How does a car reversing radar determine distance?
2 Answers
Car reversing radar determines distance by: judging the distance through sound. The alarm emitted by the reversing radar is a beeping sound at a certain frequency, and the frequency increases as the obstacle gets closer. When the beeping frequency becomes faster and is accompanied by a continuous sound, it indicates that the vehicle is getting closer to the obstacle. The reversing radar mainly consists of ultrasonic sensors, a controller, and a buzzer. Its functions are: 1. Accurately measuring the distance between the rear of the car and the obstacle; 2. Emitting rapid warning sounds to alert the driver to brake when reversing to a dangerous distance; 3. Repeatedly emitting voice warnings to remind pedestrians to pay attention.
I previously studied the principle of reverse parking sensors, which actually rely on ultrasonic distance measurement. The radar probe emits ultrasonic pulses, similar to how we can hear echoes when shouting into a cave. When the ultrasonic waves hit an obstacle behind the vehicle and reflect back, the controller calculates the distance by multiplying the time difference between sending and receiving the sound waves by the speed of sound. Typically, it emits over 30 pulses per second, with different distances corresponding to different frequencies of beeping sounds: 1.5 meters triggers intermittent beeps, 1 meter changes to continuous beeping, and within 0.5 meters, a long warning sound is emitted. If encountering sloped obstacles or thin railings, the reflected waves may weaken, leading to inaccurate distance measurement. In such cases, it's safer to rely on the rearview mirror.
