Closed-form resolution of the direct kinematics of parallel manipulators using extra sensors data

In the most general case the measurement of the link lengths of a six-degree-of-freedom parallel manipulator is not sufficient to determine the actual unique posture of its platform. It is shown that by adding four sensors on the passive joints, a unique closed-form solution of the posture of the end-effector can be obtained for the most general case. It is shown that three sensors are sufficient for a particular mechanical architecture