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Documents authored by Muehlburger, Herbert

Document
DOI: 10.4230/OASIcs.DX.2025.12
GEMMA-FD: Zero-Shot Fault Detection in Heat Pumps Using Multimodal Language Models

Authors: Herbert Muehlburger and Franz Wotawa

Published in: OASIcs, Volume 136, 36th International Conference on Principles of Diagnosis and Resilient Systems (DX 2025)

Abstract
Fault detection in heating systems is critical for ensuring energy efficiency and operational reliability. Traditional approaches rely on labeled fault data and expert-defined rules, which are often unavailable or costly to obtain. We introduce GEMMA-FD (GEMMA for Fault Detection), a novel zero-shot framework for fault detection in heat pumps that leverages large language models (LLMs) without requiring labeled anomalies or predefined fault signatures. Our method transforms multivariate sensor time series into structured natural language prompts and augments them with visual features, such as line plots of key variables, to facilitate multimodal reasoning. Using GEMMA-3, an open-weight multimodal LLM, we classify heat pump system states as either normal or faulty. Experiments on a real-world heat pump dataset show that GEMMA-FD can identify unseen faults with reasonable precision, although its performance remains lower than a supervised XGBoost baseline trained on the same prompts. Specifically, GEMMA-FD achieves a macro-F1 score of 0.252, compared to 0.69 for XGBoost, underscoring the trade-off between generalization and targeted accuracy. Nevertheless, GEMMA-FD demonstrates the potential of foundation models for interpretable, multilingual fault detection in cyber-physical systems, while highlighting the need for prompt engineering, few-shot augmentation, and multimodal inputs to improve the classification of rare and complex fault types.
Cite as

Herbert Muehlburger and Franz Wotawa. GEMMA-FD: Zero-Shot Fault Detection in Heat Pumps Using Multimodal Language Models. In 36th International Conference on Principles of Diagnosis and Resilient Systems (DX 2025). Open Access Series in Informatics (OASIcs), Volume 136, pp. 12:1-12:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{muehlburger_et_al:OASIcs.DX.2025.12,
  author =	{Muehlburger, Herbert and Wotawa, Franz},
  title =	{{GEMMA-FD: Zero-Shot Fault Detection in Heat Pumps Using Multimodal Language Models}},
  booktitle =	{36th International Conference on Principles of Diagnosis and Resilient Systems (DX 2025)},
  pages =	{12:1--12:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-394-2},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{136},
  editor =	{Quinones-Grueiro, Marcos and Biswas, Gautam and Pill, Ingo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.DX.2025.12},
  URN =		{urn:nbn:de:0030-drops-248015},
  doi =		{10.4230/OASIcs.DX.2025.12},
  annote =	{Keywords: fault detection, anomaly detection, cyber-physical systems, HVAC, heat pumps, energy systems, large language models, zero-shot learning, open-weight LLMs, interpretable AI, multimodal prompts, smart energy}
}
Document
Short Paper
DOI: 10.4230/OASIcs.DX.2024.25
FLEX: Fault Localization and Explanation Using Open-Source Large Language Models in Powertrain Systems (Short Paper)

Authors: Herbert Muehlburger and Franz Wotawa

Published in: OASIcs, Volume 125, 35th International Conference on Principles of Diagnosis and Resilient Systems (DX 2024)

Abstract
Cyber-physical systems (CPS) are critical to modern infrastructure, but are vulnerable to faults and anomalies that threaten their operational safety. In this work, we evaluate the use of open-source Large Language Models (LLMs), such as Mistral 7B, Llama3.1:8b-instruct-fp16, and others to detect anomalies in two distinct datasets: battery management and powertrain systems. Our methodology utilises retrieval-augmented generation (RAG) techniques, incorporating a novel two-step process where LLMs first infer operational rules from normal behavior before applying these rules for fault detection. During the experiments, we found that the original prompt design yielded strong results for the battery dataset but required modification for the powertrain dataset to improve performance. The adjusted prompt, which emphasises rule inference, significantly improved anomaly detection for the powertrain dataset. Experimental results show that models like Mistral 7B achieved F1-scores up to 0.99, while Llama3.1:8b-instruct-fp16 and Gemma 2 reached perfect F1-scores of 1.0 in complex scenarios. These findings demonstrate the impact of effective prompt design and rule inference in improving LLM-based fault detection for CPS, contributing to increased operational resilience.
Cite as

Herbert Muehlburger and Franz Wotawa. FLEX: Fault Localization and Explanation Using Open-Source Large Language Models in Powertrain Systems (Short Paper). In 35th International Conference on Principles of Diagnosis and Resilient Systems (DX 2024). Open Access Series in Informatics (OASIcs), Volume 125, pp. 25:1-25:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{muehlburger_et_al:OASIcs.DX.2024.25,
  author =	{Muehlburger, Herbert and Wotawa, Franz},
  title =	{{FLEX: Fault Localization and Explanation Using Open-Source Large Language Models in Powertrain Systems}},
  booktitle =	{35th International Conference on Principles of Diagnosis and Resilient Systems (DX 2024)},
  pages =	{25:1--25:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-356-0},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{125},
  editor =	{Pill, Ingo and Natan, Avraham and Wotawa, Franz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.DX.2024.25},
  URN =		{urn:nbn:de:0030-drops-221170},
  doi =		{10.4230/OASIcs.DX.2024.25},
  annote =	{Keywords: Fault detection, anomaly detection, powertrain systems, large language models, open-source LLMs}
}
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