Design of guidance law based on nonsingular terminal sliding mode control and finite-time disturbance observer*

The terminal guidance problem for missile intercepting maneuvering targets is investigated in this paper. To guarantee the disturbance rejection performance and alleviate the chattering problem, nonsingular terminal sliding mode control(NTSMC) and finite-time disturbance observer(FTDO) are introduced to design the composite guidance law considering the first-order autopilot dynamics. In this paper, the target acceleration and some state variables are regarded as unknown bounded disturbances. Finite-time disturbance observer(FTDO) is employed to estimate the disturbances and estimations of disturbances are employed as feedforward compensation to weaken the influence of disturbances. The proposed guidance law can guarantee that the line of sight(LOS) angular rate converges to zero in finite time. Simulation comparisons show the effectiveness of the proposed method.