The RTL-SDR site highlights the work of Humpelstilzchen in getting a robot to drive towards a 433 MHz beacon transmitter

The experiment used a 433 MHz module to send out an FSK beacon.

On the robot two antennas are used for the time difference of arrival/pseudo-doppler direction finding technique, and PIN diodes are used to rapidly switch between the antennas. A GNU Radio script running on a Humming Board single board computer computes the TDOA/pseudo-doppler algorithm.

RTL-SDR Post - https://www.rtl-sdr.com/building-an-rf-direction-finding-robot-with-an-rtl-sdr/

Hackaday - Wild Thumper based ROS robot - https://hackaday.io/project/25406-wild-thumper-based-ros-robot/