Implement dofs, get / set joint control mode in Ignition Gazebo, refactor PID #104

diegoferigo · 2019-12-17T15:27:03Z

This PR adds the following capabilities to robots simulated in Ignition Gazebo:

Gather the number of DoFs
Set and get the control mode
Refactor PID support based on the new control mode selection

Fixes partially #65

to take into account the new capability to set the JointControlMode

The checkout action requires git > 2.18 to clone the repo in such a way to be compatible with setuptools-scm

traversaro · 2019-12-18T08:41:35Z

ignition/include/gympp/gazebo/IgnitionRobot.h

@@ -71,6 +74,8 @@ class gympp::gazebo::IgnitionRobot : public gympp::Robot

    bool setJointPosition(const JointName& jointName, const double jointPosition) override;
    bool setJointVelocity(const JointName& jointName, const double jointVelocity) override;
+    bool setJointControlMode(const JointName& jointName,
+                             const JointControlMode controlMode) override;


Not a big problem for the simulation runtimes, but for real robot runtimes it may be useful to be able to set also a first reference when you switch control mode. If there is the possibility of setting the joint position setpoints synchronously with the joint control mode, then there is no problem.

Excellent catch @traversaro. Right now is not possible to set the new reference synchronously (nor before changing control mode).

I see two solutions:

Make this a warning to allow users to set a reference before changing control mode:

gym-ignition/ignition/src/IgnitionRobot.cpp

Lines 483 to 487 in 551bd20

if (jointControlMode(jointName) != JointControlMode::Position) {

gymppError << "Cannot set the position target of joint '" << jointName

<< "' not controlled in Position" << std::endl;

return false;

}

Get the current joint positions before switching to Position mode and use them as a reference. In this way, if there's a small delay between the switch of the control mode and the setting of the first reference, the PIDs are already in working state.

Do you have any comment on these two, or a third preferable option?

Get the current joint positions before switching to Position mode and use them as a reference. In this way, if there's a small delay between the switch of the control mode and the setting of the first reference, the PIDs are already in working state.

In some cases, this is not going to work (for example, if you do that on a KUKA robot with RSI, the controller will fault due to the difference between the current reference and the current position, that are different due to static error).

Do you have any comment on these two, or a third preferable option?

To be honest, I am not enthusiastic of either solution (mainly because it is not clear for the user) for me, it is ok to just take note of this problem, and understand how to solve it in the future.

In some cases, this is not going to work (for example, if you do that on a KUKA robot with RSI, the controller will fault due to the difference between the current reference and the current position, that are different due to static error).

I didn't get something. How could the user provide a reference more precise than the current state read by sensors? In any case there will be a mismatch, right?

Opened a new issue to track this #107

I didn't get something. How could the user provide a reference more precise than the current state read by sensors? In any case there will be a mismatch, right?

We can discuss f2f, but basically in general the reference is different from the measured one if there is static error. If the static error is not negligiible, switching the reference from the old reference to the new reference creates a discontinuity.

traversaro · 2019-12-18T08:43:44Z

ignition/src/IgnitionRobot.cpp

@@ -333,6 +325,11 @@ bool IgnitionRobot::valid() const
    return true;
 }

+size_t IgnitionRobot::dofs() const
+{
+    return jointNames().size();


Just to know, are we tracking somewhere that the joint contained in jointNames has 1 and only 1 DOFs?

There are a lot of asserts in the code, not here specifically. I think we're well covered, but we should document (yet another thing to remember) that we only support 1 DoF joints.

(yet another thing to remember)

Yet another thing for which to open issues. : )

I converted an old issue to collect all these links to TODO(cument) stuff #37

traversaro

Small curiosity, why you need to update git?

diegoferigo · 2019-12-18T10:09:07Z

Small curiosity, why you need to update git?

I am still puzzled to be honest. Have a look at this log:

Working directory is '/__w/gym-ignition/gym-ignition'
/usr/bin/git version
git version 2.17.1
Deleting the contents of '/__w/gym-ignition/gym-ignition'
The repository will be downloaded using the GitHub REST API
To create a local Git repository instead, add Git 2.18 or higher to the PATH
Downloading the archive
Writing archive to disk
Extracting the archive
/bin/tar xz -C /__w/gym-ignition/gym-ignition/e090103a-f92c-498f-8f07-a099e700ab8b -f /__w/gym-ignition/gym-ignition/e090103a-f92c-498f-8f07-a099e700ab8b.tar.gz
Resolved version robotology-gym-ignition-2a4ad9f

It downloads the tarball, instead of creating a local git repository. For the python versioning we use setuptools-scm that, by reading the git history, creates a PEP440 compliant release. If there's no git repo, it fails to get the version:

Traceback (most recent call last):
File "setup.py", line 166, in
'./**/*.config',
File "/venv/lib/python3.6/site-packages/setuptools/init.py", line 145, in setup
return distutils.core.setup(**attrs)
File "/usr/lib/python3.6/distutils/core.py", line 108, in setup
_setup_distribution = dist = klass(attrs)
File "/venv/lib/python3.6/site-packages/setuptools/dist.py", line 448, in init
k: v for k, v in attrs.items()
File "/usr/lib/python3.6/distutils/dist.py", line 281, in init
self.finalize_options()
File "/venv/lib/python3.6/site-packages/setuptools/dist.py", line 740, in finalize_options
ep.load()(self)
File "/venv/lib/python3.6/site-packages/setuptools/dist.py", line 747, in _finalize_setup_keywords
ep.load()(self, ep.name, value)
File "/__w/gym-ignition/gym-ignition/.eggs/setuptools_scm-3.3.3-py3.6.egg/setuptools_scm/integration.py", line 17, in version_keyword
dist.metadata.version = get_version(**value)
File "/__w/gym-ignition/gym-ignition/.eggs/setuptools_scm-3.3.3-py3.6.egg/setuptools_scm/init.py", line 150, in get_version
parsed_version = _do_parse(config)
File "/__w/gym-ignition/gym-ignition/.eggs/setuptools_scm-3.3.3-py3.6.egg/setuptools_scm/init.py", line 113, in _do_parse
"use git+https://github.com/user/proj.git#egg=proj" % config.absolute_root

diegoferigo added complexity::medium pr::status::feedback component::gympp component::ignition component::gym_ignition component::tests labels Dec 17, 2019

diegoferigo requested a review from traversaro December 17, 2019 15:27

diegoferigo self-assigned this Dec 17, 2019

diegoferigo force-pushed the feature/controlmode_and_dofs branch 3 times, most recently from 10c6d4b to cc46f76 Compare December 17, 2019 15:48

diegoferigo mentioned this pull request Dec 17, 2019

Implement joint limits and initial joint position for Gazebo Robot #105

Merged

diegoferigo added 7 commits December 17, 2019 17:14

Add dofs and joint control mode support to C++ Robot classes

c540b8f

Implement set and get joint control mode for GazeboRobot

8d0fd6a

Refactor PID support of IgnitionRobot

147ae7d

to take into account the new capability to set the JointControlMode

Return a PID Python object from a gazebo robot

8d0936b

Add utils.py file for python tests

5217320

Fix and refactor test_rates

a7df5e2

Fix GHA

551bd20

The checkout action requires git > 2.18 to clone the repo in such a way to be compatible with setuptools-scm

diegoferigo force-pushed the feature/controlmode_and_dofs branch 2 times, most recently from 8dcba75 to 551bd20 Compare December 17, 2019 17:17

traversaro reviewed Dec 18, 2019

View reviewed changes

traversaro approved these changes Dec 18, 2019

View reviewed changes

This was referenced Dec 18, 2019

Improve Gazebo robot performance #106

Merged

How to handle references when switching to Position control mode #107

Closed

diegoferigo merged commit c9de481 into robotology:devel Dec 19, 2019

diegoferigo deleted the feature/controlmode_and_dofs branch December 19, 2019 14:11

diegoferigo removed the pr::status::feedback label Dec 19, 2019

diegoferigo added the pr::resolution::merged label Dec 19, 2019

diegoferigo mentioned this pull request Dec 20, 2019

Clone the entire git history before pushing to PyPI #115

Merged

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Implement dofs, get / set joint control mode in Ignition Gazebo, refactor PID #104

Implement dofs, get / set joint control mode in Ignition Gazebo, refactor PID #104

diegoferigo commented Dec 17, 2019 •

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diegoferigo commented Dec 18, 2019

	if (jointControlMode(jointName) != JointControlMode::Position) {
	gymppError << "Cannot set the position target of joint '" << jointName
	<< "' not controlled in Position" << std::endl;
	return false;
	}

Implement dofs, get / set joint control mode in Ignition Gazebo, refactor PID #104

Implement dofs, get / set joint control mode in Ignition Gazebo, refactor PID #104

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diegoferigo commented Dec 17, 2019 • edited Loading

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diegoferigo commented Dec 18, 2019

diegoferigo commented Dec 17, 2019 •

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