Abstract |
VizCraft is a problem-solving environment that aids aircraft designers during the
conceptual design stage of a high-speed civil transport (HSCT).
At this stage, an aircraft design is defined by a vector of 10-30 parameters
(typically 29 parameters). The goal is to find a vector that minimizes a
performance-based objective function while meeting a series of constraints.
Finding this vector is not a trivial task. Considering the high dimensionality of
the problem, and given the range of values in which a variable can lie, there
are almost an infinite number of values the objective function can assume.
Thus the task of minimizing the objective function can take years, even on
a supercomputer. An alternative method could be to visualize this
optimization problem, not in 2-D or 3-D space, but in a 29-dimensional
design space. Each set of 29 design variables forms a design case, and can
be viewed as a point in a 29-D space. A design case is a specific
configuration of the aircraft, and yields one value for the objective
function. This objective function is the Take-Off Gross Weight
(TOGW) of the aircraft, and is a nonlinear implicit function of 29
variables.
In order for a particular design to be feasible, it must satisfy a
series of 68 nonlinear inequality constraints that consist of geometric,
aerodynamic, and performance constraints. These constraints are devised to
ensure feasible aircraft geometries, and to impose realistic performance
and control capabilities. If any of these 68 constraints is violated, it
renders the design meaningless, so one of the objectives of the
visualization tool is to help the designer in a careful selection of
design variables so that all design constraints are satisfied. The other,
and more significant, objective is to help in visualizing trends in the
objective function.
VizCraft offers a convenient way for the user to model the
29-dimensional design space. It offers a menu-driven graphical user
interface to the HSCT code, which is a collection of C and Fortran
routines that calculate the aircraft geometry in 3-D, the constraint
values, and TOGW, among other things. Since this is a problem of very high
dimensionality, most known visualization techniques are of little help.
VizCraft makes use of the parallel
coordinates technique for visualizing the design space. Parallel
coordinates offer a convenient way for the user to model this
multidimensional design space while retaining all the important
mathematical information contained in it. By making efficient use of
parallel coordinates, VizCraft allows the designer to visually manipulate
the design space while searching for patterns, and to eliminate portions
of the design space from consideration by carefully selecting regions of
interest.
The application of parallel coordinates along with the interactive
capabilities incorporated into VizCraft make it a solid visualization tool
for modeling higher dimensional systems like the HSCT design problem.
VizCraft is a classic example of an application where complex operations
are abstracted into a coherent form at the level of the user
interface.
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