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I'll try to answer at least some aspects of this: The notion of "fixed" here refers to a joint with 0 DOF. Essentially, this means the joint applies an identity transform to whatever frame is the parent joint. If you add that to the robot, your object will move with the robot.

If you would like to have the object not move, or do something like you suggest with the rgbd sensor, you have to consider the robot as being something that has the following structure.

virtual_joint(fixed)-> imaginary_link-> joint(floating) -> imaginary_link -> attachedObject joint(planar) -> base_link

I do not recall if this allows feeding base_frame into the planar joint above (it may be the case only virtual_joints allow that, but I don't think we implemented support for chained virtual joints, so you might have to feed in your transforms manually. When you attach the object, in a fixed fashion, it will only move if you adjust the transform for the floating joint.

Hope this helps.

I'll try to answer at least some aspects of this: The notion of "fixed" here refers to a joint with 0 DOF. Essentially, this means the joint applies an identity transform to whatever frame is the parent joint. If you add that to the robot, your object will move with the robot.

If you would like to have the object not move, or do something like you suggest with the rgbd sensor, you have to consider the robot as being something that has the following structure.

 virtual_joint(fixed)->
  imaginary_link->
     joint(floating) -> imaginary_link -> attachedObject
     joint(planar) -> base_link

base_link

I do not recall if this allows feeding base_frame into the planar joint above (it may be the case only virtual_joints allow that, but I don't think we implemented support for chained virtual joints, so you might have to feed in your transforms manually. When you attach the object, in a fixed fashion, it will only move if you adjust the transform for the floating joint.

Hope this helps.