A robust predictor-corrector entry guidance

With the development of aerospace industry, the guidance system of an entry vehicle becomes more robust, reliable and autonomous. Based on fuzzy logic, a predictor-corrector guidance law is proposed in this paper, where the trajectory prediction is realized by numerical integration. The correction system consists of two fuzzy controllers, which correct longitudinal motion and lateral motion synergistically. A drag acceleration profile is designed through interpolating between upper drag boundary and lower drag boundary, which is corrected continually to eliminate the range error. Attack angle, a secondary control variable in the paper, is used to eliminate the altitude error. In addition, the lateral error is removed by regulating the reversal time of bank angle. Compared with the traditional guidance laws, the method in this paper not only can correct synergistically the longitudinal motion and lateral motion of the vehicle, but also can easily cope with the flight constraints using interpolated drag acceleration profile. Moreover, in a correction cycle, the method designed in this paper only needs a single trajectory prediction, which reduces the on-board computation. The guidance law demonstrates a high precision and robustness in the simulation scenario.