an industrial production process.
[ abstract ] [
url] [
pdf] [
BibTeX]
G. Michieletto, A. Cenedese, L. Zaccarian, A. Franchi.
Nonlinear Control of Multi-Rotor Aerial Vehicles Based on the Zero-Moment Direction. IFAC World Congress 2017, pp. 13686--13691, 2017
Abstract:
A quaternion-based nonlinear control strategy is here presented to steer and keep a generic multi-rotor
platform in a given reference position. Exploiting a state feedback structure, the proposed solution
ensures the stabilization of the aerial vehicle so that its linear and angular velocity are zero and its
attitude is constant. The main feature of the designed controller is the identification of a zero-moment
direction in the feasible force space, i.e., a direction along which the control force intensity can be
assigned independently of the control moment. The asymptotic convergence of the error dynamics is
confirmed by simulation results on a hexarotor with tilted propellers.
[ abstract ] [
BibTeX]
2016
G. Michieletto, A. Cenedese, A. Franchi.
Bearing Rigidity Theory in SE(3). 55th Conference on Decision and Control (CDC16), pp. 5950-5955, 2016
Abstract:
Recently, rigidity theory has emerged as an ef-
ficient tool in the control field of coordinated multi–agent
systems, such as multi–robot formations and UAVs swarms
that are characterized by the sensing, communication and
movement capabilities. This paper aim at describing the rigidity
properties for frameworks embedded in SE(3), i.e. the three–
dimensional Euclidean space wherein each agent has 6DoF. In
such configuration, it is assumed that the devices are able to
gather bearing measurements of their neighbors, expressing
them into their own body frame. Rigidity properties are
mathematically formalized in the paper which differs from the
previous works as it faces the extension in three–dimensional
space dealing with the 3D rotations manifold. In particular,
the attention is focused on the infinitesimal SE(3)–rigidity for
which necessary and sufficient condition is provided.
[ abstract ] [
url] [
BibTeX]
G. Belgioioso, A. Cenedese, G. Michieletto.
Distributed partitioning strategies with visual optimization for camera network perimeter patrolling. 55th Conference on Decision and Control (CDC16), pp. 5912-5917, 2016
Abstract:
The employment of smart camera networks for
surveillance purposes has become ubiquitous in many appli-
cation scenarios, from the industrial, to the public, to the
home environments. In particular, in this work the boundary
patrolling problem is considered, where the camera network task
is to monitor the perimeter of an environment so as to detect
anomalies and track possible intrusions. Here, a distributed
solution is sought based on the definition of a suitable functional
that accounts both for the equitable partitioning of the available
space and for the quality of vision of the patrolled area,
and admits a unique optimal solution. The optimization of
such functional leads to the design of an algorithm relying
on a symmetric gossip communication protocol among the
neighboring cameras. The theoretical results formalized in
terms of propositions prove the correctness of the approach
and the numerical simulations on a realistic scenario confirm
the validity of the proposed procedure.
[ abstract ] [
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BibTeX]
2015
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), pp. 3828--3833, 2015
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.
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