/// Utility function: converts lla (int) to local point (float)
bool_t mission_point_of_lla(struct EnuCoor_f *point, struct LlaCoor_i *lla)
{
  // return FALSE if there is no valid local coordinate system
  if (!state.ned_initialized_i) {
    return FALSE;
  }

  // change geoid alt to ellipsoid alt
  lla->alt = lla->alt - state.ned_origin_i.hmsl + state.ned_origin_i.lla.alt;

  //Compute ENU components from LLA with respect to ltp origin
  struct EnuCoor_i tmp_enu_point_i;
  enu_of_lla_point_i(&tmp_enu_point_i, &state.ned_origin_i, lla);
  struct EnuCoor_f tmp_enu_point_f;
  ENU_FLOAT_OF_BFP(tmp_enu_point_f, tmp_enu_point_i);

  //Bound the new waypoint with max distance from home
  struct EnuCoor_f home;
  ENU_FLOAT_OF_BFP(home, waypoints[WP_HOME]);
  struct FloatVect2 vect_from_home;
  VECT2_DIFF(vect_from_home, tmp_enu_point_f, home);
  //Saturate the mission wp not to overflow max_dist_from_home
  //including a buffer zone before limits
  float dist_to_home = float_vect2_norm(&vect_from_home);
  dist_to_home += BUFFER_ZONE_DIST;
  if (dist_to_home > MAX_DIST_FROM_HOME) {
    VECT2_SMUL(vect_from_home, vect_from_home, (MAX_DIST_FROM_HOME / dist_to_home));
  }
  // set new point
  VECT2_SUM(*point, home, vect_from_home);
  point->z = tmp_enu_point_f.z;

  return TRUE;
}
Esempio n. 2
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void nav_route(struct EnuCoor_i *wp_start, struct EnuCoor_i *wp_end)
{
  struct Int32Vect2 wp_diff, pos_diff, wp_diff_prec;
  VECT2_DIFF(wp_diff, *wp_end, *wp_start);
  VECT2_DIFF(pos_diff, *stateGetPositionEnu_i(), *wp_start);
  // go back to metric precision or values are too large
  VECT2_COPY(wp_diff_prec, wp_diff);
  INT32_VECT2_RSHIFT(wp_diff, wp_diff, INT32_POS_FRAC);
  INT32_VECT2_RSHIFT(pos_diff, pos_diff, INT32_POS_FRAC);
  uint32_t leg_length2 = Max((wp_diff.x * wp_diff.x + wp_diff.y * wp_diff.y), 1);
  nav_leg_length = int32_sqrt(leg_length2);
  nav_leg_progress = (pos_diff.x * wp_diff.x + pos_diff.y * wp_diff.y) / nav_leg_length;
  int32_t progress = Max((CARROT_DIST >> INT32_POS_FRAC), 0);
  nav_leg_progress += progress;
  int32_t prog_2 = nav_leg_length;
  Bound(nav_leg_progress, 0, prog_2);
  struct Int32Vect2 progress_pos;
  VECT2_SMUL(progress_pos, wp_diff_prec, ((float)nav_leg_progress) / nav_leg_length);
  VECT2_SUM(navigation_target, *wp_start, progress_pos);

  nav_segment_start = *wp_start;
  nav_segment_end = *wp_end;
  horizontal_mode = HORIZONTAL_MODE_ROUTE;

  dist2_to_wp = get_dist2_to_point(wp_end);
}
Esempio n. 3
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static void compute_points_from_bungee(void)
{
  // Store init point (current position, where the plane will be released)
  VECT2_ASSIGN(init_point, stateGetPositionEnu_f()->x, stateGetPositionEnu_f()->y);
  // Compute unitary 2D vector (bungee_point - init_point) = takeoff direction
  VECT2_DIFF(takeoff_dir, bungee_point, init_point);
  float_vect2_normalize(&takeoff_dir);
  // Find throttle point (the point where the throttle line and launch line intersect)
  // If TakeOff_Distance is positive, throttle point is after bungee point, before otherwise
  VECT2_SMUL(throttle_point, takeoff_dir, BUNGEE_TAKEOFF_DISTANCE);
  VECT2_SUM(throttle_point, bungee_point, throttle_point);
}
Esempio n. 4
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void nav_circle(struct EnuCoor_i * wp_center, int32_t radius) {
  if (radius == 0) {
    VECT2_COPY(navigation_target, *wp_center);
    dist2_to_wp = get_dist2_to_point(wp_center);
  }
  else {
    struct Int32Vect2 pos_diff;
    VECT2_DIFF(pos_diff, *stateGetPositionEnu_i(), *wp_center);
    // go back to half metric precision or values are too large
    //INT32_VECT2_RSHIFT(pos_diff,pos_diff,INT32_POS_FRAC/2);
    // store last qdr
    int32_t last_qdr = nav_circle_qdr;
    // compute qdr
    nav_circle_qdr = int32_atan2(pos_diff.y, pos_diff.x);
    // increment circle radians
    if (nav_circle_radians != 0) {
      int32_t angle_diff = nav_circle_qdr - last_qdr;
      INT32_ANGLE_NORMALIZE(angle_diff);
      nav_circle_radians += angle_diff;
    }
    else {
      // Smallest angle to increment at next step
      nav_circle_radians = 1;
    }

    // direction of rotation
    int8_t sign_radius = radius > 0 ? 1 : -1;
    // absolute radius
    int32_t abs_radius = abs(radius);
    // carrot_angle
    int32_t carrot_angle = ((CARROT_DIST<<INT32_ANGLE_FRAC) / abs_radius);
    Bound(carrot_angle, (INT32_ANGLE_PI / 16), INT32_ANGLE_PI_4);
    carrot_angle = nav_circle_qdr - sign_radius * carrot_angle;
    int32_t s_carrot, c_carrot;
    PPRZ_ITRIG_SIN(s_carrot, carrot_angle);
    PPRZ_ITRIG_COS(c_carrot, carrot_angle);
    // compute setpoint
    VECT2_ASSIGN(pos_diff, abs_radius * c_carrot, abs_radius * s_carrot);
    INT32_VECT2_RSHIFT(pos_diff, pos_diff, INT32_TRIG_FRAC);
    VECT2_SUM(navigation_target, *wp_center, pos_diff);
  }
  nav_circle_center = *wp_center;
  nav_circle_radius = radius;
  horizontal_mode = HORIZONTAL_MODE_CIRCLE;
}
Esempio n. 5
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bool_t nav_approaching_from(struct EnuCoor_i *wp, struct EnuCoor_i *from, int16_t approaching_time)
{
  int32_t dist_to_point;
  struct Int32Vect2 diff;
  struct EnuCoor_i *pos = stateGetPositionEnu_i();

  /* if an approaching_time is given, estimate diff after approching_time secs */
  if (approaching_time > 0) {
    struct Int32Vect2 estimated_pos;
    struct Int32Vect2 estimated_progress;
    struct EnuCoor_i *speed = stateGetSpeedEnu_i();
    VECT2_SMUL(estimated_progress, *speed, approaching_time);
    INT32_VECT2_RSHIFT(estimated_progress, estimated_progress, (INT32_SPEED_FRAC - INT32_POS_FRAC));
    VECT2_SUM(estimated_pos, *pos, estimated_progress);
    VECT2_DIFF(diff, *wp, estimated_pos);
  }
  /* else use current position */
  else {
    VECT2_DIFF(diff, *wp, *pos);
  }
  /* compute distance of estimated/current pos to target wp
   * distance with half metric precision (6.25 cm)
   */
  INT32_VECT2_RSHIFT(diff, diff, INT32_POS_FRAC / 2);
  dist_to_point = int32_vect2_norm(&diff);

  /* return TRUE if we have arrived */
  if (dist_to_point < BFP_OF_REAL(ARRIVED_AT_WAYPOINT, INT32_POS_FRAC / 2)) {
    return TRUE;
  }

  /* if coming from a valid waypoint */
  if (from != NULL) {
    /* return TRUE if normal line at the end of the segment is crossed */
    struct Int32Vect2 from_diff;
    VECT2_DIFF(from_diff, *wp, *from);
    INT32_VECT2_RSHIFT(from_diff, from_diff, INT32_POS_FRAC / 2);
    return (diff.x * from_diff.x + diff.y * from_diff.y < 0);
  }

  return FALSE;
}
Esempio n. 6
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static inline void UNUSED nav_advance_carrot(void)
{
  struct EnuCoor_i *pos = stateGetPositionEnu_i();
  /* compute a vector to the waypoint */
  struct Int32Vect2 path_to_waypoint;
  VECT2_DIFF(path_to_waypoint, navigation_target, *pos);

  /* saturate it */
  VECT2_STRIM(path_to_waypoint, -(1 << 15), (1 << 15));

  int32_t dist_to_waypoint = int32_vect2_norm(&path_to_waypoint);

  if (dist_to_waypoint < CLOSE_TO_WAYPOINT) {
    VECT2_COPY(navigation_carrot, navigation_target);
  } else {
    struct Int32Vect2 path_to_carrot;
    VECT2_SMUL(path_to_carrot, path_to_waypoint, CARROT_DIST);
    VECT2_SDIV(path_to_carrot, path_to_carrot, dist_to_waypoint);
    VECT2_SUM(navigation_carrot, path_to_carrot, *pos);
  }
}
Esempio n. 7
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/**
 * main navigation routine. This is called periodically evaluates the current
 * Position and stage and navigates accordingly.
 * @returns True until the survey is finished
 */
bool nav_survey_polygon_run(void)
{
    NavVerticalAutoThrottleMode(0.0);
    NavVerticalAltitudeMode(survey.psa_altitude, 0.0);

    //entry circle around entry-center until the desired altitude is reached
    if (survey.stage == ENTRY) {
        nav_circle_XY(survey.entry_center.x, survey.entry_center.y, -survey.psa_min_rad);
        if (NavCourseCloseTo(survey.segment_angle)
                && nav_approaching_xy(survey.seg_start.x, survey.seg_start.y, last_x, last_y, CARROT)
                && fabs(stateGetPositionUtm_f()->alt - survey.psa_altitude) <= 20) {
            survey.stage = SEG;
            nav_init_stage();
#ifdef DIGITAL_CAM
            dc_survey(survey.psa_shot_dist, survey.seg_start.x - survey.dir_vec.x * survey.psa_shot_dist * 0.5,
                      survey.seg_start.y - survey.dir_vec.y * survey.psa_shot_dist * 0.5);
#endif
        }
    }
    //fly the segment until seg_end is reached
    if (survey.stage == SEG) {
        nav_points(survey.seg_start, survey.seg_end);
        //calculate all needed points for the next flyover
        if (nav_approaching_xy(survey.seg_end.x, survey.seg_end.y, survey.seg_start.x, survey.seg_start.y, 0)) {
#ifdef DIGITAL_CAM
            dc_stop();
#endif
            VECT2_DIFF(survey.seg_center1, survey.seg_end, survey.rad_vec);
            survey.ret_start.x = survey.seg_end.x - 2 * survey.rad_vec.x;
            survey.ret_start.y = survey.seg_end.y - 2 * survey.rad_vec.y;

            //if we get no intersection the survey is finished
            static struct FloatVect2 sum_start_sweep;
            static struct FloatVect2 sum_end_sweep;
            VECT2_SUM(sum_start_sweep, survey.seg_start, survey.sweep_vec);
            VECT2_SUM(sum_end_sweep, survey.seg_end, survey.sweep_vec);
            if (!get_two_intersects(&survey.seg_start, &survey.seg_end, sum_start_sweep, sum_end_sweep)) {
                return false;
            }

            survey.ret_end.x = survey.seg_start.x - survey.sweep_vec.x - 2 * survey.rad_vec.x;
            survey.ret_end.y = survey.seg_start.y - survey.sweep_vec.y - 2 * survey.rad_vec.y;

            survey.seg_center2.x = survey.seg_start.x - 0.5 * (2.0 * survey.rad_vec.x + survey.sweep_vec.x);
            survey.seg_center2.y = survey.seg_start.y - 0.5 * (2.0 * survey.rad_vec.y + survey.sweep_vec.y);

            survey.stage = TURN1;
            nav_init_stage();
        }
    }
    //turn from stage to return
    else if (survey.stage == TURN1) {
        nav_circle_XY(survey.seg_center1.x, survey.seg_center1.y, -survey.psa_min_rad);
        if (NavCourseCloseTo(survey.return_angle)) {
            survey.stage = RET;
            nav_init_stage();
        }
        //return
    } else if (survey.stage == RET) {
        nav_points(survey.ret_start, survey.ret_end);
        if (nav_approaching_xy(survey.ret_end.x, survey.ret_end.y, survey.ret_start.x, survey.ret_start.y, 0)) {
            survey.stage = TURN2;
            nav_init_stage();
        }
        //turn from return to stage
    } else if (survey.stage == TURN2) {
        nav_circle_XY(survey.seg_center2.x, survey.seg_center2.y, -(2 * survey.psa_min_rad + survey.psa_sweep_width) * 0.5);
        if (NavCourseCloseTo(survey.segment_angle)) {
            survey.stage = SEG;
            nav_init_stage();
#ifdef DIGITAL_CAM
            dc_survey(survey.psa_shot_dist, survey.seg_start.x - survey.dir_vec.x * survey.psa_shot_dist * 0.5,
                      survey.seg_start.y - survey.dir_vec.y * survey.psa_shot_dist * 0.5);
#endif
        }
    }

    return true;
}
Esempio n. 8
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/**
 *  initializes the variables needed for the survey to start
 *  @param first_wp      the first Waypoint of the polygon
 *  @param size          the number of points that make up the polygon
 *  @param angle         angle in which to do the flyovers
 *  @param sweep_width   distance between the sweeps
 *  @param shot_dist     distance between the shots
 *  @param min_rad       minimal radius when navigating
 *  @param altitude      the altitude that must be reached before the flyover starts
 **/
void nav_survey_polygon_setup(uint8_t first_wp, uint8_t size, float angle, float sweep_width, float shot_dist,
                              float min_rad, float altitude)
{
    int i;
    struct FloatVect2 small, sweep;
    float divider, angle_rad = angle / 180.0 * M_PI;

    if (angle < 0.0) {
        angle += 360.0;
    }
    if (angle >= 360.0) {
        angle -= 360.0;
    }

    survey.poly_first = first_wp;
    survey.poly_count = size;

    survey.psa_sweep_width = sweep_width;
    survey.psa_min_rad = min_rad;
    survey.psa_shot_dist = shot_dist;
    survey.psa_altitude = altitude;

    survey.segment_angle = angle;
    survey.return_angle = angle + 180;
    if (survey.return_angle > 359) {
        survey.return_angle -= 360;
    }

    if (angle <= 45.0 || angle >= 315.0) {
        //north
        survey.dir_vec.y = 1.0;
        survey.dir_vec.x = 1.0 * tanf(angle_rad);
        sweep.x = 1.0;
        sweep.y = - survey.dir_vec.x / survey.dir_vec.y;
    } else if (angle <= 135.0) {
        //east
        survey.dir_vec.x = 1.0;
        survey.dir_vec.y = 1.0 / tanf(angle_rad);
        sweep.y = - 1.0;
        sweep.x = survey.dir_vec.y / survey.dir_vec.x;
    } else if (angle <= 225.0) {
        //south
        survey.dir_vec.y = -1.0;
        survey.dir_vec.x = -1.0 * tanf(angle_rad);
        sweep.x = -1.0;
        sweep.y = survey.dir_vec.x / survey.dir_vec.y;
    } else {
        //west
        survey.dir_vec.x = -1.0;
        survey.dir_vec.y = -1.0 / tanf(angle_rad);
        sweep.y = 1.0;
        sweep.x = - survey.dir_vec.y / survey.dir_vec.x;
    }

    //normalize
    FLOAT_VECT2_NORMALIZE(sweep);

    VECT2_SMUL(survey.rad_vec, sweep, survey.psa_min_rad);
    VECT2_SMUL(survey.sweep_vec, sweep, survey.psa_sweep_width);

    //begin at leftmost position (relative to survey.dir_vec)
    VECT2_COPY(small, waypoints[survey.poly_first]);

    divider = (survey.sweep_vec.y * survey.dir_vec.x) - (survey.sweep_vec.x * survey.dir_vec.y);

    //calculate the leftmost point if one sees the dir vec as going "up" and the sweep vec as going right
    if (divider < 0.0) {
        for (i = 1; i < survey.poly_count; i++)
            if ((survey.dir_vec.x * (waypoints[survey.poly_first + i].y - small.y)) + (survey.dir_vec.y *
                    (small.x - waypoints[survey.poly_first + i].x)) > 0.0) {
                VECT2_COPY(small, waypoints[survey.poly_first + i]);
            }
    } else
        for (i = 1; i < survey.poly_count; i++)
            if ((survey.dir_vec.x * (waypoints[survey.poly_first + i].y - small.y)) + (survey.dir_vec.y *
                    (small.x - waypoints[survey.poly_first + i].x)) > 0.0) {
                VECT2_COPY(small, waypoints[survey.poly_first + i]);
            }

    //calculate the line the defines the first flyover
    survey.seg_start.x = small.x + 0.5 * survey.sweep_vec.x;
    survey.seg_start.y = small.y + 0.5 * survey.sweep_vec.y;
    VECT2_SUM(survey.seg_end, survey.seg_start, survey.dir_vec);

    if (!get_two_intersects(&survey.seg_start, &survey.seg_end, survey.seg_start, survey.seg_end)) {
        survey.stage = ERR;
        return;
    }

    //center of the entry circle
    VECT2_DIFF(survey.entry_center, survey.seg_start, survey.rad_vec);

    //fast climbing to desired altitude
    NavVerticalAutoThrottleMode(0.0);
    NavVerticalAltitudeMode(survey.psa_altitude, 0.0);

    survey.stage = ENTRY;
}
Esempio n. 9
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/**
 * initializes the variables needed for the survey to start.
 *
 * @param center_wp     the waypoint defining the center of the survey-rectangle
 * @param dir_wp        the waypoint defining the orientation of the survey-rectangle
 * @param sweep_length  the length of the survey-rectangle
 * @param sweep_spacing distance between the sweeps
 * @param sweep_lines   number of sweep_lines to fly
 * @param altitude      the altitude that must be reached before the flyover starts
 */
bool_t nav_survey_zamboni_setup(uint8_t center_wp, uint8_t dir_wp, float sweep_length, float sweep_spacing, int sweep_lines, float altitude)
{
  zs.current_laps = 0;
  zs.pre_leave_angle = 2;

  // copy variables from the flight plan
  VECT2_COPY(zs.wp_center, waypoints[center_wp]);
  VECT2_COPY(zs.wp_dir, waypoints[dir_wp]);
  zs.altitude = altitude;

  // if turning right leave circle before angle is reached, if turning left - leave after
  if (sweep_spacing > 0) {
    zs.pre_leave_angle -= zs.pre_leave_angle;
  }

  struct FloatVect2 flight_vec;
  VECT2_DIFF(flight_vec, zs.wp_dir, zs.wp_center);
  FLOAT_VECT2_NORMALIZE(flight_vec);

  // calculate the flight_angle
  zs.flight_angle = DegOfRad(atan2(flight_vec.x, flight_vec.y));
  zs.return_angle = zs.flight_angle + 180;
  if (zs.return_angle > 359) {
    zs.return_angle -= 360;
  }

  // calculate the vector from one flightline perpendicular to the next flightline left,
  // seen in the flightdirection. (Delta x and delta y betwen two adjecent flightlines)
  // (used later to move the flight pattern one flightline up for each round)
  zs.sweep_width.x = -flight_vec.y * sweep_spacing;
  zs.sweep_width.y = +flight_vec.x * sweep_spacing;

  // calculate number of laps to fly and turning radius for each end
  zs.total_laps = (sweep_lines+1)/2;
  zs.turnradius1 = (zs.total_laps-1) * sweep_spacing * 0.5;
  zs.turnradius2 = zs.total_laps * sweep_spacing * 0.5;

  struct FloatVect2 flight_line;
  VECT2_SMUL(flight_line, flight_vec, sweep_length * 0.5);

  //CALCULATE THE NAVIGATION POINTS
  //start and end of flight-line in flight-direction
  VECT2_DIFF(zs.seg_start, zs.wp_center, flight_line);
  VECT2_SUM(zs.seg_end, zs.wp_center, flight_line);

  struct FloatVect2 sweep_span;
  VECT2_SMUL(sweep_span, zs.sweep_width, zs.total_laps-1);
  //start and end of flight-line in return-direction
  VECT2_DIFF(zs.ret_start, zs.seg_end, sweep_span);
  VECT2_DIFF(zs.ret_end, zs.seg_start, sweep_span);

  //turn-centers at both ends
  zs.turn_center1.x = (zs.seg_end.x + zs.ret_start.x) / 2.0;
  zs.turn_center1.y = (zs.seg_end.y + zs.ret_start.y) / 2.0;
  zs.turn_center2.x = (zs.seg_start.x + zs.ret_end.x + zs.sweep_width.x) / 2.0;
  zs.turn_center2.y = (zs.seg_start.y + zs.ret_end.y + zs.sweep_width.y) / 2.0;

  //fast climbing to desired altitude
  NavVerticalAutoThrottleMode(100.0);
  NavVerticalAltitudeMode(zs.altitude, 0.0);

  zs.stage = Z_ENTRY;

  return FALSE;
}
Esempio n. 10
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void gh_update_ref_from_pos_sp(struct Int32Vect2 pos_sp) {

  VECT2_ADD(gh_pos_ref, gh_speed_ref);
  VECT2_ADD(gh_speed_ref, gh_accel_ref);

  // compute the "speed part" of accel = -2*zeta*omega*speed -omega^2(pos - pos_sp)
  struct Int32Vect2 speed;
  INT32_VECT2_RSHIFT(speed, gh_speed_ref, (GH_SPEED_REF_FRAC - GH_ACCEL_REF_FRAC));
  VECT2_SMUL(speed, speed, -2*GH_ZETA_OMEGA);
  INT32_VECT2_RSHIFT(speed, speed, GH_ZETA_OMEGA_FRAC);
  // compute pos error in pos_sp resolution
  struct Int32Vect2 pos_err;
  INT32_VECT2_RSHIFT(pos_err, gh_pos_ref, (GH_POS_REF_FRAC - INT32_POS_FRAC));
  VECT2_DIFF(pos_err, pos_err, pos_sp);
  // convert to accel resolution
  INT32_VECT2_RSHIFT(pos_err, pos_err, (INT32_POS_FRAC - GH_ACCEL_REF_FRAC));
  // compute the "pos part" of accel
  struct Int32Vect2 pos;
  VECT2_SMUL(pos, pos_err, (-GH_OMEGA_2));
  INT32_VECT2_RSHIFT(pos, pos, GH_OMEGA_2_FRAC);
  // sum accel
  VECT2_SUM(gh_accel_ref, speed, pos);

  /* Compute route reference before saturation */
  // use metric precision or values are too large
  INT32_ATAN2(route_ref, -pos_err.y, -pos_err.x);
  /* Compute North and East route components */
  PPRZ_ITRIG_SIN(s_route_ref, route_ref);
  PPRZ_ITRIG_COS(c_route_ref, route_ref);
  c_route_ref = abs(c_route_ref);
  s_route_ref = abs(s_route_ref);
  /* Compute maximum acceleration*/
  gh_max_accel_ref.x = INT_MULT_RSHIFT((int32_t)GH_MAX_ACCEL, c_route_ref, INT32_TRIG_FRAC);
  gh_max_accel_ref.y = INT_MULT_RSHIFT((int32_t)GH_MAX_ACCEL, s_route_ref, INT32_TRIG_FRAC);
  /* Compute maximum speed*/
  gh_max_speed_ref.x = INT_MULT_RSHIFT((int32_t)GH_MAX_SPEED, c_route_ref, INT32_TRIG_FRAC);
  gh_max_speed_ref.y = INT_MULT_RSHIFT((int32_t)GH_MAX_SPEED, s_route_ref, INT32_TRIG_FRAC);
  /* restore gh_speed_ref range (Q14.17) */
  INT32_VECT2_LSHIFT(gh_max_speed_ref, gh_max_speed_ref, (GH_SPEED_REF_FRAC - GH_MAX_SPEED_REF_FRAC));

 /* Saturate accelerations */
  if (gh_accel_ref.x <= -gh_max_accel_ref.x) {
    gh_accel_ref.x = -gh_max_accel_ref.x;
  }
  else if (gh_accel_ref.x >=  gh_max_accel_ref.x) {
    gh_accel_ref.x =  gh_max_accel_ref.x;
  }
  if (gh_accel_ref.y <= -gh_max_accel_ref.y) {
    gh_accel_ref.y = -gh_max_accel_ref.y;
  }
  else if (gh_accel_ref.y >= gh_max_accel_ref.y) {
    gh_accel_ref.y = gh_max_accel_ref.y;
  }

  /* Saturate speed and adjust acceleration accordingly */
  if (gh_speed_ref.x <= -gh_max_speed_ref.x) {
    gh_speed_ref.x = -gh_max_speed_ref.x;
    if (gh_accel_ref.x < 0)
      gh_accel_ref.x = 0;
  }
  else if (gh_speed_ref.x >=  gh_max_speed_ref.x) {
    gh_speed_ref.x =  gh_max_speed_ref.x;
    if (gh_accel_ref.x > 0)
      gh_accel_ref.x = 0;
  }
  if (gh_speed_ref.y <= -gh_max_speed_ref.y) {
    gh_speed_ref.y = -gh_max_speed_ref.y;
    if (gh_accel_ref.y < 0)
      gh_accel_ref.y = 0;
  }
  else if (gh_speed_ref.y >= gh_max_speed_ref.y) {
    gh_speed_ref.y = gh_max_speed_ref.y;
    if (gh_accel_ref.y > 0)
      gh_accel_ref.y = 0;
  }
}