Exploiting the Kinematic Redundancy of a (6 + 3) Degrees-of-Freedom Parallel Mechanism

This paper presents methods to exploit the redundancy of a kinematically redundant spatial parallel mechanism with three redundant DOFs. The architecture of the mechanism is similar to the well-known Gough–Stewart (GS) platform and it retains its advantages, i.e., the members connecting the base to the moving platform are only subjected to tensile/compressive loads. The kinematic redundancy is exploited to avoid singularities and extend the rotational workspace. The architecture is described and the associated kinematic relationships are presented. Solutions for the inverse kinematics are given, as well as strategies to take into account the limitations of the mechanism such as mechanical interferences and velocity limits of the actuators while controlling the redundant degrees-of-freedom.