Fully-isotropic parallel robots with four degrees of freedom T2R2-type

The paper presents singularity-free fully-isotropic parallel manipulators (PMs) with four degrees of freedom T2R2-type. The mobile platform has two independent translations (T2) and two rotations (R2). A method is proposed for structural synthesis of fully-isotropic T2R2-type PMs based on the theory of linear transformations. A one-to-one correspondence exists between the actuated joint velocity space and the external velocity space of the moving platform. The Jacobian matrix mapping the two vector spaces of fully-isotropic T2R2-type PMs presented in this paper is the identity 4×4 matrix throughout the entire workspace. The condition number and the determinant of the Jacobian matrix being equal to one, the manipulator performs very well with regard to force and motion transmission capabilities. As far as we are aware, this paper presents for the first time in the literature solutions of singularity-free fully-isotropic PMs with four degrees of freedom T2R2-type.