VDS Tour: SPECIAL FEATURES
VDS contains the same core vehicle model as MRA's MMM, LTS and VDMS simulations.
In addition to the standard comprehensive modeling, VDS has unique features of
"Preview-Predictor" Driver Model.
This driver model has several modes of operation, including path-following,
speed maintenance, speed change and skid recovery. Commanded steering wheel
angles and throttle/brake applications are filtered to reflect human dynamic
capabilities, specifically neuro-muscular dynamic characteristics.
Advanced Steering System Model
The Advanced Steering System Model is a detailed model of the steering system
from the steering wheel, through the power steering unit and finally to the
wheels. It replaces lumped-parameter calculations of bump-steer and
bump-inclination with an analysis based on linkage lengths and mounting points.
It is fully asymmetric, and has proven very useful in on-center handling
studies. The model has three main parts:
Modeled as a generic two-Hooke-joint column
Calculation of torque and rotational motion as passed from top (steering wheel)
to bottom (power steering unit) of the column, and vice versa
Includes phasing effects of the Hooke joints
Power Steering Unit
Hydraulic model of standard power steering unit
Includes flow rates, pressures, compliances, leakage across piston
Special friction/stiction model--required to properly model the rack
"Rack Loads" Model
Calculates loads on the end of the steering rack transmitted through the
Determines non-fixed steer axis, bump-steer, bump-inclination
Forces and torques considered include tire forces and moments, drive torques,
inertial reaction forces, centrifugal caster and gyroscopic torques
Includes corrections for non-flat ground, bump-caster, driveshaft angularity,
VDS includes a detailed terrain model of the roadway surface. The model includes
elevation, bank and grade as a function of location in space-fixed coordinates.
Calculation of different roadway ground planes under each wheel as occurs when
driving on a crowned, cambered and curved, warped or non-uniformly banked
roadway is properly modeled. Special emphasis is placed on determining the
"ground point" of each tire and the proper angles for use in tire force and
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