9,756 research outputs found
Gaussian process model based predictive control
Gaussian process models provide a probabilistic non-parametric modelling approach for black-box identification of non-linear dynamic systems. The Gaussian processes can highlight areas of the input space where prediction quality is poor, due to the lack of data or its complexity, by indicating the higher variance around the predicted mean. Gaussian process models contain noticeably less coefficients to be optimized. This paper illustrates possible application of Gaussian process models within model-based predictive control. The extra information provided within Gaussian process model is used in predictive control, where optimization of control signal takes the variance information into account. The predictive control principle is demonstrated on control of pH process benchmark
Adaptive, cautious, predictive control with Gaussian process priors
Nonparametric Gaussian Process models, a Bayesian statistics approach, are used to implement a nonlinear adaptive control law. Predictions, including propagation of the state uncertainty are made over a k-step horizon. The expected value of a quadratic cost function is minimised, over this prediction horizon, without ignoring the variance of the model predictions. The general method and its main features are illustrated on a simulation example
Gaussian Process priors with uncertain inputs? Application to multiple-step ahead time series forecasting
We consider the problem of multi-step ahead prediction in time series analysis using the non-parametric Gaussian process model. k-step ahead forecasting of a discrete-time non-linear dynamic system can be performed by doing repeated one-step ahead predictions. For a state-space model of the form y t = f(Yt-1 ,..., Yt-L ), the prediction of y at time t + k is based on the point estimates of the previous outputs. In this paper, we show how, using an analytical Gaussian approximation, we can formally incorporate the uncertainty about intermediate regressor values, thus updating the uncertainty on the current prediction
Model-independent Limits from Spin-dependent WIMP Dark Matter Experiments
Spin-dependent WIMP searches have traditionally presented results within an
odd group approximation and by suppressing one of the spin-dependent
interaction cross sections. We here elaborate on a model-independent analysis
in which spin-dependent interactions with both protons and neutrons are
simultaneously considered. Within this approach, equivalent current limits on
the WIMP-nucleon interaction at WIMP mass of 50 GeV/c are either
pb, pb or ,
depending on the choice of cross section or coupling strength
representation. These limits become less restrictive for either larger or
smaller masses; they are less restrictive than those from the traditional odd
group approximation regardless of WIMP mass. Combination of experimental
results are seen to produce significantly more restrictive limits than those
obtained from any single experiment. Experiments traditionally considered
spin-independent are moreover found to severely limit the spin-dependent phase
space. The extension of this analysis to the case of positive signal
experiments is explored.Comment: 12 pages, 12 figures, submitted to Phys. Rev.
Searching for visual companions of close Cepheids. VLT/NACO lucky imaging of Y~Oph, FF~Aql, X~Sgr, W~Sgr and ~Aql
Aims: High-resolution imaging in several photometric bands can provide color
and astrometric information of the wide-orbit component of Cepheid stars. Such
measurements are needed to understand the age and evolution of pulsating stars.
In addition, binary Cepheids have the potential to provide direct and
model-independent distances and masses. Methods: We used the NAOS-CONICA
adaptive optics instrument (NACO) in the near-infrared to perform a deep search
for wide components around the classical Cepheids, Y~Oph, FF~Aql, X~Sgr, W~Sgr,
and ~Aql, within a field of view (FoV) of ( for ~Aql). Results: We were able to reach contrast -8\,mag and -7\,mag in the radius range ,
which enabled us to constrain the presence of wide companions. For Y~Oph,
FF~Aql, X~Sgr, W~Sgr, and ~Aql at , we ruled out the presence
of companions with a spectral type that is earlier than a B7V, A9V, A9V, A1V,
and G5V star, respectively. For , no companions earlier than
O9V, B3V, B4V, B2V, and B2V star, respectively, are detected. A component is
detected close to ~Aql at projected separation \,mas and a position angle . We estimated its
dereddened apparent magnitude to be and derived a
spectral type that ranges between an F1V and F6V star. Additional photometric
and astrometric measurements are necessary to better constrain this star and
check its physical association to the ~Aql system.Comment: Accepted for publication in Astronomy and Astrophysic
Absolute Proper Motions to B~22.5: V. Detection of Sagittarius Dwarf Spheroidal Debris in the Direction of the Galactic Anticenter
We have detected a population of predominantly blue (B-V <= 1.1) stars in the
direction l = 167 deg., b = -35 deg. (Kapteyn Selected Area 71) that cannot be
accounted for by standard starcount models. Down to V ~ 20, the colors and
magnitudes of these stars are similar to those of the southern overdensity
detected by the Sloan Digital Sky Survey, and identified as stripped material
from the Sagittarius dwarf spheroidal galaxy. We present absolute proper
motions for the stars in SA 71, and we find that the excess blue stars
represent a distinct, kinematically cooler component than the Galactic field,
and in reasonable agreement with predictions of Sgr disruption models. The
density of the excess SA 71 stars at V ~ 18.8 and B-V <=1.1 is within a factor
of two of the density of the SDSS-south Sgr stripped material, and of that
predicted by the Helmi and White disruption model. Three additional anticenter
fields (SA 29, 45 and 118) show very good agreement with standard starcount
models.Comment: 13 pages, 3 figures, submitted to ApJL, accepted for Ap
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