OpenCRG Road Model

The OpenCRG Road Model (CRG = 'Curved Regular Grid') is based on the open source code delivered at http://www.opencrg.org/

The website states about the background of this road model:

'Its objective is the provision of a series of open file formats and tools for the detailed description of road surfaces.

This knowledge and a whole new series of tools including a new C-API shall be made available to the broad public by means of the OpenCRG® initiative. Users shall be enabled to use all data, libraries and code samples on this website with minimum opensource licensing restrictions.'

For details about the use and format of the CRG road files is referred to the users manual available at the website. Below the use of CRG within Adams is explained.

The OpenCRG road can be used with any Adams Tire tire model.

In general the position of the CRG measured road data will not match with the required position for your (vehicle model). There are two options to change the position of the road:

By default the messaging level is set to writing out (fatal) errors only (level 1). Changing the messaging level can be done by setting the environment variable MSC_CRG_MESSAGE_LEVEL:

Visualization of the OpenCRG roads is supported within Adams Car and Adams View. The OpenCRG road grid will be visualized using default settings for grid and overall road size. The maximum number of grid datapoints used in these default settings can be changed using an environment variable MSC_CRG_MAX_VIS_POINTS:MSC_CRG_MAX_VIS_POINTS = 10000.

However, the user can specify his own detailed preferences for visualization by adding his specification in a $ROAD_CRG_VISUALIZATION data block in the .crg file.

Patches (in red) with detailed grids can be shown by adding $ROAD_CRG_VISUALIZATION_PATCH_# blocks within the $ROAD_CRG_VISUALIZATION data block, see the example below.

The defined start, end and increment values of patches may be modified by the visualization routines to fit the patch in the global grid size of the road.

By default the friction on the CRG road is one: The interaction forces predicted by the tire model are scaled with a factor one. It is possible to define specific road friction scaling factors by supplying Adams Tire a second '.crg formatted file' that contains friction scaling factors (instead of road height values).

This '.crg formatted file' should have the same name as the .crg file with the road height values, but the extension of the file should read .crgf.

If the user supplies a <road_file_name>.crg file for a simulation, Adams Tire will look for a second file with the name <road_file_name>.crgf with road friction scaling values. If that file is not found, the road friction scaling will be set to one.

The .crg files can also be used for the desired path on the x-y plane in case of a ‘Full-Vehicle Analysis → Course Event' or a ‘Full-Vehicle Analysis → Adams SmartDriver’ analysis. The x and y coordinates are derived by converting the u at v = 0 coordinates towards the x, y coordinate system. Also the ‘Full-Vehicle Analysis → Path Optimization’ tool can deal with the .crg files.

When quasi-statics does not converge, setting the following environment variable may help:

The road normal setting of RGR road is upwards by default. If one would need to include the effect of the road height changes, following environment variable needs to be set:

OpenCRG assumes the same width over the whole length of the road. In practice it may occur that at some sections of a road no data could be measured over the complete width. Typically those data points are stored as Nans. Within Adams Tire, by default these Nans will be replaced by zero road height values. OpenCRG also offers another option for treating the Nans: keeping the road height as last value.

In other to change the Nan treatment option one can use the environment variable MSC_OPENCRG_NAN_MODE. Following options are available:

 

In some cases the OpenCRG will list messages about the content of the file. The messages as shown below or similar can be ignored and have no effect on the outcome of your simulation: