How much do you know about robot coordinate systems? Can you operate them proficiently? Let’s conduct an in-depth analysis of robot coordinate systems (illustrated with ABB robots).

1. Base Coordinate System

The base coordinate system is a Cartesian coordinate system referenced to the robot’s mounting base, used to describe the motion of the robot body.

It is indispensable for all robots and serves as the fundamental coordinate system required for the TCP (Tool Center Point) to move within 3D space.

• X-axis: Forward and backward (facing the robot)
• Y-axis: Left and right
• Z-axis: Up and down

This coordinate system follows the right-hand rule.

2. World Coordinate System

The world coordinate system is a Cartesian coordinate system referenced to the ground. It is commonly applied in multi-robot coordination systems and robots equipped with external axes. In 90% of scenarios, the world coordinate system coincides with the base coordinate system. However, they differ under the following two conditions:

Robot mounted in an inverted configurationFor inverted robots, the Z-axis direction of the base coordinate system is opposite to that of the world coordinate system. The robot can be installed upside down, while the ground reference remains unchanged.

Robot with external axesThe world coordinate system maintains a fixed position, whereas the base coordinate system moves synchronously as the entire robot shifts.

3. Tool Coordinate System

The tool coordinate system takes the tool center point as its origin. Robot motion trajectories refer to this new tool center point, instead of the default wrist center point Tool0 of the robot.

Examples: During welding, the tool is a welding torch, so the origin of the tool coordinate system can be set at the tip of the welding torch. When handling workpieces via suction cups, the tool coordinate origin can be defined on the surface of the suction cup.

. Work Object Coordinate System

The work object coordinate system is a Cartesian coordinate system referenced to the workpiece, used to define TCP movements.

Making full use of the work object coordinate system greatly improves programming efficiency.

Example: Suppose trajectory programming is completed for processing Workpiece 1. When processing Workpiece 2, there is no need to rewrite trajectories. Simply switch the coordinate reference from Work Object 1 to Work Object 2.