Initialization of linear controllers for constrained time-optimal control of the Laser Interferometer Space Antenna

Beschreibung

This dissertation was inspired by a simple problem: namely, that the low-bandwidth controllers in widespread use for the attitude control of highly stable scientific satellites respond poorly to transients in the control loop. In control terms: how can a low-bandwidth controller designed to reject high-frequency measurement noise respond to a transient in a time-optimal fashion? This work presents a novel method of controller initialization to counteract a transient in progress. This method, the eigenmode initialization, pursues time-optimal performance for a given controller and plant by attempting to suppress the slow eigenmodes of the closed-loop system; the dynamics that remain are a function of the remaining eigenmodes. The core theory has been extended to account for a number of real-world considerations, including an updated initialization in the presence of actuator bias, a bound on transient performance in the presence of plant state estimate error, and the design of controllers and reference signals to maximize the use of the available actuation authority without violating limits in the measurement signal. Building from this theoretical basis, the eigenmode initialization is applied to the drag-free and attitude control of the Laser Interferometer Space Antenna (LISA). Here, the eigenmode initialization is shown to provide reductions in both settling time and overshoot (factors of 2 and 5) when applied to transients expected in the scientific operations of LISA. These results are complemented by a Monte Carlo campaign conducted with the support of Airbus Defence and Space GmbH, further demonstrating the eigenmode initialization as a simple and effective technique, fully compatible with the attitude control needs of a highly stable scientific satellite.

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Adam Vigneron

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laser interferometer space antenna (LISA) mission linear control controller initialization time-optimal control drag-free attitude control

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