Samplifier

Sample and hold.

Collaboration diagram for Samplifier:

Author

Joakim Haugen

Samplifier is a SimObject that samples the input signals in a sample-and-hold fashion. It can simulate a variety of real-world properties in the sampled signal. The following things can be configured to happen with the output signals:

• Time delay, the output signal is delayed in comparison to the input.
• Outliers, singular samples with large peaks.
• Loss of signal for a time period, Not-a-Number is sent.
• Normally distributed noise with specified mean (bias) and standard deviation added to the input signal.

The random draws use std::normal_distribution and std::uniform_real_distribution on a std::mt19937 seeded with NoiseSeed. The engine is portable, but the standard leaves the distributions' transforms to the library, so a given NoiseSeed reproduces the same sequence with one standard library only. Other libraries give a different sequence with the same statistics.

Example configuration excerpt

<Lib
     LibName            = "fhsim_base"
     SimObject          = "Signal/Samplifier"
     Name               = "Sample"
     PortWidth          = "1"
     NoiseSeed          = "42"
     Tags               = "OutVector1"
     SamplingPeriod1    = "1, 1, 1"
     FirstSampleTime1   = "0.9999,0.9999,0.9999"
     TimeDelay1         = "0, 0, 0"
     OutlierProbability1= "0, 0, 0.01"
     LossProbability1   = "0, 0, 0.1"
     AvgLostSamples1    = "0, 0, 3"
     NoiseBias1         = "0, 0, 0.1"
     NoiseStdDev1       = "1, 1, 2"
/>

Input Ports

Name	Width	Description
In1 .. In<PortWidth>	n_i	Vector inputs. The dimension of each input is inferred from the configuration parameter's dimension.

Output Ports

Name	Width	Description
Out1 .. Out<PortWidth>	n_i	Vector outputs samplified.
<Tags>	<PortWidth>	Named outputs (Optional).

Configuration parameters

Name	Width	Description
NoiseSeed	0 or 1	Seed number for random generator (Optional).
PortWidth	1	Number of std::vector input signals.
Tags	<PortWidth> or 0	Named output ports (Optional).
SamplingPeriod<1..PortWidth>	n_i	List of positive sampling periods.
FirstSampleTime<1..PortWidth>	n_i or 0	List of first available sample times. Note that the sample will be available on the first time step after the sampling instant. Default is \(-\infty\).
TimeDelay<1..PortWidth>	n_i or 0	List of non-negative time delays. Default is zeros.
OutlierProbability<1..PortWidth>	n_i or 0	List of probabilities for outliers. Default is zeros.
LossProbability<1..PortWidth>	n_i or 0	List of probabilities for loss of signal. Default is zeros.
AvgLostSamples<1..PortWidth>	n_i or 0	List of average number of lost signals (when loss). Default is zeros.
NoiseBias<1..PortWidth>	n_i or 0	List of bias (mean) for each noisy output. Default is zeros.
NoiseStdDev<1..PortWidth>	n_i or 0	List of standard deviations. Default is zeros.

Initial conditions

Name	Width	Description
SamplifierDummy	1	Internal placeholder state with zero derivative. It carries no meaning, is set to 0 by InitialConditionSetup, and need not be given in the model.

Full example file

<Contents>
  <OBJECTS>
    <Lib
        LibName            = "fhsim_base"
        SimObject          = "Signal/Samplifier"
        Name               = "S"
        PortWidth          = "1"
        NoiseSeed          = "42"
        Tags               = "OutVector1"
        SamplingPeriod1    = "1, 1, 1"
        FirstSampleTime1   = "0.9999,0.9999,0.9999"
        TimeDelay1         = "0, 0, 0"
        OutlierProbability1= "0, 0, 0.01"
        LossProbability1   = "0, 0, 0.1"
        AvgLostSamples1    = "0, 0, 3"
        NoiseBias1         = "0, 0, 0.1"
        NoiseStdDev1       = "1, 1, 2"
    />
    <Lib
        LibName     = "fhsim_base"
        SimObject   = "Src/Random"
        Name        = "R"
        PortWidth   = "3"
        RandomType  = "VariableRandom"
        RandomMin   = "0.2, 0.2, 0.2"
        RandomMax   = "1.2, 1.2, 1.2"
    />
  </OBJECTS>
 
  <INTERCONNECTIONS>
    <Connection
        S.In1 = "R.Out"
    />
  </INTERCONNECTIONS>
 
  <INITIALIZATION>
    <InitialCondition
    />
  </INITIALIZATION>
 
  <SIMULATION>
    <Timing TStart="0" TEnd="30"/>
    <Integrator Method="RK45_i" NumCores="1" LogStates="1" UseRSSNorm="0">
      <StepControl StepMax="0.002" StepMin="0.00000001" AbsTol="1e-3" RelTol="1e-3"/>
    </Integrator>
  </SIMULATION>
</Contents>

This SimObject is referred to as Signal/Samplifier