Triplet Feature Fusion for Equipment Anomaly Prediction : An Open-Source Methodology Using Small Foundation Models
Abstract
Predicting equipment anomalies before they escalate into failures is a critical challenge in industrial facility management. Existing approaches rely either on hand-crafted threshold rules, which lack generalizability, or on large neural models that are impractical for on-site, air-gapped deployments. We present an industrial methodology that resolves this tension by combining open-source small foundation models into a unified 1,116-dimensional Triplet Feature Fusion pipeline. This pipeline integrates: (1) statistical features (x in ) derived from 90-day sensor histories, (2) time-series embeddings (y in ) from a LoRA-adapted IBM Granite TinyTimeMixer (TTM, 133K parameters), and (3) multilingual text embeddings (z in ) extracted from Japanese equipment master records via multilingual-e5-large. The concatenated triplet h = [x; y; z] is processed by a LightGBM classifier (< 3 MB) trained to predict anomalies at 30-, 60-, and 90-day horizons. All components use permissive open-source licenses (Apache 2.0 / MIT). The inference-time pipeline runs entirely on CPU in under 2 ms, enabling edge deployment on co-located hardware without cloud dependency. On a dataset of 64 HVAC units comprising 67,045 samples, the triplet model achieves Precision = 0.992, F1 = 0.958, and ROC-AUC = 0.998 at the 30-day horizon. Crucially, it reduces the False Positive Rate from 0.6 percent (baseline) to 0.1 percent - an 83 percent reduction attributable to equipment-type conditioning via text embedding z. Cluster analysis reveals that the embeddings align time-series signatures with distinct fault archetypes, explaining how compact multilingual representations improve discrimination without explicit categorical encoding.
Figures & tables
| Model | Hor. | Prec | Rec | F1 | AUC | FPR |
|---|---|---|---|---|---|---|
| v2-0 | 30d | .910 | .940 | .920 | .995 | 0.6% |
| 60d | .930 | .940 | .930 | .995 | 0.5% | |
| 90d | .950 | .880 | .910 | .995 | 1.1% | |
| v3-0 | 30d | .992 | .926 | .958 | .998 | 0.1% |
| 60d | .970 | .963 | .967 | .999 | 0.3% | |
| 90d | .962 | .940 | .951 | .998 | 0.4% |
| Version | Feature set | Prec (best) | Key lesson |
|---|---|---|---|
| v1.0 | Granite TS only (5 equip) | 71% (90d) | Foundation model alone is insufficient for small ; equipment-identity context is missing |
| LGB-Stat | Stats only (28-dim) | 79–87% | Hand-crafted explicit statistics provide a strong discriminative baseline |
| v2-0 | Stats + TTM (92-dim) | 91–95% | TTM embeddings capture latent temporal structure; hybrid beats any single modality |
| v3-0 | Stats + TTM + Text (1116-dim) | 96–99% | Text embeddings encode equipment-type context, suppressing FPR via type-specific decision boundaries |
| Cluster | Sensor Measurement Type | Anom. | Time series pattern signature | |
|---|---|---|---|---|
| C0 | 20 | Chilled/Cooling Water Temp | Rapid oscillation + sustained positive excursion after day 40 (heat-exchanger fouling) | |
| C1 | 5 | Mixed HVAC | Near-zero, low-variance; stable setpoint with no significant drift | |
| C2 | 5 | Mixed HVAC | Slow sinusoidal oscillation ( 0.5 ); seasonal load variation | |
| C3 | 5 | Mixed HVAC | Step-like plateaus; multi-stage setpoint controller cycling between fixed modes | |
| C4 | 7 | Main Motor Current [A] | Flat baseline with minor periodic spikes; motor within healthy band |
| Cluster | Sensor Measurement Type | Anom. | Time series pattern signature | |
|---|---|---|---|---|
| C5 | 3 | Mixed HVAC | Sparse intermittent readings at two discrete values; binary/ON-OFF sensor | |
| C6 | 5 | Mixed HVAC | Progressive upward drift across window followed by sharp spike (gradual degradation) | |
| C7 | 9 | Mixed HVAC | High-frequency noise on rising mean; classic early-warning pattern for mechanical wear | |
| C8 | 3 | Differential Pressure [Pa] | Stable, slightly negative plateau ( ); duct pressure well-controlled | |
| C9 | 6 | Operating Current [A] | Smooth near-constant trace; steady motor load over 90 days |
| Cluster | Sensor Measurement Type | Anom. | Time series pattern signature | |
|---|---|---|---|---|
| C10 | 4 | Refrigerant/System Pressure | Step-down at day 20 + sustained low-pressure plateau (refrigerant leak / valve failure) | |
| C11 | 15 | Flow Rate + Temperature | Gradually increasing negative deviation; cooling flow falls below design spec | |
| C12 | 85 | Ammeter / Diff. Pressure | Near-flat trace over 90 days; largest and most homogeneous cluster | |
| C13 | 28 | Temperature [°C] (HVAC) | Gentle sinusoidal pattern ( 0.3 ); routine diurnal/weekly cycling | |
| C14 | 14 | Temperature [°C] (sub-system) | Flatter than C13 with brief spikes; tighter sub-system control |
| Cluster | Sensor Measurement Type | Anom. | Time series pattern signature | |
|---|---|---|---|---|
| C15 | 10 | Inverter Frequency [Hz] | Step-function waveform; discrete VAV speed stages | |
| C16 | 5 | Temperature [°C] | Sustained excursion above in second half (slow-onset insulation degradation) | |
| C17 | 15 | Flow Rate + Temperature | Irregular bounded oscillation ( 0.8 ); normal demand variability | |
| C18 | 4 | Diff. Pressure / Ammeter | Low-amplitude flat signal; stable normal behaviour shared by two sensor types | |
| C19 | 4 | Mixed HVAC | Near-zero flat with single brief negative excursion; likely sensor dropout |
| Component | Model / Library | License | Role |
|---|---|---|---|
| TS encoder | IBM Granite TTM [ 7 ] | Apache 2.0 | |
| LoRA adapter | PEFT (HuggingFace) | Apache 2.0 | Fine-tuning |
| Text encoder | multilingual-e5-large [ 16 ] | MIT | |
| Classifier | LightGBM [ 17 ] | MIT | Prediction |
Anomaly Detection
Anomaly detection finds rare or unexpected patterns in data, from defective products and system faults to fraud and security threats.
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