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Sebastien
Posts: 219 Handy
Repeatability numbers for the Robotiq camera. |
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Hi Pros,
here is a video that I made where I simply locate a white piece of cardboard roundly shaped on a flat surface. I locate the part using the Robotiq camera mounted on a UR5. I don't move the part between snapshots. So when the robot goes down with the pen on the object, it should hit at the exact same location everytime.
I would like to get more accurate then what you see on the video. Of course I could snapshot closer to the object but I want to keep a relatively good field of view. What are your thoughts on this? Do you have any tricks or can you put some numbers on the repeatability we should expect to get from Robotiq's camera with UR5?
https://www.youtube.com/watch?v=wkxwLczp8VU&feature=youtu.be
here is a video that I made where I simply locate a white piece of cardboard roundly shaped on a flat surface. I locate the part using the Robotiq camera mounted on a UR5. I don't move the part between snapshots. So when the robot goes down with the pen on the object, it should hit at the exact same location everytime.
I would like to get more accurate then what you see on the video. Of course I could snapshot closer to the object but I want to keep a relatively good field of view. What are your thoughts on this? Do you have any tricks or can you put some numbers on the repeatability we should expect to get from Robotiq's camera with UR5?

Tagged:
We will release numbers as soon as possible!
[email protected]
It makes sense a lot. So the closer to the center that I will be, when teaching a round/symmetrical target, the more accurate I will be!
I will run some more testing!
I was looking at this application more closely. What you said makes sense but based on other vision hardware that we work on, there should be a way around it.
Snapping and finding the round shape is quite simple using Pattern matching algorithm or blob finder. Then we get the X,Y position of the geometric center of our round part along with the angle between the taught and found pattern. I would just discard this angle and send X-Y position to the robot. This way I should point directly in the middle every time if the robot keeps the same orientation on the plane where it has to pick.
What do you think?
[email protected]
We did the same testing as above but with a fixed Cognex Camera. The Cognex camera has a really nice calibration feature built in its interface. This allows you to calibrate the robot with the vision system by simply moving the robot to 'calibration targets'. Once done, coordinate values output by the camera are in the robot's coordinate system.
You will see in our video below that we are really repeatable when taking snapshots while leaving the white round piece at the same spot. We are 1-2mm off when we move the piece on the table. This is do to our calibration and our setup. We did not spend much time on the calibration since we simply wanted to run some testings rapidly. Furthermore, our touch tool was a Sharpie that could move a bit in its setup and the camera was installed on a stand that could vibrate a little. So our conclusion was that this setup worked well for repeatable results on these round object. To increase accuracy we would:
Below is the video. Note that we can see two different part sizes in the video. The first one is about 1,25'' in diameter and the second one 0.5'' in diameter. Using blob tool we can easily switch between the two parts!