Sufficient stability condition for hybrid position/force control

A sufficient condition for the kinematic stability of a robot hybrid position/force control scheme is defined. The test for the sufficient condition is a technique that uses only the kinematic information to determine system stability or to identify situations where possible stability problems may occur. The sufficient condition test is applied to an example, using the original hybrid position/force control scheme of J.J. Craig and M.H. Raibert (1979) and the corrected hybrid position/force control scheme proposed by W.D. Fisher and M.S. Mujtaba (1992). A root locus analysis showed the original hybrid control approach to be unstable. It is shown that the sufficient condition is also violated for this situation. In the corrected hybrid control approach, the sufficient condition is never violated for any manipulator and the same example is shown to be always stable. A root locus plot for the hybrid control approaches is included to confirm the results of the sufficient stability condition