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Make a kinematic only model [closed]

asked 2016-06-17 10:40:41 -0600

Brosseau.F gravatar image

Hello everybody,

I have a robot model written in urdf and I want to make it move with a linear/angular speed command. So I have modified the planar_move plugin. I also had to make some links (not close to the ground) kinematic to avoid bad orientation in turn. But I still have a small bias in the trajectory following (which works fine with the diff_drive plugin).

I tried to disable gravity, set constraint solver iterations to 0, set all the links to kinematic. But when the robot receives an angular speed (take a turn), all the links falls apart.

Some possibilities :

  • Maybe the little bias can be corrected with follower's parameters (but I don't want to change them to test that specific version)

  • I am probably making some mistakes in using kinematic. I saw some posts about it but no answer. What is the steps to follow in order to use a kinematic only simulation ?

Thanks in advance.

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Closed for the following reason the question is answered, right answer was accepted by Brosseau.F
close date 2017-12-05 04:05:26.399051

1 Answer

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answered 2016-10-21 01:42:27 -0600

Brosseau.F gravatar image

updated 2017-12-05 04:04:39 -0600

Workaround: I made a plugin to apply speed to the base link of my robot.

This plugin will also set links (which are not parents on a joint) with no friction.

And it's working pretty nice.

Update :

This plugin was working with a model with unrealistic inertial matrix. When I tried it on a more realistic model a bias between the wanted angular speed and the actual one appeared.

As I said here (http://answers.gazebosim.org/question/17842/car-with-front-wheel-drive/), the solution is to switch the root link of the model to be kinematic (SetKinematic method). And then you can apply the wanted speed with SetLinearVel and SetAngularVel.

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Asked: 2016-06-17 10:40:41 -0600

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Last updated: Dec 05