Control limitations from distributed sensing: theory and Extremely Large Telescope application

TL;DR

This paper analyzes how distributed sensing constraints impact feedback control performance, especially in large-scale systems like the European Extremely Large Telescope, highlighting the need to limit integral action for stability.

Contribution

It provides a theoretical framework for understanding performance bounds in distributed sensing control systems without controller restrictions, applied to large-scale telescopic systems.

Findings

Distributed sensing limits feedback performance under noise and uncertainty.

Performance bounds necessitate reducing integral action on certain modes.

Application to E-ELT mirror stabilization demonstrates practical implications.

Abstract

We investigate performance bounds for feedback control of distributed plants where the controller can be centralized (i.e. it has access to measurements from the whole plant), but sensors only measure differences between neighboring subsystem outputs. Such "distributed sensing" can be a technological necessity in applications where system size exceeds accuracy requirements by many orders of magnitude. We formulate how distributed sensing generally limits feedback performance robust to measurement noise and to model uncertainty, without assuming any controller restrictions (among others, no "distributed control" restriction). A major practical consequence is the necessity to cut down integral action on some modes. We particularize the results to spatially invariant systems and finally illustrate implications of our developments for stabilizing the segmented primary mirror of the European Extremely Large Telescope.