Generators

Give a member a generator when its value should change at runtime instead of staying fixed.

Technical detailsCopy Anchor Link

Generator familiesCopy Anchor Link

• Source generators produce a value on their own: sine, noise, random-walk, step, ramp, mean-reverting-noise, timetable, state-machine, waveform, chirp, impulse.
• Transformers build on another member, a previous-tick value, a parameter, or an input port: first-order-lag, integrator, transport-delay, slew-rate-limiter, second-order, hysteresis-relay, weighted-sum, expression, gate.
• Context-aware generators derive from another signal or switch by lifecycle stage. correlated couples a member directly to another. health-dependent gives each lifecycle stage its own source generator.

Where a generator reads its inputCopy Anchor Link

generator:
  type: first-order-lag
  tau: 30
  input: { member: "speed_feedback" }

Write an expressionCopy Anchor Link

Use expression when the value is a formula over other values and weighted-sum would need nested terms. Miravo parses the expression once at load and evaluates it every tick. It never calls eval. The language supports numbers, + - * /, unary minus, parentheses, min(a, b, ...), max(a, b, ...), and clamp(x, lo, hi).

generator:
  type: expression
  expression: "max(0, $param.design_load_kw * (18 - outdoor_temperature) / (18 - $param.design_outdoor_temp_c))"
  min: 0
  max: 6000

Names use letters, digits, and underscores, so a-b is a subtraction. Booleans read as 0 and 1. A result that is not finite, such as a division by zero, raises an error. Guard denominators with max(..., 0.001). The min and max fields clamp the result and accept numbers or $param expressions. Load-time validation checks syntax, that members, parameters, and ports exist, and member order.

Build a chainCopy Anchor Link

speed_setpoint:
  kind: variable
  data_type: Double
  access: readwrite
  unit: rpm
  generator:
    type: timetable
    repeat: true
    interpolation: step
    points:
      - { time: 0, value: 0 }
      - { time: 21600, value: 1200 }
      - { time: 64800, value: 900 }

speed_feedback:
  kind: variable
  data_type: Double
  access: read
  unit: rpm
  generator:
    type: slew-rate-limiter
    input: { member: "speed_setpoint" }
    rate_up: 220
    rate_down: 320
    min: 0
    max: 1850

Rates and durationsCopy Anchor Link

• state-machine transitions take an optional rate_per_hour. Without it, the transition is unconditional. A transition with on: fault fires only while the asset has an active fault.
• impulse takes either rate_per_hour or interval (simulated seconds), plus duration_s and a decay factor per simulated second.
• Rates use p = 1 - exp(-rate_per_hour * dt / 3600) per step.
• random-walk increments scale by sqrt(dt), so variance follows simulated time.
• noise draws an independent sample on every evaluation. It is not an event rate. For time-correlated variation, use mean-reverting-noise.
• With substeps, previous_member inputs read the previous substep.

Start at a parameter valueCopy Anchor Link

The initial_value of first-order-lag, second-order, integrator, and slew-rate-limiter accepts a number or a $param expression, resolved on the first tick. A lag with initial_value: "$param.supply_temp_setpoint_c" starts at its setpoint instead of climbing to it, so a plant that is already running starts in steady state.

ReferenceCopy Anchor Link

Parameters by generatorCopy Anchor Link

Key parameters, one generator per row. Transformers and gate also take an input.

$param coefficientsCopy Anchor Link

These fields accept a $param expression instead of a number: center (sine, noise, waveform, chirp), mean (mean-reverting-noise), factor and offset (correlated), initial_value, gain, and bias (first-order-lag and second-order), initial_value and gain (integrator), initial_value (slew-rate-limiter), delay (transport-delay), the thresholds of hysteresis-relay, the bias, weights, min, and max of weighted-sum, and the min and max of expression.

A $param field is an expression over numbers and $param.X only. It supports + - * /, parentheses, min, max, and clamp. Examples: factor: "$param.rated_voltage_v / $param.rated_frequency_hz" or max: "($param.rated_frequency_hz + 2) * 1.01". Miravo evaluates it once per asset, so it rejects member, $prev, and $port references at load. Use an expression generator for those.

Observation effectsCopy Anchor Link

Generators and faults define the process truth. Observation effects then distort what a sensor reports, the way a real instrument would. Declare them in observation_effects on a numeric read variable. Relative parameters use the member's eu_range span as the scale, or an explicit scale on the effect.

Declare white_noise, drift, outlier, and noise_burst first, in any order. Then quantize, then deadband and stuck. The schema rejects other orders. miravo lint warns when a quantize step exceeds 1% of the eu_range span or a deadband exceeds 5%. See Asset models for a full member example.

Related pagesCopy Anchor Link