This is a video tutorial series exploring how to rig a full robot in Blender 2.8. One of the main features of this tutorial series (Part 4) is to create an IK FK Switch on the rig. This same technique can be applied to human and robotic characters.
See an overview of the series below, and watch the entire series here.
All of the assets are available for free from our Gumroad account, this includes files for each step of the process.