A DIRECT DETERMINATION OF THE INSTANTANEOUS KINEMATICS OF FULLY PARALLEL ROBOT MANIPULATORS

Screw theory is applied to the study of the instantaneous kinematics of the end-effector platform of fully parallel robot type devices. The instantaneous motion of the end-effector is expressed directly in terms of the twists of the input-actuated joints and it is demonstrated that the twist representing the instantaneous motion of the end-effector platform is equal to the sum of its partial twists. A partial twist is defined as the twist representing the instantaneous motion of the end-effector when all but one of the input actuators are locked. The analysis presented forms a proper basis for the study of special configurations of parallel type devices.