Separable contextual graph neural networks to identify tailgating-oriented traffic congestion

Abstract

Identifying largescale traffic congestion with thousands of robots is a complicated task involving structured-data graphical modeling, and it has recently gained more research attention. This study aims to model traffic metrics that exhibit negative correlations in specific spatiotemporal contexts of automated material handling systems in semiconductor manufacturing. Numerous studies have focused on detecting vehicle congestion using multivariate time-series data. However, they faced challenges regarding the understanding of the complex graph structural joint spatiotemporal dynamics of the traffic rails. Existing methods fail to distinguish between congestion caused by high traffic volumes and nondisruptive delivery robot operations, such as parking and hoisting. This study introduces a novel approach to detect tailgating-oriented congestion using separable contextual graph neural networks (SC-GNNs). The proposed method employs deviation-based anomaly detection with attentive GNNs to capture spatial correlations and temporal dependencies. SC-GNNs were proposed for dual metrics with distinct characteristics, and dynamic thresholds were applied for each GNN to ensure reliable and interpretable anomaly detection. To demonstrate the outperformance of the proposed method, we conducted simulation experiments via a high-fidelity simulator similar to actual semiconductor fabrication. The experimental results showed that our method achieved both a 36% reduction in the false positive rate and a 32% decrease in the equal error rate compared to the best performance of existing state-of-the-art anomaly detection models. Overall, the proposed approach significantly improved the accuracy and interpretability of anomaly detection in multivariate time series, particularly effective in the context of identifying anomalies related to traffic congestion tailgating.