Both front wheels are modulated to start and stop to control steering. The rear wheel is the Vientiane wheel, which plays a supporting role. Track the photoelectricity under the installation of the left and right body respectively. When the sensor on the left side under the car body detects the black line, the main control chip controls the left wheel motor to stop and the car to correct to the left side. When the sensor on the right side under the car body detects the black line, the main control chip controls the right wheel motor to stop and the car to correct to the right side.