Large Space Optics Using System Identification

Temperature control of space optics is a relatively new field. The main components of a temperature control loop are spatially distributed temperature heaters, controllers, and spatially distributed temperature sensors (thermistors or thermocouples).nbsp;Traditional Proportional Integral Derivative (PID) control approaches do not achieve optimal system performance when there are significant delays between the control inputs or disturbances and observed state variables, and when the system is of higher order.nbsp;PID controllers often cannot achieve optimal energy consumption, as well as high control performance and accuracy. Besides these challenges, optimal tuning of PID controllers for systems with many inputs and outputs (such as the thermal control system for space telescopes) is a highly nontrivial and still active research problem.nbsp;Recently, model-based control approaches developed using a lumped model of temperature dynamics were developed.nbsp; These lumped model representations may be too simplistic to produce accurate results and do not include the coupling between the absorbed external flux and the system dynamics.System identification (SID) uses statistical methods to build mathematical models of dynamical systems from measured data.nbsp; It is the basis for modern data-driven control systems, in which concepts of system identification are integrated into the controller design laying the foundations for formal controller optimality proofs.Our proposed innovation is an active thermal control using system identification (ATC-SID) methodnbsp;to enable a:Large mirror (gt;4-meter diameter ndash; monolithic or segmented) with diffraction limited performance at wavelengths less than 500 nm (lt; 40 nm RMS wavefront error, WFE).Total cost of the primary mirror below $100M.nbsp;Our ATC-SID innovation will enable thermal control (lt; 1 mK) to reduce wavefront stability to lt; 10 pm RMS per 10 min).