홀 추력기(Hall Thruster) 아노드 레이어 전자 수송 & 1,000Hz 0-Alloc C# 호흡 모드(Breathing Mode) 플라즈마 진동 억제 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.Aerospace.HallThruster
{
    /// 

    /// 홀 추력기 호흡 모드 진동 감쇠 및 방전 안정화 서보 엔진 (0-Alloc C#)
    /// 
    public ref struct HallThrusterBreathingEngine
    {
        private const double ElectronCharge = 1.602176634e-19; // C
        private const double XenonMassKg = 2.1801714e-25;       // kg
        
        private readonly double _channelLengthM;     // 채널 길이 (~0.025 m)
        private readonly double _targetVoltageVd;    // 공칭 방전 전압 (300 V)
        private readonly double _kp;
        private readonly double _kd;
        private readonly double _dt;

        private double _commandedVoltageVd;
        private double _neutralDensityNn;            // m^-3
        private double _plasmaDensityNi;             // m^-3
        private double _prevDischargeCurrentA;
        private double _estimatedThrustMilliNewtons;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public HallThrusterBreathingEngine(
            double channelLengthM = 0.025,
            double targetVoltageVd = 300.0,
            double kp = 4.5,
            double kd = 0.35,
            double dt = 0.001)
        {
            _channelLengthM = channelLengthM;
            _targetVoltageVd = targetVoltageVd;
            _kp = kp;
            _kd = kd;
            _dt = dt;
            _commandedVoltageVd = targetVoltageVd;
            _neutralDensityNn = 1.0e19;
            _plasmaDensityNi = 2.0e17;
            _prevDischargeCurrentA = 3.0;
            _estimatedThrustMilliNewtons = 0.0;
        }

        /// 

        /// 계측된 방전 전류(A)와 가스 유량으로부터 호흡 모드 진동을 억제하고 추력을 연산 (1,000Hz)
        /// 
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void UpdateServoStep(
            double measuredCurrentAmperes,
            double massFlowMgPerSec,
            out double commandedVd,
            out double thrustMilliNewtons,
            out bool isBreathingInstability)
        {
            // 방전 전류 섭동율 dI/dt
            double dIdt = (measuredCurrentAmperes - _prevDischargeCurrentA) / _dt;
            _prevDischargeCurrentA = measuredCurrentAmperes;

            // 전류 리플이 기준값(3.0A) 대비 30% 이상 요동 시 불안정 경보
            double currentRipple = Math.Abs(measuredCurrentAmperes - 3.0);
            isBreathingInstability = currentRipple > 0.9;

            // 능동 역위상 보정 전압: Delta V = -Kp * Delta I - Kd * dI/dt
            double voltageCompensation = -(_kp * (measuredCurrentAmperes - 3.0)) - (_kd * dIdt);
            _commandedVoltageVd = _targetVoltageVd + voltageCompensation;

            // PPU 하드웨어 출력 전압 한계 (220V ~ 380V)
            if (_commandedVoltageVd < 220.0) _commandedVoltageVd = 220.0;
            else if (_commandedVoltageVd > 380.0) _commandedVoltageVd = 380.0;

            // 유효 이온 배출 속도: v_i = sqrt(2 * e * Vd / M_xe)
            double vi = Math.Sqrt((2.0 * ElectronCharge * _commandedVoltageVd) / XenonMassKg);
            
            // 추력 F = m_dot * vi * eta (m_dot: kg/s)
            double mDotKgS = massFlowMgPerSec * 1e-6;
            _estimatedThrustMilliNewtons = (mDotKgS * vi * 0.85) * 1000.0; // mN

            commandedVd = _commandedVoltageVd;
            thrustMilliNewtons = _estimatedThrustMilliNewtons;
        }

        public double CommandedVoltageVd => _commandedVoltageVd;
        public double EstimatedThrustMilliNewtons => _estimatedThrustMilliNewtons;
    }
}