Real and virtual coarse-fine robot bracing strategies for precision assembly

Previous work on coarse-fine robots has emphasized improved positioning resolution or improved compliant behavior. The authors stress the use of the coarse-fine system´s redundant degrees of freedom for bracing of either the coarse or the fine manipulator to execute an assembly task reliably. They refer to real bracing if the constraining forces and torques are supplied by mechanical means, and to virtual bracing if they are supplied by a control system. An application of the coarse-fine robot bracing approach to precision laminate registration and stacking for electronic packaging is presented. Results show that assembly errors of only a few microns can be readily obtained, approximately an order of magnitude improvement over the unbraced coarse-fine case, and nearly two orders of magnitude better than those attainable by coarse manipulation alone