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Nodes & Edges

Physical locations and paths in the warehouse.

Nodes

Definition

A node represents a physical location where a robot can be.

Node Types

Type Description
aisle Regular traversable location
rack Storage rack location
station_pick Pick station
station_drop Drop station
station_inbound Inbound receiving
station_outbound Outbound shipping
charging Charging station
maintenance Maintenance station

Node Properties

Property Description
id Unique identifier
name Human-readable name
x, y Coordinates (meters)
type Node classification

Node Capacity

Default: 1 robot per node

Can be configured higher for:

  • Intersections
  • Station areas
  • Waiting zones

Edges

Definition

An edge connects two nodes, representing a path robots can traverse.

Edge Properties

Property Description
id Unique identifier
from Source node ID
to Destination node ID
length Distance in meters
bidirectional Both directions allowed?
capacity Max robots simultaneously

Edge Length

Physical distance between nodes:

length = sqrt((x2-x1)² + (y2-y1)²)

Or specified explicitly for non-straight paths.

Edge Capacity

Default: 1 robot per edge

Higher capacity for:

  • Wide aisles
  • Multi-lane paths
  • High-traffic routes

Bidirectional Edges

Default (Bidirectional)

{
  "from": 0,
  "to": 1,
  "bidirectional": true
}

Equivalent to two one-way edges.

One-Way Edges

{
  "from": 0,
  "to": 1,
  "bidirectional": false
}

Only allows travel from 0 to 1.

Use Cases for One-Way

  • Traffic flow control
  • Aisle direction policies
  • Reduced congestion

Travel Time

Calculated from edge length and robot speed:

travel_time = edge_length / robot_speed

Example:

  • Edge: 6 meters
  • Speed: 1.5 m/s
  • Time: 4 seconds

Capacity and Congestion

Node Capacity

When a node is at capacity:

  • New robots must wait
  • Or reroute (if configured)

Edge Capacity

When an edge is at capacity:

  • Robots wait at source node
  • Release when edge clears

Capacity Configuration

traffic:
  node_capacity_default: 1
  edge_capacity_default: 1

Example: Grid Layout

Nodes:
  N0(0,0) -- N1(3,0) -- N2(6,0)
     |          |          |
  N3(0,3) -- N4(3,3) -- N5(6,3)
     |          |          |
  N6(0,6) -- N7(3,6) -- N8(6,6)

Edges (bidirectional, length 3.0):
  N0-N1, N1-N2, N0-N3, N1-N4, N2-N5
  N3-N4, N4-N5, N3-N6, N4-N7, N5-N8
  N6-N7, N7-N8

Best Practices

Node Placement

  • Place at decision points
  • At racks and stations
  • At intersections

Edge Design

  • Use actual path distances
  • Consider robot turning radius
  • Account for acceleration/deceleration

Capacity Planning

  • Higher capacity at bottlenecks
  • Match to actual aisle widths
  • Test with expected traffic