항공기 복합재 날개 압전(PZT) 패치 능동 진동 제어 & 1,000Hz 0-Alloc C# 플러터(Flutter) 공력탄성 억제 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.Aerospace.Aeroelasticity
{
    /// 

    /// 복합재 주익 PZT 압전 패치 플러터 능동 진동 억제 구조체 (0-Alloc C#)
    /// 
    public ref struct PztFlutterSuppressionEngine
    {
        private readonly double _modalMassPlunge;      // kg (~15.0)
        private readonly double _modalInertiaPitch;    // kg*m^2 (~1.2)
        private readonly double _pztMomentGain;        // Nm/V (~0.12)
        private readonly double _kpPlunge;
        private readonly double _kdPlunge;
        private readonly double _kdPitch;
        private readonly double _dt;

        private double _commandedPztVoltageV;          // 출력 전압 (-200V ~ +200V)
        private double _vibrationEnergyJ;
        private bool _isFlutterOnsetDetected;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public PztFlutterSuppressionEngine(
            double pztMomentGain = 0.12,
            double kdPlunge = 80.0,
            double kdPitch = 15.0,
            double dt = 0.001)
        {
            _modalMassPlunge = 15.0;
            _modalInertiaPitch = 1.2;
            _pztMomentGain = pztMomentGain;
            _kdPlunge = kdPlunge;
            _kdPitch = kdPitch;
            _kpPlunge = 25.0;
            _dt = dt;
            _commandedPztVoltageV = 0.0;
            _vibrationEnergyJ = 0.0;
            _isFlutterOnsetDetected = false;
        }

        /// 

        /// 날개 뿌리 스트레인 및 익단 가속도계로부터 플러터 발산을 감지하고 PZT 고전압을 인가 (1,000Hz)
        /// 
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void UpdateAeroelasticStep(
            double tipPlungeDisplacementM,
            double tipPlungeVelocityMps,
            double tipPitchRateRadS,
            double flightDynamicPressureKPa,
            out double commandedVolts,
            out double dampingPowerWatts,
            out bool isFlutterActive)
        {
            // 총 모드 진동 에너지: E = 0.5 * (m*vh^2 + I*valpha^2)
            _vibrationEnergyJ = (0.5 * _modalMassPlunge * tipPlungeVelocityMps * tipPlungeVelocityMps) +
                                (0.5 * _modalInertiaPitch * tipPitchRateRadS * tipPitchRateRadS);

            // 플러터 징후 검출 (진동 에너지 급증 및 동압 한계 초과)
            _isFlutterOnsetDetected = (_vibrationEnergyJ > 2.5) && (flightDynamicPressureKPa > 15.0);

            // 역위상 능동 댐핑 전압: V = -Kd_h * v_h - Kd_alpha * omega_alpha
            double controlVolts = -(_kdPlunge * tipPlungeVelocityMps) - (_kdPitch * tipPitchRateRadS) - (_kpPlunge * tipPlungeDisplacementM);

            // PZT 고전압 드라이버 증폭기 포화 구속 (-200V ~ +200V)
            if (controlVolts > 200.0) controlVolts = 200.0;
            else if (controlVolts < -200.0) controlVolts = -200.0;
            _commandedPztVoltageV = controlVolts;

            // 능동 억제 일률: P = M_pzt * omega_alpha
            double appliedMoment = _pztMomentGain * _commandedPztVoltageV;
            dampingPowerWatts = Math.Abs(appliedMoment * tipPitchRateRadS);

            commandedVolts = _commandedPztVoltageV;
            isFlutterActive = _isFlutterOnsetDetected;
        }

        public double CommandedPztVoltageV => _commandedPztVoltageV;
        public double VibrationEnergyJ => _vibrationEnergyJ;
    }
}