Optimal sliding mode guidance law with height deviation and terminal impact angle constraints

To meet the requirement of terminal impact attitude angle constraint of UAV to enhance precision-guided, this paper combines the optimal guidance and the sliding mode control, selects the error as a switching function, and then designs an optimal sliding mode guidance law with terminal impact angle constraint, which satisfies well with Rubustness, two methods of calculating time-to-go were derived, one of which based on getting the length of the curved path, and the other of which based on getting the range over average velocity. Through mathematical simulations, the derived guidance law was tested under the put in conditions of different airspace (at low and high airspace) to attack stationary targets with different terminal impact attitude angles, for different gravity compensation Kg respectively; compared the above two methods and analyzed their influence on guidance performance. The simulation results show that the terminal guidance law designed in this paper can meet with the placement and predetermined impact attitude angles constraints for different targets, thus it also can achieve the best effect of damage for UAV.