Soft landing guidance law for UUV bottom-sitting task

In order to achieve a smooth and non-overshoot performance for risk of striking the seabed in UUV bottom-sitting task, a soft landing guidance law is presented, which is inspired from the corresponding concept in aerospace science. The guidance law is a polynomial function with respect to time, and the desired vertical position, velocity and acceleration of UUV are determined. In particular, the necessary and sufficient condition for rationality of the guidance law is explained and proved. Theoretical analysis indicates that, with this method, the energy consumption of UUV only depends on the initial velocity and the final velocity, and thus a trade-off between time consumption and energy consumption could be achieved when setting desired velocities. Simulation results show that the UUV moves towards the destination at the determined velocity and acceleration by the proposed guidance law without overshoot, and the acceleration approaches zero according with the concept of soft landing. Safety, rationality, and effectiveness of the proposed guidance law are demonstrated.