Topology Synthesis and Classification of Low-Mobility Parallel Mechanisms

Topology synthesis of low-mobility parallel mechanisms is an important direction of mechanism research. At present, various systematic methods for topology synthesis have been proposed, and large numbers of new mechanisms that satisfy the motion requirements have been synthesized through step-by-step deducing. However, some fundamental problems are ignored. In this paper, some significant synthesis methods are compared from the aspects of the description of output character, limb structure synthesis and geometrical relationship between limbs. The commonly existent problems are analyzed, including the strict description of the output character of the moving platform and the instantaneous mechanisms in the process of topology synthesis. The limitation of existent methods is also indicated. Moreover, a classifying method for low-mobility parallel mechanisms from the viewpoint of topology synthesis is proposed. This classification has guiding effect for synthesis, analysis and application of parallel mechanisms.