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2017-04-30 16:39:26 -0500 commented question Two quadrotors in a single robot

I edited my question, thanks!

2017-04-30 16:39:13 -0500 edited question Two quadrotors in a single robot

Two quadrotors in a single robot Hello, I'd like to know how to I spawn two quadrotors inside a single robot in Gazebo
2017-04-30 10:40:50 -0500 asked a question Two quadrotors in a single robot

Two quadrotors in a single robot Hello, I'd like to know how to I spawn two quadrotors inside a single robot in Gazebo
2017-04-27 20:24:45 -0500 received badge ● Popular Question (source)
2017-04-19 22:33:33 -0500 asked a question Joint between different namespace/models

Joint between different namespace/models Hello, I'm working on a project where I have to connect two quads on a bar. On
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2017-04-17 21:34:56 -0500 asked a question Two quadrotors in one model

Hello, guys

I'm using hector_quadrotor library to develop a model where I have two quads connected physically.

https://ibb.co/efGc3v

On the image above there's an illustration of the problem with one quad.

My problem is that I need to add a second quad but also be able to fly both quads simultaneously.

I can launch two quads, but then I'm not able to add the bar that connects them. Using the .launch files there's no way to launch the quads and the bar, and also add a joint between them.

And also, there's the problem that the plugin that makes me able to fly them, is related to the model, not the quads individually. So I think I can't have a single model.

Anyone has any idea how to solve this?
2017-04-11 19:15:17 -0500 commented answer Ball joint in URDF

it worked! thank you very much for the explanation!
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2017-04-04 18:44:05 -0500 commented answer Ball joint in URDF

Hello, Jarvis, I just did what you said me to do. Thank you very much!
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2017-04-02 20:20:43 -0500 commented answer Ball joint in URDF

I thought about migrating to SDF but then I don't know how to make the plugins work nor how to spawn the model through ROS so I can control it with my xbox controller.
2017-04-02 20:19:14 -0500 commented answer Ball joint in URDF

Second DoF my bar disappears when I spawn the model in Gazebo. I've tried many combinations, creating more links between them, editing the bar model, but everytime I add a second DoF the bar doesn't show up in Gazebo. I can't find a way out to solve this problem.
2017-04-02 19:56:47 -0500 commented answer Ball joint in URDF

Center of the bar. If I switch roles (bar as parent and quad as child) my controller which I use to fly the quad will stop working. When I create a third link between them, I can make 1 DoF work. But for some reason, when I try to implement your suggestion, when I add the second DoF
2017-04-02 19:54:30 -0500 commented answer Ball joint in URDF

That's exactly what I meant. But it didn't work. I have a quadrotor (link1) and a bar with a ball in one end which I want to fix in the quad base with the spherical joint. If I try to create a continuous joint between them (quad as parent and bar as child) the quad rotates relative to the center of
2017-04-01 18:22:44 -0500 asked a question Ball joint in URDF

Hello, guys

I'd like to know how do I create a 3D ball joint using URDF.

I've tried some approaches like trying to create a dummy link, but I had no success.

In my project I have a quadrotor and a ball, I'd like to fix them, so the quad could roll, pitch and yaw on a fixed spot.

Any thoughts about that?

EDIT

I'll give more explanation about my problem.

In my project I want to develop a system for drones to share payload, and I want to avoid the problem of collision keeping them fixed in distance. To achieve that, I had the idea of using a bar, where they would be able to move freely. The image above ilustrates the ideia with one quad.

https://ibb.co/efGc3v

The problem that I'm facing right now is with the spherical joint between the quad and the ball. I managed to achieve 1 DoF at the moment. I'll copy here the 3 files that I'm using to make it work.

The bar model: 

<?xml version="1.0"?>

<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
    <xacro:property name="M_PI" value="3.1415926535897931"/>

    <xacro:macro name="barra_model" params="name parent *origin">
      <joint name="${name}_joint" type="fixed">
        <xacro:insert_block name="origin" />
        <parent link="${parent}"/>
        <child link="barra_baselink"/>
      </joint>

      <link name="barra_baselink">
        <visual>
          <geometry>
            <sphere radius="0.025"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0.9875 0 0.1125"/>
          <material name="white">
            <color rgba="1 1 1 1"/>
          </material>
        </visual>
        <inertial>
          <mass value="0.025" />
          <origin xyz="0.9875 0 0.1125" rpy="0 0 0" />
          <inertia ixx="5.8083e-4" ixy="0" ixz="0" iyy="3.0833e-5" iyz="0" izz="5.9083e-4" />
        </inertial>
    <collision>
          <geometry>
            <sphere radius="0.025"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0.9875 0 0.1125"/>
        </collision>
      </link>   

      <joint name="${name}_b2ebase_link" type="fixed">
      <parent link="barra_baselink"/>
          <child link="${name}_b2"/>
      </joint>

    <link name="${name}_b2">
        <visual>
          <geometry>
            <box size="0.025 0.025 0.10"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0.9875 0 0.075"/>
        </visual>
        <inertial>
          <mass value="0.050" />
          <origin xyz="0.9875 0 0.075" rpy="0 0 0" />
          <inertia ixx="5.8083e-4" ixy="0" ixz="0" iyy="3.0833e-5" iyz="0" izz="5.9083e-4" />
        </inertial>
    <collision>
          <geometry>
            <box size="0.05 0.05 0.20"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0.9875 0 0.075"/>
        </collision>
      </link>

      <joint name="${name}_b1eb2" type="fixed">
      <parent link="${name}_b2"/>
          <child link="${name}_bhor"/>
      </joint>

      <link name="${name}_bhor">
        <visual>
          <geometry>
            <box size="2.0 0.025 0.025"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0 0 0.0125"/>
        </visual>
        <inertial>
          <mass value="0.253" />
          <origin xyz="0 0 0" rpy="0 0 0.0125" />
          <inertia ixx="5.8083e-4" ixy="0" ixz="0" iyy="3.0833e-5" iyz="0" izz="5.9083e-4" />
        </inertial>
    <collision>
          <geometry>
            <box size="2.0 0.025 0.025"/>
          </geometry>
      <origin rpy="0 0 0" xyz="0 ...
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2017-03-23 20:26:52 -0500 asked a question Rosservice Hector_Quadrotor EnableMotors error

Hello,

I've been trying to controle the quadrotor that is simulated in Gazebo. Everything works fine, until I try to enable the motors. When I type rosservice list, I can see that /enable_motors is there. But this is happening:

rosservice call /enable_motors true ERROR: Unable to load type [hector_uav_msgs/EnableMotors]. Have you typed 'make' in [hector_uav_msgs]?

Does anyone have any idea on how to solve this? I had this error once, and then it stopped happening for some reason, but now it is back again.
2017-03-20 19:14:46 -0500 asked a question Two hector_quadrotor connected with a rod

Hello, guys

I'm trying to simulate a system where I have 2 (on the future more) quadrotors connect between them with a rod. But it is not an ordinary rod, which would make their motions limited. It's a physical link that fixes the distance between them, but doesn't limit their movements. I already have two quadrotors which I can control both simultaneously with a Taranis TX in gazebo+ROS. I'd like to know exactly how would I create a model, where I have 2 quadrotors that are fixed in distance from one another. I don't know if the best way to do it is by modeling the rod or just making an imaginary link. Either way, I'd need help with it.

Thanks in advance, Pedro
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