Design of variable structure guidance law for head-on interception based on variable coefficient strategy

Head-on interception is a common guidance method for interception problem. The adaptive variable structure guidance law guiding the line-of-sight angular rate to converge to zero is available to improve the guidance precision. However, the variable structure guidance law leads to large required acceleration of interceptor before the line-of-sight angular rate converges to zero, especially in a situation where the target has strong maneuverability as well as high velocity. A strategy making the coefficients of the guidance law vary according to a typical rule via fuzzy control is proposed. Smaller guidance coefficients are selected at the beginning of terminal guidance. Therefore, the guidance command is reduced and a smaller acceleration of interceptor is incurred. As the coefficients grow to the fixed and desired values, the line-of-sight angular rate converges to zero rapidly so that the stability of the guidance system is guaranteed. It is concluded that the fuzzy variable coefficients strategy is highly effective for head-on interception as shown in the simulation.