  To enable multiple missiles to attack a maneuvering target simultaneously,
fixed-time distributed cooperative guidance laws are proposed in this paper.
Here, we present a novel fixed-time fast nonsingular terminal sliding mode
surface (FNTSMS). In particular, the sliding mode surface not only avoids
singularities but also has the characteristic of a settling time boundary
regardless of the initial conditions. Based on the FNTSMS, we have developed a
distributed guidance law, which has the characteristic of fixed-time
convergence. The guidance law achieves the consensus of range-to-go, relative
velocity along and perpendicular to the line of sight (LOS) direction to
realize the simultaneous attack. In addition, a saturation function is
introduced to avoid the chattering problem caused by the commonly used sign
function. Furthermore, the distributed cooperative guidance law with
communication failure is considered and proved theoretically, which shows that
the proposed guidance law has excellent performance. Finally, the simulation
results verify the performance of the distributed guidance law and its
robustness against communication topology mutations, and explain the phenomenon
in detail.
