针对大扰动下小型无人直升机位置的精准控制和机体震颤问题，提出了一种改进的滑模控制器。首先，针对亚拓T-REX 300X机型动力学模型中包含的未知气动参数，设计了三项飞行实验用于数据采集，并确定了完整的气动参数。其次，设计了位置和航向双通道控制策略并提出了一种改进的滑模控制器，实现其在持续大扰动下的悬停控制；此外还结合稳定性分析给出了在滑模趋近律中可以有效抑制震颤的参数范围。模型验证实验表明，通过飞行实验确定的气动参数具有较高的保真性；控制仿真实验表明，在持续的大扰动下阶跃响应的稳态误差小于0.02。在改进的滑模控制器下，直升机控制精度高、震颤弱，舵控信号曲线平滑，更有利于实际工程中无人直升机在有扰动下的精准悬停实现。

In view of the position control accuracy and body chattering of small unmanned helicopter under large disturbance, an improved sliding mode controller (SMC) was proposed. Firstly, for the unknown parameters in the dynamic model of small unmanned helicopter named Align T-REX 300, three flight experiments were designed for the data acquisition, determining the comprehensive aerodynamic parameters. Then, the dual-channels control strategy with an improved SMC was designed to realized the helicopter hovering. The parameters ranges of SMC were presented by combining stability analysis, which can effectively suppress chattering. The model validation experiment shows that the aerodynamic parameters determined by the flight experiments have high fidelity. Moreover, the control simulations show that the steady state error of the step responses is less than 0.02 under the continuous large disturbance. Under the improved SMC with high control accuracy and weak tremor, the servos' control signal curves are smooth, which is more conducive for achieving the flight control of unmanned helicopter under the disturbance in actual engineering.