Interval Approach for the Modeling of Tolerances and Clearances in Mechanism Analysis

It is important to conduct error analysis of assemblies in order to ensure that the manufactured parts satisfy the design specifications. Traditionally, mechanical tolerances and clearances are modeled as random variables and the analysis is conducted using probabilistic methods. In this work, a new approach, based on interval analysis, is presented for the modeling and analysis of tolerances and clearances. The basic procedure of interval analysis involving solution of simultaneous nonlinear equations is described. The application of the approach in the fuzzy error analysis of planar and spatial mechanisms is also outlined. The treatment of the tolerances and clearances of the mechanism as interval numbers leads to a better and a more realistic estimation of the analysis results. Numerical examples are presented to illustrate the computational procedures. The results of the interval analysis, although philosophically different, are compared with those given by the probabilistic method for comparable input data; the differences found in the two sets of results are explained in terms of the basic characteristics of the two methods. This work denotes the first application of interval methods for the modeling of tolerances and clearances and the fuzzy error analysis of mechanisms.