ardupilot/ArduCopter/navigation.pde

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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
//****************************************************************
// Function that will calculate the desired direction to fly and distance
//****************************************************************
static byte navigate()
{
// waypoint distance from plane
// ----------------------------
wp_distance = get_distance(&current_loc, &next_WP);
home_distance = get_distance(&current_loc, &home);
if (wp_distance < 0){
//gcs_send_text_P(SEVERITY_HIGH,PSTR("<navigate> WP error - distance < 0"));
//Serial.println(wp_distance,DEC);
//print_current_waypoints();
return 0;
}
// target_bearing is where we should be heading
// --------------------------------------------
target_bearing = get_bearing(&current_loc, &next_WP);
home_to_copter_bearing = get_bearing(&home, &current_loc);
// nav_bearing will includes xtrac correction
// ------------------------------------------
nav_bearing = target_bearing;
return 1;
}
static bool check_missed_wp()
{
int32_t temp;
temp = target_bearing - original_target_bearing;
temp = wrap_180(temp);
return (abs(temp) > 10000); //we pased the waypoint by 10 °
}
// ------------------------------
static void calc_XY_velocity(){
// offset calculation of GPS speed:
// used for estimations below 1.5m/s
// our GPS is about 1m per
static int32_t last_longitude = 0;
static int32_t last_latutude = 0;
// y_GPS_speed positve = Up
// x_GPS_speed positve = Right
// this speed is ~ in cm because we are using 10^7 numbers from GPS
float tmp = 1.0/dTnav;
//int8_t tmp = 5;
int16_t x_diff = (g_gps->longitude - last_longitude) * tmp;
int16_t y_diff = (g_gps->latitude - last_latutude) * tmp;
// filter
x_GPS_speed = (x_GPS_speed * 3 + x_diff) / 4;
y_GPS_speed = (y_GPS_speed * 3 + y_diff) / 4;
// Above simply works better than GPS groundspeed
// which is proving to be problematic
/*if(g_gps->ground_speed > 120){
// Derive X/Y speed from GPS
// this is far more accurate when traveling about 1.5m/s
float temp = g_gps->ground_course * RADX100;
x_GPS_speed = sin(temp) * (float)g_gps->ground_speed;
y_GPS_speed = cos(temp) * (float)g_gps->ground_speed;
}*/
last_longitude = g_gps->longitude;
last_latutude = g_gps->latitude;
//Serial.printf("GS: %d \tx:%d \ty:%d\n", g_gps->ground_speed, x_GPS_speed, y_GPS_speed);
}
static void calc_location_error(struct Location *next_loc)
{
/*
Becuase we are using lat and lon to do our distance errors here's a quick chart:
100 = 1m
1000 = 11m = 36 feet
1800 = 19.80m = 60 feet
3000 = 33m
10000 = 111m
*/
// X Error
long_error = (float)(next_loc->lng - current_loc.lng) * scaleLongDown; // 500 - 0 = 500 Go East
// Y Error
lat_error = next_loc->lat - current_loc.lat; // 500 - 0 = 500 Go North
}
#define NAV_ERR_MAX 800
static void calc_loiter(int x_error, int y_error)
{
// East/West
x_error = constrain(x_error, -NAV_ERR_MAX, NAV_ERR_MAX); //800
int16_t x_target_speed = g.pi_loiter_lon.get_p(x_error);
int16_t x_iterm = g.pi_loiter_lon.get_i(x_error, dTnav);
x_rate_error = x_target_speed - x_actual_speed;
nav_lon_p = g.pi_nav_lon.get_p(x_rate_error);
nav_lon_p = constrain(nav_lon_p, -1200, 1200);
nav_lon = nav_lon_p + x_iterm;
nav_lon = constrain(nav_lon, -2500, 2500);
// North/South
y_error = constrain(y_error, -NAV_ERR_MAX, NAV_ERR_MAX);
int16_t y_target_speed = g.pi_loiter_lat.get_p(y_error);
int16_t y_iterm = g.pi_loiter_lat.get_i(y_error, dTnav);
y_rate_error = y_target_speed - y_actual_speed;
nav_lat_p = g.pi_nav_lat.get_p(y_rate_error);
nav_lat_p = constrain(nav_lat_p, -1200, 1200);
nav_lat = nav_lat_p + y_iterm;
nav_lat = constrain(nav_lat, -2500, 2500);
/*
int8_t ttt = 1.0/dTnav;
int16_t t2 = g.pi_nav_lat.get_integrator();
// 1 2 3 4 5 6 7 8 9 10
Serial.printf("%d, %d, %d, %d, %d, %d, %d, %d, %d, %d\n",
wp_distance, //1
y_error, //2
y_GPS_speed, //3
y_actual_speed, //4 ;
y_target_speed, //5
y_rate_error, //6
nav_lat_p, //7
nav_lat, //8
y_iterm, //9
t2); //10
//*/
/*
int16_t t1 = g.pi_nav_lon.get_integrator(); // X
Serial.printf("%d, %1.4f, %d, %d, %d, %d, %d, %d, %d, %d\n",
wp_distance, //1
dTnav, //2
x_error, //3
x_GPS_speed, //4
x_actual_speed, //5
x_target_speed, //6
x_rate_error, //7
nav_lat, //8
x_iterm, //9
t1); //10
//*/
}
//wp_distance,ttt, y_error, y_GPS_speed, y_actual_speed, y_target_speed, y_rate_error, nav_lat, y_iterm, t2
#define ERR_GAIN .01
// called at 50hz
static void estimate_velocity()
{
// we need to extimate velocity when below GPS threshold of 1.5m/s
//if(g_gps->ground_speed < 120){
// some smoothing to prevent bumpy rides
x_actual_speed = (x_actual_speed * 15 + x_GPS_speed) / 16;
y_actual_speed = (y_actual_speed * 15 + y_GPS_speed) / 16;
// integration of nav_p angle
//x_actual_speed += (nav_lon_p >>2);
//y_actual_speed += (nav_lat_p >>2);
// this is just what worked best in SIM
//x_actual_speed = (x_actual_speed * 2 + x_GPS_speed * 1) / 4;
//y_actual_speed = (y_actual_speed * 2 + y_GPS_speed * 1) / 4;
//}else{
// less smoothing needed since the GPS already filters
// x_actual_speed = (x_actual_speed * 3 + x_GPS_speed) / 4;
// y_actual_speed = (y_actual_speed * 3 + y_GPS_speed) / 4;
//}
}
// this calculation rotates our World frame of reference to the copter's frame of reference
// We use the DCM's matrix to precalculate these trig values at 50hz
static void calc_loiter_pitch_roll()
{
//Serial.printf("ys %ld, cx %1.4f, _cx %1.4f | sy %1.4f, _sy %1.4f\n", dcm.yaw_sensor, cos_yaw_x, _cos_yaw_x, sin_yaw_y, _sin_yaw_y);
// rotate the vector
nav_roll = (float)nav_lon * sin_yaw_y - (float)nav_lat * cos_yaw_x;
nav_pitch = (float)nav_lon * cos_yaw_x + (float)nav_lat * sin_yaw_y;
// flip pitch because forward is negative
nav_pitch = -nav_pitch;
}
// what's the update rate? 10hz GPS?
static void calc_wind_compensation()
{
// this idea is a function that converts user input into I term for position hold
// the concept is simple. The iterms always act upon flight no matter what mode were in.
// when our velocity is 0, we call this function to update our iterms
// otherwise we slowly reduce out iterms to 0
// take the pitch and roll of the copter and,
float roll = dcm.roll_sensor;
float pitch = -dcm.pitch_sensor; // flip pitch to make positive pitch forward
// rotate it to eliminate yaw of Copter
int32_t roll_tmp = roll * sin_yaw_y - pitch * -cos_yaw_x;
int32_t pitch_tmp = roll * -cos_yaw_x + pitch * sin_yaw_y;
roll_tmp = constrain(roll_tmp, -2000, 2000);
pitch_tmp = constrain(pitch_tmp, -2000, 2000);
// filter the input and apply it to out integrator value
// nav_lon and nav_lat will be applied to normal flight
nav_lon = ((int32_t)g.pi_loiter_lon.get_integrator() * 15 + roll_tmp) / 16;
nav_lat = ((int32_t)g.pi_loiter_lat.get_integrator() * 15 + pitch_tmp) / 16;
// save smoothed input to integrator
g.pi_loiter_lon.set_integrator(nav_lon); // X
g.pi_loiter_lat.set_integrator(nav_lat); // Y
//Serial.printf("build wind iterm X:%d Y:%d, r:%d, p:%d\n",
// nav_lon,
// nav_lat,
// nav_roll,
// nav_pitch);
}
static void reduce_wind_compensation()
{
//slow degradation of iterms
float tmp;
tmp = g.pi_loiter_lon.get_integrator();
tmp *= .98;
g.pi_loiter_lon.set_integrator(tmp); // X
tmp = g.pi_loiter_lat.get_integrator();
tmp *= .98;
g.pi_loiter_lat.set_integrator(tmp); // Y
#if 0
// debug
int16_t t1 = g.pi_loiter_lon.get_integrator();
int16_t t2 = g.pi_loiter_lon.get_integrator();
//Serial.printf("reduce wind iterm X:%d Y:%d \n",
// t1,
// t2);
#endif
}
static int16_t calc_desired_speed(int16_t max_speed)
{
/*
|< WP Radius
0 1 2 3 4 5 6 7 8m
...|...|...|...|...|...|...|...|
100 | 200 300 400cm/s
| +|+
|< we should slow to 1.5 m/s as we hit the target
*/
// max_speed is default 600 or 6m/s
// (wp_distance * 50) = 1/2 of the distance converted to speed
// wp_distance is always in m/s and not cm/s - I know it's stupid that way
// for example 4m from target = 200cm/s speed
// we choose the lowest speed based on disance
max_speed = min(max_speed, (wp_distance * 50));
// limit the ramp up of the speed
// waypoint_speed_gov is reset to 0 at each new WP command
if(waypoint_speed_gov < max_speed){
waypoint_speed_gov += (int)(50.0 * dTnav); // increase at .5/ms
// go at least 50cm/s
max_speed = max(50, waypoint_speed_gov);
// limit with governer
max_speed = min(max_speed, waypoint_speed_gov);
}
return max_speed;
}
static void calc_nav_rate(int max_speed)
{
// push us towards the original track
update_crosstrack();
// nav_bearing includes crosstrack
float temp = (9000 - nav_bearing) * RADX100;
x_rate_error = (cos(temp) * max_speed) - x_actual_speed; // 413
x_rate_error = constrain(x_rate_error, -1000, 1000);
int16_t x_iterm = g.pi_loiter_lon.get_i(x_rate_error, dTnav);
nav_lon_p = g.pi_nav_lon.get_p(x_rate_error);
nav_lon = nav_lon_p + x_iterm;
nav_lon = constrain(nav_lon, -3000, 3000);
y_rate_error = (sin(temp) * max_speed) - y_actual_speed; // 413
y_rate_error = constrain(y_rate_error, -1000, 1000); // added a rate error limit to keep pitching down to a minimum
int16_t y_iterm = g.pi_loiter_lat.get_i(y_rate_error, dTnav);
nav_lat_p = g.pi_nav_lat.get_p(y_rate_error);
nav_lat = nav_lat_p + y_iterm;
nav_lat = constrain(nav_lat, -3000, 3000);
/*
Serial.printf("max_sp %d,\t x_sp %d, y_sp %d,\t x_re: %d, y_re: %d, \tnav_lon: %d, nav_lat: %d, Xi:%d, Yi:%d, \t XE %d \n",
max_speed,
x_actual_speed,
y_actual_speed,
x_rate_error,
y_rate_error,
nav_lon,
nav_lat,
x_iterm,
y_iterm,
crosstrack_error);
//*/
// nav_lat and nav_lon will be rotated to the angle of the quad in calc_nav_pitch_roll()
/*Serial.printf("max_speed: %d, xspeed: %d, yspeed: %d, x_re: %d, y_re: %d, nav_lon: %ld, nav_lat: %ld ",
max_speed,
x_actual_speed,
y_actual_speed,
x_rate_error,
y_rate_error,
nav_lon,
nav_lat);*/
}
static void update_crosstrack(void)
{
// Crosstrack Error
// ----------------
if (abs(wrap_180(target_bearing - original_target_bearing)) < 4500) { // If we are too far off or too close we don't do track following
float temp = (target_bearing - original_target_bearing) * RADX100;
crosstrack_error = sin(temp) * (wp_distance * g.crosstrack_gain); // Meters we are off track line
nav_bearing = target_bearing + constrain(crosstrack_error, -3000, 3000);
nav_bearing = wrap_360(nav_bearing);
}else{
nav_bearing = target_bearing;
}
}
static int32_t get_altitude_error()
{
return next_WP.alt - current_loc.alt;
}
static int32_t wrap_360(int32_t error)
{
if (error > 36000) error -= 36000;
if (error < 0) error += 36000;
return error;
}
static int32_t wrap_180(int32_t error)
{
if (error > 18000) error -= 36000;
if (error < -18000) error += 36000;
return error;
}
/*
//static int32_t get_altitude_above_home(void)
{
// This is the altitude above the home location
// The GPS gives us altitude at Sea Level
// if you slope soar, you should see a negative number sometimes
// -------------------------------------------------------------
return current_loc.alt - home.alt;
}
*/
// distance is returned in meters
static int32_t get_distance(struct Location *loc1, struct Location *loc2)
{
//if(loc1->lat == 0 || loc1->lng == 0)
// return -1;
//if(loc2->lat == 0 || loc2->lng == 0)
// return -1;
float dlat = (float)(loc2->lat - loc1->lat);
float dlong = ((float)(loc2->lng - loc1->lng)) * scaleLongDown;
return sqrt(sq(dlat) + sq(dlong)) * .01113195;
}
/*
//static int32_t get_alt_distance(struct Location *loc1, struct Location *loc2)
{
return abs(loc1->alt - loc2->alt);
}
*/
static int32_t get_bearing(struct Location *loc1, struct Location *loc2)
{
int32_t off_x = loc2->lng - loc1->lng;
int32_t off_y = (loc2->lat - loc1->lat) * scaleLongUp;
int32_t bearing = 9000 + atan2(-off_y, off_x) * 5729.57795;
if (bearing < 0) bearing += 36000;
return bearing;
}