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

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 * modification, are permitted provided that the following conditions
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/**
 * @file main.cpp
 *
 * Example implementation of a rover steering controller.
 *
 * @author Lorenz Meier <lorenz@px4.io>
 */

#include <px4_tasks.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <math.h>
#include <poll.h>
#include <time.h>
#include <drivers/drv_hrt.h>
#include <uORB/uORB.h>
#include <uORB/topics/vehicle_global_position.h>
#include <uORB/topics/position_setpoint_triplet.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/vehicle_status.h>
#include <uORB/topics/vehicle_attitude_setpoint.h>
#include <uORB/topics/manual_control_setpoint.h>
#include <uORB/topics/actuator_controls.h>
#include <uORB/topics/actuator_controls_0.h>
#include <uORB/topics/actuator_controls_1.h>
#include <uORB/topics/actuator_controls_2.h>
#include <uORB/topics/actuator_controls_3.h>
#include <uORB/topics/vehicle_global_position.h>
#include <uORB/topics/parameter_update.h>
#include <systemlib/param/param.h>
#include <systemlib/pid/pid.h>
#include <geo/geo.h>
#include <systemlib/perf_counter.h>
#include <systemlib/systemlib.h>
#include <systemlib/err.h>

/* process-specific header files */
#include "params.h"

/* Prototypes */

/**
 * 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 rover_steering_control_main(int argc, char *argv[]);

struct params {
	float yaw_p;
};

struct param_handles {
	param_t yaw_p;
};

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

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

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

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

/**
 * 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
 */
void control_attitude(const struct vehicle_attitude_setpoint_s *att_sp, const struct vehicle_attitude_s *att,
		      struct actuator_controls_s *actuators);

/* 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 pp;
static struct param_handles ph;

int parameters_init(struct param_handles *h)
{
	/* PID parameters */
	h->yaw_p 	=	param_find("RV_YAW_P");

	return OK;
}

int parameters_update(const struct param_handles *h, struct params *p)
{
	param_get(h->yaw_p, &(p->yaw_p));

	return OK;
}

void control_attitude(const struct vehicle_attitude_setpoint_s *att_sp, const struct vehicle_attitude_s *att,
		      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):
	 *
	 *    ...
	 */

	/* set r/p zero */
	actuators->control[0] = 0.0f;
	actuators->control[1] = 0.0f;

	/*
	 * Calculate roll error and apply P gain
	 */
	float yaw_err = att->yaw - att_sp->yaw_body;
	actuators->control[2] = yaw_err * pp.yaw_p;

	/* copy throttle */
	actuators->control[3] = att_sp->thrust;

	actuators->timestamp = hrt_absolute_time();
}

/* Main Thread */
int rover_steering_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;
		}
	}

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


	/*
	 * 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_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 < (sizeof(actuators.control) / sizeof(actuators.control[0])); i++) {
		actuators.control[i] = 0.0f;
	}

	struct vehicle_attitude_setpoint_s _att_sp = {};

	/*
	 * 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);

	/* 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 att_sp_sub = orb_subscribe(ORB_ID(vehicle_attitude_setpoint));

	int param_sub = orb_subscribe(ORB_ID(parameter_update));

	/* Setup of loop */

	struct pollfd fds[2];

	fds[0].fd = param_sub;

	fds[0].events = POLLIN;

	fds[1].fd = att_sub;

	fds[1].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, 2, 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 {

			/* only update parameters if they changed */
			if (fds[0].revents & POLLIN) {
				/* read from param to clear updated flag (uORB API requirement) */
				struct parameter_update_s update;
				orb_copy(ORB_ID(parameter_update), param_sub, &update);

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

			/* only run controller if attitude changed */
			if (fds[1].revents & POLLIN) {


				/* Check if there is a new position measurement or position setpoint */
				bool pos_updated;
				orb_check(global_pos_sub, &pos_updated);
				bool att_sp_updated;
				orb_check(att_sp_sub, &att_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 (att_sp_updated) {
					orb_copy(ORB_ID(vehicle_attitude_setpoint), att_sp_sub, &_att_sp);
				}

				/* control attitude / heading */
				control_attitude(&_att_sp, &att, &actuators);

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

				// XXX copy from manual depending on flight / usage mode to override

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

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

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

	warnx("exiting, stopping all motors.");
	thread_running = false;

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

	actuators.timestamp = hrt_absolute_time();

	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: rover_steering_control {start|stop|status}\n\n");
	exit(1);
}

/**
 * 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 rover_steering_control_main(int argc, char *argv[])
{
	if (argc < 2) {
		usage("missing command");
	}

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

		if (thread_running) {
			warnx("running");
			/* this is not an error */
			exit(0);
		}

		thread_should_exit = false;
		deamon_task = px4_task_spawn_cmd("rover_steering_control",
					     SCHED_DEFAULT,
					     SCHED_PRIORITY_MAX - 20,
					     2048,
					     rover_steering_control_thread_main,
					     (argv) ? (char * const *)&argv[2] : (char * const *)NULL);
		thread_running = true;
		exit(0);
	}

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

	if (!strcmp(argv[1], "status")) {
		if (thread_running) {
			warnx("running");

		} else {
			warnx("not started");
		}

		exit(0);
	}

	usage("unrecognized command");
	exit(1);
}