Study on transmission angle and singularity in 5R planar mechanism

Transmission angle is one of the important design criteria to be considered for the effective force and motion transmission of a mechanism. Poor transmission angles are detrimental to the performance of a mechanism as they exaggerate the effect of friction and clearances. In addition, the torque required to overcome external load tends to increase and the required torque capacity of the drive increases unnecessarily. The singularity positions in a workspace are closely related to the transmission angle of the manipulator configuration. For achieving a large singularity-free area, the configuration dimension needs to be increased. Even though the objective is to design a compact five-bar planar mechanism, the link dimensions are likely to increase to some extent while achieving the desired transmission angles. This paper deals with estimating the singularity-free area of a five-bar mechanism by considering variations in transmission angles for different link lengths. The generalized methodology presented in this work demonstrates the estimation of singularity-free largest reachable area and link proportions at which intra-link transmission angles are confined. A dimensionless singularity-free workspace index is proposed to quantify performance at various transmission angles.