How do I change ROS2 code in multi-vehicle simulation?

I want move 2 iris respectively.
Then I did below.

DONT_RUN=1 make px4_sitl_rtps gazebo
./Tools/gazebo_sitl_multiple_run.sh -t px4_sitl_rtps -m iris -l rtps -n 2
micrortps_agent -t UDP -r 2020 -s 2019 -n v1 &
micrortps_agent -t UDP -r 2022 -s 2021 -n v2 &

Then, I want to run example “offboard_control”
when I controll only v1, How do I change offboard_control.cpp?

offboard_control.cpp

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/**
 * @brief Offboard control example
 * @file offboard_control.cpp
 * @addtogroup examples
 * @author Mickey Cowden <info@cowden.tech>
 * @author Nuno Marques <nuno.marques@dronesolutions.io>

 * The TrajectorySetpoint message and the OFFBOARD mode in general are under an ongoing update.
 * Please refer to PR: https://github.com/PX4/PX4-Autopilot/pull/16739 for more info. 
 * As per PR: https://github.com/PX4/PX4-Autopilot/pull/17094, the format
 * of the TrajectorySetpoint message shall change.
 */

#include <px4_msgs/msg/offboard_control_mode.hpp>
#include <px4_msgs/msg/trajectory_setpoint.hpp>
#include <px4_msgs/msg/timesync.hpp>
#include <px4_msgs/msg/vehicle_command.hpp>
#include <px4_msgs/msg/vehicle_control_mode.hpp>
#include <rclcpp/rclcpp.hpp>
#include <stdint.h>

#include <chrono>
#include <iostream>

using namespace std::chrono;
using namespace std::chrono_literals;
using namespace px4_msgs::msg;

class OffboardControl : public rclcpp::Node {
public:
	OffboardControl() : Node("offboard_control") {
#ifdef ROS_DEFAULT_API
		offboard_control_mode_publisher_ =
			this->create_publisher<OffboardControlMode>("v1/OffboardControlMode_PubSubTopic", 10);
		trajectory_setpoint_publisher_ =
			this->create_publisher<TrajectorySetpoint>("TrajectorySetpoint_PubSubTopic", 10);
		vehicle_command_publisher_ =
			this->create_publisher<VehicleCommand>("VehicleCommand_PubSubTopic", 10);
#else
		offboard_control_mode_publisher_ =
			this->create_publisher<OffboardControlMode>("v1/OffboardControlMode_PubSubTopic");
		trajectory_setpoint_publisher_ =
		 	this->create_publisher<TrajectorySetpoint>("TrajectorySetpoint_PubSubTopic");
		vehicle_command_publisher_ =
			this->create_publisher<VehicleCommand>("VehicleCommand_PubSubTopic");
#endif

		// get common timestamp
		timesync_sub_ =
			this->create_subscription<px4_msgs::msg::Timesync>("Timesync_PubSubTopic", 10,
				[this](const px4_msgs::msg::Timesync::UniquePtr msg) {
					timestamp_.store(msg->timestamp);
				});

		offboard_setpoint_counter_ = 0;

		auto timer_callback = [this]() -> void {

			if (offboard_setpoint_counter_ == 10) {
				// Change to Offboard mode after 10 setpoints
				this->publish_vehicle_command(VehicleCommand::VEHICLE_CMD_DO_SET_MODE, 1, 6);

				// Arm the vehicle
				this->arm();
			}

            		// offboard_control_mode needs to be paired with trajectory_setpoint
			publish_offboard_control_mode();
			publish_trajectory_setpoint();

           		 // stop the counter after reaching 11
			if (offboard_setpoint_counter_ < 11) {
				offboard_setpoint_counter_++;
			}
		};
		timer_ = this->create_wall_timer(100ms, timer_callback);
	}

	void arm() const;
	void disarm() const;

private:
	rclcpp::TimerBase::SharedPtr timer_;

	rclcpp::Publisher<OffboardControlMode>::SharedPtr offboard_control_mode_publisher_;
	rclcpp::Publisher<TrajectorySetpoint>::SharedPtr trajectory_setpoint_publisher_;
	rclcpp::Publisher<VehicleCommand>::SharedPtr vehicle_command_publisher_;
	rclcpp::Subscription<px4_msgs::msg::Timesync>::SharedPtr timesync_sub_;

	std::atomic<uint64_t> timestamp_;   //!< common synced timestamped

	uint64_t offboard_setpoint_counter_;   //!< counter for the number of setpoints sent

	void publish_offboard_control_mode() const;
	void publish_trajectory_setpoint() const;
	void publish_vehicle_command(uint16_t command, float param1 = 0.0,
				     float param2 = 0.0) const;
};

/**
 * @brief Send a command to Arm the vehicle
 */
void OffboardControl::arm() const {
	publish_vehicle_command(VehicleCommand::VEHICLE_CMD_COMPONENT_ARM_DISARM, 1.0);

	RCLCPP_INFO(this->get_logger(), "Arm command send");
}

/**
 * @brief Send a command to Disarm the vehicle
 */
void OffboardControl::disarm() const {
	publish_vehicle_command(VehicleCommand::VEHICLE_CMD_COMPONENT_ARM_DISARM, 0.0);

	RCLCPP_INFO(this->get_logger(), "Disarm command send");
}

/**
 * @brief Publish the offboard control mode.
 *        For this example, only position and altitude controls are active.
 */
void OffboardControl::publish_offboard_control_mode() const {
	OffboardControlMode msg{};
	msg.timestamp = timestamp_.load();
	msg.position = true;
	msg.velocity = false;
	msg.acceleration = false;
	msg.attitude = false;
	msg.body_rate = false;

	offboard_control_mode_publisher_->publish(msg);
}


/**
 * @brief Publish a trajectory setpoint
 *        For this example, it sends a trajectory setpoint to make the
 *        vehicle hover at 5 meters with a yaw angle of 180 degrees.
 */
void OffboardControl::publish_trajectory_setpoint() const {
	TrajectorySetpoint msg{};
	msg.timestamp = timestamp_.load();
	msg.x = 0.0;
	msg.y = 0.0;
	msg.z = -5.0;
	msg.yaw = -3.14; // [-PI:PI]

	trajectory_setpoint_publisher_->publish(msg);
}

/**
 * @brief Publish vehicle commands
 * @param command   Command code (matches VehicleCommand and MAVLink MAV_CMD codes)
 * @param param1    Command parameter 1
 * @param param2    Command parameter 2
 */
void OffboardControl::publish_vehicle_command(uint16_t command, float param1,
					      float param2) const {
	VehicleCommand msg{};
	msg.timestamp = timestamp_.load();
	msg.param1 = param1;
	msg.param2 = param2;
	msg.command = command;
	msg.target_system = 1;
	msg.target_component = 1;
	msg.source_system = 1;
	msg.source_component = 1;
	msg.from_external = true;

	vehicle_command_publisher_->publish(msg);
}

int main(int argc, char* argv[]) {
	std::cout << "Starting offboard control node..." << std::endl;
	setvbuf(stdout, NULL, _IONBF, BUFSIZ);
	rclcpp::init(argc, argv);
	rclcpp::spin(std::make_shared<OffboardControl>());

	rclcpp::shutdown();
	return 0;
}

Just adding /v1/ as a prefix fo all the topics should be enough.

1 Like

I have tried to add /v1 , but nothing happened before.

I’ll try again one more time

Thank you.

I am trying to do the same thing but I think using namespaces may be not sufficient. In my case, the first vehicle can takeoff and do what it supposed to do but the second one does not takeoff. Even if the mode changes to takeoff mode and then off-board mode. I can see these changes for the second vehicle from QGroundControl. Is there anything we need to change about the arguments of VehicleCommand?

Did you see this? Offboard mode in SITL
It could be that the second drone expects an RC signal but none is received.