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Hi.

I created this launch ROS package to spawn at least a working version of Cassie robot. The only thing remaining is to calibrate the PIDs and the joint limits.

I had to make some modifications to the original cassie.xacro in cassie_description package because it was only for RVIZ purposes, not useful for Gazebo simulation. There fore you have to add collisions, masses some inertias. You have to also add the Gazebo Physics elements like mu,kp or the material. I had also to correct some elements of the transimissions that weren't quite right in the xacro at least.

As I said the solution is just to have it in Gazebo, because the PID calibration is loads of work and I dont have access to the real robot to compare the fidelity of the performance and speed. Thats work you will have to do.

Example:

<xacro:macro name="vectorNav">
<link name="vectorNav">
  <inertial>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <mass value="0.01" />
        <inertia ixx="1.66666666667e-07" ixy="0.0" ixz="0.0" iyy="1.66666666667e-07" iyz="0.0" izz="1.66666666667e-07"/>
    </inertial>
    <collision>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <geometry>
            <box size="0.01 0.01 0.01"/>
        </geometry>
    </collision>
    <visual>
        <origin rpy="0.0 0 0" xyz="0 0 0"/>
        <geometry>
            <box size="0.1 0.1 0.1"/>
        </geometry>
    </visual>
</link>

  <gazebo reference="vectorNav">
<kp>100000000.0</kp>
<kd>10.0</kd>
<mu1>0.1</mu1>
<mu2>0.1</mu2>
<fdir1>1 0 0</fdir1>
<maxVel>10.0</maxVel>
<minDepth>0.0005</minDepth>
<material>Gazebo/Green</material>

</gazebo> </xacro:macro>

Because ROS Anwsers doesnt allow me to upload non image files I'll have to give you the git where I uploaded all the code. Here you have the corrected xacro ready for moving it and all the code related to it in a convenient git: Git with XACRO and spawn and control

I have also created a ROSJect with all the project ready to go.

I've also created a tiny video to explain other details of the solution

Hope it helped