# Request

Model ElementRequest defines an output request entity in MotionSolve.

Request

## Description

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:
• As built-in marker-based functions
• As a set of expressions based on the MotionSolve run-time expression language
• As a user-subroutine written in a compiled language Fortran, C or C++
• As a user-subroutine written in Python

## Attribute Summary

Name Property Modifiable by command? Designable?
id Int ()   No
label Str () Yes
type Enum ("DISPLACEMENT VELOCITY ACCELERATION FORCE")
i Reference (Marker) Yes
j Reference (Marker) Yes
rm Reference (Marker) Yes
f1 Function () Yes
f2 Function () Yes
f3 Function () Yes
f4 Function () Yes
f5 Function () Yes
f6 Function () Yes
f7 Function () Yes
f8 Function () Yes
function Function ("REQSUB")
routine Routine ()
comment String ()
results_name String ()
cnames String ()
cunits String ()
clabels String ()
variables Reference ("Variable", count=0)
active Bool () Yes

## 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)

## Attributes

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"
• "/staff/Altair/ engine.dll is the DLL
• "myRequest" is the function within this DLL that performs the calculations
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.
• myRequest 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 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 automatically creates 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.
• True indicates that the element is active in the model and it affects the behavior of the system
• False indicates that the element is inactive in the model and it does not affect the behavior of the system. It is almost as if the entity was removed from the model, of course with the exception that can be turned "ON" when desirable.

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

## Example

1. XML example: Marker displacement REQUEST.
req1 = Request(type="DISPLACEMENT", i=satellite.cm, comment="Satellite trajectory time history")
2. XML example: Angular Momentum REQUEST.
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")
3. XML Example: Force REQUEST.
req3 = Request (type="Force", i=m1102, j=m1972, rm=m1972, comment="Tether force time history")