CN108898139A - Laser radar data anti-interference processing method and its experimental provision under a kind of rainy environment - Google Patents

Abstract

The present invention provides the laser radar data anti-interference processing methods and its experimental provision under a kind of rainy environment.The device includes rubber tube, laser radar bracket, water water tank, plug, rain-proof lower stop piece, laser radar, rain-proof upper stop piece.This method sample to the data for simulating the laser radar in the environment that rains and converts image for laser data according to the distance of measurement and laser data intensity, and after filtering, the rejecting of rainy noise spot is carried out using successive frame comparison algorithm.To two-dimensional laser radar, the processing method of data under the environment that rains provides a solution to the present invention, can promote the use of outer scene and change the location navigation to rain under environment outside little robot chamber.

Description

A LiDAR data anti-jamming processing method and its experiment in rainy environment device

technical field

The invention relates to the technical field of laser scanning, in particular to a laser radar data anti-jamming processing method in a rainy environment and an experimental device thereof.

Background technique

Positioning and navigation technology is a key technology of mobile robots. According to the different sensors used, it can be divided into positioning and navigation based on laser sensors and positioning and navigation based on visual sensors. The method based on the visual sensor is to use the camera to perceive the environment. Compared with the visual sensor, the laser radar has strong anti-interference ability and accurate information. Therefore, the method of environmental perception based on the laser sensor has been widely used in mobile robot navigation. Laser-based positioning and navigation is a mobile robot that collects the information of the laser radar carried by the mobile robot, and determines the landmark points in the environment and the position of the robot in the environment through the processing and analysis of the sensor information, so as to realize the construction of environmental maps, path planning, and autonomous movement. and obstacle avoidance.

The environmental perception of robots in rainy conditions is often based on visual sensor environmental perception. The main reason is that lidar uses infrared laser ranging, so its data will generally be reflected by raindrops in outdoor rainy environments. and refraction interference caused errors. This vision-based approach removes raindrops in the environment as dynamic distractions. Since the visual sensor itself is easily disturbed by changes in ambient light and has limited accuracy, this method cannot completely solve the problem effectively. In order to make full use of the high ranging accuracy and high stability of the laser sensor itself, it is of great significance to study the anti-jamming algorithm of the lidar data in the rainy environment.

Contents of the invention

In view of the defects existing in the prior art, the object of the present invention is to provide an anti-jamming processing method and an experimental device for laser radar data in a rainy environment. The device can effectively simulate the rainy environment, and the processing method can eliminate error points for the laser data in the environment.

To achieve the above object, the present invention adopts the following technical solutions:

A method for anti-jamming processing of laser radar data in a rainy environment, comprising the steps of:

1) Convert the original laser data containing error points into a grayscale image. The conversion principle is to convert each laser point into a pixel in the image according to the light intensity and distance value of the data returned by the laser radar. The gray value of the pixel is based on the light intensity. Strong normalization processing;

2) After the data of the two-dimensional lidar is converted into a grayscale image, due to the error of the lidar itself and the error introduced in the normalization process, the collected data will inevitably contain noise, so the filtering method is used to remove noise and interference;

3) Discrete sampling is performed on the lidar data, and the continuous frame algorithm is used to filter and eliminate data from images containing error points caused by raindrops.

In the step 1), the laser data is converted into a grayscale image, including the following steps:

1.1) The setting of image pixels in the plane depends on the data resolution of the lidar, that is, the position of each laser point is a pixel, and the position of the pixel is the distance of the data returned by the lidar;

1.2) The gray value of the pixel is normalized by the laser intensity returned by the lidar.

The filtering process in step 2) includes the following steps:

2.1) Use the histogram equalization method to process the image, so that the gray level distribution on the image histogram changes from dense to uniform, so that the overall contrast effect of the image is enhanced;

2.2) The median filter is used for image preprocessing, and the value of the pixel with a larger difference with the surrounding pixels is replaced by a value with a smaller gray value difference with the surrounding pixels.

In the step 3), the data frame of the lidar is sampled, and the setting of the sampling frequency needs to meet the following principles:

3.1) All the laser data points obtained by scanning the lidar itself are one frame. Since the scanning frequency of the lidar is high, it is necessary to set the sampling frequency and sample the data of the lidar at intervals for subsequent algorithms. deal with;

3.2) Determine the sampling frequency according to the temporal characteristics of raindrops in the rainy environment, so that the same pixel in two consecutive frames of images cannot be disturbed by raindrops at the same time.

An experimental device for simulating a rainy environment, so that the above method can be verified, including a rubber tube, a laser radar bracket, a water storage tank, a plug, a rain-proof lower baffle, a laser radar, and a rain-proof upper baffle, the rubber tube Installed on the top of the water storage tank, the rubber tube is externally connected to a water flow controller, through which a uniform water flow with a controllable flow rate is injected into the rubber tube. , so as to form a simulated raining environment with adjustable rainfall and rain speed; the rain-proof bottom plate is fixed on the bottom of the water storage tank, the lidar is fixed on the rain-proof bottom plate through the laser radar bracket, and the rain-proof The upper block and the rain-proof lower block are connected by hexagonal bolts, so that the laser radar is located under the rain-proof upper block; the bottom of the water storage tank is provided with a water outlet, and a plug is also provided on the water outlet.

The water flow controller is any device with feedback control capable of providing a stable water flow rate.

The rainproof lower baffle and the rainproof upper baffle can prevent water from splashing into the laser radar, but do not block the normal scanning range of the laser radar, wherein the installation position of the hexagonal bolt should be within the minimum range of the laser radar, Or it can be removed from the lidar data through prior position calibration. In this case, the hexagonal bolt does not have much impact on the normal detection of the lidar.

The shell of the water storage tank is made of non-transparent material or its surface is evenly painted with color so that the laser radar can detect and keep the same reflection intensity of the laser radar within the same detection distance.

In the working state, a fixed flow rate of water is passed through the rubber hose to create a simulated raining environment around the lidar. The upper and lower layers of rain-proof baffles can prevent water droplets from splashing into the lidar, and water droplets fall into the water storage tank. There is a plug at the bottom of the water tank, which can pour out the stored water after the experiment. The maximum detection range of the lidar is the water tank shell, which belongs to the static environment, and the raindrops generated by the simulated rain device will interfere with the laser data. Sampling the laser radar data containing interference points and converting the laser data into images according to the measured distance and laser data intensity, after filtering, the continuous frame comparison algorithm is used to eliminate rain interference points

As a selection method, the water tank shell is a barrel-shaped structure, made of acrylic plate material, and coated with a reflective coating at the detection height of the laser radar to enhance the reflection intensity of the laser point.

As an installation method, a laser radar with omnidirectional 360° scanning is used, but it is not installed in the center of the water tank.

Compared with the prior art, the present invention has the following prominent substantive features and remarkable advantages:

The invention provides a method for anti-interference processing of laser radar data in a rainy environment. By simulating a rainy environment, a solution is provided for the processing method of two-dimensional laser radar data in a rainy environment, which can be extended and applied to external scene changes. Positioning and navigation of a small robot in an outdoor rainy environment. The device of the invention sets a static environment simulating rain, and it is verified that the method can effectively eliminate the interference of laser data in the static environment caused by the reflection and refraction of raindrops.

Description of drawings

Fig. 1 is a structural schematic diagram of an experimental device for simulating a rainy environment according to the present invention.

FIG. 2 is a grayscale image converted from laser data obtained by a single scan of the lidar without interference from raindrops in an embodiment of the present invention.

FIG. 3 is a grayscale image converted from laser data obtained by a single scan of the lidar in an embodiment of the present invention with interference from raindrops.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the following examples are intended to facilitate the understanding of the present invention, but do not limit it in any way.

A method for anti-jamming processing of laser radar data in a rainy environment, comprising the steps of:

1) Convert the original laser data containing error points into a grayscale image. The conversion principle is to convert each laser point into a pixel in the image according to the light intensity and distance value of the data returned by the laser radar. The gray value of the pixel is based on the light intensity. Strong normalization processing;

2) After the data of the two-dimensional lidar is converted into a grayscale image, due to the error of the lidar itself and the error introduced in the normalization process, the collected data will inevitably contain noise, so the filtering method is used to remove noise and interference;

3) Discrete sampling is performed on the lidar data, and the continuous frame algorithm is used to filter and eliminate data from images containing error points caused by raindrops.

In the step 1), the laser data is converted into a grayscale image, including the following steps:

1.1) The setting of image pixels in the plane depends on the data resolution of the lidar, that is, the position of each laser point is a pixel, and the position of the pixel is the distance of the data returned by the lidar;

1.2) The gray value of the pixel is normalized by the laser intensity returned by the lidar.

The filtering process in step 2) includes the following steps:

2.1) Use the histogram equalization method to process the image, so that the gray level distribution on the image histogram changes from dense to uniform, so that the overall contrast effect of the image is enhanced;

2.2) The median filter is used for image preprocessing, and the value of the pixel with a larger difference with the surrounding pixels is replaced by a value with a smaller gray value difference with the surrounding pixels.

The scanning frequency of the lidar itself is 7Hz. After analyzing the time characteristics of raindrops falling, we know that when the falling speed of raindrops is constant, the frequency of laser data interference is lower than the frequency of the lidar itself. In the step 3), the data frame of the lidar is sampled, and the setting of the sampling frequency needs to meet the following principles:

3.1) All the laser data points obtained by scanning the lidar itself are one frame. Since the scanning frequency of the lidar is high, it is necessary to set the sampling frequency and sample the data of the lidar at intervals for subsequent algorithms. deal with;

3.2) Determine the sampling frequency according to the temporal characteristics of raindrops in the rainy environment, so that the same pixel in two consecutive frames of images cannot be disturbed by raindrops at the same time.

Adopt the document: Xiaoopeng Zhang, Hao Li, Ying Qi, etal. Rain Removal in Videoby Combining Temporal and Chromatic Properties [C]. IEEE International Conference on Digital Object Identifier, 2006: 461-464P. The following method recorded in:

There are 3 consecutive frames of video images, which are the n-1th frame, the nth frame and the n+1th frame respectively, and the gray value of each pixel in each frame is I _n-1 , I _n and I _n+1 ; assuming that the same pixel in two consecutive frames of video images cannot be covered by rain and snow at the same time, then the gray values of the n −1th frame and the n+1th frame are equal, that is

I _{n-1 =} I _n+1

Then, in the nth frame, the change ΔI of the gray value caused by rain and snow must satisfy the formula:

ΔI =I _no -I _n-1 = I _no -I _{n+1 =} c

ΔI is a positive value, and the threshold c is a positive number. Take the value between c=1~3 , when the above formula is established, the pixels disturbed by rain in the nth frame can be detected.

As shown in Figure 1, an experimental device for simulating a rainy environment enables the above method to be verified, including a rubber tube 1, a lidar bracket 2, a water storage tank 3, a plug 4, a rain-proof baffle 5, and a lidar 6. The rain-proof upper block 7, the rubber tube 1 is installed on the top of the water storage tank 3, the rubber tube 1 is externally connected to a water flow controller, and a uniform water flow with a controllable flow rate is injected into the rubber tube 1 through the water flow controller. Holes are evenly punched on the rubber tube 1, and the water flow drips downward through the uniform holes on the rubber tube 1, thereby forming a simulated raining environment with adjustable rainfall and rain speed; At the bottom, the laser radar 6 is fixed on the rainproof lower cover 5 through the laser radar bracket 2, and the rainproof upper cover 7 is connected with the rainproof lower cover 5 by hexagonal bolts, so that the laser radar 6 is positioned at the rainproof Below the upper blocking piece 7; the bottom of the water storage tank 3 is provided with a water outlet, and a plug 4 is also provided on the water outlet.

The water flow controller is any device with feedback control capable of providing a stable water flow rate, such as a valve, a pressure pump, and the like.

Described rainproof lower baffle 5 and rainproof upper baffle 7 can prevent water flow from splashing into laser radar 6, but do not block the normal scanning range of laser radar 6, and wherein the installation position of hex bolt should be in the minimum measurement of laser radar 6 In this case, the hexagonal bolt does not have much impact on the normal detection of the LiDAR 6.

The shell of the water storage tank 3 is made of non-transparent material or its surface is evenly coated with color so that the laser radar 6 can detect it and keep the same reflection intensity of the laser radar 6 within the same detection distance.

The scanning range of the laser radar 6 is a plane parallel to the horizontal plane to obtain plane information, and the maximum detection range is the shell of the water storage tank 3 . In this embodiment, the RPLidar A1 two-dimensional laser radar of Shanghai Silan Technology Co., Ltd. is selected. The frequency of the laser radar is 7 Hz, and the maximum distance measurement range is 5 meters. The lidar is powered by a 12V power supply, and transmits communication data with the PC through a USB cable.

The information output by the laser radar 6 includes angle, distance and light intensity information. The water storage tank 3 shell is its maximum detection range. When the raining device is not activated, the laser detection data are evenly distributed on the maximum detection edge. Take the position of Lidar 6 as the center of the image to create a grayscale image: the position of each pixel is the position of the data point of Lidar 6, and the grayscale value is the normalized value of the light intensity. The size of each pixel depends on the data resolution of Lidar 6. When the laser is outside the detection range, that is, the blocked position can be considered as a maximum gray value of 255, and the point on the laser optical path can be considered as a gray value of 0. According to this principle, the grayscale image converted from the laser data without raindrop interference can be obtained, as shown in Figure 2.

When the experimental device simulating the rainy environment is activated, the data detected by the laser is interfered by the refraction or reflection of the raindrops. Similarly, take the position of Lidar 6 as the center of the image to create a grayscale image: the position of each pixel is the position of the data point of Lidar 6, and the gray value is the normalized value of the light intensity. At this time, due to the reflection and refraction of the laser data by the raindrops, the edge position of part of the water storage tank 3 cannot be completely detected, and the reflected light intensity value also changes. By normalizing the light intensity and assigning a gray value, the gray image converted from the laser data with raindrop interference can be obtained, as shown in Figure 3.

Sampling the data of LiDAR 6 in the simulated rain environment and transforming the laser data into images according to the measured distance and laser data intensity, after filtering, the continuous frame comparison algorithm is used to eliminate the rain interference points.

In this embodiment, the terms "laser radar" and "two-dimensional laser radar" can be used interchangeably, and refer to a laser ranging device whose scanning range is a two-dimensional plane, and the information read from the device is a plane point, including Angle and distance information and intensity information of the laser spot.

In this embodiment, the laser data obtained by one scan of the lidar is the original data, and one scan obtained after sampling is a "data frame", and "one frame of data" should include all the data of one complete scan of the two-dimensional lidar.

In this embodiment, the terms "filtering", "noise reduction" and "noise removal" can be used interchangeably, and refer to a method or process of eliminating errors in lidar data.

Claims (8)

1. a lidar data anti-interference processing method under a rainy environment, is characterized in that, comprises the steps: 1) Convert the original laser data containing error points into a grayscale image. The conversion principle is to convert each laser point into a pixel in the image according to the light intensity and distance value of the data returned by the laser radar. The gray value of the pixel is based on the light intensity. Strong normalization processing; 2) After the data of the two-dimensional lidar is converted into a grayscale image, due to the error of the lidar itself and the error introduced in the normalization process, the collected data will inevitably contain noise, so the filtering method is used to remove noise and interference; 3) Discrete sampling is performed on the lidar data, and the continuous frame algorithm is used to filter and eliminate data from images containing error points caused by raindrops. 2. The anti-jamming processing method for lidar data in a rainy environment according to claim 1, wherein the step 1) converts the laser data into a grayscale image, comprising the following steps: 1.1) The setting of image pixels in the plane depends on the data resolution of the lidar, that is, the position of each laser point is a pixel, and the position of the pixel is the distance of the data returned by the lidar; 1.2) The gray value of the pixel is normalized by the laser intensity returned by the lidar. 3. The lidar data anti-jamming processing method under the rainy environment according to claim 1, characterized in that the filtering process in the step 2) includes the following steps: 2.1) Use the histogram equalization method to process the image, so that the gray level distribution on the image histogram changes from dense to uniform, so that the overall contrast effect of the image is enhanced; 2.2) The median filter is used for image preprocessing, and the value of the pixel with a larger difference with the surrounding pixels is replaced by a value with a smaller gray value difference with the surrounding pixels. 4. The anti-interference processing method for lidar data in a rainy environment according to claim 1, characterized in that, in the step 3), the data frame of the lidar is sampled, and the setting of the sampling frequency needs to meet the following principles : 3.1) All the laser data points obtained by scanning the lidar itself are one frame. Since the scanning frequency of the lidar is high, it is necessary to set the sampling frequency and sample the data of the lidar at intervals for subsequent algorithms. deal with; 3.2) Determine the sampling frequency according to the temporal characteristics of raindrops in the rainy environment, so that the same pixel in two consecutive frames of images cannot be disturbed by raindrops at the same time. 5. An experimental device for simulating a rainy environment, so that the above method can be verified, it is characterized in that it includes a rubber tube (1), a laser radar bracket (2), a water storage tank (3), a plug (4), an anti The rain shield (5), the laser radar (6), and the rainproof upper shield (7), the rubber tube (1) is installed on the top of the water storage tank (3), and the rubber tube (1) is externally connected to the water flow controller , inject uniform water flow with controllable flow rate into the rubber tube (1) through the water flow controller, the rubber tube (1) is uniformly perforated, and the water flow drips downward through the uniform holes on the rubber tube (1), thereby forming rainfall , The simulated raining environment with adjustable rain speed; the rain-proof lower flap (5) is fixed on the bottom of the water storage tank (3), and the lidar (6) is fixed on the rain-proof On the lower baffle (5), the rainproof upper baffle (7) is connected with the rainproof lower baffle (5) through hexagonal bolts, so that the laser radar (6) is located under the rainproof upper baffle (7) A water outlet is provided at the bottom of the water storage tank (3), and a plug (4) is also provided on the water outlet. 6 . The experimental device for simulating a rainy environment according to claim 5 , wherein the water flow controller is any device with feedback control capable of providing a stable water flow velocity. 7. The experimental device for simulating a rainy environment according to claim 5, characterized in that the rain-proof lower cover (5) and the rain-proof upper cover (7) can prevent water from splashing into the laser radar (6) , but does not block the normal scanning range of the laser radar (6), where the installation position of the hexagonal bolt should be within the minimum range of the laser radar (6), or through the prior position calibration to be within the laser radar (6) data In this case, the hex bolt does not have much impact on the normal detection of the LiDAR (6). 8. The experimental device for simulating a rainy environment according to claim 5, characterized in that, the shell of the water storage tank (3) is made of non-transparent material or its surface is evenly painted with color, so that the laser radar (6) can Detect and keep the same reflection intensity of the lidar (6) within the same detection distance.