  In this paper, formation control for reduced attitude is studied, in which
both stationary and rotating regular tetrahedron formation can be achieved and
are asymptotically stable under a large family of gain functions in the
control. Moreover, by further restriction on the control gain, almost global
stability of the stationary formation is obtained. In addition, the control
proposed is an intrinsic protocol that only uses relative information and does
not need to contain any information of the desired formation beforehand. The
constructed formation pattern is totally attributed to the geometric properties
of the space and the designed inter-agent connection topology. Besides, a novel
coordinates transformation is proposed to represent the relative reduced
attitudes in S^2, which is shown to be an efficient approach to reduced
attitude formation problems.
