Embedded_codes/libraries/RTIMULib/RTFusionKalman4.cpp

////////////////////////////////////////////////////////////////////////////
//
//  This file is part of RTIMULib-Teensy
//
//  Copyright (c) 2014-2015, richards-tech
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//
//  The above copyright notice and this permission notice shall be included in all
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//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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#include "RTFusionKalman4.h"
#include "RTIMUSettings.h"

//  The QVALUE affects the gyro response.

#define KALMAN_QVALUE	0.001f

//  The RVALUE controls the influence of the accels and compass.
//  The bigger the value, the more sluggish the response.

#define KALMAN_RVALUE	0.0005f

#define KALMAN_QUATERNION_LENGTH	4

#define	KALMAN_STATE_LENGTH	4								// just the quaternion for the moment


RTFusionKalman4::RTFusionKalman4()
{
    reset();
}

RTFusionKalman4::~RTFusionKalman4()
{
}

void RTFusionKalman4::reset()
{
    m_firstTime = true;
    m_fusionPose = RTVector3();
    m_fusionQPose.fromEuler(m_fusionPose);
    m_gyro = RTVector3();
    m_accel = RTVector3();
    m_compass = RTVector3();
    m_measuredPose = RTVector3();
    m_measuredQPose.fromEuler(m_measuredPose);
    m_Rk.fill(0);
    m_Q.fill(0);

    // initialize process noise covariance matrix

    for (int i = 0; i < KALMAN_STATE_LENGTH; i++)
        for (int j = 0; j < KALMAN_STATE_LENGTH; j++)
            m_Q.setVal(i, i, KALMAN_QVALUE);

    // initialize observation noise covariance matrix


    for (int i = 0; i < KALMAN_STATE_LENGTH; i++)
        for (int j = 0; j < KALMAN_STATE_LENGTH; j++)
            m_Rk.setVal(i, i, KALMAN_RVALUE);
 }

void RTFusionKalman4::predict()
{
    RTMatrix4x4 mat;
    RTQuaternion tQuat;
    RTFLOAT x2, y2, z2;

    //  compute the state transition matrix

    x2 = m_gyro.x() / (RTFLOAT)2.0;
    y2 = m_gyro.y() / (RTFLOAT)2.0;
    z2 = m_gyro.z() / (RTFLOAT)2.0;

    m_Fk.setVal(0, 1, -x2);
    m_Fk.setVal(0, 2, -y2);
    m_Fk.setVal(0, 3, -z2);

    m_Fk.setVal(1, 0, x2);
    m_Fk.setVal(1, 2, z2);
    m_Fk.setVal(1, 3, -y2);

    m_Fk.setVal(2, 0, y2);
    m_Fk.setVal(2, 1, -z2);
    m_Fk.setVal(2, 3, x2);

    m_Fk.setVal(3, 0, z2);
    m_Fk.setVal(3, 1, y2);
    m_Fk.setVal(3, 2, -x2);

    m_FkTranspose = m_Fk.transposed();

    // Predict new state estimate Xkk_1 = Fk * Xk_1k_1

    tQuat = m_Fk * m_stateQ;
    tQuat *= m_timeDelta;
    m_stateQ += tQuat;

//    m_stateQ.normalize();

    // Compute PDot = Fk * Pk_1k_1 + Pk_1k_1 * FkTranspose (note Pkk == Pk_1k_1 at this stage)

    m_PDot = m_Fk * m_Pkk;
    mat = m_Pkk * m_FkTranspose;
    m_PDot += mat;

    // add in Q to get the new prediction

    m_Pkk_1 = m_PDot + m_Q;

    //  multiply by deltaTime (variable name is now misleading though)

    m_Pkk_1 *= m_timeDelta;
}


void RTFusionKalman4::update()
{
    RTQuaternion delta;
    RTMatrix4x4 Sk, SkInverse;

    if (m_enableCompass || m_enableAccel) {
        m_stateQError = m_measuredQPose - m_stateQ;
    } else {
        m_stateQError = RTQuaternion();
    }

    //	Compute residual covariance Sk = Hk * Pkk_1 * HkTranspose + Rk
    //  Note: since Hk is the identity matrix, this has been simplified

    Sk = m_Pkk_1 + m_Rk;

    //	Compute Kalman gain Kk = Pkk_1 * HkTranspose * SkInverse
    //  Note: again, the HkTranspose part is omitted

    SkInverse = Sk.inverted();

    m_Kk = m_Pkk_1 * SkInverse;

    if (m_debug)
        HAL_INFO(RTMath::display("Gain", m_Kk));

    // make new state estimate

    delta = m_Kk * m_stateQError;

    m_stateQ += delta;

    m_stateQ.normalize();

    //  produce new estimate covariance Pkk = (I - Kk * Hk) * Pkk_1
    //  Note: since Hk is the identity matrix, it is omitted

    m_Pkk.setToIdentity();
    m_Pkk -= m_Kk;
    m_Pkk = m_Pkk * m_Pkk_1;

    if (m_debug)
        HAL_INFO(RTMath::display("Cov", m_Pkk));
}

void RTFusionKalman4::newIMUData(RTIMU_DATA& data, const RTIMUSettings *settings)
{
    if (m_enableGyro)
        m_gyro = data.gyro;
    else
        m_gyro = RTVector3();
    m_accel = data.accel;
    m_compass = data.compass;
    m_compassValid = data.compassValid;

    if (m_firstTime) {
        m_lastFusionTime = data.timestamp;
        calculatePose(m_accel, m_compass, settings->m_compassAdjDeclination);
        m_Fk.fill(0);

        //  init covariance matrix to something

        m_Pkk.fill(0);
        for (int i = 0; i < 4; i++)
            for (int j = 0; j < 4; j++)
                m_Pkk.setVal(i,j, 0.5);

        // initialize the observation model Hk
        // Note: since the model is the state vector, this is an identity matrix so it won't be used

        //  initialize the poses

        m_stateQ.fromEuler(m_measuredPose);
        m_fusionQPose = m_stateQ;
        m_fusionPose = m_measuredPose;
        m_firstTime = false;
    } else {
        m_timeDelta = (RTFLOAT)(data.timestamp - m_lastFusionTime) / (RTFLOAT)1000000;
        m_lastFusionTime = data.timestamp;
        if (m_timeDelta <= 0)
            return;

        if (m_debug) {
            HAL_INFO("\n------\n");
            HAL_INFO1("IMU update delta time: %f\n", m_timeDelta);
        }

        calculatePose(data.accel, data.compass, settings->m_compassAdjDeclination);

        predict();
        update();
        m_stateQ.toEuler(m_fusionPose);
        m_fusionQPose = m_stateQ;

        if (m_debug) {
            HAL_INFO(RTMath::displayRadians("Measured pose", m_measuredPose));
            HAL_INFO(RTMath::displayRadians("Kalman pose", m_fusionPose));
            HAL_INFO(RTMath::displayRadians("Measured quat", m_measuredPose));
            HAL_INFO(RTMath::display("Kalman quat", m_stateQ));
            HAL_INFO(RTMath::display("Error quat", m_stateQError));
         }
    }
    data.fusionPoseValid = true;
    data.fusionQPoseValid = true;
    data.fusionPose = m_fusionPose;
    data.fusionQPose = m_fusionQPose;
}