px4_autopilot/apps/multirotor_pos_control/position_control.c

/****************************************************************************
 *
 *   Copyright (C) 2008-2012 PX4 Development Team. All rights reserved.
 *   Author: @author Lorenz Meier <lm@inf.ethz.ch>
 *           @author Laurens Mackay <mackayl@student.ethz.ch>
 *           @author Tobias Naegeli <naegelit@student.ethz.ch>
 *           @author Martin Rutschmann <rutmarti@student.ethz.ch>
 *
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 * modification, are permitted provided that the following conditions
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 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file multirotor_position_control.c
 * Implementation of the position control for a multirotor VTOL
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <stdbool.h>
#include <float.h>
#include <systemlib/pid/pid.h>

#include "multirotor_position_control.h"

float get_distance_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next)
{
	double lat_now_rad = lat_now / 180.0 * M_PI;
	double lon_now_rad = lon_now / 180.0 * M_PI;
	double lat_next_rad = lat_next / 180.0 * M_PI;
	double lon_next_rad = lon_next / 180.0 * M_PI;


	double d_lat = lat_next_rad - lat_now_rad;
	double d_lon = lon_next_rad - lon_now_rad;

	double a = sin(d_lat / 2.0) * sin(d_lat / 2.0) + sin(d_lon / 2.0) * sin(d_lon / 2.0) * cos(lat_now_rad) * cos(lat_next_rad);
	double c = 2 * atan2(sqrt(a), sqrt(1 - a));

	const double radius_earth = 6371000.0;

	return radius_earth * c;
}

float get_bearing_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next)
{
	double lat_now_rad = lat_now / 180.0 * M_PI;
	double lon_now_rad = lon_now / 180.0 * M_PI;
	double lat_next_rad = lat_next / 180.0 * M_PI;
	double lon_next_rad = lon_next / 180.0 * M_PI;

	double d_lat = lat_next_rad - lat_now_rad;
	double d_lon = lon_next_rad - lon_now_rad;

	/* conscious mix of double and float trig function to maximize speed and efficiency */
	float theta = atan2f(sin(d_lon) * cos(lat_next_rad) , cos(lat_now_rad) * sin(lat_next_rad) - sin(lat_now_rad) * cos(lat_next_rad) * cos(d_lon));

	// XXX wrapping check is incomplete
	if (theta < 0.0f) {
		theta = theta + 2.0f * M_PI_F;
	}

	return theta;
}

void control_multirotor_position(const struct vehicle_state_s *vstatus, const struct vehicle_manual_control_s *manual,
 const struct vehicle_attitude_s *att, const struct vehicle_local_position_s *local_pos,
 const struct vehicle_local_position_setpoint_s *local_pos_sp, struct vehicle_attitude_setpoint_s *att_sp)
{
	static PID_t distance_controller;

	static int read_ret;
	static global_data_position_t position_estimated;

	static uint16_t counter;

	static bool initialized;
	static uint16_t pm_counter;

	static float lat_next;
	static float lon_next;

	static float pitch_current;

	static float thrust_total;


	if (initialized == false) {

		pid_init(&distance_controller,
			 global_data_parameter_storage->pm.param_values[PARAM_PID_POS_P],
			 global_data_parameter_storage->pm.param_values[PARAM_PID_POS_I],
			 global_data_parameter_storage->pm.param_values[PARAM_PID_POS_D],
			 global_data_parameter_storage->pm.param_values[PARAM_PID_POS_AWU],
			 PID_MODE_DERIVATIV_CALC, 150);//150

//		pid_pos_lim = global_data_parameter_storage->pm.param_values[PARAM_PID_POS_LIM];
//		pid_pos_z_lim = global_data_parameter_storage->pm.param_values[PARAM_PID_POS_Z_LIM];

		thrust_total = 0.0f;

		/* Position initialization */
		/* Wait for new position estimate */
		do {
			read_ret = read_lock_position(&position_estimated);
		} while (read_ret != 0);

		lat_next = position_estimated.lat;
		lon_next = position_estimated.lon;

		/* attitude initialization */
		global_data_lock(&global_data_attitude->access_conf);
		pitch_current = global_data_attitude->pitch;
		global_data_unlock(&global_data_attitude->access_conf);

		initialized = true;
	}

	/* load new parameters with 10Hz */
	if (counter % 50 == 0) {
		if (global_data_trylock(&global_data_parameter_storage->access_conf) == 0) {
			/* check whether new parameters are available */
			if (global_data_parameter_storage->counter > pm_counter) {
				pid_set_parameters(&distance_controller,
						   global_data_parameter_storage->pm.param_values[PARAM_PID_POS_P],
						   global_data_parameter_storage->pm.param_values[PARAM_PID_POS_I],
						   global_data_parameter_storage->pm.param_values[PARAM_PID_POS_D],
						   global_data_parameter_storage->pm.param_values[PARAM_PID_POS_AWU]);

//
//				pid_pos_lim = global_data_parameter_storage->pm.param_values[PARAM_PID_POS_LIM];
//				pid_pos_z_lim = global_data_parameter_storage->pm.param_values[PARAM_PID_POS_Z_LIM];

				pm_counter = global_data_parameter_storage->counter;
				printf("Position controller changed pid parameters\n");
			}
		}

		global_data_unlock(&global_data_parameter_storage->access_conf);
	}


	/* Wait for new position estimate */
	do {
		read_ret = read_lock_position(&position_estimated);
	} while (read_ret != 0);

	/* Get next waypoint */ //TODO: add local copy

	if (0 == global_data_trylock(&global_data_position_setpoint->access_conf)) {
		lat_next = global_data_position_setpoint->x;
		lon_next = global_data_position_setpoint->y;
		global_data_unlock(&global_data_position_setpoint->access_conf);
	}

	/* Get distance to waypoint */
	float distance_to_waypoint = get_distance_to_next_waypoint(position_estimated.lat , position_estimated.lon, lat_next, lon_next);
//	if(counter % 5 == 0)
//		printf("distance_to_waypoint: %.4f\n", distance_to_waypoint);

	/* Get bearing to waypoint (direction on earth surface to next waypoint) */
	float bearing = get_bearing_to_next_waypoint(position_estimated.lat, position_estimated.lon, lat_next, lon_next);

	if (counter % 5 == 0)
		printf("bearing: %.4f\n", bearing);

	/* Calculate speed in direction of bearing (needed for controller) */
	float speed_norm = sqrtf(position_estimated.vx  * position_estimated.vx + position_estimated.vy * position_estimated.vy);
//	if(counter % 5 == 0)
//		printf("speed_norm: %.4f\n", speed_norm);
	float speed_to_waypoint = 0; //(position_estimated.vx * cosf(bearing) + position_estimated.vy * sinf(bearing))/speed_norm; //FIXME, TODO: re-enable this once we have a full estimate of the speed, then we can do a PID for the distance controller

	/* Control Thrust in bearing direction  */
	float horizontal_thrust = -pid_calculate(&distance_controller, 0, distance_to_waypoint, speed_to_waypoint,
				  CONTROL_PID_POSITION_INTERVAL); //TODO: maybe this "-" sign is an error somewhere else

//	if(counter % 5 == 0)
//		printf("horizontal thrust: %.4f\n", horizontal_thrust);

	/* Get total thrust (from remote for now) */
	if (0 == global_data_trylock(&global_data_rc_channels->access_conf)) {
		thrust_total = (float)global_data_rc_channels->chan[THROTTLE].scale; 												//TODO: how should we use the RC_CHANNELS_FUNCTION enum?
		global_data_unlock(&global_data_rc_channels->access_conf);
	}

	const float max_gas = 500.0f;
	thrust_total *= max_gas / 20000.0f; //TODO: check this
	thrust_total += max_gas / 2.0f;


	if (horizontal_thrust > thrust_total) {
		horizontal_thrust = thrust_total;

	} else if (horizontal_thrust < -thrust_total) {
		horizontal_thrust = -thrust_total;
	}



	//TODO: maybe we want to add a speed controller later...

	/* Calclulate thrust in east and north direction */
	float thrust_north = cosf(bearing) * horizontal_thrust;
	float thrust_east = sinf(bearing) * horizontal_thrust;

	if (counter % 10 == 0) {
		printf("thrust north: %.4f\n", thrust_north);
		printf("thrust east: %.4f\n", thrust_east);
		fflush(stdout);
	}

	/* Get current attitude */
	if (0 == global_data_trylock(&global_data_attitude->access_conf)) {
		pitch_current = global_data_attitude->pitch;
		global_data_unlock(&global_data_attitude->access_conf);
	}

	/* Get desired pitch & roll */
	float pitch_desired = 0.0f;
	float roll_desired = 0.0f;

	if (thrust_total != 0) {
		float pitch_fraction = -thrust_north / thrust_total;
		float roll_fraction = thrust_east / (cosf(pitch_current) * thrust_total);

		if (roll_fraction < -1) {
			roll_fraction = -1;

		} else if (roll_fraction > 1) {
			roll_fraction = 1;
		}

//		if(counter % 5 == 0)
//		{
//			printf("pitch_fraction: %.4f, roll_fraction: %.4f\n",pitch_fraction, roll_fraction);
//			fflush(stdout);
//		}

		pitch_desired = asinf(pitch_fraction);
		roll_desired = asinf(roll_fraction);
	}

	att_sp.roll = roll_desired;
	att_sp.pitch = pitch_desired;

	counter++;
}