ROS Answers: Open Source Q&A Forum - RSS feedhttps://answers.ros.org/questions/Open source question and answer forum written in Python and DjangoenROS Answers is licensed under Creative Commons Attribution 3.0Tue, 17 Feb 2015 12:49:24 -0600Finding the relative pose of a robot gripperhttps://answers.ros.org/question/203267/finding-the-relative-pose-of-a-robot-gripper/I have a robot arm with a gripper. I know the gripper pose (relative to the robot base coordinate system) at any moment. At startup, I record the pose of the gripper and set this as the original pose `O`. Then, the gripper moves to its new pose `N`, again in the robot base coordinate system. What I want to calculate, is `R`, the relative pose of the gripper *in the coordinate system of the original pose* `O`, rather than in the coordinate system of the robot base, which would just be `N`.
So, `O` = original pose, `N` = new pose, `R` = relative pose
From my calculations:
`O` * `R` = `N`
Therefore:
`R` = `O^-1` * `N`
However, from my observations, `R` is the pose of the hand relative to the original pose, but in the coordinate system of the robot base. I want it to be in the coordinate system of the original pose. How do I get this?Tue, 17 Feb 2015 05:10:40 -0600https://answers.ros.org/question/203267/finding-the-relative-pose-of-a-robot-gripper/Answer by 130s for <p>I have a robot arm with a gripper. I know the gripper pose (relative to the robot base coordinate system) at any moment. At startup, I record the pose of the gripper and set this as the original pose <code>O</code>. Then, the gripper moves to its new pose <code>N</code>, again in the robot base coordinate system. What I want to calculate, is <code>R</code>, the relative pose of the gripper <em>in the coordinate system of the original pose</em> <code>O</code>, rather than in the coordinate system of the robot base, which would just be <code>N</code>.</p>
<p>So, <code>O</code> = original pose, <code>N</code> = new pose, <code>R</code> = relative pose</p>
<p>From my calculations:</p>
<p><code>O</code> * <code>R</code> = <code>N</code></p>
<p>Therefore:</p>
<p><code>R</code> = <code>O^-1</code> * <code>N</code></p>
<p>However, from my observations, <code>R</code> is the pose of the hand relative to the original pose, but in the coordinate system of the robot base. I want it to be in the coordinate system of the original pose. How do I get this?</p>
https://answers.ros.org/question/203267/finding-the-relative-pose-of-a-robot-gripper/?answer=203310#post-id-203310If you're asking how to implement the solution in ROS, [tf](http://wiki.ros.org/tf) is a powerful library that should exactly suits your need.
If you're asking general robotics ideas, this forum is not the place for it. I recommend to ask on [robotics.stackexchange.com](http://robotics.stackexchange.com/).
Tue, 17 Feb 2015 12:49:24 -0600https://answers.ros.org/question/203267/finding-the-relative-pose-of-a-robot-gripper/?answer=203310#post-id-203310