火星大气进入段轨迹设计和制导方法研究

发布时间：2019-03-13 12:03

【摘要】：随着火星探测任务的深入开展,火星表面采样返回和载人登陆火星已经是未来火星探测新阶段的目标,探测器的着陆精度成为探火任务成功与否的关键因素。在大气进入阶段进行有效的制导与控制是提高着陆器着陆精度中必然和重要的技术手段之一,因此对火星探测器在大气进入段的相关技术和理论进行较深层次的研究,设计合理的火星大气进入段的轨迹和高精度制导系统,已经成为当前火星研究的重点。本文结合科技部973项目“行星表面精确着陆导航与制导控制问题研究”和国家自然科学基金项目“行星着陆自主导航方法研究”,以提高火星探测器大气进入段开伞点精度为目标,对该阶段的轨迹设计与制导关键技术进行了系统地研究,主要研究成果如下:研究了火星探测器在大气进入段的轨迹设计问题。基于火星大气进入段的动力学模型,利用蒙特卡洛方法,对影响探测器开伞点状态的各种误差源进行了分析。结果表明在火星大气进入段,大气密度以及气动力参数不确定性对轨迹开伞点精度影响较大。为了降低这些误差源对开伞点精度的影响,将大气密度及气动力参数中的不确定性作为一阶齐次常微分方程初值问题加入到轨迹设计中,并结合火星着陆器在大气进入阶段的任务特点,构建了新的鲁棒性能指标,提出了基于状态灵敏度的鲁棒轨迹设计方法。该方法对应的最优控制问题得到的轨迹对各种误差源的敏感程度明显降低。利用线性协方差分析方法定量地分析了火星大气进入过程中的各种误差因素对开伞点状态的影响,提出了基于协方差分析的鲁棒轨迹设计方法。该方法中利用协方差矩阵的传播方程以及对称性,将开伞点状态的协方差加入到原目标函数中,同时还考虑了大气密度、气动力参数的不确定性,以及探测器受到的动力学约束、控制约束、路径约束等其他约束条件,通过该方法规划出来的轨迹可以有效地提高开伞精度。随后,分别从计算复杂度和鲁棒性能两方面对上述基于状态灵敏度和基于状态协方差的轨迹设计方法进行了详细的比较和分析。研究了火星探测器在火星大气进入段内的轨迹跟踪问题。针对探测器在大气进入段的实时性以及精确性要求,考虑到初始进入点偏差、大气密度及气动力参数不确定性对探测器轨迹的影响,设计出了基于模型预测静态规划技术的轨迹跟踪方法。该方法将模型预测控制和静态规划理论相结合,只需在线求解静态规划问题,结构简单具有控制解析解。同时,为了提高在线计算速度,利用递归方法求解计算控制量所需的系数矩阵,在保证实时性要求的情况下,有效地降低了实际飞行轨迹和标称轨迹之间的误差,实现了较高的开伞点状态精度。对火星大气进入段的预测跟踪制导方法的关键技术问题进行了研究。首先,利用平衡滑翔条件将轨迹分为进入初段、平衡滑翔段和进入末段,重点针对平衡滑翔段航迹角变化为零的条件,结合线性二次型规划的轨迹跟踪方法,设计出了基于常值航迹角的解析预测跟踪制导方法。该方法计算速度快,对各种扰动和不确定因素具有一定的适应能力,但是在扰动环境恶劣情况下的开伞精度偏低。为了实现高精度的制导,进一步设计了基于常值航迹角的数值预测跟踪制导方法,该方法根据轨道特性将大气进入段轨迹设计为Pre-bank段、航程控制段和航向修正段,重点针对航程控制段待飞航程的要求利用牛顿辛普森方法确定常值航迹角参数,采用反馈线性化方法设计了轨迹实时跟踪航迹角的控制律,仿真结果表明它具有较高的开伞精度,但是计算速度较慢。分析比较以上两种预测跟踪制导方法,并探讨了它们在火星大气进入段任务中的适用性。
[Abstract]:With the development of the Mars exploration mission, the surface sampling of Mars and the manned landing of Mars have been the target of the new stage of the future exploration of Mars, and the landing accuracy of the detector is the key factor for the success of the fire detection task. The effective guidance and control at the air entering stage is one of the necessary and important technical means to improve the landing precision of the lander, so the related technology and the theory of the Mars detector in the atmospheric entry section are deeply studied. The design of a reasonable trajectory and high-precision guidance system for the entry of the Mars atmosphere has become the focus of the current Mars research. Based on the "Research on the Precision Landing and Guidance Control of the Planetary Surface" of the 973 Project of the Ministry of Science and Technology and the "Research on the Autonomous Navigation Method for Planetary Landing" of the National Natural Science Foundation of China, the paper systematically studies the trajectory design and the key technology of the guidance of the trajectory design and guidance of the Martian detector, and the main research results are as follows: The trajectory design of the Mars probe in the atmosphere is studied. Based on the dynamic model of the atmosphere entering section of Mars, the various error sources that influence the state of the open-and-open point of the detector are analyzed by using the Monte-Carlo method. The results show that the influence of the atmospheric density and the uncertainty of aerodynamic parameters on the accuracy of the trajectory opening point is great. In order to reduce the influence of these error sources on the accuracy of the open-loop point, the uncertainty of the atmospheric density and the aerodynamic parameters is added to the trajectory design as the first-order homogeneous ordinary differential equation and combined with the mission characteristics of the Mars lander during the atmospheric entry phase, A new robust performance index is constructed, and a robust trajectory design method based on state sensitivity is proposed. The trajectory of the optimal control problem corresponding to the method obviously reduces the sensitivity of various error sources. The influence of various error factors on the state of the umbrella point is analyzed quantitatively by using the linear covariance analysis method, and a robust trajectory design method based on the covariance analysis is proposed. The method comprises the following steps of: using the propagation equation and the symmetry of the covariance matrix, adding the covariance of the state of the open umbrella point into the original objective function, taking into account the uncertainty of the atmospheric density, the aerodynamic parameters, and the dynamic constraint and the control constraint that the detector is subjected to, And other constraints such as path constraints can effectively improve the accuracy of the opening and closing by using the track which is planned by the method. Then, the method of trajectory design based on state sensitivity and state covariance is compared and analyzed from two aspects of computational complexity and robustness. In this paper, the trace tracking problem of the Martian detector in the atmosphere of Mars is studied. In view of the real-time and accuracy requirements of the detector in the atmospheric entry section, the trajectory tracking method based on the model predictive static planning technique is designed in view of the influence of the initial entry point deviation, the atmospheric density and the aerodynamic parameter uncertainty on the trajectory of the detector. The method combines the model predictive control with the static planning theory, and only needs to solve the static programming problem on-line, and the structure is simple and has the control and resolution solution. At the same time, in order to improve the on-line calculation speed, the coefficient matrix required for calculating the control amount is solved by a recursive method, and the error between the actual flight path and the nominal track is effectively reduced under the condition that the real-time requirement is ensured, and the state accuracy of the high-opening point state is realized. The key technology problem of the prediction and tracking guidance method for the entry section of the Mars atmosphere is studied. firstly, the track is divided into a first section, a balanced glide section and an entry end section by using a balance gliding condition, and the track tracking method combining the linear quadratic programming is focused on the condition that the change of the track angle of the balance glide section is zero, An analytical and predictive tracking guidance method based on the constant-value track angle is designed. The method has the advantages of high calculation speed, certain adaptability to various disturbance and uncertain factors, and low opening and opening precision under severe disturbance conditions. in order to realize high-precision guidance, a numerical prediction and tracking guidance method based on a constant-value track angle is further designed, which is designed as a Pre-bank section, a range control section and a heading correction section according to the track characteristics, The control law of track angle in real-time track is designed by means of the method of feedback linearization. The simulation results show that it has high open-parachute precision, but the calculation speed is slow. In this paper, two kinds of predictive tracking guidance methods are compared, and the applicability of these two kinds of prediction tracking guidance methods is discussed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：V448.2;V412.41

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