MinVal

Class Name

MinVal

Description

The minimum is approximated by an alpha-soft function so that the analytical sensitivity can be calculated.(1)

\min (x) = \frac{\int_{0}^{T} x (t) e^{α x (t)} d t}{\int_{0}^{T} e^{α x (t)} d t}

Where $α$ is a negative constant and satisfies $α = - c o e f$ . The default of $c o e f$ is 10 and should work for the majority of use cases.

Attribute Summary

Name	Property	Designable
label	Str ()
function	Function ()	Yes
routine	Routine ()
plot	Bool ()
wlen	Int ()
k	Int ()

Usage

#1: MinVal specified as an expression
MinVal (function=expressionString)

#2: Defined in a compiled user-subroutine
MinVal (function=userString, routine=string, optional_attributes)

#3: Defined in a Python function
MinVal (function=userString, routine=functionPointer, optional_attributes)

Attributes

Defined as the maximum value of an expression.

function: String; A MotionSolve expression defining the function for which MinVal is required.; The function attribute is mandatory.

Defined as a user-subroutine in a compiled DLL.

function

String defining a valid user function MotionSolve expression.

The list of parameters that are passed from the data file to the user defined subroutine where the MinVal is defined.

The function attribute is mandatory.

routine

Specifies an alternative name for the user subroutine. The name consists of two pieces of information, separated by "∷". The first is the path name to the shared library containing the function that computes the response of the user-defined Variable. The second is the name of the function in the shared library that does the computation.

An example is: routine="/staff/Altair/engine.dll∷myMinVal"

"/staff/Altair/ engine.dll is the DLL
"myMinVal" is the function within this DLL that performs the calculations.

The attribute routine is optional.

When not specified, routine defaults to VARSUB.

Defined as a user-subroutine in a Python script

function

String defining a valid user function MotionSolve expression

The list of parameters that are passed from the data file to the user defined subroutine where the Variable is defined.

The function attribute is mandatory.

routine

Pointer to a callable function in Python.

An example is: routine = myMinVal

myMinVal is a Python function or method that can be called from wherever the model resides.

The attribute routine is optional.

When not specified, routine defaults to VARSUB.

Optional attribute

label: String; Specifies the name of the MinVal object.; This attribute is optional. When not specified, MotionSolve creates a label for you.
coef: Double; Specifies the coefficient in the soft-alpha function. The default value is 1.0 and should work for the majority of use cases.
wlen: Integer; The window length for the smoothing function. You can increase its value to smooth the minimum value when the response contains high frequency noise.
k: Integer; The order of the smoothing function. The default value is 1. You can increase its value if you lose the true minimum due to smoothing.

Example

# Compute the minimum of the absolute value of the z-acceleration of a Marker
zacc = "ABS(ACCZ({},{}))".format(self.block.cm.id,self.ref.id)
zmax = MinVal (function=zacc)

Comments

See Properties for an explanation about what properties are, why they are used, and how you can extend these.
You can verify the response value by comparing it with the curve in HyperGraph. For a high frequency signal, the value returned by MotionSolve may not agree with HyperGraph. This is because the minimum in MotionSolve is computed at each integration step, while HyperGraph computes only at the output step. The output step is usually larger than the integration step, hence the difference. You can eliminate the difference by reducing the output step in MotionSolve.