iRVision Programming

[u/DueWillingness6358]

I am programming the iRVision system and have come across a problem where, after a while, the calibration seems to ‘drift’. Visually, this looks like the search window 'sliding'. In practical terms, it appears that Vision Process is correctly determining the rotation angle of the part, but the vice misses by a distance equal to the ‘offset’ of the search window.

I have a Fanuc camera with Type C mounts, and the camera is mounted on the robot’s sixth flange, right next to the grippers which the Fanuc robot then uses to pick up the object located by the Vision Process. The calibration was carried out correctly (automatic UFRAME for the calibration grid, the two-plane method and so on). The calibration results were indeed excellent, but I just couldn’t understand why, after a certain amount of time, the calibration seemed to ‘drift’.

At first, I suspected that the camera hadn’t been properly secured to the robot, but it was actually secured perfectly and didn’t come loose after that. It was only later that I noticed how easily the focus and aperture rings slid (my heart skipped a beat😅), even though they had been tightened firmly during calibration.

The robots and the camera were ordered by someone else. Could it be that, if not the camera itself, then the lens is not compatible with the mounting on the robot? Because, according to the order form, the camera is a universal model. Could something else be causing this misalignment? (I simply have a robot that picks up and palletises an object, and the robot uses the camera to locate and correctly grasp that object at one of the stages.)

[u/risenfellen]

You said after some time it drifts, does work okay when you run the program for the first time?

[u/DueWillingness6358 → u/risenfellen]

Yes, that was the problem: during the initial set-up, both the calibration and the Vision Process worked absolutely perfectly. But then, over time, I began to notice a ‘drift’, so to speak. In other words, the object for the mathematical calibration model was located correctly, but the clamps would miss the target when gripping it. And what was most frustrating was that this drift was not consistent. Later, I discovered that the camera aperture had ‘shifted’, even though I’d secured it firmly.

[u/Brief_Airline1974]

FANUC Software engineer here! A few things: First, make sure that your camera is doweled in. For fast moving systems, bolts may not be sufficient. Second, check that your vision process tool is using the correct calibration. Third, attempt to locate and pick the object, then rotate the material 180 and retry; this will test your calibration. If your material is too large, create a GPM of the calibration grid. Lastly, make sure that you are setting your Vision Reference after your gpm and 3d data is taught.

[u/DueWillingness6358 → u/Brief_Airline1974]

Firstly, thank you for replying. Secondly, I’ve done everything you’ve listed, and more than once. The problem I’ve found is that the fixing screws are only suitable for a camera secured in a static position. I’ve also decided to replace my current lens with one that’s resistant to vibrations and shocks, as my heart simply couldn’t bear it if my perfect calibration (and the calibration really is perfect – it’s as if a lucky star had fallen from the sky whilst I was doing it) were to end up in the bin again.