s7-1 adm740, section 7, june 2007 copyright 2007 msc.software corporation section 7 creating and...

S7-1ADM740, Section 7, June 2007Copyright 2007 MSC.Software Corporation

SECTION 7

CREATING AND SIMULATING FULL VEHICLES


● In this section, you learn how to create full-vehicle assemblies in Adams/Car. You also learn about the available full-vehicle analyses and how to submit them.

Creating and Simulating Full Vehicles


Creating and Simulating Full Vehicles

● What’s in this section:

● Creating Full-Vehicle Assemblies

● Shifting Subsystems

● Updating Subsystems and Assemblies

● Synchronizing Subsystems and Assemblies

● Adding/Removing and Activating/Deactivating Subsystems

● Adjusting Mass

● Full-Vehicle Analyses

● Full-Vehicle Event Generator


● To create a full-vehicle assembly, go to File New Full Vehicle. This dialog box requires a list of all subsystems that make up your assembly. The subsystem necessary are body, front and rear suspension, front and rear tires, steering system, and a test rig.

● All the analyses currently available are based on the Driving Machine. Therefore, to perform open-loop, closed-loop, and quasi-static analyses, you must select the .__MDI_SDI_TESTRIG in your assemblies.

● You can include other subsystems in the full-vehicle assembly by selecting the check box, Other Subsystem. The location and connectivity of these subsystems depend on the how the subsystems and the communicators are defined, and whether or not the template is shifted.

Creating Full-Vehicle Assemblies


Full Vehicle Assembly Illustrated

Full Vehicle Assembly

Rear Wheels

TestrigFront

Suspension

Body Steering

Rear Suspension

Front Wheels


● To shift a subsystem, in the Standard Interface, go to Adjust Shift. Here you have the choice of shifting the subsystem fore/aft and up/down. Fore/aft moves the subsystem along the global x-axis. Up/down moves it along the global z-axis.

Shifting Subsystems


After shifting the rear suspension aft and up

Shifting Subsystems (Cont.)


Updating Subsystems and Assemblies

● Updating subsystems● Occasionally, you may want to change a subsystem that is used within

your assembly, and see the changes take effect in your assembly. In other words, you want to edit the subsystem file, and see the changes alter your assembly file. To do this, go to File Update Subsystem, and then select the subsystem. This option prevents you from closing the assembly and reopening it with the modified subsystem to see the change.

Note: You must save the changed subsystem in the database to be loaded into the assembly. Also, the update subsystem changes do not affect topology; they only update the parameters that can be adjusted at the subsystem level.

● Updating assemblies● Similarly to updating subsystems, you can update your assembly. To do

this, go to File Update Assembly, and then select the assembly. This option prevents you from closing the assembly and reopening it with the modified subsystems by reloading information from the saved subsystems that the assembly references.


Synchronizing Subsystems and Assemblies

● Adams/Car allows you to automatically synchronize multiple in-session versions of the same subsystem. You can select a master subsystem (source) and choose from a dynamically updated list of other subsystems (targets) in the session. The target subsystems then inherit all settings of the master (only the subsystem mode is retained), which helps alleviate some subsystem consistency concerns raised when we introduced support for multiple assemblies in the same session.

● For example, assume you are working on a suspension assembly and a full-vehicle assembly that both reference the same steering subsystem. If you make a change to the steering wheel position in the suspension assembly, this functionality allows you to synchronize that change into the full-vehicle assembly, rather than making the change in two places.


Adding/Removing and Activating/Deactivating Subsystems

● An assembly is a live entity, in that you can modify the underlying subsystems even after the assembly is opened. You can perform five basic tasks on an assembly open in an Adams/Car session, as explained next.

● 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 reassembled, which includes re-assigning the communicators.


Adding/Removing and Activating/Deactivating Subsystems (Cont.)

● 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.

● 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.



● 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.

● 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.



● 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.

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


Adjusting Mass

● Adjusting the mass of your vehicle automatically● In Adams/Car you can adjust the mass properties of an

assembled model. To adjust the aggregate mass, enter the desired mass, the desired centroidal inertias, and the desired center-of- mass location, relative to a marker. You also select a part that Adams/Car modifies to match the desired mass properties. Therefore, the mass properties of the virtual vehicle match those of the real vehicle.

● To adjust the mass properties, go to Simulation Full Vehicle Analysis Automatic Mass Adjustment.

● To get the mass of some or all of the parts in your model, select Tools Aggregate Mass (use the dialog box help (F1) for help on Aggregate Mass).

● If desired change causes the part you select to have a negative Ixx, Iyy, or Izz then the system the system will be unstable. To avoid this, you should first reduce inertia values in other parts so that all parts satisfy the Ixx + Iyy > Izz criteria without having negative inertias.


Adjusting Mass (Cont.)

● Adjusting the mass of your vehicle based on a typical measurement

● In most cases, the vehicle’s center of gravity (CG) location data (inertia tensor) is given with respect to the vehicle’s CG. However, when you use Tools Aggregate Mass with respect to the ground (default) reference frame, the inertia tensor will be reported with respect to the global coordinate system at (0,0,0), since you don't know where the vehicle CG is beforehand. So, you have to first find out the vehicle CG location and create a CG marker in the template at that location. Then using Tools Aggregate Mass again, this time with respect to the CG, find out the inertia tensor. This will allow you to compare your MD R2 Adams model mass properties to your measured data.


Adjusting Mass (Cont.)

● In your Adams/Car body template, you may create a hardpoint named vehicle_cg and create a marker, also named vehicle_cg, in the body parameterized to the same location as this hardpoint. In Adams/Car Standard Interface, first modify the CG hardpoint to the given value, then select Simulate Full-Vehicle Analysis Automatic mass adjustment. To display online help for this dialog box, press F1. Here is the suggested dialog box input:

● CG location = 0,0,0● Relative to marker = vehicle_cg● Modify Part = body (chassis)

Adams/Car can adjust the total vehicle mass and inertia by changing the mass, inertia, and CG location of the Modify Part.

Tip: Don't set Relative to Marker to ges_chassis.cm if you select ges_chassis as the Modify Part, because Adams/Car will change the center-of-mass position of ges_chassis.


Full-Vehicle Analyses

● As stated previously, all the analyses currently available are based on the Driving Machine. Therefore, to perform open-loop, closed-loop, and quasi-static analyses, you must select the .__MDI_SDI_TESTRIG in your assemblies.

● The following is a list of the types of events that are available in Adams/Car:● Open-loop events

● Drift● Impulse steer● Ramp steer● Single lane change● Step steer● Swept sine steer


Full-Vehicle Analyses (Cont.)

● Cornering events● Braking-in-turn● Constant-radius cornering● Cornering with steering release● Lift-off turn-in● Power-off cornering

● Straight-line behavior● Acceleration● Braking● Power-off straight-line

● Course events● ISO lane change

● File Driven Events


Full-Vehicle Analyses (Cont.)

● Static and Quasi-static maneuvers● Constant-radius cornering● Constant-velocity cornering● Force moment method● Straight-line acceleration● Static Analysis

● SmartDriver● 3D smooth road

For details on these analyses, see the Running Analysis section in the Adams/Car online help.

● You can perform other full-vehicle analyses by creating your own test rig (see Appendix B, Four-Post Vertical Excitation Test) or by using Adams/Car Ride or Adams/Driveline (see Section 17 - Additional Applications).


Full-Vehicle Event Generator

● You use the Event Generator to create and modify full-vehicle event files that can contain multiple mini-maneuvers that you define. Within each minimaneuver, you can specify the steering, throttle, braking, gear, and clutch settings. You can also select from a large list of end conditions that terminates each mini-maneuver. These event files can then be used with the new driver technology developed by MSC.Software to simulate various full-vehicle events.


Full-Vehicle Event Generator (Cont.)

● The Driving Machine control files use the XML data format and can be viewed in the Event Builder interface or in any Web browser.

● To access the Event Generator, go to Simulate Full-Vehicle Analysis Event Generator. Use the Event Generator to define a generic full-vehicle event from scratch or modify an existing full-vehicle event file. In particular you can:

● Define vehicle-specific information that is used by the Driving Machine during the execution of an event.

● Define controller parameters and gear-shifting strategies.● Define quasi-static setup information that will be used during the quasi-

static prephase of the simulation to drive the vehicle to a desired state of longitudinal and lateral acceleration.

● Define the number and the type of mini-maneuvers. For each mini-maneuver you can specify:

● The behavior of all five application areas (throttle, brake, gear, clutch, and steer).

● A number of individual or grouped end-conditions.● The machine control strategy for the longitudinal and lateral dynamics of

your vehicle.

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