SRI abacus drive

=== SRI international: Abacus drive ===
https://patents.google.com/patent/US20190242464A1/en?inventor=Alexander+KERNBAUM An apparatus includes a first ring having an open annular space and a variable-width groove disposed on an interior peripheral surface of the first ring; a second ring rotatable within the open annular space of the first ring, where the second ring has a respective variable-width groove disposed on an exterior peripheral surface of the second ring; and a plurality of rollers disposed between, and configured to roll on, the interior peripheral surface of the first ring and the exterior peripheral surface of the second ring and rotatable therebetween.
https://patents.google.com/patent/WO2019221703A1/en?q=pure&q=roling&q=cycloid+%2c&q=sri&oq=pure+roling+cycloid+%2c+sri filed by SRI international A variety of mechanisms are provided for coupling the rotation of shafts or other mechanical elements having parallel but offset axes of rotation. The coupling mechanisms can couple such input and output elements via pins that are in contact with the input and output elements. The pins, upon rotation of the input and output elements, can engage in substantially pure roiling motion with respect to respective contact surfaces on the input and output members. Accordingly, the pins can reduce the number of bearings and increase efficiency relative to alternative coupling mechanisms. Such couplings may be employed in a variety of applications, including the coupling of rotations between elements of a cycloidal drive or a transmission that includes a member that undergoes cycloidal motion. For example, this coupling could replace the cage gear of a cycloidal drive in coupling the output to the cycloidal disc of a cycloidal drive. Invented by inventor:(Alexander KERNBAUM)
https://www.youtube.com/watch?v=zoaHeamUqBE Robotics engineers at SRI International in Silicon Valley have developed the first new rotary transmission design since the invention of the Harmonic Drive gear. Learn more: https://spectrum.ieee.org/automaton/robotics/robotics-hardware/sri-demonstrates-abacus-rotary-transmission. Zero backlash high gear ratio. From Tracked_vehicle#Variable_speed_drive_shaft
SRI’s Abacus drive has beads that roll in and out of a groove with a variable diameter. This causes the beads to effectively change their diameters depending on where in the groove they are, resulting in the same kind of cycloidal motion that you see in Harmonic Drive gears, but with less backlash(zero) than a harmonic drive and much less complex manufacturing.
=== 3d printable ===
https://www.youmagine.com/designs/abacus-drive-v0-v1 
https://www.thingiverse.com/thing:1868146/comments
=== links ===
genesis robotics high precision gear drives.
https://hackaday.com/2016/12/02/abacus-drive-is-a-speed-to-torque-game-changer/
Antenna tracking
Gears robot harmonic drive
https://www.sri.com/
Chris Annin six axis robot
Category:Backlash
Category:Robotics