[pick_place_demo.py] cannot grasp the cube about fetch_gazebo

[moriarty]

Thanks, how reproducible is this?

Does it fail every time? Or sometimes pass as mentioned in this issue #20

[umhan35]

I tried like 5 times, it was never successful. One thing is that I am using integrated GPU (Intel® HD Graphics 620).

Here is my environment setup:

Environment Setup

Make sure Ubuntu 18.04 and ROS Melodic are installed. We are using this version because it is also installed on the robot and it works.

(Currently only ROS Indigo is supported as Debian packages, but there are git branches for Ubuntu 18.04/ROS Melodic and both are installed on the onboard computer of the robot.)

Installing fetch_ros & fetch_gazebo from source

Install the dependencies for Fetch Robotics:

sudo apt-get update
sudo apt install ros-melodic-robot-controllers ros-melodic-costmap-2d ros-melodic-moveit ros-melodic-rgbd-launch

Create a catkin workspace: http://wiki.ros.org/catkin/Tutorials/create_a_workspace

In the carkin workspace src directory, run:

git clone https://github.com/fetchrobotics/fetch_ros.git
git clone https://github.com/fetchrobotics/fetch_gazebo.git

In your carkin workspace root directory, run

catkin_make

Test your installation in an empty world

roslaunch fetch_gazebo simulation.launch

Gazebo demo

Install dependencies:

sudo apt install ros-melodic-map-server ros-melodic-simple-grasping ros-melodic-amcl ros-melodic-move-base

demo:

roslaunch fetch_gazebo pickplace_playground.launch
roslaunch fetch_gazebo_demo pick_place_demo.launch

[umhan35]

I also made changes mentioned in PR #26.

[moriarty]

We have a new Intern: @ejichen who is working on updating our demos with the Fetch in Simulation and on the Real Robot.

She started this week and will work on a new cube picking demo.

I'll assign this to her to look into.

1. I've noticed in Gazebo9, the lighting is much more accurate than it was in the past. We may need to update our simulation world to increase the lighting to improve the ability to detect the cube.
2. There are a number of other tickets related to the control of the base/gripper/arm etc. I think we can consulate them all into one ticket to focus our efforts.

[ejichen]

Hi @umhan35,
I tried to reproduce the issue and the situation showed in the video might be similar to your problem.

On the first try, the Gazebo window shows that the robot flickered a little bit after it moved the arm (0:05 in the video). The movement shifted the robot, resulting in the mismatch of the robot frame and the planning scene frame (shows in the rviz window).

The second try didn't succeed because the previous movement made some changes to the position of the cube. However, if you let the simulation run for a while, you could see the pick and place demo succeed with the third try (since the script is a while loop of pick and place).

[moriarty]

@umhan35 I've made two URDF changes.

1. Quick Fix: #37 (comment)
2. Better Fix: #37 (comment)

@ejichen has been using 1. which is a quick fix, but I will make a PR with 2. which adds the caster wheels to the model

[moriarty]

Actually, I before committing the changes, I went to record before and after videos.

And surprisingly the fetch was able to grasp the cube, using the ccb5ad3 and the fetch-ros from debians https://github.com/fetchrobotics/fetch_ros/releases/tag/0.8.0.

https://youtu.be/izZZFZgtJYo

I didn't use fetch_ros from source- the versions from source upgraded the fetch_ikfast_plugin ZebraDevs/fetch_ros#107 to fix deprecation warnings with the next version of moveit.

[umhan35]

I'd say the behavior is not consistent. I am not sure if it is a Gazebo issue.

[moriarty]

The behaviour isn’t expected to be consistent, it’s running MoveIt! with random sampling based motion planners.

But, if we make the URDF changes to stablize the base (the real Robot is very stable and doesn‘t wiggle or tilt when moving the arm) then it should behave closer to the real thing. In #37, I’ve posted videos of Indigo & Kinetic and the inertia/CoM values visually look different- despite not being changed.