I am trying to measure the precision error of a gripper that is mounted to the flange of a 6 DOF industrial robot. The gripper-design is rather complex, therefore we would like to make sure it is operating precisely.
I think a simple way to measure the gripper-precision is to use a camera and visual markers on a piece that is gripped. See the following illustration of the setup. The colorful box mocks a part that is being gripped by the gray gripper that is mounted to the robot flange.
To get data to work with, I imagine the following procedure:
- the robot picks up part 1
- the robot holds the red side of the part in front of the camera, which takes a picture
- the robot rotates the part by actuating its 6th joint by 90 degrees, the camera takes a picture of the green side
- the robot rotates the part by another 90 degrees, the camera takes a picture (back side)
- the robot rotates the part by another 90 degrees, the camera takes a picture
- the robot places the part back in the nest
- go back to step 1, until 10 iterations are completed
In summary: Each time the robot gripped the part, a batch of pictures from different sides are taken.
The error, that needs to be calculated, is defined as the pose-difference of the part that is caused by small errors in the gripper mechanism. The error has 6 dimensions.
The camera can be assumed to be calibrated.
Using two batches of pictures from two different grips: How can I use the image plane coordinates of the $N$ features attached to a part, to calculate the pose-difference of the part?