Intelligent tail gate anti-pinch method based on millimeter wave radar multi-physical field perception

Abstract

The invention discloses a non-contact automobile tail door anti-pinch method based on millimeter-wave radar, which is characterized in that a millimeter-wave radar array, an embedded control unit and a fusion self-adaptive energy judgment threshold and motion track continuity detection module are adopted; the intelligent tail door anti-pinch system is composed of a digital signal processing link based on radio frequency direct acquisition and a tail door state machine information system obtained based on a vehicle bus, whether a human body or an obstacle exists in the area below the tail door or not is monitored in real time after the tail door is opened, if a target exists, the tail door is forbidden to be closed, and in the vehicle door closing process, the vehicle door is prevented from being closed. And if a target is monitored to enter the monitoring range, a high level is immediately output to open the tail gate. Compared with the prior art, the method has the anti-interference detection capability, can accurately identify the closing path of the tail door, can stably operate in a strong light environment and a weak light environment, realizes emergency braking and back-off after the tail door is blocked, provides a solution with high cost performance for the intelligent automobile electric tail door, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of non-contact sensor technology, and in particular to an intelligent tailgate anti-pinch method based on multi-physical field perception of millimeter-wave radar. Background Art

[0002] With the development of automotive intelligence, the electric control of automotive tailgates has become mainstream. With the popularization of electric tailgates, higher requirements are put forward for safety anti-pinch technology. Traditional anti-pinch solutions mostly rely on contact pressure sensors or optical sensors (such as infrared, ultrasonic), which have significant defects. In addition, the existing technology has poor dynamic adaptability to the movement trajectory of the car door, and it is difficult to eliminate the detection blind area or the risk of false triggering.

[0003] The infrared sensor emits infrared light beams (usually in the near-infrared band, with a wavelength of about 850 - 940 nm), and the receiver detects whether the light beam is blocked or reflected. When the tailgate is closed, the sensor array forms a "light curtain". If an obstacle blocks the light beam, the change in the receiver signal triggers the anti-pinch action. The specific implementation is to install multiple groups of infrared transmitters and receivers along the edge of the tailgate to form a dense detection area. When the signal intensity at the receiving end is lower than the preset threshold, an obstacle is determined; the ultrasonic sensor emits high-frequency sound waves (usually 40 - 50 kHz) and measures the time difference of its reflected echo (Time of Flight) to calculate the distance to the obstacle. When an obstacle is detected to enter the preset safe distance during the closing process of the tailgate, the motor is triggered to stop or retract. In addition, some vehicle models will use a visual camera to monitor the movement of the tailgate in real time and use algorithms such as machine learning for anti-pinch recognition.

[0004] In summary, in the non-contact anti-pinch solutions of the existing technology, the infrared sensor solution arranges an infrared emission-reception pair tube array at the edge of the tailgate and detects obstacles through light beam occlusion. Although this solution has a low cost, due to its sensor characteristics, it is vulnerable to strong light interference, unable to detect transparent objects, and has a short detection distance, etc.; the ultrasonic sensor emits 40 - 50 kHz ultrasonic waves and calculates the distance to the obstacle through the echo time. This solution is suitable for dark and dusty environments, has a relatively wide detection range (0.2 - 2 m), but has a low spatial resolution, an increased false triggering rate in rainy and snowy weather (interference from water droplet reflection), and is unable to detect slow-moving objects, such as children crawling, etc.; the advantage of the visual camera lies in its visualization, ability to classify objects (human body, pet, luggage), and support for behavior prediction. However, this solution depends on the lighting conditions (additional lighting is required at night), the additional lighting may affect the recognition effect, etc., and there are also issues such as privacy disputes (video data needs to be stored) and high costs. Summary of the Invention

[0005] The object of the present invention is to provide an intelligent tailgate anti-pinch method based on multi-physical field perception of millimeter-wave radar in view of the deficiencies of the prior art. An intelligent tailgate anti-pinch system based on multi-physical field perception of millimeter-wave radar is adopted, which includes a tailgate state machine information system obtained based on the vehicle bus, a millimeter-wave radar array, an embedded control unit, a multi-resolution background clutter suppression model, an adaptive energy decision threshold and a motion trajectory continuity detection module, and a digital signal processing link architecture based on radio frequency direct sampling. After the tailgate is opened, it monitors in real time whether there are humans or obstacles in the area below the tailgate. If a target exists, the tailgate is prohibited from closing; during the process of closing the tailgate, if it is detected that a target enters the monitoring range, a high level is immediately output to open the tailgate, realizing an intelligent tailgate anti-pinch system with high precision, high real-time performance and strong anti-interference ability, which has good application prospects and commercial development value.

[0006] The object of the present invention is achieved as follows: An intelligent tailgate anti-pinch method based on multi-physical field perception of millimeter-wave radar, which is characterized by adopting an intelligent tailgate anti-pinch system with a millimeter-wave radar array, an embedded control unit, a module integrating an adaptive energy decision threshold and a motion trajectory continuity detection module, a digital signal processing link based on radio frequency direct sampling and a tailgate state machine information system architecture obtained based on the vehicle bus (CAN). After the tailgate is opened, it monitors in real time whether there are humans or obstacles in the area below the tailgate. If a target exists, the tailgate is prohibited from closing. During the process of closing the tailgate, if it is detected that a target enters the monitoring range, a high level is immediately output to open the tailgate.

[0007] The millimeter-wave radar array is integrated in the kinematic pivot area of the tailgate. Through a three-dimensional beamforming algorithm combined with Capon angle measurement technology, spatial adaptive beam optimization is realized; when the tailgate reaches the maximum opening position, a space calibration program is triggered; the space calibration program establishes a rotation transformation matrix between the radar coordinate system and the vehicle body coordinate system based on the minimum variance distortionless response criterion, and completes multi-dimensional feature extraction of the original echo signal through high-resolution angle estimation; The tailgate state machine information system obtained based on the vehicle bus (CAN) includes: a residence monitoring mode (corresponding to the fully open steady state), a dynamic tracking mode (corresponding to the phase change process of closing operation), and a safety locking mode (corresponding to the mechanical locking final state). Each mode realizes smooth switching through a finite state machine.

[0008] The embedded control unit loads a preset power consumption matrix and executes an event-driven power management strategy. An interrupt wake-up type ADC sampling architecture is adopted. After the radar radio frequency front end is activated, the acquisition is started. Precise start and stop are realized through a hardware gating circuit to achieve the optimal solution of power consumption and heat generation.

[0009] The digital signal processing link based on RF direct sampling synchronously calculates I / Q quadrature components during the frequency domain reconstruction process, and uses the Coordinate Rotation Digital Computer (CORDIC) algorithm to complete phase unwrapping.

[0010] When deploying the adaptive filtering algorithm in the intelligent tailgate anti-pinch system, the Capon spatial filtering characteristics are fused to construct a multi-resolution background clutter suppression model. Through the moving target feature extraction engine, an energy spectrum search based on super-resolution angle measurement ability is performed within the dynamically adjusted anti-pinch decision domain.

[0011] The module that fuses the adaptive energy decision threshold and the moving trajectory continuity detection uses the spatial selection characteristics of Capon beamforming to enhance the angle resolution. When the target object parameters meet the anti-pinch decision threshold, it is determined as a valid target. After determining that there is a target within the monitoring range, the system outputs a control signal from the module to the vehicle control system to keep the tailgate in the open state or change it to the open state to achieve anti-pinch.

[0012] The present invention has the following beneficial technical effects and significant technical progress compared with the prior art: 1) Anti-interference detection ability: Based on the micro-Doppler effect of the millimeter-wave radar, it can penetrate environmental interferences such as rain, snow, and dust, and accurately identify the closing path of the tailgate. 2) Full-scenario adaptability: Through the adaptive clutter suppression algorithm, it effectively eliminates signal drift caused by vehicle body vibration and environmental temperature and humidity changes, and can operate stably in strong light and weak light environments. 3) Real-time response and safety: Adopting a dynamic threshold adjustment strategy, it realizes emergency braking and retraction of the tailgate when encountering an obstacle. 4) Integration and cost advantage: By fusing radar signals and vehicle body CAN bus data, redundant sensor deployment is reduced, and the radar module can be hidden inside the tailgate trim panel to avoid damaging the vehicle body appearance. 5) Using domestic millimeter-wave radar to further reduce the cost of the solution, and achieving breakthroughs in safety, environmental robustness, and cost control, providing a high-cost-performance solution for the intelligent vehicle electric tailgate, with good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a flowchart of the present invention; Figure 2 is a schematic installation diagram of the millimeter-wave radar. DETAILED DESCRIPTION OF THE INVENTION

[0014] The intelligent tailgate anti-pinch system based on multi-physical field perception of millimeter-wave radar constructed by the present invention has the following core processes in its technical implementation architecture: 1) Integrate the millimeter-wave radar array in the kinematic pivot area of the tailgate, and achieve airspace adaptive beam optimization through the three-dimensional beamforming algorithm combined with the Capon angle measurement technology. When triggering the space calibration program at the maximum opening position of the tailgate, establish the rotation transformation matrix between the radar coordinate system and the vehicle body coordinate system based on the minimum variance distortionless response criterion, and complete the multi-dimensional feature extraction of the original echo signal through high-resolution angle estimation.

[0015] 2) The tailgate status machine information system obtained based on the vehicle bus (CAN) includes: residence monitoring mode (corresponding to the fully open steady state), dynamic tracking mode (corresponding to the closing operation phase change process), and safety locking mode (corresponding to the mechanical locking final state), and each mode realizes smooth switching through a finite state machine.

[0016] 3) The embedded control unit loads the preset power consumption matrix and executes the event-driven power management strategy. Adopt the interrupt wake-up type ADC sampling architecture, start the acquisition after the radar RF front end is activated, and achieve precise start and stop through the hardware gating circuit to achieve the optimal solution of power consumption and heat generation.

[0017] 4) Construct a digital signal processing link based on direct RF sampling, synchronously solve the I / Q quadrature components during the frequency domain reconstruction process, and use the coordinate rotation digital computer (CORDIC) algorithm to complete the phase unwrapping.

[0018] 5) When deploying the adaptive filtering algorithm, fuse the Capon airspace filtering characteristics and construct a multi-resolution background clutter suppression model. Through the moving target feature extraction engine, perform the energy spectrum search based on the super-resolution angle measurement ability within the dynamically adjusted anti-pinch decision domain.

[0019] The present invention will be further described below in conjunction with specific embodiments. Embodiment 1

[0020] Refer to Figure 1 The present invention realizes high-precision, high-real-time and strong anti-interference tailgate anti-pinch according to the following steps: 1) Multi-dimensional feature extraction of the original echo signal The millimeter-wave radar of the automotive tailgate uses frequency-modulated continuous wave (FMCW), and its transmitted signal is a Chirp signal whose frequency changes linearly with time. After the echo signal is mixed with the transmitted signal, an intermediate frequency signal (IF) is generated, which contains range dimension information and Doppler dimension information (speed). Remove high-frequency noise and interference through band-pass filtering, and adjust the signal amplitude to adapt to the dynamic range of the analog-to-digital converter (ADC) for radar raw signal acquisition.

[0021] 2) Interrupt wake-up type ADC sampling architecture Use a low-pass filter (LPF) to filter out frequency components higher than fs / 2. Adopt an interrupt-wake ADC sampling architecture, which keeps the system in a low-power sleep state usually, and is only awakened by an interrupt when sampling is needed. After sampling, it enters the sleep state again. It is applicable to the application scenario of automotive tailgate anti-pinch, and can further reduce resource consumption while ensuring the efficiency of analog-to-digital conversion.

[0022] 3) Heterogeneous computing architecture to achieve parallel FFT The heterogeneous computing architecture integrates different types of processors, gives full play to their respective advantages, and significantly improves the computing efficiency of FFT. In the anti-pinch system, the FPGA is responsible for real-time FFT calculation and signal preprocessing (filtering, denoising), and the DSP is responsible for running the target detection algorithm (CFAR) and control decision-making. It realizes high-precision ranging and improves the anti-interference ability.

[0023] 4) Multi-resolution background clutter suppression to extract target motion features After the signal is transformed into the frequency domain by FFT, through multi-scale analysis (wavelet transform, multi-resolution decomposition, etc.), the target signal and background clutter are separated at different resolution levels, and the motion features of the target are identified and quantified, covering key motion state information such as speed, distance, direction, and acceleration, so as to improve the sensitivity and accuracy of target detection.

[0024] 5) Dynamically adjust the anti-pinch decision After a series of signal processing, the system conducts an energy spectrum search according to the set decision factors, and adjusts the anti-pinch decision-making scheme in real time based on the state information given by the vehicle-mounted system. The system has three major types of anti-pinch decisions: static, dynamic, and sleep. The system is dynamically adjusted to the corresponding state scheme through the interrupt to receive real-time state information, realizing seamless state switching.

[0025] 6) Adaptive energy decision Currently, mainstream automotive tailgates generally have multiple gears for closing speed. To ensure a high detection rate at significantly different speeds, the present invention adopts adaptive energy threshold judgment. The system will adopt different matching parameters according to the current tailgate closing speed to ensure the detection rate. When the energy is greater than the threshold, it is considered that the target exists. At this time, a high level is output to the vehicle-mounted system through a GPIO interrupt. At this time, the tailgate controlled by the vehicle-mounted system will be braked urgently to achieve anti-pinch. After this cycle ends, the next target detection continues; if the energy is always less than the threshold, it is considered that there is no target, and the next round of target detection continues. Specifically, when the detected energy is greater than the threshold, it is determined that the target exists, and a control signal is output to the vehicle-mounted system to brake the tailgate immediately; if the detected energy is less than the threshold, it is determined that there is no target, then return, and re-perform the threshold judgment in steps 1) to 6).

[0026] Refer to Figure 2, Hardware Configuration and Installation of the Intelligent Tailgate Anti-Pinch System with Multi-Physical Field Sensing for the Millimeter-Wave Radar in the Invention Architecture: 1) A domestically developed millimeter-wave radar sensor is used as the main detection unit, which is compatible with international mainstream millimeter-wave radar modules such as TI and Infineon through a standardized interface protocol. It has high-precision ranging, a wide field of view (±60°), and anti-interference characteristics. The radar module is installed at the center of the bottom of the car tailgate, with the installation angle horizontal to the ground, ensuring that when the tailgate is fully opened (the highest point), the radar beam covers a fan-shaped area 1m below the tailgate. The radar module communicates with the vehicle control system through the CAN bus, receives the tailgate status signals (fully opened, closing, fully closed), and outputs anti-pinch control signals.

[0027] 2) To improve the real-time performance of signal processing in the embedded system, this embodiment uses a dedicated hardware signal processing unit to achieve fast Fourier transform acceleration. A data transmission channel is established through the direct memory access mechanism, and the time-domain signals collected by the converter are transmitted to the dedicated storage area in batches. This segmented data transfer strategy not only reduces the memory resource occupancy but also significantly improves the operation efficiency through the parallel processing mechanism. The core processing unit immediately enters the low-power state after completing the operation, effectively reducing the overall system energy consumption. Its low-latency characteristic is particularly suitable for dynamic control systems that require real-time monitoring, avoiding safety risks caused by signal processing delays while ensuring detection sensitivity.

[0028] 3) When the millimeter-wave radar monitors the area below the tailgate, it receives two types of reflected signals: dynamic target signals (such as the human body); static background clutter (such as the ground, vehicle body metal parts, fixed obstacles). The reflection intensity of static clutter is usually much higher than that of dynamic targets. If not eliminated, it may lead to system misjudgment (for example, mistaking ground reflection for an obstacle). This system uses an adaptive differential signal processing mechanism to accurately extract the full-phase response characteristics of moving target echoes in the time-frequency domain, providing a high-resolution polarization feature parameter set for the multi-modal feature classification algorithm (typical samples such as human biological motion and rigid box structure). On this basis, a dynamic clutter suppression model based on a single-pole recursive feedback architecture is calibrated through an adaptive iterative update mechanism, significantly suppressing the static reflection interference in the environmental background while maintaining the phase continuity of moving targets. 4) The system innovatively constructs an adaptive distance threshold regulation strategy based on motion state perception to achieve dynamic optimization of anti-pinch detection under the constraint of the tailgate kinematic model. When the tailgate closing instruction is triggered, the embedded control unit activates the periodic timing control module to generate time-varying distance threshold parameters based on the preset kinematic equation. This parameter exhibits a non-linear attenuation characteristic synchronized with the angular displacement of the tailgate. Through the interrupt service routine (ISR), the system realizes real-time distance threshold refreshing at the millisecond level. Combining with the spatio-temporal joint filtering algorithm, the system achieves refined control and safety protection of the tailgate movement, while avoiding possible interference from rear passengers to radar detection, effectively distinguishing the multi-path scattering characteristics of real obstacles from passengers / sundries, and significantly improving the system robustness while ensuring safety.

[0029] The above embodiments are only for further illustration of the present invention, and are not intended to limit this patent. All equivalent implementations of the present invention should be included within the scope of the claims of this patent.

Claims

1. A non-contact anti-pinch method for vehicle tailgate based on millimeter-wave radar, characterized in that, This method uses a millimeter-wave radar array, an embedded control unit, a module that fuses an adaptive energy decision threshold and motion trajectory continuity detection, and an intelligent tailgate anti-pinch system with a digital signal processing link based on direct radio frequency sampling and a tailgate status machine information system architecture obtained through the vehicle bus. After the tailgate is opened, it continuously monitors the area below the tailgate for the presence of a human body or an obstacle. If a target is detected, the tailgate closing is prohibited. During the tailgate closing process, if a target is detected entering the monitoring range, a high level is immediately output to open the tailgate. The millimeter-wave radar array is integrated in the kinematic pivot area of the tailgate. Through a three-dimensional beamforming algorithm combined with Capon angle measurement technology, spatial adaptive beam optimization is achieved. When the tailgate reaches its maximum opening position, a space calibration program is triggered. The space calibration program establishes a rotation transformation matrix between the radar coordinate system and the vehicle body coordinate system based on the minimum variance distortionless response criterion, and completes the multi-dimensional feature extraction of the original echo signal through high-resolution angle estimation. The tailgate status machine information system obtained through the vehicle bus includes: a dwell monitoring mode, a dynamic tracking mode, and a safety locking mode, and smooth switching between the modes is achieved through a finite state machine.

2. The non-contact anti-pinch method for a vehicle tailgate based on a millimeter-wave radar according to claim 1, characterized in that The embedded control unit loads a preset power consumption matrix, executes an event-driven power management strategy, adopts an interrupt-wake-up ADC sampling architecture, starts acquisition after the radar radio frequency front end is activated, and achieves precise start and stop through a hardware gating circuit to obtain the optimal solution for power consumption and heat generation.

3. The non-contact anti-pinch method for a vehicle tailgate based on a millimeter-wave radar according to claim 1, wherein The digital signal processing link based on direct radio frequency sampling synchronously calculates the I / Q quadrature components during the frequency domain reconstruction process, and uses the coordinate rotation digital computer algorithm to complete phase unwrapping.

4. The non-contact vehicle tailgate anti-pinch method based on millimeter-wave radar according to claim 1, characterized in that An adaptive filtering algorithm is deployed in the intelligent tailgate anti-pinch system to construct a multi-resolution background clutter suppression model. Through a moving target feature extraction engine, an energy spectrum search based on super-resolution angle measurement ability is performed within a dynamically adjusted anti-pinch decision domain.

5. The non-contact automobile tailgate anti-pinch method based on millimeter-wave radar according to claim 1, characterized in that, The module that fuses an adaptive energy decision threshold and motion trajectory continuity detection uses the spatial selection characteristics of Capon beamforming to enhance the angle resolution. When the target object parameters meet the anti-pinch decision threshold, it is determined as a valid target. After determining that there is a target within the monitoring range, the system outputs a control signal from the module to the in-vehicle control system to keep the tailgate in the open state or change it to the open state to achieve anti-pinch.

6. The non-contact anti-pinch method for a vehicle tailgate based on a millimeter-wave radar according to claim 1, wherein The automotive millimeter-wave radar uses frequency-modulated continuous wave, and its transmitted signal is a Chirp signal whose frequency changes linearly with time. The echo signal is mixed with the transmitted signal to generate an intermediate frequency signal including range dimension information and Doppler dimension information. High-frequency noise and interference are removed through band-pass filtering, and the signal amplitude is adjusted to adapt to the dynamic range of the analog-to-digital converter for radar raw signal acquisition.

7. The non-contact anti-pinch method for a vehicle tailgate based on a millimeter-wave radar according to claim 2, wherein, The interrupt-wake-up ADC sampling architecture is woken up by an interrupt when sampling is required, and enters the sleep state after sampling, keeping the system in a low-power sleep state during normal radar raw signal acquisition.

8. The non-contact vehicle tailgate anti-pinch method based on millimeter-wave radar according to claim 1 or claim 4, characterized in that The adaptive energy decision threshold and motion trajectory continuity detection module adopts different matching parameters according to the current tailgate closing speed. When the energy is greater than the threshold, it is considered that the target exists. At this time, a high level is output to the vehicle system through GPIO interruption, and the tailgate system controlled by the vehicle system brakes emergently to achieve anti-pinch. After this cycle ends, the next target detection is continued; if the energy is always less than the threshold, it is considered that there is no target, and the next round of target detection is continued.

9. The non-contact vehicle tailgate anti-pinch method based on millimeter-wave radar according to claim 3, wherein The multi-resolution background clutter suppression model separates the target signal and background clutter through multi-scale analysis of wavelet transform and multi-resolution decomposition for the frequency domain signal after FFT conversion, and identifies and quantifies the motion state information of the target's speed, distance, direction, and acceleration.

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