LTS Tour: INPUT
Input to LTS is through a series of five ASCII files describing the vehicle,
engine, aerodynamics, tires and track. These input files are, with small
differences, also compatible with MMM and VDS. They also contain the same data
as the VDMS input files. The LTS User's Manual contains a detailed description
of the inputs and input file formats. For a sample of the User's Manual, click
The Vehicle File is a fixed-format ASCII file. Click
here to view a page from a sample vehicle file. The model
contains a choice of solid or independent rear axle, each of which is modeled
separately. Suspension kinematics and compliances are input in polynomial or
tabular form. Several choices are available for modeling normal force coupling.
LTS represents the vehicle as a lumped-parameter system with 15 degrees of
freedom: six chassis, four vertical unsprung, four rotational and 1 steer.
Left/right asymmetric vehicle parameters (as for an oval track race car) may be
input, or a symmetric vehicle may be specified. A vehicle data set may contain
hundreds of inputs, although LTS executes properly with simplified data sets.
Vehicle File inputs can be edited via a new graphical interface. Two sample
pages are shown above.
The Engine File is a free format ASCII file describing the engine, transmission
and driveline. Inputs include a table of engine power versus engine speed, gear
ratios, off-throttle shift time, gear efficiencies, minimum time in a gear and
differential type (open, clutch pack limited-slip, Weismann, spool, Detroit
The Aerodynamics File is a free format ASCII file with three choices of models.
The simplest model contains constant aerodynamic coefficients for front lift
(downforce), rear lift and drag. The intermediate model includes varying
coefficients as a function of front and rear ride height changes. The third
model is a highly detailed, six-component aero model based on vehicle ride
height, pitch, roll, and yaw.
The tire model can access data in several formats including generic tabular
force and moment data, MRA's Nondimensional Tire Model, Pacejka 96 and the
Goodyear Advanced Race Tire Model. Use of the Goodyear model requires access to
tire data in the appropriate format available only through a separate agreement
between the user and The Goodyear Tire and Rubber Company. For a description of
MRA's Nondimensional Tire Model, click here
(Note: Following this link will leave the LTS Tour).
The Track File is a free format ASCII file containing information about the
track along the "racing line". Path radius, grade, bank, vertical curvature and
local friction coefficient are inputs at up to 2000 locations around the
circuit. A "force a gear" option is provided to override the LTS shift logic,
if desired, to keep a driver in a particular gear at a specific location around
the track. To assist in developing quality track files, LTS includes the
Track.exe Utility Program which allows editing, smoothing and visualization of
the track data.
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