On the infinitesimal motion of a parallel manipulator in singular configurations

A s serial robots parallel manipulator may be in a singular configuration. In these configurations the inverse jacobian matrix is singular and the end-effector may move although the articular velocities are equal to zero. The determination of the loci of these singular configurations is an important problem because in such configuration the articular forces may go to infinity and yield important mechanical damages. In a preceding paper we have proposed a geometrical approach for finding the singular configurations loci. We consider here a specific parallel manipulator and find what are the features of the infinitesimal motions associated to each of the singular configurations.