Lempel-Ziv Complexity Methods for Fault Diagnosis in Mechanical Systems
Summary
Lempel–Ziv complexity (LZC) is an information-theoretic measure that quantifies the irregularity and diversity of patterns in a binary or symbolic representation of a time series. In mechanical‐system fault diagnosis, vibration or acoustic signals affected by bearing faults, gear damage or misalignments exhibit non-stationary, nonlinear characteristics often masked by noise. LZC captures the emergence of new subsequences as faults evolve, providing a sensitive indicator of dynamic changes. To enhance feature extraction, single-scale LZC has been extended into multiscale and hierarchical frameworks. Multiscale variants segment the signal at multiple resolutions, revealing fault signatures across low- and high-frequency bands, while hierarchical LZC integrates information from successive decompositions. In many applications, LZC is combined with signal‐processing techniques such as wavelet or variational mode decomposition to isolate fault-related components and suppress interference. The resulting LZC indices serve as inputs to pattern classifiers or trend-analysis tools, enabling early detection, severity assessment and quantitative trend diagnosis. Recent advances focus on optimising parameter selection, improving noise immunity and fusing LZC with complementary complexity measures to deliver robust, real-time monitoring solutions in wind turbines, rolling bearings and general rotating machinery.
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Lempel-Ziv Complexity Methods for Fault Diagnosis in Mechanical Systems publication trend
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Technical terms
Lempel–Ziv complexity (LZC): A metric that counts the number of distinct substrings in a symbolic sequence, reflecting its randomness and complexity.
Multiscale analysis: A procedure that evaluates a signal at various time or frequency scales to capture features that manifest at different resolutions.
Variational mode decomposition (VMD): An adaptive signal decomposition technique that separates a time series into band-limited intrinsic mode functions based on constrained variational optimisation.
Hierarchical complexity: A framework that organises decomposed signal components into levels, calculating complexity measures at each level to capture multi-resolution fault characteristics.
References
- Approach to the Quantitative Diagnosis of Rolling Bearings Based on Optimized VMD and Lempel–Ziv Complexity under Varying Conditions. Sensors (2023).
- Application of Generalized Composite Multiscale Lempel–Ziv Complexity in Identifying Wind Turbine Gearbox Faults. Entropy (2021).
- Intelligent Fault Diagnosis of Rotating Machinery Using Hierarchical Lempel-Ziv Complexity. Applied Sciences (2020).
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