CN-121995385-A - Distance and speed measuring method and device of FMCW laser radar

Abstract

The invention relates to the technical field of optical detection, in particular to a distance and speed measuring method and device of an FMCW laser radar, which can be directly applied to actual products without calibrating time delay generated by generating a hardware link from a frequency modulation signal to actual data, solve the influence caused by the time delay in the current products, and reject nonlinear sampling data, so that the sampling data at the rising or falling edge of the frequency modulation signal can be rejected, and the accuracy of FFT (fast Fourier transform) can be effectively improved only by selecting the sampling data of a linear sweep frequency interval so as to more accurately acquire the distance and speed of a target to be detected, thereby effectively improving the performance and reliability of the FMCW laser radar.

Inventors

• ZHAO LE
• CHEN HONGGANG
• ZHANG BO
• LUO YONG

Assignees

• 武汉光迅科技股份有限公司

Dates

Publication Date

20260508

Application Date

20241104

Claims (10)

1. 1. The ranging and speed measuring method of the FMCW laser radar is characterized by comprising the following steps: Sampling the beat frequency signal of the FMCW laser radar to obtain sampling data; Slicing the sampled data to obtain a plurality of intervals; acquiring beat frequency of each interval, and determining a linear sweep frequency interval with stable frequency according to the beat frequency of each interval; And processing the sampling data in the linear sweep frequency interval to obtain the speed and the distance of the target to be measured.
2. 2. The method for ranging and measuring speed of FMCW lidar according to claim 1, wherein the obtaining the beat frequency of each section and determining a frequency-stable linear sweep section according to the beat frequency of each section includes: carrying out Fourier transform on the sampling data in each interval to obtain beat frequencies of the corresponding interval, and constructing a spectrogram according to the beat frequencies of all the intervals; and determining a nonlinear sweep frequency interval with abrupt frequency change and a linear sweep frequency interval with stable frequency according to the spectrogram, and discarding sampling data in the nonlinear sweep frequency interval.
3. 3. The method for measuring the distance and speed of the FMCW lidar according to claim 2, wherein the beat signal is distributed periodically, each period having a nonlinear sweep interval; the processing the sampling data in the linear sweep frequency interval to obtain the speed and the distance of the target to be measured comprises the following steps: integrating all sampling data in a linear sweep interval which is positioned in the same period and in front of a nonlinear sweep interval to obtain rising edge sampling data; Integrating all sampling data in a linear sweep interval which is positioned in the same period and behind a nonlinear sweep interval to obtain falling edge sampling data; and processing the rising edge sampling data and the falling edge sampling data to obtain the speed and the distance of the target to be detected.
4. 4. The method for ranging and measuring speed of FMCW lidar according to claim 3, wherein the processing the rising edge sampling data and the falling edge sampling data to obtain the speed and distance of the target to be measured includes: Performing Fourier transformation on the rising edge sampling data and the falling edge sampling data to obtain frequency information of a beat frequency signal; and determining the speed and/or distance of the target to be detected according to the frequency information.
5. 5. The method of claim 4, wherein the frequency information includes a rising frequency difference between a frequency modulated signal and an echo signal and a falling frequency difference between the echo signal and the frequency modulated signal.
6. 6. The method for measuring distance and speed of FMCW lidar according to claim 5, wherein the calculating manner of the distance R of the target to be measured is: the speed v of the target to be measured is calculated in the following manner: Wherein f b,up is the rising frequency difference, f b,down is the falling frequency difference, λ is the laser sweep frequency, λ=f c /t c ,t c is the laser sweep rise and fall time, f c is the sweep laser sweep frequency, and C is the light velocity.
7. 7. The method for ranging and measuring speed of FMCW lidar according to claim 1, wherein slicing the sampled data to obtain a plurality of intervals includes: Sampling data in one period is selected, and the sampling data in the same period is divided into different intervals according to the total number of the sampling data in one period and a preset interval.
8. 8. The ranging and speed measuring method of the FMCW lidar according to claim 7, wherein the preset interval is 100-5000.
9. 9. The ranging and speed measuring device of the FMCW laser radar is characterized by comprising a processor and a memory for storing instructions executable by the processor; Wherein the processor is configured to perform the ranging and speed measurement method of the FMCW lidar of any of claims 1-8.
10. 10. A non-transitory computer storage medium storing computer executable instructions for execution by one or more processors for performing the ranging and speed measurement method of the FMCW lidar of any of claims 1-8.

Description

Distance and speed measuring method and device of FMCW laser radar Technical Field The invention relates to the technical field of optical detection, in particular to a distance and speed measuring method and device of an FMCW laser radar. Background There are two common detection methods for lidar, the Time of Flight (TOF) method and the frequency modulated continuous wave (Frequency Modulated Continuous Wave, FMCW) method. TOF is relatively simple in system structure, but cannot measure a target within a short distance due to the existence of blind spots, and furthermore, TOF is often used to detect the distance of a target, so that it is difficult to simultaneously achieve accurate speed measurement. FMCW lidars typically employ triangular wave chirping to transmit a frequency modulated signal that is reflected off of the object surface to obtain an echo signal, with the frequency shift between the frequency modulated signal and the echo signal being proportional to the distance and speed of the object. And the beat frequency signal generated after the echo signal and the frequency modulation signal are mixed is used for analyzing the distance and the speed value according to the upward and downward beat frequency signals. In addition, the FMCW lidar adopts a coherent balance detection technique, which can avoid external interference from the environment or other lidars. In general, a fast fourier transform (Fast Fourier Transform, abbreviated FFT) is a conventional signal processing method to obtain a beat signal. During data sampling and processing, there is a delay in the hardware link due to the occurrence of the fm signal to the actual data. The FMCW laser radar adopts sweep laser and coherent detection technology, adopts frequency modulation signals with the frequency periodically changing along with time, and combines reflected light from a target with local reference light in a photoelectric detector. The received optical signal is converted into an electrical signal, and then a series of processing procedures such as amplification, filtering, mixing, fourier transformation and the like of the electrical signal are performed to obtain actual data which is finally used for analyzing target information (such as distance, speed and the like). During the whole process, each hardware component spends a certain time on processing the signal, and the accumulation of these times causes a delay from the occurrence of the frequency modulated signal to the actual generation of the hardware link. When the echo signal returns to the receiving end, the echo signal may be at different phases of the period of the transmitted fm signal due to the time delay. If the echo signal is on the rising or falling edge of the fm signal, the phase of the echo signal may experience a jump from rising to falling or from falling to rising. In the frequency domain, such a phase jump may lead to a sudden change of the frequency shift, which may be misinterpreted as an actual distance or speed change. This misinterpretation can lead to errors in the calculation of distance and speed, affecting the accuracy of FMCW lidar speed and range. In view of this, overcoming the drawbacks of the prior art is a problem to be solved in the art. Disclosure of Invention The invention aims to solve the technical problem of influencing the stability of the FMCW laser radar due to inaccurate obtained frequency caused by time delay of a hardware link from the generation of a frequency modulation signal to the generation of actual data. The invention adopts the following technical scheme: in a first aspect, a ranging and speed measuring method of an FMCW lidar is provided, including: Sampling the beat frequency signal of the FMCW laser radar to obtain sampling data; Slicing the sampled data to obtain a plurality of intervals; acquiring beat frequency of each interval, and determining a linear sweep frequency interval with stable frequency according to the beat frequency of each interval; And processing the sampling data in the linear sweep frequency interval to obtain the speed and the distance of the target to be measured. Preferably, the obtaining the beat frequency of each interval, and determining the linear sweep interval with stable frequency according to the beat frequency of each interval includes: carrying out Fourier transform on the sampling data in each interval to obtain beat frequencies of the corresponding interval, and constructing a spectrogram according to the beat frequencies of all the intervals; and determining a nonlinear sweep frequency interval with abrupt frequency change and a linear sweep frequency interval with stable frequency according to the spectrogram, and discarding sampling data in the nonlinear sweep frequency interval. Preferably, the beat frequency signals are distributed periodically, and each period has a nonlinear sweep frequency interval; the processing the sampling data in the linear sweep frequency interva