共轴式无人直升机建模与鲁棒跟踪控制

Modeling and robust tracking control for coaxial unmanned helicopter

针对共轴式无人直升机非线性、强耦合的动力学特性,本文提出了一种基于动态反馈线性化方法的鲁棒跟踪控制策略.首先根据叶素理论、Pitt-Peters动态入流模型、上下旋翼气动干扰分析建立了共轴式无人直升机的数学模型.然后对于高度-姿态子系统,通过扩展状态变量对其进行了动态反馈线性化,分析了零动态特性.根据内环期望跟踪特性对解耦后的子系统进行极点配置.通过设计鲁棒补偿器实现了对高度与姿态指令的鲁棒跟踪.在此基础上,针对水平面内的位置子系统设计了外环比例微分(proportional-derivative,PD)控制器以实现位置跟踪.最后,通过内环跟踪仿真验证了反馈线性化方法良好的解耦特性,通过干扰条件下的轨迹跟踪仿真验证了所设计控制器具有较好的控制性能与鲁棒性.

To deal with the nonlinearity and coupling characteristics in dynamics of the coaxial unmanned helicopter,we propose a robust tracking control strategy via dynamic feedback linearization technique. According to the blade elementtheory, Pitt-Peters dynamic inflow model and the disturbance analysis of coaxial rotors, we build the mathematical model ofa coaxial helicopter. On the height-attitude subsystem, a dynamic feedback linearization is performed through dynamic stateaugmentation, and the zero dynamic characteristic is analyzed. Poles are placed for the decoupled subsystems according tothe desired performance of inner-loop dynamics. A robust complementary controller is employed to improve the robustnessof height and attitude tracking. After that, an outer-loop proportional-derivative （PD） controller is designed for the planerposition subsystem to realize trajectory tracking. Finally, the decoupling characteristic of feedback linearization is validatedby tracking simulation of the inner loop, and the performance and robustness of the proposed controller for the whole systemis also validated via trajectory tracking under disturbance.