ahrs_float_mlkf.c

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/*
 * Copyright (C) 2011-2012  Antoine Drouin <poinix@gmail.com>
 * Copyright (C) 2013       Felix Ruess <felix.ruess@gmail.com>
 *
 * This file is part of paparazzi.
 *
 * paparazzi is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * paparazzi is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with paparazzi; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include "subsystems/ahrs/ahrs_float_mlkf.h"
#include "subsystems/ahrs/ahrs_float_utils.h"

#include <string.h>  /* for memcpy      */

#include "math/pprz_algebra_float.h"
#include "math/pprz_algebra_int.h"
#include "math/pprz_simple_matrix.h"
#include "generated/airframe.h"

//#include <stdio.h>

#ifndef AHRS_MAG_NOISE_X
#define AHRS_MAG_NOISE_X 0.2
#define AHRS_MAG_NOISE_Y 0.2
#define AHRS_MAG_NOISE_Z 0.2
#endif

static inline void propagate_ref(struct FloatRates *gyro, float dt);
static inline void propagate_state(float dt);
static inline void update_state(const struct FloatVect3 *i_expected,
                                struct FloatVect3 *b_measured,
                                struct FloatVect3 *noise);
static inline void update_state_heading(const struct FloatVect3 *i_expected,
                                        struct FloatVect3 *b_measured,
                                        struct FloatVect3 *noise);
static inline void reset_state(void);

struct AhrsMlkf ahrs_mlkf;


void ahrs_mlkf_init(void)
{

  ahrs_mlkf.is_aligned = false;

  /* init ltp_to_imu quaternion as zero/identity rotation */
  float_quat_identity(&ahrs_mlkf.ltp_to_imu_quat);
  FLOAT_RATES_ZERO(ahrs_mlkf.imu_rate);

  VECT3_ASSIGN(ahrs_mlkf.mag_h, AHRS_H_X, AHRS_H_Y, AHRS_H_Z);

  /*
   * Initialises our state
   */
  FLOAT_RATES_ZERO(ahrs_mlkf.gyro_bias);
  const float P0_a = 1.;
  const float P0_b = 1e-4;
  float P0[6][6] = {{ P0_a, 0.,   0.,   0.,   0.,   0.  },
    { 0.,   P0_a, 0.,   0.,   0.,   0.  },
    { 0.,   0.,   P0_a, 0.,   0.,   0.  },
    { 0.,   0.,   0.,   P0_b, 0.,   0.  },
    { 0.,   0.,   0.,   0.,   P0_b, 0.  },
    { 0.,   0.,   0.,   0.,   0.,   P0_b}
  };
  memcpy(ahrs_mlkf.P, P0, sizeof(P0));

  VECT3_ASSIGN(ahrs_mlkf.mag_noise, AHRS_MAG_NOISE_X, AHRS_MAG_NOISE_Y, AHRS_MAG_NOISE_Z);
}

void ahrs_mlkf_set_body_to_imu(struct OrientationReps *body_to_imu)
{
  ahrs_mlkf_set_body_to_imu_quat(orientationGetQuat_f(body_to_imu));
}

void ahrs_mlkf_set_body_to_imu_quat(struct FloatQuat *q_b2i)
{
  orientationSetQuat_f(&ahrs_mlkf.body_to_imu, q_b2i);

  if (!ahrs_mlkf.is_aligned) {
    /* Set ltp_to_imu so that body is zero */
    ahrs_mlkf.ltp_to_imu_quat = *orientationGetQuat_f(&ahrs_mlkf.body_to_imu);
  }
}


bool ahrs_mlkf_align(struct FloatRates *lp_gyro, struct FloatVect3 *lp_accel,
                       struct FloatVect3 *lp_mag)
{

  /* Compute an initial orientation from accel and mag directly as quaternion */
  ahrs_float_get_quat_from_accel_mag(&ahrs_mlkf.ltp_to_imu_quat, lp_accel, lp_mag);

  /* used averaged gyro as initial value for bias */
  ahrs_mlkf.gyro_bias = *lp_gyro;

  ahrs_mlkf.is_aligned = true;

  return true;
}

void ahrs_mlkf_propagate(struct FloatRates *gyro, float dt)
{
  propagate_ref(gyro, dt);
  propagate_state(dt);
}

void ahrs_mlkf_update_accel(struct FloatVect3 *accel)
{
  struct FloatVect3 imu_g = *accel;
  const float alpha = 0.92;
  ahrs_mlkf.lp_accel = alpha * ahrs_mlkf.lp_accel +
                       (1. - alpha) * (float_vect3_norm(&imu_g) - 9.81);
  const struct FloatVect3 earth_g = {0.,  0., -9.81 };
  const float dn = 250 * fabs(ahrs_mlkf.lp_accel);
  struct FloatVect3 g_noise = {1. + dn, 1. + dn, 1. + dn};
  update_state(&earth_g, &imu_g, &g_noise);
  reset_state();
}

void ahrs_mlkf_update_mag(struct FloatVect3 *mag)
{
#if AHRS_MAG_UPDATE_ALL_AXES
  ahrs_mlkf_update_mag_full(mag);
#else
  ahrs_mlkf_update_mag_2d(mag);
#endif
}

void ahrs_mlkf_update_mag_2d(struct FloatVect3 *mag)
{
  update_state_heading(&ahrs_mlkf.mag_h, mag, &ahrs_mlkf.mag_noise);
  reset_state();
}

void ahrs_mlkf_update_mag_full(struct FloatVect3 *mag)
{
  update_state(&ahrs_mlkf.mag_h, mag, &ahrs_mlkf.mag_noise);
  reset_state();
}


static inline void propagate_ref(struct FloatRates *gyro, float dt)
{
  struct FloatRates rates = *gyro;

  /* unbias measurement */
  RATES_SUB(rates, ahrs_mlkf.gyro_bias);

#ifdef AHRS_PROPAGATE_LOW_PASS_RATES
  /* lowpass angular rates */
  const float alpha = 0.1;
  FLOAT_RATES_LIN_CMB(ahrs_mlkf.imu_rate, ahrs_mlkf.imu_rate,
                      (1. - alpha), rates, alpha);
#else
  RATES_COPY(ahrs_mlkf.imu_rate, rates);
#endif

  /* propagate reference quaternion */
  float_quat_integrate(&ahrs_mlkf.ltp_to_imu_quat, &ahrs_mlkf.imu_rate, dt);

}

static inline void propagate_state(float dt)
{

  /* predict covariance */
  const float dp = ahrs_mlkf.imu_rate.p * dt;
  const float dq = ahrs_mlkf.imu_rate.q * dt;
  const float dr = ahrs_mlkf.imu_rate.r * dt;

  float F[6][6] = {{  1.,   dr,  -dq,  -dt,   0.,   0.  },
    { -dr,   1.,   dp,   0.,  -dt,   0.  },
    {  dq,  -dp,   1.,   0.,   0.,  -dt  },
    {  0.,   0.,   0.,   1.,   0.,   0.  },
    {  0.,   0.,   0.,   0.,   1.,   0.  },
    {  0.,   0.,   0.,   0.,   0.,   1.  }
  };
  // P = FPF' + GQG
  float tmp[6][6];
  MAT_MUL(6, 6, 6, tmp, F, ahrs_mlkf.P);
  MAT_MUL_T(6, 6, 6,  ahrs_mlkf.P, tmp, F);
  const float dt2 = dt * dt;
  const float GQG[6] = {dt2 * 10e-3, dt2 * 10e-3, dt2 * 10e-3, dt2 * 9e-6, dt2 * 9e-6, dt2 * 9e-6 };
  for (int i = 0; i < 6; i++) {
    ahrs_mlkf.P[i][i] += GQG[i];
  }

}


static inline void update_state(const struct FloatVect3 *i_expected, struct FloatVect3 *b_measured,
                                struct FloatVect3 *noise)
{

  /* converted expected measurement from inertial to body frame */
  struct FloatVect3 b_expected;
  float_quat_vmult(&b_expected, &ahrs_mlkf.ltp_to_imu_quat, i_expected);

  // S = HPH' + JRJ
  float H[3][6] = {{           0., -b_expected.z,  b_expected.y, 0., 0., 0.},
                   { b_expected.z,            0., -b_expected.x, 0., 0., 0.},
                   { -b_expected.y, b_expected.x,            0., 0., 0., 0.}
  };
  float tmp[3][6];
  MAT_MUL(3, 6, 6, tmp, H, ahrs_mlkf.P);
  float S[3][3];
  MAT_MUL_T(3, 6, 3, S, tmp, H);

  /* add the measurement noise */
  S[0][0] += noise->x;
  S[1][1] += noise->y;
  S[2][2] += noise->z;

  float invS[3][3];
  MAT_INV33(invS, S);

  // K = PH'invS
  float tmp2[6][3];
  MAT_MUL_T(6, 6, 3, tmp2, ahrs_mlkf.P, H);
  float K[6][3];
  MAT_MUL(6, 3, 3, K, tmp2, invS);

  // P = (I-KH)P
  float tmp3[6][6];
  MAT_MUL(6, 3, 6, tmp3, K, H);
  float I6[6][6] = {{ 1., 0., 0., 0., 0., 0. },
    {  0., 1., 0., 0., 0., 0. },
    {  0., 0., 1., 0., 0., 0. },
    {  0., 0., 0., 1., 0., 0. },
    {  0., 0., 0., 0., 1., 0. },
    {  0., 0., 0., 0., 0., 1. }
  };
  float tmp4[6][6];
  MAT_SUB(6, 6, tmp4, I6, tmp3);
  float tmp5[6][6];
  MAT_MUL(6, 6, 6, tmp5, tmp4, ahrs_mlkf.P);
  memcpy(ahrs_mlkf.P, tmp5, sizeof(ahrs_mlkf.P));

  // X = X + Ke
  struct FloatVect3 e;
  VECT3_DIFF(e, *b_measured, b_expected);
  ahrs_mlkf.gibbs_cor.qx += K[0][0] * e.x + K[0][1] * e.y + K[0][2] * e.z;
  ahrs_mlkf.gibbs_cor.qy += K[1][0] * e.x + K[1][1] * e.y + K[1][2] * e.z;
  ahrs_mlkf.gibbs_cor.qz += K[2][0] * e.x + K[2][1] * e.y + K[2][2] * e.z;
  ahrs_mlkf.gyro_bias.p  += K[3][0] * e.x + K[3][1] * e.y + K[3][2] * e.z;
  ahrs_mlkf.gyro_bias.q  += K[4][0] * e.x + K[4][1] * e.y + K[4][2] * e.z;
  ahrs_mlkf.gyro_bias.r  += K[5][0] * e.x + K[5][1] * e.y + K[5][2] * e.z;

}


static inline void update_state_heading(const struct FloatVect3 *i_expected,
                                        struct FloatVect3 *b_measured,
                                        struct FloatVect3 *noise)
{

  /* converted expected measurement from inertial to body frame */
  struct FloatVect3 b_expected;
  float_quat_vmult(&b_expected, &ahrs_mlkf.ltp_to_imu_quat, i_expected);

  /* set roll/pitch errors to zero to only correct heading */
  struct FloatVect3 i_h_2d = {i_expected->y, -i_expected->x, 0.f};
  struct FloatVect3 b_yaw;
  float_quat_vmult(&b_yaw, &ahrs_mlkf.ltp_to_imu_quat, &i_h_2d);
  // S = HPH' + JRJ
  float H[3][6] = {{ 0., 0., b_yaw.x, 0., 0., 0.},
                   { 0., 0., b_yaw.y, 0., 0., 0.},
                   { 0., 0., b_yaw.z, 0., 0., 0.}
  };
  float tmp[3][6];
  MAT_MUL(3, 6, 6, tmp, H, ahrs_mlkf.P);
  float S[3][3];
  MAT_MUL_T(3, 6, 3, S, tmp, H);

  /* add the measurement noise */
  S[0][0] += noise->x;
  S[1][1] += noise->y;
  S[2][2] += noise->z;

  float invS[3][3];
  MAT_INV33(invS, S);

  // K = PH'invS
  float tmp2[6][3];
  MAT_MUL_T(6, 6, 3, tmp2, ahrs_mlkf.P, H);
  float K[6][3];
  MAT_MUL(6, 3, 3, K, tmp2, invS);

  // P = (I-KH)P
  float tmp3[6][6];
  MAT_MUL(6, 3, 6, tmp3, K, H);
  float I6[6][6] = {{ 1., 0., 0., 0., 0., 0. },
    {  0., 1., 0., 0., 0., 0. },
    {  0., 0., 1., 0., 0., 0. },
    {  0., 0., 0., 1., 0., 0. },
    {  0., 0., 0., 0., 1., 0. },
    {  0., 0., 0., 0., 0., 1. }
  };
  float tmp4[6][6];
  MAT_SUB(6, 6, tmp4, I6, tmp3);
  float tmp5[6][6];
  MAT_MUL(6, 6, 6, tmp5, tmp4, ahrs_mlkf.P);
  memcpy(ahrs_mlkf.P, tmp5, sizeof(ahrs_mlkf.P));

  // X = X + Ke
  struct FloatVect3 e;
  VECT3_DIFF(e, *b_measured, b_expected);
  ahrs_mlkf.gibbs_cor.qx += K[0][0] * e.x + K[0][1] * e.y + K[0][2] * e.z;
  ahrs_mlkf.gibbs_cor.qy += K[1][0] * e.x + K[1][1] * e.y + K[1][2] * e.z;
  ahrs_mlkf.gibbs_cor.qz += K[2][0] * e.x + K[2][1] * e.y + K[2][2] * e.z;
  ahrs_mlkf.gyro_bias.p  += K[3][0] * e.x + K[3][1] * e.y + K[3][2] * e.z;
  ahrs_mlkf.gyro_bias.q  += K[4][0] * e.x + K[4][1] * e.y + K[4][2] * e.z;
  ahrs_mlkf.gyro_bias.r  += K[5][0] * e.x + K[5][1] * e.y + K[5][2] * e.z;

}
static inline void reset_state(void)
{

  ahrs_mlkf.gibbs_cor.qi = 2.;
  struct FloatQuat q_tmp;
  float_quat_comp(&q_tmp, &ahrs_mlkf.ltp_to_imu_quat, &ahrs_mlkf.gibbs_cor);
  float_quat_normalize(&q_tmp);
  ahrs_mlkf.ltp_to_imu_quat = q_tmp;
  float_quat_identity(&ahrs_mlkf.gibbs_cor);

}