Radar sensor calibration method

Abstract

According to the radar sensor calibration method, a Fresnel lens and a light source located on the other side of the Fresnel lens are arranged right opposite to a medium-range radar sensor (MRR), a calibration mirror is arranged on the MRR, the calibration mirror and the Fresnel lens are arranged in parallel in the initial state, the light source is located on the focus of the Fresnel lens, the light source becomes parallel light after passing through the lens, and the parallel light is transmitted to the MRR. Calibration in the horizontal direction and the vertical direction is carried out by collecting and analyzing an image reflected back to the light source plane by the calibration mirror. Through an optical measurement method, deviation of the radar sensor in the horizontal direction and the vertical direction is calibrated and compensated, and it is ensured that the sensor can provide accurate measurement data under various environmental conditions. Through optical measurement and automatic rotation, the deviation between the radar axis and the vehicle dynamics axis can be accurately measured; the rapid characteristic of the passive calibration method can greatly shorten the total time required by calibration.

Description

Technical Field

[0001] The present invention relates to a technology in the field of radar calibration, in particular to a radar sensor calibration method. Background Art

[0002] With the rapid development of the automotive industry, the application of advanced driver assistance systems (ADAS) is becoming more and more widespread. Among them, radar sensors are key components for realizing functions such as automatic emergency braking and adaptive cruise control of vehicles. However, during the production process, the installation position of the radar sensor may deviate, resulting in its detection performance being affected. Therefore, it is crucial to accurately calibrate the radar sensor. Through calibration, the axis of the radar sensor can be aligned with the dynamic axis of the vehicle to ensure the normal use of the zero-kilometer function and performance when the vehicle is off the line. Existing radar calibration methods have problems such as low efficiency, insufficient accuracy, and strong dependence on the environment. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a radar sensor calibration method, which uses an optical measurement method to calibrate and compensate for the deviation of the radar sensor in the horizontal and vertical directions, ensuring that the sensor can provide accurate measurement data under various environmental conditions. Through optical measurement and automatic rotation, the deviation between the radar axis and the vehicle dynamics axis can be accurately measured; the fast characteristics of the passive calibration method can greatly shorten the total time required for calibration.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a radar sensor calibration method. A Fresnel lens and a light source located on the other side of the Fresnel lens are arranged facing a mid-range radar sensor (MRR), wherein a calibration mirror is arranged on the MRR, the calibration mirror is arranged parallel to the Fresnel lens in an initial state, the light source is located at the focus of the Fresnel lens, and the light source becomes parallel light after passing through the lens. Calibration in the horizontal and vertical directions is performed by collecting and analyzing an image reflected back to a light source plane by the calibration mirror.

[0006] The present invention relates to a system for implementing the above method, comprising: an image acquisition and preprocessing unit, an edge and corner point detection unit, a light spot positioning and angle calculation unit and an actuator control unit, wherein: the image acquisition and preprocessing unit acquires an image reflected back to a light source plane by a calibration mirror, and performs preprocessing to obtain a high-quality image for subsequent edge and corner point detection; the edge and corner point detection unit identifies edge and corner point information in the preprocessed image; the light spot positioning and angle calculation unit determines the position of the reflected light spot in the image, and calculates the angle between the radar sensor and the horizontal and vertical directions, that is, the calibration angle data of the radar sensor; the actuator control unit controls the actuator to automatically adjust the inclination angle of the reflective lens according to the calibration angle data.

[0007] The preprocessing refers to: grayscale processing, Gaussian filtering and binarization processing are performed on the original image data obtained from the image acquisition device.

[0008] The identification refers to: based on the high-quality image, applying the Canny operator and other edge detection algorithms to identify the edges in the image, and then using the Harris corner detection algorithm to detect the corners in the image to obtain edge and corner information for light spot positioning.

[0009] The angle is determined by identifying the bright spots in the image and determining the coordinates of the reflected light spots through the threshold segmentation method, converting the image coordinates into world coordinates according to the geometric relationship between the image acquisition device and the calibration mirror, and then calculating the angle between the radar sensor and the horizontal and vertical directions.

[0010] The automatic adjustment described above uses, but is not limited to, a stepping motor or other actuator to move the direction and distance according to the voltage output by the actuator control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the passive calibration schematic;

[0012] Figure 2 Schematic diagram of automatic adjustment mechanism. DETAILED DESCRIPTION

[0013] like Figure 1 As shown, this embodiment relates to a radar sensor calibration method, by setting a Fresnel lens and a light source located on the other side of the Fresnel lens directly facing a mid-range radar sensor (MRR), wherein a calibration mirror is provided on the MRR, and the calibration mirror is arranged parallel to the Fresnel lens in an initial state, and the light source is located at the focus of the Fresnel lens. The light source becomes parallel light after passing through the lens, and the horizontal and vertical directions are calibrated by collecting and analyzing the image reflected back to the light source plane by the calibration mirror, which specifically includes:

[0014] Step 1: Use an image acquisition device to capture the image reflected by the calibration mirror back to the light source plane and perform preprocessing.

[0015] The preprocessing includes grayscale, filtering, binarization and other operations to improve image quality, including reducing image noise and enhancing image contrast to make the reflected light spots more obvious.

[0016] Step 2: Use an edge detection algorithm (such as the Canny operator, the Sobel operator, etc.) to identify edge information in the preprocessed image, and then detect corner information in the image using the Harris corner detection algorithm, the Shi-Tomasi corner detection algorithm, etc.

[0017] Step 3: Light spot positioning and angle calculation, specifically including:

[0018] 3.1 Determine the coordinates (x, y) of the reflected light point in the image by identifying the bright spot in the image through the threshold segmentation method;

[0019] 3.2 Through the geometric relationship between the image acquisition device and the calibration mirror, the image coordinates are converted into world coordinates through coordinate transformation;

[0020] 3.3 As Figure 1 As shown, according to the deviation between the actual coordinates of the reflected light point and the expected position, the angle between the radar sensor and the horizontal direction and the vertical direction is calculated, which is: Where: (x1, y1) are the coordinates of the origin of the incident light, and (x2, y2) are the coordinates where the incident light intersects the surface.

[0021] like Figure 2 As shown, according to the calculation results, the stepper motor or other actuator is controlled to automatically adjust the tilt angle of the reflective lens to achieve the purpose of changing the laser light path. This can be achieved through mechanical adjustment or optical adjustment:

[0022] Mechanical adjustment: Changing the angle and direction of a lamp through mechanical means, such as adjustable lamp heads and lamp holders.

[0023] Optical adjustment: Changing the angle and direction of light through optical elements, such as using mirrors, lenses and other optical elements.

[0024] After specific actual experiments, in the specific environment setting of 25℃ and 50% of the ambient temperature inside the control room, the light source intensity is set to 100mW, the focal length of the Fresnel lens is set to 500mm, the image acquisition frequency is set to 30 frames / second, the edge detection algorithm is the Canny operator, the threshold is set to 0.1 and 0.2, the corner detection algorithm is the Harris corner detection, the threshold is set to 0.01, and the stepper motor response time is 5ms. The calibration accuracy achieved by the above method is: ±0.1° in the horizontal direction and ±0.1° in the vertical direction. The calibration time is an average of 3 seconds / time. The standard deviation after repeated calibration for 10 times is: 0.05° in the horizontal direction and 0.05° in the vertical direction. The influence of environmental changes (temperature changes from 20℃ to 30℃, humidity changes from 40% to 60%) on the calibration accuracy is: the horizontal change does not exceed ±0.2°, and the vertical change does not exceed ±0.2°. System stability test: after 100 hours of continuous operation, the calibration accuracy remains above 95% of the initial accuracy.

[0025] Experimental results show that the radar sensor calibration method and system of the present invention can maintain high accuracy and fast response under different environmental conditions, and have good stability and reliability. Compared with the prior art, the present invention realizes the calibration and compensation of the deviation of the radar sensor in the horizontal and vertical directions through an optical measurement method, improves the calibration accuracy, and is more accurate than the existing mechanical adjustment method.

[0026] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A radar sensor calibration method, characterized in that: A Fresnel lens and a light source on the other side of the Fresnel lens are set facing the mid-range radar sensor (MRR), wherein a calibration mirror is provided on the MRR. In the initial state, the calibration mirror is set parallel to the Fresnel lens, and the light source is located at the focus of the Fresnel lens. The light source becomes parallel light after passing through the lens. The horizontal and vertical calibration is performed by collecting and analyzing the image reflected back to the light source plane by the calibration mirror.

2. A radar sensor calibration system for implementing the method of claim 1, characterized in that: include: An image acquisition and preprocessing unit, an edge and corner point detection unit, a light spot positioning and angle calculation unit, and an actuator control unit, wherein: the image acquisition and preprocessing unit acquires the image reflected by the calibration mirror back to the light source plane, and performs preprocessing to obtain a high-quality image for subsequent edge and corner point detection; The edge and corner point detection unit identifies the edge and corner point information in the preprocessed image; the light spot positioning and angle calculation unit determines the position of the reflected light spot in the image and calculates the angle between the radar sensor and the horizontal and vertical directions, that is, the calibration angle data of the radar sensor; the actuator control unit controls the actuator to automatically adjust the inclination angle of the reflective lens according to the calibration angle data.

3. The radar sensor calibration system according to claim 2, characterized in that: The preprocessing refers to: grayscale processing, Gaussian filtering and binarization processing are performed on the original image data obtained from the image acquisition device.

4. The radar sensor calibration system according to claim 2, characterized in that: The identification refers to: based on the high-quality image, applying the Canny operator and other edge detection algorithms to identify the edges in the image, and then using the Harris corner detection algorithm to detect the corners in the image to obtain edge and corner information for light spot positioning.

5. The radar sensor calibration system according to claim 2, characterized in that: The angle is determined by identifying the bright spots in the image and determining the coordinates of the reflected light spots through the threshold segmentation method, converting the image coordinates into world coordinates according to the geometric relationship between the image acquisition device and the calibration mirror, and then calculating the angle between the radar sensor and the horizontal and vertical directions.

6. The radar sensor calibration system according to claim 2, characterized in that: The automatic adjustment is achieved by using a stepping motor.

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