ON SINGULAR TIME-OPTIMAL CONTROL ALONG SPECIFIED PATHS

This paper presents a general necessary condition for singular time op timal control of robotic manipulation moving along specified paths. Ea rly work [1], [7] ignored the issue of singular control, assuming bang -bang acceleration along the path. Recent work [6] has shown that the time optimal control can be singular if one of the equations of motion reduces to a velocity constraint. This paper derives a more general n ecessary condition for singular control. It is also proven that singul ar control cannot exist if the set of admissible controls is strictly convex, as is demonstrated for a two-link planar manipulator with elli ptical actuator constraints.