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Add new integral function block for determining approximate integral over time. #648

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Add new integral function block for determining approximate integral over time. #648

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56 changes: 56 additions & 0 deletions data/typelibrary/utils-1.0.0/typelib/math/INTEGRAL.fbt
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<?xml version="1.0" encoding="UTF-8"?>
<FBType Name="INTEGRAL" Comment="determines approximately the integral over time.">
<Identification Standard="61499-1" Description="Copyright (c) 2024 HR Agrartechnik GmbH &#10; &#10;This program and the accompanying materials are made&#10;available under the terms of the Eclipse Public License 2.0&#10;which is available at https://www.eclipse.org/legal/epl-2.0/&#10;&#10;SPDX-License-Identifier: EPL-2.0&#10;&#10;This Block was inspired by &#10;https://content.helpme-codesys.com/en/libs/Util/Current/Mathematical-Functions/INTEGRAL.html&#10;" >
</Identification>
<VersionInfo Organization="HR Agrartechnik GmbH" Version="1.0" Author="Franz Höpfinger" Date="2024-10-18" Remarks="initial Version">
</VersionInfo>
<CompilerInfo packageName="utils::math">
</CompilerInfo>
<InterfaceList>
<EventInputs>
<Event Name="REQ" Type="Event" Comment="Normal Execution Request">
<With Var="IN"/>
<With Var="TM"/>
</Event>
<Event Name="RESET" Type="Event" Comment="TRUE: OUT is set to zero and OVERFLOW to FALSE">
</Event>
</EventInputs>
<EventOutputs>
<Event Name="CNF" Type="Event" Comment="Execution Confirmation">
<With Var="OUT"/>
<With Var="OVERFLOW"/>
</Event>
</EventOutputs>
<InputVars>
<VarDeclaration Name="IN" Type="REAL" Comment="Input value" InitialValue="0.0"/>
<VarDeclaration Name="TM" Type="DINT" Comment="Time since last call in msec" InitialValue="0"/>
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I would prefer TM to have type TIME to better indicate the meaning of this value. But I fully understand the implications this has on the integration as soon as people start to use values in nanoseconds...

</InputVars>
<OutputVars>
<VarDeclaration Name="OUT" Type="REAL" Comment="Value of the integral. This is done by summing all part integrals IN * TM" InitialValue="0.0"/>
<VarDeclaration Name="OVERFLOW" Type="BOOL" Comment="TRUE: The value of OUT is out of range of REAL variables. he function is blocked till it is new initialised by input RESET." InitialValue="FALSE"/>
</OutputVars>
</InterfaceList>
<SimpleFB>
<Algorithm Name="REQ" Comment="">
<ST><![CDATA[ALGORITHM REQ
IF NOT OVERFLOW THEN
IF (1.0E38 - IN * DINT_TO_REAL(TM) < OUT OR -1.0E38 - IN * DINT_TO_REAL(TM) > OUT) THEN
OVERFLOW := TRUE;
ELSIF (TM > 0) THEN // Time Difference since last call must be positive.
OUT := OUT + IN * DINT_TO_REAL(TM) / 1000.0;
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When testing this in the Interpreter I got the following case:

  • send RESET
  • set IN to 9.0E9, TM to 1 send REQ; OUT goes to 8999999.0
  • set the input to 1.0, send REQ; OUT does not change
  • set the input to -1.0, send REQ; OUT also does not change

this is caused by the variable resolution of the REAL datatype - a warning for the case where the integration does not work (i.e. OUT does not change with IN <> 0) could be nice-to-have

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you are totally right:
our colleges at CODESYS have same issue with same Function.
this comes from the internal representation of REAL.

maybe we should also make a LREAL Version, as well a Fixed-comma Version in DINT.
i will think about it, and in the MEantime make the warning as written above.

END_IF;
END_IF;
END_ALGORITHM]]></ST>
</Algorithm>
<Algorithm Name="RESET" Comment="">
<ST><![CDATA[

ALGORITHM RESET
OUT := 0.0;
OVERFLOW := FALSE;
END_ALGORITHM

]]></ST>
</Algorithm>
</SimpleFB>
</FBType>
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