ardupilot/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp

130 lines
4.3 KiB
C++

/*
* ADC.cpp - Analog Digital Converter Base Class for Ardupilot Mega
* Code by James Goppert. DIYDrones.com
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*/
#include "AP_OpticalFlow.h"
#define FORTYFIVE_DEGREES 0.78539816
// pointer to the last instantiated optical flow sensor. Will be turned into
// a table if we ever add support for more than one sensor
AP_OpticalFlow* AP_OpticalFlow::_sensor = NULL;
// number of times we have been called by 1khz timer process.
// We use this to throttle read down to 20hz
uint8_t AP_OpticalFlow::_num_calls;
bool AP_OpticalFlow::init()
{
_orientation = ROTATION_NONE;
update_conversion_factors();
return true; // just return true by default
}
// set_orientation - Rotation vector to transform sensor readings to the body
// frame.
void AP_OpticalFlow::set_orientation(enum Rotation rotation)
{
_orientation = rotation;
}
// parent method called at 1khz by periodic process
// this is slowed down to 20hz and each instance's update function is called
// (only one instance is supported at the moment)
void AP_OpticalFlow::read(uint32_t now)
{
_num_calls++;
if( _num_calls >= AP_OPTICALFLOW_NUM_CALLS_FOR_20HZ ) {
_num_calls = 0;
// call to update all attached sensors
if( _sensor != NULL ) {
_sensor->update(now);
}
}
};
// read value from the sensor. Should be overridden by derived class
void AP_OpticalFlow::update(uint32_t now){ }
// reads a value from the sensor (will be sensor specific)
uint8_t AP_OpticalFlow::read_register(uint8_t address){ return 0; }
// writes a value to one of the sensor's register (will be sensor specific)
void AP_OpticalFlow::write_register(uint8_t address, uint8_t value) {}
// rotate raw values to arrive at final x,y,dx and dy values
void AP_OpticalFlow::apply_orientation_matrix()
{
Vector3f rot_vector;
rot_vector(raw_dx, raw_dy, 0);
// next rotate dx and dy
rot_vector.rotate(_orientation);
dx = rot_vector.x;
dy = rot_vector.y;
// add rotated values to totals (perhaps this is pointless as we need
// to take into account yaw, roll, pitch)
x += dx;
y += dy;
}
// updates conversion factors that are dependent upon field_of_view
void AP_OpticalFlow::update_conversion_factors()
{
// multiply this number by altitude and pixel change to get horizontal
// move (in same units as altitude)
conv_factor = ((1.0 / (float)(num_pixels * scaler))
* 2.0 * tan(field_of_view / 2.0));
// 0.00615
radians_to_pixels = (num_pixels * scaler) / field_of_view;
// 162.99
}
// updates internal lon and lat with estimation based on optical flow
void AP_OpticalFlow::update_position(float roll, float pitch,
float cos_yaw_x, float sin_yaw_y, float altitude)
{
float diff_roll = roll - _last_roll;
float diff_pitch = pitch - _last_pitch;
// only update position if surface quality is good and angle is not
// over 45 degrees
if( surface_quality >= 10 && fabs(roll) <= FORTYFIVE_DEGREES
&& fabs(pitch) <= FORTYFIVE_DEGREES ) {
altitude = max(altitude, 0);
// calculate expected x,y diff due to roll and pitch change
exp_change_x = diff_roll * radians_to_pixels;
exp_change_y = -diff_pitch * radians_to_pixels;
// real estimated raw change from mouse
change_x = dx - exp_change_x;
change_y = dy - exp_change_y;
float avg_altitude = (altitude + _last_altitude)*0.5;
// convert raw change to horizontal movement in cm
// perhaps this altitude should actually be the distance to the
// ground? i.e. if we are very rolled over it should be longer?
x_cm = -change_x * avg_altitude * conv_factor;
// for example if you are leaned over at 45 deg the ground will
// appear farther away and motion from opt flow sensor will be less
y_cm = -change_y * avg_altitude * conv_factor;
// convert x/y movements into lon/lat movement
vlon = x_cm * sin_yaw_y + y_cm * cos_yaw_x;
vlat = y_cm * sin_yaw_y - x_cm * cos_yaw_x;
}
_last_altitude = altitude;
_last_roll = roll;
_last_pitch = pitch;
}