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dahonoradahonora Posts: 17 Apprentice
Hi there!
I am working with a camera mounted to a UR10e gripper. The application requires very high precision, so I am performing a handEye calibration to measure the relatives angles between the TCP and the camera. They are suppose to be [0, 0, 180], but because the mounting is not precise, I know that the error is around 1° in each coordinate. 
To do the calibration I need to get the UR rotation matrix from the axis-angle notation. I created a Polyscope program to extract the robot poses. It gets them in axis-angle notation, in radians. However, If you check the axis-angle notation on the Polyscope (under move) and you compare with the script values of that same point, you will see a difference. From another post, I understood that the Polyscope values are scaled following the next formula: 

p[x,y,z] - script values
scale = 1 - 2*PI/length(p[x,y,x])
polyscope_values = [scale*x, scale*y, scale*z]

I took 5 different poses on the UR and realized, that this formula is correct. 
But, which one should I use to get the rotation matrix?


  • David_GouffeDavid_Gouffe Vacuum Beta tester Posts: 56 Handy

    From my point of view, it would be easier to use Robotiq Wrist Camera. It came with a URCap including wizard for calibrating the camera mounted on the robot, wizard for identifying parts and then retrieving parts is only a matter of making the move relative to the reference variable. 

    No maths, no wondering. Just finding the part and picking it. The handEye calibration is already done in the background.  

    Maybe you could give it a try and "Start Production Faster" . 

    Enjoy UR programming. And hope you will enjoy Robotiq Wrist Camera soon. 


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  • dahonoradahonora Posts: 17 Apprentice
    Thank you for the suggestion

    For our specific application is not possible to use a Wrist camera. We are working with a RealSense D415 stereo camera to get depth information of the scenes. We are working in a high unstructured environment, so I don´t think that we could change that.

    The part of the handEye calibration is fixed already. I am anyway curious about the difference in the axis-angle values and the scaled issue. 

    Kind regards,  
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