【作者】 黄国勇；

【导师】 姜长生；

【作者基本信息】 南京航空航天大学 ， 控制理论与控制工程， 2007， 博士

【摘要】 空天飞行器(ASV)是新一代的航空航天器,它将填补临近空间(Near Space)航空航天活动的空白,并且具有极其重要的军事价值。ASV再入大气层的飞行环境变化剧烈、干扰大,因而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再入飞行的高精度、强稳定、快速自适应鲁棒控制问题展开了较为深入的研究。首先,在实验室已有成果的基础上,建立了ASV的再入模型,其控制系统包含反作用发动机(RCS)和控制舵面,以满足不同飞行阶段的控制要求。然后对其开环性能进行了分析,结果表明该模型具有复杂的非线性、耦合性以及快速时变性等特点,具有一定的代表性,可以为后续的研究工作提供参考。其次,基于Terminal滑模控制方法研究了ASV再入飞行控制系统的设计问题。在对综合干扰进行一定假设的条件下,得到了具有有限时间收敛特性的Terminal滑模闭环控制系统,可以保证系统跟踪误差在有限时间内收敛到零,从而提高了系统的响应速度。为了消除前述假设,提出另一种基于神经网络的自适应Terminal滑模控制方案,可以在线消除系统的综合干扰,并对闭环稳定性进行了严格的证明。两种方案都在ASV高超声速再入飞行条件下进行了仿真验证。随后,为了更有效消除综合干扰的影响,且易于工程应用,提出了基于模糊干扰观测器的自适应Terminal滑模控制方法,并基于Lyapunov稳定性理论给出了严格的稳定性证明。进一步,通过改进模糊干扰观测器的自适应律,设计了快速模糊干扰观测器,大大加快了其逼近速度,并将其应用到ASV再入飞控系统的设计中。最后的仿真结果进一步显示了该方法的优越性。在第五章中,重点研究了闭环系统的有限时间收敛特性和自适应律运算效率的问题。为了明确得到基于快速模糊干扰观测器的闭环系统的收敛时间,保留了模糊系统的逼近误差。此时,闭环系统误差不再收敛到零,而是收敛到可以任意小的某些区域。本章研究的另一个问题是如何减轻机载计算机的运算量。通过提出一种新型参数自适应律,将模糊系统在线调整的参数减少到两个,大大提高了运算效率。第六章首先分析了Terminal滑模面设计参数对滑模区域及达到时间的影响,然后设计了基于T-S模糊模型的时变自适应Terminal滑模控制系统。该方法采用T-S模糊系统在线逼近综合干扰,且时变滑模面有利于增大滑模区域,提高系统的鲁棒性,缩短到达时间。最后,研究了ASV状态观测器的设计问题。在考虑系统量测噪声的情况下,对系统进行两次扩张,设计了基于超扭曲算法(Super-twisting)的新型扩张状态观测器,保证观测误差在有限时间内收敛到零。接着利用可以测量的状态,结合精确微分器,对ASV未知状态进行了估计,该方法简单,精度高,易于工程应用。更多还原

【Abstract】 Aerospace vehicle (ASV) is the reusable flying vehicle of next generation. The vehicle fills the blanks of spaceraft’s activities in near space and has very important martial values. For the varieties of the aerosphere and the large disturbances, the design of attitude control system of ASV is a very difficult problem during the re-entry. In this dissertation, we focus on the high-precision, strong-stabilization, fast adaptive robust control of ASV re-entry.First of all, a simulation model of an ASV re-entry mode is presented based on the contributions of our lab. This model includes two kinds of actuators, the RCS and the control surface deflections, to satisfy different control tasks in the flight. Open-loop dynamics and stability characteristics demonstrate that this model is complex-nonlinear, coupling, fast time-varying, so it is able to be used in the following research works.Secondly, a discussion is devoted to the design of the control systems of ASV re-entry based on the terminal sliding mode control. Under the assumption to the totall disturbances, a terminal sliding mode control scheme with finite-time convergence is proposed. This scheme can promise that the tracking errors converge to zeros in finite time, and can improve the response speed of the closed-loop system rapidly. Then, in order to release the assumption above, an adaptive terminal sliding mode control based on neural networks is designed. The controller can compensate the totall disturbances online. After strict analysis to the stabilities, the simulation results are given to demonstrate the good performances of the controllers under the hypersonic conditions.In the following, an adaptive terminal sliding mode control method that based on the fuzzy disturbance observer (FDO) is designed, in order to eliminate the influences of the totall disturbances and be applicated easily. The stabilities of this method are proved strictly based on Lyapunov’s direct method. Furthmore, by modifying the adaptive law of the FDO, a fast fuzzy disturbance observer (FFDO) is presented to improve the convergence speed of FDO. Then the FFDO is used in the design of the flight control system of ASV re-entry. The simulation results demonstrate the superiority of proposed methods.In Chapter 5, the reseach emphases are the finite-time convergence of closed-loop system and the efficiencies of the adaptive laws. The approximation errors of fuzzy systems are holded to get the explicit expression of the convergence time. Then the errors of closed-loop converge to certain arbitary small regions, not to zeroes. Another problem studied in this chapter is how to alleviate the computation burden of the computers on-vehicle. A novel adaptive law for the fuzzy systems, only two parameters are adjusted on-line, is proposed to enhance the efficiencies of the computation.In Chapter 6, after the analysis to the influences of the design parameters to the sliding mode regions and the reaching time, an adaptive time-varying terminal sliding mode control method based on T-S fuzzy model is designed. In this scheme, on one side the T-S fuzzy systems are adopted to approach the totall disturbances on-line, on the other side the time-varying sliding surfaces are benefit to enhance the sliding mode regions, improve the robusticity of closed-loop systems and abbreviate the reaching time.Finally, the design of observers is studied. After extended the system two times, a novel state-extended observer based on super-twisting is presented. It provides the observer errors can converge to zeroes in finite time under the consideration of the measured noises. Then the unkown states of ASV are estimated using the measured states and the exact differentiation. This method is simple, high-precision, and easy to be applicated.更多还原