Hi,
this is almost the same as for the turtlesim. You can lookup the transformation between arbitrary coordinate frames. So, say you want to find the transformation from your end-effector ee_link
to the base of the manipulator base_link
. You can do this with (better place it in a try-catch enviroment):
tf::StampedTransform transform;
listener.lookupTransform ("/ee_link", "/base_link", ros::Time::now(), transform);
However, first it would be helpful to open rviz and lookup the names of the coordinate frames, if you didn't do it so far.
I hope, I got your question right, if not, don't hesitate to ask again.
Cheers,
Matthias
Edit: It seems, that you have to complete a few steps more before you need the transformations served by ROS. At first, create a model of your robot. For this purpose you can use Denavit–Hartenberg parameters. This will help you to get the forward kinematikc. The inverse kinematic will be an optimization problem, which can't be solved in a closed form for a six axis robot like yours.
However, maybe you should have a look at this Matlab toolbox by Peter Corke. It is an open-source toolbox which will help you to learn a lot about your task.
Edit 2: Your Robot has 5 axis, not 6. But nonetheless, it should make no difference for you.