luca consolini - Academia.edu (original) (raw)

Papers by luca consolini

Sensors, 2009

In this paper, we present an innovative transmit power control scheme, based on optimization theo... more In this paper, we present an innovative transmit power control scheme, based on optimization theory, for wireless sensor networks (WSNs) which use carrier sense multiple access (CSMA) with collision avoidance (CA) as medium access control (MAC) protocol. In particular, we focus on schemes where several remote nodes send data directly to a common access point (AP). Under the assumption of finite overall network transmit power and low traffic load, we derive the optimal transmit power allocation strategy that minimizes the packet error rate (PER) at the AP. This approach is based on modeling the CSMA/CA MAC protocol through a finite state machine and takes into account the network adjacency matrix, depending on the transmit power distribution and determining the network connectivity. It will be then shown that the transmit power allocation problem reduces to a convex constrained minimization problem. Our results show that, under the assumption of low traffic load, the power allocation strategy, which guarantees minimal delay, requires the maximization of network connectivity, which can be equivalently interpreted as the maximization of the number of non-zero entries of the adjacency matrix. The obtained theoretical results are confirmed by simulations for unslotted Zigbee WSNs.

For a class of Chaplygin-like nonholonomic systems a special motion planning is addressed. Given ... more For a class of Chaplygin-like nonholonomic systems a special motion planning is addressed. Given a path in an n-dimensional space we deduce conditions for which there exist feedforward inputs that cause the system to exactly follow the given path. The posed problem is studied from both local and global viewpoints and a constructive solution is provided by means of a dynamic inversion generator, i.e., a dynamical (inverse) system whose outputs are the sought control inputs. The developed theory may be applied to the maneuver regulation problem to help pursuing aggressive maneuvering of autonomous aerial vehicles. Simulations for 3-dimensional and 2-dimensional path following examples are included.

This paper presents a method for non causal exact dynamic inversion for non minimum phase nonline... more This paper presents a method for non causal exact dynamic inversion for non minimum phase nonlinear systems, which seems alternative to those existing in literature. The method is based on a morphing procedure which allows to find a periodic solution of a desired equation by a continuous deformation of a known periodic solution of a simpler auxiliary system. This method allows to face the tracking problem for a class of systems which are well-known in literature, such as the inverted pendulum,the VTOL aircraft, the motorcycle and the CTOL aircraft.

International Journal of Control, 2003

This paper focuses on a special path following task arising from the needs of vision-based autono... more This paper focuses on a special path following task arising from the needs of vision-based autonomous guidance: a given front point of a car-like vehicle that is within the look-ahead range of a stereo vision system must follow a prespecified Cartesian path. A solution to this path following problem is provided by a new feedforward/feedback control strategy where the feedforward is determined by a dynamic generator based on exact dynamic inversion over the nominal vehicle model and the feedback is mainly issued by correcting terms proportional to the tangential and normal errors determined with respect to the vehicle's ideal trajectory. A convergence analysis of the resulting dynamic inversion based controller is established versus a vehicle's uncertain model defined via equation errors. Simulation examples highlighting the controller's performances are included.

Systems & Control Letters, 2009

A spherical pendulum consists of a mass (the body) linked to a moving mass (the base), to which a... more A spherical pendulum consists of a mass (the body) linked to a moving mass (the base), to which an external force is applied. In recent literature, considerable attention has been given to the spherical pendulum with particular emphasis on the stabilization problem, but there are fewer results related to tracking.

International Journal of Robust and Nonlinear Control, 2009

This paper presents a method for non-causal exact dynamic inversion for a class of non-minimum ph... more This paper presents a method for non-causal exact dynamic inversion for a class of non-minimum phase nonlinear systems, which seems to be an alternative to those existing in the literature. This method is based on a homotopy procedure that allows to find a ‘small’ periodic solution of a desired equation by a continuous deformation of a known periodic solution of a simpler auxiliary system. This method allows to face the exact output tracking problem for some non-minimum phase systems that are well known in the literature, such as the inverted pendulum, the motorcycle and the CTOL aircraft. Copyright © 2008 John Wiley & Sons, Ltd.

Automatica, 2005

This paper deals with a path following problem for a system affected by noise and proposes a dyna... more This paper deals with a path following problem for a system affected by noise and proposes a dynamic inversion-based controller that makes use of the error between the real position and a suitable path location. An estimate of such error is given in terms of the noise bounds, showing the practical stability of the closed loop system. The results presented in this article apply to a subclass of Chaplygin control systems which includes several common mechanical systems. As an example the developed strategy has been applied to maneuver a kinematic model of a system moving in a 3-dimensional space in such a way that a point located at a positive distance from its center of geometry is driven towards a given path.

Automatica, 2010

This article presents a solution to the path following problem for the planar vertical take-off a... more This article presents a solution to the path following problem for the planar vertical take-off and landing aircraft (PVTOL) which is applicable to a class of smooth Jordan curves. Our path following methodology enjoys the two properties of output invariance of the path (i.e., if the PVTOL's centre of mass is initialized on the path and its initial velocity is tangent to the path, then the PVTOL remains on the path at all future time) and boundedness of the roll dynamics. Further, our controller guarantees that, after a finite time, the time average of the roll angle is zero, and the PVTOL does not perform multiple revolutions about its longitudinal axis.

The local path following problem for time-varying nonlinear control affine systems is addressed a... more The local path following problem for time-varying nonlinear control affine systems is addressed and sufficient conditions for its solution are found by transforming it in a constrained nonlinear control problem on a suitable manifold. In case of Chaplygin-type systems, a very simple condition and a dynamic inversion generator of the control are exhibited. The developed theory has been applied to

The paper deals with a general class of leader-follower formations of unicycle robots induced by ... more The paper deals with a general class of leader-follower formations of unicycle robots induced by a constraint function that depends on the position and the orientation of the vehicles. We study the flexibility of such formations by introducing the notion of formation internal dynamics, characterize its equilibria and give sufficient geometric conditions for their existence. In particular, we show that the displacement and the relative orientation of each follower with respect to the leader's reference frame are fixed if and only if the robots either move along circular paths or parallel straight lines. These equilibrium configurations always exist if the trajectory of the leader is a circle of sufficiently small curvature or a straight line.

This article proposes a path following controller that regulates the center of mass of the planar... more This article proposes a path following controller that regulates the center of mass of the planar vertical takeoff and landing aircraft (PVTOL) to the unit circle and makes the aircraft traverse the circle in a desired direction. A static feedback controller is designed using the ideas of transverse feedback linearization, finite time stabilization and virtual constraints. No time parameterization is given to the desired motion on the unit circle. Instead, our approach relies on the nested stabilization of two sets on which the dynamics of the PVTOL exhibit desirable behavior.

In this paper a stabilizing control scheme to steer hierarchical formations of unicycle robots is... more In this paper a stabilizing control scheme to steer hierarchical formations of unicycle robots is proposed. Hierarchical formations are characterized by modular leader-follower units suitably interconnected. Robots linear velocity and trajectory curvature are forced to satisfy some given bounds. An original contribution of the paper is the study of the effect of these bounds on the admissible paths of the robots and the derivation of formulae. A peculiar feature of the proposed control strategy is that the position of the follower in the basic unit is not rigidly fixed with respect to the leader but varies in proper circle arcs centered in the leader reference frame. Simulation experiments illustrate the theory and show the effectiveness of the proposed design.

Siam Journal on Applied Mathematics, 2007

Automatica, 2008

The paper deals with leader-follower formations of nonholonomic mobile robots, introducing a form... more The paper deals with leader-follower formations of nonholonomic mobile robots, introducing a formation control strategy alternative to those existing in the literature. Robots control inputs are forced to satisfy suitable constraints that restrict the set of leader possible paths and admissible positions of the follower with respect to the leader. A peculiar characteristic of the proposed strategy is that the follower position is not rigidly fixed with respect to the leader but varies in proper circle arcs centered in the leader reference frame.

This paper presents a sufficient condition for a manifold Â¿ to be locally controlled invariant a... more This paper presents a sufficient condition for a manifold Â¿ to be locally controlled invariant at x0 Â¿ Â¿ which reduces, in the cases of linear and non linear affine systems, to well known results in the literature: essentially the result says that a manifold Â¿ Â¿ Â¿n is locally controlled at x0 Â¿ Â¿ if first of all we can find a control u0 Â¿ Â¿m such that F(x0, u0) Â¿ Tx0Â¿ (this condition is evidently necessary), second F(x,u) continues to stay in something larger than TxÂ¿ (namely TxÂ¿ + Â¿uF(x, u)(Â¿m)) in a neighborhood of (x0, u0) in Â¿ Ã Â¿m.

Nonlinear Analysis-theory Methods & Applications, 2011

We present a continuation method to obtain a family of T-periodic solutions for a family of T-per... more We present a continuation method to obtain a family of T-periodic solutions for a family of T-periodic systems.In particular, we present some sufficient analytical conditions, which have the advantage of being an easy application to some systems of interest in physics or engineering. We apply these conditions to the exact tracking problem for the inverted spherical pendulum.

IEEE Transactions on Robotics, 2009

The paper proposes a new geometric approach to the stabilization of a hierarchical formation of u... more The paper proposes a new geometric approach to the stabilization of a hierarchical formation of unicycle robots. Hierarchical formations consist of elementary leader-follower units disposed on a rooted tree: each follower sees its relative leader as a fixed point in its own reference frame. Robots' linear velocity and trajectory curvature are forced to satisfy some given bounds. The major contribution of the paper is to study the effect of these bounds on the admissible trajectories of the main leader. In particular, we provide recursive formulas for the maximum velocity and curvature allowed for the main leader, so that the robots can achieve the desired formation while respecting their input constraints. An original formation control law is proposed and the asymptotic stabilization is proved. Simulation experiments illustrate the theory and show the effectiveness of the proposed designs.

IEEE Transactions on Automatic Control, 2007

... In [7], a nonlinear output-feedback controller is used to force the VTOL aircraft to globally... more ... In [7], a nonlinear output-feedback controller is used to force the VTOL aircraft to globally ... In the development of the proof, the problem of finding the right initial state is reformulated as ... internal dynamics given by system (4). The main idea is the following: the VTOL aircraft has an ...

This paper deals with leader-follower formations of nonholonomic mobile robots. Formalizing the p... more This paper deals with leader-follower formations of nonholonomic mobile robots. Formalizing the problem in a geometric framework, it is proposed a controller that is alternative to those existing in the literature. It is shown that the geometry of the formation imposes a bound on the maximum admissible curvature of leader trajectory. A peculiar characteristic of the proposed strategy is that the position of the followers is not fixed with respect to the leader reference frame but varies in suitable cones. The formation geometry adapts to the followers dynamics and this allows lower control effort with respect to other approaches based on rigid formations.

The paper focuses on leader-follower formations of nonholonomic mobile robots. A formation contro... more The paper focuses on leader-follower formations of nonholonomic mobile robots. A formation control alternative to those existing in the literature is introduced. We show that the geometry of the formation imposes a bound on the maximum admissible curvature of leader trajectory. An peculiar feature of the proposed strategy is that the followers position is not rigidly fixed with respect to the leader reference frame but varies in suitable cones centered in the leader reference frame. Our approach also applies to hierarchical multirobot formations described by rooted tree graphs. Simulation experiments confirm the effectiveness of the proposed control schemes.