A Modified Three-Dimensional Sliding Mode Guidance Law with Impact Angle Constraint

This paper proposes a modified three-dimensional (3D) impact angle constrained guidance law based on a sliding mode control approach. Firstly, sliding mode surfaces with respect to impact angles are designed in both yaw and pitch planes considering the 3D guidance characteristics. Then, a parameter adaptive power reaching law is designed based on Lyapunov stability theory. Furthermore, a modified sliding mode impact angle constrained guidance (SMIACG) law is deduced from the 3D guidance model via using the proposed sliding mode control technique. The modified 3D SMIACG law ensures finite-time convergence of the impact angle error rather than asymptotic or exponential convergence. Compared with existing 3D impact angle constrained guidance (IACG) methods, the deduced SMIACG law requires less maximum normal overload and less normal overload near the hit point while satisfying hitting accuracy. The trajectory is relatively straight in the final guidance process. Besides, the proposed guidance law processes a simple overall form without any switching strategy and only one parameter needs to be set which facilitates the practical application. Finally, various simulations under different scenarios are conducted to verify the properties and effectiveness of the modified SMIACG with further parameter setting suggestions.