HannesIII's profile - activity

Sorry for my late response, wasn't able to get in. The problem is that the robot can reach a state using different joint values. E.g. one joint value can be 20 deg or 200deg (+180deg). So my solution would be to tell the robot to use a value between [-180,180] for a pose. How can I do that?

Hello together,

I have a question regarding planning with a UR10 arm and Moveit. I try to compute a Cartesian Path around an object. And it frequently happens that the robot can not successfully follow the path until 100%. E.g. it stops after 59% etc. Looking on the control panel for the robot, I noticed that it could not execute the path completely because a joint limit is reached (-2 pi/2 pi). It is a little bit strange to me because normally Moveit should know that it will violate that limit and of course just setting the start state to something around 0 degree would do the job, but it starts for example sometimes with 250 degree for that special joint. Could you help me?

Thank you very much in advance!

Hannes

Hello, did you found a solution?

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!

Hannes

Hey bluefish, I know the questin is rather old, but could you tell me a bit of how you managed it to align your end-effector with a given vector? I tried to getRPY->CurrentVector (using sin, cos) -> create quaternion between CurrentVector <> given goal vector. Failed due to wrong current vector...

Hi, thank you for your answer! It is the correcht approach. The next step is just to create a quaternion out of the matrix from your post and set it as orientation for the goal pose. Unfortunately I thought a bit to complicated. I will mark your answer as correct!

Hi all,

I am using a UR10 with Moveit! for motion planning (move group interface C++). I want to align my end-effector with a vector in space. I read a lot about quaternions and rotation in 3d space, but at the moment I struggle to find out the best way to do this.

I have a given point (x,y,z) and a given vector for orientation (a,b,c), how can I set a target pose for the end-effector? Tried to use a geometry_msg but it needs a point and a quaternion. Also tried to calculate a quaternion between the current vector and the goal vector using cross product etc. but therefore I would need the vector of the current pose and I struggled to find it out -.- Does anybody know a clean solution for my problem?

Thank you very much in advance!

Hannes

I did not update the .yaml file. I think the joint limits are set by the xacro file above, aren't they? Thank you for your response!

Hello,

I am using MoveIt! for a simulated UR10 in Gazebo. When I try to tell the MoveGroup to move the end effector to a position (x,y,z,w), MoveIt! ignores the joint limits which are set in the launch file (-pi/2, pi/2, etc.). This leads frequently to a collision between the shoulder_link and the ground plane. Does anybody know why MoveIt! ignores these limits? If so, how can I resolve this problem? I am using ROS Indigo and Gazebo 2. If you will need more information, please advise :)

Thank you very much in advance! Kind regards, Hannes

Update1: I am referring to this xacro file, the ur10_joint_limited_robot.urdf.xacro...

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro"
       name="ur10" >

  <!-- common stuff -->
  <xacro:include filename="$(find ur_description)/urdf/common.gazebo.xacro" />

  <!-- ur10 -->
  <xacro:include filename="$(find ur_description)/urdf/ur10.urdf.xacro" />

  <!-- arm -->
  <xacro:ur10_robot prefix="" joint_limited="true"
         shoulder_pan_lower_limit="${-pi}" shoulder_pan_upper_limit="${pi}"
         shoulder_lift_lower_limit="${-pi/2}" shoulder_lift_upper_limit="${pi/2}"
         elbow_joint_lower_limit="${-pi}" elbow_joint_upper_limit="${pi}"
         wrist_1_lower_limit="${-pi}" wrist_1_upper_limit="${pi}"
         wrist_2_lower_limit="${-pi}" wrist_2_upper_limit="${pi}"
         wrist_3_lower_limit="${-pi}" wrist_3_upper_limit="${pi}"
/>

  <link name="world" />

  <joint name="world_joint" type="fixed">
    <parent link="world" />
    <child link = "base_link" />
    <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
  </joint>

</robot>

Hello all, I need a structure for my project.

The aim is that a 3D camera tells a UR10 the location of an object (coordinates), then it moves its arm to the object and performs a circular path around it. During this activity it uses another stereo camera which is installed at the end of its arm to scan the objectl to generate a more detailed 3D model. At first I have to get it running in Gazebo and then using a real UR10.

I am using Ubuntu 14.04 LTS, ROS Indigo and Gazebo 2. Up to now I managed it to run the UR10 in Gazebo and control it using the Joint Trajectory Controler plugin for rqt_gui.

Next Step: I think I do need a motion planning package to tell the robot that it should move its arm from one position(x0,y0,z0) to the other (x1,y1,z1-> which is provided from a Kinect, but that is just gimmick if I have enough time)... Moreover it should of course prevent collision. What kind of package whould you recommend? Movit? How would you structure this project? Could you tell me more about the details?

I read a lot of the basics of ROS, Gazebo and ros_control, but in this case I need practical knowledge...

Thank you in advance & kind regards