Units and frames¶
Units¶
Millimetres and degrees, everywhere, with no exceptions and no unit selector. Masses are kilograms. A field never means anything else than what this paragraph says.
Coordinate frames¶
A position is meaningless on its own; it means something in a frame.
- World — the fixed origin of the scene. Everything can ultimately be expressed in it.
- User frames — origins you create, usually one per pallet station or per machine. A reference object is how you make one.
- Tool — carried by the robot, at the TCP. Moving in the tool frame means moving relative to the gripper, whichever way it is pointing.
Working in a user frame is what makes a cell maintainable: when the pallet station is moved by 30 mm, you correct the frame and every position on it follows.
Positions and orientation¶
A position is a point and an orientation — where the tool is and which way it faces. Two positions with the same point and different orientations are different positions, and the robot reaches them differently.
Robot configuration¶
An industrial arm can often reach the same position in more than one posture: shoulder front or rear, elbow up or down, wrist flipped. These are its configurations.
They matter because the robot cannot swap between them while moving. A trajectory that would need to change configuration mid-path is not a trajectory, and the software will tell you so rather than trying.