Task Lifecycle¶

The complete journey of a robot task from creation to completion.

Task Types¶

Type	Description
Pick	Retrieve item from storage
Drop	Deliver item to destination
Transport	Move item between locations
Charge	Travel to charging station
Maintenance	Go for scheduled maintenance

Lifecycle Stages¶

┌─────────────────────────────────────────────────────────────┐
│                        TASK LIFECYCLE                        │
├──────────┬───────────┬──────────┬──────────┬────────────────┤
│ Created  │ Assigned  │ Traveling│ Executing│   Completed    │
│          │           │          │          │                │
│ Order    │ Robot     │ Moving   │ At       │ Task done,     │
│ arrives, │ selected, │ to       │ station, │ robot freed    │
│ task     │ task      │ station  │ being    │                │
│ queued   │ scheduled │          │ serviced │                │
└──────────┴───────────┴──────────┴──────────┴────────────────┘
     │           │           │          │            │
     t₀         t₁          t₂         t₃           t₄

Stage 1: Task Creation¶

Trigger¶

Tasks created when:

Order arrives
Replenishment needed
Charging required
Maintenance scheduled

Initial State¶

Task {
  id: T001
  type: Pick
  origin: Rack R5
  destination: Station S1
  status: Pending
  created_at: 10:00:00
}

Stage 2: Assignment¶

Assignment Process¶

Task enters queue
Policy selects robot
Robot receives task
Path calculated

Assignment Policies¶

Policy	Selection Criteria
`nearest_idle`	Closest available robot
`least_busy`	Robot with fewest tasks
`round_robin`	Sequential assignment

After Assignment¶

Task {
  ...
  status: Assigned
  robot: R3
  assigned_at: 10:00:05
  path: [N1, N5, N10, N15]
}

Stage 3: Traveling¶

Robot Movement¶

Robot navigates through calculated path:

N1 ──> N5 ──> N10 ──> N15
      ↑
    Current position

Possible Events¶

Event	Response
Path clear	Continue travel
Node blocked	Wait or reroute
Battery low	Interrupt for charging
Higher priority task	May preempt (if configured)

Travel Metrics¶

Travel time: Time from start to arrival
Wait time: Time blocked by traffic
Distance: Total path length

Stage 4: Execution¶

At Destination¶

Robot arrives at station and begins service:

Enter station queue (if needed)
Wait for service slot
Receive service
Complete task actions

Service Time¶

Variable based on task:

service_time_s:
  distribution: lognormal
  base: 6.0
  per_item: 2.0

Queue Behavior¶

Station Queue:  [R3] ← [R7] ← [R12]
                 ↑
              Being serviced

Stage 5: Completion¶

Task Finished¶

Task {
  ...
  status: Completed
  completed_at: 10:02:30
}

Robot Released¶

Robot transitions to:

Idle: No pending tasks
Next task: If tasks queued
Charging: If battery low

Time Breakdown¶

Task Time Components¶

┌─────────────────────────────────────────────────────────┐
│                    Total Task Time                       │
├──────────┬──────────┬──────────┬───────────┬───────────┤
│  Queue   │  Travel  │   Wait   │   Queue   │  Service  │
│  Wait    │  Time    │  (traffic)│  (station)│   Time   │
│          │          │          │           │           │
│  t_q     │   t_t    │   t_w    │    t_sq   │    t_s    │
└──────────┴──────────┴──────────┴───────────┴───────────┘

Total = t_q + t_t + t_w + t_sq + t_s

Key Metrics¶

Metric	Formula
Task time	completion_time - creation_time
Travel ratio	travel_time / task_time
Wait ratio	(traffic_wait + queue_wait) / task_time
Service ratio	service_time / task_time

Task Interruption¶

Preemption¶

Higher priority tasks may interrupt:

Current task paused
Urgent task executed
Original task resumed

Battery Interrupt¶

Low battery forces charging:

Task T1: Traveling... → Battery < 20% → Charging... → Resume T1

Failure Interrupt¶

Robot failure stops task:

Task T1: Executing... → Robot fails → Task reassigned to R2

Example Timeline¶

10:00:00.000  Order O1 created
10:00:00.100  Task T1 created (pick SKU001 from R5)
10:00:00.250  T1 assigned to Robot R3
10:00:00.300  R3 starts traveling to R5
10:00:04.500  R3 arrives at R5
10:00:04.600  R3 picks item
10:00:04.700  R3 starts traveling to Station S1
10:00:08.200  R3 arrives at S1
10:00:08.300  R3 joins station queue (position 2)
10:00:15.100  R3 reaches service slot
10:00:21.400  Service complete
10:00:21.500  Task T1 completed
10:00:21.600  R3 becomes idle