How is automatic parking achieved? Illustration of the composition and technical principle of the automatic parking system

Many novice drivers have a hard time understanding parallel parking, a skill that is essential for everyday driving. Parking space is limited in big cities, and maneuvering a car into a tight space has become a must-have skill. Parking is rarely done without some effort, and can lead to traffic jams, nerve fatigue, and bent bumpers. Fortunately, car manufacturers have taken this into account, and the development of technology has provided a solution: the automatic parking function.

Automatic parking is also known as automatic parking. It is a very convenient configuration for novices and saves a lot of effort for veterans. When you find an ideal parking spot, you don't have to toss back and forth. Just press the start button, sit back, and relax. Everything else will be done automatically, completely eliminating the trouble you encounter in parking.

The implementation process of automatic parking

Most of the automated parking technology is used in parallel parking situations. Parallel parking requires the car to be parked parallel to the curb, in a straight line with other parked cars. Most car users need a parking space that is about 1.8 meters longer than the car body to successfully complete parallel parking, although some skilled drivers only need less space.

To parallel park, the driver must follow five basic steps:

1. Drive the car to the front of the parking space and park next to the car in front.

2. Turn the wheel toward the roadside and move the car backwards at about 45 degrees into the parking space.

3. When the front wheels of the car are parallel to the rear wheels of the car in front, the driver straightens the front wheels and continues to reverse.

4. After ensuring a certain distance from the vehicle behind through rear vision, the driver turns the wheel outward from the roadside and turns the front end of the car back into the parking space.

5. Finally, the driver moves the car forward and backward in the parking space until the car is about 0.3 meters away from the roadside.

Existing self-parking cars aren't fully autonomous, but they do make parallel parking easier. The driver still has to control the speed of the car by pressing the brake pedal (the car's idle speed is enough to park it without pressing the accelerator pedal). Then, the car's computer system takes over the steering.

When driving along the road, as long as the speed is less than 36 km/h (the speed setting value of each model will be different), the system will think that the driver intends to park, and the vehicle will start to use the radar probe to automatically detect whether there is a suitable parking space around. The length of the available parking area set by the automatic parking system of general models must be greater than 1.2 meters of the vehicle body before it can be confirmed that the area is within the parking range.

When the automatic parking system finds a suitable parking position and the vehicle is shifted into reverse gear, the system will prompt the driver whether to start the active parking assist function. After confirming the start, the driver can now take both hands off the steering wheel, and the steering wheel will automatically turn to adjust the reverse direction of the vehicle. The driver only needs to control the accelerator and brake to control the speed (when the driver holds the steering wheel, the system will stop working).

During the reversing process, the driver needs to properly control the speed and pay attention to the warning sound of the reversing radar. When the alarm is heard, it means that the car behind is very close. At this time, you need to shift into the forward gear. While the car is moving forward, the system will automatically return the wheel to the correct position of the car. The screen prompts that the parking is completed. Shift to neutral and the parking task is easily completed. (Tip: Some models equipped with automatic parking systems do not automatically return the wheel after reversing into the parking space, and the driver needs to complete it manually)

Composition and technical principle of automatic parking system

The automatic parking system consists of the following components:

1. Ultrasonic sensors : There are 12 sensors in total, located on the front and rear bumpers. They transmit ultrasonic signals , then receive the signals reflected from obstacles and evaluate the distance to obstacles based on the time from transmission to reception. The front radar monitoring distance in front of the vehicle bumper is 100cm, and the rear monitoring distance is 120cm. The left and right front outer distance sensors are used to detect the length and width of the parking space.

2. Parking Positioning System (PTS) Control Unit: Located on the left side of the trunk, it has the following main functions: reading various electronic component input signals, such as vehicle speed, gear status, ignition switch status, electric steering gear status, etc., actuating vehicle distance sensors and warning components, and communicating with the CAN network through the Flex Ray bus .

3. Warning element: The front warning element is integrated into the instrument. When the vehicle speed is lower than 16 km/h, the parking system switches to the measurement mode. The rear warning element is located above the rear windshield. When the vehicle speed is lower than 16 km/h, the warning part lights up to give the driver a visual warning.

4. Electric power steering mechanism: It consists of a rack and pinion steering gear, a torque sensor (A91b1), an electric motor (A91m1) and a steering mechanism control unit (N68). N68 reads the signal of A91b1 and the wheel speed signal from ESP, and activates A91 m1 accordingly, thereby driving the rack and pinion steering gear to realize the steering function.

5. Steering column module control unit: reads the steering wheel angle and steering angular velocity, and communicates with the CAN R network through the Flex Ray bus .

6. Vehicle stability system control unit: It has functions such as adaptive braking, brake force distribution (EBD), anti-lock braking (ABS), anti-skid control (ASR), electronic traction assistance (ETS), and brake assist (BAS). By analyzing the signals from various sensors (such as wheel speed sensors), and then sending correction instructions (correct control instructions) to ABS and ASR, it helps the vehicle maintain dynamic balance so that the vehicle can maintain the best stability under various conditions. In the case of oversteering or understeering, the stabilization effect is more obvious. In the case of oversteering, rear-wheel drive cars often have oversteering, the rear wheels lose control and drift, and ESP will quickly and slightly brake the outer front wheels to stabilize the car (note: braking at this time will not lock the wheels, but is intended to reduce the wheel speed). In the case of understeering, ESP will quickly and slightly brake the inner rear wheel to correct the direction of the vehicle.

Radar probes located around the vehicle measure the distance and angle between itself and surrounding objects, and then use the onboard computer to calculate the operation process and adjust the steering wheel rotation according to the vehicle speed.

The system includes an environmental data acquisition system, a central processor and a vehicle strategy control system . The environmental data acquisition system includes an image acquisition system and an on-board distance detection system, which can collect image data and the distance data of surrounding objects from the vehicle body, and transmit them to the central processor through a data line.

The central processing unit can analyze and process the collected data to obtain the car's current position, target position and surrounding environmental parameters, make automatic parking strategies based on the above parameters, and convert them into electrical signals.

After receiving the electrical signal, the vehicle strategy control system controls the car's driving angle, direction, etc. according to the instructions until it parks.

Different self-parking systems use different methods to detect objects around the car. Some have sensors around the front and rear bumpers that act as both transmitters and receivers . These sensors send signals that bounce off obstacles around the car. The car's computer then uses the time it takes to receive the signal to determine the obstacle's location. Other systems use bumper-mounted cameras or radar to detect obstacles. But the end result is the same: The car detects the parked vehicles, the size of the parking space, and the distance from the curb, and then maneuvers into the space.

Types and development of automatic parking technology

Passive automatic parking

Passive warning system warns the driver of obstacles in front or behind the vehicle when parking. In the process of development, it has evolved from only rear warning to front detection warning when the vehicle moves forward, adding visual images, auxiliary lines and surrounding blind spot warning. The most complex one is the combination of two systems, including reversing radar + 360-degree surround view.

The passive type mainly uses ultrasonic sensors + buzzers + HMI icons to remind the driver of external obstacles to prevent the vehicle from colliding when reversing. It is generally composed of the following functions:

1. Anti-collision sound + image prompt

2. System for measuring parking space size

3. Provide turning angle prompts

4. Provide rear view image and auxiliary line detection

5. 360-degree surround image

The passive type is a system that fully considers the cost. It uses low-cost ultrasonic sensors to realize obstacle detection when reversing. The general distance is 1 meter to 1.5 meters. Consumers have a high acceptance of this type of system.