Study On The Methods Of Tolerance Analysis And Design

Influenced by many factors, the component values always derivate from the nominal values in some degree. This may lead to the quality loss and yield reduction of product, even cause product functionality is sensitive to the circumstance of use extremely. The range between the upper and lower limits of the variation from the nominal values is called tolerance. The tolerance directly influences the functionality and costs of product. A tighter tolerance is normally preferred for product functionality; however, manufacturing cost usually increases due to the requirement of more rigorous operations. Contrarily, a loose tolerance is less costly; however, it may cause inferior quality. Therefore, it is necessary to study tolerance, and to make trade-off between quality and costs.The works in this dissertation focused on the study on the existed methods of tolerance analysis and design. Moreover, design centering also was a part content of the dissertation. In tolerance analysis, tolerance design or parameters design, it is required to approximate the feasible region of parameters, or to estimate the yield of product. Hence, some methods about region approximation and yield estimation were introduced in this dissertation.The author presented a new method of tolerance analysis. It based on a genetic algorithm with sharing technique. It could treat with not only a large scale problem, but also the problem with multi-performance functions. In the dissertation, the method was applied to the tolerance analysis of a directional coupler of 3mm rectangular waveguide. And the validity and feasibility of this method was tested by the results. In addition, the author presented a method that combined particle swarm algorithm with a method of region approximation. The method could deal with design centering for parameters with arbitrary statistical distributions. Compared with the literature's result, it existed some advantages.