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IFL-CAMP / easy_handeye

Automated, hardware-independent Hand-Eye Calibration
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A small question about handeye calibration for 3DoF robot #48

Closed T2honda closed 4 years ago

T2honda commented 5 years ago

Hello

 Thank you very much for the great package.
 I want to do some picking task for the 3DoF ( x, y, z)  robot arm.
 I want to make the eye to hand calibration for 3DoF ( x, y, z ) robot by the package, rather than the normal 6 DoF robot.
 I got the following figure by rviz:

AR

 and we can get the point cloud like that:

point_cloud

I want to know can I get good calibration result for the 3DoF robot by the package ?
For the case of 3DoF robot, could you please give some special suggestions for getting precision eye to hand calibration result ?

I am very appreciated for your kindness help.

Best Regards
marcoesposito1988 commented 5 years ago

Hello @T2honda,

from the images, I guess that the joint axes are parallel. In this case, I am afraid that the robot cannot rotate the marker in all 3 directions, so the calibration problem is undetermined and the algorithm cannot work.

Furthermore, is the camera external to a mobile robot? In order for this to work, you would need to stop the robot base, and calibrate the arm just before picking up the object. Then perform the grasping without moving the robot base.

In your case I would try to measure the pose of the marker with respect to the end effector by hand.

T2honda commented 5 years ago

Dear Marco

     Thank you so much for your kindness and useful suggestion.
     I understand that.

    Yes, the camera external to the robot arm. Actually, it is not a mobile robot, just a robot arm (URL about the robot arm: https://www.dobot.cc/dobot-magician/product-overview.html )

    However, I don't understand the last sentence "try to measure the pose of the marker with respect to the end effector by hand" completely.  Since I just sticked the marker on the center of end effector, so they only exist difference in Z axis. 

    Do I understand it wrong?
    Could you please explain the last sentence again?
    I am very appreciated for your kindness help.

    Best Regards
marcoesposito1988 commented 4 years ago

Hi @T2honda,

I meant to directly measure the transformation by hand, such as with a ruler, or a caliper. If you have the URDF of the robot, and you know the location of the end effector frame on the flange, you may be able to measure this transformation with a precision that may suffice for your use case.

marcoesposito1988 commented 4 years ago

Closing for inactivity