Dynamic inversion three-dimensional guidance law for impact time control

In order to hit a stationary target at a designated time, a missile guidance system was developed with an augmented proportional navigation guidance (APNG) system in the pitch channel, and a maneuver control system in the yaw channel. Maneuver control was able to adjust the impact time to a designated value. Time-to-go error was introduced, which is the difference between actual time-to-impact and the designated time-to-impact. The current time-to-go was calculated as current range-to-go over velocity. According to the kinematics of missile-to-target, current range-to-go can be indirectly altered by the yaw control command through the yaw lead angle. This means that time-to-go error could also be indirectly controlled by this command. For the proposed two part control system, the low speed subsystem and the fast one were designed using the time-scale separation method. Two nonlinear dynamic inversion controllers were designed for the two subsystems and a yaw maneuver control command was provided. Simulation results showed that this guidance approach allowed time-to-go errors to be ultimately reduced to zero, with missile impact time accurately controlled. The final phase of flight can still be a straight trajectory.