Tuning the MAPS Adaptive Secondary Mirror: Actuator Control, PID Tuning, Power Spectra and Failure Diagnosis

TL;DR

This paper details the tuning and control of the MAPS adaptive secondary mirror at the MMT telescope, focusing on actuator control, PID tuning, power spectra analysis, and failure diagnosis to enhance performance.

Contribution

It introduces a comprehensive approach to actuator control, PID tuning, and failure diagnosis for the MAPS adaptive secondary mirror, improving its response and operational capabilities.

Findings

Reduced mirror latency

Increased operational mirror modes

Enhanced image PSF quality

Abstract

The MMT Adaptive optics exoPlanet characterization System (MAPS) is currently in its engineering phase, operating on-sky at the MMT Telescope on Mt. Hopkins in southern Arizona. The MAPS Adaptive Secondary Mirror's actuators are controlled by a closed loop modified PID control law and an open loop feed-forward law, which in combination allows for faster actuator response time. An essential element of achieving the secondary's performance goals involves the process of PID gain tuning. To start, we briefly discuss the design of the MAPS ASM and its actuators. We then describe the actuator positional control system and control law. Next, we discuss a few of the issues that make ASM tuning difficult. We then outline our initial attempts at tuning the actuator controllers and discuss the use of actuator positional power spectra for both tuning and determining the health and failure states of individual actuators. We conclude by presenting the results of our latest round of tuning configuration trials, which have been successful at decreasing mirror latency, increasing operational mirror modes and improving image PSF.