Jerry
81 lines
4.5 KiB
Markdown
81 lines
4.5 KiB
Markdown
# lyra — dexterous humanoid hand concept
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An aesthetically refined five-digit robotic RIGHT hand for an advanced
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bipedal robot: slim pearl-composite shell tubes over an exposed graphite
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structural spine, machined-aluminum precision knuckle clevises with visible
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pivot pins and rim washers, tendon-driven architecture (dorsal tendon
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channel grooves fanning to each knuckle plus a five-dial tensioner row at
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the wrist), integrated tactile sensing (2x2 palm pad array, per-phalanx
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soft-touch strips, palmar fingertip caps, amber-ringed palm sensor), and a
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6-bolt wrist flange. Graceful human-like proportions (~198 mm flange to
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middle fingertip), clean industrial design, no logos.
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## Degrees of freedom (16)
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| Group | Joints | DOF |
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| --- | --- | --- |
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| Each finger (x4) | MCP, PIP, DIP flexion (about -X) | 12 |
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| Thumb | CMC yaw (opposition swing about +Z), CMC flex, MP, IP (about -Y) | 4 |
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MCP abduction/spread is intentionally omitted (documented tendon-budget
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trade in `lyra_parts/chain.py`). Named poses are capsule-tuned to small
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positive clearances (`lyra_parts/clearance.py`): `precision_pinch` and
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`ok_sign` kiss the thumb-index pads at ~0.7-0.8 mm surface clearance,
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`tripod_pinch` chuck-grips a virtual ~12 mm object, and the `fist` thumb
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rests on the index middle phalanx — no pose or animation blend
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interpenetrates.
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## Files
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- `lyra.py` — build123d generator (`gen_step()`); authoritative source.
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Joints are authored as `cadpy.assembly.AssemblyHelper` revolute frames
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driven by the baked `relaxed` pose. Also exposes `gen_urdf()` /
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`gen_srdf()` for the robot description.
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- `lyra_parts/` — part-builder package. `chain.py` is the shared kinematic
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chain/pose/limit spec (stdlib-only FK included) used by the CAD assembly,
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the URDF/SRDF generators, and the animation sidecar; `lib.py` holds the
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palette and the verified `revolute_attach()` joint math; `palm.py` /
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`digits.py` build the parts; `description.py` emits the URDF/SRDF XML;
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`mass_props.py` holds baked CAD volume/COM/inertia/bbox data;
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`clearance.py` is the stdlib capsule-collision self-check (run
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`python -m lyra_parts.clearance` from this directory after editing
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poses or animation key orders — it sweeps every named pose and every
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sidecar blend path).
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- `lyra.step` — generated STEP assembly (derived artifact), baked in the
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`relaxed` pose. Occurrence refs `#o1.1..#o1.17` follow the `asm.add`
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order in `lyra.py` (palm, then index/middle/ring/pinky
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proximal/middle/distal, then thumb base/metacarpal/proximal/distal).
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- `.lyra.step.js` — CAD Viewer animation sidecar driving per-frame chain FK
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deltas against the baked pose. Animations: `poseTour` (a finger-ripple
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wave, then relaxed -> precision pinch -> OK sign -> point -> tripod
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pinch -> fist; key order chosen so every blend is collision-free),
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`graspLoop` (power grasp), `pinchLoop` (pinch with pad double-tap),
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`rippleLoop` (traveling finger curl wave with overlapping per-digit
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pulses), `countLoop` (count to five from a fist; the thumb lifts to a
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hover before any finger extends).
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Controls: `phase`, `mode`, `pose` (named SRDF pose hold), `grip`.
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- `lyra.urdf` — generated URDF (derived artifact): a frame-only
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`wrist_mount` root plus 17 physical links and 16 revolute joints,
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per-link 3MF mesh visuals, bbox collisions, CAD-derived inertials at an
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assumed 0.62 kg total mass.
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- `lyra.srdf` — generated MoveIt2 SRDF (derived artifact): per-digit joint
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groups, `fingers`/`hand` unions, a palm-mounted `hand_eef` end effector,
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disabled collisions, and hand group states (`zero`, `relaxed`, `fist`,
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`precision_pinch`, `tripod_pinch`, `point`, `ok_sign`).
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- `STEP/` — per-link wrapper sources (`gen_step()` per link) and their
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generated STEP parts; `3MF/` — per-link mm mesh sidecars referenced by
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the URDF.
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## Conventions
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Units mm. RIGHT hand: the wrist-flange mount face center is the origin,
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+Z distal (fingers up), +Y palmar, +X radial (thumb side). Every link frame
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sits at its joint center with axes parallel to the palm at zero angles
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(URDF joints are pure translations). Positive joint angles flex/curl.
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Regenerate with the CAD skill: `python scripts/step models/robots/lyra/lyra.py`.
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Regenerate link meshes per link with the CAD skill, e.g.
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`python scripts/step models/robots/lyra/STEP/<link>.py --3mf ../3MF/<link>.3mf`.
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Regenerate the robot description with the URDF/SRDF skills:
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`python scripts/urdf models/robots/lyra/lyra.py=models/robots/lyra/lyra.urdf`
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and `python scripts/srdf models/robots/lyra/lyra.py=models/robots/lyra/lyra.srdf`.
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