Geometric and Feature modelling
Multiple-View Feature Modelling with Model Adjustment
Summary
Multiple-view feature modelling is a recently introduced approach to product development, which combines concurrent engineering and feature modelling. It supports applications from various phases of product development, by providing an own interpretation of, or view on, a product for each of these applications. Each view has its own feature model of the product. The approach can lead to a higher quality of products in less time, which is one of the most important goals of contemporary product development.
Current approaches to multiple-view feature modelling still have at least three major shortcomings. First, they focus on the later product development phases, in which the geometry of the product has to be fully specified. Second, they deal with single parts only, whereas real product rarely consists of a single part. Third, they discard the possibility that a feature model of a product for some view is invalid or that a consistent feature model in another view cannot be created.
In this thesis, a new approach to multiple-view feature modelling is described that overcomes these shortcomings. It supports high-level product design and design of products with multiple parts, in particular conceptual and assembly design. This includes consistency maintenance for the involved feature models. Further, it supports automatic adjustment of form feature models that are invalid or for which no consistent form feature model in another view can be created.
The conceptual design view allows the designer to determine the configuration of a product by specifying components, which are to be implemented by one or more parts, and interfaces between them, which are to be implemented by a connection. Components are specified by means of a base shape with shape concepts and references on it. The base shape is used to attach and position the shape concepts and references, and gives an impression of the shape of the component. Shape concepts are used to specify functional requirements on the geometry of a component, e.g. that there should be a passage, possibly with block shape, somewhere on the component. References are used to position interfaces between components, shape concepts and other references. Interfaces between components are specified by means of Degrees Of Freedom (DOFs) between references on components.
The assembly design view focuses on connection design, and allows the designer to specify the type of connection between components and the geometry for the connection on the components. A component can be a single component, which represents a single part, or a compound component, which represents multiple connected sub-components. The geometry of components only needs to be specified as far as it is involved in connections. Connections are specified on regions of the geometry of the connected components, such as a rib and a slot, and represent a reduction of the DOFs between the components.
Consistency maintenance integrates all views with each other, by ensuring that their feature models represent the same product or part of it, i.e. that their feature models are consistent. It checks the consistency of pairs of feature models, based on the consistency definitions for those pairs, and if an inconsistency is found, it recovers the consistency of the feature models. To optimise the performance and to reduce the number of consistency maintenance techniques, consistency maintenance is only performed for a minimal set of pairs that together allow all views to be kept consistent.
Automatic model adjustment is able to automatically adjust the model of a product in case the feature model of one of its views has become invalid, or a consistent feature model in another view cannot be created. In current feature modelling systems, the model of the product has to be manually adjusted in order to make an invalid feature model valid again, or to make a consistent feature model in another view possible. The main disadvantage of manually adjusting the model of a product is that it can be a lot of tedious work for a designer to get a model that satisfies all requirements on the product at the same time. Automatic model adjustment only adjusts dimensions in the feature model that are not critical for the function of the product. It has been built on top of constraint solvers for geometric and algebraic constraints and constraint checkers for dimension and interaction constraints.
This thesis shows that a multiple-view feature modelling approach can also support the earlier phases of the product development process, by describing views that support conceptual and assembly design, and their integration with views that support part detail design and manufacturing planning. In addition, it shows that automatic model adjustment is a feasible and useful technique
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Noort A (2002), Multiple-View
Feature Modelling with Model Adjustment, PhD Thesis, Delft University of
Technology, ISBN 90-9016343-3.