Coordination and Control of Multiple Spacecraft using Convex Optimization Techniques
Coordination and Control of Multiple Spacecraft using Convex Optimization Techniques
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发表时间：
2002-06
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通讯作者：
J. How
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作者：
J. How
文摘：多航天器编队飞行是未来许多空间科学任务的使能技术。例如，这些未来的任务将使用高度协调的分布式运载器阵列，用于地球测绘干涉仪和合成孔径雷达。本文提出了为航天器机队设计的协调和控制算法。这些算法被嵌入到一个层次化的舰队结构中，该结构包括一个用于编队机动的高级协调器，用于形成编队配置、调整编队大小或重新确定目标，以及低级控制器，用于为每辆车生成和实施单独的控制输入。将弹道和控制问题归结为线性规划(LP)优化问题，以求最小燃料机动。高级协调和低级别控制器的组合结果是一个非常灵活的优化框架，可以脱机分析任务设计的各个方面，并作为机载自主编队飞行控制系统的一部分进行实时分析。本文还研究了与实现这种编队飞行方法相关的几个关键问题。特别是，对线性规划算法的改进包括：对传感器噪声的鲁棒性，包括执行器约束，确保最优解始终是可行的，并减少线性规划解的时间。此外，还从两个关键问题对控制问题的动力学进行了分析：1)应该使用什么动力学模型来指定保持被动孔径的期望状态；以及2)应该使用什么动力学模型来表示LP中关于该状态的运动。分析中考虑了几种线性化的相对动力学模型，包括圆轨道的Hill方程，部分考虑J2效应的修正的线性动力学，以及偏心轨道的Lawden方程。
Abstract : Formation flying of multiple spacecraft is an enabling technology for many future space science missions. These future missions will, for example, use the highly coordinated, distributed array of vehicles for earth mapping interferometers and synthetic aperture radar. This thesis presents coordination and control algorithms designed for a fleet of spacecraft. These algorithms are embedded in a hierarchical fleet archi- tecture that includes a high-level coordinator for the fleet maneuvers used to form, re-size, or re-target the formation configuration and low-level controllers to generate and implement the individual control inputs for each vehicle. The trajectory and control problems are posed as linear programming (LP) optimizations to solve for the minimum fuel maneuvers. The combined result of the high-level coordination and low-level controllers is a very flexible optimization framework that can be used off-line to analyze aspects of a mission design and in real-time as part of an on-board autonomous formation flying control system. This thesis also investigates several crit- ical issues associated with the implementation of this formation flying approach. In particular, modifications to the LP algorithms are presented to: include robustness to sensor noise, include actuator constraints, ensure that the optimization solutions are always feasible, and reduce the LP solution times. Furthermore, the dynamics for the control problem are analyzed in terms of two key issues: 1) what dynamics model should be used to specify the desired state to maintain a passive aperture; and 2) what dynamics model should be used in the LP to represent the motion about this state. Several linearized models of the relative dynamics are considered in this analysis, including Hill's equations for circular orbits, modified linear dynamics that partially account for the J2 effects, and Lawden's equations for eccentric orbits.