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LibrePilot/flight/Libraries/paths.c

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/**
******************************************************************************
*
* @file paths.c
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2012.
* @brief Library path manipulation
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "pios.h"
#include "paths.h"
/**
* @brief Compute progress along path and deviation from it
* @param[in] start_point Starting point
* @param[in] end_point Ending point
* @param[in] cur_point Current location
* @param[out] status Structure containing progress along path and deviation
*/
void path_progress(float * start_point, float * end_point, float * cur_point, struct path_status * status)
{
float path_north, path_east, diff_north, diff_east;
float dist_path2;
float dot;
float normal[2];
// Distance to go
path_north = end_point[0] - start_point[0];
path_east = end_point[1] - start_point[1];
// Current progress location relative to start
diff_north = cur_point[0] - start_point[0];
diff_east = cur_point[1] - start_point[1];
dot = path_north * diff_north + path_east * diff_east;
dist_path2 = path_north * path_north + path_east * path_east;
// Compute the normal to the path
normal[0] = -path_east / sqrtf(dist_path2);
normal[1] = path_north / sqrtf(dist_path2);
status->fractional_progress = dot / dist_path2;
status->error = normal[0] * diff_north + normal[1] * diff_east;
// Compute direction to correct error
status->correction_direction[0] = -status->error * normal[0];
status->correction_direction[1] = -status->error * normal[1];
// Compute direction to travel
status->path_direction[0] = path_north / sqrtf(dist_path2);
status->path_direction[1] = path_east / sqrtf(dist_path2);
status->error = fabs(status->error);
}