Modeling and Control of Spacecraft with Multiple Active Pointing Ultra-Quiet Platforms

Future high-resolution space-based astronomical observation and remote sensing require space telescope with long focal length or space interferometer with long baseline. In these systems, multiple payloads will be placed over a large spacecraft structure and work in coordination to fulfill the mission tasks. However, structure flexibility and various disturbances present challenges for precision control of the payloads. In this article, each payload is placed on an active pointing ultra-quiet platform for simultaneous steering and active/passive vibration isolation, and the associated modeling and control problems are addressed. First, dynamic equations are formulated for a flexible spacecraft with
$N$
platforms. In these equations, relative motion variables are used for the platforms, so that the equations are simple yet suitable for control design and analysis. Then, two typical coordination schemes for the platforms are identified, and the corresponding control goals are defined. Finally, the controllers for both the schemes are designed based on the disturbance observer technique, and their performance, including steady-state disturbance rejection and transient-state agility, is evaluated via numerical simulation.