Meets the standard. Then answers questions the standard doesn't ask.

When all three layers trigger simultaneously, the system takes the most conservative input. If ultrasonic says 1.8 m, depth camera says 1.2 m, and floor contact says "no event", the planner uses 1.2 m as the distance estimate and applies the corresponding deceleration profile. If floor contact triggers at any distance, it issues a full stop command independent of the other two, since that signal indicates physical contact has occurred or is about to occur. No layer overrides the floor contact trigger except a hardware fault flag from that sensor itself.

Behavior depends on which sensor fails and how. If one of the eight ultrasonic transducers self-reports a fault, the robot continues at reduced speed (0.4 m/s) and sends an alert to the fleet operations portal. It does NOT stop unless the fault leaves a coverage gap larger than 90 degrees in the proximity ring. If the depth camera fails completely, the robot drops to 0.4 m/s and ultrasonic-only mode. If the floor-contact sensor array fails, the robot stops and waits for a manual clearance command. The logic is: the floor contact sensor is the final backstop; if it's unavailable, we do not continue operating at any speed.

The robot stops and yields each time the detection threshold is crossed, regardless of history. There is no adaptive "this person blocked me twice so I'll keep moving" mode. After 60 seconds of continuous obstruction at the same task waypoint, the robot broadcasts a yield request through the fleet portal and holds position. The operations supervisor receives an alert. After 120 seconds, it declares the route temporarily blocked and reroutes if an alternative route is available. This is intentionally conservative: a human choosing to stand in the path is treated as a valid operational state, not a fault.

Japan's Industrial Safety and Health Act (ISHA) requires mobile machinery operating near workers to either provide physical separation or demonstrate equivalent safety through a documented risk assessment. We support the second path. The Closer technical documentation package includes a pre-formatted risk assessment template aligned to JISHA notification requirements, a facility-specific hazard log template, and the test scenario data referenced on this page. Most Japanese pilot operators have completed their internal safety officer review using this package within 4 to 6 weeks. We can also arrange a site visit from our safety team to support the facility's assessment process directly.

Minimal. We provide a 15-minute worker briefing (available as a printed one-page summary or a short video, localized to Japanese). The briefing covers: what the robot does if it detects you (slows and yields), how to stop it if needed (move toward it, wave, or use the physical e-stop), and what the lights and sounds mean. Workers who completed the briefing in beta sites reported comfort levels similar to shared-aisle pallet jack operation within two weeks. No ongoing re-certification is required unless a software update changes operating behavior, in which case we issue a change notice with a revised briefing.

The robot's operating mass is 68 kg at maximum payload. At 0.4 m/s proximity mode speed, kinetic energy at contact is approximately 5.4 J, below the ISO 13849 body-part force and pressure limit thresholds for low-severity contact. At standard 0.8 m/s aisle speed, energy is approximately 21.8 J. The three-layer stop chain is designed so that any single sensor failure does not eliminate detection; two layers must simultaneously fail without either raising a fault flag before a contact event could occur. The SIL 2 design target on the stop chain addresses this specific failure mode. We share the full FMEA (Failure Modes and Effects Analysis) with qualified safety reviewers under NDA.