  The finite-time attitude synchronization problem is considered in this paper,
where the rotation of each rigid body is expressed using the axis-angle
representation. Two discontinuous and distributed controllers using the
vectorized signum function are proposed, which guarantee almost global and
local convergence, respectively. Filippov solutions and non-smooth analysis
techniques are adopted to handle the discontinuities. Sufficient conditions are
provided to guarantee finite-time convergence and boundedness of the solutions.
Simulation examples are provided to verify the performances of the control
protocols designed in this paper.
