7,471 research outputs found
Identification of Linear Systems with Multiplicative Noise from Multiple Trajectory Data
We study identification of linear systems with multiplicative noise from
multiple trajectory data. A least-squares algorithm, based on exploratory
inputs, is proposed to simultaneously estimate the parameters of the nominal
system and the covariance matrix of the multiplicative noise. The algorithm
does not need prior knowledge of the noise or stability of the system, but
requires mild conditions of inputs and relatively small length for each
trajectory. Identifiability of the noise covariance matrix is studied, showing
that there exists an equivalent class of matrices that generate the same
second-moment dynamic of system states. It is demonstrated how to obtain the
equivalent class based on estimates of the noise covariance. Asymptotic
consistency of the algorithm is verified under sufficiently exciting inputs and
system controllability conditions. Non-asymptotic estimation performance is
also analyzed under the assumption that system states and noise are bounded,
providing vanishing high-probability bounds as the number of trajectories grows
to infinity. The results are illustrated by numerical simulations
Long-tail Behavior in Locomotion of Caenorhabditis elegans
The locomotion of Caenorhabditis elegans exhibits complex patterns. In
particular, the worm combines mildly curved runs and sharp turns to steer its
course. Both runs and sharp turns of various types are important components of
taxis behavior. The statistics of sharp turns have been intensively studied.
However, there have been few studies on runs, except for those on klinotaxis
(also called weathervane mechanism), in which the worm gradually curves toward
the direction with a high concentration of chemicals; this phenomenon was
discovered recently. We analyzed the data of runs by excluding sharp turns. We
show that the curving rate obeys long-tail distributions, which implies that
large curving rates are relatively frequent. This result holds true for
locomotion in environments both with and without a gradient of NaCl
concentration; it is independent of klinotaxis. We propose a phenomenological
computational model on the basis of a random walk with multiplicative noise.
The assumption of multiplicative noise posits that the fluctuation of the force
is proportional to the force exerted. The model reproduces the long-tail
property present in the experimental data.Comment: 30 pages, 11 figures, some errors were correcte
Invariant EKF Design for Scan Matching-aided Localization
Localization in indoor environments is a technique which estimates the
robot's pose by fusing data from onboard motion sensors with readings of the
environment, in our case obtained by scan matching point clouds captured by a
low-cost Kinect depth camera. We develop both an Invariant Extended Kalman
Filter (IEKF)-based and a Multiplicative Extended Kalman Filter (MEKF)-based
solution to this problem. The two designs are successfully validated in
experiments and demonstrate the advantage of the IEKF design
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