Module: tempMeasurement

Executive Summary

Models the addition of noise, bias, and faults to temperature measurements.

Message Connection Descriptions

The following table lists all module input and output messages. The module msg connection is set by the user from python. The msg type contains a link to the message structure definition, while the description provides information on what this message is used for.

Module I/O Messages

Msg Variable Name

Msg Type

Description

tempInMsg

TemperatureMsgPayload

True temperature measurement

tempOutMsg

TemperatureMsgPayload

Sensed temperature measurement with corruptions

Detailed Module Description

This module simulates the corruption of a true thermal measurement by noise, bias, and three faults:

  • TEMP_FAULT_STUCK_VALUE is faulty behavior where the measurement sticks to a specific value

  • TEMP_FAULT_STUCK_CURRENT fixes the measurement to the value

  • TEMP_FAULT_SPIKING is faulty behavior where the measurement spikes to a specified multiplier times the actual value, with a given probability

  • TEMP_FAULT_NOMINAL has no faulty behavior but may still have noise and bias

User Guide

Fault Parameters

This module has several parameters that are set to default values:

Default Module Parameters

Parameter

Description

Default Value

faultState

Sets the fault status.

TEMP_FAULT_NOMINAL

senBias

Sets the bias value.

0.0

senNoiseStd

Sets the standard deviation for sensor noise.

0.0

walkBounds

Sets the random walk bounds for sensor noise.

1E-15

stuckValue

Temperature at which the reading is stuck for fault mode TEMP_FAULT_STUCK_VALUE.

0.0

spikeProbability

Probability of a spike when in fault mode TEMP_FAULT_SPIKING. Between 0 and 1.

0.1

spikeAmount

Sensed temperature multiplier when spiking for fault mode TEMP_FAULT_SPIKING.

2.0

Module Setup

The module is created in python using, for example:

1tempMeasurementModel = tempMeasurement.TempMeasurement()
2tempMeasurementModel.ModelTag = 'tempMeasModel'

A sample setup is done using:

1tempMeasurementModel.senBias = 1.0  # [C] bias amount
2tempMeasurementModel.senNoiseStd = 5.0  # [C] noise standard devation
3tempMeasurementModel.walkBounds = 2.0  #
4tempMeasurementModel.stuckValue = 10.0  # [C] if the sensor gets stuck, stuck at 10 degrees C
5tempMeasurementModel.spikeProbability = 0.3  # [-] 30% chance of spiking at each time step
6tempMeasurementModel.spikeAmount = 10.0  # [-] 10x the actual sensed value if the spike happens

The incomping temperature message must be connected to the module:

1tempMeasurementModel.tempInMsg.subscribeTo(sensorThermalModel.temperatureOutMsg)

The fault state is changed by the user to spiking, for example, by setting:

1tempMeasurementModel.faultState = tempMeasurement.TEMP_FAULT_SPIKING

Enums

enum TempFaultState_t

Values:

enumerator TEMP_FAULT_STUCK_CURRENT

temp measurement is set to current value for all future time

enumerator TEMP_FAULT_STUCK_VALUE

temp measurement is set to specified value for all future time

enumerator TEMP_FAULT_SPIKING

temp measurement has a probability of spiking at each time step

enumerator TEMP_FAULT_NOMINAL
class TempMeasurement : public SysModel
#include <tempMeasurement.h>

Models a sensor to add noise, bias, and faults to temperature measurements.

Public Functions

TempMeasurement()

This is the constructor for the module class. It sets default variable values and initializes the various parts of the model. Don’t allow random walk by default.

~TempMeasurement()
void Reset(uint64_t CurrentSimNanos)

This method is used to reset the module and checks that required input messages are connected.

Returns:

void

void UpdateState(uint64_t CurrentSimNanos)

This is the main method that gets called every time the module is updated.

Returns:

void

Public Members

ReadFunctor<TemperatureMsgPayload> tempInMsg

True temperature measurement.

Message<TemperatureMsgPayload> tempOutMsg

Sensed temperature measurement.

BSKLogger bskLogger

&#8212; BSK Logging

TempFaultState_t faultState

[-] Fault status variable

double senBias = {}

[-] Sensor bias value

double senNoiseStd = {}

[-] Sensor noise value

double walkBounds

[-] Gauss Markov walk bounds

double stuckValue = {}

[C] Value for temp sensor to get stuck at

double spikeProbability

[-] Probability of spiking at each time step (between 0 and 1)

double spikeAmount

[-] Spike multiplier

Private Functions

void applySensorErrors()

This method adds noise, bias, and fault behaviors to the read-in temperature message.

Returns:

void

Private Members

double trueTemperature = {}

[C] Truth value for the temperature measurement

double sensedTemperature = {}

[C] Temperature measurement as corrupted by noise and faults

double pastValue = {}

[-] Measurement from last update (used only for faults)

std::minstd_rand spikeProbabilityGenerator
GaussMarkov noiseModel

[-] Number generator for calculating probability of spike if faulty