Design of nonlinear observer for strap-down missile guidance law via sliding mode differentiator and extended state observer

A guidance observer for observer-based guidance law is designed for a missile equipped with strap-down seeker. Practical guidance system requires a precise estimation algorithm to obtain the target information from the seeker. In the considerations of parameter estimation, fast-convergence and robustness with respect to the noise should be guaranteed. To design a guidance filter, a delayed look-angle observed from the strap-down seeker is compensated in the LOS (Line-of-sight) reconstruction, and nonlinear observer is applied to estimate look-angle and the LOS rate using extended state observer and sliding-mode differentiator. Based on the nonlinear observer, an observer-based guidance law is applied to a strap-down seeker-based missile. Numerical simulation is performed to demonstrate the performance of the proposed observer and the observer-based guidance system.