NONLINEAR DISTURBANCE OBSERVER-BASED FAST TERMINAL SLIDING MODE GUIDANCE LAW WITH IMPACT ANGLE CONSTRAINTS

摘要

For the terminal guidance problem of tactical missiles intercepting maneuvering targets with impact angle constraints, a fast terminal sliding mode guidance law without any singularity is proposed based on a nonlinear disturbance observer. Considering the target acceleration as an unknown bounded external disturbance, the nonlinear disturbance observer is employed to estimate the external disturbance. The estimated disturbance is used to compensate the actual disturbance, which aims to alleviate the chattering and to make the proposed guidance law with stronger robustness. With the aid of the Lyapunov stability theory, the finite time convergence of the line-of-sight angle and the line-of-sight angular rate in both reaching and sliding phase is proven based on a fast terminal sliding mode and a switching controller that eliminates the singularity problem generated by the fast terminal sliding mode control. Numerical simulations are presented to demonstrate the effectiveness of the proposed guidance law. Although the. proposed guidance law is developed under the assumption that the missile speed is a constant, the simulation results for the time-varying speed of missiles are also presented to validate the proposed guidance law further.