System

Remote Weapon Station (RWS), project se-remote-weapon-station-rws, mid-decomposition. At session start, 2/8 subsystems complete ({{entity:Safety Interlock System}}, {{entity:Fire Control System}}). Session goal: clear the specTree 6/8 blocker by decomposing the four highest-priority pending subsystems. All four were completed: {{entity:Weapon and Ammunition Handling Assembly}} (SIL 2), {{entity:Turret Drive Assembly}} (SIL 2), {{entity:Electro-Optical Sensor Assembly}} (SIL 2), and {{entity:Operator Control Unit}} (SIL 0). Spec tree ended at 6/8 complete; IFC count reached 24 (up from 17); total requirements 125.

Decomposition

Weapon and Ammunition Handling Assembly was decomposed into five components: {{entity:Weapon Cradle and Mount}} ({{hex:CE851018}}), {{entity:Recoil Buffer and Damping System}} ({{hex:CED51019}}), {{entity:Ammunition Magazine Assembly}} ({{hex:CE851059}}), {{entity:Belt Feed and Transfer Mechanism}} ({{hex:CE851018}}), and {{entity:Barrel Change Mechanism}} ({{hex:4CB53819}}). The key structural decision was separating recoil attenuation from the cradle, reducing turret structural load from 25kN to a 5kN transmitted force ceiling. The Barrel Change Mechanism produces a barrel retention status signal fed directly to the SIS — an unlocked barrel asserts a hardwired BARREL-NOT-LOCKED discrete to prevent firing.

flowchart TB
  AMA["Ammunition Magazine Assembly"]
  BFTM["Belt Feed and Transfer Mechanism"]
  WCM["Weapon Cradle and Mount"]
  RBD["Recoil Buffer and Damping System"]
  BCM["Barrel Change Mechanism"]
  SIS["Safety Interlock System"]
  AMA -->|belt feed| BFTM
  BFTM -->|chambered round| WCM
  WCM -->|recoil force 25kN| RBD
  BCM -->|BARREL-NOT-LOCKED discrete| SIS
  BCM -->|barrel latch| WCM

Turret Drive Assembly was decomposed into {{entity:Azimuth Drive Motor and Gearbox}} ({{hex:D7D51008}}), {{entity:Elevation Drive Motor and Gearbox}} ({{hex:D7D51018}}), {{entity:Turret Drive Controller}} ({{hex:55F57208}}), {{entity:Azimuth Slip Ring Assembly}} ({{hex:D6851018}}), and {{entity:Turret Position Encoder Assembly}} ({{hex:D4E55018}}). The worm gearbox on the elevation axis provides self-locking on power loss, eliminating a separate elevation hold brake. Dual-redundant encoders allow both TDC and SIS to independently verify turret position.

Electro-Optical Sensor Assembly was decomposed into {{entity:Thermal Imaging Camera}} ({{hex:D4EC5019}}), {{entity:Daylight Television Camera}} ({{hex:D6C55019}}), {{entity:Laser Rangefinder}} ({{hex:D4C55019}}), and {{entity:Sensor Head Stabilisation Platform}} ({{hex:DFB51008}}). All three sensors share a single 2-axis stabilised gimbal — rejected per-channel gimbals would increase sensor head mass and require separate bore-sight maintenance.

Operator Control Unit was decomposed into {{entity:Operator Display Unit}} ({{hex:D6CC5018}}), {{entity:Gunner Hand Controller}} ({{hex:D6CD5019}}), and {{entity:OCU Control Processing Unit}} ({{hex:D1F57018}}). Physical separation of the GHC from the display ensures weapon control input remains available when the display fails, and retains tactile trigger operation in cold or high-vibration conditions.

Analysis

Trait clustering across the four subsystems shows a consistent pattern: all structural/mechanical components (Weapon Cradle, Recoil Buffer, Slip Ring) classify with {{trait:Structural}} and {{trait:Physical Object}} without {{trait:Processes Signals/Logic}}, while control and processing components (TDC, OCU CPU) classify as {{trait:System-integrated}} and {{trait:Processes Signals/Logic}} without {{trait:Structural}}. This trait boundary maps cleanly onto the IEC 61508 (Functional safety of E/E/PE safety-related systems) architectural separation between load-bearing and programmable elements — a reassuring cross-domain consistency.

Two high-severity lint findings were acknowledged: the {{entity:Dual-Channel Safety Controller}} and {{entity:Hardware Firing Interlock Relay}} are classified as {{trait:Powered}} but have no power budget requirements at the component level. These are intentionally deferred to the Power Distribution Unit subsystem decomposition, where the 24VDC distribution architecture will be specified.

Requirements

Twenty-eight requirements were created this session: 10 SUB, 7 IFC, 6 VER, 4 ARC, plus trace links. Key requirements include {{sub:SUB-REQ-025}} (barrel retention fire permit — hardwired BARREL-NOT-LOCKED to SIS within 50ms, SIL 2), {{sub:SUB-REQ-027}} (TDA drive inhibit — both axes stop within 200ms of SIS DRIVE-INHIBIT, SIL 2), and {{sub:SUB-REQ-031}} (EOSA degraded mode — day channel and LRF must continue operating independently when thermal imager fails, SIL 2). Interface {{ifc:IFC-REQ-018}} defines the barrel retention hardwired discrete — active-low convention so an open-circuit fault de-asserts the fire permit. Verification {{ver:VER-REQ-020}} covers the WAHA recoil structural test: 500 load cycles at 25kN with CMM measurement before and after.

Next

Two subsystems remain pending: Communications Interface Unit (SIL 0) and Power Distribution Unit (SIL 0). The PDU is the natural next session because it resolves the two acknowledged lint findings (power requirements for SIS components) and defines the vehicle power bus architecture that all other subsystems reference. After PDU, the CIU will complete the spec tree at 8/8, enabling the harness to transition to QC flow.