Simulation Profiles

Every device type can ship an optional simulation.yaml alongside its manifest.yaml. The file is a declarative, data-driven description of how the device behaves — sensor readings ramp and lag, derived values are computed, disturbances add noise, and failure modes describe injectable faults. A data-driven simulator reads the profile and ticks the device forward in time — deterministic simple dynamics models overlaid with stochastic disturbance noise — so you can exercise the UI, alarms, historian, and AI advisory tools without a single piece of field hardware.

Profiles are authored as part of creating a device type and reference the same tags declared in the type’s manifest — see Tags for tag dataType, access, and physicalRole.

Note

The format originates in the platform’s original two-mode simulation design. That design was later reframed so simulation is a per-device activity rather than a platform-wide “mode”, while the simulation.yaml format itself was kept unchanged. The file you author today is that format; the modes described below are ways a device’s simulation runs, not a platform-wide switch you flip.

The ownership split: inputs vs outputs

The most important architectural rule is what the simulator is allowed to write.

• The simulator owns physical-input tags — sensor readings and external signals, i.e. tags whose manifest physicalRole is Input — plus any simulator-only Internal tags a type declares for the physical model’s own consistency.
• Output tags are owned by the vPLC control logic (physicalRole: Output). They are written by the function-block scan — Running, Speed, Fault, FaultCode, LocalMode, AutoMode and the like — and the profile must never write them.

A profile’s expressions may read output tags (for example, the centrifugal pump’s MotorCurrent steady state is "Speed / 3600 * 85", where Speed is read from the vPLC tag cache), but it only writes the input tags it declares. This keeps the simulator and the control logic cleanly separated: the vPLC decides what the equipment does, and the simulator supplies the physics the equipment’s sensors would report back.

graph LR
  SIM[Device simulator<br/>simulation.yaml] -->|writes Input tags<br/>MotorCurrent, BearingTemp,<br/>FlowRate, Level| CACHE[Tag cache]
  VPLC[vPLC control logic<br/>function-block scan] -->|writes Output tags<br/>Running, Speed, Fault| CACHE
  CACHE -->|Speed read back into<br/>sim expressions| SIM
  CACHE -->|source_class = simulated| HIST[Historian]

Caution

The enforced rule is must not be Output: a profile may write Input tags (and simulator-only Internal tags), but writing an Output tag from simulation.yaml is rejected by the profile validator (simulator-writes-output-tag) — the control logic owns those tags and would fight the simulator for them.

File structure

The header identifies the profile and pins it to a device-type version range:

schemaVersion: 1
deviceType: consystence.pump.centrifugal
deviceTypeVersion: ">=1.0.0"

Key	Meaning
schemaVersion	Profile schema version (currently 1).
deviceType	The dot-id of the type this profile drives (must match the manifest).
deviceTypeVersion	Semver range the profile is valid for, e.g. ">=1.0.0".

The remaining sections — all optional — are described below. In practice you almost always want initialValues, so input tags start from sensible values rather than zero.

initialValues

Seeds the input tags at start-up. Input tags only — output-tag initial state comes from the vPLC function block’s initialisation, not from here.

initialValues:
  SpeedSetpoint: 75
  MotorCurrent: 0
  BearingTemp: 32
  FlowRate: 0
  DischargePressure: 0
  Interlock: false

stateScopedDynamics

The core physics. Each entry binds a model to a single tag, scoped to a named device state (e.g. Running, Stopped, Opening, Closed).

stateScopedDynamics:
  - state: Running
    tag: MotorCurrent
    model: firstOrderLag
    parameters:
      steadyState: "Speed / 3600 * 85"   # 85 A at rated 3600 rpm
      timeConstant: 0.5
  - state: Stopped
    tag: MotorCurrent
    model: firstOrderLag
    parameters:
      steadyState: 0
      timeConstant: 0.5

State scoping is not yet evaluated at runtime

The simulator does not yet evaluate the state field — every stateScopedDynamics entry runs on every tick, whatever state the device is in (wiring the manifest’s state machine into the simulator is on the roadmap). To condition a dynamic today, use the optional activeWhen gate: an expression evaluated each tick that must be truthy for the entry to run, e.g. activeWhen: "Running == 0" on the Stopped entry above. Without it, two entries targeting the same tag both execute each tick and fight over the value.

Models

The v1 schema defines a fixed library of eight named models (adding one requires a schema version bump):

Model	Parameters	Behaviour
firstOrderLag	steadyState, timeConstant (seconds)	Tag relaxes exponentially towards steadyState with the given time constant.
secondOrderUnderdamped	steadyState, naturalFrequency (rad/s), dampingRatio	Second-order response towards steadyState — overshoot and ringing when the damping ratio is below 1.
integrator	gain, inputExpression	Accumulates gain × input per second — levels, totals, run-hours.
deadTime	delay (seconds), sourceExpression	Replays the source value after a fixed transport delay.
rateLimit	target, rate (units/second)	Tag moves towards target at a constant rate (used for valve Position towards PositionSetpoint).
hysteresis	inputExpression, upperThreshold, lowerThreshold, outputHigh, outputLow	Latches to outputHigh when the input crosses the upper threshold, back to outputLow below the lower — deadband switching.
saturation	inputExpression, min, max	Clamps the input expression into [min, max].
lookupTable	inputExpression, points (list of [x, y] pairs)	Piecewise-linear interpolation over the points — pump curves and other characteristic maps.

Numeric parameters such as steadyState and target accept either a literal or an expression (see below), so steady states can track other tags — "32 + 28 * (Speed / 3600)" for bearing temperature, or "(Speed / 3600) * (Speed / 3600) * 4.5" for a head-curve discharge-pressure approximation.

These are deliberately simple lumped models — the shipped pump-library profiles restrict themselves to firstOrderLag and rateLimit. That fidelity is sufficient for demos, development, and training; the platform intentionally avoids a Simulink-grade physics dependency.

Expressions

Expressions are arithmetic over tag names and constants, evaluated every tick. They support the usual operators, a ternary, and helpers such as abs(...):

# motorised valve — limit switches and motion booleans derived from position
algebraicRelations:
  - tag: OpenLimit
    expression: "Position >= 98 ? 1 : 0"
  - tag: ClosedLimit
    expression: "Position <= 2 ? 1 : 0"
  - tag: Moving
    expression: "abs(PositionSetpoint - Position) > 1 ? 1 : 0"

algebraicRelations

Pure, stateless derivations recomputed each tick from current tag values. Use these for engineering conversions and derived readings. The level sensor derives a scaled raw value and a tank volume:

algebraicRelations:
  - tag: RawValue
    expression: "(Level - RangeMin) / (RangeMax - RangeMin) * 100"
    unit: "%"
  - tag: Volume
    expression: "Level / 100 * TankCapacity"
    unit: "m3"

behaviours

Event-driven effects triggered by tag transitions — for example, freezing motion booleans when a Fault rises:

behaviours:
  - trigger:
      tag: Fault
      condition: rising
    effects:
      - tag: Moving
        action: setTo
        value: false
      - tag: Opening
        action: setTo
        value: false

Note

Behaviours that drive state-machine transitions (e.g. “fault → stop running”) belong in the vPLC control logic, not the profile — those touch output tags. The centrifugal pump profile deliberately removed its old Fault → Running=false rule for exactly this reason.

disturbances

Adds realistic measurement noise to a tag. Today’s profiles use band-limited white noise with an amplitude:

disturbances:
  - tag: MotorCurrent
    type: white
    amplitude: 2.0
  - tag: BearingTemp
    type: white
    amplitude: 0.3

failureModes

Named fault definitions for testing alarms, AI explanations, and operator response. Each mode lists the tags it affects and how:

failureModes:
  - id: bearing-degradation
    description: Progressive bearing wear; temperature rise.
    severity: warning
    affects:
      - tag: BearingTemp
        type: bias
        offset: 15
  - id: sensor-stuck
    description: Level transmitter stuck at last good reading.
    severity: fault
    affects:
      - tag: Level
        type: stuckAt
        value: lastValueWhenFaultActivated
      - tag: Status
        type: setTo
        value: 3

Affect types seen across the shipped profiles include bias (offset), stuckAt (value, often lastValueWhenFaultActivated), drift (rate), setTo (value), and dropout (probability, durationSeconds); the schema also defines a sixth, noise (amplitude), that no shipped profile uses yet. severity is informational, warning or fault (shipped profiles use only the latter two). A failure mode may target tag: "*" to affect all of the device’s tags (e.g. an intermittent comms dropout), and an optional progressTo names another failure mode in the profile that this one cascades into.

Failure-mode injection has not shipped yet

Failure modes are schema-validated today, but there is no runtime activation surface — no API, CLI command or scenario action injects them, and the simulator’s tick does not apply failure-mode effects (activation is on the roadmap). Declare them for validation and forward-compatibility.

processCouplings

Couples a device’s output into a site-level process, so one device’s behaviour can feed another’s inputs (a pump’s flow feeding a downstream tank’s level, for example). The profile declares the named value the device publishes; the site’s coupling graph routes it.

processCouplings:
  - output: FlowRate
    expression: FlowRate
    requires: [Running]
    publishesTo: pumpFlowOutput

Profile couplings are not yet consumed at runtime

The processCouplings section is validated but not yet read by the simulator — publishesTo publication is on the roadmap. Today, cross-device coupling is authored per site in a simulation-config.yaml, which routes a source instance’s tag into a target instance’s tag after each tick, optionally through a transform expression:

couplings:
  - sourceInstanceId: dev_K7M2P9QX   # pump flow → flow sensor PV
    sourceTag: FlowRate
    targetInstanceId: dev_3F8T1N6B
    targetTag: PV
  - sourceInstanceId: dev_3F8T1N6B   # net flow integrates dam level
    sourceTag: PV
    targetInstanceId: dev_9W4D2R7S
    targetTag: Level
    expression: "{tags.Level} + (80 - {value}) / 5000 * 1.0"

Wiring a new device into the site process therefore does mean editing that site-level file for now; profile-declared couplings are the target model that removes the step.

How a profile is driven at runtime

A site-scoped simulation coordinator owns the simulation lifecycle and drives a timer-based tick (1 second by default). On each tick it advances every simulated device’s ramps and dynamics, evaluates algebraic relations, then overlays disturbance noise last (an emit-only overlay — derived tags are computed from the un-noised values), and finally resolves cross-device couplings at the site level. Changed tags flow through state evaluation and alarm processing exactly as live readings do — that is the whole point: the UI, alarms, and historian cannot tell a simulated reading from a real one, except by provenance.

The original design framed this as two modes, both of which reuse the same profile format. Both exist today:

• PLC-in-the-loop (edge) — the simulator writes simulated input values into a controller’s input variables through the edge, so the controller’s own logic runs against simulated inputs. The controller’s outputs are driven by that logic, as they are in normal running, so this mode is for bench and virtual controllers that are not connected to plant. It is off by default on every edge and limited to the controllers that edge’s configuration allows. Starting it is a plant write, so only a site where Consystence is the operator surface admits it, and a display-only site refuses it. Simulation switching inside the Standard Library IO module blocks, within the controller scan, is the planned successor (roadmap). See PLCnext border gateway and controller communication.
• Full server simulation — runs entirely in the server Orleans cluster with no edge or PLC required. Used for demos, development, and offline work.

These collapse into one model: simulation is a per-device activity inside whatever deployment topology the device sits in, so mixed-state operation — some devices real, some simulated — is a natural consequence rather than a special case.

Reaching the historian

Simulated tag changes are persisted through the normal historian path and tagged with a provenance marker (source_class = simulated) so that simulated samples are distinguishable from live field data downstream. Queries and dashboards can therefore include or exclude simulated history explicitly.

Note

Simulation profiles run today on a demonstration site we operate on the hosted service, and in our workshop. Simulations resume automatically after platform restarts.

AI is advisory-only

Simulation is a safe way to exercise AI tools, because the AI tier only reads, explains and recommends — it never commands equipment. Even against a simulated device, no AI output drives a control write; the vPLC control logic and hard interlocks remain the only things that move outputs. See AI architecture.

Next steps

• Creating device types — where simulation.yaml lives in the type bundle.
• Tags — physicalRole, dataType, and access, which decide what a profile may write.
• Engineering model — controller → module → channel → tag, the structure simulated tags belong to.