chassis/
The submersible chassis subsystems — pressure hull, thruster pod, ballast trim, comms module, and the upper-body sub-subsystems that are inherited from the bipedal sibling but operated submerged.
This directory will hold:
Lower body (submersible-specific)
- Pressure hull — 6061-T6 aluminum cylinder (~0.30 m dia × 0.80 m length), hard-anodized exterior, Delrin (acetal) endcaps with double-O-ring face-seal at each endcap. 50 m design depth (Phase 2 target). Houses battery, compute, safety supervisor, upper-body actuator drivers, comms electronics. Single point of failure on hull seal — seal architecture is conservative. Corpus shielding:
bluefin-21-rov, remus-class-auv, saab-sabertooth, jason-rov-1989 (recommended-future-corpus-additions).
- Thruster pod — 8-thruster vectored layout (4 horizontal vectored at ±45° + 4 vertical), ~0.7 m × 0.4 m × 0.2 m external space-frame mounting the thrusters and ballast-trim assembly to the pressure hull. Thruster choice: Blue Robotics T200 / T500 class subsea brushless, ~5 kgf thrust each. Each thruster on its own ESC on a CAN-FD bus shared with the inherited upper-body Moteus actuator bus. The 8-thruster ROV-class layout is the morphology-distinguishing piece of original engineering.
- Ballast trim — variable-buoyancy ballast trim (~1.5 L water displacement) at the centerline of the thruster pod. TBD (architectural call): active variable-buoyancy via syringe pump vs. fixed-trim with selectable ballast plates. v0.2 commitment is fixed-trim plates (more reliable); active variant deferred to v0.3+.
- Penetrators — 14 connectors through the rear endcap (8 thrusters + DVL + USBL + sonar + camera-array + tether + charging-and-data) + 2 through the front endcap (forward camera, depth sensor). Standard subsea wet-mateable connectors (Subconn, Birns, or compatible). Pressure-tested at 1.5× design depth.
- Communications module — external pressure-balanced housing for the JANUS acoustic transducer (per shoal ARCHITECTURE §4, JANUS / STANAG 4748 is the lingua franca) and the USBL transducer. Penetrators to inside-hull comms electronics. Tether port is rear-endcap penetrator-mounted.
Upper body (shared with bipedal sibling — submerged operation)
- Trunk-shared — the bipedal sibling’s torso link + waist-yaw joint, mounted at the top of the pressure hull at fixed origin via the
HULL_to_pelvis joint. The 21-DoF upper body in the bipedal sibling’s chassis/ is reused verbatim above the waist, with submerged-rated wrist seals.
- Arms-shared — the bipedal sibling’s 7-DoF arm × 2 (shoulder pitch / roll / yaw + elbow pitch + wrist yaw / pitch / roll). Inherited from free-humanoid-platform/chassis/. The arm housings are dry-side from shoulder to wrist; the wrist seal is the submerged-side boundary.
- Hands-shared — the bipedal sibling’s underactuated 5-finger synergy hand × 2. Inherited from free-humanoid-platform/chassis/ with submerged-rated tendon-channel jackets and hydrolytically-stable cable material (Vectran or HMPE / Dyneema). The synergy progress DoF [0,1] semantics are unchanged. Corpus citation:
pisa-iit-softhand, shadow-dexterous-hand, dlr-hand-ii (inherited).
Cross-references
Status
v0.0 scaffold. Detailed CAD is the Phase 1 / Phase 2 deliverable, gated on:
- The architectural-call resolution for active-vs-fixed ballast trim (current commitment: fixed for v0.2).
- The architectural-call resolution for 8-thruster vs. 6-thruster (current commitment: 8 for v0.2; the 6-thruster Aquanaut variant is held as a future descriptor variant).
- Pressure-hull seal pressure-cycle characterization on the Phase 2 prototype.
The pressure hull + 8-thruster pod is the priority Phase 2 prototype subassembly per ARCHITECTURE §7.