Mechanical error of a four-bar linkage coupler curve

Mechanical error in the coupler curve of a four-bar linkage is estimated in terms of translational and rotational components of the position error. Cognate linkages, theoretically capable of generating identical coupler curves, are seen to have different sensitivity to the errors in the link lengths. Numerical results are included to identify the most critical link of a given mechanism. The maximum translational and rotational errors are found to be proportional to the errors in link lenght when all the links have the same but small error