Lockheed Martin Simulates Orion Spacecraft Missions Using a Multidomain Power System Model

Several years ago, Lockheed Martin engineers developed a power system model for NASA’s Constellation program using Microsoft^®Excel^®和Visual Basic^®用于应用程序（VBA）。但是，当工程师试图检查越来越多的测试用例时，该模型放慢了速度，偶尔会崩溃。由于它是单节点电源模型，因此团队无法使用它来评估整个系统中的电压降低或评估电源质量要求。

洛克希德·马丁（Lockheed Martin）需要创建猎户座电力系统（Orion Power System）的多键模型，包括其发电，存储和配电组件，然后运行模拟以验证设计，测试故障条件，验证系统性能并执行任务分析。他们想要一个视觉模型，其NASA同事将立即理解，而无需检查低级代码。

Lockheed Martin engineers used Simulink and Simscape Electrical to model and simulate the power system for the Orion spacecraft.

To model the solar arrays, the team created a custom solar cell model written in the Simscape™ language. To calculate an accurate current-voltage (IV) curve for the array, this model takes into account the number of cells per wing, pointing angles of the solar array, shadowing, and thermal effects such as solar, planetary infrared and albedo. Performance degradation factors such as radiation, contamination, and collisions with micrometeoroids and orbital debris were also considered.

接下来，该团队使用SIMSCAPE电气组件库和使用SIMSCAPE语言开发的自定义块的标准块组合创建了锂离子电池模型。该模型解释了电池磁滞效果，温度和电池电量状态。

该团队继续使用SIMSCAPE语言，创建了一个自定义的电力负载块，以模拟航天器的推进，指导和其他系统在整个任务中打开和关闭时产生的不同负载。使用集成电源系统模型，该团队为各种任务配置文件进行了模拟。他们监视了任务和负载变化，以评估开发过程中的功率影响，模拟故障场景，包括电池故障，卡住开关以及上升和轨道阶段的太阳阵列故障。结果用于指导开发失败案件的任务机会和协议。

They also simulated numerous mission profiles to ensure that the solar arrays and batteries were sized correctly and to project how the power system would perform during hours-long eclipse scenarios. The inputs to these simulations were timelines of commanded system states and load profiles generated with MATLAB^®.

该团队使用MATLAB进行了后处理和可视化模拟结果，并根据NASA的内部电力系统模拟器为国际空间站产生的结果进行了验证。

• 开发时间减少了三分之二。“With Simscape Electrical and the Simscape language, we reduced the time needed to develop the Orion power system model by about two-thirds compared with using VBA,” says Hernandez. “Simscape is straightforward; it enables us to create custom components faster and more efficiently than with VBA.”
• 建立可重复使用的组件库。埃尔南德斯说：“我们创建了一个具有SIMSCAPE的自定义组件库，其中包括配电分配组件以及电气，热和轨道力学块。”“重用EFT-1的几个组件以进行EM-1，使我们能够对该计划进行快速的周转评估。”
• 底层编码最小化。“With Simulink and Simscape Electrical, I don’t have to write more code to numerically solve systems of equations. I build the custom blocks, connect them graphically, and let the solver do its work,” says Hernandez. “The NASA engineers I work with like the Simscape models, because the models are more intuitive than low-level code.”