# 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

- 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.