The working principle of ultrasonic sensor in car reversing radar

The full name of the reversing radar is “reversing anti-collision radar”, also called “parking aid”, which is a safety aid when the car is parked or reversing. composed of other parts.

The working principle of ultrasonic sensor in car reversing radar

It can inform the driver of the surrounding obstacles with sound or a more intuitive Display, which relieves the driver from the trouble of looking around when parking, reversing, and starting the vehicle, and helps the driver to eliminate blind spots and blurred vision. defects, improve driving safety. Ultrasound (referring to mechanical waves with frequencies above 20 kHz) is a special sound wave with basic physical properties such as sound wave refraction, reflection, and interference. The ultrasonic ranging sensor sends out ultrasonic waves through the ultrasonic transmitter, and the time difference between the time when the receiver receives the transmitted ultrasonic waves to measure the distance length.

The ultrasonic transmitter emits an ultrasonic signal in a certain direction outside, and starts timing at the time of transmitting the ultrasonic wave. The ultrasonic wave propagates through the air, and if it encounters an obstacle during the propagation, it will immediately return and propagate back. The ultrasonic receiver receives the reflection. The time of the wave stops immediately. The propagation speed of ultrasonic waves in the air is 340m/s. The timer can measure the distance (s) from the launch point to the obstacle by recording the time t, namely: s=340t/2.

Ultrasonic energy consumption is relatively slow, the distance of propagation in the medium is relatively long, the penetration is strong, the distance measurement method is simple, and the cost is low. However, it has certain limitations in measuring distance under high speed. This is because the transmission speed of ultrasonic waves is easily affected by weather conditions. In different weather conditions, the transmission speed of ultrasonic waves is different, and the propagation speed is slow. When When the car is driving at high speed, the use of ultrasonic ranging cannot keep up with the real-time change of the car’s distance, and the error is large. On the other hand, the ultrasonic scattering angle is large and the directivity is poor. When measuring a distant target, the echo signal will be relatively weak, which will affect the measurement accuracy. However, in short-distance measurement, ultrasonic ranging sensors have great advantages.

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