Ranging and speed measuring method and device of FMCW (Frequency Modulated Continuous Wave) laser radar

Abstract

The invention relates to the technical field of optical detection, in particular to an FMCW (Frequency Modulated Continuous Wave) laser radar distance and speed measurement method and device, which can be directly applied to actual products without calibrating time delay generated from frequency modulation signal generation to actual data generation hardware link, solves the influence caused by time delay in the current products, and improves the accuracy of the distance and speed measurement of the FMCW laser radar. According to the method, the nonlinear sampling data is eliminated, so that the sampling data at the rising or falling edge of the frequency modulation signal can be eliminated, and the accuracy of the FFT can be effectively improved to more accurately obtain the distance and speed of the target to be measured only by selecting the sampling data in the linear frequency sweeping interval, so that the performance and reliability of the FMCW laser radar are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and in particular to a ranging and velocity measurement method and apparatus for an FMCW lidar. Background Technology

[0002] Currently, there are two common detection methods for lidar: Time-of-Flight (TOF) and Frequency Modulated Continuous Wave (FMCW). While TOF has a relatively simple system structure, it suffers from blind spots and cannot measure targets at short distances. Furthermore, TOF is often used to detect target distance, making it difficult to simultaneously achieve accurate velocity measurement. FMCW lidar typically uses triangular wave linear frequency modulation (FM) to transmit a frequency-modulated signal. This FM signal is reflected from the object's surface, producing an echo signal. The frequency shift between the FM signal and the echo signal is proportional to the object's distance and velocity. The echo signal is mixed with the FM signal to generate a beat frequency signal. The upward and downward beat frequency signals are used to resolve the distance and velocity values. Additionally, FMCW lidar employs coherent balanced detection technology to avoid external interference from the environment or other lidar systems. Typically, Fast Fourier Transform (FFT) is the conventional signal processing method for obtaining the beat frequency signal.

[0003] During data sampling and processing, there is a time delay between the generation of the frequency-modulated signal and the actual data generation hardware link. FMCW lidar employs swept-frequency laser and coherent detection technology, using a frequency-modulated signal whose frequency changes periodically with time to combine the reflected light from the target with a local reference light in a photodetector. The received optical signal is converted into an electrical signal, and then undergoes a series of processing steps including amplification, filtering, mixing, and Fourier transform to obtain the final actual data used for analyzing target information (such as distance and velocity). Throughout this process, each hardware component spends time processing the signal, and the accumulation of this time causes the time delay between the generation of the frequency-modulated signal and the actual data generation hardware link.

[0004] When the echo signal returns to the receiver, due to time delay, it may be at different stages of the transmitted FM signal cycle. If the echo signal is on the rising or falling edge of the FM signal, its phase may experience a jump from rising to falling or from falling to rising. In the frequency domain, this phase jump causes a sudden change in frequency shift, which can be misinterpreted as a change in actual distance or velocity. This misinterpretation can lead to errors in distance and velocity calculations, affecting the accuracy of FMCW lidar in velocity and range measurement.

[0005] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to solve the problem of inaccurate frequency acquisition and the impact on the stability of FMCW lidar caused by the time delay between the generation of the frequency modulation signal and the actual data generation hardware link.

[0007] The present invention adopts the following technical solution:

[0008] Firstly, a ranging and velocity measurement method for FMCW lidar is provided, including:

[0009] The beat frequency signal of the FMCW lidar is sampled to obtain sampling data;

[0010] The sampled data is sliced ​​to obtain multiple intervals;

[0011] Obtain the beat frequency of each interval, and determine the frequency-stable linear sweep interval based on the beat frequency of each interval;

[0012] The sampled data within the linear frequency sweep interval is processed to obtain the velocity and distance of the target under test.

[0013] Preferably, the step of obtaining the beat frequency of each interval and determining the frequency-stable linear sweep interval based on the beat frequency of each interval includes:

[0014] Perform Fourier transform on the sampled data in each interval to obtain the beat frequency of the corresponding interval, and construct a spectrum based on the beat frequencies of all intervals.

[0015] Based on the spectrum, determine the nonlinear sweep frequency interval with frequency abrupt changes and the linear sweep frequency interval with stable frequency, and discard the sampled data within the nonlinear sweep frequency interval.

[0016] Preferably, the beat frequency signal is periodically distributed, with each period having a nonlinear sweep frequency interval;

[0017] The process of processing the sampled data within the linear frequency sweep interval to obtain the velocity and distance of the target includes:

[0018] All sampled data within the same period and within the linear frequency sweep interval preceding the nonlinear frequency sweep interval are integrated together to obtain rising edge sampled data;

[0019] All sampled data within the same period and within the linear frequency sweep interval following the nonlinear frequency sweep interval are integrated together to obtain the falling edge sampled data;

[0020] The rising edge sampling data and the falling edge sampling data are processed to obtain the velocity and distance of the target under test.

[0021] Preferably, the step of processing the rising edge sampling data and the falling edge sampling data to obtain the velocity and distance of the target to be measured includes: performing a Fourier transform on the rising edge sampling data and the falling edge sampling data to obtain the frequency information of the beat frequency signal;

[0022] Based on the frequency information, the speed and / or distance of the target to be measured are determined.

[0023] Preferably, the frequency information includes the difference in rising frequency between the frequency-modulated signal and the echo signal, and the difference in falling frequency between the echo signal and the frequency-modulated signal.

[0024] Preferably, the distance R of the target to be measured is calculated as follows:

[0025]

[0026] The velocity v of the target to be measured is calculated as follows:

[0027]

[0028] Among them, f b,up For the rise frequency difference, f b,down Let f be the frequency difference, λ be the laser sweep frequency, and λ = f c / t c , t c It refers to the rise and fall times of the laser sweep frequency, f c C is the sweep frequency of the sweep laser, and C is the speed of light.

[0029] Preferably, the step of slicing the sampled data to obtain multiple intervals includes:

[0030] Select sampling data within a period, and divide the sampling data within the same period into different intervals based on the total number of sampling data within a period and a preset interval.

[0031] Preferably, the range of the preset interval is 100 to 5000.

[0032] Secondly, a ranging and velocity measuring device for an FMCW lidar is provided, the ranging and velocity measuring device for the FMCW lidar includes: a processor and a memory for storing processor-executable instructions;

[0033] The processor is configured to execute the ranging and velocity measurement method of the FMCW lidar described in the first aspect.

[0034] Thirdly, a non-volatile computer storage medium is provided, the computer storage medium storing computer-executable instructions, which are executed by one or more processors to perform the ranging and velocity measurement method of the FMCW lidar described in the first aspect.

[0035] Fourthly, a ranging and velocity measuring device for an FMCW lidar is provided, used to implement the ranging and velocity measuring method of the FMCW lidar described in the first aspect, the device comprising:

[0036] At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the processor for performing the ranging and velocity measurement method of the FMCW lidar described in the first aspect.

[0037] Fifthly, a chip is provided, comprising: a processor and an interface for calling and running a computer program stored in a memory to execute the ranging and velocity measurement method of the FMCW lidar as described in the first aspect.

[0038] In a sixth aspect, a computer program product containing instructions is provided, which, when executed on a computer or processor, causes the computer or processor to perform the ranging and velocity measurement method of the FMCW lidar as described in the first aspect.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention eliminates the time delay caused by the hardware link between the frequency modulation signal generation and the actual data generation, allowing direct application in actual products. It solves the problem of time delay in current products and eliminates nonlinear sampling data. This allows sampling data at the rising or falling edge of the frequency modulation signal to be removed, and only sampling data within the linear frequency sweep interval is selected. This effectively improves the accuracy of FFT, enabling more accurate acquisition of the distance and velocity of the target under test, thereby effectively improving the performance and reliability of FMCW lidar. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a waveform diagram of a frequency modulation signal and an echo signal provided in an embodiment of the present invention;

[0043] Figure 2 This is a flowchart illustrating a ranging and velocity measurement method for an FMCW lidar provided in an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of sampling data of an FMCW lidar provided in an embodiment of the present invention;

[0045] Figure 4 This is a schematic flowchart illustrating a ranging and velocity measurement method for an FMCW lidar provided in an embodiment of the present invention.

[0046] Figure 5 This is a spectrum diagram of sampling data provided in an embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of performing Fourier transform on sampled data in intervals according to an embodiment of the present invention;

[0048] Figure 7 This is a flowchart illustrating the comparison of a ranging and velocity measurement method using an FMCW lidar provided in an embodiment of the present invention.

[0049] Figure 8 This is a schematic diagram of the ranging and velocity measuring device of an FMCW lidar provided in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0051] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0052] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0053] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0054] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] Example 1:

[0056] Frequency modulated continuous wave lidar is a new type of radar system that combines lidar with FMCW technology. It integrates technologies from multiple fields such as optics, mechanics, and electronics, and can achieve large-size, high-precision, blind-zone-free long-distance measurement with low power. It has broad application prospects in the field of high-resolution observation.

[0057] However, there is a time delay between the generation of the FM signal and the actual data generation hardware link, meaning the echo signal may be at different stages of the transmitted FM signal cycle. If it's at the rising or falling edge of a triangular wave, the echo signal's phase may experience a jump from rising to falling or from falling to rising. In the frequency domain, this phase jump causes a sudden change in frequency shift, which can be misinterpreted as a change in actual distance or velocity. This misinterpretation leads to errors in distance and velocity calculations, making it unsuitable for accurate calculations of the distance and velocity of the target.

[0058] like Figure 1The diagram shows the waveforms of the frequency modulation signal and the echo signal. To ensure measurement accuracy, the time-domain signal is continuous while the frequency-domain information changes abruptly within the time period td. Generally, the corresponding beat frequency signal needs to be discarded before performing a Fourier transform to determine the distance or velocity of the target.

[0059] To address the aforementioned issues, this embodiment proposes a ranging and velocity measurement method for an FMCW lidar, comprising: sampling the beat frequency signal of the FMCW lidar to obtain sampling data; slicing the sampling data to obtain multiple intervals; obtaining the beat frequency of each interval; determining a frequency-stable linear sweep frequency interval based on the beat frequency of each interval; and processing the sampling data within the linear sweep frequency interval to obtain the velocity and distance of the target.

[0060] A frequency-modulated (FM) signal is a signal whose frequency changes over time. The echo signal is the signal reflected back from the target after the FM signal reaches it. Multiplying the FM signal and the echo signal produces a new frequency component, which contains the difference between the original frequencies of the two signals. The beat frequency signal is obtained based on the difference between the original frequencies.

[0061] In this embodiment, the ranging and velocity measurement method of the FMCW lidar mainly includes: sampling the beat frequency signal to obtain a series of sampled data, which contains information about the continuous wave signal emitted from the lidar and reflected back to the sensor. The sampled data is then sliced, dividing the continuous data stream into multiple intervals. Each interval contains sampled data within a specific time or frequency range. Frequency analysis is performed on the sampled data within each interval to determine the beat frequency of the interval. The beat frequency refers to the frequency difference generated by modulation in the continuous wave signal. Finally, the beat frequency of each interval is analyzed to construct a corresponding spectrum diagram, and intervals with stable frequency changes and linear frequency sweeps on the spectrum diagram are identified as linear frequency sweep intervals. Further processing of the sampled data within the determined linear frequency sweep intervals allows for the calculation of the target's velocity using the Doppler effect principle. The velocity is related to the frequency change of the received signal; the greater the frequency change, the faster the velocity. Based on the principle of FMCW lidar, by comparing the frequency difference between the frequency-modulated signal and the echo signal, combined with the known wavelength and signal propagation time, the distance between the target and the lidar can be calculated. Finally, the processed speed and distance are output for subsequent applications such as navigation, obstacle avoidance, and monitoring.

[0062] The linear sweep frequency interval refers to the linear sweep frequency interval in the sampled data, while the interval with unstable beat frequency is referred to as the nonlinear sweep frequency interval (i.e., the time domain signal is continuous while the frequency domain information jumps). In order to improve accuracy, the sampled data in the nonlinear sweep frequency interval is discarded.

[0063] The following will describe each step of the method in detail. In one embodiment, such as... Figure 2 As shown, it includes:

[0064] Step 101: Sample the beat frequency signal of the FMCW lidar to obtain sampled data.

[0065] In one embodiment, a sampling frequency and sampling period are preset for the FMCW lidar; sampling data from the FMCW lidar is obtained based on the sampling frequency and the sampling period. The sampling frequency refers to the number of samples collected by the FMCW lidar per unit time, determining the density of data sampling. A higher sampling frequency yields more signal details, but also increases the burden on data processing and transmission. The sampling period refers to the time interval between two consecutive samples. The sampling period is the reciprocal of the sampling frequency, i.e., T = 1 / f, where T is the sampling period and f is the sampling frequency.

[0066] Based on a preset sampling frequency and sampling period, the FMCW lidar collects data once per sampling period. For example, in one embodiment, such as Figure 3 As shown, when the sampling frequency is 1.25 G / s and the sampling period is 100 μs, there will be 125,000 consecutive sampled data points in one period. Based on the above sampled data, in... Figure 3 In the graph, the horizontal axis represents time, and the vertical axis represents amplitude.

[0067] Step 102: Slice the sampled data to obtain multiple intervals.

[0068] In one embodiment, sampling data within a period is selected, and the sampling data within the same period is divided into different intervals according to the total number of sampling data within a period and a preset interval, wherein the preset interval can range from 100 to 5000.

[0069] Based on the total number of sampled data points within a period and a preset interval, the sampled data within that period is divided into several smaller intervals. For example, as mentioned above, when the sampling frequency is 1.25 G / s and the sampling period is 100 μs, there will be 125,000 consecutive sampled data points in one period. Setting the preset interval to 5,000, the 1000th to 6000th sampled data points can be selected as the first interval, the 2000th to 7000th sampled data points as the second interval, and so on, until all 125,000 sampled data points are assigned to their respective intervals.

[0070] It is worth noting that the preset interval can range from 100 to 5000. This means that each interval can consist of 100 samples, 5000 samples, or any integer number of samples between 100 and 5000 as a period. If the preset interval is less than 100, it may lead to excessive computational costs later on, while a preset interval greater than 5000 may result in insufficient accuracy, failing to meet practical requirements. In other words, smaller intervals result in higher accuracy but also higher computational costs; larger intervals result in lower accuracy but lower computational costs. The specific interval can be selected based on actual accuracy requirements and computational costs.

[0071] Step 103: Obtain the beat frequency of each interval, and determine the frequency-stable linear sweep interval based on the beat frequency of each interval.

[0072] In one embodiment, such as Figure 4 As shown, step 103 specifically includes:

[0073] Step 1031: Perform Fourier transform on the sampled data in each interval to obtain the beat frequency of the corresponding interval, and construct a spectrum diagram based on the beat frequencies of all intervals.

[0074] like Figure 5 As shown, a Fourier transform is performed on the sampled data in each interval to obtain the beat frequency corresponding to each sampled data in each interval. Based on the beat frequency, a corresponding spectrum is constructed, which shows the components of the signal at different frequencies and their corresponding amplitudes.

[0075] In one embodiment, in Figure 5 In the diagram, the horizontal axis represents the interval, and the vertical axis represents the beat frequency of that interval. Taking an interval of 5000 samples as an example, the horizontal axis 1 represents that the beat frequency obtained from the 1000th to the 6000th sample is 7MHz, and 2 represents that the beat frequency obtained from the 2000th to the 7000th sample is 7MHz.

[0076] Step 1032: Based on the spectrum diagram, determine the nonlinear sweep frequency interval with frequency abrupt changes and the linear sweep frequency interval with stable frequency, and discard the sampled data within the nonlinear sweep frequency interval.

[0077] In the frequency spectrum, intervals with stable beat frequencies are identified as linear sweep intervals, while intervals with unstable frequencies are nonlinear sweep intervals. The selection criteria for stable frequencies can be determined based on frequency stability, amplitude, and the presence of significant jumps or drifts. For example, following the previous example, the beat frequency obtained by performing a Fourier transform on the 1000th to 6000th sample data is f1, the beat frequencies obtained by performing Fourier transforms on the 2000th to 7000th and 3000th to 8000th sample data are also f1, and so on until the frequency obtained by performing a Fourier transform on the Nth to N+5000th sample data is f2. Therefore, the interval with beat frequency f1 is a linear sweep interval, and the interval with beat frequency f2 is a nonlinear sweep interval.

[0078] like Figure 6 As shown, f1 can be 7MHz, and f2 can be 8MHz. The beat frequency at the periodic inflection point is 8MHz, and 7MHz is the stable point of the beat frequency. In the spectrum diagram, the inflection point usually refers to the place where the frequency components change, that is, the region where the frequency sweep is nonlinear, which is the region where the time domain signal is continuous but the frequency domain information jumps as mentioned above.

[0079] In one embodiment, such as Figure 6 As shown, according to the specific implementation process of the aforementioned steps, the beat frequency after Fourier transform of all intervals between the 1000th and Nth sampled data is 7MHz. The beat frequency at the corresponding inflection point between N and N+5000 is 8MHz. Therefore, the data of N to N+5000 points in the sampled data is a non-linear sweep interval. It is necessary to discard the data of N to N+5000 points in the sampled data of the beat frequency signal, and integrate all the sampled data in the linear sweep interval that is in the same period and before the non-linear sweep interval to obtain the rising edge sampled data (i.e., the 10th). The sampling data is obtained by combining all the sampling data from the Nth sampling data point to the Nth sampling data point. Then, all the sampling data within the same period and within the linear frequency sweep interval after the nonlinear frequency sweep interval are integrated together to obtain the falling edge sampling data (i.e., all the sampling data after the N+5000th sampling data point within the same period). The rising edge and falling edge sampling data are then integrated before performing a Fourier transform to obtain the distance and velocity of the target. This effectively discards the sampling data within the nonlinear frequency sweep interval, making the final Fourier transform more accurate and thus improving the accuracy and reliability of the FMCW lidar measurement results.

[0080] Step 104: Process the sampled data within the linear frequency sweep interval to obtain the velocity and distance of the target under test.

[0081] exist Figure 5The sampling data corresponding to 7MHz was found. Figure 3 The starting point of the stable frequency band is determined by selecting the entire segment of data from that segment as the starting point for the FFT analysis. Once the starting point is identified, the sampled data corresponding to that point is used as the starting point for the FMCW lidar sampling data. After determining the starting point for the FFT analysis, a Fourier transform can be performed on this entire segment of data to obtain the spectral distribution of the entire signal. This starting point can then be used for subsequent distance and velocity calculations, improving the accuracy and reliability of the measurement.

[0082] In one embodiment, the beat frequency signal is periodically distributed, with each period having a nonlinear sweep frequency interval. Step 104 specifically includes: integrating all sampled data within the same period and the linear sweep frequency interval preceding the nonlinear sweep frequency interval to obtain rising edge sampled data; integrating all sampled data within the same period and the linear sweep frequency interval following the nonlinear sweep frequency interval to obtain falling edge sampled data; and processing the rising edge sampled data and the falling edge sampled data to obtain the velocity and distance of the target. Rising edge sampled data refers to sampled data when the frequency changes from low to high. All sampled data within the same period and preceding the nonlinear sweep frequency interval are integrated together. Falling edge sampled data refers to sampled data when the frequency changes from high to low. All sampled data within the same period and following the nonlinear sweep frequency interval are integrated together.

[0083] FMCW lidar uses a frequency-modulated signal with a frequency that changes periodically over time. The echo signal from the target is combined with a local reference light in a photodetector, converting the round-trip distance into frequency. In one embodiment, after obtaining an accurate beat frequency signal using this method, signal processing is performed on the integrated rising and falling edge sampling data. In one embodiment, a Fourier transform can be performed on the rising and falling edge sampling data to obtain the frequency information of the beat frequency signal; based on the frequency information, the velocity and / or distance of the target are determined. The frequency information includes the difference in rising frequency between the frequency-modulated signal and the echo signal, and the difference in falling frequency between the echo signal and the frequency-modulated signal. Because the frequency of the frequency-modulated signal changes linearly with time, a frequency difference is generated between the frequency-modulated signal and the reflected echo signal. This frequency difference is due to the time it takes for light to travel to the target and return to the FMCW lidar. For example, if the target is far from the FMCW lidar, the round-trip time of the laser will be longer, resulting in more frequency changes in the frequency-modulated signal during this time, and thus a larger frequency difference between the frequency-modulated signal and the echo signal. Conversely, if the target is close to the FMCW lidar, the round-trip time is shorter, and the frequency difference between the frequency-modulated signal and the echo signal is smaller. By accurately measuring the corresponding frequency difference and utilizing the fixed mathematical relationship between the speed of light and the frequency difference, the distance between the target and the FMCW lidar can be accurately calculated.

[0084] Specifically, the distance R of the target to be measured is calculated as follows:

[0085]

[0086] The echo signal received by the FMCW lidar contains not only the frequency difference between the measured target and the frequency-modulated signal due to the distance to the target, but also an additional frequency offset caused by the target's motion. The velocity measurement of the target is primarily based on this additional frequency offset caused by motion, because there is a fixed physical relationship between this additional frequency offset and the target's velocity. By accurately measuring the magnitude and direction of this additional frequency offset (the direction reflects whether the target is approaching or moving away from the lidar), the velocity of the target relative to the FMCW lidar can be accurately calculated. For example, if the measured additional frequency offset is positive and large, it indicates that the target is rapidly moving towards the lidar; if it is negative and large in absolute value, it indicates that the target is rapidly moving away from the lidar.

[0087] Specifically, the velocity v of the target to be measured is calculated as follows:

[0088]

[0089] Among them, f b,up For the rise frequency difference, f b,down Let f be the frequency difference, λ be the laser sweep frequency, and λ = f c / t c , t c It refers to the rise and fall times of the laser sweep frequency, f c C is the sweep frequency of the sweep laser, and C is the speed of light.

[0090] In one embodiment, such as Figure 7 The figures show the waveforms of data after Fourier transform processing using the ranging and velocities measurement method proposed in this embodiment for FMCW lidar, and the waveforms of data directly subjected to Fourier transform without this method. The horizontal axis represents the frequency after Fourier transform, and the vertical axis represents the amplitude (mW) corresponding to the frequency after Fourier transform. Differences in peak frequencies can affect the calculation of speed and distance. This process ensures that the starting point for FFT analysis of the sampled data is a position where the beat frequency is stable, improving the accuracy and reliability of subsequent spectrum analysis. In practical applications, this method can help FMCW lidar better handle complex signal environments, improving system performance and measurement accuracy.

[0091] In summary, this invention eliminates the time delay caused by the hardware link between the frequency modulation signal generation and the actual data generation, allowing direct application in actual products. It solves the problem of time delay in current products and eliminates nonlinear sampling data. This allows sampling data at the rising or falling edge of the frequency modulation signal to be removed, and by selecting only sampling data within the linear frequency sweep interval, the accuracy of FFT can be effectively improved to more accurately obtain the distance and velocity of the target under test, thereby effectively improving the performance and reliability of FMCW lidar.

[0092] Example 2:

[0093] In Embodiment 1, a ranging and velocity measurement method for an FMCW lidar was provided. In this embodiment, a ranging and velocity measurement device for an FMCW lidar will be proposed. The ranging and velocity measurement device for the FMCW lidar includes: a processor and a memory for storing processor-executable instructions; wherein, the processor is configured to execute the ranging and velocity measurement method for the FMCW lidar described in Embodiment 1.

[0094] like Figure 8 As shown, the ranging and velocity measuring device of the FMCW lidar includes a processor 21 and a memory 22, wherein the processor 21 and the memory 22 can be connected by a bus or other means.

[0095] Processor 21 can be a Central Processing Unit (CPU). Processor 21 can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations of the above types of chips.

[0096] The memory 22, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the ranging and velocity measurement method of the FMCW lidar in Embodiment 1 of this invention. The processor executes various functional applications and training processes by running the non-transitory software programs, instructions, and modules stored in the memory.

[0097] The memory 22 may include a program storage area and a training storage area. The program storage area may store the operating system and applications required for at least one function; the training storage area may store training data created by the processor. Furthermore, the memory may include high-speed random access memory and non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 22 may optionally include memory remotely located relative to the processor, which can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0098] The one or more modules are stored in the memory 22, and when executed by the processor 21, they perform the following: Figure 1 The ranging and velocity measurement method of the FMCW lidar in Example 1 is shown.

[0099] For specific details regarding the ranging and velocity measurement methods of the aforementioned FMCW lidar, please refer to the relevant documentation. Figure 1 , Figure 2 and Figure 3 The relevant descriptions and effects in the embodiments shown are for reference only and will not be repeated here.

[0100] This embodiment also provides a non-volatile computer storage medium storing computer-executable instructions, which are executed by one or more processors to perform the ranging and velocity measurement method of the FMCW lidar described in Embodiment 1.

[0101] The computer storage medium stores computer-executable instructions that can execute the ranging and velocity measurement methods of the FMCW lidar in any of the above method embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium may also include combinations of the above types of memory.

[0102] For the specific steps of the ranging and velocity measurement method of the FMCW lidar, please refer to Example 1, which will not be repeated in this example.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ranging and velocity measurement method for an FMCW lidar, characterized in that, include: The beat frequency signal of the FMCW lidar is sampled to obtain sampling data; The sampled data is sliced ​​to obtain multiple intervals; Obtain the beat frequency of each interval, and determine the frequency-stable linear sweep interval based on the beat frequency of each interval; The sampled data within the linear frequency sweep interval is processed to obtain the velocity and distance of the target under test.

2. The ranging and velocity measurement method for FMCW lidar according to claim 1, characterized in that, The process of obtaining the beat frequency of each interval and determining the frequency-stable linear sweep interval based on the beat frequency of each interval includes: Perform Fourier transform on the sampled data in each interval to obtain the beat frequency of the corresponding interval, and construct a spectrum based on the beat frequencies of all intervals. Based on the spectrum, determine the nonlinear sweep frequency interval with frequency abrupt changes and the linear sweep frequency interval with stable frequency, and discard the sampled data within the nonlinear sweep frequency interval.

3. The ranging and velocity measurement method for FMCW lidar according to claim 2, characterized in that, The beat frequency signal is periodically distributed, with each period having a non-linear sweep frequency interval; The process of processing the sampled data within the linear frequency sweep interval to obtain the velocity and distance of the target includes: All sampled data within the same period and within the linear frequency sweep interval preceding the nonlinear frequency sweep interval are integrated together to obtain rising edge sampled data; All sampled data within the same period and within the linear frequency sweep interval following the nonlinear frequency sweep interval are integrated together to obtain the falling edge sampled data; The rising edge sampling data and the falling edge sampling data are processed to obtain the velocity and distance of the target under test.

4. The ranging and velocity measurement method for FMCW lidar according to claim 3, characterized in that, The process of processing the rising edge sampling data and the falling edge sampling data to obtain the velocity and distance of the target includes: Perform Fourier transform on the rising edge sampled data and the falling edge sampled data to obtain the frequency information of the beat frequency signal; Based on the frequency information, the speed and / or distance of the target to be measured are determined.

5. The ranging and velocity measurement method for FMCW lidar according to claim 4, characterized in that, The frequency information includes the difference in rising frequency between the frequency-modulated signal and the echo signal, and the difference in falling frequency between the echo signal and the frequency-modulated signal.

6. The ranging and velocity measurement method for FMCW lidar according to claim 5, characterized in that, The distance R to the target to be measured is calculated as follows: The velocity v of the target to be measured is calculated as follows: Among them, f b,up For the rise frequency difference, f b,down Let f be the frequency difference, λ be the laser sweep frequency, and λ = f c / t c , t c It refers to the rise and fall times of the laser sweep frequency, f c C is the sweep frequency of the sweep laser, and C is the speed of light.

7. The ranging and velocity measurement method for FMCW lidar according to claim 1, characterized in that, The step of slicing the sampled data to obtain multiple intervals includes: Select sampling data within a period, and divide the sampling data within the same period into different intervals based on the total number of sampling data within a period and a preset interval.

8. The ranging and velocity measurement method for FMCW lidar according to claim 7, characterized in that, The preset interval range is 100 to 5000.

9. A ranging and velocity measuring device for an FMCW lidar, characterized in that, The ranging and velocity measuring device of the FMCW lidar includes: a processor and a memory for storing processor-executable instructions; The processor is configured to execute the ranging and velocity measurement method of the FMCW lidar according to any one of claims 1-8.

10. A non-volatile computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, which are executed by one or more processors to perform the ranging and velocity measurement method of the FMCW lidar according to any one of claims 1-8.

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