Chassis

The rolling platform is a Yahboom Ackermann 520M chassis. It provides the frame, the four drive wheels, and the Ackermann steering linkage that the steering servo turns. Everything else on the car - the compute boards, sensors, batteries, and dashboard - is mounted on this chassis.

Parts (Amazon)

How It Works

  • The chassis uses Ackermann steering: the front wheels pivot on a linkage driven by a single steering servo, while the drive comes from JGB37-520 DC motors rated for 12 V and 550 RPM through the AT8236 Motor Controller. This matches how a real car steers, not skid/tank steering.
  • Logical steering commands (0 = left, 90 = center, 180 = right) are turned into servo angles in hardware.py; the linkage geometry translates that into the actual wheel angle.
  • The chassis is the physical reference frame for steering tests. Bench work observed direction-dependent steering return and field testing observed left drift. Those observations can have multiple contributors, including linkage geometry, load, surface, trim, and motor balance; the current motor scales remain neutral at 1.0 on both sides.

Why This Choice

  • An Ackermann chassis produces car-like turning geometry, which keeps the steering-model labels meaningful and matches the target domain (sidewalks/roads) far better than a differential-drive robot base.
  • The 520M is a well-supported, off-the-shelf platform, so effort could go into the autonomy stack instead of fabricating a frame - the same reuse-what-exists reasoning behind the rest of the build.