A Method for Identifying Reverse State and Switching Warning Function Based on Millimeter-Wave Radar

Abstract

The present invention relates to a method for identifying the reverse state and switching the warning function based on a millimeter-wave radar. By processing the original ADC data of the radar, the reverse state is identified. The specific steps include: performing distance-dimensional and Doppler-dimensional FFT processing on the radar data to generate an RD map; screening target points through the CFAR algorithm; analyzing the energy distribution of Doppler lines to determine the stationary, reverse, or forward state of the vehicle, and automatically switching the modes of the LCA warning and RCTA warning systems according to the vehicle state. During the stationary stage, the point cloud in the RCTA warning area is allowed to form a track in advance, accelerating the warning response speed when reversing. The method provided by the present invention does not require additional hardware support, reducing the system cost; achieving lossless installation, and effectively preventing misjudgment by comprehensively judging the Doppler index in the RD map and the proportion of stationary point cloud; being able to quickly and accurately judge the vehicle state and improving the warning response speed.

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 (LCA) and Rear Cross Traffic Alert (RCTA) systems 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 LCA of the lane change assist radar system warns of longitudinally approaching targets on both sides. Currently, there are two ways to obtain the vehicle gear information: The first is to obtain the vehicle gear information through the vehicle's On-Board Diagnostics (OBD) 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. Moreover, it has a high dependence on the vehicle's OBD interface, and compatibility issues may occur due to OBD protocol differences. The second way is to break the power line 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. However, this method requires breaking the power line connected to the reverse light and then manually wrapping the insulation layer again, which cannot achieve a non-destructive installation. Most customers cannot accept the method of breaking the wire for 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 damage 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:

[0005] S1. Obtain the original ADC data through the vehicle-mounted millimeter-wave radar, and preprocess the original ADC data to obtain a range-Doppler (RD) map and point cloud data;

[0006] 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 ;

[0007] S3. Determine whether the vehicle is in a stationary state;

[0008] 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 it is continuously judged 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 step S4 is entered; otherwise, step S5 is entered.

[0009] S4. Warn 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.

[0010] S5. Determine whether the vehicle is in a reverse state;

[0011] If the Doppler line index mutates from 0 to dopBins - 1, where dopBins represents the number of Doppler units, and the Doppler line indices , in the next two consecutive frames are detected. If the Doppler line indices , 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. Here, m represents a preset threshold used to characterize the range of the reverse speed within two consecutive frames.

[0012] S6. The LCA warning and RCTA warning automatically switch to the mode when the vehicle is in a reverse state.

[0013] S7. Determine whether the Doppler line index changes from 0 to 1. If it is satisfied and the Doppler line indices , in the next two consecutive frames 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 RCTA warning automatically switch to the mode when the vehicle is in a forward state.

[0014] Preferably, the preprocessing includes:

[0015] Perform range-dimensional FFT and Doppler-dimensional FFT processing on the original ADC data to obtain range and speed data;

[0016] Non-coherent integration is performed on multi-channel data to obtain a range-Doppler map;

[0017] CFAR detection is performed on the range-Doppler map, and FFT processing in the angular dimension is performed on the points selected by CFAR detection to obtain angular data.

[0018] Preferably, when the vehicle is in a stationary state in step S4, rear cross-traffic alert (RCTA) is performed for rear-crossing targets and lateral collision alert (LCA) is performed for targets approaching longitudinally from both sides. Tracks are allowed to be formed by the point clouds in the warning area, and only the targets in the LCA warning area are allowed to trigger warnings.

[0019] Preferably, when the vehicle is in a reverse state in step S6, tracks are not allowed to be formed by the point clouds in the LCA warning area, RCTA warning is turned on and LCA warning is turned off.

[0020] Preferably, when the vehicle is in a forward state in step S7, tracks are not allowed to be formed by the point clouds in the RCTA warning area, LCA warning is turned on and RCTA warning is turned off.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] By judging the ratio of the Doppler index with the strongest energy in the RD map to the stationary point cloud, the present invention effectively prevents misjudgment, improves the reliability of system warnings, and allows the point clouds in the RCTA warning area to form tracks during the stationary stage, accelerating the warning response speed during reverse driving; at the same time, the method proposed by the present invention does not rely on the OBD interface or power cord of a specific vehicle model, enhances versatility, reduces hardware and installation costs, and realizes lossless installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] To further elaborate on 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 implementation manners, structures, features, and effects of the present invention as follows.

[0025] In order to achieve fast and accurate judgment of the vehicle reverse state and warning function without additional hardware, this embodiment includes the following steps:

[0026] S1. Original ADC data is obtained through an in-vehicle millimeter-wave radar, and the original ADC data is preprocessed to obtain a range-Doppler (RD) map and point cloud data;

[0027] The preprocessing includes:

[0028] Perform range - dimension FFT (1D) and Doppler - dimension FFT (2D) processing on the original ADC data to obtain range and velocity data;

[0029] Perform non - coherent integration on multi - channel data to obtain a range - Doppler map;

[0030] Perform CFAR detection on the range - Doppler map, and perform angle - dimension FFT processing on the points selected by CFAR detection to obtain angle data;

[0031] 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 , in this embodiment , the number of Doppler cells dopBins is 128, and the Doppler line index corresponds to , where positive velocity means moving away, and corresponds to the Doppler index in ascending order of absolute value , negative velocity means moving closer, and corresponds to the Doppler index in ascending order of absolute value , represents the maximum unambiguous velocity, represents the velocity resolution;

[0032] S3. Determine whether the vehicle is in a stationary state;

[0033] If the value of the Doppler line index is 0 and the number of point clouds with a speed of 0 meets a 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 it can be continuously judged for 10 frames. If all 10 frames meet the conditions, then the vehicle stationary flag is set to 1, and step S4 is entered; otherwise, step S5 is entered;

[0034] S4. Give early warnings for 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 rear cross - traffic targets RCTA and for 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;

[0035] S5. Determine whether the vehicle is in a reverse state;

[0036] If the Doppler line index Mutate from 0 to dopBins - 1, where dopBins represents the number of Doppler units, and detect the Doppler cues for 2 consecutive frames after detection 、 . If the Doppler cues 、 are both between dopBins - 1 and dopBins - 1 - m, it is determined that the vehicle is in a reverse state, and step S6 is entered; otherwise, step S7 is entered. m represents a preset threshold used to characterize the interval where the reverse speed is within 2 consecutive frames. The value of m can be adjusted appropriately 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;

[0037] S6. The LCA warning and RCTA warning are automatically switched to the mode when the vehicle is in a reverse state. It is not allowed for the point cloud in the LCA warning area to form a track. The RCTA warning is turned on and the LCA warning is turned off;

[0038] S7. Determine whether the Doppler cue changes from 0 to 1. If it is satisfied and the subsequent 2 consecutive frame Doppler cues 、 are both between 1 and m, it is determined that the vehicle is in a forward state. The LCA warning and RCTA warning are automatically switched to the mode when the vehicle is in a forward state. It is not allowed for the point cloud in the RCTA warning area to form a track. The LCA warning is turned on and the RCTA warning is turned off.

[0039] In this embodiment, it is judged 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 turn, 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 reverse; using the last Doppler line and the last few Doppler lines in 2 consecutive frames as the judgment conditions for the start of reverse can quickly and accurately judge the reverse state; using the first Doppler line and the first few Doppler lines in 2 consecutive frames as the judgment conditions for exiting the reverse state ensures a quick exit.

[0040] The above are only the preferred embodiments of the present invention and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content 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 recognizing the reverse state based on a millimeter-wave radar and switching warning functions, characterized in that It 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; 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 Doppler clue 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 condition is met, the vehicle stationary flag is set to 1, and step S4 is entered; otherwise, step S5 is entered. S4. Give early warnings for 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; S5. Determine whether the vehicle is in a reverse state; Doppler clue index Mutates from 0 to dopBins - 1, where dopBins represents the number of Doppler units, and the Doppler clue index for 2 consecutive frames after detection and , if the Doppler clue index and are both between dopBins - 1 and dopBins - 1 - m, it is determined that the vehicle is in a reverse state and step S6 is entered; otherwise, step S7 is entered. Here, m represents a preset threshold used to characterize the interval in which the reverse speed is located within 2 consecutive frames of time; S6. The LCA warning and the RCTA warning automatically switch to the mode when the vehicle is in a reverse state; S7. Determine the Doppler cue index Whether it changes from 0 to 1. If so and the Doppler cue indices and of the next two consecutive frames are both between 1 and m, it is determined that the vehicle is in the forward state, and the LCA warning and RCTA warning are automatically switched to the mode when the vehicle is in the forward state.

2. A method for identifying the reverse state based on a millimeter-wave radar and switching warning functions according to claim 1, characterized in that, The preprocessing includes: Perform range-dimensional FFT and Doppler-dimensional FFT 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.

3. A method for identifying the reverse state and switching the warning function based on a millimeter-wave radar according to claim 1, characterized in that, When the vehicle is in a stationary state in step S4, give early warnings for rear cross-traffic targets (RCTA) and for targets approaching longitudinally on both sides (LCA). Allow the point cloud in the warning area to form a track, and only allow the targets in the LCA warning area to trigger an early warning.

4. A method for switching the recognition and warning functions of the reverse state based on a millimeter-wave radar according to claim 1, characterized in that, When the vehicle is in a reverse state in step S6, do not allow the point cloud in the LCA warning area to form a track, turn on the RCTA warning and turn off the LCA warning.

5. A method for identifying the reversing state based on a millimeter-wave radar and switching the warning function according to claim 1, characterized in that When the vehicle is in a forward state in step S7, do not allow the point cloud in the RCTA warning area to form a track, turn on the LCA warning and turn off the RCTA warning.

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