Mismatch between coordinate monitor and actual motion using SMC_GroupJog2, MC_MoveLinearAbsolute (6DOF)

2026-10-16T13:22:34.233000Z

Hi darwin03,

as can bee seen at the end of your video, the direction of rotation now seems correct for all axes.

I can only guess, but the most likely reason are different denavit hartenberg parameters in the SoftMotion axis group editors and the robot used in the simulation tool. Maybe some arm lengths differ, maybe some offsets are given with opposite sign.

I would again refer you to https://content.helpme-codesys.com/en/libs/SM3_Transformation/Current/SM3_Transformation/Function-Blocks/Standalone-Kinematics/Articulated-Robots/6AxisArticulated/Kin_ArticulatedRobot_6DOF.html. Please double check all parameters and the table of the DH parameters given there and compare that against the robot in the simulation tool.

Also: did you configure any tool in CODESYS? I would suggest to simplify and remove any tools for finding the source of the wrong movements.

Best regards,

Georg

Mismatch between coordinate monitor and actual motion using SMC_GroupJog2, MC_MoveLinearAbsolute (6DOF)

2026-10-15T08:16:34.256000Z

Hi Georg,

Thank you very much for your help and for taking the time to look into my issue!

After reversing the directions of A2 and A3, the robot now moves correctly according to the coordinate system. That solved the main issue with the joint rotation directions.

However, I still have two issues:

When I command the robot to move along the X, Y, and Z axes, the movement seems slightly off, and the trajectory appears somewhat diagonal instead of following a straight line along the commanded axis.
The A6 axis also rotates during the movement, whereas I would expect it to maintain its orientation and remain unchanged.

Do you have any suggestions on how I could correct the Cartesian linear movement and keep A6 fixed during the motion?

Thank you again for your support!

Best regards,
Darwin

Video link: https://drive.google.com/file/d/1tnokDYoNUEDy--eQtX_JZavMVSn-a9Le/view?usp=sharing

Mismatch between coordinate monitor and actual motion using SMC_GroupJog2, MC_MoveLinearAbsolute (6DOF)

2026-10-12T11:10:07.261000Z

Hi darwin01,

looking at the video and comparing the movement with the first figure in https://content.helpme-codesys.com/en/libs/SM3_Transformation/Current/SM3_Transformation/Function-Blocks/Standalone-Kinematics/Articulated-Robots/6AxisArticulated/Kin_ArticulatedRobot_6DOF.html, I think that the direction of rotation does not match between the RoboDK model and the CODESYS 6DOF kinematics.

In the CODESYS kinematics, A1 and A2, when moved in positive direction, rotate into the opposite direction to what the RoboDK model does. This could explain the strange movements.

For real axes, you could change the direction using the "Invert direction" flag of the scaling/mapping page. For your simulation, you could manually invert the position of the axes A1 and A2 before sending them to RoboDK. (A0 seems correct, please also check A3, A4, and A5. The figure I mentioned gives the order of positive rotation with arrows through the joints. You can use the right-hand-rule to see what the positive rotation is.)

Best regards,

Georg

Mismatch between coordinate monitor and actual motion using SMC_GroupJog2, MC_MoveLinearAbsolute (6DOF)

2026-10-09T07:42:28.431000Z

Hi Georg,

Thanks for your previous suggestion. I was able to resolve the issue!

I'm now trying to build the 6DOF robot again, but I'm not sure why this is happening. Even when I simulate it in RoboDK using the joint angles from my code, the robot's motion still seems abnormal.

Do you have any ideas what might be causing this?

Thank you for taking the time to look into my question!

Best regards,
darwin03

Video link: https://drive.google.com/file/d/1PBqS4yIY2R_CZ3celSKz-BXVRk8pCHKz/view?usp=sharing

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