Simultaneous maximum-likelihood calibration of odometry and sensor parameters

For a differential-drive mobile robot equipped with an on-board range sensor, there are six parameters to calibrate: three for the odometry (radii and distance between the wheels), and three for the pose of the sensor with respect to the robot frame. This paper describes a method for calibrating all six parameters at the same time, without the need for external sensors or devices. Moreover, it is not necessary to drive the robot along particular trajectories. The available data are the measures of the angular velocities of the wheels and the range sensor readings. The maximum-likelihood calibration solution is found in a closed form

On the Recognition of Fuzzy Circular Interval Graphs

Fuzzy circular interval graphs are a generalization of proper circular arc graphs and have been recently introduced by Chudnovsky and Seymour as a fundamental subclass of claw-free graphs. In this paper, we provide a polynomial-time algorithm for recognizing such graphs, and more importantly for building a suitable representation.Comment: 12 pages, 2 figure

Gait generation via intrinsically stable MPC for a multi-mass humanoid model

We consider the problem of generating a gait with no a priori assigned footsteps while taking into account the contribution of the swinging leg to the total Zero Moment Point (ZMP). This is achieved by considering a multi-mass model of the humanoid and distinguishing between secondary masses with known pre-defined motion and the remaining, primary, masses. In the case of a single primary mass with constant height, it is possible to transform the original gait generation problem for the multi-mass system into a single LIP-like problem. We can then take full advantage of an intrinsically stable MPC framework to generate a gait that takes into account the swinging leg motion

Domination between traffic matrices

A traffic matrix D-1 dominates a traffic matrix D-2 if any capacity reservation supporting D-1 supports D-2 as well. We prove that D-1 dominates D-2 if and only if D-1, considered as a capacity reservation, supports D-2. We show several generalizations of this result

A Bayesian framework for optimal motion planning with uncertainty

Modeling robot motion planning with uncertainty in a Bayesian framework leads to a computationally intractable stochastic control problem. We seek hypotheses that can justify a separate implementation of control, localization and planning. In the end, we reduce the stochastic control problem to path- planning in the extended space of poses x covariances; the transitions between states are modeled through the use of the Fisher information matrix. In this framework, we consider two problems: minimizing the execution time, and minimizing the final covariance, with an upper bound on the execution time. Two correct and complete algorithms are presented. The first is the direct extension of classical graph-search algorithms in the extended space. The second one is a back-projection algorithm: uncertainty constraints are propagated backward from the goal towards the start state

La desregulación del Mercado de Energía y la nueva regulación. La política energética. El caso europeo

Desde principios de los años noventa se ha presenciado un proceso de desregulación de distintos mercados de servicios tradicionalmente conocidos como servicios públicos, entre ellos los energéticos (gas y electricidad), que se ha verificado en diversas partes del mundo y que aún continúa. Este trabajo pretende explicar de una manera simple cuáles son los motivos, los objetivos y los mecanismos que se utilizan para desregular los mercados de energía. El análisis se circunscribirá a los mercados de gas y electricidad, y hará una referencia más precisa al caso europeo. Se cita el ejemplo de la Unión Europea (UE) porque además de la desregulación de los mercados nacionales este bloque pretende también llevar a cabo la integración energética en ese mercado regional. La integración energética no sólo reviste importancia para la desregulación sino también para mejorar la seguridad del suministro. Además, debe tenerse en cuenta que la UE se ampliará en el corto plazo sustancialmente, ya que hay varios países de Europa oriental, central y sur que están ya ingresando a la UE o negociando la accesión, además de algunos otros, como Noruega, que hasta ahora no han querido adherirse pero que podrían querer hacerlo en el mediano o largo plazo. De manera que estamos hablando de una región no sólo importante sino con un peso mundial en crecimiento. No obstante, este trabajo no va a limitarse al análisis de la desregulación y apertura del mercado de energía, sino que va a analizar otras cuestiones importantes de la política energética, en particular, la seguridad del abastecimiento energético y la política ambiental.mercado de energía; abastecimiento energético; política ambiental; servicios públicos

MPC-based humanoid pursuit-evasion in the presence of obstacles

We consider a pursuit-evasion problem between humanoids in the presence of obstacles. In our scenario, the pursuer enters the safety area of the evader headed for collision, while the latter executes a fast evasive motion. Control schemes are designed for both the pursuer and the evader. They are structurally identical, although the objectives are different: the pursuer tries to align its direction of motion with the line- of-sight to the evader, whereas the evader tries to move in a direction orthogonal to the line-of-sight to the pursuer. At the core of the control architecture is a Model Predictive Control scheme for generating a stable gait. This allows for the inclusion of workspace obstacles, which we take into account at two levels: during the determination of the footsteps orientation and as an explicit MPC constraint. We illustrate the results with simulations on NAO humanoids

Clique-circulants and the stable set polytope of fuzzy circular interval graphs

In this paper, we give a complete and explicit description of the rank facets of the stable set polytope for a class of claw-free graphs, recently introduced by Chudnovsky and Seymour (Proceedings of the Bristish Combinatorial Conference, 2005), called fuzzy circular interval graphs. The result builds upon the characterization of minimal rank facets for claw-free graphs by Galluccio and Sassano (J. Combinatorial Theory 69:1-38, 2005) and upon the introduction of a superclass of circulant graphs that are called clique-circulants. The new class of graphs is invetigated in depth. We characterize which clique-circulants C are facet producing, i.e. are such that Sigma upsilon epsilon V(C) chi(upsilon) <= alpha(C) is a facet of STAB(C), thus extending a result of Trotter (Discrete Math. 12:373-388, 1975) for circulants. We show that a simple clique family inequality (Oriolo, Discrete Appl. Math. 132(2):185-201, 2004) may be associated with each clique-circulant C subset of G, when G is fuzzy circular interval. We show that these inequalities provide all the rank facets of STAB(G), if G is a fuzzy circular interval graph. Moreover we conjecture that, in this case, they also provide all the non-rank facets of STAB(G) and offer evidences for this conjecture