KUKA robots use several coordinate systems for precise operation. The robot foot coordinate system (RobRoot) is fixed at the robot’s foot and serves as the origin, usually coinciding with the world coordinate system initially. The world coordinate system is a fixed Cartesian one, ensuring predictable robot movement. The base coordinate system, user – defined, indicates its position in the world system and allows robot movement along its axes. The flange coordinate system, on the robot flange, is a reference for the tool coordinate system. The tool coordinate system, customizable, defines the tool’s position and orientation, with its origin at the tool center point (TCP), enabling precise task execution along the tool’s working direction.
The coordinate systems of KUKA robots mainly include the robot foot coordinate system, the world coordinate system, the base coordinate system, the flange coordinate system and the tool coordinate system. These coordinate systems play a vital role in the robot system, and each coordinate system has its own unique applications and characteristics.
- Robot-related coordinate systems
The coordinate system is a plane or space defined by axes from a fixed point called the origin. The coordinate system is of great significance in the operation, programming and debugging of industrial robots. The robot’s target and position are located by measuring along the coordinate system axis. The following coordinate systems are defined in the robot control system:
1) ROBROOT (robot foot coordinate system)
2) WORLD (world coordinate system)
3) BASE (base coordinate system)
4) FLANGE (flange coordinate system)
5) TOOL (tool coordinate system) - Application and characteristics of coordinate systems
(1) Robot foot coordinate system
The robot foot coordinate system is a Cartesian coordinate system fixed at the robot’s foot. It is the origin of the robot and can describe the robot’s position according to the world coordinate system. In the default configuration, the robot foot coordinate system is consistent with the world coordinate system and is the reference point of the world coordinate system. The robot foot coordinate system can be used to define the movement of the robot relative to the world coordinate system.
(2) World coordinate system
The world coordinate system is a fixed Cartesian coordinate system that applies to the origin coordinate system of the robot foot coordinate system and the base coordinate system. In the default configuration, the world coordinate system is located at the robot foot. The world coordinate system is consistent with the foot coordinate system in the delivery state and can also be moved outward.
When using the world coordinate system, the robot’s movement can always be predicted, because the TCP movement in space is always unique and the origin and the direction of the coordinate system are always known.
For robots that have been zero-calibrated, the world coordinate system can always be used.
(3) Base coordinate system
The base coordinate system is a freely definable, user-defined coordinate system that describes the position of the base coordinate system in the world coordinate system. The robot tool can move according to the coordinate direction of the base coordinate system.
The base coordinate system can be measured individually and can be adjusted frequently along the edge of the workpiece, the workpiece support or the pallet. As long as the base coordinate system is known, the robot’s motion can always be predicted.
The origin and coordinate direction of the base coordinate system can be determined by the three-point method, the indirect method, or direct digital input.
(4) Flange coordinate system
The flange coordinate system is fixed on the robot’s flange. The origin is the center of the robot’s flange and is the reference point of the tool coordinate system.
(5) Tool coordinate system
The tool coordinate system is a freely definable, user-customizable coordinate system. As long as the tool coordinate system is known, the robot’s motion can always be predicted.
The origin of the tool coordinate system is called TCP-Tool Center Point. The tool coordinate system can be moved along the tool working direction or adjusted around TCP. The tool working direction refers to the working direction of the tool.
If a tool coordinate system has been accurately determined, it can be used in practice to improve the manual operation of the robot and can be used in trajectory motion programming. To determine the origin of the tool coordinate system, you can choose the XYZ 4-point method and the XYZ reference method. To determine the posture of the tool coordinate system, you can choose the ABC world coordinate method and the ABC 2-point method. Through the flexible application of these five coordinate systems, KUKA robots can efficiently and accurately complete various complex tasks and meet the high requirements of industrial production. Through the interaction of these coordinate systems, KUKA robots can demonstrate their excellent performance and reliability in many fields such as automobile manufacturing, pharmaceutical packaging, and food processing.