Anylysis And Synthesis Of Elastic Linkages With Joint Clearances Based On Robust Design

Linkages, which is widely used in many fields of machinery, can never generate the desired function or path exactly over the entire range of operation because of its deviations which consist of inherent structural error of ideal linkages and mechanical errors caused by manufacturing tolerances on the dimension, clearances in joint and elasticity of links. Usually, the tolerances and the clearances are probabilistic variables, so the outputs of linkages are also probabilistic ones.Traditionally, the error analysis of linkages is carried out by exact techniques and the synthesis is carried out by optimization approachs, both processes take tolerances and clearances as deterministic variables. The deterministic synthesis can produce a very small structural error, but the tolerances, clearances and elasticity maybe result in the actual outputs of linkages deviating from the desired ones, as a result, a feasible linkages in theory is eventually unfeasible in practice. Therefore, the mechanical errors should be considered as probabilistic variables in the analysis and synthesis of a linkage, which is called robust analysis and synthesis of linkage.In this dissertation, the analytical models of kinematics and dynamics are constructed, in which manufacturing tolerances on the dimensions, clearances in joints and elasticity of links are taken into account. The synthetical models whose objective function is output precision or cost of manufacturing are presented. A four-bar path generator is selected for numerical illustration.The results of the robust analysis and synthesis are compared with those of the traditional deterministic analysis and synthesis.