jalfonso's profile - activity

I get same message "No Oculus device found!" with Oculus Rift DK2 , Ubuntu 12.04 and ROS Hydro.

Hello arennuit.

Question 1: Would I be able to reuse the same geometric and dynamic parameters and gains in the simulation and get a stable simulation with a behaviour in simulation comparable to the real life behaviour?

In the Community Forum 2014 ROS-Industrial, people COMAU (manufacturer of robots) showed GAZEBO model of one of his robot. The model runs same algorithms and parameters that control real robot, so you can reproduce the behavior of the real robot in the gazebo.

From my experience developing controllers and simulation models for the automotive sector, if you have a good model, you can use the same PID in the real world as a starting point. This is the base of Hardware In the Loop (HIL) testing.

Question 2: If the behaviours are different are they totally different and unrelated, or are the gains / parameters from the real world a good start to tweak the gains / parameters of the simulated world?

If behaviours are different, this point the model is not correlated with the real plant. So the values of gains will not correlate. This could apply to UR5 because we do not have a model of the controlers of the robot and we use standar PID from ROS. For sure, the controller of the real UR5 is better than PID.

If you find information on the control algorithms for robot motors, I offer to colaborate with you to model them in GAZEBO.

Question 3: I know that gazebo uses ODE as its default engine, would the answer be the same with bullet or another engine? I don´t know.

I cant explain more because I only can write Solution and a few words in Comments. And I dont want modify the original answer. :(

In ur_gazebo/controller/arm_controller_ur5.yam, Change parameters of all controllers to p: 10000.0, i: 50.0, d: 500.0, i_clamp: 0.0, i_clamp_min: -100.0, i_clamp_max: 100.0

Till end of weekend I will not have acces to my PC. I will chech your repo on monday. ;) jalfonso100

Check /joint_states topic is only published by gazebo using: rostopic info /joint_states If there are two publishers, and you use demo.launch, then comment or remove <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher"> <rosparam param="/source_list">[/move_group/fake_controller_joint_states]</rosparam> </node> Enjoy a rviz graphics without weird positions of arm.

Another problem, is the arm apears in rviz in strange positions. Maybe is caused because you use demo.launch and a gazebo launch. First launch fake_controller . In order to avoid this situation, your launch file should include <arg name="fake_execution" value="false">

You can overlay the package with an older but functional version.

See my answer in this post link text

I got same error in Ubuntu 12.04 and groovy. The solution is to use an overlay with an older version that works, the version 3.5 of the groovy-devel branch in github.

This are the instructions to get the old version. I assume you had created and sourced an overlay.

In a terminal..

roscd

cd ../src

git clone https://github.com/RobotWebTools/rosb... -b groovy-devel

cd rosbridge_suite

git reset --hard da51ab060ec74d7c026bf3f1dbb2bde76d55d0b9

cd ../..

catkin_make

Yes, I will propose add the changes to UR5 package maintainers. Meanwhile, you can use the above values​​.

Hi b3l33 The gains of the controller and the inertia of the model have default values. This cause the the arm has a lot of inertia and the controller is very slow and underdamped. The origin of the oscilations is the gravity, acting as a perturbation on the system. Other efect is a very large position error. When the arm stops, the hand is very down the goal state. You can see it in rviz.

I want to develope a best modell next week, but now you can use the following;

(This values are tested for hydro-dev branch of ros-industrial/universal_robot package.) In order to improve the behaviour, you should increase the gain of the controller, reduce the inertia of the links and increase the damping in the joins. You can change all p gain from 1.000 to 10.000 in the file,

ur_gazebo/controller/arm_controller_ur5.yam

shoulder_pan_joint: {p: 10000.0, i: 0.0, d: 0.0, i_clamp: 0.0, i_clamp_min: 0.0, i_clamp_max: 0.0}
shoulder_lift_joint: {p: 10000.0, i: 0.0, d: 0.0, i_clamp: 0.0, i_clamp_min: 0.0, i_clamp_max: 0.0}
elbow_joint: {p: 10000.0, i: 0.0, d: 0.0, i_clamp: 0.0, i_clamp_min: 0.0, i_clamp_max: 0.0}

Reduce inertia in all links to inertia to ixx="0.002" ixy="0.0" ixz="0.0" iyy="0.02" iyz="0.0" izz="0.002" in files

ur_description/ur5_joint_limited.urdf.xacro and ur_description/ur5_joint_limited.urdf.xacro

  <inertia ixx="0.002" ixy="0.0" ixz="0.0" iyy="0.02" iyz="0.0" izz="0.002"/>

And increase the damping in all joints to 0.5 in files

ur_description/ur5_joint_limited.urdf.xacro and ur_description/ur5_joint_limited.urdf.xacro

  <dynamics damping="0.5" friction="0.0"/>