Full Vehicle Variability Modeling

Sweder, T. A.; Pollock, J.

doi:10.4271/942334

Cited by 6 publications

(2 citation statements)

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“…The second example involves over‐constraint in a car seat (Sweder and Pollock, 1994)[5]. Figure 4 shows the problem and how it was solved.…”

Section: Another Examplementioning

confidence: 99%

“…In the original design, there were four 25 mm diameter studs on the seat that had to be assembled to four 25±0.5 mm diameter holes. In the final design, the right rear hole has been enlarged into a slot 25 × 40 mm, and the front holes have been enlarged to 40 mm diameter (Sweder and Pollock, 1994, reprinted with permission from SAE Paper 942334 ©1994 Society of Automotive Engineers).…”

Section: Another Examplementioning

confidence: 99%

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Proper constraint as a design principle for assemblies

Whitney

2008

Assembly Automation

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PurposeThis paper's objective is to explain the concept of proper kinematic constraint to guide requirements‐driven design of mechanical assemblies and to connects proper constraint to the datum flow chain (DFC) and key characteristics (KCs).Design/methodology/approachThe paper presents proper constraint as a way to support the goal of placing key parts in particular geometric relationships with respect to one another so that a DFC can deliver KCs unambiguously. Such a DFC is said to be competent. Additionally, a competent DFC is robust in the sense that the constraint relationships between parts retain their definition and effect under all allowed variations in parts.FindingsFailure to provide proper constraint can lead to undesired consequences including locked‐in stresses and difficult or inconsistent assembly. Some designs need to be over‐constrained, and this requires very careful control and tight tolerances on the over‐constrained degrees of freedom in order to avoid or at least understand the consequences listed above.Research limitations/implicationsMathematical methods exist to test designs for proper constraint. The simplest, and occasionally unsuccessful, is the Kutzbach criterion. Screw theory is the most reliable method but its application requires extra knowledge and mathematical tools.Practical implicationsMost CAD software and tolerance analysis software do not test designs for their state of constraint. The engineer needs to take account of this independently and be aware of the limitations of software as a guide. Tolerance analysis software that does not take account of constraint may yield incorrect answers.Originality/valueThe paper reinvigorates a once‐well‐known principle and makes engineers aware of it. It also links this concept to the concepts of DFC and KCs and supports a mathematically‐based method for designing assemblies.

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“…The second example involves over‐constraint in a car seat (Sweder and Pollock, 1994)[5]. Figure 4 shows the problem and how it was solved.…”

Section: Another Examplementioning

confidence: 99%

Section: Another Examplementioning

confidence: 99%

Proper constraint as a design principle for assemblies

Whitney

2008

Assembly Automation

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Application of screw theory to motion analysis of assemblies of rigid parts

Adams

Gerbino

Whitney³

Proceedings of the 1999 IEEE International Symposium on Assembly and Task Planning (ISATP'99) (Cat. No.99TH8470)

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Application of Screw Theory to Constraint Analysis of Mechanical Assemblies Joined by Features

Adams

Whitney

1999

Journal of Mechanical Design

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Screw Theory is used to provide mathematical models of assembly features, allowing the determination of positioning constraints imposed on one part in an assembly by another part based on the geometry of the features that join them. Several feature types have been modeled, and it is easy to model new ones. A user of this theory is able to combine members of this set to join two parts and then determine whether or not the defined feature set over-, under-, or fully-constrains the location and orientation of the part. The ability to calculate the state of constraint of parts in an assembly is useful in supporting quantitative design of properly constrained assemblies in CAD systems. Locational over-constraint of parts can lead to assembleability problems or require deformation of parts in order to complete the assembly.

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Full Vehicle Variability Modeling

Cited by 6 publications

References 0 publications

Proper constraint as a design principle for assemblies

Proper constraint as a design principle for assemblies

Application of screw theory to motion analysis of assemblies of rigid parts

Application of Screw Theory to Constraint Analysis of Mechanical Assemblies Joined by Features

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