OffboardControlMode makes motor throttle zero after change target position

PX4 Autopilot
1

Hello, everyone.

I have encountered an issue during OffboardControlMode. The key point is as follows:

  1. The drone takes off without any apparent anomalies.
  2. Subsequently, shortly after reaching its target altitude, the throttle of motors 1 and 3 abruptly drops to zero, causing the drone to fall.

I have attached a screenshot from PlotJuggler, summarizing this incident.

25-01-23 1843 Crash - 1
25-01-23 1843 Crash - 12672Ă—1527 534 KB

As you can see, _lactuator_motors/control.00 and _lactuator_motors/control.02 suddenly drop to zero when the trajectory setpoint is entered into the FCU.

This behavior has never exhibited during position control mode with RC. Therefore, I assume there is no problem with sensors or parameter settings but rather with OffboardControlMode.

The attached screenshot is a PX4 log message. The drone appears to have fallen around Timestamp 95.00. Subsequently, a Preflight Error is detected at 95.86.

25-01-23 1843 Crash - 2
25-01-23 1843 Crash - 2752Ă—1167 121 KB

The following function, referred to as the “trajectory setpoint” function, is utilized within the experiment, where hovering position is {0, 0, -1.5}, initial position is {-4, -4, -1.5}.

Upon publishing the message “RCLCPP_INFO(this->get_logger(), “’%s’ reached to hovering position!”, namespace_.c_str());”, the drone falls down.

void OffboardControl::publish_trajectory_setpoint()
{
	std::string namespace_ = this->get_namespace();

	if (!reached_hovering_position_)
	{
		geometry_msgs::msg::PoseStamped hovering_position_;
		hovering_position_.header.frame_id = namespace_;
		hovering_position_.pose.position.x = 0;
		hovering_position_.pose.position.y = 0;
		hovering_position_.pose.position.z = -hover_height_ + ref_alt_; // END

		TrajectorySetpoint msg{};
		msg.position = {
			static_cast<float>(hovering_position_.pose.position.x), 
			static_cast<float>(hovering_position_.pose.position.y), 
			static_cast<float>(hovering_position_.pose.position.z) // END
		};
		// msg.yaw = M_PI / 2; // [-PI:PI]
		msg.timestamp = this->get_clock()->now().nanoseconds() / 1000;
		trajectory_setpoint_publisher_->publish(msg);


		if (distance(local_position_, hovering_position_) < 0.1) 
		{
			RCLCPP_INFO(this->get_logger(), "'%s' reached to hovering position!", namespace_.c_str());
			reached_hovering_position_ = true;
		}
	}
	else
	{	
		// RCLCPP_INFO(this->get_logger(), "'%s' recieve initial position, '%s'", namespace_.c_str(), recieve_initial_position_ ?"true":"false");
		if (recieve_initial_position_)
		{
			TrajectorySetpoint msg{};
			msg.position = {
				static_cast<float>(initial_position_.pose.position.x), 
				static_cast<float>(initial_position_.pose.position.y), 
				static_cast<float>(initial_position_.pose.position.z) // END
			};
			msg.yaw = 0;
			msg.timestamp = this->get_clock()->now().nanoseconds() / 1000;
			trajectory_setpoint_publisher_->publish(msg);

			if (distance(local_position_, initial_position_) < 0.1)
			{	
				reached_initial_position_ = true;
				custom_files::msg::BoolStamped msg;
				msg.header.frame_id = namespace_;
				msg.data = reached_initial_position_;
				reached_initial_position_publisher_->publish(msg);
				
				if (count < 1)
				{
					RCLCPP_INFO(this->get_logger(), "'%s' reached to initial position!", namespace_.c_str());
					count++;
				}

			}
		}

	}
}

I thick it is similar to case 1 of similar issue.

Lastly, the video captures this incident. Please pay attention to the around 18-second that illustrates this “failure.”

Motor throttle 1 & 3 suddenly dropped to zero, completely losing its control.

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