Reference coordinate system of mobile platform for Ros learning

A basic concept

1 Reference System (reference frame): Because of the relativity of motion description, to describe the motion of an object must choose other objects for reference, the object used for reference is called the reference system. (Turn multiple solutions into unique solutions)

2 coordinate system (coordinate system): to quantitatively describe certain properties.

3 Reference coordinate system (coordinate frame): In a reference system, the established coordinate system has the properties of 1 and 22.

Reference coordinate system in two ros (coordinate frames)

1 Base_link: The coordinate system established in the mobile robot base

2 Odom: World Fixed coordinate system, robot posture in this coordinate system, long drift, but Odom in the attitude description is

Smooth. (good local effect)

3 Map: The World fixed coordinate system, z-axis upward, the mobile platform relative to the map coordinate system does not drift significantly with time, map is discontinuous, meaning that the mobile platform in the map coordinate system can jump discrete. (Good overall effect)

4

The relationship between the three coordinate systems (from the parent coordinate system to the transformation of the sub-coordinate system, you can transform the points in the coordinate system into the parent coordinate system)

(Differentiate between coordinate system transformations and coordinate transformations)

Each coordinate system has a parent coordinate system and can have multiple sub-coordinate systems

Odom->base_link, calculate and broadcast with odometer resources (visual odometer, wheel odometer, IMU, etc.)

Map->base_link, calculated by positioning, but broadcast is map->odom.

Four reference documents

Http://wiki.ros.org/action/fullsearch/tf2?action=fullsearch&context=180&value=linkto%3A%22tf2%22

John Craig's book, Introduction to Robotics [1986, 1989]. We follow his conventions for transform and point indices.

Reference coordinate system of mobile platform for Ros learning