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 here.

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 Locker, viscous).

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.

LTS TOUR

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