3 research outputs found
Survey on Flight Control Technology for Large-Scale Helicopter
A literature review of flight control technology is presented for large-scale helicopter. Challenges of large-scale helicopter flight control system (FCS) design are illustrated. Following this, various flight control methodologies are described with respect to their engineering implementation and theoretical developments, whose advantages and disadvantages are also analyzed. Then, the challenging research issues on flight control technology are identified, and future directions are highlighted
Approximate Reasoning in Hydrogeological Modeling
The accurate determination of hydraulic conductivity is an important element of successful groundwater flow and transport modeling. However, the exhaustive measurement of this hydrogeological parameter is quite costly and, as a result, unrealistic. Alternatively, relationships between hydraulic conductivity and other hydrogeological variables less costly to measure have been used to estimate this crucial variable whenever needed. Until this point, however, the majority of these relationships have been assumed to be crisp and precise, contrary to what intuition dictates. The research presented herein addresses the imprecision inherent in hydraulic conductivity estimation, framing this process in a fuzzy logic framework. Because traditional hydrogeological practices are not suited to handle fuzzy data, various approaches to incorporating fuzzy data at different steps in the groundwater modeling process have been previously developed. Such approaches have been both redundant and contrary at times, including multiple approaches proposed for both fuzzy kriging and groundwater modeling. This research proposes a consistent rubric for the handling of fuzzy data throughout the entire groundwater modeling process. This entails the estimation of fuzzy data from alternative hydrogeological parameters, the sampling of realizations from fuzzy hydraulic conductivity data, including, most importantly, the appropriate aggregation of expert-provided fuzzy hydraulic conductivity estimates with traditionally-derived hydraulic conductivity measurements, and utilization of this information in the numerical simulation of groundwater flow and transport
Towards UAV-assisted monitoring of onshore geological CO2 storage site
Scientists all over the world look for solutions to reduce
greenhouse gas emissions in an effort to achieve proclaimed
emissions reduction targets. An intriguing candidate with the
potential to make a substantial contribution to this attempt is
carbon capture and storage (CCS). The key advantage of CCS is
that it provides the possibility to make a significant impact on
the reduction of anthropogenic carbon dioxide (CO2) emissions
from power plants and carbon-rich industry processes while
maintaining existing fossil fuel energy infrastructure. The
technique could therefore be used as a transitional solution
until fossil fuels can be eliminated from the energy generation
mix, and the energy efficiency of industrial processes as well as
appliances and products is further improved.
Like other technologies, CCS comes with its risks and rewards. To
minimize possible negative impacts on humans as well as on the
environment, it is necessary to understand the risks and to
address them accordingly. A range of monitoring solutions for
geological CO2 storage sites is available. However, a
cost-effective solution for the regular observation of
atmospheric CO2 concentrations (or tracer concentrations) of
large areas above onshore geological CO2 storage sites has yet to
be developed.
This thesis discusses the use of a helicopter unmanned aerial
vehicle (UAV) to fill this gap. The robot platform and its
autopilot are designed to cope with ongoing sensor developments
in addition to providing safety features necessary for the beyond
line-of-sight operation of the UAV. The design focuses on the use
of commercial off-the-shelf components for the aerial platform in
order to shorten the development time and to reduce costs. The
autopilot does neither enforce a specific helicopter model nor
defines a set position estimation unit to be used. Access to the
control loop enables low-level extensions like obstacle avoidance
to be implemented. The developed solution allows the monitoring
of an area of approximately 750m2 with one set of batteries in
one altitude with a spatial resolution of 2m by 2m. Experiments
show that point source leaks of as low as 100kg CO2 per day can
be detected and their source located.
As opposed to autonomous take-offs of the helicopter UAV,
autonomous landings on small dedicated helipads require an
accurate localization system. A time difference of arrival (TDOA)
based acoustic localization system which is based on planar
microphone arrays with at least four microphones is proposed. The
system can be embedded into the landing platform and provides the
accuracy necessary to land the UAV on a helipad of the size of 1m
by 1m. A review of existing TDOA-based approaches is given.
Simulations show that the developed approach outperforms its
direct competitors for the targeted task. Furthermore,
experimental results with the developed UAV confirm the
feasibility of the introduced method. The effects of the sensor
arrangement onto the quality of the calculated position estimates
are also discussed.
In order to combine robotic-assisted monitoring solutions and
other monitoring strategies (e.g. sensor networks and individual
sensors) into a single solution, it is necessary to have a
framework which allows next to the measurement data analysis also
the management (path changes, robot behavior changes, monitoring
of internal robot state) of possibly multiple heterogeneous
mobile robotic systems. A modular user interface (UI) framework
is proposed which allows robots from different vendors and with
various configurations next to individual sensors and sensor
networks to be managed from a single application. The software
system introduces a strict separation between the robot control
software and UIs. UI implementations inside the UI framework can
be reused across robot platforms, which can reduce the
integration time of new robots significantly. The end user
benefits by being able to manage a fleet of robots from various
vendors and being able to analyze all the measurement data
together in a single solution