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System Module

The System Module provides supportive functionalities that manage simulation flow and synchronize system-wide parameters for other core modules like Planning and Control.

This module includes two essential nodes:

  • sim_monitor
  • portal

These nodes operate behind the scenes to ensure temporal consistency and repeatability within simulation scenarios, especially when running in environments like AWSIM.

1. sim_monitor

The sim_monitor node is responsible for calculating the simulation clock rate by subscribing to the /clock topic published by AWSIM. It compares the simulated time and the real-world time to estimate the simulation delay rate (i.e., how fast or slow the simulation is running compared to real time).

Why it's important:

  • This simulation delay rate is published periodically and used in downstream modules such as:
  • behavior_motion_planning: For predicting future object positions.
  • control: For accurate time-based control computations.

By compensating for the simulation speed difference, these modules can make consistent and real-time-aware decisions.

2. portal

The portal node enables scenario looping and repetition by monitoring sudden jumps in vehicle position, which typically occur when the vehicle passes through a portal and respawns at a starting point.

How it works:

  • Subscribes to the GNSS pose topic (/sensing/gnss/pose).
  • Tracks vehicle position over time.
  • Detects significant jumps (beyond a threshold), indicating the vehicle has entered a portal.
  • Publishes a portal message to inform other modules (e.g., Planning) that the scenario has reset.

This functionality is particularly useful in testing and evaluation scenarios where repeatability and automated resets are required.

Summary

The System Module ensures that all other modules in the simple-AV stack are:

  • Aware of time distortion in simulation environments.
  • Synchronized and responsive to resets in simulation flow (e.g., portal teleportation).

By handling these system-level signals, sim_monitor and portal provide a stable backbone for accurate simulation, prediction, and testing behavior.