Let $SE\left(3\right)$ be the Lie group of all Euclidean motions in the Euclidean space $E_3$, let $se\left(3\right)$ be its Lie algebra and $s{e}^{*}\left(3\right)$ the space dual to $se\left(3\right)$. This paper deals with structures of the subspaces of $s{e}^{*}\left(3\right)$ which are formed by all the forces whose power exerted on the robot effector is zero.

A multi-robot environment with a STRIPS representation is considered. Under some assumptions such problems can be modelled as a STRIPS language (for instance, a Block World environment) with one initial state and a disjunction of goal states. If the STRIPS planning problem is invertible, then it is possible to apply the machinery for planning in the presence of incomplete information to solve the inverted problem and then to find a solution to the original problem. In the paper a planning algorithm...