Modelling spatial and non-spatial conflicts across multiple design domains

Abstract

This thesis aims to detect spatial and non-spatial conflicts in product design arising out of requirements in different design domains. Handling such conflicts requires modelling the non-geometric knowledge outside the computer-aided-design (CAD) model and associating it with product geometry in the CAD model. Product knowledge needs to be identified and structured to help detect spatial and non-spatial conflicts. System modelling Language (SysML) is used to model the product knowledge, specifically product structure, unoccupied or empty space blocks, product life-cycle states, and design domains. SysML Requirements diagram is used to model the design requirements. Block definition diagrams (BDD) model the product structure with empty space blocks. The relationship between Product life-cycle states and design domains is established through product structure and empty space blocks. The unused space blocks are allocated to design requirements from different domains based on the relationship modelled. These blocks are used to capture and represent knowledge inside CAD tools. Identification and decomposition of empty spaces inside CAD have been discussed, and an algorithm has been developed for automating the decomposition task for empty space blocks. A method of modelling intended empty spaces using parametric primitive shapes has also been described. An algorithm has been developed to capture the relationship between the empty space blocks and the associated design domains, product life-cycle states, and design requirements. An algorithm has been developed to identify and represent associativity between these blocks and features in the CAD model. Two case studies involving heat sink assembly and coupled-cavity slow-wave structure have been discussed to demonstrate and validate the framework for empty space modelling. Spatial conflict detection using graph-based and matrix-based approaches like DSM, DMM, and MDM, have been discussed and implemented. Two different methods were developed for spatial conflict detection and evaluated for ease of implementation and visualization. Two case studies of Coupled-cavity travelling wave tube (CCTWT) Slow-wave structure (SWS) design and high-power RF window design are used to showcase the detection of spatial conflicts under multiple design domains. Next, the thesis proposes using an octree model to represent the spatial conflicts across multiple design domains. This approach has the advantage of independence from the CAD system for computations and visualization. It also enables the resolution of dynamic spatial conflicts. A framework has been developed to create an octree model linked with intended empty spaces in the product. The model is also connected with design requirements, product life-cycle states, and functional design domains. Two case studies of coupled-cavity travelling wave tube (CCTWT) slow-wave structure (SWS) design and high-power RF window design demonstrate the use of octree to visualize spatial conflicts outside of a CAD environment. An octree-based voxel model gives us spaces free from conflicts, which designers can recommend for locating new parts in the assembly and carrying out layout planning. Spatial conflict detection for moving parts is also implemented where conflicts are detected for dynamic cases. The octree-based voxel model is discussed and implemented to represent and compute non-spatial conflicts across multiple design domains. A framework has been developed to create an octree-based voxel model linked with physics-based non-spatial constraints. A case study of a travelling-wave tube (TWT) collector design has been taken to showcase the framework's capabilities for non-spatial conflict detection. It enables visualization of the octree model outside the CAD platform, along with spatial and non-spatial conflicts detected by associativity established between the part, physics-based constraints, and the product information available in the SysML model. The thesis concludes by summarizing the contributions made and identifying areas for further research.