Longitudinal guidance law with constraints on impact angle and control

A certain impact angle and the observation of the control constraint are desired when a land-attack-missile attacks a stationary ground target. To address this problem, a longitudinal guidance law with constraints on the impact angle and the control was presented. Based on nonlinear center of mass motion equations of the missile, a linear model for guidance law design was derived by coordinate transformation. The guidance problem was converted to a stabilization problem of a linear time-invariance(LTI) system with control saturation. To stabilize the LTI system, a low gain state feedback law was designed utilizing the parametric Lyapunov equation approach. And a longitudinal guidance law with a design parameter was derived. A method tuning the design parameter of the guidance law was proposed. By tuning the parameter online, sight angle converged to the desired impact angle in finite time. And the control constraint was observed during flight. Simulation results show that the guidance law is adaptive to various missions and has a potential for engineering applications.