Drag tracking sliding mode control for mars atmospheric reentry

In view of the mars reentry problem under external disturbance, this paper presents a guidance algorithm based on drag tracking. First of all, the reference drag is calculated based on the reentry model and the reference trajectory. Secondly, estimated disturbance via the sliding mode observer, this paper improve the accuracy of the controller parameters and increase the anti-disturbance capability. Finally, the sliding mode guidance law for drag tracking is proposed based on the observer, reentry model and the reference trajectory. The simulation results indicate that the anti — disturbance capability of the guidance law is increased by introducing the sliding mode observer. The proposed guidance law can effectively enhance the response speed and decrease the tracking errors, with higher practical value, compared with the traditional PD algorithm.