System

Surgical Robot System, session 350. Six functional subsystems were already decomposed (Motion Control, Safety and Interlock, Vision and Imaging, Haptic Feedback, Communication and Data Management, Surgical Instrument). This session addressed the {{entity:Power Management Subsystem}} — the last major functional subsystem with no component decomposition — and resolved a high-severity lint finding in the {{entity:Vision and Imaging System}}.

Decomposition

The {{entity:Power Management Subsystem}} was decomposed into four components: {{entity:Main Power Distribution Unit}} ({{hex:D6851058}}), {{entity:Auxiliary Power Supply}} ({{hex:57cb1da3}}), {{entity:UPS Battery Module}} ({{hex:D6D51058}}), and {{entity:Power Sequencing Controller}} ({{hex:D1F77A18}}). The critical structural decision was the electrical isolation of the Auxiliary Power Supply from the main bus — it feeds the {{entity:Emergency Stop Chain}} contactor coils and {{entity:Watchdog Timer Controller}} exclusively, remaining energised through any main bus fault or brownout. This isolation is what makes the safety subsystem independent of application-layer software failures.

flowchart TB
  MPDU["Main Power Distribution Unit"]
  APS["Auxiliary Power Supply"]
  UPS["UPS Battery Module"]
  PSC["Power Sequencing Controller"]
  ESC["Emergency Stop Chain"]
  SAI["Safety and Interlock Subsystem"]
  MPDU -->|22-26V DC bus| APS
  MPDU -->|power rails| PSC
  UPS -->|battery backup| APS
  APS -->|isolated 24V| ESC
  APS -->|isolated 24V| SAI
  PSC -->|contactor sequence| MPDU

The {{entity:Power Sequencing Controller}} enforces startup order: Safety and Interlock first, then Communication and Data Management, then Motion Control, then Surgical Instrument. Shutdown reverses the sequence. This ensures no motion-capable subsystem receives power before hardware safety supervision is active.

The {{entity:Safety and Interlock Subsystem}} internal structure — established in prior sessions — was validated intact this session:

flowchart TB
  n0["Watchdog Timer Controller"]
  n1["Emergency Stop Chain"]
  n2["Joint Force Monitor"]
  n3["Communication Monitor"]
  n4["Safe State Manager"]
  n0 -->|watchdog trip| n4
  n1 -->|E-stop event| n4
  n2 -->|force violation| n4
  n3 -->|link fault| n4

Analysis

The UHT classification of {{entity:Emergency Stop Chain}} ({{hex:44AD7810}}) as non-Physical-Object is ontologically correct: the E-stop chain is a circuit topology, not a discrete physical item. The lint similarity flag against {{entity:Force Signal Conditioner}} ({{hex:D4A51018}}) — Physical Object — reflects a real distinction: the force signal conditioner is a PCB assembly, the E-stop chain is a wired loop. This is an acknowledged finding, not a classification error.

The {{entity:Power Sequencing Controller}} ({{hex:D1F77A18}}) classified with traits Active and Functionally Autonomous — consistent with an embedded microcontroller that initiates power-rail monitoring and startup sequencing without external trigger per boot cycle.

Cross-domain search for “power sequencing safety interlock” returned railway signalling power supply controllers as the closest analog — the same hardwired auxiliary supply isolation pattern appears in ETCS Eurobalise readers, where the safety processor runs on a physically separate power domain from the communication electronics. This confirms the architectural approach.

Five previously acknowledged lint findings (Powered trait without power budget) are now partially resolved: the power source is defined through {{entity:Main Power Distribution Unit}} and {{entity:Auxiliary Power Supply}}. Per-subsystem power budgets remain unspecified — deferred to QC session.

Requirements

{{sub:SUB-MAIN-043}}: UPS 30-minute minimum duration at full load, derived from {{sys:SYS-MAIN-005}}. The 30-minute figure comes from IEC 60601-1 clause 11.8.4 and the realistic time to complete a laparoscopic procedure segment and park all arms safely.

{{sub:SUB-MAIN-044}}: Power sequencing order (Safety first, reverse on shutdown). Traced to {{sys:SYS-MAIN-013}} — 8-hour operational continuity requires controlled state transitions throughout the operating period.

{{sub:SUB-MAIN-045}}: Auxiliary Power Supply isolation — must remain energised through any main bus brownout below 85% nominal.

{{ifc:IFC-MAIN-029}}: Auxiliary Power Supply to {{entity:Emergency Stop Chain}} contactor coil interface — 22–26V DC with no interruption exceeding 10ms. The 10ms limit matches IEC 60204-1 Category 3 contactor dropout time specification.

{{sub:SUB-MAIN-046}}: {{entity:Image Processing Pipeline}} safety constraint — must detect frame artefacts exceeding 5% pixel corruption or latency violations exceeding 33ms (2-frame drop at 60fps), substituting a frozen clean frame and alerting the Surgeon Console within 10ms. Addresses high-severity lint finding: FPGA-based pipeline is Functionally Autonomous without this supervisory requirement.

Verification entries {{ver:VER-MAIN-032}} (IFC-MAIN-029 contactor voltage under simulated mains loss) and {{ver:VER-MAIN-033}} (UPS 30-minute discharge test at 80% charge state) were added. Architecture decision {{arc:ARC-MAIN-008}} records the rationale for isolated auxiliary supply over single-supply with software priority.

Next

{{entity:Energy Delivery System}} (electrosurgical RF delivery) is the only system-level subsystem without component decomposition or requirements. It requires decomposition into: Electrosurgical Generator, Instrument Energy Interface, Energy Delivery Controller, and potentially return-electrode monitoring. The next session should address this, followed by first-pass completion assessment across all subsystems.