Reversing state recognition and early warning function switching method based on millimeter wave radar

Abstract

The invention relates to a millimeter wave radar-based reversing state identification and early warning function switching method, which realizes reversing state identification by processing radar original ADC data, and specifically comprises the following steps: carrying out distance dimension and Doppler dimension FFT processing on radar data to generate an RD map; screening target points through a CFAR algorithm; doppler linear energy distribution is analyzed, the static, reversing or advancing state of the vehicle is judged, the modes of an LCA early warning system and an RCTA early warning system are automatically switched according to the state of the vehicle, the point cloud of an RCTA early warning area is allowed to form a track in advance in the static stage, and the early warning response speed during reversing is increased; the method provided by the invention does not need extra hardware support, so that the system cost is reduced; lossless installation is achieved, and misjudgment is effectively prevented by comprehensively judging the proportion of Doppler clue indexing and static point clouds in the RD map; the vehicle state can be quickly and accurately judged, and the early warning response speed is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive active safety, and particularly to a method for identifying the reverse state based on a millimeter-wave radar and switching warning functions. Background Art

[0002] With the continuous development of automotive intelligence and autonomous driving technologies, the lane change assist radar system (LCA) and the rear cross traffic alert system (RCTA) have become important components of intelligent vehicle safety functions. These systems use on-vehicle radar sensors to continuously monitor the traffic environment around the vehicle and provide warnings to the driver to improve driving safety. In the prior art, the lane change assist radar usually switches different working modes according to different gears of the vehicle. When the vehicle is in reverse gear, the rear cross traffic alert system warns of rear cross traffic targets. When the vehicle is in other gears, the lane change assist radar system LCA warns of longitudinally approaching targets on both sides. Currently, there are two ways to obtain vehicle gear information: The first way is to obtain the gear information of the vehicle through the vehicle's OBD (On-Board Diagnostics) interface. The OBD interface is connected to the vehicle's CAN bus, and the data on the CAN bus is parsed to determine which gear the vehicle is in. This method does not require additional wiring and is relatively simple to install. However, it requires a separate control box to parse the vehicle CAN bus data, which not only increases the hardware cost and complexity of the system, but also requires additional software to support the parsing of CAN data, and has a high dependence on the vehicle's OBD interface, resulting in compatibility problems due to OBD protocol differences. The second way is to break the power supply wire of the vehicle's reverse light and lead a separate wire to the radar end. The radar system determines whether the vehicle is in reverse gear by detecting the level change of the IO port. This method is simple to implement, but it requires breaking the power supply wire connected to the reverse light and then manually wrapping the insulation layer again, which cannot achieve lossless installation. Most customers cannot accept the way of wire-breaking installation, and the installation process is complex, increasing the installation man-hours and costs. Summary of the Invention

[0003] In view of this, the present invention provides a method for identifying the reverse state based on a millimeter-wave radar and switching warning functions, which can solve the problems of high cost, high complexity in judging the vehicle state and inability to install additional hardware without loss in the existing methods, and can quickly and accurately judge the vehicle reverse state and warning functions without additional hardware.

[0004] To achieve the above object, a method for identifying the reverse state based on a millimeter-wave radar and switching warning functions of the present invention includes the following steps: S1. Obtain the original ADC data through the vehicle-mounted millimeter-wave radar, and preprocess the original ADC data to obtain the range-Doppler (RD) map and point cloud data; S2. Poll the RD data, calculate the sum of the energy values of all range cells corresponding to each Doppler line, and search for the Doppler line index with the largest sum of energy values ; S3. Determine whether the vehicle is in a stationary state; If the value of the Doppler line index is 0 and the number of point clouds with a speed of 0 meets the preset threshold, it is determined that the vehicle is in a stationary state, and the determination is continuously made for n frames and the total time does not exceed 0.5 seconds. If the conditions are met, the vehicle stationary flag is set to 1, and step S4 is entered; otherwise, step S5 is entered; S4. Give early warnings for the targets approaching longitudinally on both sides, and the lane change assist radar (LCA) and the rear cross traffic alert system (RCTA) automatically switch to the mode when the vehicle is in a stationary state; S5. Determine whether the vehicle is in a reverse state; If the Doppler line index mutates from 0 to dopBins - 1, where dopBins represents the number of Doppler units, and the Doppler line index is continuously detected for 2 frames 、 , if the Doppler line index 、 are both in the range from dopBins - 1 to dopBins - 1 - m, it is determined that the vehicle is in a reverse state, and step S6 is entered; otherwise, step S7 is entered, where m represents a preset threshold used to characterize the interval in which the reverse speed is located within 2 consecutive frames; S6. The LCA warning and the RCTA warning automatically switch to the mode when the vehicle is in a reverse state; S7. Determine whether the Doppler line index changes from 0 to 1. If it is satisfied and the subsequent continuous 2-frame Doppler line indices 、 are both in the range from 1 to m, it is determined that the vehicle is in a forward state, and the LCA warning and the RCTA warning automatically switch to the mode when the vehicle is in a forward state.

[0005] Preferably, the preprocessing includes: Perform range-dimensional FFT and Doppler-dimensional FFT processing on the original ADC data to obtain range and speed data; Perform non-coherent accumulation on multi-channel data to obtain the range-Doppler map; Perform CFAR detection on the range-Doppler map, and perform angle-dimensional FFT processing on the points selected by the CFAR detection to obtain angle data.

[0006] Preferably, when the vehicle is in a stationary state in step S4, a Rear Cross Traffic Alert (RCTA) is issued for a rear cross target and a Longitudinal Collision Alert (LCA) is issued for targets approaching longitudinally from both sides. The point cloud in the warning area is allowed to form a track, and only the targets in the LCA warning area are allowed to trigger the warning.

[0007] Preferably, when the vehicle is in a reverse state in step S6, the point cloud in the LCA warning area is not allowed to form a track, the RCTA warning is turned on and the LCA warning is turned off.

[0008] Preferably, when the vehicle is in a forward state in step S7, the point cloud in the RCTA warning area is not allowed to form a track, the LCA warning is turned on and the RCTA warning is turned off.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: By judging the ratio of the Doppler cue with the strongest energy in the RD map to the stationary point cloud, the present invention effectively prevents misjudgment, improves the reliability of the system warning, and allows the point cloud in the RCTA warning area to form a track during the stationary phase, thus accelerating the warning reaction speed during reverse; at the same time, the method proposed by the present invention does not rely on the OBD interface or power line of a specific vehicle model, enhances the versatility, reduces the hardware and installation costs, and realizes a lossless installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific embodiments, structures, features and their effects of the present invention as follows.

[0012] In order to realize the rapid and accurate judgment of the vehicle reverse state and warning function without additional hardware, the present embodiment includes the following steps: S1. Obtain the original ADC data through an in-vehicle millimeter-wave radar, and preprocess the original ADC data to obtain a range-Doppler (RD) map and point cloud data; The preprocessing includes: Perform range-dimensional FFT (1D) and Doppler-dimensional FFT (2D) processing on the original ADC data to obtain range and velocity data; Perform non-coherent accumulation on multi-channel data to obtain a range-Doppler map; Perform CFAR detection on the range-Doppler map, and perform angle-dimensional FFT processing on the points selected by the CFAR detection to obtain angle data; S2. Poll the RD data, calculate the sum of the energy values of all range cells corresponding to each Doppler line, and search for the Doppler line index with the largest sum of energy values , in this embodiment, the speed measurement range of the radar is , the number of Doppler units dopBins is 128, and the Doppler index corresponds to , where the positive speed indicates moving away, and the Doppler index corresponds to the absolute value from small to large , the negative speed indicates approaching, and the Doppler index corresponds to the absolute value from small to large , represents the maximum unambiguous speed, represents the speed resolution; S3. Determine whether the vehicle is in a stationary state; If the Doppler index value is 0 and the number of point clouds with a speed of 0 meets the preset threshold, which is set to half of the total number of point clouds in the environment in this embodiment, then it is determined that the vehicle is in a stationary state, and it is continuously judged for n frames and the total time does not exceed 0.5 seconds. In this embodiment, the frame time T is 50 ms, and 10 frames can be continuously judged. If all 10 frames meet the conditions, the vehicle stationary flag is set to 1, and step S4 is entered; otherwise, step S5 is entered; S4. Give early warnings for the targets approaching longitudinally on both sides. The lane change assist radar LCA and the rear cross-traffic alert system RCTA automatically switch to the mode when the vehicle is in a stationary state, give early warnings for the rear cross-traffic targets RCTA and give early warnings for the targets approaching longitudinally on both sides LCA. Allow the point clouds in the warning area to form tracks, and only allow the targets in the LCA warning area to trigger early warnings. It usually takes a few tenths of a second for the targets in the RCTA warning area to form tracks, so as to quickly trigger early warnings when it is determined to be reversing later; S5. Determine whether the vehicle is in a reversing state; If the Doppler index suddenly changes from 0 to dopBins - 1, dopBins represents the number of Doppler units. After detection, the Doppler index for two consecutive frames , if the Doppler index for two consecutive frames are both in the range from dopBins - 1 to dopBins - 1 - m, then it is determined that the vehicle is in a reversing state, and step S6 is entered; otherwise, step S7 is entered. m represents a preset threshold used to characterize the interval where the reversing speed is located within two consecutive frame times. The value of m can be appropriately adjusted according to the speed resolution and the frame time T. In this embodiment, the speed resolution is 0.1 m / s, the frame time T is 50 ms, and the value of m is set to 2; S6. The LCA warning and RCTA warning are automatically switched to the mode where the vehicle is in the reverse state. It is not allowed for the point cloud in the LCA warning area to form a track. The RCTA warning is enabled and the LCA warning is disabled. S7. Determine the Doppler cue Whether it changes from 0 to 1. If it is satisfied and the consecutive two frames of Doppler cues 、 Are both between 1 and m, it is determined that the vehicle is in the forward state. The LCA warning and RCTA warning are automatically switched to the mode where the vehicle is in the forward state. It is not allowed for the point cloud in the RCTA warning area to form a track. The LCA warning is enabled and the RCTA warning is disabled.

[0013] In this embodiment, it is determined whether the vehicle is in a stationary state by the ratio of the Doppler cue with the strongest energy in the RD data to the stationary point cloud, which is used as a prerequisite for judging the reverse gear of the vehicle in sequence, effectively preventing misjudgment. At the same time, during the stationary phase of the vehicle, it is allowed for the point cloud in the RCTA warning area to form a track in advance, accelerating the warning response speed during actual reversing. Using the last Doppler line and two consecutive frames of the last few Doppler lines as the judgment conditions for the start of reversing can quickly and accurately judge the reversing state. Using the first Doppler line and two consecutive frames of the first few Doppler lines as the judgment conditions for exiting the reversing state ensures a quick exit.

[0014] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for reversing state recognition and warning function switching based on millimeter wave radar, characterized in that: The following steps are involved: S1. Obtaining raw ADC data through a vehicle-mounted millimeter-wave radar, and preprocessing the raw ADC data to obtain a range-Doppler RD graph and point cloud data; S2. Poll RD data, calculate the sum of the energy values ​​of all distance units corresponding to each Doppler line, and search for the Doppler line index with the largest sum of energy values. ; S3, determining whether the vehicle is in a stationary state; If the Doppler line index If the value of is 0 and the number of point clouds with a speed of 0 meets the preset threshold, the vehicle is judged to be stationary, and the judgment is performed continuously for n frames and the total time does not exceed 0.5 seconds. If the condition is met, the vehicle stationary flag is set to 1 and the process goes to step S4, otherwise, the process goes to step S5; S4: Warning of targets approaching longitudinally on both sides, the lane change assist radar LCA and the rear cross traffic alert system RCTA automatically switch to the mode when the vehicle is stationary; S5, determining whether the vehicle is in a reversing state; If the Doppler line index From 0 to dopBins-1, dopBins indicates the number of Doppler units, and the Doppler line index of two consecutive frames after detection. , , if the Doppler line index , If both are between dopBins-1 and dopBins-1-m, the vehicle is judged to be in the reversing state and the process goes to step S6; otherwise, the process goes to step S7, where m represents a preset threshold value, which is used to characterize the interval of the reversing speed within two consecutive frames. S6, LCA warning and RCTA warning automatically switch to the mode when the vehicle is in reverse state; S7. Determine Doppler line index Whether it changes from 0 to 1, if it is satisfied and the Doppler line index of the next two consecutive frames , If both are between 1 and m, the vehicle is judged to be in a forward state, and the LCA warning and RCTA warning are automatically switched to the mode in which the vehicle is in a forward state.

2. The method for switching the reversing state recognition and warning function based on millimeter wave radar according to claim 1 is characterized in that: Preprocessing includes: Performing distance dimension FFT and Doppler dimension FFT processing on the original ADC data to obtain distance and speed data; Perform non-coherent accumulation on multi-channel data to obtain the range-Doppler map; The range-Doppler image is subjected to CFAR detection, and angle-dimensional FFT processing is performed on the points selected by the CFAR detection to obtain angle data.

3. The method for switching the reversing state recognition and warning function based on millimeter wave radar according to claim 1 is characterized in that: When the vehicle is stationary in step S4, an early warning RCTA is issued for the rearward crossing target and an early warning LCA is issued for the longitudinally approaching targets on both sides, and the point cloud in the early warning area is allowed to form a track, and only the targets in the LCA early warning area are allowed to trigger an early warning.

4. The method for switching the reversing state recognition and warning function based on millimeter wave radar according to claim 1 is characterized in that: When the vehicle is in the reversing state in step S6, the point cloud in the LCA warning area is not allowed to form a track, the RCTA warning is turned on and the LCA warning is turned off.

5. The method for switching the reversing state recognition and warning function based on millimeter wave radar according to claim 1 is characterized in that: When the vehicle is in the forward state in step S7, the point cloud in the RCTA warning area is not allowed to form a track, the LCA warning is turned on and the RCTA warning is turned off.

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