Revert #255

[knorth55]

related to #245 and #255

In #245 and #255, they try to work PR2 on Gazebo in Indigo version and make this change.
However, this modification doesn't make sense, and it doesn't work on Kinetic and Melodic, which uses higher version Gazebo.
I revert the PR and I checked it's working on Kinetic Gazebo.

[knorth55]

I update to revert d5c8f47 and it works in Kinetic !

[k-okada]

LGTM, please backport to kinetic and also add a more detailed explanation.

[knorth55]

I add detailed explanation in this PR.

[knorth55]

@k-okada can you review this again?

[v4hn]

Hi @knorth55

However, this modification doesn't make sense, and it doesn't work on Kinetic and Melodic, which uses higher version Gazebo.

Please give more details in pull-requests.
"doesn't make sense".. Why?
"doesn't work on kinetic and melodic".. What do you observe there?

Any idea why this factor of 10 seemed necessary in indigo and "doesn't work" in kinetic?

@k-okada given that both the original and the new patch come from your lab, I will leave this to you to resolve.

[knorth55]

"doesn't make sense".. Why?

Originally, this parameter is set as 3141.6, which comes from PR2 hardware design.
Willow garage set this parameter at first (we can see it from git log), but some people change the parameter to 314.16 in #255.
They change this parameter from 3141.6 -> 314.16 to run PR2 gazebo indigo, but this parameter is defined from PR2 hardware, so 314.16 doesn't make sense.
However, PR2 gazebo in Indigo does not work (it is reported in #245) with this original correct parameter 3141.6, and they solved the problem by changing this parameter to 314.16.
This is my guess, but this problem is actually a bug in Gazebo, and it looks running correctly on Gazebo with the wrong parameter 314.16 somehow.

"doesn't work on kinetic and melodic".. What do you observe there?

However, when I tried to close PR2 gripper on PR2 Gazebo Kinetic, the gripper does not close.
We read git log, and this is caused the parameter difference between

pr2_common/pr2_description/urdf/gripper_v0/gripper.transmission.xacro

Line 41 in 7a59197

simulated_reduction="314.16" />

and

pr2_common/pr2_description/urdf/gripper_v0/gripper.gazebo.xacro

Line 170 in 6f96993

<thread_pitch>-3141.6</thread_pitch>

.
So I change the parameter back to correct one 314.16 -> 3141.6, and now PR2 gazebo on kinetic works.

[knorth55]

@v4hn I updated the comment to add more detailed information.
My point is that

• Original parameter 3141.6 is decided from PR2 hardware design, so it should not be modified.
  • Original commit: cfc824c
• however, the parameter is modified from 3141.6 -> 314.16 in [pr2_description] fix: gripper reduction 3141.6 -> 314.16 #255
• in Indigo PC, PR2 gazebo works correctly with this wrong parameter 314.16.
• But in Kinetic, PR2 gazebo does not work correctly with this wrong parameter 3141.6.
  • Grippers do not close in PR2 Gazebo
• This PR revert [pr2_description] fix: gripper reduction 3141.6 -> 314.16 #255 to correct the parameter 314.16 -> 3141.6, and PR2 Gazebo works (grippers close) in Kinetic PC.

[knorth55]

@v4hn kindly ping.