Terminal guidance method with multiple constraints in the presence of disturbances and control saturation

In the terminal guidance phase, a vehicle is subject to various disturbances, such as modeling error, wind, and target movement. Moreover, the seeker's field-of-view, attack angle, and impact angle are constrained. To guide the vehicle under these conditions, a guidance method under multiple constraints and disturbances is proposed. The guidance problem is transformed to a stabilization problem of a system with control saturation and disturbance. A low-gain state feedback law with disturbance compensation is designed to stabilize the system, and a linear extended state observer is used to estimate the disturbance. Then, a terminal guidance law is derived. Using Lambert W function, effects of the guidance law parameters on the convergence of the line-of-sight angle are investigated. Moreover, an adaptive parameter regulation method is presented to adjust the guidance law parameters online. The proposed guidance method is demonstrated by numerical simulation under various disturbances. All the constraints are observed and high guidance precision is achieved.