Foreign object coverage detection method based on millimeter wave radar parking detection

Abstract

The present invention discloses a foreign object coverage detection method based on millimeter wave radar parking detection, which is used to determine the parking state and whether the parking detection module is covered by foreign objects, including step S1: the parking detection module samples the acquired detection signal to obtain the sampling signal and pre-processes the sampling signal; step S2: the pre-processed sampling signal is subjected to spectrum calculation processing to obtain the spectrum curve of the sampling signal. The present invention discloses a foreign object coverage detection method based on millimeter wave radar parking detection, which divides the spectrum of the detection signal into two frequency bands, medium and low, under the condition of limited working bandwidth, and judges whether the state above the parking detection module is a car, no car or covered by foreign objects through comprehensive analysis of the signal characteristics in the above two frequency bands, and has the advantages of sensitive detection, high precision and easy use.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter wave radar parking detection, and in particular relates to a foreign object coverage detection method based on millimeter wave radar parking detection. Background Art

[0002] Millimeter-wave radar can be used in embedded parking detection modules to detect parked vehicles above the module. Millimeter-wave radar modules are highly integrated and compact, making them easy to integrate into parking detection modules. Electromagnetic waves can penetrate the plastic casing of the parking detection module to detect objects above it. Common millimeter-wave radar parking detection modules can accurately determine whether a vehicle is parked above the module. These parking detection modules are often used in outdoor environments. The surface of the parking detection module may be covered by objects that shield electromagnetic waves, such as standing water, metal foreign objects, and greenery. In this case, the millimeter-wave radar will be unable to determine the parking status above the module, resulting in a detection failure. Therefore, millimeter-wave radars should have a coverage detection function. If the parking detection module is covered by objects that shield electromagnetic waves, such as standing water, metal foreign objects, and greenery, the radar should report the foreign object coverage information, informing the host computer of the radar detection failure, to avoid misjudgments.

[0003] The common detection method used by millimeter-wave radars in current parking detection modules is FMCW ranging. This method detects the presence of a target above the module and the distance to the target (i.e., the vehicle chassis) to determine whether a vehicle is parked above. The distance between the vehicle chassis and the radar is typically tens to several dozen centimeters, and the distance between covered foreign objects such as stagnant water and the radar is typically only a few millimeters. If the radar's minimum detection distance could reach a few millimeters, the radar could accurately distinguish between covered foreign objects and parked vehicles above it based on the distance to the detected target. However, the reality is that the radar's minimum detection distance is inversely proportional to its operating bandwidth. Currently common millimeter-wave radars are far from capable of supporting such a large operating bandwidth. When the target is relatively close (usually within a single radar resolution unit), the radar's detection distance is inaccurate. When the distance between the car chassis and the radar exceeds the radar's minimum detection distance or minimum resolution unit, the radar can accurately detect the distance from the car chassis to the radar, thereby accurately determining that there is a vehicle parked above; when the car chassis is very low, or the detection module is installed at a high height, the distance between the car chassis and the radar is less than the radar's minimum detection distance or minimum resolution unit, and the target distance and signal strength information detected by the radar is likely to be similar to the information detected when covered by foreign objects. The radar cannot accurately distinguish between the above two situations, resulting in false alarms.

[0004] The existing technical solutions are improved in the following three aspects:

[0005] 1. Increase the working bandwidth as much as possible from the hardware system, but this solution is costly and has the risk of frequency violation;

[0006] 2. The frequency corresponding to the peak point of the main lobe of the spectrum is used to determine whether there is a foreign object covering the parking detection module. When the frequency of the main lobe peak point is lower than a certain threshold and the peak intensity is higher than a certain threshold, it is considered to be covered by a foreign object. However, this solution is relatively rough. When the vehicle chassis is low, the main peak characteristics of the detection signal spectrum and the signal spectrum when there is a foreign object are similar, which can easily lead to misjudgment.

[0007] 3. Use dual-mode or multi-mode detection mode to reduce the confidence of radar detection results. This solution is complex and costly.

[0008] Therefore, further improvements are made to the above problems. Summary of the Invention

[0009] The main purpose of the present invention is to provide a foreign object coverage detection method based on millimeter-wave radar parking detection. Under limited working bandwidth, the spectrum of the detection signal is divided into two frequency bands: medium and low. Through comprehensive analysis of the signal characteristics in the above two frequency bands, it is judged whether the status above the parking detection module is a car, no car, or foreign object coverage. The method has the advantages of sensitive detection, high accuracy and easy use.

[0010] To achieve the above objectives, the present invention discloses a foreign object coverage detection method based on millimeter wave radar parking detection, which is used to determine the parking state and whether the parking detection module is covered by foreign objects, including the following steps:

[0011] Step S1: The parking detection module samples the acquired detection signal to obtain a sampled signal and pre-processes the sampled signal;

[0012] Step S2: performing spectrum calculation processing on the pre-processed sampling signal to obtain a spectrum curve of the sampling signal;

[0013] Step S3: Extract the frequency x of the maximum peak on the spectrum curve p And the signal intensity y corresponding to the maximum peak p , according to the frequency x of the maximum peak p and signal strength y p Determine the parking status above the parking detection module and whether it is covered by foreign objects.

[0014] As a further preferred technical solution of the above technical solution, step S3 is specifically implemented as the following steps:

[0015] Step S3.1: When the signal strength y p Less than the preset detection threshold y th , it is determined that there is no car above the parking detection module and no foreign objects covering it;

[0016] Step S3.2: When the signal strength y pGreater than or equal to the preset detection threshold y th , then according to the frequency x p With the preset detection threshold x th The relationship between them can be used to further determine the parking status and whether the parking detection module is covered by foreign objects.

[0017] As a further preferred technical solution of the above technical solution, step S3.2 is specifically implemented as the following steps:

[0018] Step S3.2.1: When the frequency x p Greater than or equal to the detection threshold x th , it is determined that there is a vehicle parked above the parking detection module;

[0019] Step S3.2.2: When the frequency x p Less than the detection threshold x th , then the calculated mid-frequency signal energy is used to further determine whether the parking detection module is covered by foreign objects.

[0020] As a further preferred technical solution of the above technical solution, step S3.2.2 is specifically implemented as the following steps:

[0021] Step S3.2.2.1: According to the formula Calculate the mid-frequency signal energy of the spectrum curve, where n1 is the preset start frequency of the mid-frequency band and n2 is the preset end frequency of the mid-frequency band, where:

[0022] When the calculated mid-frequency signal energy p sum Less than the preset detection threshold p th , it is determined that the parking detection module is covered by foreign matter;

[0023] When the calculated mid-frequency signal energy p sum Greater than or equal to the preset detection threshold p th , it is determined that there is a vehicle parked above the parking detection module.

[0024] As a further preferred technical solution of the above technical solution, in step S1, the preprocessing includes fast Fourier transform and MUSIC spectrum algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the foreign body coverage detection method based on millimeter wave radar parking detection of the present invention.

[0026] Figure 2 This is a detection signal spectrum analysis diagram of the foreign object coverage detection method based on millimeter wave radar parking detection of the present invention. DETAILED DESCRIPTION

[0027] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0028] In the preferred embodiment of the present invention, those skilled in the art should note that the millimeter wave radar and the like involved in the present invention may be regarded as prior art.

[0029] Preferred embodiment.

[0030] The present invention discloses a foreign object coverage detection method based on millimeter wave radar parking detection, which is used to determine the parking state and whether the parking detection module is covered by foreign objects, including the following steps:

[0031] Step S1: The parking detection module samples the acquired detection signal to obtain a sampled signal and pre-processes the sampled signal;

[0032] Step S2: performing spectrum calculation processing on the pre-processed sampling signal to obtain a spectrum curve of the sampling signal;

[0033] Step S3: Extract the frequency x of the maximum peak on the spectrum curve p And the signal intensity y corresponding to the maximum peak p , according to the frequency x of the maximum peak p and signal strength y p Determine the parking status above the parking detection module and whether it is covered by foreign objects.

[0034] Specifically, step S3 is implemented as follows:

[0035] Step S3.1: When the signal strength y p Less than the preset detection threshold y th , it is determined that there is no car above the parking detection module and no foreign objects covering it;

[0036] Step S3.2: When the signal strength y p Greater than or equal to the preset detection threshold y th , then according to the frequency x p With the preset detection threshold x th The relationship between them can be used to further determine the parking status and whether the parking detection module is covered by foreign objects.

[0037] More specifically, step S3.2 is implemented as follows:

[0038] Step S3.2.1: When the frequency xp Greater than or equal to the detection threshold x th , it is determined that there is a vehicle parked above the parking detection module;

[0039] Step S3.2.2: When the frequency x p Less than the detection threshold x th , then the calculated mid-frequency signal energy is used to further determine whether the parking detection module is covered by foreign objects.

[0040] Furthermore, step S3.2.2 is specifically implemented as the following steps:

[0041] Step S3.2.2.1: According to the formula Calculate the mid-frequency signal energy of the spectrum curve, where n1 is the preset start frequency of the mid-frequency band and n2 is the preset end frequency of the mid-frequency band, where:

[0042] When the calculated mid-frequency signal energy p sum Less than the preset detection threshold p th , it is determined that the parking detection module is covered by foreign matter;

[0043] When the calculated mid-frequency signal energy p sum Greater than or equal to the preset detection threshold p th , it is determined that there is a vehicle parked above the parking detection module.

[0044] Furthermore, in step S1, the preprocessing includes fast Fourier transform and MUSIC spectrum algorithm.

[0045] like Figure 2 As shown, it is the spectrum of the actual detected signal under three different conditions when simulating the millimeter-wave radar to detect parking conditions: Curve 1, no obstruction (no parking and no foreign objects covering the simulation detection module); Curve 2, wet tissue coverage (simulating the coverage of objects such as accumulated water that have a shielding effect on electromagnetic waves); Curve 3, metal plate obstruction about 10 cm above the parking detection module (simulating a vehicle parked above the module, and the vehicle chassis is low, lower than a distance resolution unit of the radar). Curve 4 is the threshold curve. When the detection curve is higher than the threshold curve, it is determined that there is a target above the module. In normal detection, the peak point p of the detection signal spectrum is detected. m The corresponding frequency and intensity (x p ,y p ), to determine whether there is a parking vehicle or foreign objects covering the upper part. Curves 2 and 3 both exceed the threshold curve 4, indicating that there is a target above the module. For radars working in FMCW mode, and there is only one target in front of the module, its detection distance is the same as x pAssuming that the radar working bandwidth is wide enough and the minimum detection distance is small enough, the radar detection indication distance of metal plate obstruction should be greater than that of foreign object coverage, that is, x p2 >x p1 However, due to the limited working bandwidth of the radar, it is far from being able to achieve such a small minimum detection distance and high distance resolution. Therefore, when the target distance is close to or less than the actual minimum detection distance, the target distance detected by the radar is inaccurate. Figure 1 The main peak features of the peaks of curves 2 and 3 are similar, and even x p1 >x p2 Therefore, only the maximum peak point information of the detection signal spectrum or the main peak feature where the peak point is located is judged. Curve 3 corresponds to the situation of foreign matter coverage, which is inconsistent with the actual situation.

[0046] Although the maximum peak points of curves 2 and 3 are both located in the low-frequency band and the main peak characteristics of their peak points are similar, it is impossible to use this alone to distinguish between foreign object coverage and short-distance overhead obstruction. However, there are significant differences in the spectral characteristics of the mid-frequency bands: Curve 3 has obvious sidelobes next to the main peak where the peak is located. The sidelobes are located in the mid-frequency range and have higher energy. When there is a close target obstructing the parking detection module, the radar display detects the target at a farther distance due to the multipath effect of the electromagnetic waves, which means that the mid-frequency signal spectrum energy is higher. The comprehensive detection signal spectrum low-frequency and mid-frequency signal characteristics can accurately distinguish between foreign object coverage and target obstruction within a limited working bandwidth.

[0047] To this end, the principle of the present invention is:

[0048] The millimeter wave radar uses FMCW detection mode to detect the parking status (car or no car) above the parking detection module and whether it is covered by foreign objects. The algorithm detection flow chart is as follows Figure 1 The steps are described as follows:

[0049] 1. Sample the detection signal and pre-process the sampled signal, including background calibration, temperature calibration, noise reduction, DC component removal, windowing, zero padding, etc.;

[0050] 2. Use FFT, MUSIC and other spectrum calculation methods to calculate the detection signal spectrum;

[0051] 3. Extract the frequency and signal strength information of the maximum peak on the spectrum curve (x p ,y p );

[0052] 4. Set the peak signal strength y p and the preset detection threshold y th In comparison, when yp <y th When the parking detection module is not covered by a vehicle or foreign objects, it will proceed to the next step of judgment;

[0053] 5. The frequency x corresponding to the spectrum peak p With the preset detection threshold x th In comparison, when x p ≥x th When the radar detects the target, it is considered that the target distance exceeds the minimum detection distance. The radar range is calibrated and it is determined that there is a vehicle parked above the detection module. Otherwise, it is considered that the target distance above the radar is small. At this time, the detection module may be covered by foreign objects or a target at a small distance. Then the next step is judged.

[0054] Calculate the mid-frequency signal energy, Where n1 and n2 are the start and end frequencies of the preset mid-frequency band. sum <p th When the detection module is detected, it is determined that there is a foreign object covering the top, otherwise it is determined that there is a parked vehicle above it.

[0055] It is worth mentioning that the technical features such as millimeter-wave radar involved in the patent application of this invention should be regarded as prior art. The specific structure, working principle and possible control method and spatial layout method of these technical features can be selected by conventional means in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated.

[0056] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A foreign object coverage detection method based on millimeter wave radar parking detection, used to determine the parking state and whether the parking detection module is covered by foreign objects, characterized in that: The following steps are involved: Step S1: the parking detection module samples the acquired detection signal to obtain a sampled signal and pre-processes the sampled signal; Step S2: performing spectrum calculation processing on the preprocessed sampling signal to obtain a spectrum curve of the sampling signal; Step S3: Extract the frequency x of the maximum peak on the spectrum curve p And the signal intensity y corresponding to the maximum peak p , according to the frequency x of the maximum peak p and signal strength y p Determine the parking status above the parking detection module and whether it is covered by foreign objects; Step S3 is specifically implemented as the following steps: Step S3.1: When the signal strength y p Less than the preset detection threshold y th , it is determined that there is no car above the parking detection module and no foreign objects cover it; Step S3.2: When the signal strength y p Greater than or equal to the preset detection threshold y th , then according to the frequency x p With the preset detection threshold x th The relationship between the parking state and the parking detection module is further determined to determine whether the parking detection module is covered by foreign objects; Step S3.2 is specifically implemented as follows: Step S3.2.1: When the frequency x p Greater than or equal to the detection threshold x th , it is determined that there is a vehicle parked above the parking detection module; Step S3.2.2: When the frequency x p Less than the detection threshold x th , then the calculated mid-frequency signal energy is used to further determine whether the parking detection module is covered by foreign objects.

2. The method for detecting foreign object coverage based on millimeter wave radar parking detection according to claim 1, characterized in that: Step S3.2.2 is specifically implemented as follows: Step S3.2.2.1: According to the formula Calculate the signal energy of the intermediate frequency band of the spectrum curve, n1 is the preset start frequency of the intermediate frequency band, n2 is the preset end frequency of the intermediate frequency band, where: When the calculated mid-frequency signal energy p sum Less than the preset detection threshold p th , it is determined that the top of the parking detection module is covered by foreign matter; When the calculated mid-frequency signal energy p sum Greater than or equal to the preset detection threshold p th , it is determined that there is a vehicle parked above the parking detection module.

3. The method for detecting foreign body coverage based on millimeter wave radar parking detection according to claim 2, characterized in that: In step S1, preprocessing includes fast Fourier transform and MUSIC spectrum algorithm.

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