【作者】 钱承山；

【导师】 吴庆宪；

【作者基本信息】 南京航空航天大学 ， 控制理论与控制工程， 2009， 博士

【摘要】 空天飞行器(Aerospace Vehicle, ASV)是各国大力发展的新型航空航天飞行器之一,具有重要的军事价值和民用价值。美国等国家都制定了各自的空天飞行器研究计划,且取得了许多重大进展,而目前我国在高超声速方面尚处于起步阶段,很多关键问题还需要深入研究。ASV再入大气层过程中气动参数变化剧烈、控制精度要求高,使得控制系统设计面临许多挑战,其姿态控制系统的设计是一项非常前沿的研究课题。本文围绕这一问题,对ASV再入姿态飞行控制系统设计展开系统研究,并通过理论分析和仿真予以验证。获得的主要结果如下:首先,重点考虑了ASV在跨大气层再入飞行时空气稀薄、气动舵面低效或失效且推力系统关机不能提供推力矢量的情况下,建立了ASV在跨大气层再入时的数学仿真模型,所建数学模型包含完整的6自由度动力学方程和运动方程。气动力和力矩系数是迎角、马赫数、高度及控制舵面偏角的函数,反作用控制系统(RCS)推进器属于开关型的,控制量可近似为常值开关型的量。开环特性分析说明整个模型能够体现出ASV复杂的非线性、耦合性以及快时变性等特点,可满足新一代高超声速飞行器轨迹优化、姿态控制等问题的概念设计和仿真研究。其次,研究了ASV再入跨大气层飞行时的姿态控制问题,建立了ASV再入多区域T-S模糊模型,在各区域设计区域T-S模糊控制器,这样在模糊规则数相同的情况下由于模糊论域的变小从而提高了控制精度。在ASV跨大气层再入飞行时,通过RCS中的反作用发动机推力产生控制力矩来控制ASV的姿态,以补偿气动舵面操纵失效或者部分失效而引起的控制力矩不足;随着空气密度的增加,气动舵面逐步介入控制系统,RCS随之逐步退出。考虑ASV在空气稀薄、气动舵面低效或失效的情况,设计了基于反作用发动机推力的ASV再入姿态飞行控制系统。接着,研究了ASV再入姿态广义模糊多模型跟踪控制问题,通过把一般的模糊模型等价变换到广义模糊模型,从而引入了松弛变量,可以直接求解同一组线性矩阵不等式(LMIs)就能获得全部参数的解,使得求解LMIs的可行性更大,降低了局限性。随后,考虑到ASV再入飞行中很难对各种外界干扰有足够的认识,因此提出新的基于补偿的多模型切换组合控制策略。设计非线性干扰观测器(Nonlinear Disturbance Observer, NDO)来估计外界干扰,通过相应的反馈补偿控制律削弱或抵消外界干扰。基于Lyapunov理论证明了闭环系统的稳定性,仿真结果表明新方案不仅有效且可以提高不确定条件下系统的控制性能和鲁棒性。最后,提出一种基于局部T-S模型的非线性系统非脆弱多模型切换控制,且考虑控制器存在可加性摄动的情况下,给出了非脆弱状态反馈控制器的设计方案。将所设计方案应用到ASV再入姿态飞控系统并进行了仿真,仿真结果表明所设计方案降低了控制器对其本身参数摄动的敏感性,亦即提高了控制器的非脆弱性。更多还原

【Abstract】 Aerospace vehicles (ASV) are a new type of aerospace planes. Many countries are devoting major efforts to develop this reusable flying vehicles. Aerospace vehicles have very important military values and civilian values. The United States and other countries have their own aerospace projects and have achieved significant research progress. However, the research on hypersonic vehicles in our country is still at in the initial stage, a good number of important problems in this field still call for deeper study. Aerospace vehicle’s reentry has the characteristic of violent aero-dynamic parameters change and demands high control performance. These characteristics make the control system face with many grave challenges for aerospace vehicles. The flight attitude control system design methods are studied systematically and comprehensively in this dissertation by means of theoretical analysis and simulation validation. The results attained are as follows.First of all, the problems about the modeling of six degrees of freedom of an ASV under the reentry flight condition are studied. The proposed model includes the whole of kinetic equations and motion equations. Aerodynamic force and moment coefficients are given as functions of angle of attack, Mach number, altitude and control surface deflections. The thrusters of reaction control system (RCS) are of switch type and the control value is approximately switching constant. Open-loop dynamics and stability characteristics proves that the whole model can demonstrate the complex nonlinearity, coupling and rapid variation of ASV. Therefore, the proposed model can be used to investigate trajectory optimization, attitude control conceptual design and simulation for a new generation hypersonic vehicle.Secondly, the problems concerning the ASV’s atmospheric reentry flight attitude control system are researched. Multiple region T-S fuzzy models are modeled for ASV reentry attitude dynamics, and then local T-S controllers are designed in every region. The approach precision improves as the fuzzy domain decreases under a constant fuzzy rule. During reentry through the atmosphere, the control moment is generated by thrusters of the reaction control system to control attitudes of the ASV, and to compensate for the shortage of aero-surfaces that fail to offer enough moment because of the partially or completely lost efficiency. Along with the increase in air density, aero-surfaces gradually intervene the control system, and the RCS drops out of use. Considering the air scarcity and the decreased efficiency of aero-surfaces, the flight attitude control system for the ASV based on thrust of reaction jets is designed.Thirdly, a T-S fuzzy descriptor tracking control design for an atmospheric reentry flight attitude control system of aerospace vehicles is discussed. Slack variables are introduced into the model by equivalent transforming of the ordinary fuzzy model to a fuzzy descriptor model, and then a H∞tracking controller design method which is based on linear matrix inequality (LMI) is obtained. Its advantages are to solve all the controlling variables in LMIs at the same time. This improves the feasibility and debases the limitation to solving LMIs.Then, for it is hard to obtain enough knowledge about disturbances generated by an exogenous system, a novel multi-model switching integrated control based on compensation is proposed. A nonlinear disturbance observer is designed to deduce external disturbances and then to compensate for the influence of the disturbances using proper feedback. Based on Lyapunov theory, it is proven that the closed-loop system is exponential stability. The simulation results demonstrate that the proposed method is not only effective but also can improve control performance and robustness under uncertainty condition.Finally, a non-fragile multi-model switching control for a class of nonlinear systems based on local T-S models is proposed. The design scheme of non-fragile state-feedback controllers is developed in the presence of additive controller gain perturbations. We apply the scheme to the flight attitude control system for the ASV and make simulation. The simulation results show that the scheme can debase the sensitiveness of the controller with respect to perturbation in its coefficients, in other words, the scheme improves the non-fragile of the controller.更多还原