Changed the origin of the left and right finger joints to avoid collision

[crthilakraj]

• changed the origin of the left and right finger joints to avoid collision
• corrected the depricated hardware interface syntax in common.xacro file.

[christian-rauch]

Can you rebase your PR on master that contains #216?

[crthilakraj]

Can you rebase your PR on master that contains #216?

Done!

[christian-rauch]

Thanks. Did you get these values +/-0.0055 from a datasheet or are they determined empirically?

[crthilakraj]

/-0.0055 f
As per the URDF of pg70 , width of the finger is 0.01 and the lower limit for the joint is -0.001 hence the value 0.0055 , so that with in the range of joint limit there will be no collision between left and right finger joint.

[christian-rauch]

/-0.0055 f
As per the URDF of pg70 , width of the finger is 0.01 and the lower limit for the joint is -0.001 hence the value 0.0055 , so that with in the range of joint limit there will be no collision between left and right finger joint.

Can you reference a document from https://schunk.com/no_en/clamping-technology/series/pg/ that contains this information? I only found another URDF at https://github.com/SmartRoboticSystems/schunk_grippers/tree/master/schunk_pg70/urdf and it contains the same values.

I would like to document the change of the URDF because I do not have the physical PG 70 to verify the new values.

[crthilakraj]

i took the values from the urdf file from schunk description package. File name https://github.com/crthilakraj/schunk_modular_robotics/blob/indigo_dev/schunk_description/urdf/pg70/pg70.urdf.xacro.

[christian-rauch]

i took the values from the urdf file from schunk description package. File name https://github.com/crthilakraj/schunk_modular_robotics/blob/indigo_dev/schunk_description/urdf/pg70/pg70.urdf.xacro.

The URDF file you are linking is part of this PR. What I am asking for is a secondary source or a way how you determined these values.
Are you referring to <box size="0.03 0.01 0.01"/>? Can you paste a screenshot of the gripper state with and without this change? I want to have this documented here, such that the change is reasonably justified.

[crthilakraj]

yes i am referring to the value mentioned <box size="0.03 0.01 0.01"/>
Following are the requested images.

1. with changes.
   
2. without change.
   .

As per urdf file origin of both finger_left_joint and finger_right_joint have same origin, hence there will be collison of the joints as shown in above image. Fom <box size="0.03 0.01 0.01"/> we know the collision geometry is l=0.03, w= 0.01, height=0.01. and from <limit effort="10" lower="-0.001" upper="0.0301" velocity="0.041"/> the lower limit is -0.001. so to avoid collision, i calculated the finger_xx_links origins y displacement ( 0.01 + 0.001)/2 .

[christian-rauch]

@crthilakraj Thanks for the clarification. I thought that we might need to change the joint limits instead of the joint origin, but your images show that the bracket is actually wrongly positioned.