Project visual identity

Wireless Brains • Practical Robotics Project

Record, Map, and Relocalize with AprilTags

Practical assignment workflow, record a trajectory, rebuild and optimization references offline, and evaluate relocalization with distance and heading metrics.

Start Practical Work See Results Open on GitHub

Practical Work Flow

  1. Record telemetry and tag detections.
  2. Build reference trajectory and tag map offline optimization.
  3. Relocalize live robot pose against record trajectory.
  4. Evaluate deviation metrics and visualization outputs.

Results

Organized by real-robot scenarios and simulation validation .

Phase A: Recording

Real-Robot Scenario 1: Recording

Scenario View

Real robot scenario 1 overview

Recording / Driving Session

Output 027 - Basic Trajectory

Real scenario 1 recording trajectory output 027 basic

Output 027 - Trajectory with Axes

Real scenario 1 recording trajectory output 027 with axes

Additional Scenario Views

Real-Robot Scenario 2: Recording

Recording / Driving Session

Scenario View

Real robot scenario 2 overview

Output 020 - Basic Trajectory

Real scenario 2 recording trajectory output 020 basic

Output 020 - Trajectory with Axes

Real scenario 2 recording trajectory output 020 with axes

Phase B: Relocalization

Real-Robot Scenario 1: Relocalization

Relocalization Session Video

Additional Scenario Views

Real scenario 1 alternative angle

Relocalization Point Photos

Relocalization Output Graphs

Real-Robot Scenario 2: Relocalization

Relocalization Session Video

Notes

This scenario includes video evidence and trajectory outputs; no still-point photo set was captured.

Validation in Simulation: Recording + Relocalization

Reference world: limo_ws/src/gz_apriltag_env/worlds/walls_apriltag_limo.sdf

Simulation Environment

Walls AprilTag simulation environment

Simulation Summary

Offline optimized trajectory, ground-truth comparison, and tag-map consistency were validated on the walls scenario.

Simulation Output Graphs

Simulation Videos

Relocalization Demo 1

Relocalization Demo 2

Key Metrics

Metric Value Comment
Mean Distance to Path -- m Lower is better
P95 Distance -- m Robustness indicator
Mean |Heading Error| -- deg Orientation consistency

Practical Work Example

Important: both real and simulation practical sessions require manual driving via joystick/teleop during the teach run.

Suggested student exercise:

  1. Record one run in simulation or on robot.
  2. Generate reference trajectory and map outputs.
  3. Run online relocalization and capture RViz evidence.
  4. Report distance and heading metrics with interpretation.

Simulation Annexes

Two annex simulations are provided to support the practical work:

  1. Annex A - Parking + Control Demo: simulated parking workflow with control integration.
  2. Annex B - Experiment Validation: same pipeline used to validate recording and relocalization experiments in simulation.

Annex A Commands

cd limo_ws
source /opt/ros/humble/setup.bash
bash profiles/build_sim.sh
bash profiles/launch_sim_parking.sh

Annex B Commands

cd limo_ws
source /opt/ros/humble/setup.bash
bash profiles/build_sim.sh
bash profiles/launch_sim_tags_dataset.sh
bash profiles/launch_teleop_joy_sim.sh

Validation scenario file: limo_ws/src/gz_apriltag_env/worlds/walls_apriltag_limo.sdf

Students who want to study or implement additional control laws can use: PythonRobotics.

These control methods can be connected to the outputs of this pipeline .

Scope Boundaries

In Scope

  • Trajectory recording and offline reconstruction
  • Online nearest-point relocalization
  • Distance and heading deviation metrics

Out of Scope

  • Full global navigation in arbitrary worlds
  • Dynamic obstacle avoidance stack
  • Multi-robot mission planning

Quick Start Commands

cd limo_ws
source /opt/ros/humble/setup.bash
bash profiles/build_real.sh
# or
bash profiles/build_sim.sh