Computational Modeling and Learning-Based Adaptive Control of Solid-Fuel Ramjets

TL;DR

This paper develops a computational and learning-based adaptive control framework for solid-fuel ramjets, combining CFD modeling with RCAC to achieve robust thrust regulation amid complex nonlinearities and multi-physics interactions.

Contribution

It introduces a novel integration of CFD modeling with a retrospective cost adaptive control approach for SFRJs, enabling effective thrust regulation without relying on simplified models.

Findings

RCAC controller accurately regulates thrust in simulations.

The framework is robust to variations in operating conditions.

Demonstrates potential for reliable SFRJ operation in future applications.

Abstract

Solid-fuel ramjets offer a compact, energy-dense propulsion option for long-range, high-speed flight but pose significant challenges for thrust regulation due to strong nonlinearities, limited actuation authority, and complex multi-physics coupling between fuel regression, combustion, and compressible flow. This paper presents a computational and control framework that combines a computational fluid dynamics model of an SFRJ with a learning-based adaptive control approach. A CFD model incorporating heat addition was developed to characterize thrust response, establish the operational envelope, and identify the onset of inlet unstart. An adaptive proportional-integral controller, updated online using the retrospective cost adaptive control (RCAC) algorithm, was then applied to regulate thrust. Closed-loop simulations demonstrate that the RCAC-based controller achieves accurate thrust regulation under both static and dynamic operating conditions, while remaining robust to variations in commands, hyperparameters, and inlet states. The results highlight the suitability of RCAC for SFRJ control, where accurate reduced-order models are challenging to obtain, and underscore the potential of learning-based adaptive control to enable robust and reliable operation of SFRJs in future air-breathing propulsion applications.