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http://dspace.lib.cranfield.ac.uk/handle/1826/835

Document Type:  Thesis or dissertation 
Title:  CAD interface and framework for curve optimisation applications 
Authors:  Munaux, Olivier 
Supervisors:  Jared, Graham 
Issue Date:  Sep2004 
Abstract:  Computer Aided Design is currently expanding its boundaries to include more design
features in its processes. Design is identified as an iterative process converging to solutions
satisfying a set of constraints. Its close relation with optimisation indicate that there is strong
potential for the integration of optimisation and CAD. The problem addressed in this thesis
lies in interfacing the geometric representation of design with other nongeometric aspects.
The example of freeform curve modelling is taken to investigate such relationships.
Assumptions are made that Optimisation is powered by Evolutionary Computing algorithms
like Genetic Algorithms (GA).
The geometric definition of curves is commonly supported by NURBS, whose construction
constraints are defined locally at the data points. Here the NURBS formulation is used with
GA in an attempt to provide complementary handles on the curves shape other than the usual
data point coordinates and control points weights. Differential properties are used for
optimising NURBS, Hermite interpolation allows for the definition of higher order
constraints (tangent, normal, binormal) at data points. The assignment of parameter values
at the data points, known as parameterisation also provides control of the curve’s shape.
Curve optimisation is also performed at the geometric modelling level. Old mathematical
theorems established by Frénet and further developed by other mathematicians provide
means of defining a curve’s shape with it’s intrinsic equations. Such representation is
possible by using Function Representation (Frep) algebra available in the ACIS software. Frep
allows more generic and exact means of interfacing with the curve’s geometry and new
functionality for curve inspection and optimisation are proposed in this thesis.
The integration of optimisation findings and CAD are documented in the definition of a
framework. The framework architecture proposed reconstructs a new CAD environment
from separate elements bolted together in a generic Application Programming Interface
(API) named “Oli interface”. Functionality created to interface optimisation and CAD makes
a requirement list of the work that both sides should undertake to achieve design
optimisation in the CAD environment. 
URI:  http://hdl.handle.net/1826/835 
Appears in Collections:  PhD, EngD and MSc by research theses (School of Applied Sciences)

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