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Physical AIby Santi

07Aerial robots, swarms & dual use

How to keep a robot fleet operating through communication and positioning failures

What keeps working, what degrades and when the mission must stop if GNSS, links or a fleet node fail. Every figure links to its source; where there is no sufficient public evidence, we say so.

Last reviewed: 2026-11Methodology & sources →

01 · The operational problem

“I need to inspect a facility even where coverage or positioning is unreliable”

Tunnels, mines, boiler interiors, substations and solar plants spanning hundreds of hectares share one problem: GNSS and radio are not guaranteed. GNSS interference is already documented by aviation authorities in several European regions.[EASA, 2026]

Operating envelope for each failure

No technique makes a fleet “work when everything fails”. What you can design is what the system does on each failure. This logic should be written into the operating procedure and the authorisation.

  • GNSS loss or spoofing

    The mission continues if…
    A validated alternative localization source exists (VIO, LiDAR, beacons) and the environment is within its envelope (light, texture, geometry).
    It degrades…
    Position uncertainty grows with distance: reduce speed and range and prioritise the return.
    It must stop when…
    There is no alternative source, or uncertainty exceeds the margin to obstacles or the authorised geofence.

    [EASA, 2026][IEEE ICRA, 2018]

  • Loss of the command link (C2)

    The mission continues if…
    The authorised lost-link procedure allows completing the pre-programmed task; data is stored onboard.
    It degrades…
    No live video or re-tasking: the operator loses the ability to intervene.
    It must stop when…
    As set by the contingency procedure: return to launch, to the dock, or a safe landing.

    [EASA][IETF, 2022]

  • Network partition or leader loss

    The mission continues if…
    The group that keeps a majority of nodes can elect a new leader and reassign tasks.
    It degrades…
    The minority group cannot elect a leader: it keeps already-assigned tasks that are safe without coordination.
    It must stop when…
    A task requires coordination (several robots in the same volume, for example): the minority group suspends it.

    [USENIX ATC, 2014]

  • Perception degradation (darkness, fog, dust)

    The mission continues if…
    Another sensor covers the condition: LiDAR in darkness, thermal in low light, or onboard lighting.
    It degrades…
    Obstacle avoidance and visual localization lose reliability: increase safety distances.
    It must stop when…
    No onboard sensor ensures obstacle detection in the current condition.

    [IEEE ICRA, 2018]

02 · Decision table

What to evaluate, what to ask the vendor and what to measure in the pilot

Start from the need, not the technology. For each typical need, this table summarises the evaluation criteria, the questions to ask the vendor and the metrics that belong in the pilot's acceptance criteria.

  • Indoor and confined-space inspection

    What to evaluate

    • GNSS-free localization (LiDAR, VIO)
    • Onboard lighting and darkness sensors
    • Collision and obstacle tolerance
    • Recovery after link loss

    Questions for the vendor

    • Localization results in an environment equivalent to ours?
    • What does the system do if it loses localization mid-gallery?
    • What is the real endurance with the payload we need?

    What to measure in the pilot

    • Position error against surveyed control points
    • Share of surface with valid data
    • Pilot interventions per flight
    • Inspection time vs. current method
  • Fleets over large sites

    What to evaluate

    • Actual coordination level (central, distributed or swarm)
    • Communications coverage across the site
    • Battery and dock management
    • Supervision: robots per operator

    Questions for the vendor

    • Who decides task allocation and what happens if that element fails?
    • What data do robots share with each other and how often?
    • What regulatory authorisation do similar operations hold?

    What to measure in the pilot

    • Hectares inspected per hour and per operator
    • Valid vs. planned coverage
    • Time to reassign a failed robot's task
    • Confirmed findings vs. false positives
  • Continuity under disconnection

    What to evaluate

    • Which tasks are safe without a link and which are suspended
    • Onboard storage and forwarding when contact returns
    • Authorised contingency procedures
    • Behavior under network partition

    Questions for the vendor

    • Can we see a demonstration with an induced link loss?
    • What happens if the fleet splits into two groups without contact?
    • How is what happened during disconnection logged?

    What to measure in the pilot

    • Missions completed with induced disconnection
    • Data recovered vs. captured
    • Reconnection and sync time
    • Incidents and geofence deviations
  • Economic viability

    What to evaluate

    • Actual uptime (system availability)
    • Data quality for the decision being made
    • Maintenance, batteries and replacement
    • Cost per mission and per useful finding

    Questions for the vendor

    • What is the measured availability at customers with similar use?
    • What does the subscription include and what is extra?
    • What is the service life of batteries and sensors?

    What to measure in the pilot

    • Cost per mission vs. current method
    • System availability (%)
    • Maintenance hours per operating hour
    • Findings that lead to a maintenance action

03 · Coordination levels

Not every group of drones is a swarm

The difference is not how many robots fly, but who decides and what information they share. Each level behaves differently under the same failure.

  1. 1

    Independent drones

    Who decides
    Each operator or drone, separately
    What they share
    Nothing between drones; only telemetry with its operator
    If a node or link fails
    Its area stays uncovered until a person reassigns it.

    Maturity and example

    Common practice in inspection.

  2. 2

    Fleet coordinated by a controller

    Who decides
    A central planner (station, cloud or fleet software)
    What they share
    State, position, battery and progress with the controller
    If a node or link fails
    If the controller or link fails, each drone finishes its sector or returns; reassignment stops.

    Maturity and example

    Authorised commercial operation: multi-drone solar inspection with software-assigned sectors, and remote BVLOS docks.[vHive, 2025][Skydio]

  3. 3

    Distributed coordination

    Who decides
    The robots themselves, via rules or consensus (leader election, auctions)
    What they share
    State, tasks and coverage map, peer-to-peer over a mesh
    If a node or link fails
    The others reassign the failed node's task if they keep quorum; an isolated minority group cannot.

    Maturity and example

    Mature techniques in distributed systems and ad-hoc networks; we found no documented civil inspection operation with this architecture.[USENIX ATC, 2014][IETF, 2014]

    No documented civil operation

  4. 4

    Cooperating swarm

    Who decides
    Collective behavior emerging from each robot's local rules
    What they share
    Detections and partial maps that change neighbors' actions (confirm a finding, fill a gap)
    If a node or link fails
    Designed to degrade gradually as robots are lost, though its behavior is hard to verify and certify.

    Maturity and example

    Mainly research; the reference literature points out limits to real-world application.[Swarm Intelligence, 2013]

    No documented civil operation

A mesh network only carries data between robots. Collective intelligence exists when what one robot shares (a detection, a gap in the coverage map, its battery) changes what the others do.

04 · Where Physical AI acts

Perceive, reason, decide and act — on each robot and across the fleet

What turns a drone fleet into a Physical AI system is that it closes the loop between what it perceives and what it does, without waiting for a human at every step. That loop exists at two scales, and each degrades differently.

StageOn each robotAcross the fleet
1PerceiveDetect obstacles and anomalies (thermal, visible, LiDAR) with models running onboard.[Skydio, 2023]Fuse detections from several robots into a shared map.
2ReasonEstimate its own position and uncertainty, and judge whether a detection is reliable.Prioritise which findings to confirm and which coverage gaps to fill.
3DecideReplan the route, slow down or return.Reassign tasks by position, battery and sensors.
4ActExecute flight or locomotion control.Dispatch new tasks and create work orders.

Example on a solar plant

  1. 1A drone detects a panel with an abnormal temperature in its thermal image.
  2. 2It estimates the finding's position and confidence and shares it with the fleet.
  3. 3The system sends the nearest drone with a higher-resolution camera to confirm it, without interrupting everyone else's coverage.
  4. 4If confirmed, a work order is created with the location and images.

If the network goes down, each drone keeps its local loop (navigate, avoid obstacles, log findings) and the fleet loop is suspended until contact returns.

05 · Simulator

Try the failures in a teaching model

The simulator shows the coordination logic of an inspection fleet under interference, leader loss and network partition. It is a simplified teaching model, not a reproduction of real protocols or radio propagation. Its assumptions are listed next to it.

Didactic model · simplified simulation14 UAVs · solar plant · fixed seed
Simulated time T+0 s

Scenario

No failures. Each drone sweeps its sector and transmits. Three thermal anomalies are hidden in the panels.

Coordination mode

Cooperative swarm. Leaderless mesh: neighbors share tasks through local auctions; any drone with a ground link acts as gateway.

Starts when you reach this section or press Start.

Legend

  • Drone with a path to deliver data
  • Drone without a path (stores data)
  • Safe mode (no quorum)
  • Lost drone
  • Elected leader
  • Ground station (GCS)
  • Cell with delivered data
  • Cell swept, data on board
  • Orphaned sector
  • Anomaly detected (?) / confirmed (!)
  • Diversion to confirm
  • Interference zone · Links blocked (partition)

Event log

Perception → reasoning → decision → action, plus network events.

  1. No events yet.

What happened and why

The explanation appears when the run ends. You can speed up with ×4.

Same failure, four ways to coordinate · Normal operation

Each row is a complete, deterministic run of the selected scenario, up to 180 simulated seconds, with the same rules and seed. The highlighted row is the one on screen.

  • Independent routes

    Final valid coverage
    100%
    Mission time
    42.6 s
    Orphaned sectors at the end
    —
    Reallocation after failure
    —
    Confirmed anomalies
    0/3 · 3 to manual review
    Detection → confirmation
    —
    Data held on board (peak)
    0%
  • Central controller

    Final valid coverage
    100%
    Mission time
    53 s
    Orphaned sectors at the end
    —
    Reallocation after failure
    —
    Confirmed anomalies
    3/3
    Detection → confirmation
    5 s
    Data held on board (peak)
    0%
  • Distributed coordination

    Final valid coverage
    100%
    Mission time
    53 s
    Orphaned sectors at the end
    —
    Reallocation after failure
    —
    Confirmed anomalies
    3/3
    Detection → confirmation
    5 s
    Data held on board (peak)
    0%
  • Cooperative swarm● On screen

    Final valid coverage
    100%
    Mission time
    53 s
    Orphaned sectors at the end
    —
    Reallocation after failure
    —
    Confirmed anomalies
    3/3
    Detection → confirmation
    5 s
    Data held on board (peak)
    0%

Times in simulated seconds, not real time. “—”: not applicable in this scenario. If you move the interference zone, the on-screen run diverges from this table.

Model assumptions

What this simulation represents and what it leaves out. Read this before drawing conclusions from the numbers.

Nature
Deterministic didactic model (fixed seed, 0.05 s step). It does not reproduce real protocols, radio propagation or flight dynamics, and it is not from an experiment. Its purpose is to compare coordination logics under the same rules.
Connectivity
Share of operational drones with a path to deliver data. Independent and central: direct link to the station. Distributed: one- or multi-hop mesh path to the leader. Swarm: mesh path to any drone with a ground link.
Coverage
We separate area swept (cell overflown) from valid coverage (its data reached the station). A drone without a path stores data on board and forwards it when it reconnects; once its task is done, it heads toward the station to deliver.
Links & interference
Link quality falls with the square of distance (mesh range 300 u., station 900 u.). Interference is a simplified factor: full strength in the inner 60 % of the zone, fading to the edge. Frequency hopping reduces it to 45 %. There is no radio physics.
Leadership
Raft-like election: each drone has a random timeout (1.5–3 s). When it expires without hearing from the leader, the drone runs as candidate and wins if its connected component holds a majority: 8 of the 14 configured members, failed ones included. A leader that loses the majority for 2 s steps down.
No quorum
A minority cannot elect a leader. It enters safe mode: it finishes its already-assigned task, stores data, accepts no new tasks and waits. This prevents two leaders, at the cost of not reacting to the unexpected.
Reallocation
A lost drone is detected after 3 s without heartbeats. The station reallocates in central mode, the leader in distributed mode, and neighbors after a 0.6 s auction in swarm mode. The lowest-cost drone wins: distance × (1 + 0.5 × pending tasks). The sector is redone in full.
Physical AI loop
Perception: when flying over a hot spot, a drone detects it with a fixed confidence (64–78 %). Reasoning: below 90 %, a second pass by another drone is required. Decision: the coordinator picks the lowest-cost drone. Action: that drone diverts, confirms (≥ 96 %) and returns to its lane. Without coordination, the anomaly is left for manual review.
Out of scope
Wind, battery physics and endurance, collisions and separation, real radio propagation, network latency, sensor errors, regulation (BVLOS, U-space) and security. The figures are not performance predictions for any real system.

06 · GNSS-denied navigation

Without satellites, the robot has to estimate its own position

Every localization source has an envelope: conditions where it works and conditions where it fails. Published figures come from benchmarks with specific hardware and environments; they are not performance guarantees at your facility.

Localization sources compared

  • GNSS / RTK

    Low
    Published accuracy
    ~4.9 m (smartphone, open sky) · 1 cm + 1 ppm horizontal with fixed RTK (DJI M350 RTK sheet)[GPS.gov][Norsat][EASA, 2026]
    Drift behavior
    No drift accumulation while the signal is valid
    Where it fails
    Jamming and spoofing, indoors, tunnels, dense urban areas and under foliage
  • Inertial only (IMU)

    Low
    Published accuracy
    No absolute accuracy: error grows with time squared (accelerometer bias) or cubed (gyro bias)[Inside GNSS]
    Drift behavior
    Fast without external aiding
    Where it fails
    Any long mission without another source to bound the error
  • Visual-inertial odometry (VIO)

    Medium
    Published accuracy
    Expressed as % of distance traveled; varies widely by algorithm, onboard computer and environment[IEEE ICRA, 2018][ETH Zürich, 2016]No verifiable general range
    Drift behavior
    Grows with distance; loop closure reduces it at the cost of more compute
    Where it fails
    Low texture, darkness, fog, very fast motion and reflective surfaces
  • LiDAR SLAM

    High
    Published accuracy
    ~0.5% translational error for top KITTI entries (ground vehicle outdoors)[KITTI]
    Drift behavior
    Low; reduced further with loop closure or a prior map
    Where it fails
    Poor geometry (long uniform galleries), dense dust or rain; adds weight and power draw
  • Visual localization against satellite maps

    High
    Published accuracy
    Absolute; depends on altitude, terrain texture, season and map age[arXiv, 2025][arXiv, 2021]No verifiable general range
    Drift behavior
    No drift accumulation when matching succeeds
    Where it fails
    Outdated maps, clouds, night without thermal, uniform terrain (water, desert) and indoors
  • Terrain-referenced navigation (TERCOM-style)

    Low
    Published accuracy
    Limited by relief-map quality and by the terrain itself[USPTO]No verifiable general range
    Drift behavior
    Absolute over terrain with relief
    Where it fails
    Flat terrain; needs an altimeter and an onboard digital elevation model
  • UWB beacons

    Low
    Published accuracy
    ~10 cm with line of sight and calibration[NiceRF]
    Drift behavior
    No drift accumulation within coverage
    Where it fails
    Needs installed infrastructure; multipath and poor anchor geometry

Figures depend on hardware, calibration, altitude, light and environment. Ask vendors for results under conditions equivalent to yours.

Teaching model

Position-estimate drift in a GNSS-denied gallery

A loop of about 520 m. Move the time slider to see how each estimate separates from the true path.

  • True path
  • IMU only (dead reckoning)49.3 m
  • VIO7.3 m
  • VIO + loop closure0.7 m
04080120160 m-4004080Loop closureSTART

Model assumptions

  • Commercial-grade IMU with constant bias: error grows non-linearly with time (integrator physics, not data from a specific unit).
  • VIO with an assumed drift of 1.5% of distance traveled. An illustrative value, not a measured result.
  • Loop closure when revisiting known areas, pulling the estimate back near the true path.
  • No occlusions, no dust and enough texture: in real conditions, VIO can fail entirely.

Teaching model with editorial assumptions (evidence level D). It shows the shape of drift; do not use it to size a system.

07 · Resilient communications

Three layers that reduce the impact of a failure, each with its limits

Communication resilience combines the spectrum, the network topology and the decision logic. No layer removes the risk on its own: know what each one protects against and where it stops helping.

  1. L1 · ESPECTRO

    Spectrum: frequency hopping and selection

    The link changes channel following a shared sequence and avoids bands where it detects noise.

    Protects against

    • Narrowband interference
    • Momentary congestion of a channel

    Limits

    • Does not protect against interference covering all usable bands
    • Available bands depend on national regulation
  2. L2 · MANET

    Topology: multi-hop ad-hoc network

    Every robot also acts as a relay. Standardised routing protocols such as OLSRv2 recompute routes when a link drops; data can be stored onboard and forwarded when contact returns.[IETF, 2014][IETF, 2022]

    Protects against

    • Loss of individual links
    • Robots beyond the station's direct range

    Limits

    • Reduces single points of failure but does not remove them: if a bridge node fails, the network splits
    • Recovery time depends on the control-message configuration
    • Store-and-forward does not guarantee delivery
  3. L3 · CONSENSO

    Decision: leader and tasks by consensus

    With consensus algorithms such as Raft, a candidate needs a majority of votes to become leader. If the network splits, the minority group cannot elect a leader: a deliberate safety limit that prevents two leaders issuing contradictory orders.[USENIX ATC, 2014]

    Protects against

    • Leader failure while a majority remains
    • Contradictory orders after a partition

    Limits

    • A partition without a majority halts coordination in that group
    • Tasks must be designed to be safe without coordination

08 · Operational lessons & civil maturity

What hostile environments have taught, and what is already proven in civil use

Recent conflicts have accelerated technologies the civil sector can use. We separate two things: the publicly documented lesson and the demonstrated maturity of a specific civil system. Where no civil system has documented operation, we say so.

Key transfer

  • Multi-drone coordinationSolar farms & forestsTRL 9
  • GNSS-free navigation (VIO/SLAM)Underground mining & tunnelsTRL 9
  • Low-latency first-person (FPV) pilotingDisaster search & rescueNo sufficient public evidence
Context
Civil application

7/7 technologies

  1. Multi-drone coordination

    ★ Key transfer: Solar farms & forests

    Several drones sharing a mission, with task allocation and reassignment on failure.

    USASolar farms & forestsAgricultural monitoringDisaster search & rescue

    Demonstrated civil maturity

    Demonstrated civil maturity: TRL 9

    Multi-drone solar inspection with software-assigned sectors (vHive, FAA waiver, 2025). This is central coordination, not a decentralised swarm.[vHive, 2025]

    Decentralised swarms in civil inspection: we found no documented operation.

  2. GNSS-free navigation (VIO/SLAM)

    ★ Key transfer: Underground mining & tunnels

    Estimating position from cameras, IMU and LiDAR when satellites are unavailable or unreliable.

    RussiaUnderground mining & tunnelsCritical infrastructure

    Demonstrated civil maturity

    Demonstrated civil maturity: TRL 9

    LiDAR SLAM drone in a coal mine (Elios 3 at LW Bogdanka), documented in a technical publication.[E3S Web of Conferences, 2024]

  3. Low-latency first-person (FPV) piloting

    ★ Key transfer: Disaster search & rescue

    Agile manual control with low-latency video to maneuver in complex spaces.

    UkraineDisaster search & rescueCritical infrastructureUnderground mining & tunnels

    Demonstrated civil maturity

    Demonstrated civil maturity: TRL 9

    Assisted piloting in confined spaces with a caged drone (Elios 3 in a mine).[E3S Web of Conferences, 2024]

    FPV use in search and rescue: we found no public evaluation of results.

  4. Fiber-optic control links

    The drone receives commands over an unspooling fiber cable: it emits no radio and is unaffected by jamming.

    UkraineRussiaUnderground mining & tunnelsCritical infrastructure

    Demonstrated civil maturity

    No sufficient public evidence

    We found no documented civil deployments with unspooling fiber. Tethered drones are a different technology.

  5. Visual localization against maps

    Matching the camera image against onboard satellite maps to obtain an absolute position without GNSS.

    RussiaAgricultural monitoringDisaster search & rescueLong-range logistics

    Demonstrated civil maturity

    No sufficient public evidence

    Recent literature is mostly research prototypes; we found no documented civil operation.

  6. Mass production and fast iteration cycles

    Simple designs built in volume with commercial components and frequently updated software.

    IranUSALong-range logisticsAgricultural monitoringCritical infrastructure

    Demonstrated civil maturity

    Demonstrated civil maturity: TRL 9

    Civil autonomous operation at scale: medical and retail logistics with over 2 million deliveries (Zipline, company figures). It does not derive from these programs.[DroneLife, 2026]

  7. Docked drones and remote BVLOS operation

    Autonomous stations that launch, recharge and recover the drone, operated remotely.

    USAPerimeter securityCritical infrastructureDisaster search & rescue

    Demonstrated civil maturity

    Demonstrated civil maturity: TRL 9

    BVLOS docks at dozens of a utility's facilities (Skydio with Dominion Energy, 2022, per the manufacturer).[Skydio]

TRL is assigned to a specific system, not to a technology category, using NASA's scale (9 = actual system proven through successful operations). The assignment is ours, based on the cited evidence.[NASA]

High-level analysis from public sources, focused on civil applications. It contains no operational or employment detail.

09 · Regulatory framework (EU)

Which regulatory route applies to your operation

In the EU, an operation's category depends on its risk. Most professional BVLOS inspections fall into the specific category, which has several access routes with different requirements.

  1. UE 2019/947

    Three risk-based categories

    Open: low risk, with height, weight and visual-line-of-sight (VLOS) limits; no prior authorisation. Specific: higher-risk operations, such as most professional BVLOS. Certified: risk comparable to crewed aviation (e.g., carrying people).[EUR-Lex, 2019]

  2. STS

    Standard scenario: declaration

    If the operation fits an EASA standard scenario (STS-01 and STS-02), a declaration to the authority is enough, with no prior authorisation. The scenario's conditions and the matching equipment class are required.[EASA][Transpordiamet]

  3. PDRA · SORA

    Authorisation: PDRA or SORA

    If it does not fit an STS, an authorisation is requested. A PDRA is a scenario already assessed by EASA with defined mitigations, simplifying the application. If no PDRA fits either, a full SORA risk assessment is done; its risk level drives the link, containment and contingency-procedure requirements.[EASA]

  4. LUC

    LUC certificate: self-approval

    The light UAS operator certificate (LUC) lets an organisation with a mature management system approve its own operations within the granted privileges. It is the route to scale many operations without requesting an authorisation for each one.[EASA][Luftfartstilsynet]

  5. UE 2021/664

    U-space

    Framework to designate U-space airspace with digital services for drones, such as network identification, geo-awareness and flight authorisation. Its rollout depends on each state designating such airspace.[EUR-Lex, 2021]

  6. UE 2024/1689

    AI Act and aviation

    For civil aviation, the AI Act acts mainly through EASA rules: aviation acts on AI systems that are safety components must take the high-risk requirements into account. Exclusively military systems are outside its scope.[EASA, 2024][SpringLex]

  7. UE 2021/821

    Dual-use exports

    Items on the Annex I list need a licence for export outside the EU. Check the classification of navigation, communications and encryption hardware and software before selling or transferring.[EUR-Lex, 2021]

Informational summary as of November 2026; not legal advice. Always check the consolidated text and your national authority.

10 · Platforms

Aerial platforms related to these applications

Open a sheet to see specifications with their conditions and sources.

Dual-use ground platforms (e.g., THeMIS or Vision 60) are in the explorer, under ground vehicles and quadrupeds. See ground platforms →