基于主动控制策略的机翼颤振特性模拟

THE SIMULATION OF AIRFOIL FLUTTER CHARACTERISTIC BASED ON ACTIVE CONTROL STRATEGY

航空航天飞行器舵翼类结构的气动颤振是一种灾难性的动力学行为.在基于偶极子理论的气动弹性动力学模型中,气动载荷可表达为基于结构动力学响应的一种状态反馈的闭环控制力,控制律取决于翼型的几何参数、材料参数、结构动力学特性以及来流速度等多种条件,通常需通过实际飞行或风洞实验进行辨识与检验.在实验室条件下,以系统动力学响应的模态特征等效为前提,提出了一种基于人工主动控制的方式进行气动载荷下舵翼类结构自激颤振的特征值跟踪策略.建立并讨论了等效系统的非自伴随动力学微分方程及其特征方程的求解过程,并与通用软件的计算结果进行了对比,二者具有较好的一致性.通过优化搜索分别获得了位移和速度的最优反馈点、最优作动点位置及最优反馈增益系数,经对比计算拟合得到风速–位移增益曲线和风速–速度增益曲线,从而实现了由单点反馈、单点作动的集中力的闭环控制等效系统的真实气动力分布控制.仿真算例表明,由此预示的实验过程无需辨识和重构非定常气动力的时域波形,无需其他干预即可实现地面模拟实验,主动控制的效果满足预期,初步实现了自激颤振的特征值跟踪,为进一步推动主动控制模拟实验及颤振参数辨识提供了基础.

The aerodynamic flutter of aerospace vehicle Rudder-airfoil structure is a catastrophic dynamic behavior. In the aeroelastic dynamic model that is on the basis of doublet lattice theory, aerodynamic load can be expressed as a closedloop control force that is a kind of state feedback based on structural dynamic response. In fact, the aerodynamic forces received by each node are derived from the complex coefficient proportional feedback of the displacement response and velocity response of all nodes. The control law of feedback is dependent on the geometric parameters, material parameters,dynamic characteristics of the structure, flight altitude, air density and inflow velocity etc. It usually needs to be identified and validated by actual flight or wind tunnel testing. Under laboratory conditions, with the premise of equivalent modal characteristic in system dynamic responds, a strategy is put forward that is based on active control in order to track the eigenvalues of self-excited flutter in Rudder-airfoil structure under aerodynamic load. The process of solving the non-self-adjoint dynamic differential equation and its characteristic equation of the equivalent system is established and discussed. The comparison between the computed results and those results from the common software shows good consistency. Through optimization search, the optimal feedback point for displacement and velocity, the optimal actuation point, and the optimal feedback-gain factor can be obtained respectively. The fitting of the wind velocity-displacement gain curve and wind velocity-velocity gain curve can help to realize the real contribution control of the aerodynamic force of the equivalent system. Simulation example shows that the first two modal are the main modal of flutter and higher order modals do not participate in flutter, so the active control strategy focuses on the main modal of flutter. The result also shows that the predicted experimental process does not need identification or reconstruction of the unsteady aerodynamic force in time domain. Ground simulation experiment can be achieved without any other meddles. The active control reaches satisfied effects, ensure the variation characteristics of eigenvalue, achieves preliminary eigenvalue tracking of self-excited flutter, and provides a basement to further promote the active control simulation experiment and flutter parameter identification.