A novel high-precision laser ranging method and system using a time-delay phase-locked loop

Abstract

The present invention belongs to the technical field of laser ranging and discloses a novel high-precision laser ranging method and system using a delay phase-locked loop. The method comprises generating two identical m-sequence signals, one signal being transmitted to a laser and the other signal being sent to a matched filter; the laser signal being reflected by a target to be measured, received by a detector, converted into an electrical signal, and transmitted to the matched filter as an echo signal; the echo signal being matched filtered, and a coarse measurement result of the matched filtering being sent to a novel delay phase-locked loop using a sinc function as a model; a peak value of the original result and four points near the peak value being used to perform function fitting on the sinc function model, and a more accurate peak coordinate being obtained by solving the solution, i.e., a precisely measured distance value. The method can significantly improve ranging accuracy by only data processing without changing the hardware and structure of the original system.

Description

Technical Field

[0001] The present invention relates to the technical field of laser ranging, and more particularly to a novel delay phase-locked loop (DPLL) high-precision laser ranging method and system. More particularly, the invention relates to a novel delay phase-locked loop (DPLL) modeled on a sinc function, which further processes a pseudo-code ranging result to improve the ranging accuracy of the ranging system. Background Art

[0002] LiDAR uses highly directional, energy-concentrated lasers as its detection medium. Compared to microwave radar, LiDAR offers higher detection sensitivity and measurement resolution, greater anti-interference and stealth, and a smaller size and weight. Compared to other passive optoelectronic radars, LiDAR offers greater environmental adaptability and provides more detection information. Traditional laser ranging methods, such as pulse, phase, triangulation, and coherence, do not adequately meet the requirements of autonomous driving. The pulse method is generally used for range measurements exceeding kilometers, but its data update rate is inconsistent with the range. The phase method is generally used for high precision over short distances, but accuracy decreases over longer distances, and the data update rate is also low. The triangulation method can achieve ranging accuracy up to micrometers, but this decreases sharply with increasing distance. The coherence method offers high data update rates and high precision, but it places high demands on lasers, detectors, and information processing components, resulting in complex and costly systems.

[0003] Pseudo-code modulated laser ranging uses pseudo-random code to modulate the laser and matched filter decoding, which has a high signal-to-noise ratio and data update rate. It can not only reduce the power requirements for the emitted laser, but also solve the contradiction between long-range and fast ranging. In addition, pseudo-code modulation only modulates the power of the laser, which reduces the requirements for the laser, detectors and other optical antennas. It has a high cost-effectiveness and is very suitable for the requirements of lidar, autonomous driving, drone navigation and other fields. However, pseudo-code ranging is subject to the laser modulation frequency and data sampling frequency, and the accuracy is not high, which cannot meet the requirements of imaging and navigation. Some existing research improves the ranging accuracy by combining pseudo-code modulation with coherent detection, but doing so will inevitably increase the complexity and cost of the system. Another part of the research improves the accuracy through data processing, including various peak-finding algorithms, delay phase-locked loops, etc., but the accuracy needs to be further improved. Summary of the Invention

[0004] In response to the defects of the existing technology or the need for improvement, the present invention provides a new high-precision laser ranging method and system with a delay phase-locked loop, thereby solving the technical problem of low accuracy of pseudo-code laser ranging.

[0005] To achieve the above object, according to one aspect of the present invention, a novel delay phase-locked loop high-precision laser ranging method is provided, comprising the following steps:

[0006] S1: Generates two identical m-sequence signals. One signal is transmitted to the laser to modulate the laser signal, and the other signal is sent to the matched filter as a reference signal for subsequent distance calculation.

[0007] S2: The laser signal obtained in step S1 is reflected by the target, received by the detector and converted into an electrical signal, which is then transmitted to the matched filter as an echo signal for distance calculation;

[0008] S3: performing matched filtering on the reference signal obtained in step S1 and the echo signal obtained in step S2 to obtain a rough measurement result of the matched filtering;

[0009] S4: sending the coarse measurement result obtained in step S3 to a new delay-locked loop based on the sinc function as a model, calculating the initial values ​​of the sinc function parameters, and continuing to fit the model function to obtain a more accurate fine measurement result;

[0010] S5: Add the rough measurement result obtained in step S3 and the fine measurement result obtained in step S4 to obtain a final measurement result.

[0011] Preferably, the sequence signal in step S1 is an m-sequence signal. When the m-sequence is logic "1", the laser emits full-power laser; when the m-sequence is logic "0", the laser does not emit laser, which is used to modulate the laser signal amplitude.

[0012] Preferably, the matched filtering result in step S3 includes the peak point and four points on its left and right.

[0013] Preferably, the peak point in step S3 is (τ, P), where P is the peak value of the matched filtering result, and τ is the horizontal coordinate of the peak value of the matched filtering result.

[0014] Preferably, the calculation formula of the rough measurement result d1 in step S3 is:

[0015]

[0016] Where c is the speed of light.

[0017] Preferably, the four points on the left and right of the peak point in step S3 are (-2d, E2), (-d, E1), (d, L1), and (2d, L2), respectively, where E1 is the point on the left side of the peak P of the matched filtering result, E2 is the point on the left side of the matched filtering result E1, L1 is the point on the right side of the peak P of the matched filtering result, L2 is the point on the right side of the matched filtering result L1, and d is the interval between the two points in the matched filtering result.

[0018] Preferably, the sinc function calculation formula in step S4 is:

[0019] f(x)=a0sinc(a1x+a2)

[0020]

[0021] Wherein, a0, a1, and a2 are parameters of the sinc function, P, E1, E2, L1, and L2 are five point values ​​of the matched filtering rough measurement result obtained in step S3, and d is the interval between two points of the matched filtering result obtained in step S3.

[0022] Preferably, the calculation formula for the precise measurement result d2 in step S4 is:

[0023]

[0024] Where c is the speed of light.

[0025] Preferably, the method further includes step S6, changing the distance between the measurement target and the ranging system, re-executing steps S1 to S5, calculating the ranging result of the new distance and recording the ranging error.

[0026] To achieve the above objectives, according to another aspect of the present invention, a novel delay phase-locked loop high-precision laser ranging system is provided, which adopts the above novel delay phase-locked loop high-precision laser ranging method, including a signal generation module, a laser emission module, a detector module and a signal processing module, wherein the signal processing module includes a matched filter and a delay phase-locked loop;

[0027] The signal generation module generates two m-sequence modulation signals, one of which is transmitted to the laser to modulate the laser signal, and the other is sent to the matched filter as a reference signal for subsequent distance calculation;

[0028] The laser emission module receives the modulation signal and emits the modulated laser signal toward the measurement target;

[0029] The laser signal is reflected by the detection target, received and converted by the detector module, and sent to the signal processing module as an echo signal;

[0030] The signal processing module performs matched filtering processing on the reference signal of the signal generation module and the echo signal of the detector module, and obtains the final ranging result and outputs it.

[0031] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0032] (1) Based on the original ranging results, the present invention introduces a new delay phase-locked loop based on the sinc function model. The sinc function model is fitted with the peak value of the original result and four points near the peak value to obtain a more accurate peak coordinate, which is the precise distance value. This method can significantly improve the ranging accuracy through data processing without changing the original system hardware and structure.

[0033] (2) The present invention has a very high system signal-to-noise ratio and can significantly reduce the laser power within the same measurement range.

[0034] (3) While ensuring the ranging performance index, the present invention reduces the requirements for the system and significantly improves the cost performance of the system.

[0035] (4) The present invention significantly improves the ranging accuracy without changing the system hardware and structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of a new type of high-precision laser ranging method using a time-delay phase-locked loop;

[0037] Figure 2 This is a new delay phase-locked loop high-precision laser ranging method and system delay phase-locked loop working diagram;

[0038] Figure 3 This is a new type of high-precision laser ranging method and system with a delayed phase-locked loop.

[0039] Figure 4 This is a graph showing the ranging error results of a new type of high-precision laser ranging method and system using a time-delay phase-locked loop. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] The present invention provides a new type of delay phase-locked loop high-precision laser ranging system, please refer to Figure 1The system mainly includes a signal generation module, a laser emission module, a detector module, and a signal processing module. The signal processing module includes a matched filter and a delay-locked loop. The signal generation module generates two m-sequence modulation signals. One signal is transmitted to the laser to modulate the laser signal, and the other signal is sent to the matched filter as a reference signal for subsequent distance calculation. The laser emission module receives the modulation signal and transmits the modulated laser signal to the measurement target. The laser signal is reflected by the detection target, received and converted by the detector module, and sent to the signal processing module as an echo signal. The signal processing module performs matched filtering and matched filter processing on the reference signal of the signal generation module and the echo signal of the detector module to obtain the final ranging result and output it.

[0042] The present invention provides a novel delay phase-locked loop high-precision laser ranging method, comprising the following steps:

[0043] Step S1: Generate two identical m-sequence signals. One signal is transmitted to the laser to modulate the laser signal amplitude. When the m-sequence is a logical "1," the laser emits full power; when the m-sequence is a logical "0," the laser does not emit. The other signal is sent to a matched filter as a reference signal for subsequent distance calculation.

[0044] Step S2: The laser signal obtained in step S1 is reflected by the target, received by the detector, converted into an electrical signal, and transmitted to the matched filter as an echo signal for distance calculation.

[0045] Step S3: performing matched filtering on the reference signal obtained in step S1 and the echo signal obtained in step S2 by a matched filter to obtain a rough measurement result of the matched filtering;

[0046] The matched filtering results include the peak point and the four points on its left and right. The peak point is (τ, P), and the four points on the left and right of the peak point are (-2d, E2), (-d, E1), (d, L1), and (2d, L2), where P is the peak value of the matched filtering result, τ is the horizontal coordinate of the peak value of the matched filtering result, E1 is the point on the left side of the peak value P of the matched filtering result, E2 is the point on the left side of the matched filtering result E1, L1 is the point on the right side of the peak value P of the matched filtering result, L2 is the point on the right side of the matched filtering result L1, and d is the interval between two points in the matched filtering result.

[0047] Matched filtering results refer to Figure 3, where P is the peak value of the matched filtering result 913307883, E1 is the point 796572081 on the left side of the peak value P of the matched filtering result, E2 is the point 869779238 on the left side of the matched filtering result E1, L1 is the point 912473586 on the right side of the peak value P of the matched filtering result, L2 is the point 848076615 on the right side of the matched filtering result L1, and d is the interval between two points in the matched filtering result 1×10 -9 , τ is the peak horizontal coordinate of the matched filtering result 51×10 -9 , take the speed of light c=3×10 8 m / s, that is, the calculation formula for the rough distance d1 is:

[0048]

[0049] Step S4: sending the coarse measurement result obtained in step S3 to a new delay-locked loop with a sinc function as a model, calculating the initial values ​​of the sinc function parameters, and continuing to fit the model function to obtain a more accurate fine measurement result;

[0050] For details, please refer to the workflow of the new delay-locked loop modeled on the sinc function. Figure 2 , the model function is,

[0051] f(x)=a0sinc(a1x+a2) (2)

[0052] Among them, a0, a1, and a2 are the parameters of the sinc function;

[0053] Substitute the five points of the matched filtering results into the formula to calculate the initial value of the function parameter.

[0054]

[0055] Where P, E1, E2, L1, and L2 are the five point values ​​of the matched filtering results obtained by S3, and d is the interval between two points of the matched filtering results obtained by S3. The calculation results of the above formula are the initial values ​​of the function parameters. The model function is fitted through five points to obtain more accurate function parameters a0 of 916622094, a1 of 0.1255, and a2 of -0.0408. The speed of light c is taken as 3×10 8 m / s, that is, the precise distance measurement result of the delay phase-locked loop is d2, and the calculation formula is:

[0056]

[0057] Step S5: Add the rough measurement result and the fine measurement result, 7650+48.76=7698.76 mm, which is the final measurement result.

[0058] Step S6: Change the distance between the measurement target and the ranging system, re-execute steps S1 to S5, calculate the ranging result of the new distance and record it. For all ranging error results, refer to Figure 4 When the measuring distance is 1000-3000mm, the measurement error is less than 0.6%; when the measuring distance is 3000-6000mm, the measurement error is less than 0.8%; when the measuring distance is 6000-9000mm, the measurement error is less than 1.3%. This verifies that the new delay phase-locked loop high-precision laser ranging method and system disclosed in this invention has high ranging accuracy.

[0059] It will be easily understood by those skilled in the art that the above description is merely 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 in the scope of protection of the present invention.

Claims

1. A new delay phase-locked loop high-precision laser ranging method, characterized in that: The following steps are involved: S1: Generates two identical m-sequence signals. One signal is transmitted to the laser to modulate the laser signal, and the other signal is sent to the matched filter as a reference signal for subsequent distance calculation. S2: The laser signal obtained in step S1 is reflected by the target, received by the detector and converted into an electrical signal, which is then transmitted to the matched filter as an echo signal for distance calculation; S3: performing matched filtering on the reference signal obtained in step S1 and the echo signal obtained in step S2 to obtain a rough measurement result of the matched filtering; S4: sending the coarse measurement result obtained in step S3 to a new delay-locked loop based on the sinc function as a model, calculating the initial values ​​of the sinc function parameters, and continuing to fit the model function to obtain a more accurate fine measurement result; S5: Add the rough measurement result obtained in step S3 and the fine measurement result obtained in step S4 to obtain a final measurement result.

2. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 1, characterized in that: The sequence signal in step S1 is an m-sequence signal. When the m-sequence is logic "1", the laser emits full-power laser; when the m-sequence is logic "0", the laser does not emit laser, which is used to modulate the laser signal amplitude.

3. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 1, characterized in that: The matched filtering result in step S3 includes the peak point and the four points on its left and right.

4. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 3, characterized in that: The peak point in step S3 is (τ, P), where P is the peak value of the matched filtering result and τ is the horizontal coordinate of the peak value of the matched filtering result.

5. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 4, characterized in that: The calculation formula of the rough measurement result d1 in step S3 is: Where c is the speed of light.

6. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 4, characterized in that: The four points on the left and right of the peak point in step S3 are (-2d, E2), (-d, E1), (d, L1), and (2d, L2), respectively, where E1 is the point on the left side of the peak P of the matched filtering result, E2 is the point on the left side of the matched filtering result E1, L1 is the point on the right side of the peak P of the matched filtering result, L2 is the point on the right side of the matched filtering result L1, and d is the interval between the two points in the matched filtering result.

7. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 6, characterized in that: The sinc function calculation formula in step S4 is: f(x)=a0sinc(a1x+a2) Wherein, a0, a1, and a2 are parameters of the sinc function, P, E1, E2, L1, and L2 are five point values ​​of the matched filtering rough measurement result obtained in step S3, and d is the interval between two points of the matched filtering result obtained in step S3.

8. A novel delay phase-locked loop high-precision laser ranging method as claimed in claim 7, characterized in that: The calculation formula for the precise measurement result d2 in step S4 is: Where c is the speed of light.

9. The novel delay phase-locked loop high-precision laser ranging method according to claim 1, characterized in that: The method further includes step S6, changing the distance between the measurement target and the ranging system, re-executing steps S1 to S5, calculating the ranging result of the new distance and recording the ranging error.

10. A novel delay phase-locked loop high-precision laser ranging system, using the novel delay phase-locked loop high-precision laser ranging method according to any one of claims 1 to 9, characterized in that: It includes a signal generation module, a laser emission module, a detector module and a signal processing module. The signal processing module includes a matched filter and a delay phase-locked loop; The signal generation module generates two m-sequence modulation signals, one of which is transmitted to the laser to modulate the laser signal, and the other is sent to the matched filter as a reference signal for subsequent distance calculation; The laser emission module receives the modulation signal and emits the modulated laser signal toward the measurement target; The laser signal is reflected by the detection target, received and converted by the detector module, and sent to the signal processing module as an echo signal; The signal processing module performs matched filtering processing on the reference signal of the signal generation module and the echo signal of the detector module, and obtains the final ranging result and outputs it.

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