Method and system for detecting low speed closing targets while moving

Abstract

The application relates to a detection method and system for low-speed approaching targets during movement, a detection method for low-speed approaching targets during movement, which comprises the following steps: emitting medium-frequency signals to the rear of a vehicle body by a radar and receiving the reflected medium-frequency signals; accumulating data and obtaining a two-dimensional virtual part speed amplitude spectrum and a two-dimensional virtual part speed phase spectrum; if the vehicle body is in a high-speed movement state and there is a real part speed amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part speed amplitude spectrum, it is determined that there is a suspicious low-speed approaching target; according to the coordinate set A, the real part speed phase, the virtual part speed amplitude and the virtual part speed phase of each suspicious low-speed approaching target are extracted; if the virtual part speed amplitude of the suspicious low-speed approaching target is greater than a second preset threshold, the amplitude is close and the phase difference is between -110 DEG and -90 DEG, it is determined that there is a low-speed approaching target.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radar target detection, and particularly to a method and system for detecting a low-speed approaching target during movement. BACKGROUND

[0002] With the rapid development of urbanization, people's work rhythm and lifestyle have changed a lot. In order to alleviate traffic pressure, two-wheeled vehicles have become one of the main means of transportation in urban traffic. In the complex traffic situation, it is particularly important to improve the safety of two-wheeled vehicle riders. In the process of using two-wheeled vehicles, if the distance between the target and the two-wheeled vehicle gradually approaches, the target is a low-speed approaching target. The low-speed approaching target poses a great safety hazard to two-wheeled vehicles. If it can be identified during riding, the safety of riders will be greatly improved.

[0003] The prior art such as Chinese application "Vehicle and target detection method and device of vehicle-mounted radar" (CN201910806353.3) can judge whether there is an approaching target, but the detection error of the low-speed approaching target behind the two-wheeled vehicle by radar is large at present, and there is room for improvement.

[0004] In view of the above problems existing in the prior art, the present application aims to design a method and system for detecting a low-speed approaching target during movement. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application aims to design a method and system for detecting a low-speed approaching target during movement.

[0006] The technical scheme of the present application is as follows:

[0007] A method for detecting a low-speed approaching target during movement, comprising the following steps:

[0008] The radar emits a medium frequency signal towards the rear of the vehicle body and receives the reflected medium frequency signal;

[0009] The reflected medium frequency signal is subjected to M-point FFT transformation to obtain a one-dimensional real part sequence and a one-dimensional imaginary part sequence;

[0010] The one-dimensional real part sequences corresponding to N medium frequency signals and the one-dimensional imaginary part sequences are accumulated, the N one-dimensional real part sequences are arranged in rows to obtain a two-dimensional real part sequence, the N one-dimensional imaginary part sequences are arranged in rows to obtain a two-dimensional imaginary part sequence, and the two-dimensional real part sequence and the two-dimensional imaginary part sequence are updated in real time;

[0011] performing N-point FFT transformation on the two-dimensional real part sequence by column to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, performing N-point FFT transformation on the two-dimensional imaginary part sequence by column to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum;

[0012] If the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, it is determined that there is a suspicious low-speed approaching target, and a coordinate set A corresponding to the suspicious low-speed approaching target in the two-dimensional real part velocity amplitude spectrum is recorded.

[0013] According to the coordinate set A, the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase of each suspicious low-speed approaching target are extracted from the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum, and the two-dimensional imaginary part velocity phase spectrum, and the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase corresponding to the same coordinate are defined as an element pair.

[0014] If the suspicious low-speed approaching target has a horizontal coordinate of 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, it is determined that there is a relatively stationary target.

[0015] If the suspicious low-speed approaching target has a horizontal coordinate greater than 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, and the phase difference between the real part velocity phase and the imaginary part velocity phase in the element pair of the suspicious low-speed approaching target is between -110° and -90°, it is determined that there is a low-speed approaching target. Further, the radar emits a medium frequency signal towards the rear of the vehicle body and receives the reflected medium frequency signal, including:

[0016] The radar emits the medium frequency signal multiple times, and the medium frequency signal contains at least several chirp signals, and the reflected medium frequency signal is obtained in real time as a data unit of chirp.

[0017] Further, wherein is the maximum detection distance of the radar, is the distance resolution of the radar.

[0018] Further, wherein is the maximum detection velocity of the radar, is the velocity resolution of the radar.

[0019] Further, the real-time updating of the two-dimensional real part sequence and the two-dimensional imaginary part sequence comprises:

[0020] The two-dimensional real part sequence and the two-dimensional imaginary part sequence are updated in real time by a sliding window method, wherein the size of the sliding window is N.

[0021] Further, if the vehicle body is in a high-speed motion state, it comprises:

[0022] obtaining the motion speed v of the vehicle body and the speed resolution of the radar if , it is determined that the vehicle body is in a high-speed motion state.

[0023] Further, the imaginary part speed amplitude and the real part speed amplitude in the suspicious low-speed approaching target element pair are close, which comprises:

[0024] If the amplitude value of the imaginary part speed amplitude and the real part speed amplitude in the suspicious low-speed approaching target element pair is between 0.8 and 1.2, it is determined that the imaginary part speed amplitude and the real part speed amplitude are close.

[0025] Further, the first preset value and the second preset value are obtained by statistical results to distinguish targets and noises. Further, the reflected intermediate frequency signal is subjected to M-point FFT transformation, which comprises:

[0026] The reflected intermediate frequency signal is subjected to M-point FFT transformation after being subjected to a Hamming window.

[0027] A detection system for low-speed approaching targets during movement is used to implement the detection method for low-speed approaching targets during movement, which comprises:

[0028] A radar, which is a 24GHz transmitting-receiving frequency continuous wave radar, is installed on the vehicle body and faces the rear of the vehicle body.

[0029] A transmitting-receiving module is used to transmit intermediate frequency signals to the rear of the vehicle body by the radar and receive reflected intermediate frequency signals.

[0030] An M-point FFT transformation module is used to perform M-point FFT transformation on the reflected intermediate frequency signals to obtain one-dimensional real part sequences and one-dimensional imaginary part sequences.

[0031] A data storage module is used to accumulate one-dimensional real part sequences and one-dimensional imaginary part sequences corresponding to N intermediate frequency signals, arrange N one-dimensional real part sequences in rows to obtain a two-dimensional real part sequence, arrange N one-dimensional imaginary part sequences in rows to obtain a two-dimensional imaginary part sequence, and update the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time.

[0032] An N-point FFT transform module is configured to perform N-point FFT transform on the two-dimensional real part sequence column by column to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, and perform N-point FFT transform on the two-dimensional imaginary part sequence column by column to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum;

[0033] A suspicious low-speed closing target judgment module is configured to determine that there is a suspicious low-speed closing target if the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, and record a coordinate set A corresponding to the suspicious low-speed closing target in the two-dimensional real part velocity amplitude spectrum;

[0034] A target judgment module is configured to extract real part velocity phase, imaginary part velocity amplitude and imaginary part velocity phase of each suspicious low-speed closing target from the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum and the two-dimensional imaginary part velocity phase spectrum according to the coordinate set A, and define the real part velocity phase, the imaginary part velocity amplitude and the imaginary part velocity phase corresponding to the same coordinate as an element pair.

[0035] If the suspicious low-speed closing target has a horizontal coordinate of 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, it is determined that there is a relatively stationary target.

[0036] If the suspicious low-speed closing target has a horizontal coordinate greater than 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, and the phase difference between the real part velocity phase and the imaginary part velocity phase in the element pair of the suspicious low-speed closing target is between -110° and -90°, it is determined that there is a low-speed closing target.

[0037] The present application uses a frequency-modulated continuous wave radar to detect a target that is closing at a low speed relative to a two-wheeled intelligent vehicle when the vehicle body itself is moving at a high speed, and obtain an approximate radial distance and an approximate radial velocity of the target relative to the two-wheeled intelligent vehicle. The present application improves the accuracy of detecting a low-speed closing target for a two-wheeled intelligent vehicle moving at a high speed, and has the advantages of simple method, easy implementation, low cost and applicability to various application environments.

[0038] The present application provides a radar to obtain the reflected intermediate frequency signal, and carries out corresponding data transformation, data extraction, data judgment and other steps, whether there is a low-speed approaching target can be judged. Through the real part velocity amplitude set A greater than the first preset threshold, it is determined that there is a suspicious low-speed approaching target; and the real part velocity phase, the imaginary part velocity amplitude and the imaginary part velocity phase of each suspicious low-speed approaching target are extracted in the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum and the two-dimensional imaginary part velocity phase spectrum, it is judged that the imaginary part velocity amplitude of the suspicious low-speed approaching target is greater than the second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, and the phase difference between the real part velocity phase and the imaginary part velocity phase in the element pair of the suspicious low-speed approaching target is between-110° and-90°, which meets the condition, so that the judgment can be accurately judged, and the accuracy of the judgment is improved.

[0039] It should be understood that the above summary and the following detailed description of the present application are exemplary and explanatory, and are intended to provide further explanation of the present application as claimed. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The flowchart of the present application.

[0041] Figure 2 The logic diagram of the present application.

[0042] Figure 3 The result diagram of each step of the present application. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of those skilled in the art, the present application will be further described in detail in combination with the drawings: it should be understood that, in the present embodiment, the steps mentioned, except for the order specified, can be adjusted according to the actual needs, even can be executed simultaneously or partially simultaneously.

[0044] REFERENCE Figures 1-2 A method for detecting low-speed approaching target in moving process, comprising the following steps:

[0045] S1, transmitting intermediate frequency signal to the rear of the vehicle body by radar and receiving the reflected intermediate frequency signal;

[0046] In the embodiment, the radar has the function of receiving and transmitting intermediate frequency signals. By transmitting intermediate frequency signals to the rear of the vehicle body, it can be detected whether there is a target approaching the vehicle body behind the vehicle body. Detecting low-speed and close-to-vehicle bodies can effectively remind the vehicle owner to pay attention to the target and make early avoidance actions. After the radar transmits intermediate frequency signals, the intermediate frequency signals are reflected back by the target during propagation, and thus are received by the radar. Specifically, a 24GHz transmit-receive frequency-modulated continuous wave radar is installed on the seat support of the two-wheeled vehicle and faces the rear, and the axis of the radar plane is above the wheel, so that the intermediate frequency signals of the radar are obtained in real time with chirp as a data unit. The axis of the radar plane above the wheel means that the detection plane of the radar should be behind the vehicle body, so as to avoid the radar facing the wheel and thus detecting the rear and lower part of the vehicle body, thereby improving the detection range of the radar.

[0047] The vehicle body of the embodiment can be a two-wheeled vehicle, such as an electric bicycle, or other vehicle bodies, which are not limited here.

[0048] S2, M-point FFT transformation is performed on the reflected intermediate frequency signals to obtain a one-dimensional real part sequence and a one-dimensional imaginary part sequence;

[0049] Further, wherein is the maximum detection distance of the radar, is the distance resolution of the radar.

[0050] In this step, the intermediate frequency signal can be converted from time domain to frequency domain by FFT transformation to obtain the frequency spectrum corresponding to the intermediate frequency signal. The FFT transformation is a prior art, and its principle is not specifically expanded here. M is determined by the maximum detection distance and the distance resolution The number of M can be effectively determined by the above to confirm the number of FFT transformation points.

[0051] S3, accumulate N one-dimensional real part sequences and N one-dimensional imaginary part sequences corresponding to the intermediate frequency signals, arrange N one-dimensional real part sequences in rows to obtain a two-dimensional real part sequence, arrange N one-dimensional imaginary part sequences in rows to obtain a two-dimensional imaginary part sequence, and update the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time;

[0052] A one-dimensional real part sequence and a one-dimensional imaginary part sequence corresponding to the intermediate frequency signal can be obtained through the step S2, and a plurality of one-dimensional real part sequences and one-dimensional imaginary part sequences can be obtained by repeating the step S2, and the one-dimensional real part sequences are stored in rows to form a two-dimensional real part sequence. For example, the first one-dimensional real part sequence is arranged in the first row, the second one-dimensional real part sequence is arranged in the second row, the third one-dimensional real part sequence is arranged in the third row, and so on, so that a two-dimensional real part sequence is obtained, and the real part values of the same frequency band are located in the same column, and the real part values of the same intermediate frequency signal are located in the same row. The method of forming a two-dimensional imaginary part sequence is the same.

[0053] In this embodiment, the one-dimensional FFT may not be accurate in the speed direction, so the complex transformation is not directly performed. The real part velocity spectrum and the imaginary part velocity spectrum are obtained by performing FFT respectively.

[0054] S4, performing N-point FFT transformation on the two-dimensional real part sequence to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, and performing N-point FFT transformation on the two-dimensional imaginary part sequence to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum;

[0055] Further, , wherein is the maximum detection speed of the radar, is the velocity resolution of the radar.

[0056] In the step S3, the two-dimensional real part sequence and the two-dimensional imaginary part sequence are obtained, and in this step, the two-dimensional real part sequence and the two-dimensional imaginary part sequence are subjected to FFT transformation to further obtain a two-dimensional real part velocity amplitude spectrum, a two-dimensional real part velocity phase spectrum, a two-dimensional imaginary part velocity amplitude spectrum, and a two-dimensional imaginary part velocity phase spectrum. The sequence length N is determined by the maximum detection speed of the target relative to the two-wheeled vehicle and the velocity resolution , specifically, .

[0057] Through the steps S1-S4, the data accumulation required for judging the low-speed approaching target is completed. The subsequent steps will use the data obtained in the steps S1-S4 to make specific judgments.

[0058] S5, if the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, it is determined that there is a suspicious low-speed approaching target, and a coordinate set A corresponding to the suspicious low-speed approaching target in the two-dimensional real part velocity amplitude spectrum is recorded.

[0059] In this step, according to the motion speed of the two-wheeled vehicle where the radar is located, the velocity resolution of the radar , the two-dimensional real part velocity amplitude spectrum, the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum, and the two-dimensional imaginary part velocity phase spectrum determine whether there is a low-speed closing target, and determine the approximate radial distance and approximate radial velocity of the low-speed closing target and the two-wheeled vehicle. Specifically, first, in the first three rows of the two-dimensional real part velocity amplitude spectrum, whether there is a real part velocity amplitude greater than a first preset threshold is found, and a real part velocity amplitude set A is formed. As mentioned above, the real part values of the same frequency band in the two-dimensional real part sequence are located in the same column, and the first three rows are searched because the first three rows respectively represent 0 , velocity , and velocity , for example, the velocity resolution is 5 km / h, then the first three rows respectively represent 0 km / h, 5 km / h, and 10 km / h, that is, the first three rows of the two-dimensional real part sequence represent the spectrum of the corresponding relative velocity of the low-speed closing target.

[0060] The first preset threshold greater than the first preset threshold indicates that there is a suspicious low-speed closing target at present, which may be a misjudgment, or a relatively static target or a low-speed closing target, which needs to be judged through subsequent steps. Then, the first three rows of the two-dimensional real part velocity amplitude spectrum are traversed, and the coordinates of the amplitudes greater than the first preset threshold, that is, the coordinates of the suspicious low-speed closing target in the two-dimensional real part velocity amplitude spectrum are extracted, and then the candidate low-speed closing target set is determined by the corresponding row and column pairs.

[0061] This step is only performed when the vehicle body is moving at a high speed, because if the vehicle body is moving slowly, the movement of the surrounding objects has little effect on its safety, and is not considered in this application.

[0062] S6, according to the coordinate set A, the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase of each suspicious low-speed closing target are extracted from the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum, and the two-dimensional imaginary part velocity phase spectrum, and the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase corresponding to the same coordinates are defined as element pairs.

[0063] In step S5, for example, the coordinates (2,10) are extracted. This step extracts the corresponding values ​​from the two-dimensional real velocity phase spectrum, the two-dimensional imaginary velocity amplitude spectrum, and the two-dimensional imaginary velocity phase spectrum of the suspected low-speed approaching target at coordinates (2,10), obtaining the real velocity phase, imaginary velocity amplitude, and imaginary velocity phase corresponding to coordinate (2,10). Then, the real velocity phase, imaginary velocity amplitude, and imaginary velocity phase corresponding to coordinates (2,10) are grouped together to form element pairs. That is, each element pair consists of values ​​corresponding to the same coordinates, and there can be multiple element pairs.

[0064] The next step is the existence of a target approaching at a low speed, as described in this application.

[0065] If the horizontal coordinate of the suspected low-speed approaching target is 0 and the imaginary velocity amplitude is greater than the second preset threshold, and the imaginary velocity amplitude and the real velocity amplitude are close in the element pair of the suspected low-speed approaching target, it is determined to be a relatively stationary target.

[0066] If the abscissa of the suspected low-speed approaching target is greater than 0 and the imaginary velocity amplitude is greater than a second preset threshold, and the imaginary velocity amplitude and the real velocity amplitude in the element pair of the suspected low-speed approaching target are close, and the phase difference between the real velocity phase and the imaginary velocity phase in the element pair of the suspected low-speed approaching target is between -110° and -90°, then it is determined that a low-speed approaching target exists. Specifically, the set is traversed on the two-dimensional real velocity amplitude spectrum, the two-dimensional real velocity phase spectrum, the two-dimensional imaginary velocity amplitude spectrum, and the two-dimensional imaginary velocity phase spectrum. For each pair of elements in the set, if the velocity is 0 and both conditions a and b are satisfied, then there exists a target that is stationary relative to the two-wheeled vehicle. Update the set of targets approaching at low speeds. If the speed is greater than 0 and all three conditions a, b, and c are met simultaneously, then the existence of a low-speed approaching target is confirmed, and the set of low-speed approaching targets is updated. And the corresponding approximate radial velocity and approximate radial distance of the target relative to the two-wheeled vehicle are respectively and .

[0067] a. The two-dimensional imaginary part velocity amplitude spectrum at point The amplitude value at that location exceeds the preset second threshold.

[0068] b. The two-dimensional real part velocity amplitude spectrum and the two-dimensional imaginary part velocity amplitude spectrum at point... The ratio of the amplitude values ​​at that point is between 0.8 and 1.2;

[0069] c. The two-dimensional real part velocity phase spectrum and the two-dimensional imaginary part velocity phase spectrum at point... The phase difference of the two signals is between -110 degrees and -90 degrees.

[0070] In the subsequent of the step, the function of alarm reminder can be added. When the low-speed approaching target is detected, the sound and light alarm system sends corresponding alarm to remind the owner to pay attention to the rear.

[0071] Further, the transmitting and receiving of the intermediate frequency signal by the radar towards the rear of the vehicle body comprises:

[0072] The intermediate frequency signal is transmitted by the radar for multiple times, and the intermediate frequency signal contains at least a plurality of chirp signals. The reflected intermediate frequency signal is obtained in real time by taking chirp as a data unit.

[0073] The linear frequency modulation signal is also called chirp signal. Because the frequency spectrum bandwidth falls within the audible range, it sounds like a bird sound, so it is also called chirp spread spectrum (CSS) technology. LFM technology is widely used in radar and sonar technology. For example, in radar positioning technology, it can increase the radio frequency pulse width, improve the average transmission power, increase the communication distance, and maintain sufficient signal spectrum width while not reducing the distance resolution of the radar.

[0074] Further, the real-time updating of the two-dimensional real part sequence and the two-dimensional imaginary part sequence comprises:

[0075] The two-dimensional real part sequence and the two-dimensional imaginary part sequence are updated in real time by a sliding window method, and the size of the sliding window is N.

[0076] The sliding window algorithm is a prior art. Through the sliding window algorithm, the future data of the next moment can be predicted and extracted from a plurality of historical data. At this time, in order to make full use of all data, a sliding window operation should be performed on the original data set.

[0077] Further, if the vehicle body is in a high-speed motion state, it comprises:

[0078] The speed v of the vehicle body and the speed resolution of the radar are obtained. If , it is determined that the vehicle body is in a high-speed motion state.

[0079] The speed resolution of the radar is used to determine whether the vehicle body is in a high-speed motion state. If , it is determined that the vehicle body is in a high-speed motion state. For example, if the speed resolution of the radar is 5 km / h, it is determined that the vehicle body is in a high-speed motion state when the speed v is greater than or equal to 30 km / h. The speed v of the vehicle body can be obtained by a speed detection module provided on the vehicle body.

[0080] Further, the suspicious low-speed closing target element pair in which the imaginary part velocity amplitude and the real part velocity amplitude are close to each other includes:

[0081] If the amplitude value of the imaginary part velocity amplitude and the real part velocity amplitude in the suspicious low-speed closing target element pair is between 0.8 and 1.2, it is determined that the imaginary part velocity amplitude and the real part velocity amplitude are close to each other.

[0082] The first preset threshold and the second preset threshold are obtained by statistical results, and are used to distinguish the target and the noise. In the embodiment, the first preset threshold and the second preset threshold are both set to 600. In other embodiments, when the first preset threshold and the second preset threshold can be used to distinguish the target and the noise, the first preset threshold and the second preset threshold can be used. Further, the M-point FFT transformation of the reflected intermediate frequency signal includes:

[0083] The M-point FFT transformation of the reflected intermediate frequency signal after the Hamming window is added.

[0084] Further, a low-speed closing target detection system in a moving process is provided, which is used to implement the low-speed closing target detection method in the moving process, and includes:

[0085] A radar, which is a 24GHz transmitting-receiving frequency-modulated continuous wave radar, is installed on the vehicle body and faces the rear of the vehicle body.

[0086] A transmitting-receiving module is configured to transmit an intermediate frequency signal to the rear of the vehicle body by the radar and receive a reflected intermediate frequency signal.

[0087] An M-point FFT transformation module is configured to perform M-point FFT transformation on the reflected intermediate frequency signal to obtain a one-dimensional real part sequence and a one-dimensional imaginary part sequence.

[0088] A data storage module is configured to accumulate one-dimensional real part sequences and one-dimensional imaginary part sequences corresponding to N intermediate frequency signals, arrange N one-dimensional real part sequences in rows to obtain a two-dimensional real part sequence, arrange N one-dimensional imaginary part sequences in rows to obtain a two-dimensional imaginary part sequence, and update the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time.

[0089] An N-point FFT transformation module is configured to perform N-point FFT transformation on the two-dimensional real part sequence in columns to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, and perform N-point FFT transformation on the two-dimensional imaginary part sequence in columns to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum.

[0090] A suspicious low-speed closing target judgment module is configured to determine that there is a suspicious low-speed closing target if the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, and record a coordinate set A corresponding to the suspicious low-speed closing target in the two-dimensional real part velocity amplitude spectrum;

[0091] A target judgment module is configured to extract a real part velocity phase, a virtual part velocity amplitude and a virtual part velocity phase of each suspicious low-speed closing target from the two-dimensional real part velocity phase spectrum, the two-dimensional virtual part velocity amplitude spectrum and the two-dimensional virtual part velocity phase spectrum according to the coordinate set A, and define the real part velocity phase, the virtual part velocity amplitude and the virtual part velocity phase corresponding to the same coordinate as an element pair.

[0092] If the abscissa of the suspicious low-speed closing target is 0 and the virtual part velocity amplitude is greater than a second preset threshold, and the virtual part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, it is determined that there is a relatively static target.

[0093] If the abscissa of the suspicious low-speed closing target is greater than 0 and the virtual part velocity amplitude is greater than a second preset threshold, and the virtual part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, and the phase difference between the real part velocity phase and the virtual part velocity phase in the element pair of the suspicious low-speed closing target is between -110° and -90°, it is determined that there is a low-speed closing target. The working principle of a detection system for a low-speed closing target in a moving process is the same as a detection method for a low-speed closing target in a moving process, and will not be described here.

[0094] Embodiment one

[0095] S1, a two-wheeled motorcycle is used as a vehicle body, a 24GHz transmitting-receiving frequency-modulated continuous wave radar is installed on the seat support of the two-wheeled motorcycle and faces the rear, the axis of the radar plane is above the wheel, and the intermediate frequency signal of the radar is acquired in real time with chirp as a data unit.

[0096] S2, the maximum detection distance of the radar on the motorcycle is set , the distance resolution of the radar detection , the length of the Hamming window is determined according to the above detection requirements . After the 64-point Hamming window is added to the intermediate frequency signal, 64-point FFT is performed to obtain a one-dimensional real part sequence and a one-dimensional virtual part sequence of the distance spectrum.

[0097] S3, the maximum closing speed of the target relative to the motorcycle detected by the motorcycle is set , the speed resolution of the radar detection According to the above detection requirements, the chirp accumulation length is determined The one-dimensional real part sequence and the one-dimensional imaginary part sequence corresponding to the intermediate frequency signal of 64 chirps are stored in rows to form a two-dimensional real part sequence and a two-dimensional imaginary part sequence, and the two-dimensional real part sequence and the two-dimensional imaginary part sequence are updated by a sliding window method.

[0098] S4, 64-point FFT is performed on the two-dimensional real part sequence in the column direction to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum. 64-point FFT is performed on the two-dimensional imaginary part sequence in the column direction to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum.

[0099] S5, when the motorcycle's own motion speed is , the calculation , the two-wheeled vehicle is in a low-speed motion state, and target judgment of relative low-speed approach to the target is not performed.

[0100] When the motorcycle's own motion speed is , the calculation , the two-wheeled vehicle is in a high-speed motion state, and further target judgment of relative low-speed approach to the target is performed. The amplitudes of the first three speeds of the two-dimensional real part velocity amplitude spectrum are traversed in the column direction to determine a set of row-column pairs , for example .

[0101] S6, for the first row-column pair in the set , it is judged whether the amplitude value of the two-dimensional imaginary part velocity amplitude spectrum at point exceeds a preset second threshold value, and whether the ratio of the amplitude values of the two-dimensional real part velocity amplitude spectrum and the two-dimensional imaginary part velocity amplitude spectrum at point is between 0.8 and 1.2, if both conditions are met, the set of row-column pairs of the detected target is updated .

[0102] For the second row-column pair in the set , it is judged whether the amplitude value of the two-dimensional imaginary part velocity amplitude spectrum at point exceeds a preset second threshold value, and whether the ratio of the amplitude values of the two-dimensional real part velocity amplitude spectrum and the two-dimensional imaginary part velocity amplitude spectrum at point is between 0.8 and 1.2, and whether the phase difference of the two-dimensional real part velocity phase spectrum and the two-dimensional imaginary part velocity phase spectrum at point is between -110 degrees and -90 degrees, if the three conditions cannot be met at the same time, the set of row-column pairs of the detected target is kept .

[0103] For the third row-column pair in the set , it is determined whether the amplitude value of the two-dimensional imaginary part velocity amplitude spectrum at point exceeds a preset second threshold value, and whether the ratio of the amplitude values of the two-dimensional real part velocity amplitude spectrum and the two-dimensional imaginary part velocity amplitude spectrum at point is between 0.8 and 1.2, and whether the phase difference of the two-dimensional real part velocity phase spectrum and the two-dimensional imaginary part velocity phase spectrum at point is between -110 degrees and -90 degrees, if the three conditions are met simultaneously, the row-column pair set of the detection target is updated .

[0104] According to the detection target row-column pair set , it is determined that there are two low-speed approaching targets, and one of the targets is approximately at the same speed as the motorcycle and travels approximately 30 m behind the motorcycle, and the other target is approximately 65 m behind the motorcycle and approaches the motorcycle at a speed of 5 km / h.

[0105] Those skilled in the art will understand that embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0106] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce an apparatus that implements the functions specified in the flow Figure 1 flow or multiple flows and / or blocks Figure 1 of the flowcharts and / or block diagrams.

[0107] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction apparatus, which implements the functions specified in the flow Figure 1 flow or multiple flows and / or blocksFigure 1 the function specified in the one or more blocks.

[0108] These computer program instructions can also be loaded into computer or other programmable data processing devices to cause a series of operational steps to be performed on the computer or other programmable devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable devices provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 the flowchart block or blocks Figure 1 the function specified in the one or more blocks.

[0109] It is noted that in the claims the word "comprising" does not exclude not having other parts than those specified in the claim. The word "a" or "an" preceding a claim category does not exclude a plurality of those categories. The application can be implemented by means of hardware comprising several distinct elements, and by means of a programmed computer. In the claims, the term "comprising" does not exclude other elements being added to the claimed elements. The word "first", "second", "third", etc. does not imply any order. The terms "first", "second", "third", etc. are to be interpreted according to the context in which they are used.

[0110] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to cover all such modifications and variations as fall within the true spirit and scope of the application.

[0111] It is clear that the application can be carried out in various ways and the disclosure can be implemented in several embodiments without deviating from its spirit or essential characteristics. It is therefore demanded that all such modifications and variations that fall within the scope of the application as defined in the claims and their equivalents be considered as part of the application.

[0112] In the description of the specification, the description using the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that a specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Descriptive expressions of the above terms in the specification should not be understood as necessarily referring to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction with each other.

Claims

1. A method for detecting a low speed closing target during a moving process, characterized in that: The method comprises the following steps: emit intermediate frequency signals towards the back of the vehicle body through radar and receive the reflected intermediate frequency signals; perform M-point FFT transformation on the reflected intermediate frequency signals to obtain a one-dimensional real part sequence and a one-dimensional imaginary part sequence; accumulate the one-dimensional real part sequences and the one-dimensional imaginary part sequences corresponding to N intermediate frequency signals, arrange the N one-dimensional real part sequences in rows to obtain a two-dimensional real part sequence, arrange the N one-dimensional imaginary part sequences in rows to obtain a two-dimensional imaginary part sequence, and update the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time; perform N-point FFT transformation on the two-dimensional real part sequence column by column to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, and perform N-point FFT transformation on the two-dimensional imaginary part sequence column by column to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum; if the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, it is determined that there is a suspicious low-speed approaching target, and a coordinate set A corresponding to the suspicious low-speed approaching target in the two-dimensional real part velocity amplitude spectrum is recorded; extract the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase of each suspicious low-speed approaching target from the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum, and the two-dimensional imaginary part velocity phase spectrum according to the coordinate set A, and define the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase corresponding to the same coordinates as elements of a pair; if the suspicious low-speed approaching target has a horizontal coordinate of 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, it is determined that there is a relatively stationary target; if the suspicious low-speed approaching target has a horizontal coordinate greater than 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, and the phase difference between the real part velocity phase and the imaginary part velocity phase in the element pair of the suspicious low-speed approaching target is between -110° and -90°, it is determined that there is a low-speed approaching target.

2. The method of claim 1, wherein the method is used for detecting a low-speed closing target in a moving process. The method of emitting intermediate frequency signals towards the back of the vehicle body through radar and receiving the reflected intermediate frequency signals comprises: emitting the intermediate frequency signals multiple times through radar, wherein the intermediate frequency signals at least contain a plurality of chirp signals, and the reflected intermediate frequency signals are obtained in real time in units of chirp.

3. The method of claim 1, wherein the method is used for detecting a low-speed closing target in a moving process. wherein is the maximum detection range of the radar, is the range resolution of the radar.

4. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. wherein Vmax is the maximum detection speed of the radar, Vres is the speed resolution of the radar.

5. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. The method of updating the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time comprises: updating the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time through a sliding window method, wherein the size of the sliding window is N.

6. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. If the vehicle body is in a high-speed motion state, the method comprises: acquiring a self-motion speed v of the vehicle body and a speed resolution of the radar , if then determining that the vehicle body is in a high-speed motion state.

7. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. if the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target are close, the method comprises: if the amplitude value ratio of the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed approaching target is between 0.8 and 1.2, it is determined that the imaginary part velocity amplitude and the real part velocity amplitude are close.

8. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. The first preset threshold and the second preset threshold are obtained by statistical results, and are used to distinguish targets and noises.

9. The method of claim 1, wherein the method is used for detecting a low-speed closing target during a moving process. The M-point FFT transformation of the reflected intermediate frequency signal comprises: The M-point FFT transformation of the reflected intermediate frequency signal after the Hamming windowing.

10. A system for detecting a low speed closing target during a moving process, characterized in that: The method for detecting a low-speed closing target during a moving process comprises: a radar, which is a 24 GHz transmitting-receiving frequency-modulated continuous wave radar, is installed on the vehicle body and faces the rear of the vehicle body; a transmitting-receiving module is configured to transmit an intermediate frequency signal to the rear of the vehicle body by the radar and receive a reflected intermediate frequency signal; an M-point FFT transformation module is configured to perform M-point FFT transformation on the reflected intermediate frequency signal to obtain a one-dimensional real part sequence and a one-dimensional imaginary part sequence; a data storage module is configured to accumulate one-dimensional real part sequences and one-dimensional imaginary part sequences corresponding to N intermediate frequency signals, arrange N one-dimensional real part sequences in rows to obtain a two-dimensional real part sequence, arrange N one-dimensional imaginary part sequences in rows to obtain a two-dimensional imaginary part sequence, and update the two-dimensional real part sequence and the two-dimensional imaginary part sequence in real time; an N-point FFT transformation module is configured to perform N-point FFT transformation on the two-dimensional real part sequence in columns to obtain a two-dimensional real part velocity amplitude spectrum and a two-dimensional real part velocity phase spectrum, and perform N-point FFT transformation on the two-dimensional imaginary part sequence in columns to obtain a two-dimensional imaginary part velocity amplitude spectrum and a two-dimensional imaginary part velocity phase spectrum; a suspicious low-speed closing target judgment module is configured to determine that there is a suspicious low-speed closing target if the vehicle body is in a high-speed motion state and there is a real part velocity amplitude set A greater than a first preset threshold in the first three rows of the two-dimensional real part velocity amplitude spectrum, and record a coordinate set A corresponding to the suspicious low-speed closing target in the two-dimensional real part velocity amplitude spectrum; a target judgment module is configured to extract a real part velocity phase, an imaginary part velocity amplitude, and an imaginary part velocity phase of each suspicious low-speed closing target according to the coordinate set A in the two-dimensional real part velocity phase spectrum, the two-dimensional imaginary part velocity amplitude spectrum, and the two-dimensional imaginary part velocity phase spectrum, and define the real part velocity phase, the imaginary part velocity amplitude, and the imaginary part velocity phase corresponding to the same coordinate as an element pair; if the suspicious low-speed closing target has a horizontal coordinate of 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, it is determined that the target is relatively static; if the suspicious low-speed closing target has a horizontal coordinate greater than 0 and an imaginary part velocity amplitude greater than a second preset threshold, and the imaginary part velocity amplitude and the real part velocity amplitude in the element pair of the suspicious low-speed closing target are close to each other, and the phase difference between the real part velocity phase and the imaginary part velocity phase in the element pair of the suspicious low-speed closing target is between -110° and -90°, it is determined that there is a low-speed closing target.

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