"... and no one shall work for money, and no one shall work for fame; But each for the joy of the working, and each, in his separate star, shall draw the thing as he sees it, for the god of things as they are"

-Kipling

 

FPath_Ex006: The Pantograph

Background

FPath is a project to explore the possibilities of the Feynman Path to Nanotechnology. Essentially this means using tools to make small tools which then make smaller tools. See the main FPath Project page for more details.

This experiment demonstrates the effectiveness of closed loop error correction to make inherently poor quality hardware driven at larger scales produce accurate output at a smaller scale.

The Goal

The target goal of this experiment is to:

Demonstrate that closed loop control is a viable error reduction option when having large machines make smaller machines which then make smaller machines.

FPath Ex_006 Pantograph Example

This experiment is intended to verify a hypothesis which which will be useful in future Feynman path experiments. If the errors in the path of a tool head can be removed then the it will be much easier to have larger tools construct smaller tools. This is important because as machines make smaller machines, the effects of errors compound.

Achieving the Goal

This experiment made no changes to the experimental infrastructure and the only hardware addition was the construction of a pantograph device. Minor changes were made to the Walnut software. The starting point for this experiment is Walnut Server/Client version 00.02.07 and the changes made have been released as version 00.02.08.

Below is a specific list of the steps involved in reaching the goal. All of these steps are discussed in considerably more detail in the video which documents this experiment.

  1. Construct a simple, not especially accurate, pantograph device.
  2. Implement a recording mechanism so the movements on the micro end of the pantograph can be tracked.
  3. Use Stigmergic Path Following (see FPath_Ex004) with control applied to the macro end to move a red marker point around a circular path and observe the result of the movement on the micro end. The output of this step forms the "before" result.
  4. Change the point of control and use Stigmergic Path Following with control applied to the micro end to move a red marker point around a circular path and observe the result.
  5. Compare the two results and determine if closed loop control is an effective way of removing errors derived from inaccurate hardware driven from larger scales operating at smaller scales.

The Result

The experiment was successful. Actually, the results of the closed loop control on the movements of the micro end exceeded expectations and resulted in near perfect circles being recorded by the pantograph recording mechanism.

FPath Ex_006 Pantograph Macro End Example FPath Ex_006 Pantograph Macro End Example

The two images above demonstrate the path taken by the micro end of the pantograph. The image on the left shows the path (it is supposed to be a circle) when the pantograph was controlled on the macro end. The image on the right shows the path taken by the micro end when the control was applied to the micro end. The following video provides much more documentation of this experiment.

Video of a pantograph following circular paths and the effect of closed loop control on those operations.

This experiment was also discussed in a post on the RepRap Blog: The Pantograph

This experiment is now complete. The Walnut software associated with this experiment can be found under Commit ID: 6a96848 on the GitHub repo.

The Future

This project will probably not pursue pantographs further, they are hard to work with and are regarded as something of a dead end. Probably flexures, such as are used by the ongoing RepRap Micron project, are a better design choice. However, in this case, the inaccuracy has proved to be beneficial - since it enabled visual confirmation of the experiments central hypothesis:

Acknowledgments

Interestingly, both Heinlein and Feynman proposed using pantographs to have large machines make smaller machines. One reason the pantograph was chosen as a "first device" when "going downscale" on the Feynman Path is to acknowledge their ideas - a kind of homage if you will.

License

The intellectual property rights to all new and/or original ideas and technologies documented under the FPath project and sub-projects are claimed in full by the author and are immediately released into the public domain under the terms of the MIT License. Any ideas, techniques, processes or methods of work documented in the FPath project and sub-projects must be considered to be prior art and must be cited in any patent applications.

The contents of the FPath project and sub-projects are provided "as is" without any warranty of any kind and without any claim to accuracy. Please be aware that the information provided may be out-of-date, incomplete, erroneous or simply unsuitable for your purposes. Any use you make of the information is entirely at your discretion and any consequences of that use are entirely your responsibility.