In this study, a composite robust control approach with non‐singular terminal sliding mode control and fixed‐time disturbance observer (FxTDO) is proposed for a class of second‐order non‐linear systems in the presence of matched uncertain disturbances. A bi‐limit‐weighted homogeneous FxTDO is designed based on the efficient utilisation of power functions obtained by the differentiation error amplification strategy. The FxTDO enjoys a fast convergence rate and simple parameters tuning process. By introducing the disturbance estimation to directly compensate the total disturbance in the composite control law, only a particular small gain‐based discontinuous control term is needed to guarantee the existence of sliding mode, and chattering phenomenon can be attenuated. The simulation results revealed the effectiveness of the proposed method.

This study proposes a three-dimensional appointed-time cooperative guidance law for multiple missiles. The maneuvering target can be hit simultaneously by multiple missiles with different expected line-of-sight (LOS) angles. It is worth noting that the actual convergence time of the LOS error or time-to-go can be treated as a tuning parameter along the LOS direction and the normal direction of LOS. Firstly, the simultaneous attack problem of multiple missiles can be regarded as a consensus problem. In the LOS direction, a distributed cooperative guidance law is presented to guarantee the time-to-go of all missiles to be consensus at the appointed time. Subsequently, a guidance law is also presented in the normal direction of LOS to achieve the expected LOS angles at the appointed time. Finally, to improve the robustness of the cooperative guidance system, an appointed-time extended state observer (ATESO) is developed for compensating the guidance commands. The stability of the proposed cooperative guidance law is fully proved by the rigorous theoretical derivation. Numerical simulation results verify the efficacy of this scheme.