Hunt singularity determination for Gough-Stewart platform

Geometry parameters and lengths of legs often have close relations with the singularity of a Gough-Stewart platform. When these parameters are improperly selected, the platform may have hunt singularities. The relations among the geometrical parameters and the leg lengths when in hunt singularity for 3-3, 6-3, 6-6 Gough-Stewart are derived according to their geometrical constrains. The obtained relations can be used as a geometrical criterions, for a Gough-Stewart platform with given geometrical parameters, to determine if the mechanism may have or close to Hunt singularity in its workspace. Two experiments are performed, which validates the hunt singularity criterions.