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Karl D. Iagnemma - One of the best experts on this subject based on the ideXlab platform.

  • Optimal motion planning with the half-car Dynamical Model for autonomous high-speed driving
    2013 American Control Conference, 2013
    Co-Authors: Raghvendra V. Cowlagi, Panagiotis Tsiotras, Steven C Peters, Emilio Frazzoli, Karl D. Iagnemma
    Abstract:

    We discuss an implementation of the RRT∗ op- timal motion planning algorithm for the half-car Dynamical Model to enable autonomous high-speed driving. To develop fast solutions of the associated local steering problem, we observe that the motion of a special point (namely, the front center of oscillation) can be Modeled as a double integrator augmented with fictitious inputs. We first map the constraints on tire friction forces to constraints on these augmented inputs, which provides instantaneous, state-dependent bounds on the curvature of geometric paths feasibly traversable by the front center of oscillation. Next, we map the vehicle’s actual inputs to the augmented inputs. The local steering problem for the half- car Dynamical Model can then be transformed to a simpler steering problem for the front center of oscillation, which we solve efficiently by first constructing a curvature-bounded geometric path and then imposing a suitable speed profile on this geometric path. Finally, we demonstrate the efficacy of the proposed motion planner via numerical simulation results

R Beck - One of the best experts on this subject based on the ideXlab platform.

  • a Dynamical Model for the heavily ram pressure stripped virgo spiral galaxy ngc 4522
    Astronomy and Astrophysics, 2006
    Co-Authors: B Vollmer, M Soida, K Otmianowskamazur, Jeffrey D P Kenney, J H Van Gorkom, R Beck
    Abstract:

    Context. Recent Hi and H α observations of NGC 4522 have revealed that this spiral galaxy represents one of the best cases of ongoing ram pressure stripping in the Virgo cluster. Aims. We determined the parameters of the interaction between the interstellar medium of NGC 4522 and the intracluster medium of the Virgo cluster. Methods. A Dynamical Model including ram pressure stripping is applied to the strongly Hi deficient Virgo spiral galaxy NGC 4522. A carefully chosen Model snapshot is compared with existing VLA Hi observations. Results. The Model successfully reproduces the large-scale gas distribution and the velocity field. However it fails to reproduce the large observed Hi linewidths in the extraplanar component, for which we give possible explanations. In a second step, we solve the induction equation on the velocity fields of the Dynamical Model and calculate the large scale magnetic field. Assuming a Gaussian distribution of relativistic electrons we obtain the distribution of polarized radio continuum emission which is also compared with our VLA observations at 6 cm. The observed maximum of the polarized radio continuum emission is successfully reproduced. Our Model suggests that the ram pressure maximum occurred only ∼ 50 Myr ago. Conclusions. Since NGC 4522 is located far away from the cluster center ( ∼ 1 Mpc) where the intracluster medium density is too low to cause the observed stripping if the intracluster medium is static and smooth, two scenarios are envisaged: (i) the galaxy moves very rapidly within the intracluster medium and is not even bound to the cluster; in this case the galaxy has just passed the region of highest intracluster medium density; (ii) the intracluster medium is not static but moving due to the infall of the M 49 group of galaxies. In this case the galaxy has just passed the region of highest intracluster medium velocity. This study shows the strength of combining high resolution Hi and polarized radio continuum emission with detailed numerical Modeling of the evolution of the gas and the large-scale magnetic field.

  • a Dynamical Model for the heavily ram pressure stripped virgo spiral galaxy ngc 4522
    arXiv: Astrophysics, 2006
    Co-Authors: B Vollmer, M Soida, K Otmianowskamazur, Jeffrey D P Kenney, J H Van Gorkom, R Beck
    Abstract:

    A Dynamical Model including ram pressure stripping is applied to the strongly HI deficient Virgo spiral galaxy NGC 4522. A carefully chosen Model snapshot is compared with existing VLA HI observations. The Model successfully reproduces the large-scale gas distribution and the velocity field. However it fails to reproduce the large observed HI linewidths in the extraplanar component, for which we give possible explanations. In a second step, we solve the induction equation on the velocity fields of the Dynamical Model and calculate the large scale magnetic field. Assuming a Gaussian distribution of relativistic electrons we obtain the distribution of polarized radio continuum emission which is also compared with our VLA observations at 6 cm. The observed maximum of the polarized radio continuum emission is successfully reproduced. Our Model suggests that the ram pressure maximum occurred only ~50 Myr ago. Since NGC 4522 is located far away from the cluster center (~1 Mpc) where the intracluster medium density is too low to cause the observed stripping if the intracluster medium is static and smooth, two scenarios are envisaged: (i) the galaxy moves very rapidly within the intracluster medium and is not even bound to the cluster; in this case the galaxy has just passed the region of highest intracluster medium density; (ii) the intracluster medium is not static but moving due to the infall of the M49 group of galaxies. In this case the galaxy has just passed the region of highest intracluster medium velocity. This study shows the strength of combining high resolution HI and polarized radio continuum emission with detailed numerical Modeling of the evolution of the gas and the large-scale magnetic field.

Yūki Sugiyama - One of the best experts on this subject based on the ideXlab platform.

  • Dynamical Model of a cooperative driving system for freeway traffic
    Physical Review E, 2003
    Co-Authors: Katsuya Hasebe, Akihiro Nakayama, Yūki Sugiyama
    Abstract:

    We propose an extended optimal velocity Model applicable to cooperative driving control system, which will be realized in the near future. In the Model, a vehicle is controlled by the system using the information of arbitrary number of vehicles that precede or follow. We investigate the stability of uniform flow and the response to a disturbance in the linear approximation.

  • Dynamical Model of traffic congestion and numerical simulation
    Physical Review E, 1995
    Co-Authors: Masako Bando, Katsuya Hasebe, Atsuko Nakayama, Akira Shibata, Yūki Sugiyama
    Abstract:

    We present a Dynamical Model of traffic congestion based on the equation of motion of each vehicle. In this Model, the legal velocity function is introduced, which is a function of the headway of the preceding vehicle. We investigate this Model with both analytic and numerical methods. The stability of traffic flow is analyzed, and the evolution of traffic congestion is observed with the development of time.

  • Phenomenological Study of Dynamical Model of Traffic Flow
    Journal de Physique I, 1995
    Co-Authors: Masako Bando, Katsuya Hasebe, Ken Nakanishi, Akihiro Nakayama, Akihiro Shibata, Yūki Sugiyama
    Abstract:

    We show that the Car Following Model with Optimal Velocity (Optimal Velocity Model), which was proposed in our previous paper, is a successful traffic Model in reproducing the characteristic features of observed traffic flow data. In our Model the transition from free flow to congested flow occurs spontaneously by the collective motion of vehicles, which obey to the same Dynamical equation. The observed specific discrepancy of traffic flow vs. car density graph is well understood in terms of the phase transition in our Model.

Maria Selina Nitschai - One of the best experts on this subject based on the ideXlab platform.

  • first gaia Dynamical Model of the milky way disc with six phase space coordinates a test for galaxy dynamics
    Monthly Notices of the Royal Astronomical Society, 2020
    Co-Authors: Maria Selina Nitschai, Michele Cappellari, N Neumayer
    Abstract:

    We construct the first comprehensive Dynamical Model for the high-quality subset of stellar kinematics of the Milky Way disc, with full 6D phase-space coordinates, provided by the Gaia Data Release 2. We adopt an axisymmetric approximation and use an updated Jeans Anisotropic Modelling (JAM) method, which allows for a generic shape and radial orientation of the velocity ellipsoid, as indicated by the Gaia data, to fit the mean velocities and all three components of the intrinsic velocity dispersion tensor. The Milky Way is the first galaxy for which all intrinsic phase space coordinates are available, and the kinematics are superior to the best integral-field kinematics of external galaxies. This situation removes the long-standing Dynamical degeneracies and makes this the first Dynamical Model highly over-constrained by the kinematics. For these reasons, our ability to fit the data provides a fundamental test for both galaxy dynamics and the mass distribution in the Milky Way disc. We tightly constrain the volume average total density logarithmic slope, in the radial range 3.6--12 kpc, to be $\alpha_{\rm tot}=-2.149\pm 0.055$ and find that the dark halo slope must be significantly steeper than $\alpha_{\rm DM}=-1$ (NFW). The dark halo shape is close to spherical and its density is $\rho_{\rm DM}(R_\odot)=0.0115\pm0.0020$ M$_\odot$ pc$^{-3}$ ($0.437\pm0.076$ GeV cm$^{-3}$), in agreement with previous estimates. The circular velocity at the solar position $v_{\rm circ}(R_{\odot}) = 236.5\pm 3.1$ km s$^{-1}$ (including systematics) and its gently declining radial trends are also consistent with recent determinations.

Raghvendra V. Cowlagi - One of the best experts on this subject based on the ideXlab platform.

  • Optimal motion planning with the half-car Dynamical Model for autonomous high-speed driving
    2013 American Control Conference, 2013
    Co-Authors: Raghvendra V. Cowlagi, Panagiotis Tsiotras, Steven C Peters, Emilio Frazzoli, Karl D. Iagnemma
    Abstract:

    We discuss an implementation of the RRT∗ op- timal motion planning algorithm for the half-car Dynamical Model to enable autonomous high-speed driving. To develop fast solutions of the associated local steering problem, we observe that the motion of a special point (namely, the front center of oscillation) can be Modeled as a double integrator augmented with fictitious inputs. We first map the constraints on tire friction forces to constraints on these augmented inputs, which provides instantaneous, state-dependent bounds on the curvature of geometric paths feasibly traversable by the front center of oscillation. Next, we map the vehicle’s actual inputs to the augmented inputs. The local steering problem for the half- car Dynamical Model can then be transformed to a simpler steering problem for the front center of oscillation, which we solve efficiently by first constructing a curvature-bounded geometric path and then imposing a suitable speed profile on this geometric path. Finally, we demonstrate the efficacy of the proposed motion planner via numerical simulation results