Simple yet Effective Anti-windup Techniques for Amplitude and Rate Saturation: An Autonomous Underwater Vehicle Case Study

TL;DR

This paper revisits classical anti-windup techniques, proposing modifications to PID and LQI controllers, demonstrating their effectiveness in AUV yaw control with performance comparable to constrained MPC.

Contribution

It introduces simple modifications to classical anti-windup schemes for amplitude and rate saturation, showing they can perform well in practical AUV control scenarios.

Findings

Classical anti-windup methods can effectively handle A extbackslash{}&RSat in AUV control.

Modified PID and LQI controllers achieve performance comparable to constrained MPC.

Results suggest simple anti-windup schemes are viable for practical engineering applications.

Abstract

Actuator amplitude and rate saturation (A\&RSat), together with their consequent windup problem, have long been recognised as challenges in control systems. Anti-windup (AW) solutions have been developed over the past decades, which can generally be categorised into two main groups: classical and modern anti-windup (CAW and MAW) approaches. Classical methods have provided simple and effective results, mainly addressing amplitude saturation. In contrast, modern approaches offer powerful and theoretically sound solutions capable of handling both amplitude and rate saturations. However, MAW's derivation process often imposes restrictive conditions and can be complex to apply in practical engineering problems. Nevertheless, the literature has paid limited attention (if not entirely ignored) to the potential of simple yet effective CAW schemes that can operate in the presence of both A\&RSat elements. This paper revisits this issue and proposes modifications to two well-known controllers: PID and LQI. The obtained results, benchmarked on the REMUS AUV yaw control problem and compared with constrained MPC, indicate that these classical techniques can still provide simple yet effective solutions with comparable performance, at least for SISO systems. These findings may stimulate further research into solutions that achieve comparable performance with only one (or a limited number of) additional tuning parameters and straightforward implementation.