Model Element

Class Name

Request

Description

Request defines an output request entity in MotionSolve. Request are written to MotionSolve output files so that they may be used for plotting and signal processing by HyperGraph. Request is available in four types:

Attribute Summary

Usage

#1. As built-in marker-based functions

Request (type=string, i=objMarker, optional_attributes)

#2: As a set of expressions based on the MotionSolve run-time expression language

Request (optional_attributes)

#3. As a user-subroutine written in a compiled language Fortran, C or C++

Request (function=userString, routine=string, optional_attributes)

#4. As a user-subroutine written in Python

Request (function=userString, routine=functionPointer, optional_attributes)

Attribute Description

As built-in marker-based functions

type

String

Specifies the type of REQUEST element.  Select from “DISPLACEMENT”, “VELOCITY”, “ACCELERATION”, or “FORCE”.

The type attribute is mandatory.

i

Reference to an existing Marker object

Specifies the Reference_Marker ID at which the information is being calculated.

The i attribute is mandatory.

j

Reference to an existing Marker object

Specifies the Reference_Marker ID at which the information is being calculated. from which the information is being calculated.  The information is typically some vector or orientation relating to j, such as displacement, velocity, acceleration and I or force.

The j attribute is optional.

When not specified, j defaults to the global coordinate system. You can also set j=0, indicating it is the global coordinate system.

rm

Reference to an existing Marker object

Specifies the Marker in whose coordinate system the vector components are computed. rm can be on any body, including Ground

The rm attribute is optional.

When not specified, rm defaults to the global coordinate system. You can also set rm=0, indicating it is the global coordinate system.

As a set of expressions

f1, f2, f3,

f4, f5, f6,

f7, f8

String defining a valid MotionSolve expression

Each of these attributes contains an expression that specifies a scalar quantity that is to be computed at run-time as output.

All of these attributes are optional. When not specified they default to 0.

As a user-subroutine written in a compiled language Fortran, C or C++

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 Request is defined.

The function attribute is mandatory.

routine

String

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

An example is: routine=”/staff/Altair/engine.dll∷myRequest”

The attribute routine is optional.

When not specified, routine defaults to REQSUB.

As a user-subroutine written in Python

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 Request is defined.

The function attribute is mandatory.

routine

Pointer to a callable function in Python

An example is: routine=myRequest

The attribute routine is optional.

When not specified, routine defaults to REQSUB.

Optional attributes – Available to all variants

id

Integer

Specifies the element identification number.  This number must be unique among all the Gforce objects in the model.

This attribute is optional. MotionSolve will automatically create an ID when one is not specified.

Range of values: id > 0

label

String

Specifies the name of the Gforce object.

This attribute is optional. When not specified, MotionSolve will create a label for you.

comment

String

A character string that gives a general description of signals being measured in this Request. The string can be of any length.

This attribute is optional.

cnames

List of strings

Specifies eight component names for each of the eight signals.

This attribute is optional.

cunits

List of strings

Specifies the Units of each signal.

This attribute is optional.

active

Bool

Select one from True or False.

The attribute active is optional. When not specified, active defaults to True

Comments

Example

req1 = Request(type="DISPLACEMENT", i=satellite.cm, comment="Satellite trajectory time history")

Hx = “{M}*WX ({i},0,{i})”.format(M=satellite.mass, i=satellite.cm)

Hy = “{M}*WY ({i},0,{i})”.format(M=satellite.mass, i=satellite.cm)

Hz = “{M}*WZ ({i},0,{i})”.format(M=satellite.mass, i=satellite.cm )

req2 = Request (f2=Hx, f3=Hy, f4=Hz, comment="Satellite angular momentum")

req3 = Request (type="Force", i=m1102, j=m1972, rm=m1972, comment="Tether force time history")