HOW IT WORKS.

Your steering angle is normalized in the range [-1, 1] all the way through the drive pipeline. The controller node writes the per-tick command v <m/s> <deg> over USB-CDC to the ESP32, where the angle in degrees is what the servo eventually sees. Before that send, the controller adds one YAML value, steering_trim_deg, from config/controller.yaml. That value starts at 0.0. Nudge it a degree or two and the wheels at zero angle shift with it.

WHAT YOU NEED.

THE PROCEDURE.

bashCopy
# 1. SSH into the Jetson.
ssh racecar@neoracer

# 2. Open the controller YAML and find the trim line.
$EDITOR ~/ros2_ws/src/neoracer_ros2_driver/config/controller.yaml
#   controller:
#     ros__parameters:
#       steering_trim_deg: 0.0   # degrees added to the servo angle

# 3. Roll-test first (Section 04) to see which way it drifts, then nudge:
#      drifts LEFT  at angle 0  ->  steer it right: lower the trim
#      drifts RIGHT at angle 0  ->  steer it left:  raise the trim
#    Step a degree at a time. Half a degree is usually enough at the end.

# 4. Re-launch teleop so the new trim is picked up.
racecar teleop

VERIFY THE CENTER.

This holds the servo at center and the motor at zero so you can roll the car by hand along the tape and watch the drift:

pythonCopy
import racecar_core

rc = racecar_core.create_racecar()

HOLD_S = 8.0
timer = 0.0


def start():
    global timer
    timer = 0.0
    rc.drive.set_speed_angle(0, 0)
    print("Servo verify: holding straight, push the car 1 m along the tape")


def update():
    global timer
    timer += rc.get_delta_time()
    rc.drive.set_speed_angle(0, 0)   # motor at zero, servo centered
    if timer > HOLD_S:
        rc.drive.stop()


rc.set_start_update(start, update)
rc.go()

A pass is finishing within a wheel's width of the line after a metre. A bigger gap means another nudge to the offset and a rebuild.

WHERE IT LIVES.

The trim is a YAML value the controller node reads on launch, so a re-launch is what applies it. There is no colcon build to wait on. Keep your edited controller.yaml in your own copy of the workspace so a re-image does not reset it to zero.

yamlCopy
# ~/ros2_ws/src/neoracer_ros2_driver/config/controller.yaml
controller:
  ros__parameters:
    port:               /dev/osrbot_base
    max_speed_mps:      2.0
    steering_trim_deg:  0.0    # your trim, in degrees
    throttle_channel:   2
    steering_channel:   0
    mode_channel:       4

• A positive steering_trim_deg steers the zero-angle wheels one way, negative the other. Worth confirming the direction on your own car with a roll test.
• The top-speed cap is max_speed_mps on the same file; leave it alone if you only meant to trim the steering.
• Every script that sends a steering angle of 0 now points true ahead, no per-program tweak needed.