1,720,996 research outputs found
Multiconsensus control of homogeneous LTI hybrid systems under time-driven jumps
Full text linkIn this paper, we consider a network of homogeneous LTI hybrid dynamics under time-driven aperiodic jumps and exchanging information over a fixed communication graph. Based on the notion of almost equitable partitions, we explicitly characterize the clusters induced by the network over the nodes and, consequently, the corresponding multi-consensus trajectories. Then, we design a decentralized control ensuring convergence of all agents to the corresponding multi-consensus trajectory. Simulations over an academic example illustrate the results
Sampled-Data String Stability for a Platoon of heterogeneous Vehicles via a Mesoscopic Approach
Full text linkThis paper explores sampled-data techniques to achieve asymptotic string stability in a platoon of autonomous vehicles. This is done making use of both microscopic and macroscopic data that are, however, often available at distinct time instants. The proposed mesoscopic controller is demonstrated to operate effectively, regardless of the involved sampling periods. The theoretical findings are validated through simulations
Energy-Balance PBC of nonlinear dynamics under sampling and delays
Full text linkThe paper provides a new class of passivity-based controllers (PBCs) for stabilizing sampled-data input-delayed dynamics at a desired equilibrium via energy-balancing (EB) and reduction. Given a nonlinear dynamics under piecewise constant and retarded input, we first exhibit a new dynamics (the reduced dynamics) that is free of delays and equivalent to the original one. Accordingly, we design the digital controller assigning a suitable energetic behaviour to the reduced delay-free model with a stable target equilibrium. Then, it is proved that such a controller solves the EB-PBC problem on the original retarded system. The results are illustrated over a simple mechanical system
Nonlinear Hamiltonian systems under sampling
Full text linkThis paper investigates the transformation of Hamiltonian structures under sampling. It is shown that the exact sampled-data equivalent model associated to a given port-Hamiltonian continuous-time dynamics exhibits a discrete-time representation in terms of the discrete gradient, with the same energy function but modified damping and interconnection matrices. By construction, the proposed sampled-data dynamics guarantees exact matching of both the state evolutions and the energy-balance at all sampling instants. Its generalization to port-controlled Hamiltonian dynamics leads to characterize a new power conjugate output which recovers the average-passivating output. On these bases, energy-management control strategies are proposed. An energetic interpretation is confirmed by its description in the Dirac formalism. Two classical examples are worked out to validate the proposed sampled-data modeling in a comparative way with the literature
Virtual Holonomic Constraints for Euler-Lagrange systems under sampling
Full text linkIn this paper, we consider the problem of imposing Virtual Holonomic Constraints to mechanical systems in Euler-Lagrangian form under sampling. An exact solution based on multi-rate sampling of order two over each input channel is described. The results are applied to orbital stabilization of the pendubot with illustrative simulations
Beta 1-integrin expression and function in human bladder cancer cells: modulation by TNF-alpha.
No full textCytofluorimetric and biochemical analysis ill two different grade human bladder cancer cell lines showed that G3 EJ cells exhibited higher levels of alpha 5 beta 1 and alpha 6 beta 1 heterodimers, and the G2 RT112 cell line higher levels of alpha 2 beta 1. Alpha6/beta4 receptor was detected only in RT112 cells. Adhesion assays with extracellular matrix proteins indicated that both cells bound to fibronectin, laminin and collagen I, the adhesive properties bring related to the integrin profile. Inhibition tests revealed that alpha 5 beta 1 mediated adhesion to fibronectin, alpha 3 beta 1 and alpha 6 beta 1 to laminin, and that alpha 2 beta 1 was the main mediator of adhesion to collagen I in both cell lines. In EJ but not in RT112 cells, tumor necrosis factor-alpha induced the upregulation of alpha 2, which mediated increased adhesion to collagen I. The different effects of TNF alpha on the two cell lines were not attributable to differences in tumor necrosis factor responsiveness, as both cells expressed comparable levels of tumor necrosis factor receptor-1 and the tumor necrosis factor-inducible intercellular adhesion molecule-1
A gradient descent algorithm built on approximate discrete gradients
Full text linkWe propose an optimization method obtained by the approximation of a novel discretization approach for gradient dynamics recently proposed by the authors. It is shown that the proposed algorithm ensures convergence for all amplitudes of the step size, contrarily to classical implementations
Stabilization of the Acrobot via sampled-data passivity-based control
Full text linkThe paper deals with the sampled-data asymptotic stabilization of the Acrobot at its upward equilibrium. The proposed controller results from the action of an Input-Hamiltonian-Matching (IHM) strategy that shapes the closed-loop energy combined with a Damping Injection (DI) feedback designed on the sampled-data equivalent model. Simulations show the effectiveness of the proposed controller
Discrete-time energy-balance passivity-based control
Full text linkIn this paper, new results for passivation and stabilization of discrete-time nonlinear systems via energy balancing are established. When specified on sampled-data systems, the approach is constructive for computing stabilizing digital controllers that assign, at all sampling instants, a target energy profile while stabilizing a target equilibrium. The class of mechanical systems is discussed as an example. Simulations are reported highlighting, for position regulation of a 2R robot, the effect of approximate solutions with respect to standard emulation
A new distributed protocol for consensus of discrete-time systems
Full text linkIn this paper, a new distributed protocol is proposed to force consensus in a discrete-time network of scalar agents with an arbitrarily assignable convergence rate. Several simulations validate the performances and the improvements with respect to more standard protocols
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