---
title: 3D Pump Curve Architecture
created: 2026-04-07
updated: 2026-04-07
status: proven
tags: [predict, curves, interpolation, rotatingMachine]
sources: [nodes/generalFunctions/src/predict/predict_class.js, nodes/rotatingMachine/src/specificClass.js]
---

# 3D Pump Curve Prediction

## Data Structure
A family of 2D curves indexed by pressure (f-dimension):
- **X-axis**: control position (0-100%)
- **Y-axis**: flow (nq) or power (np) in canonical units
- **F-dimension**: pressure (Pa) — the 3rd dimension

Raw curves are in curve units (m3/h, kW, mbar). `_normalizeMachineCurve()` converts to canonical (m3/s, W, Pa).

## Interpolation
Monotonic cubic spline (Fritsch-Carlson) in both dimensions:
- **X-Y splines**: at each discrete pressure level
- **F-splines**: across pressure levels for intermediate pressure interpolation

## Prediction Flow
```
predict.y(x):
  1. Clamp x to [currentFxyXMin, currentFxyXMax]
  2. Normalize x to [normMin, normMax]
  3. Evaluate spline at normalized x for current fDimension
  4. Return y in canonical units (m3/s or W)
```

## Unit Conversion Chain
```
Raw curve (m3/h, kW, mbar)
  → _normalizeMachineCurve → canonical (m3/s, W, Pa)
  → predict class → canonical output
  → MeasurementContainer.getCurrentValue(outputUnit) → output units
```

No double-conversion. Clean separation: specificClass handles units, predict handles normalization/interpolation.

## Three Predict Instances per Machine
- `predictFlow`: control % → flow (nq curve)
- `predictPower`: control % → power (np curve)
- `predictCtrl`: flow → control % (reversed nq curve)

## Boundary Behavior
- Below/above curve X range: flat extrapolation (clamped)
- Below/above f-dimension range: clamped to min/max pressure level

## Performance
- `y(x)`: O(log n), effectively O(1) for 5-10 data points
- `buildAllFxyCurves`: sub-10ms for typical curves
- Full caching of normalized curves, splines, and calculated curves