s4_creating and simulating suspensions

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ADM740, Section 4, May 2012

Copyright 2012 MSC.Software Corporation

SECTION 4

CREATING AND SIMULATINGSUSPENSIONS



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● In this section, you learn how to create a suspension

assembly in Adams/Car. You learn about the available

suspension analyses and how to submit them. You also learn

about the plot configuration files, how to create them, and

how to review the results of your analyses.

Creating and Simulating Suspensions



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● What’s in this section:

● Creating Suspension Assemblies

● Half-Vehicle Analyses

● Suspension Parameters

● Creating Loadcases

● Dynamic Analysis

● Warning Messages

● Files Produced by Analyses

● Plot Configuration Files

Creating and Simulating Suspensions



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● An assembly consists of a single test rig and one or moresubsystems (a test rig by itself is just a specialized subsystem).

● You create suspension assemblies in Standard Interface: from the

File menu, point to New, and then select Suspension Assembly. In

the dialog box, specify all the subsystems to be included in the

assembly, as well as the test rig.● If you use subsystems created from new templates, you need to

make sure the communicators match up. Communicators are

special variables defined at the template level to bring the

subsystems together, and with the test rig, to create an assembly.

In the template-builder mode, you can test the communicators tomake sure they match with other templates (communicators are

described in more detail in Section 12 – Communicators).

Adams/Car displays warning messages in the Message window for

communicators that are not matched when creating an assembly.

Creating Suspension Assemblies



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Creating Suspension Assemblies

● The picture below shows a suspension assembly containinga suspension and steering subsystem, and test rig.

● Because simulations are activated by test rigs, to perform a

simulation, you must use an assembly.



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Suspension Assembly Illustrated

Suspension Assembly

Test Rig

Front

SuspensionSteering



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Half-Vehicle Analyses

● You can perform the following types of suspension analyses

in Adams/Car:

● Parallel wheel travel - Both wheels move in unison.

● Opposite wheel travel - Wheels move out of phase.

● Roll and vertical force - Sweeps roll angle while allowing wheels tofind their own vertical position, the total force on both wheels is held

constant.

● Single wheel travel - One wheel fixed, while other moves.

● Steering - Motion applied to steering wheel or rack.



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For more information, see the Running Analyses

section in the Adams/Car online help.

Half-Vehicle Analyses● Static load - Force or displacement applied at specified locations

(wheel center, tire contact patch), with or without steering.

● External files:

● Loadcase – specify a file that describes a custom loading scenario.

Loadcase files can be created using the Generate Loadcase dialog box

● Wheel envelope – a series of parallel wheel actuations in which the steer

angle is being swept over a specified range. Generates a table of points

that define the wheels position for wheel interference/collision analysis

● When performing a suspension analysis, Adams/Car uses the first

second to bring the wheel centers to the lowest position, and then uses

as many seconds as you specify steps, to move the suspension to the

upper position.

● Dynamic Analysis - Apply test data to drive the test rig actuators andcarry out dynamic analysis



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Suspension Parameters

● Some of the default request outputs need information that is

not available in the model. Therefore, you must supply this

additional information. This information has no bearing on the

outcome of the simulation, and only affects the values of

some “user -defined” (pre-defined) results (for example, the

roll center).● Adams/Car stores the input in an array named Suspension

Parameters, which you can find in the Standard Interface

under Simulate Suspension Analysis Suspension

Parameters.● The values you must supply are:

● Loaded tire radius






● Tire stiffness (user-entered or from property file)● Sprung mass

● CG height

● Wheelbase

● Drive ratio

● Brake ratio

● Adams/Car uses the parameters cg_height, wheelbase,

sprung_mass, and tire stiffness when calculating:

● Percent anti-dive

● Dive

● Percent anti-lift

● Lift

● Percent anti-squat

● Roll center height






● Adams/Car uses the tire stiffness when calculating:

● Suspension rates

● Total roll rate




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2012 MSC.Software Corporation

Creating Loadcases

● A loadcase is an ASCII file containing all necessaryinformation to run a simulation. It is basically a way of scripting suspension simulations with these fiveforce/actuation types:● Wheel travel (Parallel, Opposite, Single)

● Steering

● Static load● Roll and vertical force

● When running a loadcase, Adams/Car searches for theparticular loadcase file stored in the database. You can callmany loadcases, and Adams/Car will run them one at a time.

● You can create a loadcase file by selecting Simulate Suspension Analysis Create Loadcase. Then, select thetype of analysis you want to run, and specify the relevantdata.




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Dynamic Analysis

● Adams/Car now provides the ability to do a dynamic analysis

in addition to the other analysis.

● The Suspension assembly can be excited by providing input

as displacement, velocity, acceleration or Force to the Jacks

(defined in the testrig).

● Use a RPC File to drive the testrig using test data or use

runtime View functions.

● Issues a Sim/Dynamics command to the test rig.

● Compliance Matrix is not calculated.




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Warning Messages

● When you create an assembly, you will sometimes see

warning messages. For example, suppose you are creating afront MacPherson suspension assembly without a steering or body subsystem. Because steering and body parts are notspecified in the test rig or another subsystem, certaincommunicators are attached to ground or not attached to

anything. The Message window displays the following:




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Warning Messages

● The models in the shared car database contain all the

communicators that could possibly be used by other systems,and in many cases, not all communicators are used.However, be sure to check out which ones aren't beingconnected to see if it makes sense. Here, most of them couldpotentially be connected to the body, or to some other subsystem you currently don't care about in your analysis. Bydefault, if Adams/Car cannot find the matching communicator,it attaches it to ground, which, in this case, is fine. So, youshouldn’t typically be concerned about it, unless you see acommunicator that should be used but isn't.




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Files Produced by Analyses

● It’s important to remember that all vertical products, including Adams/Car, are simply preprocessors for Adams/Solver. This means

that they simply produce the .adm file (Adams/Solver data, the model)

and the .acf file (Adams/Solver commands). These files are created in

the working directory (File Select Directory).

● The output files produced include message (.msg), request (.req),

results (.res), graphics (.gra), and output (.out) files. Adams/Car mayalso produce a .xml file as described in Driving Machine, in Section 7.

Adams/PostProcessor requires the results file to plot the deformation

color contours, and so on, of the flexible body, if one exists.

● When you import the analysis requests file (.req) in

Adams/PostProcessor, Adams/Car also produces a special file,

named the name file (.nam), which contains the name associated withevery request in the interface.

● You can use the .adm, .acf, and .xml files to submit an analysis

outside of the Adams/Car graphical interface.




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Plot Configuration Files

● In this section, we’ll cover following topics:

● What is Plot Configuration File?

● Creating Plot Configuration Files

● Creating Plots Using a Plot Configuration File

● Format of Plot Configuration Files

● Example Plot Configuration File




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● What is Plot Configuration File?:

● Plot configuration files tell your template-based product:

● Which plots to create

● The vertical and horizontal components that it should plot

● General settings and preferences, such as titles, labels, horizontal and

vertical spacings, scaling, legend text, and more

● The files currently support only one plot per page, which can

contain multiple axes. You can cross-plot multiple analyses of the

same type using one plot configuration file.

● Plot configuration files are TeimOrbit files and are stored in your

database in the plot_configs.tbl directory.● You can access the plot configuration file functionality in

Adams/PostProcessor.




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● Creating Plot Configuration Files:

● You can create a plot configuration file containing all of the plots

currently in Adams/PostProcessor or only a selected set of plots. Your

template-based product stores the configuration files in the plot_config

table of your default writable database.

● Note that you can create only one plot per page.




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● To create a plot configuration file:

1. Create and configure plots as desired, including specifying labels and

spacing. For example, you can create a set of plots and add subtitles

to all of them that describe the type of analysis with which the plots are

associated.

2. From the File menu, point to Export, and then select PlotConfiguration File.

The Save Plot Configuration File dialog box appears.

3. In the Configuration File Name text box, enter the name for the plot

configuration.

4. Select the plots and curves that you want to include.

5. Select OK.





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Plot Configuration File

● Creating Plots Using a Plot Configuration File:

● After you've run an analysis, you can view the series of plots definedin a plot configuration file. If your plot configuration file containscustomization command keywords and it has created the plots andcurves, you can have your template-based product invoke the macrothat contains a command keyword in its user-entered command.

● The plot configuration file specifies a subtitle for your plots. Inaddition, in the File Import

● you can:● Add a title to all the plots.

● Plot results of multiple analyses on one plot using the Cross Plotting

option.● Change the look of your plot, such as fonts and size, using the option

Execute Custom Macros. To use this option, you must have a macrothat defines the commands to be executed.




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● To view the plots defined in a plot configuration file:

1. From the Plot menu, select Create Plots.

The File Import dialog box appears.

2. In the Analyses text box, enter the analysis or analyses from which

you want to view results.

3. In the Plot Configuration File text box, enter the name of the plot

configuration file defining the plots that you want to view.

4. Select OK.

● For details, see the Plot tab in the Adams/Car onlinehelp.





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Plot Configuration Files● Format of Plot Configuration Files:

● Plot Data Block● The plot data block has the following structure:

● NAME

● SUBTITLE

● TIME_LOWER_LIMIT

● TIME_UPPER_LIMIT

● PLOT_AXES (subblock)● COMMAND

● command_keyword

● After your template-based product creates each plot, it executes the following

commands if you defined a command keyword:

acar custom_plots <command_keyword> & plot_name=<plot_name>

● The command acar custom_plots <command_keyword> must already becreated in the current session, either interactively or already present in the

acar.bin, aengine.bin, or arail.bin file.

● For more information, see KBA 8848 at:

http://support.Adams.com/kb/faq.asp?ID=kb8848.html.





Format of Plot Configuration Files

● Plot-Curve Data Block

● The plot-curve data block has the following structure:● NAME

● PLOT

● VERTICAL_AXIS

● HORIZONTAL_AXIS

● VERTICAL_COMPONENT

● HORIZONTAL_COMPONENT

● LEGEND_TEXT

● COLOR● red, blue, yellow, magenta, cyan, black, white, skyblue, midnight_blue, blue_gray,

dark_gray, silver, peach, maize

● STYLE● solid, dash, dotdash, dot

● SYMBOL● none, x, o, plus, star, at

● LINE_WEIGHT● Real value from 1-4

● COMMAND● command_keyword






● After your template-based product creates each curve, it executes the

following commands if you defined a command keyword:

● The command acar custom_plots <command_keyword> must alreadybe created in the current session, either interactively or already

present in the acar.bin, aengine.bin, or arail.bin file.

● For more information, see KBA 8848 at:

http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1-KB8848

● We provide several example plot configuration files in the Adams/Car shared database. For details of the output they plot, see KBA 10652

at: http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1-KB10652






● Example Plot Configuration File:● The following is an example of an

Adams/Car plot configuration file:

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