flight/libraries/paths.c

   1 /**
   2  ******************************************************************************
   3  *
   4  * @file       paths.c
   5  * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2012.
   6  * @brief      Library path manipulation
   7  *
   8  * @see        The GNU Public License (GPL) Version 3
   9  *
  10  *****************************************************************************/
  11 /*
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 3 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  19  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  20  * for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  25  */
  26
  27 #include <pios.h>
  28 #include <pios_math.h>
  29 #include <mathmisc.h>
  30
  31 #include "uavobjectmanager.h" // <--.
  32 #include "pathdesired.h" // <-- needed only for correct ENUM macro usage with path modes (PATHDESIRED_MODE_xxx,
  33 #include "paths.h"
  34 // no direct UAVObject usage allowed in this file
  35
  36 // private functions
  37 static void path_endpoint(PathDesiredData *path, float *cur_point, struct path_status *status, bool mode);
  38 static void path_vector(PathDesiredData *path, float *cur_point, struct path_status *status, bool mode);
  39 static void path_circle(PathDesiredData *path, float *cur_point, struct path_status *status, bool clockwise);
  40
  41 /**
  42  * @brief Compute progress along path and deviation from it
  43  * @param[in] path  PathDesired structure
  44  * @param[in] cur_point Current location
  45  * @param[out] status Structure containing progress along path and deviation
  46  */
  47 void path_progress(PathDesiredData *path, float *cur_point, struct path_status *status)
  48 {
  49     switch (path->Mode) {
  50     case PATHDESIRED_MODE_FLYVECTOR:
  51         return path_vector(path, cur_point, status, true);
  52
  53         break;
  54     case PATHDESIRED_MODE_DRIVEVECTOR:
  55         return path_vector(path, cur_point, status, false);
  56
  57         break;
  58     case PATHDESIRED_MODE_FLYCIRCLERIGHT:
  59     case PATHDESIRED_MODE_DRIVECIRCLERIGHT:
  60         return path_circle(path, cur_point, status, 1);
  61
  62         break;
  63     case PATHDESIRED_MODE_FLYCIRCLELEFT:
  64     case PATHDESIRED_MODE_DRIVECIRCLELEFT:
  65         return path_circle(path, cur_point, status, 0);
  66
  67         break;
  68     case PATHDESIRED_MODE_FLYENDPOINT:
  69         return path_endpoint(path, cur_point, status, true);
  70
  71         break;
  72     case PATHDESIRED_MODE_DRIVEENDPOINT:
  73     default:
  74         // use the endpoint as default failsafe if called in unknown modes
  75         return path_endpoint(path, cur_point, status, false);
  76
  77         break;
  78     }
  79 }
  80
  81 /**
  82  * @brief Compute progress towards endpoint. Deviation equals distance
  83  * @param[in] path PathDesired
  84  * @param[in] cur_point Current location
  85  * @param[out] status Structure containing progress along path and deviation
  86  * @param[in] mode3D set true to include altitude in distance and progress calculation
  87  */
  88 static void path_endpoint(PathDesiredData *path, float *cur_point, struct path_status *status, bool mode3D)
  89 {
  90     float diff[3];
  91     float dist_path, dist_diff;
  92
  93     // Distance to go
  94     status->path_vector[0] = path->End.North - path->Start.North;
  95     status->path_vector[1] = path->End.East - path->Start.East;
  96     status->path_vector[2] = mode3D ? path->End.Down - path->Start.Down : 0.0f;
  97
  98     // Current progress location relative to end
  99     diff[0]   = path->End.North - cur_point[0];
 100     diff[1]   = path->End.East - cur_point[1];
 101     diff[2]   = mode3D ? path->End.Down - cur_point[2] : 0.0f;
 102
 103     dist_diff = vector_lengthf(diff, 3);
 104     dist_path = vector_lengthf(status->path_vector, 3);
 105
 106     if (dist_diff < 1e-6f) {
 107         status->fractional_progress  = 1;
 108         status->error = 0.0f;
 109         status->correction_vector[0] = status->correction_vector[1] = status->correction_vector[2] = 0.0f;
 110         // we have no base movement direction in this mode
 111         status->path_vector[0] = status->path_vector[1] = status->path_vector[2] = 0.0f;
 112
 113         return;
 114     }
 115
 116     if (fmaxf(dist_path, 1.0f) > dist_diff) {
 117         status->fractional_progress = 1 - dist_diff / fmaxf(dist_path, 1.0f);
 118     } else {
 119         status->fractional_progress = 0; // we don't want fractional_progress to become negative
 120     }
 121     status->error = dist_diff;
 122
 123     // Compute correction vector
 124     status->correction_vector[0] = diff[0];
 125     status->correction_vector[1] = diff[1];
 126     status->correction_vector[2] = diff[2];
 127
 128     // base movement direction in this mode is a constant velocity offset on top of correction in the same direction
 129     status->path_vector[0] = path->EndingVelocity * status->correction_vector[0] / dist_diff;
 130     status->path_vector[1] = path->EndingVelocity * status->correction_vector[1] / dist_diff;
 131     status->path_vector[2] = path->EndingVelocity * status->correction_vector[2] / dist_diff;
 132 }
 133
 134 /**
 135  * @brief Compute progress along path and deviation from it
 136  * @param[in] path PathDesired
 137  * @param[in] cur_point Current location
 138  * @param[out] status Structure containing progress along path and deviation
 139  * @param[in] mode3D set true to include altitude in distance and progress calculation
 140  */
 141 static void path_vector(PathDesiredData *path, float *cur_point, struct path_status *status, bool mode3D)
 142 {
 143     float diff[3];
 144     float dist_path;
 145     float dot;
 146     float velocity;
 147     float track_point[3];
 148
 149     // Distance to go
 150     status->path_vector[0] = path->End.North - path->Start.North;
 151     status->path_vector[1] = path->End.East - path->Start.East;
 152     status->path_vector[2] = mode3D ? path->End.Down - path->Start.Down : 0.0f;
 153
 154     // Current progress location relative to start
 155     diff[0]   = cur_point[0] - path->Start.North;
 156     diff[1]   = cur_point[1] - path->Start.East;
 157     diff[2]   = mode3D ? cur_point[2] - path->Start.Down : 0.0f;
 158
 159     dot       = status->path_vector[0] * diff[0] + status->path_vector[1] * diff[1] + status->path_vector[2] * diff[2];
 160     dist_path = vector_lengthf(status->path_vector, 3);
 161
 162     if (dist_path > 1e-6f) {
 163         // Compute direction to travel & progress
 164         status->fractional_progress = dot / (dist_path * dist_path);
 165     } else {
 166         // Fly towards the endpoint to prevent flying away,
 167         // but assume progress=1 either way.
 168         path_endpoint(path, cur_point, status, mode3D);
 169         status->fractional_progress = 1;
 170         return;
 171     }
 172     // Compute point on track that is closest to our current position.
 173     track_point[0] = status->fractional_progress * status->path_vector[0] + path->Start.North;
 174     track_point[1] = status->fractional_progress * status->path_vector[1] + path->Start.East;
 175     track_point[2] = status->fractional_progress * status->path_vector[2] + path->Start.Down;
 176
 177     status->correction_vector[0] = track_point[0] - cur_point[0];
 178     status->correction_vector[1] = track_point[1] - cur_point[1];
 179     status->correction_vector[2] = track_point[2] - cur_point[2];
 180
 181     status->error = vector_lengthf(status->correction_vector, 3);
 182
 183     // correct movement vector to current velocity
 184     velocity = path->StartingVelocity + boundf(status->fractional_progress, 0.0f, 1.0f) * (path->EndingVelocity - path->StartingVelocity);
 185     status->path_vector[0] = velocity * status->path_vector[0] / dist_path;
 186     status->path_vector[1] = velocity * status->path_vector[1] / dist_path;
 187     status->path_vector[2] = velocity * status->path_vector[2] / dist_path;
 188 }
 189
 190 /**
 191  * @brief Compute progress along circular path and deviation from it
 192  * @param[in] path PathDesired
 193  * @param[in] cur_point Current location
 194  * @param[out] status Structure containing progress along path and deviation
 195  */
 196 static void path_circle(PathDesiredData *path, float *cur_point, struct path_status *status, bool clockwise)
 197 {
 198     float radius_north, radius_east, diff_north, diff_east, diff_down;
 199     float radius, cradius;
 200     float normal[2];
 201     float progress;
 202     float a_diff, a_radius;
 203
 204     // Radius
 205     radius_north = path->End.North - path->Start.North;
 206     radius_east  = path->End.East - path->Start.East;
 207
 208     // Current location relative to center
 209     diff_north   = cur_point[0] - path->End.North;
 210     diff_east    = cur_point[1] - path->End.East;
 211     diff_down    = cur_point[2] - path->End.Down;
 212
 213     radius  = sqrtf(squaref(radius_north) + squaref(radius_east));
 214     cradius = sqrtf(squaref(diff_north) + squaref(diff_east));
 215
 216     // circles are always horizontal (for now - TODO: allow 3d circles - problem: clockwise/counterclockwise does no longer apply)
 217     status->path_vector[2] = 0.0f;
 218
 219     // error is current radius minus wanted radius - positive if too close
 220     status->error = radius - cradius;
 221
 222     if (cradius < 1e-6f) {
 223         // cradius is zero, just fly somewhere
 224         status->fractional_progress  = 1;
 225         status->correction_vector[0] = 0;
 226         status->correction_vector[1] = 0;
 227         status->path_vector[0] = path->EndingVelocity;
 228         status->path_vector[1] = 0;
 229     } else {
 230         if (clockwise) {
 231             // Compute the normal to the radius clockwise
 232             normal[0] = -diff_east / cradius;
 233             normal[1] = diff_north / cradius;
 234         } else {
 235             // Compute the normal to the radius counter clockwise
 236             normal[0] = diff_east / cradius;
 237             normal[1] = -diff_north / cradius;
 238         }
 239
 240         // normalize progress to 0..1
 241         a_diff   = atan2f(diff_north, diff_east);
 242         a_radius = atan2f(radius_north, radius_east);
 243
 244         if (a_diff < 0) {
 245             a_diff += 2.0f * M_PI_F;
 246         }
 247         if (a_radius < 0) {
 248             a_radius += 2.0f * M_PI_F;
 249         }
 250
 251         progress = (a_diff - a_radius + M_PI_F) / (2.0f * M_PI_F);
 252
 253         if (progress < 0.0f) {
 254             progress += 1.0f;
 255         } else if (progress >= 1.0f) {
 256             progress -= 1.0f;
 257         }
 258
 259         if (clockwise) {
 260             progress = 1.0f - progress;
 261         }
 262
 263         status->fractional_progress = progress;
 264
 265         // Compute direction to travel
 266         status->path_vector[0] = normal[0] * path->EndingVelocity;
 267         status->path_vector[1] = normal[1] * path->EndingVelocity;
 268
 269         // Compute direction to correct error
 270         status->correction_vector[0] = status->error * diff_north / cradius;
 271         status->correction_vector[1] = status->error * diff_east / cradius;
 272     }
 273
 274     status->correction_vector[2] = -diff_down;
 275
 276     status->error = fabs(status->error);
 277 }