This paper proposes a novel task description for redundant systems as an extension of oblique coordinate control. Orthogonality of tasks are not necessary and interference between a task space and a null space is precisely described in off-diagonal parameters of "task mass matrix" in this method. Dynamics of the null space is also considered with its basic variables. In order to decouple the spaces, a null space regulator is proposed. Conventionally, this kind of decoupling is given by selecting a mass matrix as a weighting matrix of the pseudo inverse. On the other hand, arbitrary weighting matrices can be selected in our approach. Some comments for sub tasks are given. In a short word, " there is few need of sub tasks". Validity of the proposed method is analyzed and is confirmed by experiments.
ASJC Scopus subject areas