This research concerns the integration of Adaptive Search (AS) technique such as the
Genetic Algorithms (GA) with knowledge based software to develop a research prototype
of an Adaptive Search Manager (ASM). The developed approach allows to utilise both
quantitative and qualitative information in engineering design decision making. A Fuzzy
Expert System manipulates AS software within the design environment concerning the
preliminary design of gas turbine blade cooling systems. Steady state cooling hole geometry
models have been developed for the project in collaboration with Rolls Royce plc. The
research prototype of ASM uses a hybrid of Adaptive Restricted Tournament Selection
(ARTS) and Knowledge Based Hill Climbing (KBHC) to identify multiple "good" design
solutions as potential design options. ARTS is a GA technique that is particularly suitable
for real world problems having multiple sub-optima. KBHC uses information gathered
during the ARTS search as well as information from the designer to perform a deterministic
hill climbing. Finally, a local stochastic hill climbing fine tunes the "good" designs. Design
solution sensitivity, design variable sensitivities and constraint sensitivities are calculated
following Taguchi's methodology, which extracts sensitivity information with a very small
number of model evaluations. Each potential design option is then qualitatively evaluated
separately for manufacturability, choice of materials and some designer's special preferences
using the knowledge of domain experts. In order to guarantee that the qualitative evaluation
module can evaluate any design solution from the entire design space with a reasonably
small number of rules, a novel knowledge representation technique is developed. The
knowledge is first separated in three categories: inter-variable knowledge, intra-variable
knowledge and heuristics. Inter-variable knowledge and intra-variable knowledge are then
integrated using a concept of compromise. Information about the "good" design solutions is
presented to the designer through a designer's interface for decision support.Rolls Royce plc., Bristol (UK
