Dynamic PID loop control

TL;DR

This paper introduces a self-optimizing PID control method with time-delay compensation to stabilize cryogenic liquid levels in Fermilab's SRF cryostats, reducing oscillations caused by long response delays.

Contribution

It proposes a novel self-optimal PID and time-delay control approach specifically designed for cryogenic liquid level regulation in superconducting RF systems.

Findings

Significant reduction in cryostat liquid level oscillations.

Improved stability of cryogenic control system.

Enhanced regulation performance in long-delay systems.

Abstract

The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters' oscillation.