danielduberg/kth_uav

KTH UAV

Assumptions

1. You are running Ubuntu 16.04
2. You are using bash
3. You have installed ros-kinetic-desktop-full (otherwise follow this guide: [http://wiki.ros.org/kinetic/Installation/Ubuntu] and install ros-kinetic-desktop-full)
4. You have created a ROS workspace (see: [http://wiki.ros.org/ROS/Tutorials/InstallingandConfiguringROSEnvironment], but do not run catkin_make).
5. You are using catkin_tools instead of catkin_make
   1. If you have not used catkin_tools before, then read this: [http://catkin-tools.readthedocs.io/en/latest/verbs/catkin_build.html]
   2. You will compile with catkin build instead of catkin_make

Prerequisites

Install Instructions

1. Clone to your ROS workspace: git clone https://github.com/danielduberg/kth_uav.git
2. Run install.sh (might have to chmod +x install.sh first)
3. Close down Gazebo and CTRL+c the terminal
4. source ~/.bashrc or restart the terminal

If you ever move kth_uav read this

1. When you ran install.sh two lines where added to your ~/.bashrc file. The first one starting with # Load the kth_uav bash file, and the second line sources a filed called .bashrc that is located inside kth_uav.
2. If you move the kth_uav, you have to make a change to the second line that was added to your ~/.bashrc file such that it points to the .bashrc inside kth_uav.

Package Explaination

mavros

1. This is what you should use to communicate with the UAV.

2. Here is a list of some of the most interesting topics:

   Filename	Use
   /mavros/distance_sensor/teraranger	Get the distance measure from the TeraRanger.
   /mavros/imu/data	Get IMU data.
   /mavros/local_position/odom	Get pose of UAV and velocity in UAV frame.
   /mavros/local_position/pose	Get pose of the UAV.
   /mavros/local_position/velocity	Get velocity in map frame.
   /mavros/mocap/pose	Send your estimate of the pose of the UAV.
   /mavros/setpoint_raw/local	The prefered (by me) topic to publish positions, velocities, and accelerations to the UAV. From my experience you can only send one of the three at the same time. You can specify which frame the message is in, which makes it possible to give velocity in UAV frame instead of map frame. Only use the non-OFFSET frames, OFFSET is not working with px4. On the real drone send a minimum of 0.3 m/s in x/y (except when you send 0.0 m/s). If the velocity is lower than 0.3 m/s then the UAV can move in any direction!
   /mavros/setpoint_velocity/cmd_vel	Can be used to send velocities. But I prefer the above one instead since it is easier to switch to sending positions if you find that better later on. With the above you can also specify the frame, which you can not here. On the real drone send a minimum of 0.3 m/s in x/y (except when you send 0.0 m/s). If the velocity is lower than 0.3 m/s then the UAV can move in any direction!
   /mavros/setpoint_position/local	Can be used to send positions. Once again I prefer /mavros/setpoint_raw/local over this.

3. Here is a list of some of the most interesting services:

   Filename	Use
   /mavros/cmd/arming	Used to arm/disarm the UAV.
   /mavros/set_mode	Change between different mode. Use offboard to control it with the above topics. For it to stay in offboard you have to publish continously at a certain frequence, else it will go back to the mode it was in before going into offboard. You can use land when you want to land.

simulation

1. The folder models inside simulation contains Gazebo models. If you want, you can add more models in that folder and they will automatically show up in Gazebo.

2. The folder worlds contains worlds...

3. The folder launch contains a number of launch files and configuration files for PX4. We will go through each file in the table:

   Filename	Use
   arm.launch	After you have launched the simulator you can launch this to arm the UAV and put it in offboard mode. You have to publish some sort of setpoint (one of /mavros/setpoint... topics) to the UAV at a certain frequency for it to stay in offboard mode.
   client.launch	Launches only the Gazebo GUI. In the file you have to specify GAZEBO_IP, which is the IP of the client computer, and GAZEBO_MASTER_URI, which is the URI to the Gazebo server that you start using server.launch.
   server.launch	Launches only the Gazebo server (no GUI). In the file you have to specify GAZEBO_IP, which is the IP of the server, and GAZEBO_MASTER_URI, which is the URI to the server (so they are the same except for the port number).
   simulation.launch	Launches the simulator (both server and client). As with the server.launch you can in this file specify the model (UAV) and world to load by changing the arguments sdf and world, respectively.
   px4_config.yaml	Config file for the PX4 where you can specify a bounch of fancy stuff.
   px4_pluginlists.yaml	In this file you can blacklist/whitelist different plugins used by PX4.

px4/Firmware

1. This is the code that is running on the FCU.

mavlink

1. This is the intermidiate layer between the px4 and mavros.

Example Use

/mavros/setpoint_raw/local

1. Example C++ code that is publishing velocities (and yaw rate) in UAV frame to the /mavros/setpoint_raw/local topic:

#include <ros/ros.h>
#include <mavros_msgs/PositionTarget.h>

int main(int argc, char** argv)
{
   ros::init(argc, argv, "controller");
   ros::NodeHandle nh;
   ros::Publisher pub = nh.advertise<mavros_msgs::PositionTarget>("mavros/setpoint_raw/local", 1);
   
   mavros_msgs::PositionTarget pos_tar;
    pos_tar.header.stamp = ros::Time::now();
    pos_tar.header.frame_id = "base_link";
    // We will ignore everything except for YAW_RATE and velocities in X, Y, and Z
    pos_tar.type_mask = mavros_msgs::PositionTarget::IGNORE_PX
            | mavros_msgs::PositionTarget::IGNORE_PY
            | mavros_msgs::PositionTarget::IGNORE_PZ
            | mavros_msgs::PositionTarget::IGNORE_AFX
            | mavros_msgs::PositionTarget::IGNORE_AFY
            | mavros_msgs::PositionTarget::IGNORE_AFZ
            | mavros_msgs::PositionTarget::FORCE
            | mavros_msgs::PositionTarget::IGNORE_YAW;
   // This makes it so our velocities are sent in the UAV frame.
   // If you use FRAME_LOCAL_NED then it will be in map frame
   pos_tar.coordinate_frame = mavros_msgs::PositionTarget::FRAME_BODY_NED;
   
   // Set the velocities we want (it is in m/s)
   // On the real drone send a minimum of 0.3 m/s in x/y (except when you send 0.0 m/s).
   // If the velocity is lower than 0.3 m/s then the UAV can move in any direction!
   pos_tar.velocity.x = 0.3;
   pos_tar.velocity.y = 0.0;
   pos_tar.velocity.z = 0.1;
   // Set the yaw rate (it is in rad/s)
   pos_tar.yaw_rate = 0.1;
   
   ros::Rate r(20); // 20 hz
   while (ros::ok())
   {
     pub.publish(pos_tar);
     r.sleep();
   }
}