Surgical Robot System

Rationale: Core value proposition of the surgical robot — patients require reduced trauma and recovery time; surgeons require precision beyond unaided manual capability for complex anatomical regions.

Rationale: Fundamental patient safety obligation. Uncontrolled actuator motion or energy delivery during loss of control is a Class III hazard (irreversible patient harm). Regulatory bodies (FDA 510(k), MDR) mandate fault-containment as a baseline approval criterion.

Rationale: Hospitals will not accept systems requiring structural OR modifications; retrofit-free integration is a purchasing prerequisite for the majority of target customers and is mandated by facilities management policies.

Rationale: Surgical site infection (SSI) is a primary post-operative complication; regulatory sterility requirements (ISO 13485, EU MDR Annex I) impose design obligations. Breach of sterile field is a never-event in regulated healthcare environments.

Rationale: Surgeon fatigue during long procedures increases error rate and is a patient safety risk; ergonomic design is required by IEC 62366 (usability). Simulation training pathway is required by hospital credentialing committees before granting robotic surgery privileges.

Rationale: Fundamental stakeholder need: surgical robot adoption is justified only if it enables operations beyond freehand limits.

Rationale: Regulatory requirement per ISO 13485 and IEC 60601-1: active surgical devices cannot create new patient hazards. Uncontrolled instrument motion in a body cavity is immediately life-threatening.

Rationale: Infection control and regulatory requirement: surgical site infection from non-sterile instrumentation can be fatal; EN ISO 11135 sterilisation standards must be met for EU and US market approval.

Rationale: Stakeholder need from surgical user research: loss of visual feedback during robotic surgery is the leading cause of conversion to open surgery; 3D HD stereo has been shown to reduce depth-perception errors by 40% vs. 2D in laparoscopic studies.

Rationale: Operational efficiency requirement: laparoscopic procedures require 8-15 instrument changes on average; each break in sterility adds risk and OR time, increasing cost and infection probability.

Rationale: Hospital governance and regulatory mandate: EU MDR Article 83 and FDA 21 CFR Part 820 require post-market surveillance data; malpractice liability creates institutional demand for full procedure recording.

Rationale: Operational requirement from theatre schedulers: a typical surgical list runs 7-9 hours with up to 4 procedures; unplanned system downtime forces cancellation, increasing patient waiting lists and OR costs.

Rationale: Sub-millimetre precision (STK-MAIN-001) requires quantified latency and repeatability: >1ms control loop latency introduces perceptible lag causing surgical error; ±0.1mm repeatability matches fine suture placement requirements in cardiovascular and ENT surgery.

Rationale: 250ms is derived from maximum safe uncontrolled instrument travel distance (<0.5mm at typical 2mm/s max tip velocity) — a hard limit from hazard analysis. Single-point failure coverage required for SIL 3 classification under IEC 62061.

Rationale: 60Hz 3D video prevents perception of flicker; <100ms latency is the threshold above which surgeons report disorientation (clinical usability studies). Tissue colour discrimination is safety-critical for distinguishing healthy and ischaemic tissue.

Rationale: Haptic feedback prevents inadvertent excessive tissue force; ≤0.1N resolution is required to feel tissue-plane transitions (typically 0.2–0.5N differential). Without force feedback, suture breakage rates and inadvertent organ perforation increase (documented in clinical literature).

Rationale: Mains power failure during active surgery is a known hazard; uncontrolled arm drop on mains loss is life-threatening. 60s battery bridge covers typical handoff time for instrument withdrawal based on human factors study of procedural steps.

Rationale: ISO 11135 and EU MDR Annex I mandate validated sterility assurance for patient-contacting devices. IPA 70% and glutaraldehyde are the standard biocides used in OR disinfection protocols; compatibility prevents material degradation and failure in service.

Rationale: Latency budget derived from human motor control studies: perceptible lag above 100ms disrupts surgeon proprioception and creates oscillatory overcorrection. Value validated by da Vinci and RAVEN II published performance data.

Rationale: Motion scaling enables micro-surgical precision: a 10mm surgeon hand movement produces a 1mm instrument movement at 10:1, enabling suturing of 1-2mm vessels not achievable with freehand technique. Three ratios cover different procedure types from gross to micro.

Rationale: Physiological tremor in surgeons is 8-12Hz at 0.1-0.5mm amplitude; at 10:1 motion scaling without filtration this would translate to unacceptable 0.01-0.05mm tip oscillation on delicate tissue. 6Hz cutoff preserves intentional motion bandwidth while removing tremor.

Rationale: 50ms arrest time derived from worst-case instrument velocity of 50mm/s: at 50ms arrest, maximum overshoot is 2.5mm. Any larger overshoot risks laceration of adjacent tissue. This is an IEC 62304 SIL 3 safety function.

Rationale: 50ms video latency budget is half the motor latency budget to ensure visual feedback arrives before the surgeon's corrective motion: higher video latency than motor latency causes the surgeon to over-correct. 1080p/60Hz matches clinical standard for high-fidelity tissue discrimination.

Rationale: Tissue damage threshold studies show that inadvertent forces above 5N on bowel serosa or vessel walls cause serosal tears; 8N exceeds the tensile strength of small bowel mesentery. Dual thresholds allow warning before hard cutoff to avoid abrupt motion.

Rationale: Derived from STK-MAIN-015: surgical lists run 7-9 hours. System must outlast the list; thermal modelling of electronics and actuator duty cycles must confirm no performance degradation in the final hour of a maximum-length list.

Rationale: Derived from STK-MAIN-011: all surface-contacting components must support validated sterilisation cycle. Autoclave compatibility restricts material selection (no ABS plastics, requires PEEK and 316L stainless on patient-contact surfaces).

Rationale: Derived from STK-MAIN-014: EU MDR Article 83 and NHS clinical governance require procedure-level audit trails. 1kHz kinematics captures all motion events; 90-day retention covers most surgical complication investigation windows.

Rationale: Single-arm dropout must not abort a procedure mid-operation: patient is already prepared and open. Maintaining 2 of 3 arms allows the surgeon to complete critical steps before safely withdrawing. 500ms alert keeps surgeon awareness within one action cycle.

Rationale: Electrosurgical energy delivery is a core surgical function of a robotic system. Activation and deactivation latency bounds are derived from IEC 60601-2-2 and clinical workflow requirements: 100ms activation is acceptable for surgeon intent recognition; 50ms deactivation is the safety-critical parameter preventing unintended tissue damage after the surgeon releases activation.

Rationale: IEC 62443-3-3 SR 1.2 requires authentication for all users, software processes, and devices that access control system resources. In a surgical robot, command injection at inter-subsystem interfaces represents a Class III medical device cybersecurity risk per FDA 2023 guidance. Authentication must be a system-level requirement so it cascades to all critical subsystems including KE, TG, RTPE, and TTAC.

Rationale: The OR environment contains monopolar electrosurgical generators at 300kHz-3MHz and up to 400W, diathermy equipment, and wireless patient monitoring. IEC 60601-1-2 HPHE immunity compliance is mandatory for CE marking under MDR 2017/745 and directly mitigates risk of motion commands being corrupted by conducted interference from co-located electrosurgical equipment.