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How do Parking Sensors Work?

12/26/2020

Ⅰ Introduction

The parking sensor also called "parking aid", is mainly composed of ultrasonic sensors, controllers, and displays. It helps the driver "see" the invisible things in the rearview mirror, and inform the driver of the obstacles around the driver by sound or a more intuitive display. The parking sensor removes the trouble caused by the driver's front, rear, left, and right visits when parking, reversing and starting the vehicle, and helps the driver to eliminate the defects of blind spots and blurred vision. The parking sensor also has certain blind spots, including too low and too thin obstacles and ridges.

How Reverse Parking Sensor works in a car?


Ⅱ Working principle of parking sensors

When backing the car, the parking sensor uses the principle of ultrasonic waves. The ultrasonic sensor installed on the rear bumper sends ultrasonic waves to the obstacle and reflects the sound wave, calculates the actual distance between the car body and the obstacle, and then prompts the driver to stop.

  Working of the parking sensor

Working of the parking sensor

When the car is in R gear, the parking sensor will automatically start. Through the controller, the ultrasonic sensor at the rear bumper controls the ultrasonic emission. The ultrasonic wave is reflected by obstacles, and the ultrasonic sensor receives the reflected ultrasonic wave and sends it to the amplifier circuit. The ultrasonic sensor calculates the propagation speed in the medium by using the time from the transmission of the ultrasonic signal to the reception of the echo signal. The data is processed by the single-chip microcomputer, and then the distance and direction of the obstacle are displayed on the display to remind the driver to operate in time.

Ⅲ The main function of parking sensors

parking sensor 

parking sensor

1 Accurately measure the distance between the rear of the vehicle and the nearest obstacle;

2 When reversing to the limit distance, a rapid warning sound can be issued to remind the driver to pay attention to braking;

3 Voice warning sounds can be repeated to remind pedestrians to pay attention to.

Ⅳ Basic components of parking sensors

The parking sensor is a safety auxiliary device when the car is parking or reversing. It can notify the driver of the obstacles around the driver by sound or a more intuitive display, eliminating the troublesome when parking, reversing and starting the vehicle. It helps the driver to eliminate the defects of blind spots and blurred vision. The parking sensor is mainly composed of ultrasonic sensors, controllers and displays or buzzers, etc.

 components of parking sensors

components of parking sensors

1. Ultrasonic sensor

 

The main function of the ultrasonic sensor is to send and receive ultrasonic signals, then input the signals into the host, and display them through the display device.

 Working of the ultrasonic sensor

Working of the ultrasonic sensor

When the controller sends an electrical signal to the ultrasonic sensor, the piezoelectric sheet of the ultrasonic sensor vibrates to generate ultrasonic waves. Due to the structure of the circular piezoelectric sheet, the emitted ultrasonic waves have a certain directivity, and the beam section is similar to an ellipse, so the ultrasonic sensor’s detection range is limited. Generally, the detection angle on the horizontal plane is 120°, and the detection angle on the vertical plane is 60°, as shown in Figure 2.

It is common to use a transmitter-receiver integrated sensor, that is to say, both transmitting and receiving ultrasonic waves are completed by the same ultrasonic sensor.

In this integrated sensor system, there are generally only two wires connected between the ultrasonic sensor and the controller. The transmitted electrical signal and the returned electrical signal are input to the controller through these two wires. Both the transmitted signal of the ultrasonic sensor and the after-vibration signal will cover or interfere with the echo signal, thus causing the parking sensor system to lose its detection function after being below a certain distance. This is one of the reasons why the detection range of the general parking sensor must be greater than 0.3m. If the distance is less than this distance, the parking sensor cannot distinguish the signal and can only sound a long warning.

In theory, the smaller the aftershock, the smaller the minimum detection distance. The best case is that there are no aftershocks so that the ultrasonic sensor can cover a larger range. However, it is impossible to determine whether the ultrasonic sensor is working normally during the system self-test. Therefore, people use the aftershock characteristics of the ultrasonic sensor to determine whether the ultrasonic sensor is intact by detecting the aftershock signal of the ultrasonic sensor itself through the controller. Therefore, in actual production, the ultrasonic sensor has a certain range of aftershocks, and the controller checks the detection results according to the pre-set range value, so as to determine whether the ultrasonic sensor meets the requirements. It reminds the driver whether the system is normal by the buzzer sound.

In short, due to the directivity of the ultrasonic beam emitted by the ultrasonic sensor and the existence of the after-vibration of the ultrasonic sensor itself, the parking sensor system is not foolproof in practice. It has detection blind spots, so more and more parking sensor systems integrate the reversing imaging system, which can more intuitively and accurately judge the situation behind the vehicle.

2. Controller

 

The controller processes the signal to calculate the distance and orientation between the vehicle body and the obstacle. The controller transmits a sine wave pulse to the sensor, processes the received signal, and obtains the corresponding distance value, and then communicates with the display. The main function of the controller is filtering and calculation. The controllers of different brands of parking sensor systems may be different, but the principles are basically the same.

In automobiles, the controller is generally installed around the dashboard, while the ultrasonic sensor is installed on the front and rear bumpers, and transmits signals through long wires. The long line will inevitably produce some noise, so the controller must filter these noises. The beam of the ultrasonic sensor is not regular, but a directional beam with a cross-section that is approximately elliptical. In the process, the beam will inevitably have some misjudgments. For example, the ultrasonic sensor may occasionally "sweep the floor" (when there is no obstacle behind the car, it always detects a fixed distance between 40-60cm, that is, the distance between the ultrasonic sensor and the ground). Therefore, in practice, the control circuit will use technical means to process the echo signal of the ultrasonic sensor to ensure that the system has sufficient sensitivity, but will not cause false alarms.

3. Display or buzzer

 

When the sensor detects that the distance between the car and the obstacle reaches a dangerous distance, the system will send an alarm through the display and buzzer to remind the driver. The display provides corresponding distance alarm sound according to the distance.

Ⅴ Vehicle backup camera

After years of development, the parking sensor system has been upgraded with technology and improved performance, and applied to various models, such as trucks, buses, school buses, combine harvesters, corn harvesters, passenger cars, construction machinery, etc. No matter in terms of structure and appearance, or in terms of performance and price, today's products have their own characteristics. Digital display, screen display, and multi-function mirror display are more commonly used.

 Vehicle reverse image

Vehicle reverse image

The car backup camera system makes the situation behind the car more intuitive when reversing. It is one of the most practical configurations for reversing safety. When the reverse gear is engaged, the system will automatically turn on the high-definition reversing camera located at the rear of the car, and clearly display the rear status on the reversing LCD screen, allowing you to accurately grasp the rear road conditions, and reversing is as confident as forward.

The reversing image system can be seen clearly even through infrared rays at night. The antimagnetic, shockproof, waterproof, and dustproof performance of professional vehicle ultrasonic sensors has been further improved. The car display adopts TFT true color and has no signal interference and no flicker after anti-magnetic treatment. It can receive two videos at the same time and can play VCD and DVD without a decoder. At the same time, it has the functions of reversing visual automatic level conversion and automatic switch. The dashboard and endoscope display can clearly display the information behind the car through the on-board camera at the rear of the car. Two reversing rear-view cameras can also be installed at the same time to achieve no blind spots when reversing.

The car reversing image is a series of overall systems, and it can also be added by the camera device and the on-board display. Of course, the 360-degree panoramic visual system makes up for the image that can only be provided by radar or a single rear-view camera. The panoramic visual system can have four video outputs, namely the front, back, left, and right. It is controlled by remote control and can automatically switch screens. The video can be composed of four videos or a single video.

Ⅵ Comparison of vehicle backup camera and parking sensor

1 Advantages and disadvantages of parking sensor

 

The parking sensor can detect the situation behind the vehicle in real-time and prompt the driver with sound and graphics so that the driver can easily obtain the situation behind the vehicle when reversing. Now many cars not only have a parking sensor at the rear but also a radar ultrasonic wave at the front of the sensor. And the front-end radar can automatically start when driving at low speeds, which greatly increases safety.

parking sensor 

parking sensor

However, the shortcomings of the parking sensor are also obvious. Because of the accuracy problems, the parking sensor cannot accurately indicate. So the parking sensor often screams but the actual distance is still there. Moreover, radar ultrasonic sensors cannot detect small obstacles, obstacles with a certain height behind the vehicle. For example, when you are reversing, there is a ditch behind, or a cable for a telegraph pole, the parking sensor cannot detect it. I remember that there was such an accident in the community last week. When the driver was reversing, the rear of the car hit the anti-theft window of the residents on the first floor. The reason is that the anti-theft window is close to 1 meter from the ground, and this height is not detected by the parking sensor, and the anti-theft window protrudes nearly 60 cm from the wall. Because the parking sensor can only detect the wall, it indicates that there is still a distance. In fact, the rear of the car is already approaching the security window.

2 Advantages and disadvantages of vehicle backup camera

 

The reversing image can intuitively view the video behind the vehicle. This is a very safe method because you can see the true distance to the vehicle behind the display screen. This is why some people cannot accurately grasp the distance to the vehicle behind using the parking sensor. Most people can grasp the distance of the car after changing to the reversing image. Some advanced car backup camera can also be linked to the steering wheel to display real-time trajectories on the screen, which is a very useful function for novices. And the backup camera is easy to install. Generally, the reversing image of ordinary single output only needs to connect the positive pole of the power link wire to the power positive of the car reversing light, and the negative power link wire can be connected to the negative or ground (GND) of the reversing light. You can simply understand how to arrange the cable according to the different models of the car. The camera can be installed in a hole where it is easy to install.

However, the backup camera also has disadvantages, that is, the field of view is limited. The blind spots on both sides of the vehicle body are too large, and the upper part of the vehicle is also a blind spot. So don't just stare at the screen when using the reversing image, but also cooperate with the rearview mirrors on both sides to solve the blind spots on both sides, and cooperate with the rearview mirrors in the car to solve the blind spots on the upper rear of the vehicle.

Ⅶ Recommendations

1 If you prefer to install simply, just install the backup camera;

2 If you are accustomed to observing the rearview mirror and want to have a warning sound for auxiliary group parking, then choose the parking sensor;

3 If you think you need dual installation protection, that is, both video and sound functions, then you can choose to install a visual parking sensor;

4 Install the parking sensor and the backup camera. For example, when reversing, the rear distance can be accurately grasped through the backup camera. When observing the left and right rearview mirrors and the interior rearview mirror and cannot see the display screen, the sound of the parking sensor can prompt us to broadcast the obstacles behind. We can't always stare at the screen of the reversing image when reversing, after all, there are still blind spots. Nowadays, many cars are basically equipped with parking sensors and reversing images at the same time. Some cars can also display the reversing video and the parking sensor information separately when reversing, which is very convenient and easy to use.

Any interest please feel free contact us.


Venus Zhao    images      

Email:  Venus@kaimte.com

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