Robotics

Ruka-v2 Adds Wrist and Finger Abduction to Open-Source Hands

Robb Harlan 4 min read

Open-source hands keep closing the gap on “you need a six-figure end effector to do research.” NYU’s group is on version two of that thesis.

Ruka-v2, presented via the project site and arXiv:2603.26660 (March 2026), is a fully open-sourced tendon-driven humanoid hand. The headline upgrades over the original Ruka: a decoupled 2-DoF parallel wrist (flexion/extension and radial/ulnar deviation) and controlled finger abduction/adduction.

Ruka-v2 CAD diagrams showing degrees of freedom, adduction, and wrist movement
Ruka-v2 hardware overview: DoF map, abduction, and wrist motion. Source: ruka-hand-v2.github.io.

Specs and results from the paper

  • Original Ruka: 11 DoF, buildable for under $1,300
  • Ruka-v2: 16 DoF across fingers/thumb plus the 2-DoF wrist; major structure 3D printed; total material cost under $2,000; actuators parked proximally in the forearm
  • User study vs Ruka: 51.3% reduction in teleop completion time and 21.2% higher success rate on the reported task set
  • Applications shown: single-arm and bimanual teleop across 13 dexterous tasks (pen pickup, writing, charger plug-in, oven open, bread handling, declutter, wipe), plus autonomous visual BC policies on 3 tasks with BAKU
  • Payload table (static holds): e.g. non-thumb DIP–PIP 1,200 g for 15 s; wrist supination/pronation 1,215 g for 20 s; thumb 835 g for 20 s
Ruka-v2 hand holding a weighted shopping bag by the handles during payload test
Payload evaluation: Ruka-v2 holding a loaded bag. Source: ruka-hand-v2.github.io.

The wrist design uses intersecting rotation axes at a passive spherical ball joint so palm translation stays small during rotation; finger tendons route near the wrist center to limit length change when the wrist moves. Abduction uses independent knuckle modules with spring return; the middle finger stays fixed as a geometric reference.

Everything is meant to be rebuildable: 3D print files, assembly docs, controller software, CAD, and video are linked from the project page (GitHub + Onshape + GitBook).

A Human’s Take

Wrist and abduction are the boring DoFs until you try to open a cabinet or pinch a card without them. The 51% teleop speed-up is the number I bookmark — not because teleop is the product, but because operator time is where open hands either get used or sit on a shelf. Next receipt: multi-lab builds hitting those payload numbers without hero tuning.

Sources

Tags: Robotics