The convergence of mechanics and electronics in robotics brings with it a lot of challenges. Thanks to 3D printing and low cost components, it’s possible to quickly and easily experiment with a variety of robotics mechanism for various use cases. [Paul Gould] has been doing exactly this, and is giving us a taste of ten designs he will be open sourcing in the near future. Video after the break.
Three of the designs are capstan mechanisms, with different motors and layouts, tested for [Paul]’s latest quadruped robot. Capstan mechanisms are a few centuries old, and were originally used on sailing ships to give the required mechanical advantage to tension large sails and hoist cargo.
Two of the mechanisms employ GUS Simpson Drives, which use a combination of belts and a rolling joint. These were inspired by the LIMS2-AMBIDEX developed at the University of Korea. The ever-popular cycloidal gearbox also makes and appearance in the form of a high torque dual disk linked, two stage, NEMA17 driven gearbox.
[Paul] also built a room sized skycam-like claw robot for his daughter, suspended by four ball chain strings reeled in by four brushless motors with ESP32 powered motor controllers. We are looking forward to having a close look at these designs when [Paul] releases them, and to see how his quadruped robot will turn out.
[Thanks TTN for the tip!]
Tensioned cables are underappreciated as an actuation system IMHO
Underappreciated in terms of ease of building. I used to work on washing machines. The Whirlpool compact washing machines once used tensioned cables for agitation. Not a good idea – these wore out quickly and ware practically unrepairable.
I think choosing the correct cables, termination and routing is very important. The braided fishing line is not a good choice. Next versions will have Dyneema cord or 49 strand 1mm Stainless wire.
Right. I have no doubt that a mechanism with appropriate cables could be used reliably in many designs. I may have overstated the case with the washing machine agitator example – that is a very heavy duty load, and possibly not all that well designed. As I recall, it used ~5 steel wire ropes pulling in each direction, about 3mm each, but there was a substantial shock load every time the agitator came to the end of its travel and had to reverse direction, about twice per second. Whirlpool ended up replacing that design with the same transmission they use in their full-size machines.
Hi Paul. I’m very impressed with your “Cycloidal Gearbox Single Stage Triple Disk 24:1 Low Backlash Low Friction Backdriveable” gearbox. At the end of your video, you ask which of the designs we’d like to see posted on Thingiverse and an assembly video. I’d like to vote for this design. I’d be very interested in trying to build this one myself. Great work and thanks for sharing.
Hi Carey
Thanks for your interest. This one has an assembly improvement over the previous design.
https://www.youtube.com/watch?v=XWp5dkeHgTY
https://hackaday.io/project/167855-simple-cycloidal-robot-leg-for-quadruped
With the proper design, tensioned cables can make “hands” small yet very strong grip and high degree of freedom.
I made some “small hands” with tensioned cables a few years ago.
Uses a TGY-306G servo and 12x 5×2 bearings
https://www.youtube.com/watch?v=RmE_u5cnerU
https://www.youtube.com/watch?v=qwZD98xAm8E
Danie, Thank you for showing your excellent work! By generating designs like these you both create interest and forward robotic innovation and technology. Many thanks.
Hi Chad, I can take no credit, this is all Paul Gould’s designs. I just help to give it some publicity