1,720,995 research outputs found
Observability and reachability of grid graphs via reduction and symmetries
No full textIn this paper we investigate the observability and reachability properties of a network system, running a Laplacian based average consensus algorithm, when the communication graph is a grid. More in detail, we characterize the structure of the grid eigenvectors by means of suitable decompositions of the graph. For each eigenvalue, based on its multiplicity and on suitable symmetries of the corresponding eigenvectors, we provide necessary and sufficient conditions to characterize all and only the nodes from which the network system is observable (reachable). We discuss the proposed criteria and show, through suitable examples, how such criteria reduce the complexity of the observability (respectively reachability) analysis of the grid
Aircraft maneuver regulation: a receding horizon backstepping approach
No full textCoordinated flight is a nonholonomic constraint that implies no sideslip of an aircraft. The equations of motion in coordinated flight are kinematically reducible. This property simplifies the maneuver regulation problem because under such assumption it is possible to write a lateral controller for the transverse dynamics independent of velocity. Assuming coordinated flight, the maneuver regulator consists of a model predictive controller based on the kinematic model. Since, in reality the coordinated flight assumption is seldom satisfied, the kinematic control action is back-stepped into dynamics to compute the actuation of the control surfaces. The proposed control law is tested on a multi-body SW model of an aircraft on various maneuvers, including some aggressive ones
Distributed Minimum Time Servicing for a Team of Dubins Vehicles
No full textIn this paper we study the following problem for a team of Dubins vehicles, i.e. nonholonomic vehicles moving at constant longitudinal speed along planar paths with bounded curvature. Given the initial configurations of the vehicles, find the point in the plane that minimizes the time to be reached by all vehicles. We call it "minimum-time servicing problem". We show that this problem can be approximated by an abstract linear program, namely a generalized version of linear programming, that can be solved in a distributed way over a network. We provide a control and communication law for a wireless network of Dubins vehicles to compute and reach the "minimum-time servicing point" while maintaining the network connected
Network abstract linear programming with application to minimum-time formation control
Full text linkWe identify a novel class of distributed optimization problems, namely a networked version of abstract linear programming. For such problems we propose distributed algorithms for networks with various connectivity and/or memory constraints. Finally, we show how various minimum-time formation control problems can be tackled through appropriate geometric examples of abstract linear programs
Distributed consensus on enclosing shapes and minimum time rendezvous
No full textIn this paper we introduce the notion of optimization under control and communication constraint in a robotic network. Starting from a general setup, we focus our attention on the problem of achieving rendezvous in minimum time for a network of first order agents with bounded inputs and limited range communication. We propose two dynamic control and communication laws. These laws are based on consensus algorithms for distributed computation of the minimal enclosing ball and orthotope of a set of points. We prove that these control laws converge to the optimal solution of the centralized problem (i.e., when no communication constrains are enforced) as the bound on the control input goes to zero. Moreover, we give a bound for the time complexity of one of the two laws
Modeling and dynamic exploration of a tilt-rotor VTOL aircraft
No full textIn this paper we introduce and study a novel model of a Tilt-Rotor VTOL aircraft. The aircraft is structured as a blended wing body equipped with a tilting rotor (the propulsion unit) that gives the vehicle the capability of vertical take off and transition to a forward flight configuration. This model captures the main features of novel tilt-rotor aircraft architectures with more challenging control and maneuvering capabilities. We introduce a complex nine degrees of freedom model of the aircraft to explore the dynamics and the maneuvering capabilities of the vehicle. We perform an analysis of the equilibrium manifold of the aircraft (namely a parametrized family of trimming trajectories) and, as main contribution of the paper, we introduce a set of optimal control based strategies to explore the trajectory manifold of the vehicle in order to generate non-stationary and highly aggressive trajectories. In particular, we provide numerical computations showing how to generate a trajectory for transitions from near hover to forward flight
On the curvature of the trajectory manifold of nonlinear systems
No full textThis paper represents a preliminary contribution in the direction of characterizing geometric properties of the trajectory manifold of nonlinear systems. We introduce the notion of curvature of the trajectory manifold and define it by means of a nonlinear quadratic optimal control problem. The quadratic cost can be viewed as a weighted norm induced by a suitable inner product that provides a notion of orthogonality. The curvature at a given trajectory is defined in terms of the curves orthogonal to the tangent space at the given trajectory. We characterize the set of orthogonal curves. We show that it is a topological complement of the tangent space. We provide numerical techniques to compute orthogonal curves and to compute a lower bound of the curvature. We test these techniques on the inverted pendulum example
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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