What are joint motion and linear motion in robotic programming?
Joint motion commands the arm to move through coordinated joint positions. The tool's path between endpoints is not necessarily a straight line. Linear motion commands the tool to follow a straight Cartesian path while the controller coordinates the joints to maintain the required trajectory and orientation.
What this means in practice
Joint motion can be useful for transfers between clear locations. Linear motion often suits approaching a fixture, inserting a component, or following a process path. The appropriate choice depends on clearance, posture, tool orientation, and the controller's motion capabilities.
Consider orientation and transitions
A straight tool path can require substantial changes in individual joints, especially near difficult postures. Joint movement can reach the same endpoint through a different tool path. Neither choice is inherently better; each must suit the available clearance and process requirement.
Blending between segments can reduce unnecessary stopping, but it may alter the path near a waypoint. That matters around fixtures and contact operations. Confirm the controller's behavior and test the resulting trajectory with the actual tool, load, and required process tolerance.
Key points
Evaluate the entire intermediate path rather than only its endpoints.
Use controlled approach and retreat paths where access is restricted.
Check joint limits and difficult configurations during Cartesian motion.
Practical example and next step
For example, a gripper may travel with joint motion above the work area and use linear motion for the final approach into a fixture. Simulate and test both segments with the real tool and carried part before approving the production program.