Towards new servo control algorithms at the TNG telescope

TL;DR

This paper discusses the overhaul of the servo control algorithms for the TNG telescope, including re-identification and redesign of control filters, to improve performance while maintaining continuous operation during hardware upgrades.

Contribution

It presents a comprehensive review and update of the TNG telescope's servo control schemes, including plant re-identification and control filter redesign, during hardware replacement.

Findings

Preliminary results show improved control performance.

Successful implementation without disrupting telescope operations.

Framework for future control system enhancements.

Abstract

The servo control algorithms of the TNG, developed in the nineties, have been working for more than 20 years with no major updates. The original hardware was based on a VME-bus based platform running a real time operating system, a rather popular choice for similar applications at the time. Recently, the obsolescence of the hardware and the lack of spares pushed the observatory towards a complete replacement of the electronics that is now being implemented in steps, respecting the basic requirement of never stopping the observatory night operations. Within the framework of this major hardware work, we are taking the opportunity to review and update the existing control schemes. This servo control update, crucial for the telescope performance, envisages a new study from scratch of the controlled plant, including a re-identification of the main axes transfer functions and a re-design of the control filters in the two nested position and speed loops. The ongoing work is described, including preliminary results in the case study of the azimuth axis and our plans for possible further improvements.