Influence of tolerances on error estimation in P3R and 4R planar mechanisms

Four-bar linkages form a primitive configuration of many mechanisms. The output of these mechanisms deviates from the desired one due to many factors including tolerance on links. For satisfactory application, the mechanism performance needs to be characterized. This article presents a treatment on the synthesis and analysis of linear-input P3R (1-Prismatic, 3-Revolute) and rotary-input 4R (4-Revolute) planar mechanism configurations, and the estimation of mechanical error under the influence of link tolerances. A detailed methodology is presented for error estimation as part of performance analysis for each mechanism. As an illustrative case, mechanisms are considered to operate under identical output generation conditions and comparative performance evaluation is carried out. Effect of link proportion is studied to investigate the mechanism behavior related to mechanical error. Comparison of error provides the basis for selecting the mechanism that gives better performance. The proposed methodology demonstrates generalized characterization of the mechanical error sources with validation.