breakpilot-compliance/ai-compliance-sdk/internal/iace/fmea_data_sources.go

package iace

// Open, public-domain methodology anchors for the auto-FMEA (P1 of the FMEA
// build plan). Every scale here is anchored on US-Government PUBLIC-DOMAIN
// sources — MIL-STD-882E (system-safety severity/probability) and MIL-STD-1629A
// (FMECA criticality). The 1-10 projection is BreakPilot's OWN scale; NO
// AIAG-VDA / SAE J1739 / IEC 60812 table is reproduced (those are copyrighted).
// Failure-rate (λ) and failure-mode-ratio (α) values come later from NPRD-91 /
// FMD-91 (RAC, public domain). See project_fmea_build_plan / opensource-fmea-sources.

// FMEADataSourcesNote is the audit/attribution line for the FMEA methodology.
const FMEADataSourcesNote = "FMEA-Methodik + Skalen verankert an US-Gov Public Domain " +
	"(MIL-STD-1629A FMECA-Kritikalität, MIL-STD-882E Severity/Probability, NASA RCM). " +
	"Ausfallraten/Mode-Verteilungen aus NPRD-91/FMD-91 (RAC, Public Domain). " +
	"Das 1-10-Mapping ist BreakPilot-eigen; KEINE AIAG-VDA/SAE/IEC-Tabelle reproduziert."

// FMEASeverityBand maps a MIL-STD-882E Table-I severity CATEGORY to our 1-10 S.
type FMEASeverityBand struct {
	Category string `json:"category"` // "I".."IV"
	LabelDE  string `json:"label_de"`
	Desc     string `json:"desc"`     // public-domain threshold (injury/$)
	Severity int    `json:"severity"` // our 1-10 projection
}

// MILStd882Severity returns the four MIL-STD-882E severity categories, ordered
// most→least severe, with our 1-10 projection. (882E is US-Gov public domain.)
func MILStd882Severity() []FMEASeverityBand {
	return []FMEASeverityBand{
		{Category: "I", LabelDE: "Katastrophal", Desc: "Tod, dauerhafte Vollinvalidität oder irreversibler schwerer Umweltschaden", Severity: 10},
		{Category: "II", LabelDE: "Kritisch", Desc: "Dauerhafte Teilinvalidität oder Krankenhausaufenthalt mehrerer Personen", Severity: 7},
		{Category: "III", LabelDE: "Marginal", Desc: "Verletzung/Erkrankung mit Ausfalltag(en)", Severity: 4},
		{Category: "IV", LabelDE: "Vernachlässigbar", Desc: "Geringfügige Verletzung ohne Ausfalltag", Severity: 2},
	}
}

// FMEAOccurrenceBand maps a MIL-STD-882E Table-II probability LEVEL to our 1-10
// O. LambdaMax is the upper bound (failures per operating hour) we use to bin a
// computed mode rate; the per-hour calibration is ours, anchored on 882E order.
type FMEAOccurrenceBand struct {
	Level      string  `json:"level"` // "A".."F"
	LabelDE    string  `json:"label_de"`
	LambdaMax  float64 `json:"lambda_max"` // inclusive upper bound, /h (0 ⇒ eliminated)
	Occurrence int     `json:"occurrence"` // our 1-10 projection
}

// MILStd882Probability returns the six MIL-STD-882E probability levels (individual
// item), ordered most→least frequent, with our 1-10 projection + a per-hour
// failure-rate band used by OccurrenceFromRate.
func MILStd882Probability() []FMEAOccurrenceBand {
	return []FMEAOccurrenceBand{
		{Level: "A", LabelDE: "Häufig", LambdaMax: 1, Occurrence: 10},           // ≥ 1e-1
		{Level: "B", LabelDE: "Wahrscheinlich", LambdaMax: 1e-1, Occurrence: 8}, // 1e-2 .. 1e-1
		{Level: "C", LabelDE: "Gelegentlich", LambdaMax: 1e-2, Occurrence: 6},   // 1e-3 .. 1e-2
		{Level: "D", LabelDE: "Selten", LambdaMax: 1e-3, Occurrence: 4},         // 1e-6 .. 1e-3
		{Level: "E", LabelDE: "Unwahrscheinlich", LambdaMax: 1e-6, Occurrence: 2},
		{Level: "F", LabelDE: "Ausgeschlossen", LambdaMax: 0, Occurrence: 1},
	}
}

// OccurrenceFromRate maps a mode failure rate (λp·α, failures per operating hour)
// onto the 1-10 occurrence axis via the MIL-STD-882E probability bands. A rate
// ≤ 0 is "eliminated" (1); anything ≥ 0.1/h saturates at "frequent" (10).
func OccurrenceFromRate(modeRatePerHour float64) int {
	if modeRatePerHour <= 0 {
		return 1
	}
	bands := MILStd882Probability()
	// bands[0] (A) has the highest threshold; walk most→least frequent and take
	// the first band whose lower edge the rate clears.
	for i := 0; i < len(bands)-1; i++ {
		lowerEdge := bands[i+1].LambdaMax // edge between band i and i+1
		if modeRatePerHour > lowerEdge {
			return bands[i].Occurrence
		}
	}
	return bands[len(bands)-2].Occurrence // E (improbable) for tiny positive rates
}

// SeverityForCategory returns our 1-10 severity for a MIL-STD-882E category
// ("I".."IV"); 0 if unknown.
func SeverityForCategory(category string) int {
	for _, b := range MILStd882Severity() {
		if b.Category == category {
			return b.Severity
		}
	}
	return 0
}

// CriticalityCm computes the MIL-STD-1629A modal criticality
// Cm = λp · α · β · t, where λp = part failure rate (/h), α = failure-mode ratio
// (fraction of part failures in this mode), β = conditional probability the mode
// produces the analysed effect, t = operating hours. Fully public-domain method.
func CriticalityCm(lambdaP, alpha, beta, operatingHours float64) float64 {
	if lambdaP < 0 || alpha < 0 || beta < 0 || operatingHours < 0 {
		return 0
	}
	return lambdaP * alpha * beta * operatingHours
}