35,862 research outputs found
Data compression for estimation of the physical parameters of stable and unstable linear systems
A two-stage method for the identification of physical system parameters from experimental data is presented. The first stage compresses the data as an empirical model which encapsulates the data content at frequencies of interest. The second stage then uses data extracted from the empirical model of the first stage within a nonlinear estimation scheme to estimate the unknown physical parameters. Furthermore, the paper proposes use of exponential data weighting in the identification of partially unknown, unstable systems so that they can be treated in the same framework as stable systems. Experimental data are used to demonstrate the efficacy of the proposed approach
Estimation of the parameters of continuous-time systems using data compression
This chapter provides a unified introductory account of the estimation of the parameters of continuous-time systems using data compression based on a number of previous publication
Image enhancement from a stabilised video sequence
The aim of video stabilisation is to create a new video sequence where the motions (i.e. rotations, translations) and scale differences between frames (or parts of a frame) have effectively been removed. These stabilisation effects can be obtained via digital video processing techniques which use the information extracted from the video sequence itself, with no need for additional hardware or knowledge about camera physical motion.
A video sequence usually contains a large overlap between successive frames, and regions of the same scene are sampled at different positions. In this paper, this multiple sampling is combined to achieve images with a higher spatial resolution. Higher resolution imagery play an important role in assisting in the identification of people, vehicles, structures or objects of interest captured by surveillance cameras or by video cameras used in face recognition, traffic monitoring, traffic law reinforcement, driver assistance and automatic vehicle guidance systems
Frequency response functions and modal parameters of a rotating system exhibiting rotating damping
In the analysis of the stability threshold speed caused by rotating damping in rotating machinery, there is
a lack of experimental data. This stability threshold speed can be found theoretically by means of a linear
speed dependent model. The accuracy of the model depends highly upon the linearity and especially on the
damping type that has been chosen. In this paper, the theoretical model and the importance of the stability
analysis is discussed together with an experiment to validate the model. A rotating shaft is used to extract
frequency response functions at different speeds. The shaft is excited with an automated impact hammer and
the response is measured by eddy current probes. From these frequency response functions, the poles are
extracted and compared to the poles derived from the model. It is found that the imaginary part of the poles,
or the Campbell diagram, agrees quite well. The decay rate plot shows a similar increase as from the model,
but there seems to be an extra stabilizing effect that is not accounted for in the model
Deep Reinforcement Learning for Tensegrity Robot Locomotion
Tensegrity robots, composed of rigid rods connected by elastic cables, have a
number of unique properties that make them appealing for use as planetary
exploration rovers. However, control of tensegrity robots remains a difficult
problem due to their unusual structures and complex dynamics. In this work, we
show how locomotion gaits can be learned automatically using a novel extension
of mirror descent guided policy search (MDGPS) applied to periodic locomotion
movements, and we demonstrate the effectiveness of our approach on tensegrity
robot locomotion. We evaluate our method with real-world and simulated
experiments on the SUPERball tensegrity robot, showing that the learned
policies generalize to changes in system parameters, unreliable sensor
measurements, and variation in environmental conditions, including varied
terrains and a range of different gravities. Our experiments demonstrate that
our method not only learns fast, power-efficient feedback policies for rolling
gaits, but that these policies can succeed with only the limited onboard
sensing provided by SUPERball's accelerometers. We compare the learned feedback
policies to learned open-loop policies and hand-engineered controllers, and
demonstrate that the learned policy enables the first continuous, reliable
locomotion gait for the real SUPERball robot. Our code and other supplementary
materials are available from http://rll.berkeley.edu/drl_tensegrityComment: International Conference on Robotics and Automation (ICRA), 2017.
Project website link is http://rll.berkeley.edu/drl_tensegrit
Pressure Bifurcation Phenomenon on Supersonic Blowing Trailing Edges
Turbine blades operating in transonic-supersonic regime develop a complex
shock wave system at the trailing edge, a phenomenon that leads to unfavorable
pressure perturbations downstream and can interact with other turbine stages.
Understanding the fluid behavior of the area adjacent to the trailing edge is
essential in order to determine the parameters that have influence on these
pressure fluctuations. Colder flow, bled from the high-pressure compressor, is
often purged at the trailing edge to cool the thin blade edges, affecting the
flow behavior and modulating the intensity and angle of the shock waves system.
However, this purge flow can sometimes generate non-symmetrical configurations
due to a pressure difference that is provoked by the injected flow. In this
work, a combination of RANS simulations and global stability analysis is
employed to explain the physical reasons of this flow bifurcation. Analyzing
the features that naturally appear in the flow and become dominant for some
value of the parameters involved in the problem, an anti-symmetrical global
mode, related to the sudden geometrical expansion of the trailing edge slot, is
identified as the main mechanism that forces the changes in the flow topology.Comment: Submitted to AIAA Journa
- ā¦