Controllability Issues of Robots near Singular Configurations
The problems of robot motion in the task space, such as Cartesian control and force control are widely studied. Here the relation between robot singularities and the concept of controllability is important. Simple examples contradict some statements usually made about the motion of robots in singular configurations. A robot may be controlled in an arbitrary direction from a singular configuration if the velocity profiles are shaped in a proper way. Nonlinear controllability introduced by differential geometry actually suggests lack of controllability at a singular point. Therefore the observations on possible motions made in this paper opens a number of questions. Frther, the results may be of immediate and significant relevance to path programming and to path following.
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