130,123 research outputs found
Improving machine dynamics via geometry optimization
The central thesis of this paper is that the dynamic performance of machinery can be improved dramatically in certain cases through a systematic and meticulous evolutionary algorithm search through the space of all structural geometries permitted by manufacturing, cost and functional constraints. This is a cheap and elegant approach in scenarios where employing active control elements is impractical for reasons of cost and complexity. From an optimization perspective the challenge lies in the efficient, yet thorough global exploration of the multi-dimensional and multi-modal design spaces often yielded by such problems. Morevoer, the designs are often defined by a mixture of continuous and discrete variables - a task that evolutionary algorithms appear to be ideally suited for. In this article we discuss the specific case of the optimization of crop spraying machinery for improved uniformity of spray deposition, subject to structural weight and manufacturing constraints. Using a mixed variable evolutionary algorithm allowed us to optimize both shape and topology. Through this process we have managed to reduce the maximum roll angle of the sprayer by an order of magnitude , whilst allowing only relatively inexpensive changes to the baseline design. Further (though less dramatic) improvements were shown to be possible when we relaxed the cost constraint. We applied the same approach to the inverse problem of reducing the mass while maintaining an acceptable roll angle - a 2% improvement proved possible in this cas
Modeling of Social Transitions Using Intelligent Systems
In this study, we reproduce two new hybrid intelligent systems, involve three
prominent intelligent computing and approximate reasoning methods: Self
Organizing feature Map (SOM), Neruo-Fuzzy Inference System and Rough Set Theory
(RST),called SONFIS and SORST. We show how our algorithms can be construed as a
linkage of government-society interactions, where government catches various
states of behaviors: solid (absolute) or flexible. So, transition of society,
by changing of connectivity parameters (noise) from order to disorder is
inferred
Universality in Bacterial Colonies
The emergent spatial patterns generated by growing bacterial colonies have
been the focus of intense study in physics during the last twenty years. Both
experimental and theoretical investigations have made possible a clear
qualitative picture of the different structures that such colonies can exhibit,
depending on the medium on which they are growing. However, there are
relatively few quantitative descriptions of these patterns. In this paper, we
use a mechanistically detailed simulation framework to measure the scaling
exponents associated with the advancing fronts of bacterial colonies on hard
agar substrata, aiming to discern the universality class to which the system
belongs. We show that the universal behavior exhibited by the colonies can be
much richer than previously reported, and we propose the possibility of up to
four different sub-phases within the medium-to-high nutrient concentration
regime. We hypothesize that the quenched disorder that characterizes one of
these sub-phases is an emergent property of the growth and division of bacteria
competing for limited space and nutrients.Comment: 12 pages, 5 figure
On Advanced Mobility Concepts for Intelligent Planetary Surface Exploration
Surface exploration by wheeled rovers on Earth's Moon (the two Lunokhods) and Mars (Nasa's Sojourner and the two MERs) have been followed since many years already very suc-cessfully, specifically concerning operations over long time. However, despite of this success, the explored surface area was very small, having in mind a total driving distance of about 8 km (Spirit) and 21 km (Opportunity) over 6 years of operation. Moreover, ESA will send its ExoMars rover in 2018 to Mars, and NASA its MSL rover probably this year. However, all these rovers are lacking sufficient on-board intelligence in order to overcome longer dis-tances, driving much faster and deciding autonomously on path planning for the best trajec-tory to follow. In order to increase the scientific output of a rover mission it seems very nec-essary to explore much larger surface areas reliably in much less time. This is the main driver for a robotics institute to combine mechatronics functionalities to develop an intelligent mo-bile wheeled rover with four or six wheels, and having specific kinematics and locomotion suspension depending on the operational terrain of the rover to operate. DLR's Robotics and Mechatronics Center has a long tradition in developing advanced components in the field of light-weight motion actuation, intelligent and soft manipulation and skilled hands and tools, perception and cognition, and in increasing the autonomy of any kind of mechatronic systems. The whole design is supported and is based upon detailed modeling, optimization, and simula-tion tasks. We have developed efficient software tools to simulate the rover driveability per-formance on various terrain characteristics such as soft sandy and hard rocky terrains as well as on inclined planes, where wheel and grouser geometry plays a dominant role. Moreover, rover optimization is performed to support the best engineering intuitions, that will optimize structural and geometric parameters, compare various kinematics suspension concepts, and make use of realistic cost functions like mass and consumed energy minimization, static sta-bility, and more. For self-localization and safe navigation through unknown terrain we make use of fast 3D stereo algorithms that were successfully used e.g. in unmanned air vehicle ap-plications and on terrestrial mobile systems. The advanced rover design approach is applica-ble for lunar as well as Martian surface exploration purposes. A first mobility concept ap-proach for a lunar vehicle will be presented
Characterization and mapping of surface physical properties of Mars from CRISM multi-angular data: application to Gusev Crater and Meridiani Planum
The analysis of the surface texture from the particle (grain size, shape and
internal structure) to its organization (surface roughness) provides
information on the geological processes. CRISM multi-angular observations
(varied emission angles) allow to characterize the surface scattering behavior
which depends on the composition but also the material physical properties
(e.g., grain size, shape, internal structure, the surface roughness). After an
atmospheric correction by the Multi-angle Approach for Retrieval of the Surface
Reflectance from CRISM Observations, the surface reflectances at different
geometries are analyzed by inverting the Hapke photometric model depending on
the single scattering albedo, the 2-term phase function, the macroscopic
roughness and the 2-term opposition effects. Surface photometric maps are
created to observe the spatial variations of surface scattering properties as a
function of geological units at the CRISM spatial resolution (200m/pixel). An
application at the Mars Exploration Rover (MER) landing sites located at Gusev
Crater and Meridiani Planum where orbital and in situ observations are
available, is presented. Complementary orbital observations (e.g. CRISM
spectra, THermal EMission Imaging System, High Resolution Imaging Science
Experiment images) are used for interpreting the estimated Hapke photometric
parameters in terms of physical properties. The in situ observations are used
as ground truth to validate the interpretations. Varied scattering properties
are observed inside a CRISM observation (5x10km) suggesting that the surfaces
are controlled by local geological processes (e.g. volcanic resurfacing,
aeolian and impact processes) rather than regional or global. Consistent
results with the in situ observations are observed thus validating the approach
and the use of photometry for the characterization of Martian surface physical
properties
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