  In this article, we plan to provide an introduction about some basics about
robots for readers. Several key topics of classic robotics will be introduced,
including robot representation, robot rotational motion, coordinates
transformation and velocity transformation. By now, classic rigid-body robot
analysis is still the main-stream approach in robot controlling and motion
planning. In this article, no data-driven or machine learning based methods
will be introduced. Most of the materials covered in this article are based on
the rigid-body kinematics that the readers probably have learned from the
physics course at high-school or college. Meanwhile, these classic robot
kinematics analyses will serve as the foundation for the latest intelligent
robot control algorithms in modern robotics studies.
