The management of parallel-manipulator singularities using joint-coupling

Joint-coupling is introduced in the design and control of parallel manipulators for purposes of singularity management. The idea behind joint-coupling is to drive several joints with one single actuator by mechanical or electronic means, while preserving the mobility of the manipulator. Such joint-coupling can affect the condition of direct singularities of parallel manipulators through its coupling coefficients. As drivability of the end-effector is affected by the direct singularities, a nonlinear optimization method is proposed to determine the appropriate coupling coefficients according to a given set of task postures. The coupling coefficients obtained in this manner can shape the direct singularity loci of the manipulator to ensure a given set of manipulator postures (tasks) free from direct singularities. Examples are included to illustrate the concept of joint-coupling and singularity management.