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Thomas H. Bradley Assistant Professor Department of Mechanical
Engineering, Engineering Building A103R Fort Collins, CO 80523-1374 Phone: +1 970-491-3539 |
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Lab Group |
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Ongoing Research Projects
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Design, Demonstration and Sustainability
Impacts Assessments for Plug-in Hybrid Electric Vehicles Energy Systems Engineering and Analysis Advanced Firefighter Breathing Apparatus Unmanned Long-Endurance Flight |
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Research Summary
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Automotive and Aerospace System Design – Aircraft
and automobiles are historically designed using an
design process wherin the required performance of
the vehicle is known and components are assembled to meet the performance
goals. For advanced technology
applications, this conventional design process breaks down because
uncertainties in performance, modeling, and scaling laws dominate the
design. For instance, design of fuel
cell aircraft has been performed by using aircraft performance requirements
to determine the performance requirements of a fuel cell powerplant
system. The naïve application of
automotive-type fuel cell technology to aviation applications has lead fuel
cell aircraft designers to specify fuel cell powerplant
performance requirements that are not technologically or even theoretically available. My dissertation work included the development and validation of fuel
cell powerplant models that can represent the
performance of fuel cell powerplants in aviation
applications. This effort resulted in
some of the first fuel cell component models that could be integrated with a
modern, multidisciplinary optimization-based aircraft design process. This research incorporates a number of
tools from complex system analysis including design of experiments, variable
fidelity modeling, error propagation analyses, and robust design
techniques. These techniques are
required to design in the highly constrained, uncertain design space of
advanced technology automobiles and aircraft.
The resulting design tools allowed us to deductively define the system
structure, performance requirements, and scaling laws for fuel cell aircraft powerplants. This
design work was validated by the flight in 2006 of the largest compressed
hydrogen fuel cell airplane to date (see Figure 1). Figure 1. Georgia Institute of Technology fuel cell powered aircraft
(June 2006) From 1999-2003, I worked with Dr. Andrew Frank at the University of
California – Davis to design and construct the first modern plug-in hybrid
electric vehicles (PHEVs). PHEVs are
currently considered one of the most viable means of improving the short-term
sustainability of personal transportation.
I and other collaborators designed hybrid electric powertrains for
five vehicles, many of which included continuously variable transmissions,
custom electric motors, Miller/Atkinson cycle engines and other technological
advancements. I am currently working to expand the scope of my work on system design
of fuel cell and hybrid vehicles to include new applications, constraints and
design criteria. These will include
new environmental performance constraints on PHEVs, technological sensitivity
studies for fuel cell powered UAVs, and application of complex system design
techniques to micro-grids, space systems and renewable energy systems. Integrated Vehicle Supervisory Control and Energy Management –
Vehicle-level energy management and control is an intrinsic component of
system design for advanced hybrid/fuel cell vehicles. Much of the vehicle design and assessment
work that is present in the literature uses unrefined supervisory control
schemes to control vehicle energy systems.
This results in the promotion of designs that are suboptimal and the
abandonment of designs that may demand more active energy system
control. My work focuses on the development
of dynamic models of vehicle systems that can be used to derive algorithms
for system-level performance outputs such as energy economy, endurance or
component lifetimes. Complex Engineered Systems Experiments and Validation –
Performance models or design algorithms from all types of engineering
research are improved through empirical and theoretical performance
validation. Empirical performance
validation is a measure of the usefulness of the model to describe the
behavior of an example hardware system.
Theoretical performance validation is a measure of the usefulness of
the model in describing the behavior of a set of real world systems, outside
of its example problems. My research
has focused on both the empirical and theoretical performance validation of
models for engineered systems. I, and a series of collaborators, have designed and constructed
empirical validation test equipment for analyses of continuously variable
transmission (CVT) efficiency, CVT control system energy consumption, PHEV energy
management, PHEV-specific battery lifetime, fuel cell aircraft powerplant energy consumption, and dynamic UAV energy
consumption. I have also designed and
developed hardware for theoretical performance validation including a hybrid
electric vehicle powertrain dynamometer with variable component performance,
and a fuel cell aircraft powerplant
hardware-in-the-loop simulator. Most recently, I and collaborators in the Georgia Tech Aerospace
System Design Laboratory have applied analyses of the propagation of error
through engineering models to guide the validation of complex system
models. This new application of system
sensitivity analysis allows for the sources of uncertainty in large-scale
system models to be understood for lower cost than Monte-Carlo
techniques. More importantly, these
techniques provide a framework for guiding validation of the decomposed
system for an uncertainty-constrained design process. By validating certain high impact
contributing analyses, the uncertainty of the design point can be
sequentially reduced in the transition from conceptual to detailed design. |
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© TH
Bradley 2011 |
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