AIDT 온디바이스 STEM 방사광 X선 나노프로브 주사 나노회절(Scanning Nano-XRD) 격자 변형률(Strain) 매핑 및 빔 위치 피에조 피드백 서보 제어기

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.Synchrotron.NanoXRD
{
    /// <summary>
    /// 2차원 검출기 브래그 회절 피크 및 빔 위치 계측 상태
    /// </summary>
    public readonly ref struct BraggPeakTelemetryState
    {
        public readonly double PeakPixelU;        // 검출기 U축 피크 중심 [pixel]
        public readonly double PeakPixelV;        // 검출기 V축 피크 중심 [pixel]
        public readonly double BeamDriftXNm;      // X선 빔 X축 표류 계측값 [nm]
        public readonly double BeamDriftYNm;      // X선 빔 Y축 표류 계측값 [nm]

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public BraggPeakTelemetryState(double u, double v, double dx, double dy)
        {
            PeakPixelU = u;
            PeakPixelV = v;
            BeamDriftXNm = dx;
            BeamDriftYNm = dy;
        }
    }

    /// <summary>
    /// 국소 변형률 및 피에조 보정 출력
    /// </summary>
    public readonly ref struct NanoXrdAnalysisOutput
    {
        public readonly double LatticeStrainPpm;      // 격자 변형률 [ppm, 10^-6]
        public readonly double StressMegapascals;     // 유효 응력 [MPa]
        public readonly double PiezoCommandXVolt;     // FZP X축 피에조 전압 [V]
        public readonly double PiezoCommandYVolt;     // FZP Y축 피에조 전압 [V]
        public readonly bool IsBeamPositionLocked;    // 빔 표류 < 2nm 안정화 여부

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public NanoXrdAnalysisOutput(double strain, double stress, double vx, double vy, bool locked)
        {
            LatticeStrainPpm = strain;
            StressMegapascals = stress;
            PiezoCommandXVolt = vx;
            PiezoCommandYVolt = vy;
            IsBeamPositionLocked = locked;
        }
    }

    /// <summary>
    /// 10,000Hz 방사광 주사 나노회절 변형률 매핑 및 FZP 피에조 서보 엔진
    /// </summary>
    public ref struct NanoXrdStrainServoEngine
    {
        private readonly double _refPixelU;
        private readonly double _refPixelV;
        private readonly double _detectorDistanceMm;
        private readonly double _pixelPitchUm;
        private readonly double _braggAngleRad;
        private readonly double _youngsModulusGpa;
        private readonly double _poissonRatio;

        private readonly double _kp;
        private readonly double _ki;
        private readonly double _kd;
        private readonly double _piezoGainVoltPerNm;
        private readonly double _maxVoltLimit;

        private double _intErrX;
        private double _intErrY;
        private double _prevErrX;
        private double _prevErrY;

        public NanoXrdStrainServoEngine(
            double refPixelU,
            double refPixelV,
            double detDistMm,
            double pixelPitchUm,
            double braggAngleRad,
            double youngsModulusGpa,
            double poissonRatio,
            double kp,
            double ki,
            double kd,
            double piezoGain,
            double maxVolt)
        {
            _refPixelU = refPixelU;
            _refPixelV = refPixelV;
            _detectorDistanceMm = detDistMm;
            _pixelPitchUm = pixelPitchUm;
            _braggAngleRad = braggAngleRad;
            _youngsModulusGpa = youngsModulusGpa;
            _poissonRatio = poissonRatio;
            _kp = kp;
            _ki = ki;
            _kd = kd;
            _piezoGainVoltPerNm = piezoGain;
            _maxVoltLimit = maxVolt;
            _intErrX = 0.0;
            _intErrY = 0.0;
            _prevErrX = 0.0;
            _prevErrY = 0.0;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public NanoXrdAnalysisOutput ProcessCycle(
            in BraggPeakTelemetryState state,
            double dtSeconds)
        {
            // 1. 브래그 피크 위치 편위 계산
            double du = state.PeakPixelU - _refPixelU;
            double dv = state.PeakPixelV - _refPixelV;
            double radialPixelDist = Math.Sqrt(du * du + dv * dv);

            // 2. 각도 편위 Delta theta_B 계산
            double deltaDistMm = (radialPixelDist * _pixelPitchUm) / 1000.0;
            double deltaThetaRad = deltaDistMm / (2.0 * _detectorDistanceMm * Math.Cos(_braggAngleRad));

            // 3. 변형률 epsilon 및 응력 sigma 산출 (ppm 단위)
            double cotBragg = 1.0 / Math.Tan(_braggAngleRad);
            double strain = -cotBragg * deltaThetaRad; // 단위 없는 비
            double strainPpm = strain * 1e6;

            // 1축 변형률 기준 유효 응력 (MPa = GPa * 1000 * strain)
            double stressMpa = (_youngsModulusGpa * 1000.0) * strain / (1.0 - _poissonRatio);

            // 4. FZP 집속 빔 드리프트 오차 폐루프 보정 (PID)
            double errX = -state.BeamDriftXNm;
            double errY = -state.BeamDriftYNm;

            _intErrX += errX * dtSeconds;
            _intErrY += errY * dtSeconds;
            double derX = (errX - _prevErrX) / dtSeconds;
            double derY = (errY - _prevErrY) / dtSeconds;
            _prevErrX = errX;
            _prevErrY = errY;

            double compX = _kp * errX + _ki * _intErrX + _kd * derX;
            double compY = _kp * errY + _ki * _intErrY + _kd * derY;

            double voltX = Math.Clamp(compX * _piezoGainVoltPerNm, -_maxVoltLimit, _maxVoltLimit);
            double voltY = Math.Clamp(compY * _piezoGainVoltPerNm, -_maxVoltLimit, _maxVoltLimit);

            double residualDriftDist = Math.Sqrt(state.BeamDriftXNm * state.BeamDriftXNm + state.BeamDriftYNm * state.BeamDriftYNm);
            bool isLocked = residualDriftDist <= 2.0; // 2nm 이내 안정화

            return new NanoXrdAnalysisOutput(
                strainPpm,
                stressMpa,
                voltX,
                voltY,
                isLocked);
        }
    }
}