Cooperating multiple robots may experience slips between their end-effectors and the object when making no rigid grasps, as is the case of manipulating fingers. Consequently, these slips make the robotic system unsuccessful in executing a job properly and can even cause a failure of control. Contact-point slips can be avoided by defining multiple constraints on grasping forces and usable work- space, but these constraints limit the utilization of a robotic system. The researchers working on finger grasps and multiple robots cooperation with contact have alwavs been assuming no slips at the contact points. However, in normal practice, one has to encounter this problem. Hence, this paper has talcen this contact-point slip problem as its main topic and theme of work. Consequently, the slip phenome- non is analyzed thoroughly and then generalized for a multiple robot system manipulating a geometrically regulan shaped object. Different slip configurations are introduced and methods for their detection are proposed. This detection does not consider dedicated sensors neither for the object's posture nor for the slip detection. It, rather, utilizes only the finger-tip position information usually available from the kinematics based on very common sensors available with the manipulator. Utilizing the proposed methodology, it is possible to detect the end-point slips in most of the cases and realize an exact task execution and stability of control, with a minimum number of sensors.
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