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, 11 Jul 2017 03:21:46 -0500Can someone explain geometry_msgs as used for robot arm poses e.g.?https://answers.ros.org/question/265988/can-someone-explain-geometry_msgs-as-used-for-robot-arm-poses-eg/I'm trying to work with a robot arm, and struggling to find anything to explain in detail how anything works. I have gone through the ROS documentation tutorials, and the PR2 moveit tutorial for example. Pose goals are used but never explained.
What do position and orientation variables refer to in this context? Position and orientation of what relative to what? What does the origin refer to, where is it specified and how is it retrieved?
The robot I'm working with has 7 joint angles. Are poses and joint specifications redundant, or can they be used together? It seems from my specification that both are simultaneously significant, though I would think the joint angles completely specify the position. Again, what does a pose goal position and orientation mean for a robot arm determined by 7 joint angles?
Thanks!
-Jason
P.S. If you are thinking that I just don't know enough about robotics or ROS to understand, please be so kind as to direct me to where I can find information sufficient to actually LEARN (I'm an ECE PhD btw).japalmer29Tue, 11 Jul 2017 03:21:46 -0500https://answers.ros.org/question/265988/Align x-axis of end effector with vector in spacehttps://answers.ros.org/question/253767/align-x-axis-of-end-effector-with-vector-in-space/Hi all,
I really need your help. I have tried now for a few days to align my end effector with a simple 3d vector in space.
Thats's a quite simple task: given position = x,y,z and given orientation vector = a,b,c but I can't find a function in moveit! to do so. I dont know how to form the geometry_msgs::Pose by position (of course) and **quaternion.** I tried everything like:
- getRPY from current pose
- convert to "vector" (which is of course not equal and simple, lose roll)
- calculate perpendicular vector (cross product) and angle (dot product) between the two vectors above (current+given goal orientation vector)
- from this calculate the quaternion by constructor tf::quaternion(perpendicular vector, angle)
That couldn't be the truth, I must have missed something... please advise.
I am using ROS Indigo, Ubuntu 14.04LTS, Moveit!
Thank you very much in advance!
HannesHannesIIIFri, 03 Feb 2017 12:41:54 -0600https://answers.ros.org/question/253767/moveit - nearest reachable pose for arm gripperhttps://answers.ros.org/question/75448/moveit-nearest-reachable-pose-for-arm-gripper/Hi,
I am working with a robotic arm and I have the following question (I am completely new to moveit): I can give the gripper a Pose to go to but the problem is that the arm may not be able to get into the pose, even though it is in its range of motion.
Is there some automatic way of finding the nearest pose that the arm can get into?
Thanks a lotvonovakThu, 29 Aug 2013 01:17:31 -0500https://answers.ros.org/question/75448/