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Overview

The 18 Degree Of Freedom (DOF) vehicle model is a double-track vehicle model with simplified roll and no pitch. This is the intermediate level of fidelity and is thus faster than the 24 DOF model but slower than the 11 DOF model. The 18 DOF model does not capture pitch and heave motions, and the front and rear suspension are represented simply by their respective roll stiffness and roll damping coefficients. Additionally, wheel lift off conditions cannot be simulated. The vertical forces $F_{z_{ij}}$ are obtained based on quasi-static lateral and longitudinal load transfers. This model assumes the same engine, torque converter, powertrain and TMeasy tires as the 11 DOF and 24 DOF models. The 18 DOF model takes the same input as the 11 DOF and 24 DOF models - Throttle $\in [0,1]$, Braking $\in [0,1]$ and Steering $\in [-1,1]$ where $-1$ is a full left turn. See chapter 2 here for more details.

Where do I set model parameters?

Model parameters are set through JSON files which are then used in the construct solver function. Examples of these JSON files are available for 2 different vehicles in data/json/HMMWV and data/json/Sedan. Examples of use are available in demos.

How do I provide driver-inputs?

Driver Inputs can be provided at run-time during the simualtion or before the beginning of the simulation. For examples on provided driver inputs at run-time, see demos/HMMWV/demo_hmmwv_hi_step.cpp.
These inputs can also be provided before the simulation begins through text files. See data/input/acc.txt for an example. Here, the first column is the time, second column is steering, third column is throttle and the last column is braking. The solver then computes the steering, throttle and braking inputs at a given time through linear-interpolation. See demos/HMMWV/demo_hmmwv_hi for more details.

How do I run the demos?

See here for a general description of how to run the demos. For the 11 DOF model, the demos are placed in the demos folder. The demos are built in the build folder. The demos require command line arguments specifying the input controls for the vehicles. For a description of how to create these control input files, or how to use the default control input files provided, see here.