A PickPlace tutorial

[v4hn]

The MoveIt task constructor is meant to replace the pick place pipeline eventually, but the current pipeline should still be documented in a tutorial.
The replacement might even use the same interfaces as a drop-in replacement.

The only documentation we have for this at the moment is a single C++ file without comments that works with the PR2... which recently got replaced by panda throughout this repository..
This is not useful, especially because it is non-trivial to set working values for all parameters.

[Ridhwanluthra]

The approach given in the file seems to be a hard-coded implementation. is that correct?
if so, maybe moveit_grasps can be used for designing pick place tutorial?

[v4hn]

Yes it is hard-coded because we know it works (or worked). :) At times, it can be hard enough to find *one* valid Grasp definition. I agree though that a grasp-generator-based implementation would be much better. Feel free to work on this, but I would still recommend to get one hard-coded grasp to work on a hard-coded object before that.

[Ridhwanluthra]

I believe to build this tutorial we would need to setup gazebo as without that it's probably nothing different than the basic move group interface tutorial.

[Ridhwanluthra]

@mlautman @feroze

[mlautman]

I think Gazebo integration would be a great incredible tutorial on it's own. Adding gazebo integration to another tutorial would add complexity that deviates from the model of the tutorials which is, teach the user one thing at a time.

[davetcoleman]

We do have a GSoC student working on Gazebo integration fyi.

[Ridhwanluthra]

PR

[DebasmitaGhose]

I have been trying to use this tutorial to implement a pick and place task for a custom robot. Can you please explain how are the values for the following variables assigned?

'grasps[0].grasp_pose.pose.position.x = 0.415;
grasps[0].grasp_pose.pose.position.y = 0;
grasps[0].grasp_pose.pose.position.z = 0.5;'

I am attempting grasp by using two hands and I have obtained the position of the end effectors in the frame of the robot. Which of these values should I be using?
rosrun tf tf_echo base_footprint lh_palm
At time 1532437665.651

• Translation: [0.727, 0.346, 1.017]
• Rotation: in Quaternion [-0.103, 0.640, -0.253, 0.718]
  in RPY (radian) [-1.247, 1.050, -1.466]
  in RPY (degree) [-71.426, 60.170, -83.993]

rosrun tf tf_echo base_footprint rh_palm
At time 1532437942.251

• Translation: [0.729, -0.285, 1.004]
• Rotation: in Quaternion [-0.175, 0.612, -0.074, 0.768]
  in RPY (radian) [-1.085, 1.152, -0.939]
  in RPY (degree) [-62.179, 66.005, -53.797]

[Ridhwanluthra]

Right above these lines in the comments, it is mentioned how these values are set. check here
I don't think there is a direct function that you can call for a 2 hand grasp. maybe wait for someone else to comment on this.

[DebasmitaGhose]

The comments say
// Setting grasp pose
// ++++++++++++++++++++++
// This is the pose of panda_link8. |br|
// From panda_link8 to the palm of the eef the distance is 0.058, the cube starts 0.01 before 5.0 (half of the length
// of the cube). |br|
// Therefore, the position for panda_link8 = 5 - (length of cube/2 - distance b/w panda_link8 and palm of eef - some
// extra padding)

But I am still unable to understand how the values of position.x, position.y and position.z are computed. It would be helpful if you could give the numerical values of the length of the cube, distance b/w panda_link8 and palm of eef and some extra padding. Also, what do you mean by "the cube starts 0.01 before 5.0 (half of the length"

[felixvd]

The cube is defined right in the code, you just have to read it. You also asked about this in at least three different places, which is not very nice. Again: You should use ROS answers and probably spend more time working this out yourself.

[Ridhwanluthra]

@v4hn we can close this issue

[mlautman]

Thanks for your work on the Pick and Place Tutorial @Ridhwanluthra!