Obstacles

Using the predefined obstacle templates, a variety of obstacle types can be created which are superimposed on the existing soft-soil road geometry.

Implementation

In order to properly position the obstacle, the X and Y coordinate of the obstacle’s center as well as the THETA angle, which defines its orientation, must be provided, as shown in Fig. 1.

By default, each obstacle is created as deformable, making use of the global soft-soil parameters (see Fig. 2). In order to change its default state, the optional parameter MAT can be set to ‘RIGID’ or a user-defined ‘MAT_LABEL’. More specifically, in the first case, the obstacle is rigid (non-deformable) and the tire-rigid road interaction is implemented using the Fiala tire model (see Fig. 3). On the other hand, in the second case the obstacle is still deformable. However, instead of the global soft-soil parameters, a new set of parameters is used for the obstacle’s region which is defined in the new block ‘MAT_LABEL’, as depicted in Fig. 4. Finally, if the block ‘MAT_LABEL’ cannot be found in the road data (.rdf) file, the simulation proceeds using the global soft-soil parameters.

Obstacle types

In the current tire model, the following obstacle types can be used:
  • Rectangular obstacle
  • Circular obstacle
  • Bump obstacle
  • Ramp obstacle
  • Roof obstacle
  • Sine obstacle
  • Sine-sweep obstacle (Linear/Logarithmic)
  • Plank obstacle (Beveled edges/Round edges)
  • Crown obstacle

Rectangular Obstacle

To create a rectangular obstacle, a new block (RECT_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of obstacle Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Circular Obstacle

To create a circular obstacle, a new block (CIRC_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of obstacle Length
RADIUS Radius of circle obstacle Length
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Bump Obstacle

To create a bump obstacle, a new block (BUMP_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of bump's center Length
RADIUS Radius of bump Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Ramp Obstacle

To create a ramp obstacle, a new block (RAMP_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z_START Z coordinate of obstacle's starting point Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
PHI Phi (inclination) angle of obstacle Angle
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Roof Obstacle

To create a roof obstacle, a new block (ROOF_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z_START Z coordinate of obstacle's starting point Length
Z Z coordinate of obstacle's midpoint Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Sine Obstacle

To create a sine obstacle, a new block (SINE_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of obstacle Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
AMPLITUDE Amplitude of sine wave Length
WAVELENGTH Wavelength of sine wave Length
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Sine-sweep Obstacle

In this obstacle type, the amplitude and the frequency of the sine wave vary as a function of the longitudinal distance s. More specifically, two cases can be distinguished for the calculation of the obstacle’s height .

Linear Sweep

Logarithmic Sweep

To create a sine-sweep obstacle, a new block (SINE_SWEEP_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of obstacle Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
AMPLITUDE_START Amplitude of obstacle's starting point Length
WAVELENGTH_START Wavelength of obstacle's starting point Length
AMPLITUDE_END Amplitude of obstacle's end point Length
WAVELENGTH_END Wavelength of obstacle's end point Length
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
SWEEP_TYPE Sweep type (‘LINEAR’ or ‘LOGARITHMIC’). Optional parameter, default value is ‘LINEAR’ -
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Plank Obstacle

Using a plank obstacle, two different cases can be distinguished regarding the shape of its edges. In detail, beveled edges are used when the BEVEL_EDGE_LENGTH parameter is positive. On the other hand, round edges are created with a negative value of this parameter, where the radius of the corner is equal to |BEVEL_EDGE_LENGTH|.

To create a plank obstacle, a new block (PLANK_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
Z Z coordinate of obstacle Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
BEVEL_EDGE_LENGTH Length of the beveled edge (45° angle). If this parameter is negative, the obstacle is created with round edges, where the radius is equal to |BEVEL_EDGE_LENGTH| Length
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

Crown Obstacle

The height of this obstacle is calculated as a function of obstacle width , crown height , crown coefficient and width-coordinate , using the equation:

Where the parameters and are defined in a new block as functions of the longitudinal distance .

To create a crown obstacle, a new block (CROWN_OBSTACLE block) is necessary in the road data (.rdf) file that contains the following parameters:

Parameter Description Units
X X coordinate of obstacle’s center Length
Y Y coordinate of obstacle’s center Length
LENGTH Length of obstacle Length
WIDTH Width of obstacle Length
THETA Theta (orientation) angle of obstacle Angle
DATA_BLOCK Name of block that contains the table with , and data  
DATA_NUMBER Number of rows in the table of , and data  
UMIN Parameter for tire-rigid road interaction (Fiala tire model) -
UMAX Parameter for tire-rigid road interaction (Fiala tire model) -
CSLIP Parameter for tire-rigid road interaction (Fiala tire model) Force
CALPHA Parameter for tire-rigid road interaction (Fiala tire model) Force
MAT Obstacle’s material. Optional parameter, default value is ‘SOFT_SOIL’ -

OBSTACLES Block

Finally, in order to support more than one obstacle of each type (for example rectangular, circular, and so on), an extra block (OBSTACLES block) can be defined that contains a list of the obstacle names for each type, as shown in Fig. 14. It should be emphasized that this block is necessary only in cases where more than one obstacle of a specific type (for example rectangular, circular, and so on) exists in the model and only for the specific obstacle type. In all other cases, the obstacles are created using the blocks presented previously (RECT_OBSTACLE block for a rectangular obstacle, CIRC_OBSTACLE block for a circular obstacle, etc.). In addition, it should be noted that the obstacle names in each list need to be provided as comma-separated values, as depicted in the following figure.

Property File Examples

Rectangular Obstacle

Circular Obstacle

Bump Obstacle

Ramp Obstacle

Roof Obstacle

Sine Obstacle

Sine-sweep Obstacle

Plank Obstacle

Crown Obstacle