4 ms·

Aaed Musa blew my mind about 18 months ago with his capstan drive video: https://youtube.com/watch?v=MwIBTbumd1Q https://youtube.com/watch?v=MwIBTbumd1Q Eight

by hinkley 7mo ago

Aaed Musa blew my mind about 18 months ago with his capstan drive video: https://youtube.com/watch?v=MwIBTbumd1Q https://youtube.com/watch?v=MwIBTbumd1Q Eight months ago he built a quadrupedal robot that could step sideways using three of them per leg. I’m not going to link that, you’ll have to find it from his YouTube page because you should look around.

keeda 7mo ago
Thanks for this. I almost never have the patience for any videos, but this one hooked me and kept me engaged throughout. Worth it for that random "yo mama" joke alone.
- Joel_Mckay 7mo ago
  This channel about retrofitting industrial robotic arm control systems is quite practical. Could always run the playback at 1.25 speed for slow talkers/edits =3 https://www.youtube.com/@ExcessiveOverkill/videos https://www.youtube.com/@ExcessiveOverkill/videos
  - hinkley 7mo ago
    Jeremy Fielding is also good, but I think he must have gotten busy because he doesn’t post as much. https://youtube.com/@Jeremy_Fielding https://youtube.com/@Jeremy_Fielding If you pay attention to Smarter Every Day videos he’s occasionally in the background, which makes me suspect he’s still active but doing behind the scenes stuff and less in his garage.
num42 7mo ago
Sorry for going off topic. "Electric Motor Scaling Laws and Inertia in Robot Actuators" by Ben Katz who designed the MIT Mini Cheetah in 2018 is very well known in the legged robotics community. His master’s thesis on actuator design is also widely referenced. During the COVID period, some Chinese companies even sold variants of actuators inspired by the Mini Cheetah design. Aaed Musa has also mentioned in some of his videos that his actuator designs were inspired by the Mini Cheetah actuator. Yes, His capstan drive video is especially impressive. For example, in Aaed Musa’s video "I Built a Rubik's Cube Solving Robot" (https://www.youtube.com/watch?v=m0bMMALYMYk https://www.youtube.com/watch?v=m0bMMALYMYk), he states in the description that the design was inspired by Ben Katz’s work. Ben Katz master thesis, is worth reading: "A low cost modular actuator for dynamic robots" 2018 https://dspace.mit.edu/handle/1721.1/118671 https://dspace.mit.edu/handle/1721.1/118671 and also has a good post https://robot-daycare.com/posts/2019-12-16-the-mini-cheetah-robot/ https://robot-daycare.com/posts/2019-12-16-the-mini-cheetah-... And also, The Rubik's Contraption (2018), 297 points, the work done by same author https://news.ycombinator.com/item?id=16561049 https://news.ycombinator.com/item?id=16561049
- jcims 7mo ago
  I did a bit of a deep dive into motor control and actuators in building a two axis gimbal for tracking satellites with an RF antenna (with the eventual goal of building a mount for optical tracking). Ben's vids were kind of mind-blowing for me at that time. I couldn't believe some of the control that was possible with relatively pedestrian electronics. Aaed's vids do a wonderful job of making it accessible in an applied way. It's something I think a lot of the folks on HN would find interesting to tinker with. Nice mix of software and hardware that actually does work in physical reality. It also gives me a level of appreciation for the advances in humanoid robots that I don't think I would have had otherwise. (If you *do* get into it, I'd highly recommend getting into field oriented control with brushless motors and encoders. Small hobby servos are fun but they encapsulate a lot of the interesting parts and tend to have limited options available for things like the capstan vid linked above)
SAI_Peregrinus 7mo ago
I hate the phrase "zero backlash" that gets used right in the intro. Nothing has zero backlash. If it did, that would mean the material is incompressible & unstretchable: it would have an infinite speed of sound. You could implement FTL communication using zero-backlash actuators. Capstan drives have backlash because the rope stretches. It's very low if using a low-stretch rope, but nonzero.
- fusionadvocate 7mo ago
  What you are referring to is stiffness, which is different than backlash. Backlash, or play, is due to gaps.
  - SAI_Peregrinus 7mo ago
    Backlash & a lack of stiffness have the same effect, but the cause happens at different scales. Just because the gaps are in between the atoms of the dyneema doesn't mean there are no gaps! There's still play due to a lack of stiffness, just less of it. The positioning errors should be lower than the feedback resolution on the servo encoders, but they won't be zero.
    - vablings 7mo ago
      I disagree; backlash is unrelated to force. If you were to graph error over force for backlash it would be a straight line but for something like dyneema it would directly scale with force applied. In a driven system the dead zone is graphable and that deadzone time or area does not change based on velocity, A lack of rigidity in couplings, gears or belts IS affected by velocity
- vablings 7mo ago
  Backlash is specifically the slack between directional change. The forces you describe are proportional to force. Backlash is independent of force
  - hinkley 7mo ago

by hinkley 7mo ago

keeda 7mo ago

Thanks for this. I almost never have the patience for any videos, but this one hooked me and kept me engaged throughout. Worth it for that random "yo mama" joke alone.

Joel_Mckay 7mo ago
This channel about retrofitting industrial robotic arm control systems is quite practical. Could always run the playback at 1.25 speed for slow talkers/edits =3 https://www.youtube.com/@ExcessiveOverkill/videos https://www.youtube.com/@ExcessiveOverkill/videos
- hinkley 7mo ago
  Jeremy Fielding is also good, but I think he must have gotten busy because he doesn’t post as much. https://youtube.com/@Jeremy_Fielding https://youtube.com/@Jeremy_Fielding If you pay attention to Smarter Every Day videos he’s occasionally in the background, which makes me suspect he’s still active but doing behind the scenes stuff and less in his garage.

num42 7mo ago

Sorry for going off topic. "Electric Motor Scaling Laws and Inertia in Robot Actuators" by Ben Katz who designed the MIT Mini Cheetah in 2018 is very well known in the legged robotics community. His master’s thesis on actuator design is also widely referenced. During the COVID period, some Chinese companies even sold variants of actuators inspired by the Mini Cheetah design. Aaed Musa has also mentioned in some of his videos that his actuator designs were inspired by the Mini Cheetah actuator. Yes, His capstan drive video is especially impressive. For example, in Aaed Musa’s video "I Built a Rubik's Cube Solving Robot" (https://www.youtube.com/watch?v=m0bMMALYMYk https://www.youtube.com/watch?v=m0bMMALYMYk), he states in the description that the design was inspired by Ben Katz’s work. Ben Katz master thesis, is worth reading: "A low cost modular actuator for dynamic robots" 2018 https://dspace.mit.edu/handle/1721.1/118671 https://dspace.mit.edu/handle/1721.1/118671 and also has a good post https://robot-daycare.com/posts/2019-12-16-the-mini-cheetah-robot/ https://robot-daycare.com/posts/2019-12-16-the-mini-cheetah-... And also, The Rubik's Contraption (2018), 297 points, the work done by same author https://news.ycombinator.com/item?id=16561049 https://news.ycombinator.com/item?id=16561049

jcims 7mo ago
I did a bit of a deep dive into motor control and actuators in building a two axis gimbal for tracking satellites with an RF antenna (with the eventual goal of building a mount for optical tracking). Ben's vids were kind of mind-blowing for me at that time. I couldn't believe some of the control that was possible with relatively pedestrian electronics. Aaed's vids do a wonderful job of making it accessible in an applied way. It's something I think a lot of the folks on HN would find interesting to tinker with. Nice mix of software and hardware that actually does work in physical reality. It also gives me a level of appreciation for the advances in humanoid robots that I don't think I would have had otherwise. (If you *do* get into it, I'd highly recommend getting into field oriented control with brushless motors and encoders. Small hobby servos are fun but they encapsulate a lot of the interesting parts and tend to have limited options available for things like the capstan vid linked above)

SAI_Peregrinus 7mo ago

I hate the phrase "zero backlash" that gets used right in the intro. Nothing has zero backlash. If it did, that would mean the material is incompressible & unstretchable: it would have an infinite speed of sound. You could implement FTL communication using zero-backlash actuators. Capstan drives have backlash because the rope stretches. It's very low if using a low-stretch rope, but nonzero.

fusionadvocate 7mo ago
What you are referring to is stiffness, which is different than backlash. Backlash, or play, is due to gaps.
- SAI_Peregrinus 7mo ago
  Backlash & a lack of stiffness have the same effect, but the cause happens at different scales. Just because the gaps are in between the atoms of the dyneema doesn't mean there are no gaps! There's still play due to a lack of stiffness, just less of it. The positioning errors should be lower than the feedback resolution on the servo encoders, but they won't be zero.
  - vablings 7mo ago
    I disagree; backlash is unrelated to force. If you were to graph error over force for backlash it would be a straight line but for something like dyneema it would directly scale with force applied. In a driven system the dead zone is graphable and that deadzone time or area does not change based on velocity, A lack of rigidity in couplings, gears or belts IS affected by velocity
vablings 7mo ago
Backlash is specifically the slack between directional change. The forces you describe are proportional to force. Backlash is independent of force
- hinkley 7mo ago