Open-Source Library of CAD Designs for 3D-printed, Underactuated Robotic Hands | Hacker News Reader

Open-Source Library of CAD Designs for 3D-printed, Underactuated Robotic Hands

eng.yale.edu

8 pointstoothpickguy6 comments

Underactuated robotics is a cool topic, but I hadn't heard of underactuated hands before.

"The released hand designs feature tendon-driven underactuated fingers. Underactuated hands have been shown to improve the generality of simple grippers by adaptively conforming to the surface of objects without the explicit need for sensors or complicated feedback systems. This design paradigm separates the actuation and finger elements, enabling a greater degree of customization."

"Based on the original SDM Hand, the Model T is the OpenHand Project's first released hand design, initially introduced at ICRA 2013. the four underactuated fingers are differentially coupled through a floating pulley tree, allowing for equal force output on all finger contacts."

Anybody here take this course? https://www.edx.org/course/underactuated-robotics-mitx-6-832... Is this ongoing?

The MIT underactuated robotics course actually deals with underactuated robotics in terms of dynamics. Our hands considers underactuation from a quasi-static perspective. The main take-away for our project/design is that the final configuration of the hand is determined not only by the actuator inputs, but also the fingers' interactions with the object and environment.

This makes me both very happy and very sad - happy because it's a brilliant thing, sad because it's in a proprietary format that requires expensive closed software to open and edit.

They do have STL files, which I understand are commonly used in 3D printing scenarios. We'll see if they decide to put up STEP and/or IGES files as well - that would be ideal. The Rhino 3dm format might also be a viable option, since openNURBS is available for reading/writing it and is under a very liberal license.

I will provide exported STEP files soon, alongside the STL files. I used Solidworks not only because it's the standard in our research lab, but also because I couldn't do what I wanted with any other CAD package. My source files are actually highly parametric, with extensive use of a set of global variables to help me adapt the designs for different printer settings and different system design constraints without having to rebuild the CAD every single time. The closest open-source solution I could find with similar functionality was OpenSCAD, but (imo) it's not mature enough to handle assemblies or more detailed models, and I'd bet that far fewer people have ever tried OpenSCAD than Solidworks.

If you can suggest an alternative open-source CAD package, not just file format, I'd be happy to look into it. Thanks for the interest!

The other two projects that leap to mind for open source CAD are FreeCAD and BRL-CAD, but I'm not sure either would meet your particular requirements. I'm pretty sure BRL-CAD doesn't offer the sort of parametrics you'd want (the closest thing would probably be writing a procedural generator, which usually means C/C++ or a scripting language). I'm less sure about FreeCAD - they use the OpenCASCADE engine - but if the other commercial systems didn't offer what you want I'd be surprised if FreeCAD had it (not impossible though - it might be worth asking the dev team if your workflow could be realized in FreeCAD.)

Providing the STEP and STL files should cover pretty much what the open source CAD world is prepared to handle - FreeCAD can import STEP and BRL-CAD is working on it, and most 3D printing applications I know of can work with STL just fine. Thank you for taking the trouble to make the extra formats available.

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