Abstract: Based on the spherical coordinates, the kinematics of the spherical five-bar mechanisms is described in a two-dimensional plane, which is constructed by the two rotational degrees of the spherical coordinates. The velocity equation and the analytical expression of the Jacobian matrix for spherical five-bar mechanisms with two degrees of freedom characteristics are deduced. The singularity configuration and dexterity of asymmetric spherical five-bar mechanisms are discussed based on Jacobian matrix of mechanisms. The distribution of singularity loci and dexterity curve for spherical five-bar mechanisms are drawn. The influence of structure pa-rameters on global condition index for asymmetric spherical five-bar mechanisms is studied. The results show that, based on the spherical coordinates, the velocity equation and the Jacobian matrix can be conveniently created, and the distribution of singularity loci and dexterity curve for spherical five-bar mechanisms can be effectively described.

Key words: Dexterity, Global conditioning index, Singularity loci, Spherical five-bar mechanisms