Ultrasonic sensor ranging and car reversing radar sensor principle

Solve the car reversing radar - the working principle of the ultrasonic sensor. The reversing radar is called "Reversing Anti-collision Radar", also called "Parking Aid Device". It is a safety auxiliary device for parking or reversing cars. It is composed of ultrasonic sensors (commonly known as probes), controllers and monitors (or buzzers). Part of the composition.

It can inform the driver of obstacles around with the sound or more intuitive display, relieve the trouble caused by the driver's parking, reversing and starting the vehicle, and help the driver to remove the blind spots and blurred vision. Defects improve driving safety.

ultrasonic parking sensor principle

Ultrasonic (referring to mechanical waves above 20 kHz) is a special kind of sound wave with basic physical properties such as sound wave refraction, reflection and interference. The ultrasonic distance measuring sensor emits ultrasonic waves through the ultrasonic transmitting device, and measures the distance length by receiving the time difference of the transmitted ultrasonic waves through the receiver.

The ultrasonic transmitter emits an ultrasonic signal to a certain direction in the outside, and starts timing at the same time as the ultrasonic wave is emitted. The ultrasonic wave propagates through the air, and an obstacle encountered in the process of propagation will immediately return and propagate back, and the ultrasonic receiver receives the reflection. The time of the wave stops immediately. The propagation speed of the ultrasonic wave in the air is 340m/s, and the timer can measure the time from the launch point to the obstacle by recording the time t.

ultrasonic parking sensor principle 1

The length of the distance between the obstacles (s), ie: s = 340t/2.

Ultrasonic energy consumption is slow, the distance traveled in the medium is relatively long, the penetration is strong, the method of ranging is simple, and the cost is low. However, it has certain limitations in measuring distance at high speeds. 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 the car is driving at a high speed, the use of ultrasonic ranging cannot keep up with the car's distance in real time, and the error is large. On the other hand, the ultrasonic scattering angle is large and the directivity is poor. When measuring a target at a relatively long distance, the echo signal is relatively weak, which affects the measurement accuracy. However, ultrasonic distance measuring sensors have great advantages in short-distance measurement.

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