【作者】 龚正；

【导师】 王同光； 沈宏良；

【作者基本信息】 南京航空航天大学 ， 流体力学， 2011， 博士

【摘要】 本文综合研究第四代有人驾驶战斗机与下一代无人作战飞机等先进飞行器的气动/运动/控制耦合问题,发展和建立了空气动力学/飞行力学/飞行控制等多学科交叉的建模、设计和分析方法。第一部分研究了大迎角过失速机动中非定常气动力建模方法及飞行动力学特性影响分析方法。首先,针对四代机等飞行器大迎角过失速机动时气动/运动非线性耦合问题,基于动力学系统建模思想,建立非线性微分方程形式的气动模型描述非定常气动特性,分析和揭示了非定常气动现象的物理机理,并发展和改进了基于强迫振荡风洞试验的模型参数辨识方法:基于小振幅实验数据,采用线性回归参数辨识方法辨识气动模型中特征时间常数等线性项参数;基于大振幅实验数据,采用遗传算法全局寻优辨识气动模型中非线性项参数。以带中心体三角翼构型飞机模型为例,基于风洞试验结果进行气动建模与验证,研究结果表明:模型可精确预测非定常气动特性,具有运动状态普适性、与运动方程兼容性等特点,模型辨识方法具有较强的工程可行性。其次,采用模态分析方法,研究了纵向非定常气动力对大迎角飞行动力学特性的影响,并使用输出反馈特征值分配方法,初步设计了大迎角下纵向增稳飞行控制律,通过不同气动模型间的对比分析,揭示了基于常规气动导数模型所建立的大迎角飞行控制律可能潜在的问题。第二部分研究了无垂尾飞翼布局先进飞行器的飞行控制律重构和闭环飞行动力学特性分析问题。首先,针对无垂尾飞翼布局无人飞机本体航向静不稳定特性、多舵面控制等特点,研究了在无侧滑角传感器或其故障情况下的控制律重构设计。本文以某无垂尾飞翼布局飞机缩比模型为例,综合采用可达力矩集分析、改进的横航向动稳定性边界图、特征值分析和可达平衡集分析等方法,全面分析确定了该飞行器本体气动特性、气动控制效能与开环飞行动力学特性。以此为基础,研究了基于飞行品质、控制效能、鲁棒特性的多目标折中飞行控制律设计方法,实现了基于纯角速度反馈的横航向控制律,并综合采用动压调参控制、横航向交联控制、迎角限制、舵面分配等控制律方法,构成了缩比验证模型飞机的完整控制律。其次,针对无垂尾飞翼布局无人飞机气动/运动/控制高度耦合特点,为了验证飞行控制律有效性,对气动模型不确定性、舵面非线性等影响因素进行综合分析评估。本文提出了基于计算飞行力学思想的控制律验证框架:采用闭环系统特征值打靶法“云图”分析、闭环可达平衡集分析等评估方法,确定了闭环线性飞行动力学系统在飞行包线范围内的稳定性与鲁棒性;采用分叉分析、吸引域分析等非线性方法,评估舵面死区/饱和、舵面速率饱和等三种非线性因素对闭环控制效果的影响;基于人在环虚拟样机技术进行飞行模拟,综合验证突风、大气紊流等外界干扰因素对六自由度闭环飞行动力学系统飞行品质的影响;通过缩比模型试飞试验,验证了上述飞行控制律设计及验证方法的有效性。研究结果表明,基于纯角速度反馈的横航向控制律适用于该类飞行器在无侧滑角传感器或其故障情况下,实现一定飞行包线范围内的有效控制,保证飞行安全。本文建立的气动建模、飞行动力学特性分析、控制律设计及验证方法,对国内先进飞行器的设计和分析具有一定的理论和工程参考价值。更多还原

【Abstract】 The aerodynamics/movement/control coupling problems in design of advanced flight vehicle, such as the 4th-generation flighter and the next-generation UCAV, are studied in this paper. New modeling, design and analysis methods based on multi-discipline research and application are developed and established.Unsteady aerodynamic modeling method in high angle of attack and its impact on flight dynamic system are researched in the first part of the paper. To solve the aerodynamics/movement coupling problem in high angle of attck when the 4th-generation fighters perform post-stall maneuvers, based on the dynamic modeling thoughts, ordinary differentical equations are used to describe and reveal the unsteady aerodynamic characteristics. A new method is introduced to improve the identification procedures based on wind-tunnel experiments: Linear Regression method is used to identify the linear parameters such as characteristic time constant with small-amplitude forced oscillation experiments; Genetic Algorithm method is used to identify other nonlinear parameters with large-amplitude forced oscillation experiments. Taking delta wing model with center body as the example, this modeling method is tested and verified. The results show that the established models could predict the unsteady aerodynamic forces accurately in arbitrary movement and is easy to coordinate with flight dynamic equations, which shows the feasibility in aeronautic engineering. Furthermore, using Modal Analysis method, the impacts of unsteady aerodyanmics on flight dynamic system are studied and the primary flight control law for high angle of attack is designed with Eigenvalue Assignment method. Comparative analysis is carried on different unsteady aerodynamic models, and the results reveal the potentially problems if the flight control law is established based on traditional aerodynamic derivative models.The flight control law reconfiguration design and the closed-loop flight dynamic characteristics for the advanced flight vehicle in fly-wing configuration are studied in the the second part of the paper. Firstly, the flight control law reconfiguration design in the case of side-slip sensor failure is studied for fly-wing aircraft, which is static directional unstable and uses multi-surfaces to prvide directional control. Taking a small-scaled UCAV model as the example, different methods, such as Attainble Moment Set, Attainable Equilibrium Set, are used to analyse its aerodynamics, control efficiencies and the open-loop flight dynamic characters. The multi-objective optimization method considering flight qualities, control power and robustness is introduced to design the lateral-directional flight control law. And the entire control law consists of dynamic-pressure scheduling, lateral-directional coupling control, AOA limiter and control power allocation. Moreover, the flight control law clearance frame based on computational flight dynamics is established to verify the validity of flight control law. Based on Monte Carlo shooting method and AES method, the linear impacts such as aerodynamic uncertainty are analysed and evaluated; based on Bifurcation Analysis method and Regions of Attractions analysis method, the nonlinear impacts, such as the dead-zone/saturation/rate saturation of actuators, are estimated. And then, flight simulations are used to train the operator and evaluate the atmosphere turbulence impacts. The research and test flights’results indicate that the flight control law using only roll/yaw rate feedbacks could help to stabilize the aircraft when the side-slip sensor fails, which guarantees the flight safety.The new methods established in this paper for aerodynamic modeling, flight dynamic analysis, control law design and clearance have rich engineering referece value in the design and analysis work for developing the next-generation advanced flight vehicle.更多还原