ardupilot/Tools/ArduTracker/navigation.pde

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-

//****************************************************************
// Function that will calculate the desired direction to fly and altitude error
//****************************************************************
void navigate()
{

	// do not navigate with corrupt data
	// ---------------------------------
	if (gps.fix == 0)
	{
		gps.new_data = false;
		return;
	}
	if(next_WP.lat == 0){
		return;
	}
	// We only perform most nav computations if we have new gps data to work with
	// --------------------------------------------------------------------------
	if(gps.new_data){
		gps.new_data = false;
						
		// target_bearing is where we should be heading 
		// --------------------------------------------
		target_bearing 	= get_bearing(&current_loc, &next_WP);
	
		// nav_bearing will includes xtrac correction
		// ------------------------------------------
		nav_bearing = target_bearing;

		// waypoint distance from plane
		// ----------------------------
		wp_distance = getDistance(&current_loc, &next_WP);
		
		if (wp_distance < 0){
			gcs.send_text(SEVERITY_HIGH,"<navigate> WP error - distance < 0");
			//Serial.println(wp_distance,DEC);
			//print_current_waypoints();
			return;
		}

		// check if we have missed the WP
		loiter_delta = (target_bearing - old_target_bearing)/100;
		
		// reset the old value
		old_target_bearing = target_bearing;
		
		// wrap values
		if (loiter_delta > 180) loiter_delta -= 360;
		if (loiter_delta < -180) loiter_delta += 360;
		loiter_sum += abs(loiter_delta);

		calc_bearing_error();

		// control mode specific updates to nav_bearing
		update_navigation();
	}
}

void update_navigation()
{
	// wp_distance is in ACTUAL meters, not the *100 meters we get from the GPS
	// ------------------------------------------------------------------------

	// distance and bearing calcs only
	if(control_mode == AUTO){
		verify_must();
		verify_may();
	}else{

		switch(control_mode){
			case LOITER:
				update_loiter();
				calc_bearing_error();
				break;
				
			case RTL:
				if(wp_distance <= (get(PARAM_LOITER_RADIUS)) + LOITER_RANGE) { 
					set_mode(LOITER);
				}else{
					update_crosstrack();
				}
				break;							
		}
	}
}


/*
Disabled for now
void calc_distance_error()
{	
	//distance_estimate 	+= (float)gps.ground_speed * .0002f * cosf(radians(bearing_error * .01f));
	//distance_estimate 	-= DST_EST_GAIN * (float)(distance_estimate - GPS_wp_distance);
	//wp_distance  		= max(distance_estimate,10);
}
*/

void calc_airspeed_errors()
{
	if(control_mode>=AUTO && airspeed_nudge > 0) {
		airspeed_error = get(PARAM_TRIM_AIRSPEED) + airspeed_nudge - airspeed;
		airspeed_energy_error = (long)(((long)(get(PARAM_TRIM_AIRSPEED) + airspeed_nudge) * (long)(get(PARAM_TRIM_AIRSPEED) + airspeed_nudge)) - ((long)airspeed * (long)airspeed))/20000; //Changed 0.00005f * to / 20000 to avoid floating point calculation
	} else {
		airspeed_error = get(PARAM_TRIM_AIRSPEED) - airspeed;
		airspeed_energy_error = (long)(((long)get(PARAM_TRIM_AIRSPEED) * (long)get(PARAM_TRIM_AIRSPEED)) - ((long)airspeed * (long)airspeed))/20000; //Changed 0.00005f * to / 20000 to avoid floating point calculation
	}
}

void calc_bearing_error()
{
	if(takeoff_complete == true  || MAGNETOMETER == ENABLED) {
	bearing_error = nav_bearing - dcm.yaw_sensor;
	} else {
		bearing_error = nav_bearing - gps.ground_course;
	}
	bearing_error = wrap_180(bearing_error);
}

void calc_altitude_error() 
{
	// limit climb rates
	target_altitude = next_WP.alt - (long)(((float)((wp_distance -30) * offset_altitude) / (float)(wp_totalDistance - 30)));
	if(prev_WP.alt > next_WP.alt){
		target_altitude = constrain(target_altitude, next_WP.alt, prev_WP.alt);
	}else{
		target_altitude = constrain(target_altitude, prev_WP.alt, next_WP.alt);
	}
	
	/*
	// Disabled for now
	#if AIRSPEED_SENSOR == 1
		// special thanks to Ryan Beall for this one
		float pitch_angle 	= pitch_sensor - AOA; // pitch_angle = pitch sensor - angle of attack of your plane at level *100 (50 = .5°)
		pitch_angle			= constrain(pitch_angle, -2000, 2000);
		float scale			= sinf(radians(pitch_angle * .01));
		altitude_estimate 	+= (float)airspeed * .0002 * scale;
		altitude_estimate 	-= ALT_EST_GAIN * (float)(altitude_estimate - current_loc.alt);
	
		// compute altitude error for throttle control
		altitude_error  = target_altitude - altitude_estimate;
	#else
		altitude_error 	= target_altitude - current_loc.alt;
	#endif
	*/

	altitude_error 	= target_altitude - current_loc.alt;
}


long wrap_360(long error)
{
	if (error > 36000)	error -= 36000;
	if (error < 0)		error += 36000;
	return error;
}

long wrap_180(long error)
{
	if (error > 18000)	error -= 36000;
	if (error < -18000)	error += 36000;
	return error;
}


void update_loiter()
{
	float power;
	if (wp_distance <= get(PARAM_LOITER_RADIUS)){
		power = float(wp_distance) / float(get(PARAM_LOITER_RADIUS));
		nav_bearing += (int)(9000.0 * (2.0 + power));
	} else if (wp_distance < (get(PARAM_LOITER_RADIUS) + LOITER_RANGE)){
		power = -((float)(wp_distance - get(PARAM_LOITER_RADIUS) - LOITER_RANGE) / LOITER_RANGE);
		power = constrain(power, 0, 1);
		nav_bearing -= power * 9000;
	} else {
		update_crosstrack();
	}
	
	nav_bearing = wrap_360(nav_bearing);

/*	loiter_delta = (target_bearing - old_target_bearing)/100;
	// reset the old value
	old_target_bearing = target_bearing;
	// wrap values
	if (loiter_delta > 170) loiter_delta -= 360;
	if (loiter_delta < -170) loiter_delta += 360;
	loiter_sum += loiter_delta;
*/
}

void update_crosstrack(void)
{
	// Crosstrack Error
	// ----------------
	if (abs(target_bearing - crosstrack_bearing) < 4500) {   // If we are too far off or too close we don't do track following
		crosstrack_error = sinf(radians((target_bearing - crosstrack_bearing)/100)) * wp_distance;   // Meters we are off track line
		nav_bearing += constrain(crosstrack_error * get(PARAM_XTRACK_GAIN), -get(PARAM_XTRACK_ANGLE), get(PARAM_XTRACK_ANGLE));
		nav_bearing = wrap_360(nav_bearing);
	}
}

void reset_crosstrack()
{
	crosstrack_bearing 	= get_bearing(&current_loc, &next_WP);	// Used for track following
}

long 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;
}

long getDistance(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 sqrtf(sq(dlat) + sq(dlong)) * .01113195f;
}

long get_alt_distance(struct Location *loc1, struct Location *loc2)
{
	return abs(loc1->alt - loc2->alt);
}

long get_bearing(struct Location *loc1, struct Location *loc2)
{
	long off_x = loc2->lng - loc1->lng;
	long off_y = (loc2->lat - loc1->lat) * scaleLongUp;
	long bearing =  9000 + atan2f(-off_y, off_x) * 5729.57795f;
	if (bearing < 0) bearing += 36000;
	return bearing;
}