README.md

Lego Spike Description

This package contains description files for the Lego Spike and Mindstorms Robot Inventor sets. Not all Lego parts have descriptions, but sensors and motors do.

Motors are configured to use continuous joints that rotate around the Z axis.

Distance and Color sensors have their sensing apparatus pointed along the positive X axis.

Usage

You must include the lego_materials.urdf.xacro file in addition to any specific components your robot needs. For convenience, lego_dimensions.urdf.xacro contains additional properties to help align URDF components with Lego's standard plate & stud dimensions. The origins of all sensors and motors are set such that they will align with each other in XYZ offsets of ${lego_stud_spacing} multiplied by increments of 0.5. For example, the following will move the origin along the X axis by 3 studs, the Y axis by -1 stud, and the Z axis by 1.5 studs:

<origin xyz="${lego_stud_spacing * 3} -${lego_stud_spacing} ${lego_stud_spacing * 1.5}" />

For more complete examples, showing rotations and adding multiple components see basic_lego_robot.urdf.xacro and/or simple_arm.urdf.xacro.

You can use Stud.io to design a complete lego model and export some/all of it as a Collada mesh (.DAE) and import that mesh into your URDF:

<link name="custom_lego_model">
  <visual>
    <geometry>
      <!--
        Make sure your exported DAE is included in a package in a sourced workspace.
      -->
      <mesh filename="package://my_lego_design/meshes/my_lego_model.dae" scale="0.001 0.001 0.001" />

      <!--
        Adjust the XYZ and RPY offset as needed to align your model
      -->
      <origin xyz="..." rpy="..." />
    </geometry>
    <
  </visual>
</link>