Security Risks in Machining Process Monitoring: Sequence-to-Sequence Learning for Reconstruction of CNC Axis Positions

TL;DR

This work demonstrates that sequence-to-sequence machine learning models can overcome non-idealities and enable reconstruction of CNC axis and tool positions from industrial condition monitoring accelerometer data, and is the first study demonstrating learning-based CNC position reconstruction from industrial condition monitoring accelerometer data.

Abstract

Accelerometer-based process monitoring is widely deployed in modern machining systems. When mounted on moving machine components, such sensors implicitly capture kinematic information related to machine motion and tool trajectories. If this information can be reconstructed, condition monitoring data constitutes a severe security threat, particularly for retrofitted or weakly protected sensor systems. Classical signal processing approaches are infeasible for position reconstruction from broadband accelerometer signals due to sensor- and process-specific non-idealities, like noise or sensor placement effects. In this work, we demonstrate that sequence-to-sequence machine learning models can overcome these non-idealities and enable reconstruction of CNC axis and tool positions. Our approach employs LSTM-based sequence-to-sequence models and is evaluated on an industrial milling dataset. We show that learning-based models reduce the reconstruction error by up to 98% for low complexity motion profiles and by up to 85% for complex machining sequences compared to double integration. Furthermore, key geometric characteristics of tool trajectories and workpiece-related motion features are preserved. To the best of our knowledge, this is the first study demonstrating learning-based CNC position reconstruction from industrial condition monitoring accelerometer data.

Figures (5)

• Figure 1: State-of-the-art digital signal processing approach to improve double integration for position estimation b6.
• Figure 2: Conceptual information extraction pipeline illustrating how process monitoring data can be transformed into higher-level representations, potentially leading to unintended leakage of sensitive process and design information.
• Figure 3: Overview of the two evaluated position reconstruction approaches.
• Figure 4: Exemplary milling sequence illustrating the relationship between machining phases and the four evaluated prediction scenarios. Only the $x$-axis components of the acceleration and ground-truth position signals are shown.
• Figure 5: Qualitative trajectory reconstruction for a representative test sequence.