SITL with gazebo doesn't receive the actuator control published by example code

Hi all,

I’m newbie in px4 and trying to make example code.

What I want to is to give reference signal (e.g. : 3211 roll angle signal) to the quadrotor.

As the first step of that, I make some example code as below.

The code subscribes vehicle_attitude.h, and publish actuator_controls.h.

The problem is that when I type px4_tutorial in px4shell, terminal prints attitude but the quadrotor doesn’t react to actuator_controls published by px4_tutorial.

What am I missed?

Also, there are any difference between actuator_controls_0 and actuator_controls_1 which are both name of the topic “actuator_controls”.

thanks and sorry for my poor english.

#include <px4_platform_common/log.h>
#include <uORB/topics/sensor_combined.h>
#include <px4_platform_common/posix.h>
#include <uORB/topics/vehicle_attitude.h>
#include <string.h>
#include <uORB/topics/actuator_controls.h>

__EXPORT int px4_tutorial_main(int argc, char *argv[]);

int px4_tutorial_main(int argc, char *argv[]) {
	PX4_INFO("Hello Sky!");

	struct vehicle_attitude_s att;
	memset(&att, 0, sizeof(att));
	orb_advert_t att_pub = orb_advertise(ORB_ID(vehicle_attitude), &att);

	struct actuator_controls_s ctr;
	memset(&ctr, 0, sizeof(ctr));
	orb_advert_t ctr_pub = orb_advertise(ORB_ID(actuator_controls_0), &ctr);

	int sensor_sub_fd = orb_subscribe(ORB_ID(sensor_combined));

	orb_set_interval(sensor_sub_fd, 200);

	px4_pollfd_struct_t fds[] = {
		{ .fd = sensor_sub_fd,  .events = POLLIN},

	int error_counter = 0;

	for (int i = 0; i < 5; i++) {
		int poll_ret = px4_poll(fds, 1, 1000);
		if (poll_ret == 0) {
			PX4_ERR("Got no data within a second");
		} else if (poll_ret <0 ) {
			if (error_counter < 10 || error_counter % 50 == 0) {
				PX4_ERR("ERROR return value from poll(): %d", poll_ret);

		} else {
			if (fds[0].revents & POLLIN) {
				struct sensor_combined_s raw;
				orb_copy(ORB_ID(sensor_combined), sensor_sub_fd, &raw);
					att.q[0] = 1;
					att.q[1] = 2;
					att.q[2] = 3;
					orb_publish(ORB_ID(vehicle_attitude), att_pub, &att);

	ctr.control[0] = 0;
	ctr.control[1] = 0;
	ctr.control[2] = 0;				
	ctr.control[3] = 1.0f;

	orb_publish(ORB_ID(actuator_controls_0), ctr_pub, &ctr);

	return 0;

You need to do at least two things to get this to work in SITL:

  1. Disable lockstep, otherwise it might get out of sync and everything will stop, see:

  2. Disable other modules that are started and are doing controls. E.g. for fixedwing it should be these:
    Otherwise you will fight the existing controllers.

Hey skfmsgka

I am trying to do exactly what you were trying, to write code to control pitch or roll of a quad and see it in jmavsim. I followed the tutorial here and now I’m trying to write an application that will give commands to change the attitude of the quad. I tried to use the message vehicle_attitude_control to send attitude commands but that didn’t work. Here’s the code-

struct vehicle_attitude_setpoint_s att;
	memset(&att, 0, sizeof(att));
	orb_advert_t att_pub = orb_advertise(ORB_ID(vehicle_attitude_setpoint), &att);

    att.q_d[0] = 1.5;
	att.q_d[1] = 2.6;
	att.q_d[3] = 2.7;
    att.q_d[4] = 1.7;

	orb_publish(ORB_ID(vehicle_attitude_setpoint), att_pub, &att);

How did you solve your problem?

Did you see my comment about disabling lockstep?

Hey @JulianOes .
Are you talking about this?- [Err] [gazebo_mavlink_interface.cpp:1018] poll timeout when mc_att_control stop · Issue #11503 · PX4/PX4-Autopilot · GitHub
I did disable lockstep in sitl.cmake in boards/px4/sitl. However I still can’t seem to get it to work.

Right, other things might have changed in the meantime. To debug it I suggest to track the data through the system. Check what gets published where and how it flows (or doesn’t flow) through.

That’s what I’m doing right now. It’s a rigorous process and is taking me time.

Right, don’t forget to use the commands uorb top and listener <topicname>

@A7sus4 have you find a solution?

I’d suggest that you look through the commander.cpp and the other related files. You’ll find the entire control flow in that code, and once you understand it, you can give your own commands by disabling or changing the default flow of control.

For example you can change what commander takeoff does and can make the quad do something entirely different using commander takeoff. I’m talking about modifying commander takeoff because it’s much simpler to modify it than create a new command right away.

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Can you show me your example code? In this way you were able to move the drone?
Because I have already seen the commander.cpp but i don’t understend in which topic I have to publish to control the movment of the drone