The Design of the Variable Coefficient Sliding Mode Guidance Law with Multi-angle Constraints

To address the problem of cruise missile attacks on ground targets with large impact angles, traditional trajectory shaping guidance laws and impact angle constrained sliding mode guidance laws often result in the line of sight angle exceeding the seeker's field of view angle, making it challenging to balance the relationship between terminal trajectory pull-up height, seeker's field of view, and terminal impact angle. This causes the problem that the seeker cannot capture the target within the recognition distance or loses it after catching it. To address these challenges, we propose a multi-angle constrained sliding mode guidance method that satisfies the constraints on the seeker's field of view angle, impact angle, and terminal attack angle. By expanding the field of view angle and terminal attack angle in the sliding mode surface equation, overload commands are derived, and the reachability and convergence of the sliding mode are demonstrated. By analyzing the correlation between the coefficients of each constraint term and the range of the seeker's frame angle, a variable coefficient sliding mode guidance law is proposed, which allows for the adjustment of the guidance law coefficients based on the actual trajectory requirements to accommodate various strike missions. The comparison of simulation results proves that this method can adjust the guidance law coefficient according to the seeker index, effectively reducing the utilization of the seeker's field of view. It also helps maintain the impact angle and angle of attack within a reasonable range.