guidance_hybrid.c

Go to the documentation of this file.

/*
 * Copyright (C) 2014 Ewoud Smeur <e.j.j.smeur@tudelft.nl>
 * This is code for guidance of hybrid UAVs. It needs a simple velocity
 * model to control the ground velocity of the UAV while estimating the
 * wind velocity.
 *
 * 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 "firmwares/rotorcraft/guidance/guidance_hybrid.h"
#include "firmwares/rotorcraft/guidance/guidance_h.h"
#include "modules/radio_control/radio_control.h"
#include "firmwares/rotorcraft/stabilization/stabilization_attitude.h"
 
/* for guidance_v.thrust_coeff */
#include "firmwares/rotorcraft/guidance/guidance_v.h"
 
#include "firmwares/rotorcraft/guidance/guidance_pid.h" // FIXME is it really what we want ?
 
// max airspeed for quadshot guidance
#ifndef MAX_AIRSPEED
#define MAX_AIRSPEED 15
#endif
 
// high res frac for integration of angles
#define INT32_ANGLE_HIGH_RES_FRAC 18
 
// Variables used for settings
int32_t guidance_hybrid_norm_ref_airspeed;
float guidance_hybrid_norm_ref_airspeed_f;
int32_t max_airspeed = MAX_AIRSPEED;
int32_t wind_gain;
int32_t horizontal_speed_gain;
float max_turn_bank;
float turn_bank_gain;
 
#define AIRSPEED_HOVER          4
#define AIRSPEED_FORWARD        12
#define CRUISE_THROTTLE         4000
#define FWD_SPEED_P_GAIN        30
#define FWD_ALT_THRUST_GAIN     0.35
#define FWD_PID_DIV             2
#define FWD_NOMINAL_PITCH       78.0
#define FWD_PITCH_GAIN          2.1
#define HOVER_P_GAIN            12
 
int32_t cruise_throttle = CRUISE_THROTTLE;
int32_t fwd_speed_p_gain = FWD_SPEED_P_GAIN;
float fwd_alt_thrust_gain = FWD_ALT_THRUST_GAIN;
float fwd_pid_div = FWD_PID_DIV;
float fwd_nominal_pitch = FWD_NOMINAL_PITCH;
float fwd_pitch_gain = FWD_PITCH_GAIN;
int32_t hover_p_gain = HOVER_P_GAIN;
 
// Private variables
static struct Int32Vect2 guidance_hybrid_groundspeed_sp;
static struct Int32Eulers guidance_hybrid_ypr_sp;
static struct Int32Vect2 guidance_hybrid_airspeed_sp;
static struct Int32Vect2 guidance_h_pos_err;
static struct Int32Vect2 guidance_hybrid_airspeed_ref;
static struct Int32Vect2 wind_estimate;
static struct Int32Vect2 wind_estimate_high_res;
static struct Int32Vect2 guidance_hybrid_ref_airspeed;
 
static int32_t norm_sp_airspeed_disp;
static int32_t heading_diff_disp;
static int32_t omega_disp;
static int32_t high_res_psi;
static int32_t airspeed_sp_heading_disp;
static bool guidance_hovering;
bool force_forward_flight;
static int32_t v_control_pitch;
 
#if PERIODIC_TELEMETRY
#include "modules/datalink/telemetry.h"
 
static void send_hybrid_guidance(struct transport_tx *trans, struct link_device *dev)
{
  struct NedCoor_i *pos = stateGetPositionNed_i();
  struct NedCoor_i *speed = stateGetSpeedNed_i();
  pprz_msg_send_HYBRID_GUIDANCE(trans, dev, AC_ID,
                                &(pos->x), &(pos->y),
                                &(speed->x), &(speed->y),
                                &wind_estimate.x, &wind_estimate.y,
                                &guidance_h_pos_err.x,
                                &guidance_h_pos_err.y,
                                &guidance_hybrid_airspeed_sp.x,
                                &guidance_hybrid_airspeed_sp.y,
                                &guidance_hybrid_norm_ref_airspeed,
                                &heading_diff_disp,
                                &guidance_hybrid_ypr_sp.phi,
                                &guidance_hybrid_ypr_sp.theta,
                                &guidance_hybrid_ypr_sp.psi);
}
 
#endif
 
void guidance_hybrid_init(void)
{
 
  INT_EULERS_ZERO(guidance_hybrid_ypr_sp);
  INT_VECT2_ZERO(guidance_hybrid_airspeed_sp);
  INT_VECT2_ZERO(guidance_hybrid_airspeed_ref);
  INT_VECT2_ZERO(guidance_hybrid_groundspeed_sp);
 
  high_res_psi = 0;
  guidance_hovering = true;
  horizontal_speed_gain = 6;
  guidance_hybrid_norm_ref_airspeed = 0;
  guidance_hybrid_norm_ref_airspeed_f = 0;
  max_turn_bank = 23.0;
  turn_bank_gain = 0.5;
  wind_gain = 35;
  force_forward_flight = 0;
  INT_VECT2_ZERO(wind_estimate);
  INT_VECT2_ZERO(guidance_hybrid_ref_airspeed);
  INT_VECT2_ZERO(wind_estimate_high_res);
 
#if PERIODIC_TELEMETRY
  register_periodic_telemetry(DefaultPeriodic, PPRZ_MSG_ID_HYBRID_GUIDANCE, send_hybrid_guidance);
#endif
 
}
 
#define INT32_ANGLE_HIGH_RES_NORMALIZE(_a) {             \
    while ((_a) > (INT32_ANGLE_PI << (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC)))  (_a) -= (INT32_ANGLE_2_PI << (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC));    \
    while ((_a) < -(INT32_ANGLE_PI << (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC))) (_a) += (INT32_ANGLE_2_PI << (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC));    \
  }
 
struct StabilizationSetpoint guidance_hybrid_run(void)
{
  guidance_hybrid_determine_wind_estimate();
  guidance_hybrid_groundspeed_to_airspeed();
  guidance_hybrid_airspeed_to_attitude(&guidance_hybrid_ypr_sp);
  return guidance_hybrid_set_cmd_i(&guidance_hybrid_ypr_sp);
}
 
struct StabilizationSetpoint guidance_hybrid_h_run_pos(bool in_flight UNUSED, struct HorizontalGuidance *gh)
{
  // compute position error
  VECT2_DIFF(guidance_h_pos_err, gh->sp.pos, *stateGetPositionNed_i());
  // Compute ground speed setpoint
  VECT2_SDIV(guidance_hybrid_groundspeed_sp, guidance_h_pos_err, horizontal_speed_gain);
  return guidance_hybrid_run();
}
 
struct StabilizationSetpoint guidance_hybrid_h_run_speed(bool in_flight UNUSED, struct HorizontalGuidance *gh)
{
  // directly set ground speed setpoint
  VECT2_COPY(guidance_hybrid_groundspeed_sp, gh->sp.speed);
  return guidance_hybrid_run();
}
 
struct StabilizationSetpoint guidance_hybrid_h_run_accel(bool in_flight UNUSED, struct HorizontalGuidance *gh UNUSED)
{
  struct StabilizationSetpoint sp = { 0 };
  // TODO
  return sp;
}
 
struct ThrustSetpoint guidance_hybrid_v_run_pos(bool in_flight, struct VerticalGuidance *gv)
{
  struct ThrustSetpoint th = guidance_pid_v_run_pos(in_flight, gv);
  return guidance_hybrid_vertical(&th);
}
 
struct ThrustSetpoint guidance_hybrid_v_run_speed(bool in_flight, struct VerticalGuidance *gv)
{
  struct ThrustSetpoint th = guidance_pid_v_run_speed(in_flight, gv);
  return guidance_hybrid_vertical(&th);
}
 
struct ThrustSetpoint guidance_hybrid_v_run_accel(bool in_flight, struct VerticalGuidance *gv)
{
  struct ThrustSetpoint th = guidance_pid_v_run_accel(in_flight, gv);
  return guidance_hybrid_vertical(&th);
}
 
 
void guidance_hybrid_airspeed_to_attitude(struct Int32Eulers *ypr_sp)
{
 
  //notes:
  //in forward flight, it is preferred to first get to min(airspeed_sp, airspeed_ref) and then change heading and then get to airspeed_sp
  //in hover, just a gradual change is needed, or maybe not even needed
  //changes between flight regimes should be handled
 
  //determine the heading of the airspeed_sp vector
  int32_t omega = 0;
  float airspeed_sp_heading = atan2f((float) POS_FLOAT_OF_BFP(guidance_hybrid_airspeed_sp.y),
                                     (float) POS_FLOAT_OF_BFP(guidance_hybrid_airspeed_sp.x));
  //only for debugging
  airspeed_sp_heading_disp = (int32_t)(DegOfRad(airspeed_sp_heading));
 
  //The difference of the current heading with the required heading.
  float heading_diff = airspeed_sp_heading - ANGLE_FLOAT_OF_BFP(ypr_sp->psi);
  FLOAT_ANGLE_NORMALIZE(heading_diff);
 
  //only for debugging
  heading_diff_disp = (int32_t)(heading_diff / 3.14 * 180.0);
 
  //calculate the norm of the airspeed setpoint
  int32_t norm_sp_airspeed;
  norm_sp_airspeed = int32_vect2_norm(&guidance_hybrid_airspeed_sp);
 
  //reference goes with a steady pace towards the setpoint airspeed
  //hold ref norm below 4 m/s until heading is aligned
  if (!((norm_sp_airspeed > (AIRSPEED_HOVER << 8)) && (guidance_hybrid_norm_ref_airspeed < (AIRSPEED_HOVER << 8))
        && (guidance_hybrid_norm_ref_airspeed > ((AIRSPEED_HOVER << 8) - 10)) && (fabs(heading_diff) > (5.0 / 180.0 * 3.14)))) {
    guidance_hybrid_norm_ref_airspeed = guidance_hybrid_norm_ref_airspeed + ((int32_t)(norm_sp_airspeed >
                                        guidance_hybrid_norm_ref_airspeed) * 2 - 1) * 3 / 2;
    guidance_hybrid_norm_ref_airspeed_f = FLOAT_OF_BFP(guidance_hybrid_norm_ref_airspeed, 8);
  }
 
  norm_sp_airspeed_disp = norm_sp_airspeed;
 
  int32_t psi = ypr_sp->psi;
  int32_t s_psi, c_psi;
  PPRZ_ITRIG_SIN(s_psi, psi);
  PPRZ_ITRIG_COS(c_psi, psi);
 
  guidance_hybrid_ref_airspeed.x = (guidance_hybrid_norm_ref_airspeed * c_psi) >> INT32_TRIG_FRAC;
  guidance_hybrid_ref_airspeed.y = (guidance_hybrid_norm_ref_airspeed * s_psi) >> INT32_TRIG_FRAC;
 
  if (guidance_hybrid_norm_ref_airspeed_f < AIRSPEED_HOVER) {
    // translate speed_sp into bank angle and heading
 
    // change heading to direction of airspeed, faster if the airspeed is higher
    if (heading_diff > 0.0) {
      omega = (norm_sp_airspeed << (INT32_ANGLE_FRAC - INT32_POS_FRAC)) / 6;
    } else if (heading_diff < 0.0) {
      omega = (norm_sp_airspeed << (INT32_ANGLE_FRAC - INT32_POS_FRAC)) / -6;
    }
 
    if (omega > ANGLE_BFP_OF_REAL(0.8)) { omega = ANGLE_BFP_OF_REAL(0.8); }
    if (omega < ANGLE_BFP_OF_REAL(-0.8)) { omega = ANGLE_BFP_OF_REAL(-0.8); }
 
    // 2) calculate roll/pitch commands
    struct Int32Vect2 hover_sp;
    //if the setpoint is beyond 4m/s but the ref is not, the norm of the hover sp will stay at 4m/s
    if (norm_sp_airspeed > (AIRSPEED_HOVER << 8)) {
      hover_sp.x = (guidance_hybrid_airspeed_sp.x << 8) / norm_sp_airspeed * AIRSPEED_HOVER;
      hover_sp.y = (guidance_hybrid_airspeed_sp.y << 8) / norm_sp_airspeed * AIRSPEED_HOVER;
    } else {
      hover_sp.x = guidance_hybrid_airspeed_sp.x;
      hover_sp.y = guidance_hybrid_airspeed_sp.y;
    }
 
    // gain of 10 means that for 4 m/s an angle of 40 degrees is needed
    ypr_sp->theta = (((- (c_psi * hover_sp.x + s_psi * hover_sp.y)) >> INT32_TRIG_FRAC) * hover_p_gain * INT32_ANGLE_PI / 180) >> 8;
    ypr_sp->phi = ((((- s_psi * hover_sp.x + c_psi * hover_sp.y)) >> INT32_TRIG_FRAC) * hover_p_gain * INT32_ANGLE_PI / 180) >>  8;
  } else {
    // translate speed_sp into theta + thrust
    // coordinated turns to change heading
 
    // calculate required pitch angle from airspeed_sp magnitude
    if (guidance_hybrid_norm_ref_airspeed_f > AIRSPEED_FORWARD) {
      ypr_sp->theta = -ANGLE_BFP_OF_REAL(RadOfDeg(fwd_nominal_pitch));
    } else {
      float airspeed_transition = (guidance_hybrid_norm_ref_airspeed_f - AIRSPEED_HOVER) / (AIRSPEED_FORWARD - AIRSPEED_HOVER);
      float hover_max_deg = hover_p_gain * AIRSPEED_HOVER;
      float diff_deg = (fwd_nominal_pitch - hover_max_deg) * airspeed_transition;
      ypr_sp->theta = -ANGLE_BFP_OF_REAL(RadOfDeg(diff_deg + hover_max_deg));
    }
 
    // if the sp_airspeed is within hovering range, don't start a coordinated turn
    if (norm_sp_airspeed < (AIRSPEED_HOVER << 8)) {
      omega = 0;
      ypr_sp->phi = 0;
    } else { // coordinated turn
      ypr_sp->phi = ANGLE_BFP_OF_REAL(heading_diff * turn_bank_gain);
      if (ypr_sp->phi > ANGLE_BFP_OF_REAL(max_turn_bank / 180.0 * M_PI)) { ypr_sp->phi = ANGLE_BFP_OF_REAL(max_turn_bank / 180.0 * M_PI); }
      if (ypr_sp->phi < ANGLE_BFP_OF_REAL(-max_turn_bank / 180.0 * M_PI)) { ypr_sp->phi = ANGLE_BFP_OF_REAL(-max_turn_bank / 180.0 * M_PI); }
 
      //feedforward estimate angular rotation omega = g*tan(phi)/v
      omega = ANGLE_BFP_OF_REAL(9.81 / guidance_hybrid_norm_ref_airspeed_f * tanf(ANGLE_FLOAT_OF_BFP(ypr_sp->phi)));
 
      if (omega > ANGLE_BFP_OF_REAL(0.7)) { omega = ANGLE_BFP_OF_REAL(0.7); }
      if (omega < ANGLE_BFP_OF_REAL(-0.7)) { omega = ANGLE_BFP_OF_REAL(-0.7); }
    }
  }
 
  //only for debugging purposes
  omega_disp = omega;
 
  //go to higher resolution because else the increment is too small to be added
  high_res_psi += (omega << (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC)) / 512;
 
  INT32_ANGLE_HIGH_RES_NORMALIZE(high_res_psi);
 
  // go back to angle_frac
  ypr_sp->psi = high_res_psi >> (INT32_ANGLE_HIGH_RES_FRAC - INT32_ANGLE_FRAC);
  ypr_sp->theta = ypr_sp->theta + v_control_pitch;
}
 
void guidance_hybrid_groundspeed_to_airspeed(void)
{
  int32_t norm_groundspeed_sp;
  norm_groundspeed_sp = int32_vect2_norm(&guidance_hybrid_groundspeed_sp);
 
  //create setpoint groundspeed with a norm of 15 m/s
  if (force_forward_flight) {
    //scale the groundspeed_sp to 15 m/s if large enough to begin with
    if (norm_groundspeed_sp > 1 << 8) {
      guidance_hybrid_groundspeed_sp.x = guidance_hybrid_groundspeed_sp.x * (max_airspeed << 8) / norm_groundspeed_sp;
      guidance_hybrid_groundspeed_sp.y = guidance_hybrid_groundspeed_sp.y * (max_airspeed << 8) / norm_groundspeed_sp;
    } else { //groundspeed_sp is very small, so continue with the current heading
      int32_t psi = guidance_hybrid_ypr_sp.psi;
      int32_t s_psi, c_psi;
      PPRZ_ITRIG_SIN(s_psi, psi);
      PPRZ_ITRIG_COS(c_psi, psi);
      guidance_hybrid_groundspeed_sp.x = (max_airspeed * c_psi) >> (INT32_TRIG_FRAC - 8);
      guidance_hybrid_groundspeed_sp.y = (max_airspeed * s_psi) >> (INT32_TRIG_FRAC - 8);
    }
  }
 
  struct Int32Vect2 airspeed_sp;
  INT_VECT2_ZERO(airspeed_sp);
  VECT2_ADD(airspeed_sp, guidance_hybrid_groundspeed_sp);
  VECT2_ADD(airspeed_sp, wind_estimate);
 
  int32_t norm_airspeed_sp;
  norm_airspeed_sp = int32_vect2_norm(&airspeed_sp);
 
  //Check if the airspeed_sp is larger than the max airspeed. If so, give the wind cancellatioin priority.
  if (norm_airspeed_sp > (max_airspeed << 8) && norm_groundspeed_sp > 0) {
    int32_t av = INT_MULT_RSHIFT(guidance_hybrid_groundspeed_sp.x, guidance_hybrid_groundspeed_sp.x,
                                 8) + INT_MULT_RSHIFT(guidance_hybrid_groundspeed_sp.y, guidance_hybrid_groundspeed_sp.y, 8);
    int32_t bv = 2 * (INT_MULT_RSHIFT(wind_estimate.x, guidance_hybrid_groundspeed_sp.x,
                                      8) + INT_MULT_RSHIFT(wind_estimate.y, guidance_hybrid_groundspeed_sp.y, 8));
    int32_t cv = INT_MULT_RSHIFT(wind_estimate.x, wind_estimate.x, 8) + INT_MULT_RSHIFT(wind_estimate.y, wind_estimate.y,
                 8) - (max_airspeed << 8) * max_airspeed;
 
    float dv = POS_FLOAT_OF_BFP(bv) * POS_FLOAT_OF_BFP(bv) - 4.0 * POS_FLOAT_OF_BFP(av) * POS_FLOAT_OF_BFP(cv);
    float d_sqrt_f = sqrtf(dv);
    int32_t d_sqrt = POS_BFP_OF_REAL(d_sqrt_f);
 
    int32_t result = ((-bv + d_sqrt) << 8) / (2 * av);
 
    guidance_hybrid_airspeed_sp.x = wind_estimate.x + INT_MULT_RSHIFT(guidance_hybrid_groundspeed_sp.x, result, 8);
    guidance_hybrid_airspeed_sp.y = wind_estimate.y + INT_MULT_RSHIFT(guidance_hybrid_groundspeed_sp.y, result, 8);
  } else {
    // Add the wind to get the airspeed setpoint
    guidance_hybrid_airspeed_sp = guidance_hybrid_groundspeed_sp;
    VECT2_ADD(guidance_hybrid_airspeed_sp, wind_estimate);
  }
 
  // limit the airspeed setpoint to 15 m/s, because else saturation+windup will occur
  norm_airspeed_sp = int32_vect2_norm(&guidance_hybrid_airspeed_sp);
  // add check for non-zero airspeed (in case the max_airspeed is ever set to zero
  if ((norm_airspeed_sp > (max_airspeed << 8)) && (norm_airspeed_sp != 0)) {
    guidance_hybrid_airspeed_sp.x = guidance_hybrid_airspeed_sp.x * (max_airspeed << 8) / norm_airspeed_sp;
    guidance_hybrid_airspeed_sp.y = guidance_hybrid_airspeed_sp.y * (max_airspeed << 8) / norm_airspeed_sp;
  }
}
 
void guidance_hybrid_determine_wind_estimate(void)
{
 
  /* compute speed error    */
  struct Int32Vect2 wind_estimate_measured;
  struct Int32Vect2 measured_ground_speed;
  INT32_VECT2_RSHIFT(measured_ground_speed, *stateGetSpeedNed_i(), 11);
  VECT2_DIFF(wind_estimate_measured, guidance_hybrid_ref_airspeed, measured_ground_speed);
 
  //Low pass wind_estimate, because we know the wind usually only changes slowly
  //But not too slow, because the wind_estimate is also an adaptive element for the airspeed model inaccuracies
  wind_estimate_high_res.x += (((wind_estimate_measured.x - wind_estimate.x) > 0) * 2 - 1) * wind_gain;
  wind_estimate_high_res.y += (((wind_estimate_measured.y - wind_estimate.y) > 0) * 2 - 1) * wind_gain;
 
  wind_estimate.x = ((wind_estimate_high_res.x) >> 8);
  wind_estimate.y = ((wind_estimate_high_res.y) >> 8);
}
 
struct StabilizationSetpoint guidance_hybrid_set_cmd_i(struct Int32Eulers *sp_cmd)
{
 
  /* orientation vector describing simultaneous rotation of roll/pitch */
  struct FloatVect3 ov;
  ov.x = ANGLE_FLOAT_OF_BFP(sp_cmd->phi);
  ov.y = ANGLE_FLOAT_OF_BFP(sp_cmd->theta);
  ov.z = 0.0;
  /* quaternion from that orientation vector */
  struct FloatQuat q_rp;
  float_quat_of_orientation_vect(&q_rp, &ov);
  struct Int32Quat q_rp_i;
  QUAT_BFP_OF_REAL(q_rp_i, q_rp);
 
  //   get the vertical vector to rotate the roll pitch setpoint around
  struct Int32Vect3 zaxis = {0, 0, 1};
 
  /* get current heading setpoint */
  struct Int32Quat q_yaw_sp;
  int32_quat_of_axis_angle(&q_yaw_sp, &zaxis, sp_cmd->psi);
 
  //   first apply the roll/pitch setpoint and then the yaw
  struct Int32Quat quat_sp;
  int32_quat_comp(&quat_sp, &q_yaw_sp, &q_rp_i);
 
  return stab_sp_from_quat_i(&quat_sp);
}
 
struct ThrustSetpoint guidance_hybrid_vertical(struct ThrustSetpoint *th)
{
  int32_t delta_t = th_sp_to_thrust_i(th, 0, THRUST_AXIS_Z);
  int32_t hybrid_delta_t = 0;
 
  float fwd_speed_err = guidance_hybrid_norm_ref_airspeed_f - AIRSPEED_FORWARD;
  float fwd_thrust = cruise_throttle
                      + (fwd_speed_err * fwd_speed_p_gain)
                      + (delta_t - (MAX_PPRZ * guidance_v.nominal_throttle)) * fwd_alt_thrust_gain;
  int32_t hover_thrust = delta_t;
 
  float alt_control_pitch = (delta_t - MAX_PPRZ * guidance_v.nominal_throttle) * fwd_pitch_gain;
  int32_t fwd_pitch = ANGLE_BFP_OF_REAL(alt_control_pitch / MAX_PPRZ);
 
  /* Hover regime */
  if (guidance_hybrid_norm_ref_airspeed_f < AIRSPEED_HOVER) {
    hybrid_delta_t = hover_thrust;
 
    // Do not control pitch and only PID for hover
    v_control_pitch = 0;
    guidance_pid.kp = GUIDANCE_V_HOVER_KP;
    guidance_pid.kd = GUIDANCE_V_HOVER_KD;
    guidance_pid.ki = GUIDANCE_V_HOVER_KI;
  }
  /* Forward regime */
  else if (guidance_hybrid_norm_ref_airspeed_f > AIRSPEED_FORWARD) {
    hybrid_delta_t  = fwd_thrust;
 
    //Control altitude with pitch, now only proportional control
    v_control_pitch = fwd_pitch;
    guidance_pid.kp = GUIDANCE_V_HOVER_KP / fwd_pid_div;
    guidance_pid.kd = GUIDANCE_V_HOVER_KD / fwd_pid_div;
    guidance_pid.ki = GUIDANCE_V_HOVER_KI / fwd_pid_div;
  }
  /* Transition regime */
  else {
    float airspeed_transition = (guidance_hybrid_norm_ref_airspeed_f - AIRSPEED_HOVER) / (AIRSPEED_FORWARD - AIRSPEED_HOVER); // scaled to 0-1
    hybrid_delta_t = (fwd_thrust * airspeed_transition
        + hover_thrust * (1 - airspeed_transition));
 
    // Control by both thrust and pitch
    v_control_pitch = fwd_pitch * airspeed_transition;
    guidance_pid.kp = GUIDANCE_V_HOVER_KP;
    guidance_pid.kd = GUIDANCE_V_HOVER_KD;
    guidance_pid.ki = GUIDANCE_V_HOVER_KI;
  }
 
  return th_sp_from_thrust_i(hybrid_delta_t, THRUST_AXIS_Z);
}
 
 
#if GUIDANCE_HYBRID_USE_AS_DEFAULT
// guidance hybrid is implementing the default functions of guidance
 
void guidance_h_run_enter(void)
{
  /*Obtain eulers with zxy rotation order*/
  struct FloatEulers eulers_zxy;
  float_eulers_of_quat_zxy(&eulers_zxy, stateGetNedToBodyQuat_f());
  nav.heading = eulers_zxy.psi;
}
 
void guidance_v_run_enter(void)
{
  // nothing to do
}
 
struct StabilizationSetpoint guidance_h_run_pos(bool in_flight, struct HorizontalGuidance *gh)
{
  return guidance_hybrid_h_run_pos(in_flight, gh);
}
 
struct StabilizationSetpoint guidance_h_run_speed(bool in_flight, struct HorizontalGuidance *gh)
{
  return guidance_hybrid_h_run_speed(in_flight, gh);
}
 
struct StabilizationSetpoint guidance_h_run_accel(bool in_flight, struct HorizontalGuidance *gh)
{
  return guidance_hybrid_h_run_accel(in_flight, gh);
}
 
struct ThrustSetpoint guidance_v_run_pos(bool in_flight, struct VerticalGuidance *gv)
{
  return guidance_hybrid_v_run_pos(in_flight, gv);
}
 
struct ThrustSetpoint guidance_v_run_speed(bool in_flight, struct VerticalGuidance *gv)
{
  return guidance_hybrid_v_run_speed(in_flight, gv);
}
 
struct ThrustSetpoint guidance_v_run_accel(bool in_flight, struct VerticalGuidance *gv)
{
  return guidance_hybrid_v_run_accel(in_flight, gv);
}
 
#endif