메타물질 음굴절률(Negative Index) & 1,000Hz 0-Alloc C# 스플릿링 공진기(SRR) 광자 스핀 홀 효과 서보 제어기

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

namespace ZeliDesk.Stem.MetaOptics
{
    /// 

    /// 사분면 광검출기(QPD) 4개 채널 전압 입력 프레임
    /// 
    [StructLayout(LayoutKind.Sequential)]
    public readonly struct QpdVoltageFrame
    {
        public readonly uint TickUs;
        public readonly float ChannelA; // Top-Left
        public readonly float ChannelB; // Top-Right
        public readonly float ChannelC; // Bottom-Left
        public readonly float ChannelD; // Bottom-Right

        public QpdVoltageFrame(uint us, float a, float b, float c, float d)
        {
            TickUs = us;
            ChannelA = a;
            ChannelB = b;
            ChannelC = c;
            ChannelD = d;
        }
    }

    /// 

    /// 1,000Hz 0-Alloc 메타물질 광자 스핀 홀 효과 나노 피에조 서보 엔진
    /// 
    public ref struct MetamaterialSpinHallServo
    {
        private const float QpdSensitivityNmPerV = 450.0f; // 450 nm/V 변환비
        private const float TargetTransverseShiftNm = 85.0f; // 목표 스핀 분리 횡변위

        private float _lastShiftError;
        private float _integralError;
        private float _piezoVoltageOut;

        public MetamaterialSpinHallServo(bool initialize = true)
        {
            _lastShiftError = 0.0f;
            _integralError = 0.0f;
            _piezoVoltageOut = 0.0f;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool UpdateTick(in QpdVoltageFrame frame, out float shiftNm, out float piezoControlVolts)
        {
            // 1. QPD 차동 신호로부터 횡방향(Y축) 빔 위치 도출 (0-Alloc)
            float sum = frame.ChannelA + frame.ChannelB + frame.ChannelC + frame.ChannelD;
            if (sum < 1e-4f)
            {
                shiftNm = 0.0f;
                piezoControlVolts = _piezoVoltageOut;
                return false;
            }

            // Y축 편위 = ((A + B) - (C + D)) / Sum
            float diffY = ((frame.ChannelA + frame.ChannelB) - (frame.ChannelC + frame.ChannelD)) / sum;
            shiftNm = diffY * QpdSensitivityNmPerV;

            // 2. 스핀 횡변위 제어 오차 및 PID 항 산출
            float error = TargetTransverseShiftNm - shiftNm;
            _integralError = Math.Clamp(_integralError + (error * 0.001f), -10.0f, 10.0f);
            float deriv = (error - _lastShiftError) / 0.001f;
            _lastShiftError = error;

            // 3. 피에조 액추에이터 전압 출력 합성 (0 ~ 100V)
            float output = (0.25f * error) + (0.05f * _integralError) + (0.002f * deriv);
            _piezoVoltageOut = Math.Clamp(_piezoVoltageOut + output, 0.0f, 100.0f);
            piezoControlVolts = _piezoVoltageOut;

            return MathF.Abs(error) < 5.0f; // 잔여 오차 5nm 이내 수렴
        }
    }
}