Three-dimensional low-order fixed-time integrated guidance and control for STT missile with strap-down seeker.

• A new low-order integrated guidance and control model is proposed. • The fixed time integrated guidance and control scheme and related stability analysis. • The angle constraints of body line-of-sight and roll are considered. • The tracking performance for body line-of-sight angle is improved by a long way. Strap-down seeker is rigidly fixed onto the missile body, which results in detection information being coupled to the missile's attitude and having a narrow field-of-view (FOV). During the terminal guidance flight, attitude adjustment of the missile may lose the target's lock and reduce interception accuracy. Therefore, this paper investigates three-dimensional integrated guidance and control (IGC) under the constraints of the FOV and roll angle for skid-to-turn (STT) missile with strap-down seeker. A new low-order IGC model is constructed by establishing a second-order model of body line-of-sight (BLOS) angle based on strap-down decoupling theory and combining it with the second-order roll angle equation. Furthermore, a low-order fixed-time IGC scheme is developed using the integral barrier Lyapunov function (iBLF) to limit BLOS and roll angles. Fixed-time filter, which avoids the "complexity explosion" caused by conventional back-stepping technique, is utilized for obtaining virtual control command and its derivative. A fixed-time disturbance observer is introduced to compensate for the lumped disturbance. According to Lyapunov stability theory, it is proven that the proposed IGC scheme can make the closed-loop system converge within a fixed time. Finally, the effectiveness and robustness of the IGC scheme are verified by various numerical simulations. [ABSTRACT FROM AUTHOR]