Graspless manipulation is to manipulate objects without grasping. The graspless methods (pushing, tumbling, etc.) enable robots to achieve manipulation goal with the lighter workload and simpler mechanism than conventional pick-and-place. Graspless manipulation, however, has difficulties in planning. It is very time-consuming to plan a general graspless manipulation problem, because it requires not only geometrical analysis but also complicated mechanical analysis including friction. To reduce the load of computation, we adopt a two-step approach: 1) construction and simplification of contact-state network at geometry level, and 2) planning of manipulation at mechanics level. In this paper, we focus the latter, and propose an algorithm for planning of planar graspless manipulation. It generates digraphs that represent C-Subspaces for all the contact states, and unites them into one big graph, which we call “manipulation-feasibility graph.” Manipulation plan can be obtained by searching the graph. This algorithm is implemented for graspless manipulation by multiple robot fingers, and planned results are shown.
