Split PID control: two sensors can be better than one

TL;DR

This paper proposes a split-PID control method using two sensors to improve regulation performance by balancing lag and offset issues inherent in traditional single-sensor PID control.

Contribution

It introduces the split-PID algorithm that assigns different control terms to two sensors, enhancing control bandwidth and accuracy over traditional PID methods.

Findings

Split-PID outperforms traditional PID in experiments.

Using two sensors reduces offset and drift issues.

Enhanced control bandwidth achieved with split-PID.

Abstract

The traditional proportional-integral-derivative (PID) algorithm for regulation suffers from a tradeoff: placing the sensor near the sample being regulated ensures that its steady-state temperature matches the desired setpoint. However, the propagation delay (lag) between heater and sample can limit the control bandwidth. Moving the sensor closer to the heater reduces the lag and increases the bandwidth but introduces offsets and drifts into the temperature of the sample. Here, we explore the consequences of using two probes---one near the heater, one near the sample---and assigning the integral term to the sample probe and the other terms to the heater probe. The \textit{split-PID} algorithm can outperform PID control loops based on one sensor.