NCog — Normalized Center of Gravity

What It Is

NCog is a 0-1 value indicating where on its flow range a pump operates most efficiently. Computed per tick from the current pressure slice of the 3D pump curve.

BEP_flow = minFlow + (maxFlow - minFlow) * NCog

How It's Computed

Pressure sensors update → getMeasuredPressure() computes differential
fDimension locks the 2D slice at current system pressure
calcCog() computes Q/P (specific flow) across the curve
Peak Q/P index → NCog = (flowAtPeak - flowMin) / (flowMax - flowMin)

When NCog is Meaningful

NCog requires differential pressure (upstream + downstream). With only one pressure sensor, fDimension is the raw sensor value (too high), producing a monotonic Q/P curve and NCog = 0.

Condition	NCog for H05K	NCog for C5
ΔP = 400 mbar	0.333	0.355
ΔP = 1000 mbar	0.000	0.000
ΔP = 1500 mbar	0.135	0.000
ΔP = 2000 mbar	0.351	0.000

Why NCog = 0 Happens

For variable-speed centrifugal pumps, Q/P is monotonically decreasing when the affinity laws dominate (P ∝ Q³). At certain pressure levels, the spline interpolation preserves this monotonicity and the peak is always at index 0 (minimum flow).

How the machineGroupControl Uses NCog

The BEP-Gravitation algorithm seeds each pump at its BEP flow, then redistributes using slope-based weights + marginal-cost refinement. Even when NCog = 0, the slope redistribution produces near-optimal results because it uses actual power evaluations.

[!warning] Disproven: NCog as proportional weight Using NCog directly as a flow-distribution weight (flow = NCog/totalNCog * Qd) is wrong. It starves pumps with NCog = 0 and overloads high-NCog pumps. See calcBestCombination in machineGroupControl.

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