A kinematically redundant (6+2)-degree-of-freedom four-legged parallel manipulator

This paper introduces TETRArm, a four-legged parallel manipulator endowed with kinematic redundancy. The redundancy of the robot is leveraged by incorporating two internal degrees of freedom into the moving platform of a non-redundant spatial parallel manipulator. This contribution demonstrates how a generalized coordinate can function identically in both inverse and forward instantaneous kinematics. Due to the complexity of the resulting equations, the forward position analysis is solved numerically. The instantaneous kinematics of the robot is examined using screw theory. In that concern, the velocity and acceleration expressions for the eight-degree-of-freedom parallel manipulator are systematically derived through the cancellation of passive joint rates via the Klein form. Numerical applications complement the theoretical findings.