Why do I need to apply large force (10 kN) to move my robot?

asked 2021-10-14 20:38:58 -0500

I modeled my physical, simple diff-drive robot with two larger drive wheels and two casters. The robot total weight is around 30 kg. Body size is L=0.512 m, W=0.384 m , H=0.211 m

When I interact with the model (Apply Force/Torque) in Gazebo, I need to use very large forces to move it: 10 kN barely moves it, 100 kN pushes it around 1 m forward. The force feels completely disproportional.

Is there anything wrong with my model because this does not pass a smell test?

Appreciate any feedback.

The body inertial is as follows:

 <inertial>
  <mass value="30.0"/>
  <inertia ixx="0.7666624999999999" ixy="0.0" ixz="0.0" iyy="1.024" iyz="0.0" izz="0.47994250000000005"/>
</inertial>

The entire URDF:

<?xml version="1.0" ?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from travik.xacro                   | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot name="travik">
  <material name="black">
    <color rgba="0.0 0.0 0.0 1.0"/>
  </material>
  <material name="blue">
    <color rgba="0.0 0.0 0.8 1.0"/>
  </material>
  <material name="green">
    <color rgba="0.0 0.8 0.0 1.0"/>
  </material>
  <material name="grey">
    <color rgba="0.2 0.2 0.2 1.0"/>
  </material>
  <material name="orange">
    <color rgba="1.0 0.4235294117647059 0.0392156862745098 1.0"/>
  </material>
  <material name="brown">
    <color rgba="0.8705882352941177 0.8117647058823529 0.7647058823529411 1.0"/>
  </material>
  <material name="red">
    <color rgba="0.8 0.0 0.0 1.0"/>
  </material>
  <material name="white">
    <color rgba="1.0 1.0 1.0 1.0"/>
  </material>
  <!-- https://en.wikipedia.org/wiki/List_of_moments_of_inertia#List_of_3D_inertia_tensors -->
  <!-- prevent "The root base_link has an inertia specified in the URDF, but KDL" error -->
  <link name="base_footprint"/>
  <joint name="base_joint" type="fixed">
    <parent link="base_footprint"/>
    <child link="base_link"/>
    <origin rpy="0 0 0" xyz="0.0 0.0 0.010"/>
  </joint>
  <link name="base_link">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <box size="0.512 0.384 0.211"/>
      </geometry>
      <material name="green"/>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <box size="0.512 0.384 0.211"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="30.0"/>
      <inertia ixx="0.7666624999999999" ixy="0.0" ixz="0.0" iyy="1.024" iyz="0.0" izz="0.47994250000000005"/>
    </inertial>
  </link>
  <link name="left_front_wheel">
    <visual>
      <origin rpy="1.5707963267948966 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.083" radius="0.128"/>
      </geometry>
      <material name="black"/>
    </visual>
    <collision>
      <origin rpy="1.5707963267948966 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.083" radius="0.128"/>
      </geometry>
    </collision>
    <inertial>
      <origin rpy="1.5707963267948966 0 0" xyz="0 0 0"/>
      <mass value="3"/>
      <inertia ixx="0.01401025" ixy="0" ixz="0" iyy="0.01401025" iyz="0" izz="0.024576"/>
    </inertial>
  </link>
  <joint name="left_front_wheel_joint" type="continuous">
    <axis rpy="0 0 0" xyz="0 1 0"/>
    <parent link="base_link"/>
    <child link="left_front_wheel"/>
    <origin rpy="0 0 0" xyz="0.128 0.2495 -0.04149999999999998"/>
    <dynamics ...
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