What's New

Full-Vehicle Steering, Speed, and Gear-Shifting Controllers

The Machine Control option in ADAMS/Car's Driving Machine incorporates new discrete control algorithms to control vehicle path, speed, and gear shifting. The algorithms respond faster and track commanded path and speed with less error than in previous releases. The speed-control algorithm incorporates a feed-forward feature that greatly improves response time and reduces error. The gear-shifting algorithm matches engine rpm to the transmission input shaft rpm to reduce clutch torque transients.

The discrete control algorithms samples vehicle states and then updates the steering, throttle, brake, gear, and clutch inputs at each output time step. Between output time steps, the steering, throttle, brake, gear, and clutch inputs are constant. Therefore, control stability is coupled directly to output step size, and larger output step sizes are destabilizing. We recommend output step sizes no larger than 0.01s for typical vehicle models. Simulations employing only open-loop steering, throttle, brake, gear and clutch inputs, however, may use larger output step sizes. The Machine Control algorithms will be decoupled from output step size in a future release.

The new control algorithms require additional information about the vehicle, in particular the available engine torque and braking torque, and the aerodynamic drag. Therefore, the __MDI_SDI_TESTRIG used for full-vehicle simulations has new input communicators for receiving information from powertrain templates. Additional information about the vehicle is stored in assembly files for use by the test rig. The following Knowledge Base Article contains additional information:

1-KB12616: Template Updates for the Driving Machine Compatibility

Finally, path point spacing and vehicle speed may influence the controller's ability to steer a vehicle along a given path. For path point spacing of about 1 m and vehicle speeds 80 to 160 km/h, the controller works well, but for slower or higher vehicle speeds, you may need to adjust the path point spacing or turn on the new path interpolation feature. See the Knowledge Base Article:

1-KB12617: Recommendations on Creating a Path for the Driving Machine

Full-Vehicle Event Builder

ADAMS/Car 2005 adds a new graphical user interface named the Event Builder to create or modify full-vehicle event files (formally driver control or .dcf files). You launch the Event Builder from the Simulate menu. Using the Event Builder you create single or multiple mini-maneuver events. Then for each mini-maneuver in an event, you specify the output step-size, abort time, and desired end conditions (for example, speed < 5m/s), and also the control type (Machine or Open) for the steering, throttle, brake, gear, and clutch inputs. You save your work to an XML event file stored on disk in any location or in your private ADAMS/Car database. To run a simulation using your event file, use DCF driven simulation, from the Simulate menu, just as you would for a .dcf file, except reference your XML event file.

For more information on the Event Editor and a getting started guide, see Knowledge Base Article:

1-KB12621: Event Editor Tutorial

Full-Vehicle XML Event Files

XML format event files replace TeimOrbit Driver Control Files (.dcf) in ADAMS/Car 2005. You can, however, continue to use existing .dcf files to script full-vehicle simulations in ADAMS/Car 2005. Note that you cannot modify .dcf files in the Event Builder without first converting them to .xml event files. You convert .dcf files to .xml event files using the following menu sequence: Tools -> Database Management -> Version Upgrade -> TeimOrbit->XML.

Full-Vehicle Simulation Debugging

To help debugging full-vehicle simulations, ADAMS/Car 2005 SP2 adds new logging capabilities. You access these capabilities by setting the value of the environment variable VEHICLE_SOLVER_DEBUG in your private .acar.cfg file. The settings for VEHICLE_SOLVER_DEBUG, as shown below, may be case-insensitive strings or integers.

Subsystem Add/Remove/Activate/Deactivate Features

With this release, an assembly becomes a live entity, in that you can modify the underlying subsystems even after the assembly is opened.

You can now execute five basic tasks on an open assembly in ADAMS/Car:

1. Add a new subsystem into an existing assembly:

File -> Manage Assemblies -> Add Subsystem

The assembly is first disassembled, which includes 'unassigning' communicators. The new subsystem is then opened underneath the existing assembly. The assembly is finally re-assembled, which includes re-assigning the communicators.

2. Replace an existing subsystem in an assembly with a new subsystem:

File -> Manage Assemblies -> Replace Subsystem

The assembly is first disassembled, which includes 'unassigning' communicators. The existing subsystem is then deleted from the assembly. Next, the new subsystem is opened underneath the existing assembly. The assembly is finally re-assembled, which includes re-assigning the communicators.

3. Remove an existing subsystem from an assembly:

File -> Manage Assemblies -> Remove Subsystem

The assembly is first disassembled, which includes 'unassigning' communicators. The existing subsystem is then deleted from the assembly. The assembly is finally re-assembled, which includes re-assigning the communicators.

4. Deactivate an existing subsystem in an assembly:

File -> Manage Assemblies -> Toggle Subsystem Activity

The assembly is first disassembled, which includes 'unassigning' communicators. The existing subsystem is then deactivated, which means that it is not actually removed from the assembly, but simply ignored. The assembly is finally re-assembled (with the deactivated subsystem not considered), which includes re-assigning the communicators.

5. Activate an existing subsystem in an assembly:

File -> Manage Assemblies -> Toggle Subsystem Activity

The assembly is first disassembled, which includes 'unassigning' communicators. The existing subsystem is then activated, which means that it will now be considered a valid part of the assembly. The assembly is finally re-assembled (with the activated subsystem now taking part), which includes re-assigning the communicators.

Before this release, these tasks would require that you first close the assembly, then re-open a new assembly containing the appropriate subsystem definitions.

Flexible Body Swapping

Added the ability to swap either a rigid part with a flexible part or an existing flexible part with a new flexible part. This utility guides you in selecting the proper node IDs for attachments.

Before this release, you had to create a new template if you wanted to include flexible parts in your assembly. Now, modal flexibility becomes a property of the MSC.ADAMS body. Therefore, introducing flexible bodies becomes a Standard Interface operation and is reflected in the subsystem file.

There are multiple benefits in delegating the creation of flexible bodies to the Standard Interface. These include:

• Avoid multiplication of templates
• Avoid use of unnecessary massless interface parts to ensure connectivity
• Automatic transfer of constraints
• Advanced tools to help detection and transferring of connections from rigid body to flex body nodes

To access this feature, use the Rigid to Flex button in the part modify dialog box. With the installation of ADAMS/Car 2005 SP2 (APN-150-312) a number of problems have been resolved. We encourage you to review the Issues Resolved section below and Known Issues in the Knowledge Base.

Documentation Enhancements

ADAMS/Car Documentation Improvements:

·         Updated the documentation to reflect the new functionality.

Overall Documentation Improvements:

For MSC.ADAMS 2005, we've made improvements to the MSC.ADAMS help:

1.    Added global search so you can search across the entire set of MSC.ADAMS help. To access the global search, do one of the following:

o        At the top of the help, select Switch Products, and then select the Search tab.

o        In any product, select the Search tab, and then in the window that appears, select Global Search.

Note that the global search does not include any .pdfs (including getting started guides and ADAMS/Driver).

2.    Removed any hardcoding of font sizes so you can scale the text of the help to any size. Note that many of the equations do not scale because they are images, and the help looks the best when viewed with medium (or 100%). In addition, your browser will print the text the same size as it is displayed.

3. Documented many of the environment variables for the products to help customize your session. The environment variables are for ADAMS/Controls, ADAMS/Durability, ADAMS/Flex, ADAMS/Solver, ADAMS/View, and the template-based products (ADAMS/Aircraft, ADAMS/Car, ADAMS/Driveline, and ADAMS/Rail). For more information, see the Running and Configuring help.

New Environment Variables

ADAMS/Car 2005 introduced new environment variables and enhanced the functionality of others, which may be helpful in configuring your ADAMS/Car session. The environment variables are listed next:

·         MDI_UPDATE_CFG

This environment variable tells ADAMS/Car whether the private configuration file should be automatically updated during the session to reflect CDB Database changes.  This auto-update of the private configuration file is also referred to as the live configuration file. ADAMS/Car 2005 defaults to the live private configuration file, and the MDI_UPDATE_CFG environment variable allows you to turn off the auto-update feature, essentially returning to the v2003 release behavior. To disable the auto-update of the private configuration file, simply add the following line into your private configuration file:

ENVIRONMENT      MDI_UPDATE_CFG          no

·         MDI_ACAR_XRF

ADAMS/Car 2005 defaults to using the XML results file (also referred to as the .xrf file) instead of the request file. To restore the behavior in ADAMS/Car 2003, with the request file being output by default, you may add this line into your private configuration file:

ENVIRONMENT      MDI_ACAR_XRF            off

·         MSC_SHOW_STATUS

Setting this environment variable causes ADAMS/Car to add the following additional line to the bottom of the .acf file for full-vehicle simulations:

show status=simulation

This can be useful in providing simulation statistics from the solver run.  To get this output into your .acf files for full-vehicle simulations, add the following line into your private configuration file:

ENVIRONMENT      MSC_SHOW_STATUS         yes

• MDI_CDB_EXPAND_PATH
  
  Setting this new environment variable causes ADAMS/Car to write out a full system path reference to CDB files in the adm deck instead of using the “mdids://” alias. For example, a tire property file reference that normally looks like this in the adm file:

mdids://acar_shared/tires.tbl/TR_front_pac89.tir

would become something like this:

D:/MSC.Software/MSC.ADAMS/2005/acar/shared_car_database.cdb/tires.tbl/TR_front_pac89.tir

Note that the property file referenced in your ADAMS/Car session will not change: it will still retain the “mdids://” alias. To have ADAMS/Car write out the full system path reference into the adm deck, add the following line into your private configuration file:

ENVIRONMENT MDI_CDB_EXPAND_PATH yes

·         MDI_ACAR_USE_EDITOR

This environment variable previously existed, but it may become more relevant to some customers who are using .xml property files.  This environment variable governs the behavior of the View Property File button visible on the dialog boxes containing property files. By default, when you click this button, ADAMS/Car puts the contents of the property file into the session Info Window. This was useful with TeimOrbit property files, but viewing the contents of an .xml property file in the info window is much less friendly. If MDI_ACAR_USE_EDITOR is set to yes, then the contents of the xml property file are displayed in your default web browser. Along with the VisEdit .xml property file editor, this allows for easy inspection of the contents. The appropriate line to enter in your private configuration file is:

ENVIRONMENT      MDI_ACAR_USE_EDITOR     yes

·         VEHICLE_SOLVER_DEBUG

To aid debugging full-vehicle simulations, ADAMS/Car 2005 SP2 adds new logging capabilities. You access these capabilities by setting the value of the environment variable VEHICLE_SOLVER_DEBUG in your private .acar.cfg file. The appropriate line to enter in your private configuration file is:

ENVIRONMENT      VEHICLE_SOLVER_DEBUG     on

The table below shows additional settings for VEHICLE_SOLVER_DEBUG, which are case-insensitive strings or integers.

Changes

Property File Changes

The following property files classes and/or property files in the acar_shared database have changed:

Subsystem Changes

mdids://acar_shared/subsystems.tbl/Powertrain_lt.sub:

The Powertrain_lt subsystem now references a new powertrain property file (mdids://acar_shared/powertrains.tbl/V8_240HP_400Nm.pwr) that represents a typical five liter displacement, OHV, V-8 engine used in North America. The torque-speed characteristic produces much greater torque at lower engine speeds, and the maximum engine speed is much lower, compared to the V12_engine_map.pwr property file.

In accordance with the powertrain property file, the number of gears is reduced to five (5) and the gear and final drive ratios are altered to better match the engine characteristics.

Template Changes

The following templates in the acar_shared database changed: