스크램제트 흡입구 격리부 충격파열(Shock Train) 거동 & 1,000Hz 0-Alloc C# 엔진 언스타트(Unstart) 방지 서보 제어기

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace ZeliDesk.Stem.ScramjetControl
{
    /// <summary>
    /// 격리부 8개 채널 벽면 정압 어레이 (스택 할당 0-Alloc)
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct IsolatorPressureArray
    {
        public readonly double P0; // 흡입구 측 (최상류)
        public readonly double P1;
        public readonly double P2;
        public readonly double P3;
        public readonly double P4;
        public readonly double P5;
        public readonly double P6;
        public readonly double P7; // 연소기 측 (최하류)

        public IsolatorPressureArray(double p0, double p1, double p2, double p3, double p4, double p5, double p6, double p7)
        {
            P0 = p0; P1 = p1; P2 = p2; P3 = p3; P4 = p4; P5 = p5; P6 = p6; P7 = p7;
        }
    }

    /// <summary>
    /// 언스타트 방지 액추에이터 제어 명령
    /// </summary>
    public ref struct ScramjetActuatorCommand
    {
        public double BleedValveOpeningRatio; // 0.0 ~ 1.0
        public double FuelFlowReductionRatio;  // 0.0 ~ 0.5
        public bool DangerAlert;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public ScramjetActuatorCommand(double bleed, double fuelReduct, bool alert)
        {
            BleedValveOpeningRatio = bleed;
            FuelFlowReductionRatio = fuelReduct;
            DangerAlert = alert;
        }
    }

    /// <summary>
    /// 1,000Hz 무할당 스크램제트 충격파 제어 서보 엔진
    /// </summary>
    public ref struct ScramjetUnstartPreventionEngine
    {
        private const double PressureThresholdRatio = 1.65; // 정상 유동 대비 충격파 감지 압력비
        private const double InletMarginLimitPosition = 0.20; // 흡입구로부터의 최소 마진 거리 (정규화 좌표)

        private double _filteredShockPosition;
        private double _shockVelocity;
        private double _prevShockPosition;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ExecuteControlCycle(
            in IsolatorPressureArray pressureArray,
            double nominalInletPressureKPa,
            double flightMachNumber,
            out ScramjetActuatorCommand actuatorCommand,
            out double currentShockPositionNormalized,
            out double unstartMarginPercent)
        {
            // 1. 압력 프로파일로부터 충격파 선단 위치 탐색 (0.0: 흡입구, 1.0: 연소기)
            double shockPos = 1.0;
            double baselineP = nominalInletPressureKPa;

            if (pressureArray.P0 > baselineP * PressureThresholdRatio) shockPos = 0.00;
            else if (pressureArray.P1 > baselineP * PressureThresholdRatio) shockPos = 0.14;
            else if (pressureArray.P2 > baselineP * PressureThresholdRatio) shockPos = 0.28;
            else if (pressureArray.P3 > baselineP * PressureThresholdRatio) shockPos = 0.42;
            else if (pressureArray.P4 > baselineP * PressureThresholdRatio) shockPos = 0.57;
            else if (pressureArray.P5 > baselineP * PressureThresholdRatio) shockPos = 0.71;
            else if (pressureArray.P6 > baselineP * PressureThresholdRatio) shockPos = 0.85;
            else if (pressureArray.P7 > baselineP * PressureThresholdRatio) shockPos = 1.00;

            // 2. 저역 통과 필터 및 충격파 상류 이동 속도 계산 (dt = 0.001s)
            _shockVelocity = (shockPos - _prevShockPosition) / 0.001; // 양수: 하류 후퇴, 음수: 상류 돌진
            _prevShockPosition = shockPos;

            _filteredShockPosition = 0.85 * _filteredShockPosition + 0.15 * shockPos;
            currentShockPositionNormalized = _filteredShockPosition;

            // 3. 언스타트 마진 산출 (%)
            unstartMarginPercent = Math.Clamp((currentShockPositionNormalized - InletMarginLimitPosition) / (1.0 - InletMarginLimitPosition) * 100.0, 0.0, 100.0);

            // 4. 비상 블리드 개방 및 연료 컷오프 서보 로직
            double bleedCmd = 0.0;
            double fuelCutCmd = 0.0;
            bool alert = false;

            if (unstartMarginPercent < 40.0 || _shockVelocity < -15.0) // 충격파가 흡입구로 급격 전진 시
            {
                alert = true;
                double severity = (40.0 - unstartMarginPercent) / 40.0;
                bleedCmd = Math.Clamp(0.3 + 0.7 * severity - 0.02 * _shockVelocity, 0.0, 1.0);
                fuelCutCmd = Math.Clamp(0.15 * severity, 0.0, 0.45);
            }
            else
            {
                bleedCmd = 0.0;
                fuelCutCmd = 0.0;
            }

            actuatorCommand = new ScramjetActuatorCommand(bleedCmd, fuelCutCmd, alert);
        }
    }
}