Roads Terrain
This 12-minute video shows some advanced features of CarSim. Roads are shown at 4:00, terrain at 4:30. June 2020.
synched plot and video
The 3D road model uses a Reference Path and several Configurable Function dataset to define elevation near the path. Click for more detail.

VS Roads and VS Terrain

BikeSim, CarSim, and TruckSim include multibody models that simulate vehicle dynamics under driver/rider control on a 3D ground surface. This 3D surface is a major part of the environment in which the vehicles operate.

VS Road Model

The VS road model defines elevation geometry and friction using S-L coordinates associated with a VS Reference Path. This allows detailed information to be concentrated in the region of interest (i.e., on or near the road path).

The 3D surface is defined as a collection of up to 200 road surfaces, where each road surface is in turn defined using a 2D VS Reference Path.

The properties of each surface are defined with Configurable Functions of S and L. These include friction, rolling resistance, and relative elevation. There is also a Configurable Function that defines a component of elevation as a function of only station.

Connections between adjacent surfaces can be specified to allow the simulation to automatically move points from the moving bodies (tire contact points, moving object locations, etc.) between surfaces automatically. Alternatively, VS Commands can be used to switch from one surface to another, or to redefine the properties of the surface that is already resident in memory.

The VS Browser uses the road datasets to automatically generate animator shapes to allow visualization of the ground geometry and its relationship with vehicle motions in animations.

VS Terrain

The VS Terrain is an alternate method to provide a terrain representation to the math models. It uses a single 3D mesh to represent the ground using global X-Y-Z coordinates, and stores the data in a binary file with extension .vsterrain.

This format exists as a means to make use of 3D ground data from other sources in VS Solvers. Two methods are used to generate .vsterrain files:

  1. Use VS Scene Builder to assemble a 3D scene, and connect it to a simulation using the using the Scene: External Import screen. The scene will include a .vsterrain file that will be used to provide the 3D ground geometry.
  2. Use the VS Terrain Utility (accessed from the Tools menu) to convert an existing .fbx file to .vsterrain format. (FBX file can be made by most 3D modeling tools.)

Road Roughness

Roughness profiles allow realistic road roughness inputs to be used in simulated tests without requiring the extensive amounts of data needed to fully map a 3D surface, especially in cases where the vehicle is not following a straight path. These can make use of data routinely measured by highways agencies, or generated with suitably filtered noise from random number generators.

A "wandering profile" is defined as an increment of elevation Z defined as a function of distance travelled, where the distance travelled is calculated in the math model by integrating the forward speed for the front wheels, and adding the distance between axles to get the proper delay of inputs for other axles. CarSim and TruckSim models include two wandering profiles; BikeSim includes one.

multiple roads
Road roughness is added with "wandering profiles" based on paths followed by the vehicle wheels. This figure is from a 2011 SAE technical paper "Road Characterization for the Simulation of Automotive Vehicle Dynamics." Click the image for the full view.
Contact Us
Subscribe to Newsletter