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In this paper, a composite anti-disturbance autopilot design for a missile system is proposed based on finite time integral sliding mode control scheme and nonlinear disturbance observer technique. First, a nonlinear disturbance observer is developed to estimate the external disturbances with partial known information. Second, in order to obtain good disturbance rejection performance and reject the other type of disturbances, a finite time integral sliding mode control strategy is employed to the design of a feedback controller. Third, an improved adaptive composite anti-disturbance autopilot is given to avoid the inaccuracy of the upper bound of external disturbances. Finally, simulation results are employed to demonstrate the effectiveness of the proposed method.

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A mixed H∞/ H2 gain-scheduled state-feedback control method is developed for trajectory tracking of spacecraft rendezvous in elliptical orbits. Since the tracking accuracy is vulnerable to exogenous disturbances, the mixed H∞/ H2 control, which takes into consideration both worst-case disturbance-attenuation performance and tracking performance, is particularly attractive for trajectory tracking of spacecraft rendezvous. Owing to the fact that the dynamic model for elliptical-orbit rendezvous is time varying, the feedback gain matrix is formulated as a matrix fraction of parameter-dependent matrix. Parameter-dependent Lyapunov functions are adopted to reduce conservatism caused by fixed quadratic Lyapunov matrices, and slack matrices are introduced to avoid setting a common Lyapunov matrix for different performances. Then, the desired controller can be obtained through a convex optimization with linear matrix inequality constraints. Computer simulations show that the proposed method can (a) handle trajectory tracking of elliptical-orbit rendezvous effectively; (b) provide a balanced performance between disturbance-attenuation performance and tracking performance; and (c) yield results that are less conservative than those obtained through conventional methods.