How to work around snapshot position calibration pose problems

T800_412

Is there a best practices method to get around having to do snapshot position calibration? I would like to do a cam locate with the UR10 positioned where the camera is horizontal, and the UR10 arm is very close to joint limits and some mechanical obstructions. If I do a normal calibrate from there, the arm will either hit the obstruction, or the joints will collide and stop the robot.

I tried calibrating with board laid horizontal so the arm can move freely, but get error messages that the arm will not be able to reach all the calculated poses.

Enric

Hi, @T800_412

Snapshot Position will determine the field of view, notice that the calibration step position does not have to be the same as Snapshot position. Thus, you can have a small field of view, then move back for calibration step.

Calibration board position.

Figure 7.3.1 : Calibration board position.

Specification	Value
	UR3	UR5	UR10
Maximum board distance (cm)	26	34	42
Minimum board distance (cm)	42	70	98

Etienne_Samson

@T800_412 to add onto what @Enric said, if you want to use closer to singularity (outside the calibration area in the picture Enric posted) you can use the copy feature of the calibration. Basically run a calibration in a workable area and then copy it to an area closer to singularities. This will work if you are on the same workplane.

T800_412

Etienne_Samson said:

@T800_412 to add onto what @Enric said, if you want to use closer to singularity (outside the calibration area in the picture Enric posted) you can use the copy feature of the calibration. Basically run a calibration in a workable area and then copy it to an area closer to singularities. This will work if you are on the same workplane.

When you say same workplane, do you just mean the same orientation, but further away?

The wheel I want to inspect is positioned as you would see a tire on a car, so the camera is looking at it from the side to see the full diameter of it. I could put the calibration board higher off the table, and further away from the robot base, which would then allow the arm to move around as it needs to for calibration. Will that work?

T800_412

@Etienne_SamsonEtienne_Samson said:

@T800_412 to add onto what @Enric said, if you want to use closer to singularity (outside the calibration area in the picture Enric posted) you can use the copy feature of the calibration. Basically run a calibration in a workable area and then copy it to an area closer to singularities. This will work if you are on the same workplane. object

Could you please explain how to copy feature of the calibration? I am in this same predicament again, this time the arm hits a physical object.

bcastets

To create a new snapshot position by copying the calibration of another snapshot position you can proceed as follow:

1. Create a point feature. Make it variable and set a position.
2. Go to installation tab>Camera>snapshot
3. Select the feature point you previously created in the pull down list
4. Select the snapshot position from which you want to copy calibration
5. Click on copy button

T800_412

@bcastets Thank you. In his previous comment, @Etienne_Samson stated this will work if you are on the same workplane. Does that mean, for example, Z=0 (robot base) for the workplane for both, or could one be Z=0.020, and the other be Z=-0.010.

With my initial attempt at doing this, the copied snapshot position, when trying to find the object in parametric teach, it cannot be located. Is that do to the 30mm offset in Z?

bcastets

When you calibrate the camera, the plan on which you place the calibration board is your workplan. The workplan is the plan where are placed objects to be detect.

If you create a new snapshot position by copying another snapshot, you have to use the same workplan.
Objects to detect should be placed on the plan where you previously placed the calibration board.

T800_412

So I am back to the beginning question with this whole conversation. Is there any way to calibrate a snapshot position, or add some programming to work around needing a snapshot position where the robot arm is unable to move through all of the calibration image positions? I cannot use the copy feature, because the workplane for these two features is not the same, and it is not feasible to disassemble the physical obstructions to calibrate where the snapshot position needs to be.

bcastets

I would proceed as follow:
Create a snapshot position from scratch using the calibration board to define your workplane where you don't have reach issue with the robot. Then create a snapshot position by copying the snapshot you previously created.

The first step remain the definition of the workplan. For this step, you have to find a place where you don't have reach issue to perform the calibration.

If you cannot find a place without reach issue to do the calibration, you cannot setup the camera.

David_Gariepy

@T800_412
The following function will allow offsetting a calibration in a program
snapshot_position_offset = p[x,y,z,rx,ry,rz]
For example, the following will offset the calibration 100MM+ in the X direction from the robot base
snapshot_position_offset = p[0.1,0,0,0,0,0]
This function should be used with the ignore_snapshot_position=True function


This means you can calibrate a snapshot position and teach a part beside the production location, then offset it to the desired position.
Note that this will affect precision and is working only for x,y,z variation.  Any rotation of Rx,Ry,Rz won't be affected.