RTFusion.cpp

////////////////////////////////////////////////////////////////////////////
//
//  This file is part of RTIMULib
//
//  Copyright (c) 2014-2015, richards-tech, LLC
//
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//  this software and associated documentation files (the "Software"), to deal in
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//  Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  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 "RTFusion.h"
#include "RTIMUHal.h"

//  The slerp power valule controls the influence of the measured state to correct the predicted state
//  0 = measured state ignored (just gyros), 1 = measured state overrides predicted state.
//  In between 0 and 1 mixes the two conditions

#define RTQF_SLERP_POWER (RTFLOAT)0.02;

const char *RTFusion::m_fusionNameMap[] = {
    "NULL",
    "Kalman STATE4",
    "RTQF"};

RTFusion::RTFusion()
{
    m_debug = false;
    m_firstTime = true;
    m_enableGyro = true;
    m_enableAccel = true;
    m_enableCompass = true;

    m_gravity.setScalar(0);
    m_gravity.setX(0);
    m_gravity.setY(0);
    m_gravity.setZ(1);

    m_slerpPower = RTQF_SLERP_POWER;
}

RTFusion::~RTFusion()
{
}

void RTFusion::calculatePose(const RTVector3& accel, const RTVector3& mag, float magDeclination)
{
    RTQuaternion m;
    RTQuaternion q;

    if (m_enableAccel) {
        accel.accelToEuler(m_measuredPose);
    } else {
        m_measuredPose = m_fusionPose;
        m_measuredPose.setZ(0);
    }

    if (m_enableCompass && m_compassValid) {
        q.fromEuler(m_measuredPose);
        m.setScalar(0);
        m.setX(mag.x());
        m.setY(mag.y());
        m.setZ(mag.z());

        m = q * m * q.conjugate();
        m_measuredPose.setZ(-atan2(m.y(), m.x()) - magDeclination);
    } else {
        m_measuredPose.setZ(m_fusionPose.z());
    }

    m_measuredQPose.fromEuler(m_measuredPose);

    //  check for quaternion aliasing. If the quaternion has the wrong sign
    //  the kalman filter will be very unhappy.

    int maxIndex = -1;
    RTFLOAT maxVal = -1000;

    for (int i = 0; i < 4; i++) {
        if (fabs(m_measuredQPose.data(i)) > maxVal) {
            maxVal = fabs(m_measuredQPose.data(i));
            maxIndex = i;
        }
    }

    //  if the biggest component has a different sign in the measured and kalman poses,
    //  change the sign of the measured pose to match.

    if (((m_measuredQPose.data(maxIndex) < 0) && (m_fusionQPose.data(maxIndex) > 0)) ||
            ((m_measuredQPose.data(maxIndex) > 0) && (m_fusionQPose.data(maxIndex) < 0))) {
        m_measuredQPose.setScalar(-m_measuredQPose.scalar());
        m_measuredQPose.setX(-m_measuredQPose.x());
        m_measuredQPose.setY(-m_measuredQPose.y());
        m_measuredQPose.setZ(-m_measuredQPose.z());
        m_measuredQPose.toEuler(m_measuredPose);
    }
}


RTVector3 RTFusion::getAccelResiduals()
{
    RTQuaternion rotatedGravity;
    RTQuaternion fusedConjugate;
    RTQuaternion qTemp;
    RTVector3 residuals;

    //  do gravity rotation and subtraction

    // create the conjugate of the pose

    fusedConjugate = m_fusionQPose.conjugate();

    // now do the rotation - takes two steps with qTemp as the intermediate variable

    qTemp = m_gravity * m_fusionQPose;
    rotatedGravity = fusedConjugate * qTemp;

    // now adjust the measured accel and change the signs to make sense

    residuals.setX(-(m_accel.x() - rotatedGravity.x()));
    residuals.setY(-(m_accel.y() - rotatedGravity.y()));
    residuals.setZ(-(m_accel.z() - rotatedGravity.z()));
    return residuals;
}