An optimized method for vehicle speed measurement based on in-vehicle radar

Abstract

The present invention relates to an optimized method for vehicle speed measurement based on on-vehicle radar, comprising the following steps: performing distance dimension and Doppler dimension FFT processing on the original ADC data obtained by the radar to obtain an RD map; performing CFAR processing on the RD map to screen out valid point clouds; performing angle dimension FFT processing on the point clouds to obtain distance, speed, and angle information; calculating the ground distance unit range according to the pitch angle and installation height of the radar antenna; judging the reliability of the vehicle speed of the current frame; polling all the point clouds of the current frame, finding out the maximum Doppler unit index corresponding to each distance unit, calculating the corresponding speed and matching it with the current vehicle speed; using the speed of the distance unit with the highest matching degree to assist in updating the vehicle speed; the method provided by the present invention effectively solves the problem that it is difficult for on-vehicle radar to accurately identify the vehicle speed when the number of point clouds is insufficient or the environment is complex, significantly improves the vehicle speed identification accuracy and stability of the on-vehicle radar system in various environments, and reduces the dependence of the system on the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle-mounted radar systems, and in particular to a vehicle speed measurement optimization method based on a vehicle-mounted radar. Background Art

[0002] The on-board radar system is an important component of modern automobile safety and driving assistance. It detects objects and obstacles around the vehicle by transmitting and receiving radio waves, thereby providing information about the distance, speed and position of surrounding objects; this data information is crucial for automobile safety and convenience functions, such as adaptive cruise control ACC, automatic emergency braking AEB, blind spot detection BSM, lane keeping LKA and forward collision warning FCW.

[0003] At present, vehicle-mounted radar speed recognition technology mainly obtains the vehicle speed through the vehicle-mounted lane change auxiliary radar to filter out stationary targets in the environment. When the vehicle speed cannot be obtained through the vehicle OBD (On-board Diagnostics, on-board automatic diagnostic system), it relies on the following methods: (1) The vehicle speed calculation method based on point cloud speed, which obtains point cloud data in the environment through the vehicle-mounted radar, filters out point clouds that are stationary relative to the ground, and calculates their speed to determine the vehicle speed. However, when there are smooth guardrails on both sides of the road or the radar detection range is very open, it is difficult to form an effective point cloud, resulting in the inability to normally identify the vehicle speed; (2) The vehicle speed calculation method based on the RD map, which calculates the vehicle speed through the position of the Doppler line with the strongest energy in the RD map. However, in an open environment, it is easily interfered by strong reflective targets in motion (such as moving vehicles), resulting in deviations in the vehicle speed calculation. The existing vehicle-mounted radar speed recognition technology is difficult to accurately and reliably identify the vehicle speed when the point cloud data is insufficient or the environment is complex, and has certain limitations. Summary of the invention

[0004] In view of this, the present invention provides a vehicle speed measurement optimization method based on a vehicle-mounted radar. By combining the pitch angle and installation angle of the radar antenna, the distance unit range of the ground echo can be more accurately located, and the speed information of the Doppler unit is used to match the current vehicle speed, thereby effectively improving the accuracy of vehicle speed recognition. The method provided by the present invention can solve the problem in the prior art that the vehicle-mounted radar is difficult to accurately identify the vehicle speed when the number of point clouds is insufficient or the environment is complex, improve the accuracy and reliability of vehicle speed recognition, reduce the dependence of the vehicle-mounted radar system on the environment, and enhance the practicality and stability of the vehicle-mounted radar system in various environments.

[0005] To achieve the above object, the present invention provides a vehicle speed measurement optimization method based on a vehicle-mounted radar, which specifically comprises the following steps:

[0006] S2. Calculate the ground distance unit range according to the pitch angle of the vehicle-mounted radar antenna Calculate the ground distance unit range based on the installation height h of the vehicle-mounted radar ;

[0007] S3. Determine the vehicle speed of the current frame Is it reliable? If the vehicle speed of the current frame is reliable, go to step S4; otherwise, end the current frame and enter the next frame;

[0008] S4. Poll all the point clouds in the current frame. If there is no distance unit of the point cloud within the ground distance unit range , it is determined that the echo in the current distance segment comes from the ground, and the continuous frame number num2 is counted, and then go to step S5;

[0009] S5. Doppler unit speed matching;

[0010] S501. Screen and obtain the Doppler unit index with the largest peak value in each distance unit within the ground distance unit range , and calculate the corresponding speed for each Doppler unit index , and the expression is: ;

[0011] ;

[0012] wherein, represents the speed resolution, represents the number of distance units within;

[0013] S502. Determine whether the current frame speed matches the speed corresponding to each Doppler unit index . If they match, increment the counter of the corresponding distance unit by 1; otherwise keep the value unchanged;

[0014] S6. Determine the distance unit for ground vehicle speed reference ;

[0015] S7. Update the vehicle speed of the current frame to .

[0016] Preferably, the preprocessing includes:

[0017] Perform range-dimensional FFT and Doppler-dimensional FFT on the original ADC data;

[0018] Perform non-coherent accumulation on multi-channel data to obtain a range-Doppler map;

[0019] ​Perform CFAR detection on the range-Doppler map, and perform angle-dimensional FFT on the points selected by CFAR detection to obtain angle information.

[0020] Preferably, calculating the ground range cell range includes:

[0021] Calculate the closest distance when the pitch beam irradiates the ground , and the expression is:

[0022] ;

[0023] Calculate the farthest distance when the pitch beam irradiates the ground , and the expression is:

[0024] ;

[0025] where h represents the installation height of the vehicle-mounted radar;

[0026] Through the range resolution Calculate the closest distance , the farthest distance corresponding range cells , , and the expression is:

[0027] ;

[0028] ;

[0029] where and values are rounded up.

[0030] Preferably, compare the current frame vehicle speed and the previous frame vehicle speed , if it satisfies:

[0031] ;

[0032] ;

[0033] where represents the preset vehicle speed threshold,

[0034] Count the continuous frame number num1 that meets the conditions and compare it with the preset frame number threshold , if the continuous frame number num1 is greater than the preset frame number threshold , then it is determined that the current vehicle speed is reliable.

[0035] Preferably, calculate the speed corresponding to each Doppler cell index The absolute value of the difference from the current frame speed , the expression is:

[0036] ;

[0037] When is satisfied, it is determined that the two speeds match.

[0038] Preferably, the steps of obtaining the distance unit for the ground vehicle speed reference include:

[0039] Determine whether the num2 reaches a preset threshold , if it reaches the preset threshold, then calculate:

[0040] ;

[0041] Wherein, represents the count value of each distance unit, and the maximum value in the corresponding distance unit is used as the distance unit for the ground vehicle speed reference.

[0042] Preferably, updating the current frame vehicle speed includes the following steps:

[0043] S701. Determine whether the number of point clouds matching the current frame and the current vehicle speed is less than a preset threshold. If the condition is satisfied, execute step S702; otherwise, do not update the vehicle speed;

[0044] S702. Determine whether there are point clouds in the distance unit for the ground vehicle speed reference. If there are point clouds, do not update the vehicle speed; if there are no point clouds, compare the speed corresponding to the ground vehicle speed reference distance unit and the vehicle speed calculated from the point cloud of the current frame. If

[0045] ;

[0046] then it is determined that the two vehicle speeds match, and update the current frame vehicle speed to , and the updated current frame vehicle speed The expression is:

[0047] ;

[0048] If the absolute value of the difference between the speed corresponding to the ground vehicle speed reference distance unit and the vehicle speed calculated from the point cloud of the current frame is greater than the preset threshold, the vehicle speed is not updated.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] By combining the pitch angle and installation height of the radar antenna, the present invention accurately calculates the ground distance unit range, filters out possible ground echoes, matches the current vehicle speed using the velocity information of the Doppler unit, finds the distance unit with the highest matching degree, improves the accuracy of vehicle speed recognition, significantly improves the stability of vehicle speed recognition of the vehicle-mounted radar system in various environments when the number of point clouds is insufficient or in a complex environment, and reduces the dependence of the system on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Flow chart for obtaining the distance unit for ground vehicle speed reference according to the present invention ;

[0052] Figure 2 Flow chart for calculating the ground distance unit range according to the present invention

[0053] Figure 3 Flow chart for assisting in updating the vehicle speed through the speed corresponding to the distance unit for ground vehicle speed reference according to the present invention corresponding to the speed ; DETAILED DESCRIPTION OF THE INVENTION

[0054] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following describes in detail the specific implementation manners, structures, features and their effects of the present invention in conjunction with the accompanying drawings and preferred embodiments.

[0055] In order to improve the accuracy and reliability of vehicle speed recognition of the vehicle-mounted radar when the number of point clouds is insufficient or the environment is complex, this embodiment provides an optimized method for measuring vehicle speed based on the vehicle-mounted radar. In this embodiment, the pitch angle of the vehicle-mounted radar antenna is set to , the installation height of the vehicle-mounted radar is set to , the distance resolution is set to 0.5 m, the speed resolution is set to 0.1 m / s, the vehicle speed threshold is set to 10 m / s, the frame time is set to 50 ms, and the frame number threshold is set to 100 frames, is set to 1000 frames;

[0056] The method includes the following steps:

[0057] S1. Preprocess the original ADC data obtained by the vehicle-mounted radar to obtain the distance, velocity and angle data of the point cloud. The preprocessing includes:

[0058] Perform range - dimension FFT and Doppler - dimension FFT on the original ADC data;

[0059] Perform non - coherent accumulation on multi - channel data to obtain a range - Doppler map;

[0060] Perform CFAR detection on the range - Doppler map, screen out valid point clouds, and perform angle - dimension FFT on the points screened by CFAR detection to obtain angle information.

[0061] S2. Calculate the ground range cell, according to the pitch angle of the vehicle - mounted radar antenna and the vehicle - mounted radar installation height h to calculate the ground range cell ;

[0062] Calculate the closest distance when the pitch beam irradiates the ground , the expression is:

[0063] ;

[0064] Calculate the farthest distance when the pitch beam irradiates the ground , the expression is:

[0065] ;

[0066] Calculate the closest distance and the farthest distance corresponding range cells respectively through the range resolution , , the expression is:

[0067] ;

[0068] ;

[0069] wherein, and are rounded up, that is:

[0070] ;

[0071] ;

[0072] S3. Determine whether the vehicle speed of the current frame is reliable. If the vehicle speed of the current frame is reliable, go to step S4; otherwise, end the current frame and enter the next frame;

[0073] Compare the vehicle speed of the current frame and the vehicle speed of the previous frame. If it satisfies:

[0074] ;

[0075] ;

[0076] Among them, represents the preset vehicle speed threshold,

[0077] count the continuous frame number num1 that meets the conditions and compare it with the preset frame number threshold If the continuous frame number num1 is greater than the preset frame number threshold , it is determined that the current vehicle speed is reliable.

[0078] S4. Poll all the point clouds in the current frame. If there is no distance unit of the point cloud within the range of the ground distance unit , it is determined that the echo in the current distance segment comes from the ground, and the continuous frame number num2 is counted, and then step S5 is entered.

[0079] S5. Doppler unit speed matching;

[0080] S501. Screen and obtain the Doppler unit index with the largest peak in each distance unit within the range of the ground distance unit , and calculate the speed corresponding to each Doppler unit index , the expression is:

[0081] ;

[0082] Among them, represents the speed resolution, represents the number of distance units within;

[0083] S502. Judge whether the current frame speed matches the speed corresponding to each Doppler unit index . If they match, increment the counter of the corresponding distance unit by 1, otherwise the value of remains unchanged;

[0084] Calculate the absolute value of the difference between the speed corresponding to each Doppler unit index and the current frame speed , the expression is:

[0085] ;

[0086] When is satisfied, it is determined that the two speeds match.

[0087] S6. Determine the distance unit for ground vehicle speed reference ;

[0088] Judge whether num2 reaches the preset threshold , if it reaches the preset threshold, then calculate:

[0089] ;

[0090] Wherein, represents the count value of each distance unit, and take the maximum value in the corresponding distance unit as the distance unit for ground vehicle speed reference;

[0091] When the num2 threshold reaches the preset threshold of 1000 frames, the number of frames matching the vehicle speed for the 4th - 8th distance units are 300, 700, 980, 800, and 400 respectively. Therefore, in this embodiment, select the speed corresponding to the 6th distance unit for assisting vehicle speed update.

[0092] S7. Update the current frame vehicle speed to ;

[0093] S701. Judge whether the number of point clouds matching the current frame and the current vehicle speed is less than the preset threshold. If the condition is met, execute step S702; otherwise, do not update the vehicle speed;

[0094] S702. Judge whether there are point clouds in the distance unit for ground vehicle speed reference . If there are point clouds, do not update the vehicle speed; if there are no point clouds, then compare the speed corresponding to the distance unit for ground vehicle speed reference and the vehicle speed calculated from the point clouds of the current frame . If it satisfies:

[0095] ;

[0096] then judge that the two vehicle speeds match, and update the current frame vehicle speed to , and the updated current frame vehicle speed expression is:

[0097] ;

[0098] In this embodiment, the vehicle speed calculated from the point clouds of the current frame, and the speed corresponding to the distance unit for ground vehicle speed reference , the absolute value of the difference between the two speeds is , less than , then update the vehicle speed of the current frame to be:

[0099] ;

[0100] If the absolute value of the difference between the speed corresponding to the ground vehicle speed reference distance unit and the vehicle speed calculated according to the point cloud of the current frame is greater than the preset threshold, the vehicle speed will not be updated.

[0101] 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 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 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. An optimized method for measuring vehicle speed based on in-vehicle radar, characterized in that, Including the following steps: S1. Preprocess the original ADC data obtained by the vehicle-mounted radar to obtain the distance, speed, and angle data of the point cloud; S2. Calculate the ground distance unit range according to the pitch angle of the vehicle-mounted radar antenna and the installation height h of the vehicle-mounted radar to calculate the ground distance unit range ; S3. Determine the vehicle speed of the current frame Whether it is reliable. If the vehicle speed of the current frame is reliable, go to step S4; otherwise, end the current frame and enter the next frame. S4. Poll all the point clouds in the current frame. If there is no distance cell of the point cloud within the range of the ground distance cell, it is determined that the echo in the current distance segment comes from the ground, and the continuous frame number num2 is counted, and step S5 is entered; S5. Doppler unit speed matching; S501. Screen and obtain the range of the ground distance unit The Doppler cell index with the largest peak in each range cell within the range , and calculate the corresponding velocity for each Doppler cell index . The expression is as follows: The expression is: ； Among them, represents the velocity resolution, represents the number of inner range cells; S502. Determine whether the current frame speed matches the speed corresponding to each Doppler cell index If they match, increment the counter of the corresponding range cell by 1; otherwise keep the value unchanged; ​ S6. Determine the distance unit for ground vehicle speed reference ; S7. Update the current frame vehicle speed to .

2. The optimized vehicle speed measurement method based on in-vehicle radar according to claim 1, characterized in that The preprocessing includes: Perform FFT on the distance dimension and Doppler dimension of the original ADC 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 FFT on the angle dimension of the points screened by CFAR detection to obtain angle information.

3. The optimized vehicle speed measurement method based on in-vehicle radar according to claim 1, characterized in that Calculating the ground range cell includes: Calculate the closest distance when the pitch beam irradiates the ground , the expression is: ； Calculate the maximum distance when the pitch beam irradiates the ground , and the expression is: ； where h represents the installation height of the vehicle-mounted radar; By distance resolution Calculate the nearest distance respectively , the farthest distance corresponding distance unit , , the expression is: ； ； Among them, and round up the values.

4. An optimized vehicle speed measurement method based on in-vehicle radar according to claim 1, characterized in that, Compare the vehicle speed of the current frame with the vehicle speed of the previous frame , if the following condition is met: ； ； Among them, represents a preset vehicle speed threshold value. Count the continuous frame number num1 that meets the condition and compare it with the preset frame number threshold If the continuous frame number num1 is greater than the preset frame number threshold then it is determined that the current vehicle speed is reliable.

5. The optimized vehicle speed measurement method based on in-vehicle radar according to claim 1, wherein Calculate the Doppler cell index for each one separately The corresponding velocity The absolute value of the difference from the velocity of the current frame , the expression is: ； When is satisfied, it is determined that the two speeds match.

6. The optimized vehicle speed measurement method based on in-vehicle radar according to claim 1, characterized in that, Distance unit for obtaining ground vehicle speed reference The steps include: Determine whether the num2 reaches a preset threshold , if it reaches the preset threshold, then calculate: ； Among them, represents the count value of each distance unit, and the maximum value in the corresponding distance unit is used as the distance unit for ground vehicle speed reference.

7. An optimized method for measuring vehicle speed based on in-vehicle radar according to claim 1, characterized in that, Updating the vehicle speed of the current frame includes the following steps: S701. Determine whether the number of point clouds matching the current vehicle speed in the current frame is less than a preset threshold. If the condition is met, execute step S702; otherwise, do not update the vehicle speed; S702. Determine the distance unit for ground vehicle speed reference Check if there is point cloud. If there is, do not update the vehicle speed. If there is no point cloud, compare the speed corresponding to the ground vehicle speed reference distance unit with the vehicle speed calculated from the point cloud in the current frame . If the following condition is met: ； Then it is determined that the vehicle speeds match, and the vehicle speed of the current frame is updated is , and the updated vehicle speed of the current frame The expression is: ； If the ground vehicle speed reference distance unit corresponding speed and the vehicle speed calculated from the point cloud of the current frame The absolute value of the difference is greater than the preset threshold, then the vehicle speed is not updated.

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