Moataz Elmasry's profile - activity

Hello everyone

I'm implementing a stair detection algorithm using kinect. My understanding is that in ros and openni the y and z of 3D points are reversed. so point.y indicates depth, and point.z indicates depth, while (0,0,1) is the normal to the ground plane

Now when I'm running plane/stair detection on some sample stairs, I have the feeling this is not the case, for example:

`Standing down and looking upstairs:
where Normal (x,y,z) is the angle between plane normal and (1,0,0), (0,0,1), (0,1,0), and center means the center point of the plane

Normal (x,y,z) to plane=8=(85.9741,5.20184,86.7113), center=(-486.011,110.283,1775.32, is vertical
Normal (x,y,z) to plane=17=(86.2233,6.65427,84.5293), center=(97.3194,177.953,1440.98, is vertical
Normal (x,y,z) to plane=21=(87.3236,16.1993,74.0353), center=(54.2511,277.825,1146.79, is vertical
Normal (x,y,z) to plane=22=(90.2841,87.4952,2.52085), center=(-26.3924,329.484,929.445, is horizontal
Normal (x,y,z) to plane=24=(87.1528,12.2501,78.0953), center=(-31.5048,393.672,855.474, is vertical
Normal (x,y,z) to plane=25=(89.4157,90.5968,179.165), center=(-21.418,422.656,675.315, is horizontal

since points are scanned from top left to bottom right, so planes with smaller id´s are scanned first, i.e. in the upper case they are the higher further plane.

Now for the case standing up the stairs and looking downwards, here are my planes:

Normal (x,y,z) to plane=67=(90.5932,89.6205,179.296), center=(-223.516,950.897,2188.82, is horizontal
Normal (x,y,z) to plane=85=(90.4772,93.7257,176.244), center=(70.3257,842.521,1605.57, is horizontal
Normal (x,y,z) to plane=86=(90.4431,94.3491,175.628), center=(32.0055,743.043,1304.14, is horizontal
Normal (x,y,z) to plane=88=(90.4187,78.5517,168.544), center=(20.4919,639.753,996.574, is horizontal
Normal (x,y,z) to plane=90=(90.0278,110.79,20.7901), center=(-1.77436,540.584,736.258

Again small plane id means further (but lower planes in this case) As you can see, the 3rd component of the center (z) starts large and goes smaller in both cases, while the (y) component in the first case is small and goes larger and vice versa in second case, so this tells me that this coordinate system is just a standard coordinate system with y indicates height and z indicates depth one more tip, calculating angle between plane normal and (0,0,1) yields almost 90 degrees for horizontal planes and 0 or 180 degrees for vertical planes, while using the normal (0,1,0) as ... (more)

Hello List

I'm a newbie to Gazebo and have been experimenting with it for the last couple of days. So now I have a small problem, I wrote a simple 4 wheels robot (attached to this email) which spawns perfectly in gazebo. Now whenever I apply a body wrench, I get the following warning in Gazebo "[ WARN] [1299848525.581625793, 11872.099000000]: ApplyBodyWrench: reference frame and reference_point not implemented yet, force is defined and applied at the body frame"

rosservice call gazebo/apply_body_wrench '{body_name: "car::left_front_wheel" , wrench: { force: { x: 0.1, y: 0, z: 0 } , torque: { x: 0.0, y: 0 , z: 0 } }, start_time: 10000000000, duration: 1000000000 }'

The car moves actually the way I want, but it I'd understande from that warning that the force is applied to the base_link and not to the wheel the way I want. Or did I miss something?

Thanks alot for the help Best regards Moataz

wheels_robot4.urdf

<?xml version="1.0" ?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from wheels_robot4.xacro            | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot name="wheels_robot" xmlns:body="http://playerstage.sourceforge.net/gazebo/xmlschema/#body" xmlns:geom="http://playerstage.sourceforge.net/gazebo/xmlschema/#geom" xmlns:joint="http://playerstage.sourceforge.net/gazebo/xmlschema/#joint" xmlns:model="http://playerstage.sourceforge.net/gazebo/xmlschema/#model" xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor" xmlns:visual="http://playerstage.sourceforge.net/gazebo/xmlschema/#visual" xmlns:xacro="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface">
  <link name="base_link">
    <inertial>
      <mass value="1"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    </inertial>
    <visual>
      <geometry>
        <box size="1 0.6 0.1"/>
      </geometry>
    </visual>
    <collision>
      <geometry>
        <box size="1 0.6 0.1"/>
      </geometry>
    </collision>
  </link>
  <link name="left_front_wheel">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
      <material name="Cyan1">
        <color rgba="0 1 1 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="0.1"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    </inertial>
  </link>
  <link name="right_front_wheel">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
      <material name="Cyan1">
        <color rgba="0 1 1 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="0.1"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    </inertial>
  </link>
  <link name="left_back_wheel">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
      <material name="Cyan1">
        <color rgba="0 1 1 1.0"/>
      </material>
    </visual>
    <collision>
      <geometry>
        <cylinder length="0.11" radius="0.096"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="0.1"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0 ...