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Hi everyone!

Because I am planning to write my master thesis using Gazebo and ROS I have some basic questions concerning various topics.

The objective:
My goal is the simulation of a 5dof robot arm, its mobile plattform and some sensors (laser scanner, kinect camera etc.). Based on the existing ROS-modules of our real robot the plattform and the arm should be able to move. The simulation should be used as a hardware independent development environment for our real robot.

What do I have so far:
I got an sdf description file for the arm and its plattform. So far it looks fine. I only set the basic parameter (no physical parameters, no weights, no joint engines etc.). If I start the engine the robot arm falls to the ground observing the set collision (self collide) ranges, which I think is the expected behavior.

My Questions:
(I did some research before and maybe I overlooked something, but I just want to be sure about these things before I start the real work or maybe it becomes apparent that I made some wrong assumptions.)

  1. Do I need to provide all the physical / dynamic parameter of our robot?
    We don't need a completely perfect physical behavior in the first instance. The correct movement of the plattform and the arm would be sufficient. And I fear that we dont have all the parameters needed in our robot documentation. Maybe it is possible to limit the dynamic to a minimum.

  2. What is the best strategy to start the development and control of all related control- / bahavior- / ros-parts (to control the robot)?
    My plan was to work with a few sdf-files and then use a "main" gazebo-plugin for the rest. I know that I somehow have to use diffent gazebo-plugins for sensors and ros-components etc.. Everything needed would be called from that one plugin. Or what is the best way respectively your recommandation?

  3. How to best connect the existing ros-components / ros-logic of our real robot to the gazebo-simulation?
    Can I call them just through the "main" gazebo-plugin like in the question before?

  4. What is the best way to control the joints?
    Do I have to specify a pid-controller for every joint (problem with missing infos) or would it be enough / the better way to control the joints through the physics::JointController Classes / or similar?

  5. What about that realtime-controller everybody is talking?
    Do I need such a controller to control my robot in a reasonable way? Wouldn't the control just work over input for the plugins as there are ros-components for movement and grasping which only wait for e.g. target-coordinates.

Well I think thats it for the time being.

Thank you very much for your answers once before.

Kind regards

Christoph

Originally posted by Christoph on Gazebo Answers with karma: 141 on 2013-04-07

Post score: 0

Original comments

Comment by SL Remy on 2013-04-07:
What package is used to control the (real) arm?

Comment by Christoph on 2013-04-08:
Hardware specific packages (metralabs_ros) as the interface to the real hardware and arm_navigation (ros stack) for calculating the arm movement itself.

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I'll try to answer each of your questions in order.

  1. No, you don't need to specify all the physical properties. Gazebo will use default values in most situations.

  2. A good strategy is to look at some working code. I would recommend the DRCSim package: http://bitbucket.org/osrf/drcsim

  3. You can use ROS within a Gazebo plugin.

  4. Gazebo has a built-in PID class that you can use to control joints. You can also use more sophisticated ROS controllers.

  5. A real-time simulation is not mandatory to control a robot. Slower than real-time simulation just means that things more slow, your controller will be fine as long as you use simulation time.

Originally posted by nkoenig with karma: 7676 on 2013-04-10

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Original comments

Comment by skhan on 2013-04-11:
Christoph

Thanks for asking so brief question. I got the same problem.

Comment by skhan on 2013-04-11:
@nkoenig

How we can get that drcsim package? I installed drcsim using instructions and its running but how it can help us?

Comment by nkoenig on 2013-04-11:
Look at the source code. There is a gazebo plugin called AtlasPlugin.h that demonstrates how to use ROS inside a Gazebo plugin.

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