Perception in Applications

The Application Simulator bundles a perception module for vehicle units. This module allows to emulate basic detection of other traffic entities using a field of view filter. To warrant fast simulation MOSAIC utilizes a spatial index, which allows for quick pre-selection of relevant entities.

Configuration

The perception module can be configured in the mosaic/scenarios/<scenario_name>/application/application_config.json. The most important configuration is the choice of a perception backend and its parameters. MOSAIC implements a Trivial, QuadTree and Grid backend, with QuadTree being the default setting. Below is an example of a application_config.json on how to configure the Grid index.

{
    "perceptionConfiguration": {
        "perceptionBackend": "Grid",
        "gridCellWidth": "5m",
        "gridCellHeight": "5m"
    }
}

For more information on choosing a backend for your scenario see here .

In order to use the perception module from your application it has to be enabled first. Viewing angles can be defined between 0° and 360°, while the range has to be larger than 0. Configuration works analogously to the AdHoc- and Cell- Communication-Modules and is usually done at startup:

private final static VIEWING_ANGLE = 120; // [degree]
private final static VIEWING_RANGE = 100; // [meter]

@Override
public void onStartup() {
    // set up the configuration for the perception module
    SimplePerceptionConfiguration perceptionModuleConfiguration = 
        new SimplePerceptionConfiguration(VIEWING_ANGLE, VIEWING_RANGE);
    // enable the perception module using the defined configuration
    getOs().getPerceptionModule().enable(perceptionModuleConfiguration);  
}

Currently, the module only supports the perception of other vehicles, but this will be extended in the future.

Usage

To get a list of vehicles in perception range the getPerceivedVehicles()-method is called:

// get list of vehicles in perception range
List<VehicleObject> perceivedVehicles = getOs().getPerceptionModule().getPerceivedVehicles();
// log the list of perceived vehicle IDs
getLog().infoSimTime(this, "Perceived vehicles: {}",
        perceivedVehicles.stream().map(VehicleObject::getId).collect(Collectors.toList()));

The VehicleObject-class contains information about the perceived vehicles' position, speed and heading.

Perception Modifiers

The perception module can be configured with different PerceptionModifiers, which can be used to emulate occlusion, false negatives, position areas, etc. MOSAIC already implements three modifiers, SimpleOcclusionModifier, WallOcclusionModifier, DistanceModifier and PositionErrorModifier.

Modifier Description Image
SimpleOcclusionModifier Emulates occlusion in a simplified manner by comparing angles between perceived vehicles and requiring a minimum angle between all other perceived vehicles.
WallOcclusionModifier Emulates occlusion of vehicles by buildings. Requires building information in the scenario database, which can be imported to the database using the --import-buildings option in scenario-convert.
DistanceModifier Stochastic modifier that reduces perception probability with the distance to the ego vehicle.
PositionErrorModifier Applies a gaussian error to lateral and longitudinal distances of perceived vehicles.

To configure modifiers they have to be passed to the PerceptionModuleConfiguration:

private void enablePerceptionModule() {
    // filter to emulate occlusion
    SimpleOcclusionModifier simpleOcclusionModifier = new SimpleOcclusionModifier(3, 5);
    // filter to emulate occlusion by buildings
    WallOcclusionModifier wallOcclusionModifier = new WallOcclusionModifier();
    // filter to reduce perception probability based on distance to ego vehicle
    DistanceModifier distanceModifier = new DistanceModifier(getRandom(), 0.0);
    // filter adding noise to longitudinal and lateral
    PositionErrorModifier positionErrorModifier = new PositionErrorModifier(getRandom());

    SimplePerceptionConfiguration perceptionModuleConfiguration = new SimplePerceptionConfiguration(
            VIEWING_ANGLE, VIEWING_RANGE,
            simpleOcclusionModifier, wallOcclusionModifier, distanceModifier, positionErrorModifier
    );
    getOs().getPerceptionModule().enable(perceptionModuleConfiguration);
}

All configured modifiers will be executed in order of configuration.

Note: Evaluating perception modifiers requires many list operations, which is costly in terms of performance. Depending on the size of your scenario you may want to limit usage.