This thesis is concerned with the use of Artificial Intelligence techniques to
support human designers. The thesis argues that support for human designers can
be improved by adopting an Al-based rather than a geometry-based approach to
engineering design. Design Support Systems (DSSs) are proposed as an effective
means of delivering this improved support. Representing and reasoning about
tolerance statements in design is introduced as a valid area to test these claims.
Tolerance statements describe the allowable variations in the geometry of a
designed artefact. Two distinct, but related problems involving the use of toler¬
ance statements in design are tackled, namely: tolerance combination (including
the way tolerance distributions combine), and tolerance allocation. The problem
of tolerance combination (and distribution) involves determining the necessary
consequences of the application of known tolerance statements to one or more
designed artefact features. Tolerance allocation concerns the assignment of tol¬
erance statements during the design process. Solutions to this second problem
are essential before manufactured instances of designed artefacts can be tested for
compliance with design descriptions.
The use of an experimental DSS, the Edinburgh Designer System (EDS), to
solve design problems is illustrated. The implementation of techniques to im¬
prove the support of tolerance combination and tolerance allocation is described
and where possible has been tested using EDS. The way that design is situated
within the product creation process is investigated and the derivation of parts
list information from an EDS design description is demonstrated. The thesis con¬
cludes that the Al-based approach can improve support for human designers, but
that further research will be required to demonstrate the effective delivery of this
support through DSSs
