# A Novel Disturbance Rejection Control of Roll Channel for Small Air-to-Surface Missiles
## 1 Introduction
The nonlinear model of aircraft pitch channel was linearized, and the disturbance was compensated to the extended model. Finally, the desired angle of attack was tracked and controlled. Furthermore, some scholars focused on the disturbance in attitude control. The variable structure control scheme was proposed in literatures [23; 24], which made the system sensitive to parameters and external disturbances after entering the sliding mode region, but also caused high frequency flutter. The attitude control of flexible multi-body satellite non-gyro or gyro fault was studied in reference [25]. Active disturbance rejection attitude controller was used to realize high precision and high stability attitude control. However, other disturbance factors were not considered. Literatures [26; 27; 28] have proposed an adaptive control algorithm for spacecraft attitude. The algorithm is robust to parameter uncertainty, but did not consider the suppression effect of the distance. In the controller design mentioned above, some disturbance factors were considered, but the influence of internal and external disturbance on the attitude control were not considered comprehensively. From previous analysis, the studies on the types of disturbances are not comprehensive enough. Besides, there are relatively few researches on micro air vehicles, whose roll control has the characteristics of relatively small moment of inertia and poor anti-disrurbance performance. Moreover, it directly affected the maneuverability and stability of the guidance process. The research content in this paper is mainly reflected in the following points:  
1. In the article, the internal and external disturbances, such as aerodynamic parameter perturbation, structural mass characteristic deviation, inertial navigation drift and wind disturbance, are regarded as the uncertainties of the control system. We compare with the existing research, and focuse on the influence of the uncertainties on the roll channel control for small air-to-surface missiles. 2. The system uncertainty is estimated through the extended state observer, and the estimated value is fed back to the control law through nonlinear feedback. It is compensated to the attitude control of the roll channel, and the roll angle is controlled according to the control command of the roll channel. Consequently, the stable tracking control of missile roll attitude is realized. 3. The internal and external disturbances are comprehensively considered, and different parameters are set for comparative analysis. The algorithm is compared with other adrc algorithms and PID to verify the effectiveness of the algorithm. This paper is organized as follows: Section 2 mainly describes the dynamic model of small missile roll channel. Section 3 is mainly about the design of controller based on ESO. First, a description of the ADRC model is presented. Further, the schematic structure of the ESO based controller is also designed. In Section 4, the simulation results under different disturbances and the comprehensive discussion are carried out in detail.