331 research outputs found
Discrete port-controlled Hamiltonian dynamics and average passivation
The paper discusses the modeling and control of port-controlled Hamiltonian dynamics in a pure discrete-time domain. The main result stands in a novel differential-difference representation of discrete port-controlled Hamiltonian systems using the discrete gradient. In these terms, a passive output map is exhibited as well as a passivity based damping controller underlying the natural involvement of discrete-time average passivity
Multiconsensus control of homogeneous LTI hybrid systems under time-driven jumps
In 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
Stabilization of the Acrobot via sampled-data passivity-based control
The 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
A gradient descent algorithm built on approximate discrete gradients
We 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
Discrete-time energy-balance passivity-based control
In 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
Sampled-data steering of unicycles via PBC
In this paper, on the basis of a recently proposed discrete-time port-Hamiltonian representation of sampled-data dynamics, we propose a new time-varying digital feedback for steering mobile robots. The quality of the proposed passivity-based control is validated and compared through simulations with the existing literature and the continuous-time implementation using the unicycle as a case study
Quaternion-Based Attitude Stabilization via Discrete-Time IDA-PBC
In this letter, we propose a new sampled-data controller for stabilization of the attitude dynamics at a desired constant configuration. The design is based on discrete-time interconnection and damping assignment (IDA) passivity-based control (PBC) and the recently proposed Hamiltonian representation of discrete-time nonlinear dynamics. Approximate solutions are provided with simulations illustrating performances
RNF11 (ring finger protein 11)
Review on RNF11, with data on DNA/RNA, on the protein encoded and where the gene is implicated
Long Range Bond-Bond Correlations in Dense Polymer Solutions
The scaling of the bond-bond correlation function along linear polymer
chains is investigated with respect to the curvilinear distance, , along the
flexible chain and the monomer density, , via Monte Carlo and molecular
dynamics simulations. % Surprisingly, the correlations in dense three
dimensional solutions are found to decay with a power law with and the exponential behavior commonly assumed is
clearly ruled out for long chains. % In semidilute solutions, the density
dependent scaling of with
( being Flory's exponent) is set by the
number of monomers contained in an excluded volume blob of size
. % Our computational findings compare well with simple scaling arguments
and perturbation calculation. The power-law behavior is due to
self-interactions of chains on distances caused by the connectivity
of chains and the incompressibility of the melt. %Comment: 4 pages, 4 figure
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