TF coordinate transformation of common components of ros-9 ROS

One 、 Concept

Coordinate transformation is simply normalization , That is, the measured position information between other objects and sensors on the robot is replaced by the information between the object and the origin of the robot .

According to what we learned in high school , As long as the relative relationship between different coordinate systems is clear , Any coordinate point can be converted between different coordinate systems , But this computing implementation is commonly used , And the algorithm is a little complicated , So in ROS The related modules are directly encapsulated in : Coordinate transformation (TF).TF Coordinate transformation is used in ROS Realize the transformation of points or vectors between different coordinate systems .

TF Coordinate transformation through broadcast TF Transform and monitor TF Transformation to achieve

Two 、 Check whether the current coordinate systems in the system are connected

rosrun tf view_frames

Running the above specification will generate .gv and .pdf2 File , It is used to display the connectivity of various coordinate systems in the current system

For example, running ros Medium turtle_tf_demo, Three coordinate systems are defined in the of this routine : Coordinate origin ,turtle1,turtle2.turtle2 Will listen turtle1d be relative to world The position of , And then change your position . Follow in real time turtle1.

Before that, install the package ：

sudo apt-get install ros-melodic-turtle-tf

The running routine code is as follows ：

roslaunch turtle_tf turtle_tf_demo.launch

And then run ：rosrun tf view_frames You can view the relationship between coordinate systems in the current system .

  3、 ... and 、 Real-time query tf The positional relationship between any two coordinate systems of tree species ：

rosrun tf tf_echo  Root coordinate system   Target coordinate system 

  for example ： I'm still running turtle_tf_demo.launch routine , Next run

rosrun tf tf_echo turtle1 turtle 2

When I keyboard control the first turtle to move , The coordinate position relationship between the second turtle and the first turtle is as follows :

  among Translation Is translation , Is the target coordinate relative to the root coordinate x,y,z Translation in three directions

rotation It's rotation , Indicates how the target coordinate system can be rotated to the root coordinate system .Rotation There are three representations

Four 、 adopt rviz Check the positional relationship between coordinate systems

function

rosrun rviz rviz 'rospack find turtle_tf' /rviz/turtle_rviz.rviz

You can see world,turtle1,turtl2 The process of making coordinate changes between