Mobility analysis of a 3-5R parallel mechanism family

Mobility analysis of a 3-5R parallel mechanism family whose limb consists of a 2R and a 3R parallel subchains is performed by the aid of screw theory. A mobility criterion applicable to such 3-leg parallel mechanisms in which each kinemaic chain contains five kinematic pairs is proposed. It is shown that under different structural conditions, the 3-5R parallel mechanism can have 3, 4, or 5 DOF (degrees of freedom). The structural conditions which guarantee the full-cycle mobility are analyzed. The analysis and the method presented in this paper will be helpful in using such a 3-5R parallel mechanism family and introduce new insights into the mobility analysis of parallel mechanisms.