If it were constrained by an extra armature, it seems it could be used as a constant velocity joint. But again it may be limited by torque loading... However I wonder if that could be worked from the other direction by using a CV-joint design that handles torque well as a robotic armature if it's not constrained like it would be on a vehicle drive line?

@@pauljs75 I liked the counter idea, its an idea worth exploring.

could someone explain this but for dummys? (me)

@@keixsy The design allows angles with lots of stress against specific joints. I.E. too many hard materials to flex and distribute the stress accross the entire structure.

@@pauljs75 look up the Thompson Coupling from Australia.

Add fingers in the next update

Also have a look at Mark Rosheim's Omni Wrist 3 mechanism.

@@dm5rkt Thanks! I just uploaded the concept I worked up. It moves in 3DOF, but would require linear actuation/artificial muscles to control. Not sure how practical. kzfaq.info/get/bejne/pbVzY6mp0rOYh3U.html . If you have seen my concept worked out further somewhere, let me know. I am not trying to be original, lol. Just want a compact solution for a "shoulder" joint. Of course my joint suffers from multiple positional limitations.

True, but design and printing this in several iterations with a single printer takes weeks if not months. But of course, that is part of the fun too

@@juliusfucik4011 yes very true. It's the design and CAD skills that matter. I do everything in open source OPENSCAD as I refuse to commit my designs to rent software.

Then mount it on tracks with a FLIR camera and let it roam around the streets at 3am .

You talk about harmonic drive? ;)

Thank you a lot!

Hello, my favourite cyborg. 😄

I asked the same question.

Ditto on that. CV joints and "virtual sphere rolling joints" solve the same problem, just for different applications. And given the variation in existing CV joints, modifying one of those may suit this purpose in a more robust fashion.

In theory you only need two motors per joint, in practical application you need three for holding strength. There's also reasons why tentacle-like arms do not approach their design like this, but rather use air bladders or wire actuators that have a larger motor in the base, with a more simplistic design that uses a flexible non-compressible spine between the actuation discs; not to mention higher arm rigidity and less complexity in these models. Though the alternate design does require three actuators, or four depending on design, due to actuation not being linked to the spine itself as it is in this model. The older iterations of the LIMS2 AMBIDEX wrist used a similar model to the alternative, having actuation be separated from the spine via wire actuators, though they used a mechanical spine of the same design as the segments shown here; the key point here is that the spine is not directly linked to the actuators. This design realistically works for only one to two segments do to its downfalls, whereas the more optimal design can go for many more segments. I have a feeling, due to the downfalls of this design, that this project would become a sunken cost fallacy even for the best designers, there's just no good way to optimize all the problems, whereas an alternative provides less issues from the start.

@@xaytana I agree with your point. Another design that can be an alternative for a quaternion joint used here is an Omni Wrist by Ross Hime Designs Inc.

I was thinking the same thing, and drive them using cables (like a Dremel flex shaft) so all the motors are in the base. That will also cut down the weight of stage 2 and 3 drastically.

It will help greatly. The amount of torque from extending the mass is large.

Yeah he actually missed in his explanation that you can rotate+translate Z by rotating all servos the same direction. So the 3rd DOF is not something a traditional roboticist considers a DOF since its a mix of two DOFs. The 3 motors do all contribute their power to motion so having a 3rd one is not inefficient even if you constrain the calculations to not rotate the platform