Calibrate Odom

Calibrating the Odometry

Note

This section assumes that you have already completed doc_build_car, doc_software_setup, doc_build_car_firmware, and drive_manualcontrol.

One final step that is crucial to get an accurate estimate of the car’s current velocity, and accurate localization and mapping later on, is to calibrate the odometry estimation. On the RoboRacer vehicle, the odometry is estimated from the motor’s ERPM and the current angle of the servo.

Required Equipment

  • Fully built RoboRacer vehicle

  • Pit/Host computer

  • Joystick

  • Tape measure

  • Tape

Calibrating the Steering and Odometry

Now that everything is built, configured, and installed, the odometry of the vehicle needs to be calibrated. The VESC receives input velocities in m/s and steering angles in radians. However, the motor and servo require commands in revolutions per minute (RPM) and servo positions. The conversion parameters will need to be tuned to your specific car.

  1. The parameters in vesc.yaml need to be calibrated. This YAML file is located at:

    $HOME/f1tenth_ws/src/f1tenth_system/f1tenth_stack/config/vesc.yaml

Preparing for Calibration

Note

Before starting, ensure you’ve lifted the car up with a pit stand or a box so the wheels can spin freely.

Checking Motor Rotation Direction

  1. Verify Motor Rotation

    If, when given a positive velocity (or moving forward with the joystick), the motor spins in the reverse direction, swap 2 of the 3 connections from the VESC to the BLDC motor.

    Important

    Before doing this, disconnect the battery from the VESC.

  2. Check VESC Driver Interpretation

    After launching teleop with the bringup launch, echo the /odom topic in a new bash window inside the container:

    ros2 topic echo --no-arr /odom