Low-pass filter

Simple low-pass filter.

Collaboration diagram for Low-pass filter:

A filter that filters out high frequencies and keep the lower frequencies. \( \dot y = \frac{1}{\tau}(u(t) - y(t)) \).

Author

Karl-Johan Reite

Example configuration excerpt

<Lib
  LibName="fhsim_base"
  SimObject="Math/LowPass"
  Name="F"
  ConvergenceRatio="0.0185"
  PortWidth="1"
/>
...
<Connection
  F.In="A.Sine" <!-- From somewhere else -->
/>

Input Ports

Name	Width	Description
In	<PortWidth>	The input port, \(u\)

Output Ports

Name	Width	Description
Out	<PortWidth>	The value of the low pass filtered input ("In"), \(y\)

Configuration parameters

Name	Width	Description
PortWidth	1	The number of elements in the signal.
ConvergenceRatio	1 or <PortWidth>	The convergence ratio \( r = \frac{1}{\tau}\). If the parameter size is 1, the same ratio is used for all elements.

Initial conditions

Name	Width	Description
FilteredValue	<PortWidth>	The filter state. Optional: when it is not given in the model it is seeded from the value of In at TStart, so the filter starts converged on its input.

Full example file

<Contents>
  <OBJECTS>
 
    <Lib
           LibName="base"
           SimObject="Math/LowPass"
           Name="F"
           ConvergenceRatio="0.0185"
           PortWidth="1"
    />
 
    <Lib
        LibName="base"
        SimObject="Src/Sine"
        Name="A"
        FHz="4000"
        PhaseRad ="0"
    />
 
  </OBJECTS>
 
  <INTERCONNECTIONS>
    <Connection
      F.In="A.Out"
    />
  </INTERCONNECTIONS>
 
  <INITIALIZATION>
    <InitialCondition
    />
  </INITIALIZATION>
 
  <SIMULATION>
    <Timing TStart="0" TEnd="0.015"/>
    <Integrator Method="RK45_i" NumCores="1" LogStates="1" UseRSSNorm="0">
      <StepControl Step="0.00001" StepMax="0.002" StepMin="0.00000001" AbsTol="1e-3" RelTol="1e-3"/>
    </Integrator>
    
  </SIMULATION>
 
<OBSERVERS>
    <FileOutput TOutput="0, 0:00001:0.01, 0.02" Select="objects:all"/>
  </OBSERVERS>
</Contents>

This SimObject is referred to as Math/LowPass