Sensitivity synthesis of four bar linkages for three and four positions.

摘要

The effect of manufacturing errors and clearances on the kinematic performance of linkages has been recently the subject of much analysis work, most of which was of a statistical nature.; In this work, the problem of kinematic errors due to manufacturing tolerances and clearances is approached from a more profound viewpoint. Instead of analyzing errors as they occur in each particular linkage, mechanism sensitivity to dimensional variations of links is used as a measure of the mechanism's ability to achieve the motion for which it was originally designed. Sensitivity variations with the mechanism's design parameters are investigated in the particular case of planar four-bar linkages in two solutions spaces. The first solution space is the three dimensional space consisting of the four bar linkage proportions. Sensitivity maps obtained in different plane sections of this space make it possible to discriminate between different four bar linkages on the basis of sensitivity and predict the maximum allowable link tolerances to obtain a certain accuracy on the output. The second space is the linkage design plane itself where the design parameters are the locations of the moving or ground pivots. Again here, sensitivity maps are laid out to allow the designer to optimize sensitivity. Both cases of three positions and four positions are considered.