The axis parameter is null.

Cause:

1. Joint axes are not configured in the PLC;
2. The robot configuration file has not been received;

Troubleshooting:

1. Call the receive functions in the correct order in the PLC program;
2. Check whether the robot configuration file is damaged;

Solution:

1. The PLC program must call the receive functions in sequence.
2. Contact after-sales support and copy the correct robot configuration file to the controller.

Case sharing:

None.