modelExpression

User defined real function

Extends from IndustrialControlSystems.MathOperations.RealType.Interfaces.RealNinOperation (Real comparison interface).

Information

Description

Model of a generic function of n real numbers.
The output ( y ) is the result of the generic function f(.) of the inputs ( u(:) ) signals.

    y = f(u[:])

Fixed Point numbers

When using fixed point real numbers, Nbit is the number of bits that can be represented. The range is

  Xfp in [-2^{Nbit - 1} + 1  ,...,  2^{Nbit - 1}]

Then it is possible to define a scaleFactor

  X = Xfp/scaleFactor

When the Fixed Point representation is selected (through the selection of the boolean flag FixedPoint), each input number u is converted into an integer Ufp

  Ufp = u*scaleFactor

then the result of the math operation Yfp is computed and converted into the output value y. The output conversion depends on the math operation performed.

Saturation

To note that the Fixed Point numbers have a maximum and minimum value. In order to avoid saturation when performing the computations, the number of bit as well the scale factor have to be choosen carefully.

Parameters

Type	Name	Default	Description
Modelica.Units.SI.Time	Ts (from RealNinOperation)	0.1	sampling time
Integer	nInput (from RealNinOperation)	1	number of inputs
Boolean	useInputs (from RealNinOperation)	true	=true, if inputs are enabled
String	fname	"F name"	String that represent the name of the implemented function
Fixed Point
Boolean	FixedPoint (from RealNinOperation)	false	Use fixed point real numbers
Integer	Nbit (from RealNinOperation)	16	Number of bits for representing the real numbers
Real	scaleFactor (from RealNinOperation)	1	Scale factor for Fixed Point numbers
Integer	MAX (from RealNinOperation)	integer(2^(Nbit - 1))	maximum number that can be represented with Fixed Point notation
Integer	MIN (from RealNinOperation)	-integer(2^(Nbit - 1)) + 1	minimum number that can be represented with Fixed Point notation

Connectors

Type	Name	Default	Description
Modelica.Blocks.Interfaces.RealInput[nInput]	u (from RealNinOperation)		input vector
Modelica.Blocks.Interfaces.RealOutput	y (from RealNinOperation)		output

Components

Type	Name	Default	Description
Integer[nInput]	Ufp (from RealNinOperation)		floating point converted input
Integer	Yfp (from RealNinOperation)		floating point converted output

Name	Description
f	generic real function
g	Output re-scaling function

Revisions

Industrial Control Systems (v 1.0.0) : April-May 2012