Architecture

Proposed zonal layout for SPACE. Nothing here is decided until the matching ADR is accepted.

Reference topology

Data, RJ45Data, single pair48 V actuationHardwired e-stop loop

Fig. 1. One zone shown. A chair may have one central zone or a front and a rear zone (ADR-0002). Logic power rides on each single-pair link and is not drawn separately.

Tiers

Tier	Link	Nodes	Decision
Compute	RJ45 100/1000BASE-T	Jetson, Pi, cameras	ADR-0003
Motion and command	100BASE-T1 point-to-point	Racers, HMI, MIB	ADR-0003
Sense and accessory	10BASE-T1S multidrop	IMU, load cells, limits, small actuators	ADR-0003, ADR-0007

Power domains

Domain	Source	Feeds	Decision
Actuation	Smart bus bar, 48 V branches	Power stages only	ADR-0004
Logic	PoDL, or a 24 V harness rail	MCU, PHY, sensors	ADR-0004

Stopping

Layer	Owner	Trigger	Action	Decision
Network	MIB / supervisor	joystick released, planner stop	SAFE_STOP to each drive	ADR-0005
Node	Racer	SAFE_STOP, 200 ms command silence	ramp at `accel_limit`, then hold	ADR-0005
Node	Racer	ESTOP, guard fault	bridge Hi-Z	ATOS motor API
Power	Smart bus bar	node not safe within bound	open the drive's 48 V branch	ADR-0005
Hardware	E-stop loop	button pressed, loop broken	open every actuation branch	ADR-0006

Changes from PRD v0.1

PRD item	Was	Proposed
§3.2 pillars	P, A, C	S, P, A, C (ADR-0001)
§3.3 item 1	one 48 V class for every node	two power domains
§3.3 item 2, E-02	100BASE-TX everywhere	IP everywhere, PHY by tier
§4.2 non-goal	no multi-axis sync	gPTP timestamps in every message (ADR-0008)
§6.1 topology	flat star	zones
F-04	stop always coasts	SAFE_STOP holds, ESTOP coasts
H-07	"on-board Ethernet"	MCU/PHY platform choice (ADR-0010)
H-11, H-14, E-08	Racer or ABC problems	zone and bus bar responsibilities
Eco-5	first P node is the last step	smart bus bar is a foundation item