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A Physics-Informed MobileNetV2 Framework for Thermal Infrared Gas Classification: Combining Thermodynamic Input Features and Loss-Level Physics Penalization

Olumurewa KO, Adeniji OO, Oluwagbemi JB

2026

Abstract

Abstract Deep-learning models for thermal-infrared gas classification have thus far treated thermal images as ordinary photographs, discarding the fact that every pixel contains information on physically calibrated temperature governed by fixed thermodynamic law. This paper presents a Physics-Informed Machine Learning (PIML) system that classifies gas environments from thermal-infrared images using both physics-grounded input features and a physics-penalized training objective. Rather than utilizing the three-channel RGB representation used in all prior work on the MultimodalGasData thermal-image subset, in this work, each image is converted into a six-channel tensor comprising temperature-normalized RGB channels, horizontal and vertical thermal-gradient maps derived from Fourier's law of heat conduction via the Sobel operator, and a local temperature-anomaly map obtained by neighborhood-mean subtraction. A MobileNetV2 backbone with a custom input-projection block is trained in two phases; frozen-backbone feature adaptation followed by fine-tuning of the top thirty backbone layers — under a physics-informed loss function that penalizes confident gas predictions in thermally flat, physically implausible image regions. The resulting model attains 94.80% test accuracy and 96.67% best validation accuracy across four classes (No Gas, Perfume, Smoke, Mixture), with a Mixture-class F1-score of 99.58% and zero false Mixture alarms across 722 non-Mixture test images. Occlusion-based…

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