A novel approach for geometric accuracy synthesis of three degrees of freedom parallel mechanism

Hybrid robots featuring a 1T2R parallel mechanism as their primary structure play a crucial role in on-site machining of large components. The end accuracy of these robots is a pivotal performance factor, determining their capability to fulfill the stringent requirements of on-site machining. This paper presents a novel approach for the accuracy synthesis, where the accuracy conformity, defined by the allowable accuracy, is the constraint and the manufacturing cost is the optimization objective. The methodology accounts for the workspace size employed in actual machining, preventing an increase in manufacturing cost caused by ensuring the accuracy within non-machining workspace. Using the newly developed R(RPS&RP)&2-UPS parallel mechanism as an example, the paper extensively details the accuracy modeling, sensitivity analysis, and accuracy synthesis. Moreover, the variations among error sources, allowable accuracy thresholds, and accuracy conformity are comprehensively analyzed. Finally, three sets of error source values are determined to achieve a balance between the cost-effectiveness and the corresponding requirements of accuracy conformity.