倾转旋翼飞行器模态转换阶段非线性控制方法研究

The tilt rotor aircraft, as a class of aerial vehicle with the compound property of the helicopter’s vertical takeoff-and-landing and the airplane’s high-speed cruise as well as high payload, has now gained more and more attention due to its promising prospect of applications in both military and civil fields. During transition flight, the tilt rotor aircraft is a typical over-actuated system having two kinds of control inputs, that is, the aerodynamic control surfaces and vector thrust. The flight control of a tilt rotor aircraft is still among the most challenging problems in aviation field, due to the considerable cross-couplings within three channels (yaw, pitch and roll) and the non-affine, nonlinear and time-varying dynamic characteristics involved. With the aid of the concept of virtual/generalized control surfaces, the six-degrees-of-freedom dynamic equation of the tilt rotor aircraft is transformed into a control-oriented model. The control-oriented model distinguishes itself from the general state-space formulation in that it consists of the conventional nonlinear state-space equations, and a set of algebraic equations characterizing the mapping from the virtual control-surface deflects to the actual control-surface deflects. Based on polynomial sum of squares (SOS) convex optimization theory, the nonlinear control and strong robust control problems will be investigated. Therefore, the study will focus on deriving the control design scheme of such nonlinear time-varying systems. Furthermore, the nonlinear control subject to multiple performance objectives will be considered, in view of the fact that nonlinear control approaches seldom take into account the performance requirements. Therefore, aiming at setting up the new theory and approaches for control design of a tilt rotor aircraft, the study is also a valuable supplement to the nonlinear control and robust control theory. Simulations will be conducted to evaluate the effectiveness of the theoretical results.

倾转旋翼飞行器能够在复杂环境下实现垂直起降，具备较强的巡航与运载能力，在国防和民用领域均有广泛应用前景。在模态转换飞行阶段，倾转旋翼飞行器是典型的过驱动系统，偏航、俯仰和横滚三通道之间耦合严重，系统呈现出非仿射、非线性和时变的动力学特征，这给飞行控制系统设计带来很大挑战。本项目借助虚拟/广义操纵舵概念，将飞行器的六自由度动力学方程转换为有别于传统状态空间描述的控制设计模型。该模型包含常规的非线性状态方程，以及反映虚拟舵偏转与实际舵偏转约束关系的一组代数方程。在此基础上，应用SOS凸优化理论，研究这类系统的非线性控制和强鲁棒控制问题，建立非线性时变系统的控制设计方法。现有非线性控制方法较少涉及性能指标要求，进一步探索多种性能指标约束下的非线性控制方法。这些内容是对非线性和鲁棒控制理论的有益补充。最后，通过仿真实验验证理论成果的可行性，为倾转旋翼飞行器控制设计提供新的原理和方法。

倾转旋翼飞行器模态转换阶段飞行控制是目前航空领域一项有挑战性的工作。在模态转换阶段，倾转旋翼飞行器呈现出强耦合、非仿射、非线性和时变动力学特征。相比常规飞行器，倾转旋翼飞行器具有更大的飞行包线和更复杂的动力学特征。此外，飞行过程中，还存在着不可忽视的外部扰动和参数摄动等不确定性。因而，传统的基于小扰动线性化的方法不再适用于倾转旋翼飞行器模态转换阶段飞行控制。.本项目中，倾转旋翼飞行器模态转换阶段的飞行控制问题被转换为含时变参数的多项式非线性系统的镇定问题。首先，借助虚拟/广义操纵舵概念，我们将倾转旋翼飞行器六自由度动力学方程转换为面向控制的模型，即含时变参数的多项式非线性系统。其次，采用多项式SOS凸优化理论，我们针对这类系统建立了非线性时变镇定控制方法。进一步，针对输入受限情形，我们给出了指数镇定结果。再次，设计了基于干扰观测器的控制方案，提高了系统对外部扰动和参数摄动的鲁棒性。此外，我们还提出应用S型轨迹规划算法设计倾转角参考轨迹，配合控制律设计，形成倾转旋翼飞行器轨迹规划和跟踪控制一体化设计方法。最后，本项目的理论成果应用在倾转旋翼飞行器模态转换阶段的飞行控制，仿真验证了方法的可行性和有效性。.本项目形成的含时变参数的多项式非线性系统控制理论和方法，是对现有的多项式LPV和多项式非线性系统控制理论的进一步发展和推广，也是对现有时变非线性控制理论和鲁棒控制理论的有益补充，具有广阔的应用前景。