SIM-Planet Quest Interferometer Real-time Control System Architecture

摘要

This paper presents a top-level architectural overview of the instrument real-time control system currently under development at JPL for the SIM-Planet Quest interferometer. The control system must meet challenging requirements for providing milliarcsecond class pointing and nanometer class delay-line control performance while tracking science stars as dim as 20th visual magnitude. The driving functional requirements call for a three-interferometer system that also serves as an attitude sensing and tracking system. Due to the dim science requirements and complicated control initialization processes, the control system is architectured using complex estimators, multiloop feedforward signals, and distributed computational infrastructure. Control objectives and requirements are presented and the necessary control sensors and actuators are discussed. Initialization of the interferometer control system is explained, including processes for target star search, acquisition, and tracking. The nominal tracking control modes are then presented, including incorporation of pathlength and angle feedforward signals. The estimation architecture is explained next including its role in generating the necessary feedforward signals. The resulting overall algorithm structure and implementation using distributed processors on a ring-bus architecture is also briefly discussed.