Anti-jamming multi-lidar system

Abstract

This invention provides an anti-interference multi-liquid radar system, comprising two or more lidars, each with a different emission frequency. Currently, most multi-liquid radar systems employ two or more single-photon array flash radars, emitting lasers at the same frequency. If two radars are located nearby, they can detect each other's flash arrays, leading to interference and significant noise. This invention addresses this by setting different emission frequencies for the multiple lidars, allowing each individual lidar to identify its own emitted signal based on frequency and subtract signals from other lidars when receiving signals.

Description

Technical Field

[0001] This invention relates to a multi-laser radar system, and more particularly to an anti-interference multi-laser radar system. Background Technology

[0002] Single-photon area array (SPA) flash lidar repeatedly emits flash lasers at high speed (typically around several million times per second). Each receiving unit of the SPA array can receive millions of results per second, accumulating the actual detection effect by analyzing each ranging time point. If the ranging distance is divided into a certain number of equal parts, such as 1000 equal parts, then the number of laser ranging counts in each part is accumulated. Finally, by analyzing the accumulated data in these 1000 equal parts, the results are plotted as a graph, and the highest peak is found to determine the flight time of the ranging, and then the object distance is calculated. Note: Assuming the lidar's frame rate is 10 frames per second, then each frame contains hundreds of thousands of accumulated flash laser data points. Assuming the lidar's ranging range is 20 meters, then each receiving unit divides the 20 meters into 1000 equal parts, which is 2 centimeters per part. The lidar will place the hundreds of thousands of ranging results from each frame into these 1000 equal parts according to the distance of each measurement. Irregular noise will be evenly distributed across 1000 equal divisions. If an object is detected in a certain cell, then there will be a large number of duplicate results in the division for that object's distance, which will be treated as ranging results. Noise data distributed in other divisions is ignored because the cumulative number of occurrences is below the threshold value.

[0003] Currently, most multi-LiDAR systems employ two or more single-photon array flash radars, emitting lasers at the same frequency. If two radars are nearby, they can detect each other's flashes because the second radar's flash laser will hit an object at a fixed distance. Since the emission frequency is the same, this will generate false detection data for the first radar at a fixed location, causing interference between the two or more radars. This results in significant noise. Furthermore, because both flashes operate at the same frequency, as long as both are emitting light, there will be noise at a fixed location, easily leading to analysis errors. The system may mistake the emitted light from other LiDARs for its own, making it impossible to accurately filter noise and producing erroneous results. These false receiving points become noise reflected in the LiDAR image, reducing the accuracy of the multi-LiDAR image. Summary of the Invention

[0004] This invention provides an anti-interference multi-lidar system to reduce mutual interference between lidars in a multi-lidar system.

[0005] The present invention provides an anti-interference multi-lidar system, which includes two or more lidars, each of which has a different transmission frequency.

[0006] Furthermore, in every two laser radars, the ratio of the absolute value of the larger transmission frequency to the absolute value of the smaller transmission frequency is not an integer; for example, one is a flash 7.8MHz and the other is a flash laser frequency of 7.5MHz.

[0007] Furthermore, all of the aforementioned lidars are single-photon area array lidars.

[0008] Furthermore, the multi-lidar system also includes a lidar signal analysis process:

[0009] S101. Determine the target radar's transmission frequency and set it as the standard transmission frequency;

[0010] S102. Extract the signal that conforms to the standard transmission frequency from the signal collected by the target radar. The extracted signal is the signal of the target radar.

[0011] Furthermore, in step S102, signals conforming to the standard transmission frequency are extracted from the signals collected by the target radar. These extracted signals, representing the signals of the target radar, include:

[0012] S1021. Based on the absolute value of the standard transmission frequency n, divide the signal stream per unit time into n equal parts;

[0013] S1022. Analyze each equal portion of the signal stream to ensure that the signal appearing at the same position in the n equal portions of the signal stream is the signal of the target radar;

[0014] S1023. Subtract all signals other than the target radar signal from each equal signal stream, and merge the target radar signals from the n equal signal streams to obtain the target radar signal within that unit of time.

[0015] Furthermore, the unit of time is 1 / 10 of a second.

[0016] Compared with the prior art, this invention sets the transmission frequencies of multiple lidars to be different (for example, 7.8MHz, 7.0MHz, 6.7MHz, etc.), so that when a single lidar receives a signal, it can identify its own transmitted signal by frequency and subtract the signals of other lidars. Attached Figure Description

[0017] Figure 1 This is a unit-time signal diagram showing that lasers with larger and smaller emission frequencies do not exhibit a multiple relationship in an embodiment of the present invention.

[0018] Figure 2 This is a unit-time signal diagram showing the multiple relationship between lasers with larger and smaller emission frequencies in an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] This invention discloses an anti-interference multi-lidar system, which includes two or more lidars, each with a different transmission frequency.

[0021] In this embodiment of the invention, the laser radar frequency is set differently so that different radars emit lasers at different laser emission frequencies. The lasers interfering with each other between two or more laser radars will have different time intervals when they hit the same receiving unit, due to the different emission frequencies of the other party, which makes it easier to obtain accurate laser radar signals.

[0022] Optionally, in any two of the aforementioned lidar transmission frequencies, the ratio of the absolute value of the larger transmission frequency to the absolute value of the smaller transmission frequency is not an integer (e.g., the larger transmission frequency is 7.8MHz, 7.0MHz, 6.7MHz, etc., while the smaller transmission frequency is 5MHz, 4MHz).

[0023] Among them, the ratio of the absolute value of the larger transmission frequency to the absolute value of the smaller transmission frequency is not an integer, that is, there is no multiple relationship between the frequencies of the various lidars.

[0024] If there is a multiple relationship between the frequencies of the various lidars, for example, the larger and smaller transmission frequencies are 1000MHz and 500MHz respectively, it is still impossible to avoid some signal noise that cannot be eliminated. This embodiment of the invention sets the ratio of the absolute value of the larger transmission frequency to the absolute value of the smaller transmission frequency in every two lidars to be a non-integer, thus creating a significant difference in the transmission frequencies of the lidars and facilitating noise signal elimination.

[0025] like Figure 1 , Figure 2 As shown, the upper signal of the figure is the signal image after a lower frequency lidar scans an object within a certain time period; the middle signal of the figure is the signal image after a higher frequency lidar scans an object within a certain time period; and the lower signal of the figure is a mixed signal image after a lower frequency lidar and a higher frequency lidar scan an object within a certain time period.

[0026] It should be noted that when a lidar is working, it sends out laser signals. These signals, upon reaching an object, are reflected back to the lidar. The lidar collects this reflected signal and, by calculating the time of flight and the array configuration, determines the object's distance from the lidar. When the external object is singular (with only one reflective surface), the laser emitted by the lidar in a single operation will create a reflected signal. In this case, the lidar will collect a reflected signal corresponding to the laser frequency, such as... Figure 1 , Figure 2 The signals in the middle and upper parts are shown. When there are many external objects (if there are multiple reflective surfaces), the laser emitted by the lidar at one time will form multiple reflected signals, and the lidar will collect multiple signal segments.

[0027] In the embodiments of the present invention, for example Figure 1 , Figure 2 The signal is a scanning signal of a single, simple object. Under normal circumstances, when a lidar with a lower or higher transmission frequency performs a radar scan of a single, simple object, the signal collected should be within the same frequency band as the transmission frequency (e.g., ...). Figure 1 (The upper and middle signal states). However, if the smaller and larger frequency lidars are located close to each other, the signals will mix, forming... Figure 1 The superposition of signals in the middle and lower parts.

[0028] In this case, such as Figure 2 As shown, if there is a multiple relationship between the frequencies of the various lidars, the collected signals will appear regular, making it impossible to separate the signals from lidars with lower and higher transmission frequencies. This will cause identification errors when lidars with lower and higher transmission frequencies are performing identification, complicating a simple situation and rendering them unusable.

[0029] However, in this embodiment of the invention, the frequencies of the various lidars do not have a multiple relationship, such as... Figure 1 As shown, the collected signals may appear irregular. In this case, a certain signal can be converted according to the actual frequency of the lidar. If other signals match this frequency, it indicates that they belong to the reflected signals of the lidar at that frequency. Therefore, this embodiment of the invention can decompose the lidar signal according to frequency, and then, by identifying the signals, accurately identify the object position by utilizing the characteristics of lidars with smaller and larger transmission frequencies.

[0030] Specifically, all of the lidars mentioned are single-photon area array lidars.

[0031] Specifically, the single-photon array lidar is a single-photon array flash lidar.

[0032] In particular, the multi-LiDAR system also includes a LiDAR signal analysis process:

[0033] S101. Determine the target radar's transmission frequency and set it as the standard transmission frequency;

[0034] S102. Extract the signal that conforms to the standard transmission frequency from the signal collected by the target radar. The extracted signal is the signal of the target radar.

[0035] Specifically, in step S102, the signal conforming to the standard transmission frequency is extracted from the signal collected by the target radar. The extracted signal, which is the signal of the target radar, includes:

[0036] S1021. Based on the absolute value of the standard transmission frequency n, divide the signal stream per unit time into n equal parts;

[0037] S1022. Analyze each equal portion of the signal stream to ensure that the signal appearing at the same position in the n equal portions of the signal stream is the signal of the target radar;

[0038] S1023. Subtract all signals other than the target radar signal from each equal signal stream, and merge the target radar signals from the n equal signal streams to obtain the target radar signal within that unit of time.

[0039] Specifically, the unit of time is 1 / 10 of a second.

[0040] Taking a 7MHz transmission frequency as an example, assuming 10 frames per second and a single frame of 1 / 10 second signal, the ranging results of 700,000 flashes are divided into 1000 parts. Assuming a ranging range of 20 meters, each part represents a distance of 2 centimeters. On average, each part will receive 700 measurements from its own radar. Another radar, due to a different transmission frequency (assuming 6.8MHz), will have its transmitted laser radar signal averaged across 1000 parts. This means that each receiving unit can accumulate a maximum of 1400 distance data measurements per part. If the effective signal threshold of a particular part exceeds 1400, for example, if the threshold is 3000, the data from the other radar is treated as noise. By analyzing the accumulated number of times each part of the signal is collected, if the accumulated number of times of a particular part exceeds the threshold, it indicates that the signal of that part at that location is a valid signal from the target radar. By subtracting other radar signals, the signals that meet the requirements are collected to obtain the target radar signal stream after noise subtraction.

[0041] The embodiments of the present invention can effectively deduct noise, avoid the accumulation and interference of other radar signals, and solve the interference problem between multiple radars by using the above method.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. An interference-resistant multi-lidar system, characterized in that, The multi-laser radar system includes two or more laser radars, each with a different transmission frequency; the ratio of the absolute value of the larger transmission frequency to the absolute value of the smaller transmission frequency in any two laser radars is not an integer; all laser radars are single-photon area array laser radars; the system also includes a laser radar signal analysis and extraction unit, used to perform the following processes: determining the transmission frequency of the target radar, set as a standard transmission frequency n; dividing the signal stream per unit time into n equal parts from the mixed signal collected by the target radar, based on the absolute value of the standard transmission frequency n; analyzing each equal part of the signal stream to ensure that the signal appearing at the same position in the n equal parts of the signal stream is the target radar signal; deducting other signals besides the target radar signal from each equal part of the signal stream, and merging the target radar signals in the n equal parts of the signal stream to obtain the target radar signal in that unit time; wherein, by analyzing the cumulative number of signals within each equal part and comparing it with a preset threshold, the effective signal of the target radar is identified.

2. The anti-interference multi-laser radar system according to claim 1, characterized in that, The unit of time is 1 / 10 of a second.

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