###### Abstract  
During the ascent phase of a missile, a challenging problem occurs that blocks the construction of a high-precision attitude control scheme, which directly affects accurate modeling including disturbances: non-linearities of an actuator, rapidly time-varying parameters, un-modeled dynamics, etc. In order to improve the control performance, an active disturbance rejection control (ADRC) scheme, considering non-linear dynamics of the actuator and wind disturbance during the ascent phase, is proposed in this paper. An expand state observer (ESO) is planned to estimate and compensate the actuator's non-linear dynamics, flight model uncertainties, and wind disturbance. Therefore, the complex non-linear time-varying control problem is simplified into a linear time-invariant control problem. The pitch attitude control system is controlled by the cascade method and ADRC controllers are designed for actuator close loop and attitude control loop, respectively. The simulation results show that ADRC has strong robustness under different dead-zones and external disturbances of the actuator. On the other hand, ADRC can effectively suppress the external atmospheric disturbance. Compared with the traditional gain-scheduling control scheme, the ADRC scheme can significantly reduce the overloading of the system and shows remarkable performance for tracking as well as wind resistance. **Keywords:** missile; ascent phase; ADRC; actuator non-linearities; wind disturbance +
Footnote †: journal: Applied  
be predicted or compensated in a way that will lead to system control failure in the case of large external interference. Therefore, it is necessary to adopt a new control method to address the challenge in the ascent phase. [PERSON] [5] et al. used a dynamic inverse control method to derive the inverse system of the hypersonic loaded vehicle, realized the feedback linearization between the input and output of the longitudinal model, and designed an adaptive controller, achieving better control effect. [PERSON] [6] et al. designed a non-linear dynamic inverse control law for a class of hypersonic aircraft, and obtained better control performance through robust enhancement method. Although the dynamic inverse control approach has excellent performance in model linearization, it requires an accurate dynamic model. Therefore, it is difficult to meet the control requirements during the ascent phase due to the uncertain model. Researchers also propose robust control [4], adaptive back-stepping sliding mode control [7], neural network [8], and other methods to suppress the disturbance of the aircraft, and have achieved certain success. In general, actuator dynamics are not considered in a traditional rocket or missile autopilot, and are always assumed to be an ideal loop, fast enough, and all non-linear factors are ignored [9]. But in practice, especially in high-precision attitude control, because of the existence of non-linear factors such as the dead-zone, backlash, saturation, etc., can reduce the dynamic performance of the actuator, which will lead to serious degradation of attitude control effect, it even causes oscillations and risks global stability [9; 10]. Therefore, in the ascent phase of the rocket, the controller is not only required to have a strong ability to resist external interference, but also to have high control accuracy and dynamic response under non-linear factors. Due to the limitations of manufacturing technology, the installation error and the debugging error, the dead-zone, the gear backlash and the zero position error, and other non-linearities inevitably exist in the actuator system. To solve this problem, [PERSON] [11] studies the non-linear saturation suppression by adopting a feedback structure, proportional control and dynamic angular velocity control law for attitude control. [PERSON] [12] proposed a two-stage separation method for approximate asymmetric backlash model and quantizer to solve the backlash non-linear problem, and separated the actual control from the coupling dynamics.