Fixed-time Convergent Backstepping Sliding Mode Guidance Law with Impact Angle Constraint

A new guidance law considering the impact angle constraint, autopilot dynamics and fixed-time convergence is proposed. Firstly, the nonsingular terminal sliding mode control, fixed-time stability theory and backstepping control are used to design the guidance law. In the design process, a nonsingular terminal sliding mode surface with fixed-time convergence is designed. Based on the super-twisting algorithm and fixed-time stability theory, a fixed-time convergent sliding mode disturbance observer is designed to estimate the target maneuvering and other disturbances. A tracking differentiator is used to solve the differential expansion in the traditional backstepping control. Then, based on the Lyapunov stability theory, the fixed-time stability of the guidance law is proved, and the expression of convergence time is given. Finally, the effectiveness of the proposed guidance law is verified by simulation analysis. Compared with the existing guidance laws, the proposed guidance law has higher guidance precision and angle constraint accuracy, faster system convergence speed and less energy consumption.