Crank conditions and rotatability of 3-<Emphasis Type="Italic">RRR</Emphasis> planar parallel mechanisms

This paper investigates the rotatability of planar parallel mechanisms by revealing the crank conditions that relate to link parameters. The paper extends the theorem of assemblability and the rotatability criterion and applies these criteria to parallel mechanisms in investigating the crank conditions of a parallel mechanism, leading to classification of three types of crank existing conditions including three-crank’s, six-crank’s and nine-crank’s of 3-RRR planar parallel mechanisms. The results are summarized as constraint conditions in relation with link parameters with a concluding table and case studies.