Non-overconstrained 3-dof spherical parallel manipulators of type: 3-RCC, 3-CCR, 3-CRC

摘要

Non-overconstrained 3-dof spherical parallel manipulators of a structural type 3-RCC, 3-CCR, 3-CRC are introduced. The mechanism has three limbs that connect in parallel the moving platform to the fixed base. Each limb is an opened kinematic chain made of a sequence of one revolute pair R and two cylindrical pairs C. The orientation of the end-effector is obtained by actuating simultaneously the three limbs. A structural type analysis and synthesis, which is based on the algebraic properties of a Lie group of the displacement set, is employed to find the geometrical conditions for the assembly of these spherical parallel mechanisms and also the structurally singular configurations. Then an enumeration of the structural types is given and remarkable special cases of orientational mechanisms are also described, namely 3-HGR, 3-RGH and 3-HGH.