2020 Arm Existing Specs

Owned by Ethan Cronier
Last updated: Jan 16, 2022 by Austin Tailon Huang
1 min read

dof: 5dof

weight: 14kg

reach: ~1m

arm type: polar articulated

actuator type: gearbox brushed DC, linear actuator bicep

transmission type:

  • turn table: worm drive
  • bicep: direct
  • elbow: worm drive
  • wrist: worm & mitre gear drive
  • claw: screw drive (no ball bearings)

largest number of gears per transmission: 7 in the wrist (all 7 gears are controlled with 2 motors, 2 axis are depended on each other not good for the tolerance stackup)

primary material type: laser cut 6061 aluminum

primary bearing material: bronze bushings (this is fine for the elbow but less ideal for motor shafts; rpm too high)

encloser: 3d printed flat covers, otherwise none

wire management: none

pcb location: all boards on bicep

sensors:

  • blackfly camera on wrist
  • absolute encoders on each joint



biggest issues with current design:

  • backlash is everywhere - worms are not very precise or designed poorly
  • front heavy - motors can be moved back to the elbow
  • allen key is jank