ahrs_int_cmpl_euler.c

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/*
 * Copyright (C) 2008-2010 The Paparazzi Team
 *
 * 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 "ahrs_int_cmpl_euler.h"
 
#include "math/pprz_trig_int.h"
#include "math/pprz_algebra_int.h"
 
#include "generated/airframe.h"
 
#ifndef FACE_REINJ_1
#define FACE_REINJ_1 1024
#endif
 
#ifndef AHRS_MAG_OFFSET
#define AHRS_MAG_OFFSET 0.
#endif
 
struct AhrsIntCmplEuler ahrs_ice;
 
static inline void get_phi_theta_measurement_fom_accel(int32_t *phi_meas, int32_t *theta_meas,
    struct Int32Vect3 *accel);
static inline void get_psi_measurement_from_mag(int32_t *psi_meas, int32_t phi_est, int32_t theta_est,
    struct Int32Vect3 *mag);
 
#define F_UPDATE 512
 
#define PI_INTEG_EULER     (INT32_ANGLE_PI * F_UPDATE)
#define TWO_PI_INTEG_EULER (INT32_ANGLE_2_PI * F_UPDATE)
#define INTEG_EULER_NORMALIZE(_a) {                         \
    while (_a >  PI_INTEG_EULER)  _a -= TWO_PI_INTEG_EULER; \
    while (_a < -PI_INTEG_EULER)  _a += TWO_PI_INTEG_EULER; \
  }
 
 
void ahrs_ice_init(void)
{
  ahrs_ice.status = AHRS_ICE_UNINIT;
  ahrs_ice.is_aligned = false;
 
  /* init ltp_to_imu to zero */
  INT_EULERS_ZERO(ahrs_ice.ltp_to_imu_euler)
  INT_RATES_ZERO(ahrs_ice.imu_rate);
 
  INT_RATES_ZERO(ahrs_ice.gyro_bias);
  ahrs_ice.reinj_1 = FACE_REINJ_1;
 
  ahrs_ice.mag_offset = AHRS_MAG_OFFSET;
}
 
bool ahrs_ice_align(struct Int32Rates *lp_gyro, struct Int32Vect3 *lp_accel,
                      struct Int32Vect3 *lp_mag)
{
 
  get_phi_theta_measurement_fom_accel(&ahrs_ice.hi_res_euler.phi,
                                      &ahrs_ice.hi_res_euler.theta, lp_accel);
  get_psi_measurement_from_mag(&ahrs_ice.hi_res_euler.psi,
                               ahrs_ice.hi_res_euler.phi / F_UPDATE,
                               ahrs_ice.hi_res_euler.theta / F_UPDATE, lp_mag);
 
  EULERS_COPY(ahrs_ice.measure, ahrs_ice.hi_res_euler);
  EULERS_COPY(ahrs_ice.measurement, ahrs_ice.hi_res_euler);
 
  /* Compute LTP to IMU eulers      */
  EULERS_SDIV(ahrs_ice.ltp_to_imu_euler, ahrs_ice.hi_res_euler, F_UPDATE);
 
  RATES_COPY(ahrs_ice.gyro_bias, *lp_gyro);
 
  ahrs_ice.status = AHRS_ICE_RUNNING;
  ahrs_ice.is_aligned = true;
 
  return true;
}
 
//#define USE_NOISE_CUT 1
//#define USE_NOISE_FILTER 1
#define NOISE_FILTER_GAIN 50
 
#if USE_NOISE_CUT
#include "led.h"
static inline bool cut_rates(struct Int32Rates i1, struct Int32Rates i2, int32_t threshold)
{
  struct Int32Rates diff;
  RATES_DIFF(diff, i1, i2);
  if (diff.p < -threshold || diff.p > threshold ||
      diff.q < -threshold || diff.q > threshold ||
      diff.r < -threshold || diff.r > threshold) {
    return true;
  } else {
    return false;
  }
}
#define RATE_CUT_THRESHOLD RATE_BFP_OF_REAL(1)
 
static inline bool cut_accel(struct Int32Vect3 i1, struct Int32Vect3 i2, int32_t threshold)
{
  struct Int32Vect3 diff;
  VECT3_DIFF(diff, i1, i2);
  if (diff.x < -threshold || diff.x > threshold ||
      diff.y < -threshold || diff.y > threshold ||
      diff.z < -threshold || diff.z > threshold) {
    LED_ON(4);
    return true;
  } else {
    LED_OFF(4);
    return false;
  }
}
#define ACCEL_CUT_THRESHOLD ACCEL_BFP_OF_REAL(20)
 
#endif
 
/*
 *
 * fc = 1/(2*pi*tau)
 *
 * alpha = dt / ( tau + dt )
 *
 *
 *  y(i) = alpha x(i) + (1-alpha) y(i-1)
 *  or
 *  y(i) = y(i-1) + alpha * (x(i) - y(i-1))
 *
 *
 */
 
void ahrs_ice_propagate(struct Int32Rates *gyro)
{
 
  /* unbias gyro             */
  struct Int32Rates uf_rate;
  RATES_DIFF(uf_rate, *gyro, ahrs_ice.gyro_bias);
#if USE_NOISE_CUT
  static struct Int32Rates last_uf_rate = { 0, 0, 0 };
  if (!cut_rates(uf_rate, last_uf_rate, RATE_CUT_THRESHOLD)) {
#endif
    /* low pass rate */
#if USE_NOISE_FILTER
    RATES_SUM_SCALED(ahrs_ice.imu_rate, ahrs_ice.imu_rate, uf_rate, NOISE_FILTER_GAIN);
    RATES_SDIV(ahrs_ice.imu_rate, ahrs_ice.imu_rate, NOISE_FILTER_GAIN + 1);
#else
    RATES_ADD(ahrs_ice.imu_rate, uf_rate);
    RATES_SDIV(ahrs_ice.imu_rate, ahrs_ice.imu_rate, 2);
#endif
#if USE_NOISE_CUT
  }
  RATES_COPY(last_uf_rate, uf_rate);
#endif
 
  /* integrate eulers */
  struct Int32Eulers euler_dot;
  int32_eulers_dot_of_rates(&euler_dot, &ahrs_ice.ltp_to_imu_euler, &ahrs_ice.imu_rate);
  EULERS_ADD(ahrs_ice.hi_res_euler, euler_dot);
 
  /* low pass measurement */
  EULERS_ADD(ahrs_ice.measure, ahrs_ice.measurement);
  EULERS_SDIV(ahrs_ice.measure, ahrs_ice.measure, 2);
 
  /* compute residual */
  EULERS_DIFF(ahrs_ice.residual, ahrs_ice.measure, ahrs_ice.hi_res_euler);
  INTEG_EULER_NORMALIZE(ahrs_ice.residual.psi);
 
  struct Int32Eulers correction;
  /* compute a correction */
  EULERS_SDIV(correction, ahrs_ice.residual, ahrs_ice.reinj_1);
  /* correct estimation */
  EULERS_ADD(ahrs_ice.hi_res_euler, correction);
  INTEG_EULER_NORMALIZE(ahrs_ice.hi_res_euler.psi);
 
 
  /* Compute LTP to IMU eulers      */
  EULERS_SDIV(ahrs_ice.ltp_to_imu_euler, ahrs_ice.hi_res_euler, F_UPDATE);
}
 
void ahrs_ice_update_accel(struct Int32Vect3 *accel)
{
 
#if USE_NOISE_CUT || USE_NOISE_FILTER
  static struct Int32Vect3 last_accel = { 0, 0, 0 };
#endif
#if USE_NOISE_CUT
  if (!cut_accel(*accel, last_accel, ACCEL_CUT_THRESHOLD)) {
#endif
#if USE_NOISE_FILTER
    VECT3_SUM_SCALED(*accel, *accel, last_accel, NOISE_FILTER_GAIN);
    VECT3_SDIV(*accel, *accel, NOISE_FILTER_GAIN + 1);
#endif
    get_phi_theta_measurement_fom_accel(&ahrs_ice.measurement.phi, &ahrs_ice.measurement.theta, accel);
#if USE_NOISE_CUT
  }
  VECT3_COPY(last_accel, *accel);
#endif
 
}
 
 
void ahrs_ice_update_mag(struct Int32Vect3 *mag)
{
 
  get_psi_measurement_from_mag(&ahrs_ice.measurement.psi, ahrs_ice.ltp_to_imu_euler.phi, ahrs_ice.ltp_to_imu_euler.theta,
                               mag);
 
}
 
/* measures phi and theta assuming no dynamic acceleration ?!! */
__attribute__((always_inline)) static inline void get_phi_theta_measurement_fom_accel(int32_t *phi_meas,
    int32_t *theta_meas, struct Int32Vect3 *accel)
{
 
  *phi_meas = int32_atan2(-accel->y, -accel->z);
  int32_t cphi;
  PPRZ_ITRIG_COS(cphi, *phi_meas);
  int32_t cphi_ax = -INT_MULT_RSHIFT(cphi, accel->x, INT32_TRIG_FRAC);
  *theta_meas = int32_atan2(-cphi_ax, -accel->z);
  *phi_meas   *= F_UPDATE;
  *theta_meas *= F_UPDATE;
 
}
 
/* measure psi by projecting magnetic vector in local tangeant plan */
__attribute__((always_inline)) static inline void get_psi_measurement_from_mag(int32_t *psi_meas, int32_t phi_est,
    int32_t theta_est, struct Int32Vect3 *mag)
{
 
  int32_t sphi;
  PPRZ_ITRIG_SIN(sphi, phi_est);
  int32_t cphi;
  PPRZ_ITRIG_COS(cphi, phi_est);
  int32_t stheta;
  PPRZ_ITRIG_SIN(stheta, theta_est);
  int32_t ctheta;
  PPRZ_ITRIG_COS(ctheta, theta_est);
 
  int32_t sphi_stheta = (sphi * stheta) >> INT32_TRIG_FRAC;
  int32_t cphi_stheta = (cphi * stheta) >> INT32_TRIG_FRAC;
  //int32_t sphi_ctheta = (sphi*ctheta)>>INT32_TRIG_FRAC;
  //int32_t cphi_ctheta = (cphi*ctheta)>>INT32_TRIG_FRAC;
 
  const int32_t mn = ctheta * mag->x + sphi_stheta * mag->y + cphi_stheta * mag->z;
  const int32_t me = 0      * mag->x + cphi        * mag->y - sphi        * mag->z;
  //const int32_t md =
  //  -stheta     * mag->x +
  //  sphi_ctheta * mag->y +
  //  cphi_ctheta * mag->z;
  float m_psi = -atan2(me, mn);
  *psi_meas = ((m_psi - ahrs_ice.mag_offset) * (float)(1 << (INT32_ANGLE_FRAC)) * F_UPDATE);
 
}
 
void ahrs_ice_set_body_to_imu(struct OrientationReps *body_to_imu)
{
  ahrs_ice_set_body_to_imu_quat(orientationGetQuat_f(body_to_imu));
}
 
void ahrs_ice_set_body_to_imu_quat(struct FloatQuat *q_b2i)
{
  orientationSetQuat_f(&ahrs_ice.body_to_imu, q_b2i);
 
  if (!ahrs_ice.is_aligned) {
    /* Set ltp_to_imu so that body is zero */
    ahrs_ice.ltp_to_imu_euler = *orientationGetEulers_i(&ahrs_ice.body_to_imu);
  }
}