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Este trabalho aborda os conceitos necessários para o estudo de tolerâncias dimensionais de um conjunto mecânico e propõe um método eficaz para a especificação de tolerâncias na fase de detalhamento do projeto de um produto, através de um algoritmo de otimização baseado em custos de produção. Conceitos do custo da perda de qualidade desenvolvidos por Genichi Taguchi são também aplicados para a especificação de restrições funcionais, que visam garantir um determinado nível de qualidade em função de valores especificados para critérios funcionais. Comentários e comparações com outros trabalhos de otimização de tolerâncias dimensionais são também realizados, através dos quais podem ser observadas características específicas no método proposto. Um exemplo de aplicação é apresentado através do estudo de caso baseado em um projeto de sistema de transmissão de potência por correias a equipamentos periféricos de um motor de combustão interna. Os resultados da aplicação do algoritmo de otimização são comparados aos de métodos convencionais de síntese de tolerâncias, mostrando sua eficácia. / This work approaches the concepts needed to the study of dimensional tolerances of a mechanical assembly and proposes an effective method for specifying tolerances in the detailing phase of product design, by means of an optimization algorithm based on manufacturing costs. Concepts of quality loss developed by Genichi Taguchi are also applied for specifying functional constraints, which aim to assure an adequate quality level regarding specified values of functional criteria. Comments and comparisons with other dimensional tolerances optimization works are also made, through which specific features of the proposed method can be observed. An application example of the method is presented through a case study based on a belt power transmission system to ancillary equipment of an internal combustion engine. Results of application of the optimization algorithm are compared with the ones of conventional tolerance synthesis methods, showing their effectiveness.

Este trabalho aborda os conceitos necessários para o estudo de tolerâncias dimensionais de um conjunto mecânico e propõe um método eficaz para a especificação de tolerâncias na fase de detalhamento do projeto de um produto, através de um algoritmo de otimização baseado em custos de produção. Conceitos do custo da perda de qualidade desenvolvidos por Genichi Taguchi são também aplicados para a especificação de restrições funcionais, que visam garantir um determinado nível de qualidade em função de valores especificados para critérios funcionais. Comentários e comparações com outros trabalhos de otimização de tolerâncias dimensionais são também realizados, através dos quais podem ser observadas características específicas no método proposto. Um exemplo de aplicação é apresentado através do estudo de caso baseado em um projeto de sistema de transmissão de potência por correias a equipamentos periféricos de um motor de combustão interna. Os resultados da aplicação do algoritmo de otimização são comparados aos de métodos convencionais de síntese de tolerâncias, mostrando sua eficácia. / This work approaches the concepts needed to the study of dimensional tolerances of a mechanical assembly and proposes an effective method for specifying tolerances in the detailing phase of product design, by means of an optimization algorithm based on manufacturing costs. Concepts of quality loss developed by Genichi Taguchi are also applied for specifying functional constraints, which aim to assure an adequate quality level regarding specified values of functional criteria. Comments and comparisons with other dimensional tolerances optimization works are also made, through which specific features of the proposed method can be observed. An application example of the method is presented through a case study based on a belt power transmission system to ancillary equipment of an internal combustion engine. Results of application of the optimization algorithm are compared with the ones of conventional tolerance synthesis methods, showing their effectiveness.

An analysis of the previous method for testing tolerances of noxious weed seeds was performed. Problems of the current techniques were discussed, and the solution to these problems was given. A new technique of testing through the sequential test ratio was developed, and results examined. The sequential test was found to be useful enough to include the use of it in determining tolerances for noxious weed seeds. This study did show that the use of sequential tests does have excellent potential and flexibility as a statistical tool for the tolerances of noxious weed seeds. (75 pages)

The application of a sequential test, the sequential probability ratio test, for the tolerances of noxious weed seeds is studied. It is proved that the sequential test can give a similar power curve to that of the current fixed sample test if the test parameters are properly chosen. The average sample size required by a sequential test, in general, is smaller than that of the existing test. However, in some cases it requires relatively a larger sample than current test. As a solution to the problem a method of truncation is considered. A kind of mixed procedure is suggested. This procedure gives almost an identical power curve to the standard one with great savings in sample size. The sample size is always less than that of the current test procedure.

Haglund Industri är ett företag specialiserat på tillverkning av kylar och frysar. Företaget står dock inför utmaningar med frysningsprocessen av en specifik typ av produkt. Varmluftsläckage mellan dörrens karm och magnetremsa resulterar i isbildning som påverkar produktkvalitet och funktion. Problemet uppstår inkonsekvent i specifika produkter och observeras oftast under perioder med hög luftfuktighet. Detta problem påverkar slutskedet av produktionsprocessen, vilket leder till slöseri med tid och energi. Därför behövs en optimeringsmetod för att ta itu med problemet och förbättra produktkvaliteten. Projektet syftar till att optimera frysprocessen och minimera isbildning genom att analysera grundorsaken till problemet och utforma en lämplig lösning. Optimeringsprocessen kommer att beakta produktionslinjen, använda material och miljöfaktorer. Resultaten av detta projekt förväntas förbättra produktkvaliteten, minska produktionskostnaderna och öka kundnöjdheten. Mättningar och simuleringar gjorda för denna fallstudie visar hur små skillnader i tillverkning kan påverka slutproduktens funktioner. Med hjälp av olika hjälpmedel och strategier i produktionen kan dessa observeras. / Haglund Industries is a company specializing in the production of frozen food products. However, the company is facing challenges with the freezing process of a specific type of product. Warm air leakage between the door's frame and magnetic strip results in ice formation that affects product quality and function. The problem occurs inconsistently in specific products and is mostly observed during high humidity periods. This problem affects the final stages of the production process, causing wasted time and energy. Therefore, an optimization approach is needed to address the issue and improve product quality. The project aims to optimize the freezing process and minimize ice formation by analyzing the root cause of the problem and designing a suitable solution. The optimization process will consider the production line, materials used, and environmental factors. The results of this project are expected to improve product quality, reduce production costs, and increase customer satisfaction. Measurements and simulations made for this case study show how small differences in manufacturing can affect the functions of the final product. With the help of the various aids and strategies in production, these can be observed.

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<p> Many safety-critical software applications are hard real-time systems. They have stringent timing requirements that have to be met. We present descriptions of timing behaviors that include precise definitions as well as analysis of how functional timing requirements (FTRs) interact with performance timing requirements (PTRs), and how these concepts can be used by software designers. The definitions explicitly show how to specify timing requirements with tolerances on time durations. </p> <p> This thesis shows the importance of specifying both FTRs and PTRs, by revealing the fact that their interaction directly determines the final implementability of real-time systems. By studying this interaction under three environmental assumptions, we find that the implementability results of the timing properties are different in each environment, but they are closely related. The results allow us to predict the system's implementability without developing or verifying the actual implementation. This also shows that we can sometimes significantly reduce the sampling frequency on the target platform, and still implement the timing requirement correctly. </p> <p> We present a component-based approach to formalizing common timing requirements and provide a pre-verified implementation of one of these requirements. The verification is performed using the theorem proving tool PVS. This allows domain experts to specify the tolerance in each individual timing requirement precisely. The pre-verified implementation of a timing requirement is demonstrated by applying the method in two examples. These examples show that both the design and verification effort are reduced significantly using a pre-verified template. </p> <p> A primary focus of this thesis is on how to include tolerances on timing durations in the specification, implementation and verification of timing behaviors in hard real-time applications. </p> / Thesis / Doctor of Philosophy (PhD)

Few aircraft engine manufacturers are able to consistently achieve high levels of performance reliability in newly manufactured engines. Much of the variation in performance reliability is due to the combined effect of tolerances of key engine components, including tip clearances of rotating components and flow areas in turbine nozzles. This research presents system analysis methods for determining the maximum possible tolerances of these key components that will allow a turbine engine to pass a number of specified performance constraints at a selected level of reliability. Through the combined use of a state-of-the-art engine performance code, component clearance loss models, and stochastic simulations, regions of feasible design space can be explored that allow for a pre-determined level of engine reliability. As expected, constraints such as spool speed and fuel consumption that are highly sensitive to certain component tolerances can significantly limit the feasible design space of the component in question. Discussed are methods for determining the bounds of any components feasible design space and for selecting the most economical combinations of component tolerances. Unique to this research is the method that determines the tolerances of engine components as a system while maintaining the geometric constraints of individual components. The methods presented in this work allow for any number of component tolerances to be varied or held fixed while providing solutions that satisfy all performance criteria. The algorithms presented in this research also allow for an individual specification of reliability on any number of performance parameters and geometric constraints. This work also serves as a foundation for an even larger algorithm that can include stochastic simulations and reliability prediction of an engine over its entire life cycle. By incorporating information such as time dependent performance data, known mission profiles, and the influence of maintenance into the component models, it would be possible to predict the reliability of an engine over time. Ultimately, a time-variant simulation such as this could help predict the timing and levels of maintenance that will maximize the life of an engine for a minimum cost. / Master of Science

Given that achieving nominal (all dimensions are theoretically perfect) geometry is challenging during building construction, understanding and anticipating sources of geometric variation through tolerances modeling and allocation is critical. However, existing building modeling environments lack the ability to support coordinated, incremental and systematic specification of manufacturing and construction requirements. This issue becomes evident when adding multi-material systems produced off site by different vendors during building erection. Current practices to improve this situation include costly and time-consuming operations that challenge the relationship among the stakeholders of a project. As one means to overcome this issue, this research proposes the development of a knowledge-aided modeling framework that integrates a parametric CAD tool with a system modeling application to assess variability in building construction. The CAD tool provides robust geometric modeling capabilities, while System Modeling allows for the specification of feature-based manufacturing requirements aligned with construction standards and construction processes know-how. The system facilitates the identification of conflicting interactions between tolerances and manufacturing specifications of building material systems. The expected contributions of this project are the representation of manufacturing knowledge and tolerances interaction across off-site building subsystems to identify conflicting manufacturing requirements and minimize costly construction errors. The proposed approach will store and allocate manufacturing knowledge as Model-Based Systems Engineering (MBSE) design specifications for both single and multiple material systems. Also, as new techniques in building design and construction are beginning to overlap with engineering methods and standards (e.g. in-factory prefabrication), this project seeks to create collaborative scenarios between MBSE and Building Information Modeling (BIM) based on parametric, simultaneous, software integration to reduce human-to-data translation errors, improving model consistency among domains. Important sub-stages of this project include the comprehensive review of modeling and allocation of tolerances and geometric deviations in design, construction and engineering; an approach for model integration among System Engineering models, mathematical engines and BIM (CAD) models; and finally, a demonstration computational implementation of a System-level tolerances modeling and allocation approach.