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ardupilot/ArduCopter/navigation.pde

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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
// update_navigation - checks for new GPS updates and invokes navigation routines
static void update_navigation()
{
static uint32_t nav_last_gps_update = 0; // the system time of the last gps update
static uint32_t nav_last_gps_time = 0; // the time according to the gps
bool pos_updated = false;
bool log_output = false;
// check for new gps data
if( g_gps->fix && g_gps->time != nav_last_gps_time ) {
// used to calculate speed in X and Y, iterms
// ------------------------------------------
dTnav = (float)(millis() - nav_last_gps_update)/ 1000.0;
nav_last_gps_update = millis();
// prevent runup from bad GPS
dTnav = min(dTnav, 1.0);
// save GPS time
nav_last_gps_time = g_gps->time;
// signal to run nav controllers
pos_updated = true;
// signal to create log entry
log_output = true;
}
#if INERTIAL_NAV_XY == ENABLED
// TO-DO: clean this up because inertial nav is overwriting the dTnav and pos_updated from above
// check for inertial nav updates
if( inertial_nav.position_ok() ) {
// 50hz
dTnav = 0.02; // To-Do: calculate the time from the mainloop or INS readings?
// signal to run nav controllers
pos_updated = true;
}
#endif
// calc various navigation values and run controllers if we've received a position update
if( pos_updated ) {
// calculate velocity
calc_velocity_and_position();
// calculate distance, angles to target
calc_distance_and_bearing();
// run navigation controllers
run_navigation_contollers();
// Rotate the nav_lon and nav_lat vectors based on Yaw
calc_nav_pitch_roll();
// update log
if (log_output && (g.log_bitmask & MASK_LOG_NTUN) && motors.armed()) {
Log_Write_Nav_Tuning();
}
}
// reduce nav outputs to zero if we have not received a gps update in 2 seconds
if( millis() - nav_last_gps_update > 2000 ) {
// after 12 reads we guess we may have lost GPS signal, stop navigating
// we have lost GPS signal for a moment. Reduce our error to avoid flyaways
auto_roll >>= 1;
auto_pitch >>= 1;
}
}
//*******************************************************************************************************
// calc_velocity_and_filtered_position - velocity in lon and lat directions calculated from GPS position
// and accelerometer data
// lon_speed expressed in cm/s. positive numbers mean moving east
// lat_speed expressed in cm/s. positive numbers when moving north
// Note: we use gps locations directly to calculate velocity instead of asking gps for velocity because
// this is more accurate below 1.5m/s
// Note: even though the positions are projected using a lead filter, the velocities are calculated
// from the unaltered gps locations. We do not want noise from our lead filter affecting velocity
//*******************************************************************************************************
static void calc_velocity_and_position(){
static int32_t last_gps_longitude = 0;
static int32_t last_gps_latitude = 0;
// initialise last_longitude and last_latitude
if( last_gps_longitude == 0 && last_gps_latitude == 0 ) {
last_gps_longitude = g_gps->longitude;
last_gps_latitude = g_gps->latitude;
}
// this speed is ~ in cm because we are using 10^7 numbers from GPS
float tmp = 1.0/dTnav;
#if INERTIAL_NAV_XY == ENABLED
if( inertial_nav.position_ok() ) {
// pull velocity from interial nav library
lon_speed = inertial_nav.get_longitude_velocity();
lat_speed = inertial_nav.get_latitude_velocity();
// pull position from interial nav library
current_loc.lng = inertial_nav.get_longitude();
current_loc.lat = inertial_nav.get_latitude();
}else{
// calculate velocity
lon_speed = (float)(g_gps->longitude - last_gps_longitude) * scaleLongDown * tmp;
lat_speed = (float)(g_gps->latitude - last_gps_latitude) * tmp;
// calculate position from gps + expected travel during gps_lag
current_loc.lng = xLeadFilter.get_position(g_gps->longitude, lon_speed, g_gps->get_lag());
current_loc.lat = yLeadFilter.get_position(g_gps->latitude, lat_speed, g_gps->get_lag());
}
#else
// calculate velocity
lon_speed = (float)(g_gps->longitude - last_gps_longitude) * scaleLongDown * tmp;
lat_speed = (float)(g_gps->latitude - last_gps_latitude) * tmp;
// calculate position from gps + expected travel during gps_lag
current_loc.lng = xLeadFilter.get_position(g_gps->longitude, lon_speed, g_gps->get_lag());
current_loc.lat = yLeadFilter.get_position(g_gps->latitude, lat_speed, g_gps->get_lag());
#endif
// store gps lat and lon values for next iteration
last_gps_longitude = g_gps->longitude;
last_gps_latitude = g_gps->latitude;
}
//****************************************************************
// Function that will calculate the desired direction to fly and distance
//****************************************************************
static void calc_distance_and_bearing()
{
// waypoint distance from plane in cm
// ---------------------------------------
wp_distance = get_distance_cm(&current_loc, &next_WP);
home_distance = get_distance_cm(&current_loc, &home);
// wp_bearing is bearing to next waypoint
// --------------------------------------------
wp_bearing = get_bearing_cd(&current_loc, &next_WP);
home_bearing = get_bearing_cd(&current_loc, &home);
// bearing to target (used when yaw_mode = YAW_LOOK_AT_LOCATION)
yaw_look_at_WP_bearing = get_bearing_cd(&current_loc, &yaw_look_at_WP);
}
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
}
// called after a GPS read
static void run_navigation_contollers()
{
// wp_distance is in CM
// --------------------
switch(control_mode) {
case AUTO:
// note: wp_control is handled by commands_logic
verify_commands();
// calculates the desired Roll and Pitch
update_nav_wp();
break;
case GUIDED:
wp_control = WP_MODE;
// check if we are close to point > loiter
wp_verify_byte = 0;
verify_nav_wp();
if (wp_control != WP_MODE) {
set_mode(LOITER);
}
update_nav_wp();
break;
case RTL:
// execute the RTL state machine
verify_RTL();
// calculates the desired Roll and Pitch
update_nav_wp();
break;
// switch passthrough to LOITER
case LOITER:
case POSITION:
// This feature allows us to reposition the quad when the user lets
// go of the sticks
if((abs(g.rc_2.control_in) + abs(g.rc_1.control_in)) > 500) {
if(wp_distance > 500){
ap.loiter_override = true;
}
}
// Allow the user to take control temporarily,
if(ap.loiter_override) {
// this sets the copter to not try and nav while we control it
wp_control = NO_NAV_MODE;
// reset LOITER to current position
next_WP.lat = current_loc.lat;
next_WP.lng = current_loc.lng;
if(g.rc_2.control_in == 0 && g.rc_1.control_in == 0) {
wp_control = LOITER_MODE;
ap.loiter_override = false;
}
}else{
wp_control = LOITER_MODE;
}
// calculates the desired Roll and Pitch
update_nav_wp();
break;
case LAND:
verify_land();
// calculates the desired Roll and Pitch
update_nav_wp();
break;
case CIRCLE:
wp_control = CIRCLE_MODE;
update_nav_wp();
break;
case STABILIZE:
case TOY_A:
case TOY_M:
wp_control = NO_NAV_MODE;
update_nav_wp();
break;
}
// are we in SIMPLE mode?
if(ap.simple_mode && g.super_simple) {
// get distance to home
if(home_distance > SUPER_SIMPLE_RADIUS) { // 10m from home
// we reset the angular offset to be a vector from home to the quad
initial_simple_bearing = wrap_360(home_bearing+18000);
//cliSerial->printf("ISB: %d\n", initial_simple_bearing);
}
}
}
// update_nav_wp - high level calculation of nav_lat and nav_lon based on wp_control
// called after gps read from run_navigation_controller
static void update_nav_wp()
{
int16_t loiter_delta;
int16_t speed;
switch( wp_control ) {
case LOITER_MODE:
// calc error to target
calc_location_error(&next_WP);
// use error as the desired rate towards the target
calc_loiter(long_error, lat_error);
break;
case CIRCLE_MODE:
// check if we have missed the WP
loiter_delta = (wp_bearing - old_wp_bearing)/100;
// reset the old value
old_wp_bearing = wp_bearing;
// wrap values
if (loiter_delta > 180) loiter_delta -= 360;
if (loiter_delta < -180) loiter_delta += 360;
// sum the angle around the WP
loiter_sum += loiter_delta;
circle_angle += (circle_rate * dTnav);
//1<> = 0.0174532925 radians
// wrap
if (circle_angle > 6.28318531)
circle_angle -= 6.28318531;
next_WP.lng = circle_WP.lng + (g.loiter_radius * 100 * cos(1.57 - circle_angle) * scaleLongUp);
next_WP.lat = circle_WP.lat + (g.loiter_radius * 100 * sin(1.57 - circle_angle));
// use error as the desired rate towards the target
// nav_lon, nav_lat is calculated
if(wp_distance > 400) {
calc_nav_rate(get_desired_speed(g.waypoint_speed_max));
}else{
// calc the lat and long error to the target
calc_location_error(&next_WP);
calc_loiter(long_error, lat_error);
}
break;
case WP_MODE:
// calc error to target
calc_location_error(&next_WP);
speed = get_desired_speed(g.waypoint_speed_max);
// use error as the desired rate towards the target
calc_nav_rate(speed);
break;
case NO_NAV_MODE:
// clear out our nav so we can do things like land straight down
// or change Loiter position
// We bring copy over our Iterms for wind control, but we don't navigate
nav_lon = g.pid_loiter_rate_lon.get_integrator();
nav_lat = g.pid_loiter_rate_lon.get_integrator();
nav_lon = constrain(nav_lon, -2000, 2000); // 20<32>
nav_lat = constrain(nav_lat, -2000, 2000); // 20<32>
break;
}
}
static bool check_missed_wp()
{
int32_t temp;
temp = wp_bearing - original_wp_bearing;
temp = wrap_180(temp);
return (labs(temp) > 9000); // we passed the waypoint by 100 degrees
}
#define NAV_ERR_MAX 600
#define NAV_RATE_ERR_MAX 250
static void calc_loiter(int16_t x_error, int16_t y_error)
{
int32_t p,i,d; // used to capture pid values for logging
int32_t output;
int32_t x_target_speed, y_target_speed;
// East / West
x_target_speed = g.pi_loiter_lon.get_p(x_error); // calculate desired speed from lon error
#if LOGGING_ENABLED == ENABLED
// log output if PID logging is on and we are tuning the yaw
if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_KP || g.radio_tuning == CH6_LOITER_KI) ) {
Log_Write_PID(CH6_LOITER_KP, x_error, x_target_speed, 0, 0, x_target_speed, tuning_value);
}
#endif
// calculate rate error
x_rate_error = x_target_speed - lon_speed; // calc the speed error
p = g.pid_loiter_rate_lon.get_p(x_rate_error);
i = g.pid_loiter_rate_lon.get_i(x_rate_error + x_error, dTnav);
d = g.pid_loiter_rate_lon.get_d(x_error, dTnav);
d = constrain(d, -2000, 2000);
// get rid of noise
if(abs(lon_speed) < 50) {
d = 0;
}
output = p + i + d;
nav_lon = constrain(output, -32000, 32000); // constraint to remove chance of overflow when adding int32_t to int16_t
#if LOGGING_ENABLED == ENABLED
// log output if PID logging is on and we are tuning the yaw
if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_RATE_KP || g.radio_tuning == CH6_LOITER_RATE_KI || g.radio_tuning == CH6_LOITER_RATE_KD) ) {
Log_Write_PID(CH6_LOITER_RATE_KP, x_rate_error, p, i, d, nav_lon, tuning_value);
}
#endif
// North / South
y_target_speed = g.pi_loiter_lat.get_p(y_error); // calculate desired speed from lat error
#if LOGGING_ENABLED == ENABLED
// log output if PID logging is on and we are tuning the yaw
if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_KP || g.radio_tuning == CH6_LOITER_KI) ) {
Log_Write_PID(CH6_LOITER_KP+100, y_error, y_target_speed, 0, 0, y_target_speed, tuning_value);
}
#endif
// calculate rate error
y_rate_error = y_target_speed - lat_speed; // calc the speed error
p = g.pid_loiter_rate_lat.get_p(y_rate_error);
i = g.pid_loiter_rate_lat.get_i(y_rate_error + y_error, dTnav);
d = g.pid_loiter_rate_lat.get_d(y_error, dTnav);
d = constrain(d, -2000, 2000);
// get rid of noise
if(abs(lat_speed) < 50) {
d = 0;
}
output = p + i + d;
nav_lat = constrain(output, -32000, 32000); // constraint to remove chance of overflow when adding int32_t to int16_t
#if LOGGING_ENABLED == ENABLED
// log output if PID logging is on and we are tuning the yaw
if( g.log_bitmask & MASK_LOG_PID && (g.radio_tuning == CH6_LOITER_RATE_KP || g.radio_tuning == CH6_LOITER_RATE_KI || g.radio_tuning == CH6_LOITER_RATE_KD) ) {
Log_Write_PID(CH6_LOITER_RATE_KP+100, y_rate_error, p, i, d, nav_lat, tuning_value);
}
#endif
// copy over I term to Nav_Rate
g.pid_nav_lon.set_integrator(g.pid_loiter_rate_lon.get_integrator());
g.pid_nav_lat.set_integrator(g.pid_loiter_rate_lat.get_integrator());
}
static void calc_nav_rate(int16_t max_speed)
{
float temp, temp_x, temp_y;
// push us towards the original track
update_crosstrack();
int16_t cross_speed = crosstrack_error * -g.crosstrack_gain; // scale down crosstrack_error in cm
cross_speed = constrain(cross_speed, -150, 150);
// rotate by 90 to deal with trig functions
temp = (9000l - wp_bearing) * RADX100;
temp_x = cos(temp);
temp_y = sin(temp);
// rotate desired spped vector:
int32_t x_target_speed = max_speed * temp_x - cross_speed * temp_y;
int32_t y_target_speed = cross_speed * temp_x + max_speed * temp_y;
// East / West
// calculate rate error
x_rate_error = x_target_speed - lon_speed;
x_rate_error = constrain(x_rate_error, -500, 500);
nav_lon = g.pid_nav_lon.get_pid(x_rate_error, dTnav);
int32_t tilt = (x_target_speed * x_target_speed * (int32_t)g.tilt_comp) / 10000;
if(x_target_speed < 0) tilt = -tilt;
nav_lon += tilt;
// North / South
// calculate rate error
y_rate_error = y_target_speed - lat_speed;
y_rate_error = constrain(y_rate_error, -500, 500); // added a rate error limit to keep pitching down to a minimum
nav_lat = g.pid_nav_lat.get_pid(y_rate_error, dTnav);
tilt = (y_target_speed * y_target_speed * (int32_t)g.tilt_comp) / 10000;
if(y_target_speed < 0) tilt = -tilt;
nav_lat += tilt;
// copy over I term to Loiter_Rate
g.pid_loiter_rate_lon.set_integrator(g.pid_nav_lon.get_integrator());
g.pid_loiter_rate_lat.set_integrator(g.pid_nav_lat.get_integrator());
}
// 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_nav_pitch_roll()
{
//cliSerial->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
auto_roll = (float)nav_lon * sin_yaw_y - (float)nav_lat * cos_yaw_x;
auto_pitch = (float)nav_lon * cos_yaw_x + (float)nav_lat * sin_yaw_y;
// flip pitch because forward is negative
auto_pitch = -auto_pitch;
}
static int16_t get_desired_speed(int16_t max_speed)
{
/*
Based on Equation by Bill Premerlani & Robert Lefebvre
(sq(V2)-sq(V1))/2 = A(X2-X1)
derives to:
V1 = sqrt(sq(V2) - 2*A*(X2-X1))
*/
if(ap.fast_corner) {
// don't slow down
}else{
if(wp_distance < 20000){ // limit the size of numbers we're dealing with to avoid overflow
// go slower
int32_t temp = 2 * 100 * (int32_t)(wp_distance - g.waypoint_radius * 100);
int32_t s_min = WAYPOINT_SPEED_MIN;
temp += s_min * s_min;
max_speed = sqrt((float)temp);
max_speed = min(max_speed, g.waypoint_speed_max);
}
}
max_speed = min(max_speed, max_speed_old + (100 * dTnav));// limit going faster
max_speed = max(max_speed, WAYPOINT_SPEED_MIN); // don't go too slow
max_speed_old = max_speed;
return max_speed;
}
static void reset_desired_speed()
{
max_speed_old = 0;
}
static void update_crosstrack(void)
{
// Crosstrack Error
// ----------------
if (wp_distance >= (g.crosstrack_min_distance * 100) &&
abs(wrap_180(wp_bearing - original_wp_bearing)) < 4500) {
float temp = (wp_bearing - original_wp_bearing) * RADX100;
crosstrack_error = sin(temp) * wp_distance; // Meters we are off track line
}else{
// fade out crosstrack
crosstrack_error >>= 1;
}
}
static int32_t get_altitude_error()
{
// Next_WP alt is our target alt
// It changes based on climb rate
// until it reaches the target_altitude
#if INERTIAL_NAV_Z == ENABLED
// use inertial nav for altitude error
return next_WP.alt - inertial_nav._position.z;
#else
return next_WP.alt - current_loc.alt;
#endif
}
static void clear_new_altitude()
{
set_alt_change(REACHED_ALT);
}
static void force_new_altitude(int32_t new_alt)
{
next_WP.alt = new_alt;
set_alt_change(REACHED_ALT);
}
static void set_new_altitude(int32_t new_alt)
{
next_WP.alt = new_alt;
if(next_WP.alt > (current_loc.alt + 80)) {
// we are below, going up
set_alt_change(ASCENDING);
}else if(next_WP.alt < (current_loc.alt - 80)) {
// we are above, going down
set_alt_change(DESCENDING);
}else{
// No Change
set_alt_change(REACHED_ALT);
}
}
static void verify_altitude()
{
if(alt_change_flag == ASCENDING) {
// we are below, going up
if(current_loc.alt > next_WP.alt - 50) {
set_alt_change(REACHED_ALT);
}
}else if (alt_change_flag == DESCENDING) {
// we are above, going down
if(current_loc.alt <= next_WP.alt + 50){
set_alt_change(REACHED_ALT);
}
}
}
// Keeps old data out of our calculation / logs
static void reset_nav_params(void)
{
// always start Circle mode at same angle
circle_angle = 0;
// We must be heading to a new WP, so XTrack must be 0
crosstrack_error = 0;
// Will be set by new command
wp_bearing = 0;
// Will be set by new command
wp_distance = 0;
// Will be set by new command, used by loiter
long_error = 0;
lat_error = 0;
nav_lon = 0;
nav_lat = 0;
nav_roll = 0;
nav_pitch = 0;
auto_roll = 0;
auto_pitch = 0;
}
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;
}
// get_yaw_slew - reduces rate of change of yaw to a maximum
// assumes it is called at 100hz so centi-degrees and update rate cancel each other out
static int32_t get_yaw_slew(int32_t current_yaw, int32_t desired_yaw, int16_t deg_per_sec)
{
return wrap_360(current_yaw + constrain(wrap_180(desired_yaw - current_yaw), -deg_per_sec, deg_per_sec));
}
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