PX4-Autopilot/src/examples/fixedwing_control/main.cpp

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 *
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 * modification, are permitted provided that the following conditions
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/**
 * @file main.c
 *
 * Example implementation of a fixed wing attitude controller. This file is a complete
 * fixed wing controller for manual attitude control or auto waypoint control.
 * There is no need to touch any other system components to extend / modify the
 * complete control architecture.
 *
 * @author Lorenz Meier <lm@inf.ethz.ch>
 */

#include "params.h"

#include <poll.h>

#include <drivers/drv_hrt.h>
#include <lib/ecl/geo/geo.h>
#include <matrix/math.hpp>
#include <px4_config.h>
#include <px4_tasks.h>
#include <systemlib/err.h>
#include <parameters/param.h>
#include <perf/perf_counter.h>
#include <uORB/Subscription.hpp>
#include <uORB/topics/actuator_controls.h>
#include <uORB/topics/manual_control_setpoint.h>
#include <uORB/topics/parameter_update.h>
#include <uORB/topics/position_setpoint_triplet.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/vehicle_attitude_setpoint.h>
#include <uORB/topics/vehicle_global_position.h>
#include <uORB/topics/vehicle_global_position.h>
#include <uORB/topics/vehicle_rates_setpoint.h>
#include <uORB/topics/vehicle_status.h>
#include <uORB/uORB.h>

/* Prototypes */

/**
 * Initialize all parameter handles and values
 *
 */
extern "C" int parameters_init(struct param_handles *h);

/**
 * Update all parameters
 *
 */
extern "C" int parameters_update(const struct param_handles *h, struct params *p);

/**
 * Daemon management function.
 *
 * This function allows to start / stop the background task (daemon).
 * The purpose of it is to be able to start the controller on the
 * command line, query its status and stop it, without giving up
 * the command line to one particular process or the need for bg/fg
 * ^Z support by the shell.
 */
extern "C" __EXPORT int ex_fixedwing_control_main(int argc, char *argv[]);

/**
 * Mainloop of daemon.
 */
int fixedwing_control_thread_main(int argc, char *argv[]);

/**
 * Print the correct usage.
 */
static void usage(const char *reason);

int parameters_init(struct param_handles *h);

/**
 * Update all parameters
 *
 */
int parameters_update(const struct param_handles *h, struct params *p);

/**
 * Control roll and pitch angle.
 *
 * This very simple roll and pitch controller takes the current roll angle
 * of the system and compares it to a reference. Pitch is controlled to zero and yaw remains
 * uncontrolled (tutorial code, not intended for flight).
 *
 * @param att_sp The current attitude setpoint - the values the system would like to reach.
 * @param att The current attitude. The controller should make the attitude match the setpoint
 * @param rates_sp The angular rate setpoint. This is the output of the controller.
 */
void control_attitude(const struct vehicle_attitude_setpoint_s *att_sp, const struct vehicle_attitude_s *att,
		      struct vehicle_rates_setpoint_s *rates_sp,
		      struct actuator_controls_s *actuators);

/**
 * Control heading.
 *
 * This very simple heading to roll angle controller outputs the desired roll angle based on
 * the current position of the system, the desired position (the setpoint) and the current
 * heading.
 *
 * @param pos The current position of the system
 * @param sp The current position setpoint
 * @param att The current attitude
 * @param att_sp The attitude setpoint. This is the output of the controller
 */
void control_heading(const struct vehicle_global_position_s *pos, const struct position_setpoint_s *sp,
		     const struct vehicle_attitude_s *att, struct vehicle_attitude_setpoint_s *att_sp);

/* Variables */
static bool thread_should_exit = false;		/**< Daemon exit flag */
static bool thread_running = false;		/**< Daemon status flag */
static int deamon_task;				/**< Handle of deamon task / thread */
static struct params p;
static struct param_handles ph;

void control_attitude(const struct vehicle_attitude_setpoint_s *att_sp, const struct vehicle_attitude_s *att,
		      struct vehicle_rates_setpoint_s *rates_sp,
		      struct actuator_controls_s *actuators)
{

	/*
	 * The PX4 architecture provides a mixer outside of the controller.
	 * The mixer is fed with a default vector of actuator controls, representing
	 * moments applied to the vehicle frame. This vector
	 * is structured as:
	 *
	 * Control Group 0 (attitude):
	 *
	 *    0  -  roll   (-1..+1)
	 *    1  -  pitch  (-1..+1)
	 *    2  -  yaw    (-1..+1)
	 *    3  -  thrust ( 0..+1)
	 *    4  -  flaps  (-1..+1)
	 *    ...
	 *
	 * Control Group 1 (payloads / special):
	 *
	 *    ...
	 */

	/*
	 * Calculate roll error and apply P gain
	 */

	matrix::Eulerf att_euler = matrix::Quatf(att->q);
	matrix::Eulerf att_sp_euler = matrix::Quatf(att_sp->q_d);

	float roll_err = att_euler.phi() - att_sp_euler.phi();
	actuators->control[0] = roll_err * p.roll_p;

	/*
	 * Calculate pitch error and apply P gain
	 */
	float pitch_err = att_euler.theta() - att_sp_euler.theta();
	actuators->control[1] = pitch_err * p.pitch_p;
}

void control_heading(const struct vehicle_global_position_s *pos, const struct position_setpoint_s *sp,
		     const struct vehicle_attitude_s *att, struct vehicle_attitude_setpoint_s *att_sp)
{

	/*
	 * Calculate heading error of current position to desired position
	 */

	float bearing = get_bearing_to_next_waypoint(pos->lat, pos->lon, sp->lat, sp->lon);

	matrix::Eulerf att_euler = matrix::Quatf(att->q);

	/* calculate heading error */
	float yaw_err = att_euler.psi() - bearing;
	/* apply control gain */
	float roll_body = yaw_err * p.hdng_p;

	/* limit output, this commonly is a tuning parameter, too */
	if (roll_body < -0.6f) {
		roll_body = -0.6f;

	} else if (att_sp->roll_body > 0.6f) {
		roll_body = 0.6f;
	}

	matrix::Eulerf att_spe(roll_body, 0, bearing);

	matrix::Quatf qd(att_spe);

	att_sp->q_d[0] = qd(0);
	att_sp->q_d[1] = qd(1);
	att_sp->q_d[2] = qd(2);
	att_sp->q_d[3] = qd(3);
}

int parameters_init(struct param_handles *handles)
{
	/* PID parameters */
	handles->hdng_p 	=	param_find("EXFW_HDNG_P");
	handles->roll_p 	=	param_find("EXFW_ROLL_P");
	handles->pitch_p 	=	param_find("EXFW_PITCH_P");

	return 0;
}

int parameters_update(const struct param_handles *handles, struct params *parameters)
{
	param_get(handles->hdng_p, &(parameters->hdng_p));
	param_get(handles->roll_p, &(parameters->roll_p));
	param_get(handles->pitch_p, &(parameters->pitch_p));

	return 0;
}


/* Main Thread */
int fixedwing_control_thread_main(int argc, char *argv[])
{
	/* read arguments */
	bool verbose = false;

	for (int i = 1; i < argc; i++) {
		if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
			verbose = true;
		}
	}

	/* welcome user (warnx prints a line, including an appended\n, with variable arguments */
	warnx("[example fixedwing control] started");

	/* initialize parameters, first the handles, then the values */
	parameters_init(&ph);
	parameters_update(&ph, &p);


	/*
	 * PX4 uses a publish/subscribe design pattern to enable
	 * multi-threaded communication.
	 *
	 * The most elegant aspect of this is that controllers and
	 * other processes can either 'react' to new data, or run
	 * at their own pace.
	 *
	 * PX4 developer guide:
	 * https://pixhawk.ethz.ch/px4/dev/shared_object_communication
	 *
	 * Wikipedia description:
	 * http://en.wikipedia.org/wiki/Publish–subscribe_pattern
	 *
	 */




	/*
	 * Declare and safely initialize all structs to zero.
	 *
	 * These structs contain the system state and things
	 * like attitude, position, the current waypoint, etc.
	 */
	struct vehicle_attitude_s att;
	memset(&att, 0, sizeof(att));
	struct vehicle_attitude_setpoint_s att_sp;
	memset(&att_sp, 0, sizeof(att_sp));
	struct vehicle_rates_setpoint_s rates_sp;
	memset(&rates_sp, 0, sizeof(rates_sp));
	struct vehicle_global_position_s global_pos;
	memset(&global_pos, 0, sizeof(global_pos));
	struct manual_control_setpoint_s manual_sp;
	memset(&manual_sp, 0, sizeof(manual_sp));
	struct vehicle_status_s vstatus;
	memset(&vstatus, 0, sizeof(vstatus));
	struct position_setpoint_s global_sp;
	memset(&global_sp, 0, sizeof(global_sp));

	/* output structs - this is what is sent to the mixer */
	struct actuator_controls_s actuators;
	memset(&actuators, 0, sizeof(actuators));


	/* publish actuator controls with zero values */
	for (unsigned i = 0; i < actuator_controls_s::NUM_ACTUATOR_CONTROLS; i++) {
		actuators.control[i] = 0.0f;
	}

	/*
	 * Advertise that this controller will publish actuator
	 * control values and the rate setpoint
	 */
	orb_advert_t actuator_pub = orb_advertise(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, &actuators);
	orb_advert_t rates_pub = orb_advertise(ORB_ID(vehicle_rates_setpoint), &rates_sp);

	/* subscribe to topics. */
	int att_sub = orb_subscribe(ORB_ID(vehicle_attitude));
	int global_pos_sub = orb_subscribe(ORB_ID(vehicle_global_position));
	int manual_sp_sub = orb_subscribe(ORB_ID(manual_control_setpoint));
	int vstatus_sub = orb_subscribe(ORB_ID(vehicle_status));
	int global_sp_sub = orb_subscribe(ORB_ID(position_setpoint_triplet));

	uORB::Subscription parameter_update_sub{ORB_ID(parameter_update)};

	/* Setup of loop */

	struct pollfd fds[1] {};
	fds[0].fd = att_sub;
	fds[0].events = POLLIN;

	while (!thread_should_exit) {

		/*
		 * Wait for a sensor or param update, check for exit condition every 500 ms.
		 * This means that the execution will block here without consuming any resources,
		 * but will continue to execute the very moment a new attitude measurement or
		 * a param update is published. So no latency in contrast to the polling
		 * design pattern (do not confuse the poll() system call with polling).
		 *
		 * This design pattern makes the controller also agnostic of the attitude
		 * update speed - it runs as fast as the attitude updates with minimal latency.
		 */
		int ret = poll(fds, 1, 500);

		if (ret < 0) {
			/*
			 * Poll error, this will not really happen in practice,
			 * but its good design practice to make output an error message.
			 */
			warnx("poll error");

		} else if (ret == 0) {
			/* no return value = nothing changed for 500 ms, ignore */
		} else {

			// check for parameter updates
			if (parameter_update_sub.updated()) {
				// clear update
				parameter_update_s pupdate;
				parameter_update_sub.copy(&pupdate);

				// if a param update occured, re-read our parameters
				parameters_update(&ph, &p);
			}

			/* only run controller if attitude changed */
			if (fds[0].revents & POLLIN) {


				/* Check if there is a new position measurement or position setpoint */
				bool pos_updated;
				orb_check(global_pos_sub, &pos_updated);
				bool global_sp_updated;
				orb_check(global_sp_sub, &global_sp_updated);
				bool manual_sp_updated;
				orb_check(manual_sp_sub, &manual_sp_updated);

				/* get a local copy of attitude */
				orb_copy(ORB_ID(vehicle_attitude), att_sub, &att);

				if (global_sp_updated) {
					struct position_setpoint_triplet_s triplet;
					orb_copy(ORB_ID(position_setpoint_triplet), global_sp_sub, &triplet);
					memcpy(&global_sp, &triplet.current, sizeof(global_sp));
				}

				if (manual_sp_updated)
					/* get the RC (or otherwise user based) input */
				{
					orb_copy(ORB_ID(manual_control_setpoint), manual_sp_sub, &manual_sp);
				}

				/* check if the throttle was ever more than 50% - go later only to failsafe if yes */
				if (PX4_ISFINITE(manual_sp.z) &&
				    (manual_sp.z >= 0.6f) &&
				    (manual_sp.z <= 1.0f)) {
				}

				/* get the system status and the flight mode we're in */
				orb_copy(ORB_ID(vehicle_status), vstatus_sub, &vstatus);

				/* publish rates */
				orb_publish(ORB_ID(vehicle_rates_setpoint), rates_pub, &rates_sp);

				/* sanity check and publish actuator outputs */
				if (PX4_ISFINITE(actuators.control[0]) &&
				    PX4_ISFINITE(actuators.control[1]) &&
				    PX4_ISFINITE(actuators.control[2]) &&
				    PX4_ISFINITE(actuators.control[3])) {
					orb_publish(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, actuator_pub, &actuators);

					if (verbose) {
						warnx("published");
					}
				}
			}
		}
	}

	printf("[ex_fixedwing_control] exiting, stopping all motors.\n");
	thread_running = false;

	/* kill all outputs */
	for (unsigned i = 0; i < actuator_controls_s::NUM_ACTUATOR_CONTROLS; i++) {
		actuators.control[i] = 0.0f;
	}

	orb_publish(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, actuator_pub, &actuators);

	fflush(stdout);

	return 0;
}

/* Startup Functions */

static void
usage(const char *reason)
{
	if (reason) {
		fprintf(stderr, "%s\n", reason);
	}

	fprintf(stderr, "usage: ex_fixedwing_control {start|stop|status}\n\n");
}

/**
 * The daemon app only briefly exists to start
 * the background job. The stack size assigned in the
 * Makefile does only apply to this management task.
 *
 * The actual stack size should be set in the call
 * to px4_task_spawn_cmd().
 */
int ex_fixedwing_control_main(int argc, char *argv[])
{
	if (argc < 2) {
		usage("missing command");
		return 1;
	}

	if (!strcmp(argv[1], "start")) {

		if (thread_running) {
			printf("ex_fixedwing_control already running\n");
			/* this is not an error */
			return 0;
		}

		thread_should_exit = false;
		deamon_task = px4_task_spawn_cmd("ex_fixedwing_control",
						 SCHED_DEFAULT,
						 SCHED_PRIORITY_MAX - 20,
						 2048,
						 fixedwing_control_thread_main,
						 (argv) ? (char *const *)&argv[2] : (char *const *)nullptr);
		thread_running = true;
		return 0;
	}

	if (!strcmp(argv[1], "stop")) {
		thread_should_exit = true;
		return 0;
	}

	if (!strcmp(argv[1], "status")) {
		if (thread_running) {
			printf("\tex_fixedwing_control is running\n");

		} else {
			printf("\tex_fixedwing_control not started\n");
		}

		return 0;
	}

	usage("unrecognized command");
	return 0;
}