Termination Conditions

URBAN-SIM uses a set of modular termination conditions to determine when an episode should end. Each condition is implemented as a DoneTerm, and bound via a TerminationsCfg config class.

Taking COCO (a wheeled robot) as an example:

Termination Binding

When robot_name = "coco", the following termination config is used:

@configclass
class TerminationsCfg:
    time_out = DoneTerm(func=loc_mdp.time_out, time_out=True)

    collision = DoneTerm(
        func=nav_mdp.illegal_contact,
        time_out=False,
        params={
            "sensor_cfg": SceneEntityCfg("contact_forces", body_names="body_link"),
            "threshold": 1.0
        },
    )

    arrive = DoneTerm(
        func=nav_mdp.arrive,
        time_out=False,
        params={
            "threshold": 1.0,
            "command_name": "pose_command"
        },
    )

Termination Term Descriptions

• time_out Ends episode after a predefined number of steps.

• collision Terminates if contact force (e.g., from walls or pedestrians) exceeds a threshold.

• arrive Terminates when the robot reaches its goal (within distance threshold).

• (Optional) out_of_region Can be enabled to terminate the episode when the robot leaves a bounded region.

Each DoneTerm can be used to trigger reward terms and is evaluated per timestep. Termination decisions also propagate into curriculum updates and training logs.