A laser radar target speed determination method based on galvanometer ring light scanning

Abstract

The application discloses a laser radar target speed measuring method based on a galvanometer circular ring light scanning, which comprises the following steps: a pulse laser emits pulse light; a synchronous generator reduces the frequency of the pulse laser; a scanning galvanometer scans the circular ring light; a servo turntable feeds back the angle between a local coordinate system and a global coordinate system of the light axis; and the circular ring light detects the target and reverses the target azimuth information. The application combines the method of emitting pulse laser and scanning the circular ring light by the galvanometer, uses the distance information of the target echo at different time and the time information of the target in the pulse interval, reverses the target coordinate information, and greatly improves the detection accuracy. Meanwhile, the target speed is measured by the time information difference between the echo signals and the azimuth information of the target on the circular ring at different time, effectively solves the problem that the feedback angle error is large due to the influence of the installation and adjustment error, the galvanometer gravity and the like when the scanning angle is fed back by the traditional galvanometer, and has a significant significance for improving the inversion target positioning precision and speed precision.

Description

Technical Field

[0001] This invention relates to the field of lidar target detection technology, and in particular to a lidar target velocity measurement method based on galvanometer ring light scanning. Background Technology

[0002] A lidar (Light Detection and Ranging) system is a radar system that uses emitted laser beams to detect the position, velocity, and other characteristics of a target. Its working principle involves transmitting a detection signal to the target, then processing the received signal reflected back from the target with the transmitted signal to obtain relevant information about the target.

[0003] For example, Chinese patent document CN117111078A discloses a method and lidar for detecting the distance and speed of a target; Chinese patent document CN117607887A discloses a speed detection method, device and lidar based on TOF technology.

[0004] Currently, lidar velocity measurement mainly relies on two techniques: Doppler effect-based lidar, which uses the frequency shift of reflected light when a beam illuminates a moving object to extract the target's distance and velocity. However, this technique only measures radial velocity and requires multi-angle data fusion to obtain a complete velocity vector. Velocity measurement based on time difference and displacement calculation uses pulsed lasers to continuously measure the target's displacement and calculate velocity. However, this technique requires real-time acquisition of the scanning angle of the scanning device, which inevitably leads to feedback errors in the target's position angle information due to system assembly errors and gravity, and it has low sensitivity to targets with rapid acceleration.

[0005] LiDAR based on galvanometer ring scanning uses a galvanometer to scan the laser spot into a ring shape in space, which can greatly improve the target detection probability of the lidar. However, with this scanning method, when using the above traditional methods to measure the velocity of small, randomly moving targets at low altitudes, there are often problems such as untimely response and inaccurate measurement.

[0006] In summary, when using galvanometer-scanning ring-beam lidar to measure the velocity of small targets at low altitudes, a fast and effective measurement method is urgently needed to determine the target's velocity vector. Summary of the Invention

[0007] This invention provides a method for determining the target velocity of a lidar based on a galvanometer circular light scanning system, which can solve the problems of inaccurate azimuth information feedback from lidar galvanometers and the limitation of measurement distance by the camera.

[0008] A method for determining the target velocity of a lidar based on galvanometer ring light scanning includes the following steps:

[0009] (1) The lidar transmitter uses a pulsed laser. The pulsed laser and the scanning galvanometer are linked through a synchronous triggering device to control the pulse frequency of the pulsed laser. downclocking This is then sent to the scanning galvanometer, causing the external trigger of the scanning galvanometer to run;

[0010] (2) Set the rising edge of the pulsed laser to externally trigger the scanning galvanometer as the time. Within one scanning galvanometer rotation cycle, calculate the first... Target movement distance within the time of one laser pulse ;

[0011] (3) Place the target in the local coordinate system, when the first... When the echo signal is measured from the next laser pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the scanning galvanometer is... for rad, further determining the target's three-dimensional coordinates in the local coordinate system. and the target's three-dimensional coordinates in the global coordinate system ;

[0012] (4) When the target moves rapidly to the ring light in the next moment, calculate the first... Target movement distance within the time of one laser pulse ;

[0013] (5) When the first When the echo signal is measured from the next laser pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the scanning galvanometer is... for rad, further determining the target's three-dimensional coordinates in the global coordinate system. and the target's three-dimensional coordinates in the global coordinate system ;

[0014] (6) Based on the coordinates of the target when it was detected twice and Further calculations are performed to determine the target velocity information.

[0015] In step (2), the first The rise time of the next laser pulse is ; in the During the second pulse, the target echo signal time is ;according to and Calculate the first Target movement distance within the time of one laser pulse The formula is:

[0016] ;

[0017] In the formula, It represents the speed of light.

[0018] The location of the lidar is set as the origin of both the local and global coordinate systems. The local coordinate system refers to the azimuth angle of the lidar's rotation on the servo turntable. Pitch angle is At that time, the center of the annular light was taken as The coordinate system defined by the axis; the global coordinate system refers to the coordinate system with the center of the annular optical circle as the coordinate system when the pitch and azimuth angles of the lidar are 0 as it rotates with the servo turntable. The coordinate system defined by the axes.

[0019] In step (3), the target's three-dimensional coordinates in the local coordinate system The calculation is as follows:

[0020] ;

[0021] ;

[0022] ;

[0023] In the formula, Indicates the radius of the annular light. This indicates the initial scanning angle corresponding to the rising edge triggered by the scanning galvanometer.

[0024] In step (3), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows:

[0025] ;

[0026] In the formula, For the first The difference in azimuth angle between the local coordinate system and the global coordinate system during the next pulse time. For the first The difference in pitch angle between the local coordinate system and the global coordinate system during the subpulse time.

[0027] In step (4), the first The rise time of the next laser pulse is ; in the During the second pulse, the target echo signal time is ;according to and Calculate the first Target movement distance within the time of one laser pulse The formula is:

[0028] ;

[0029] In the formula, It represents the speed of light.

[0030] In step (5), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows:

[0031] ;

[0032] ;

[0033] ;

[0034] In the formula, Indicates the radius of the annular light. This indicates the initial scanning angle corresponding to the rising edge triggered by the scanning galvanometer.

[0035] In step (5), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows:

[0036] ;

[0037] In the formula, For the first The difference in azimuth angle between the local coordinate system and the global coordinate system during the next pulse time. For the first The difference in pitch angle between the local coordinate system and the global coordinate system during the subpulse time.

[0038] In step (6), the formula for calculating the target velocity information is as follows:

[0039] ;

[0040] In the formula, Indicates the speed of the target.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. This invention combines the emission of pulsed laser with the scanning of circular light by a galvanometer. By utilizing the distance information of the target echo at different times and the time information of the pulse interval where the target is located, the target coordinate information is inverted. This solves the problem of limited detection range when traditional CCD area array cameras measure target coordinate information, and greatly improves the detection range.

[0043] 2. This invention measures the target velocity by using the time information difference between echo signals and the target's azimuth information on the ring at different times. This effectively solves the problem of large feedback angle errors caused by installation and adjustment errors, galvanometer gravity, etc. when using traditional galvanometer feedback scanning angle. It has significant implications for improving the accuracy of target positioning and velocity inversion. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments 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 from these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a lidar target velocity determination method based on galvanometer ring light scanning, according to an embodiment of the present invention.

[0046] Figure 2 This diagram illustrates the time, number of pulses, mirror frequency, and laser pulse frequency when the target object is scanned twice on the ring light by a pulsed laser.

[0047] Figure 3 This is a schematic diagram of the local coordinate system at different times when the target object is scanned and detected by pulsed laser on a ring of light.

[0048] Figure 4 This diagram illustrates the angle, the angle between the local coordinate system and the global coordinate system, and the detection distance in the initial state of galvanometer scanning. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0050] The lidar transmitter uses a pulsed laser, and the scanning galvanometer can be externally triggered. For example... Figure 1 As shown, a method for determining the target velocity of a lidar based on galvanometer ring light scanning includes:

[0051] The laser and scanning galvanometer are linked via a synchronous triggering device to control the laser pulse frequency. Frequency reduction, reducing the pulse frequency The signal is sent to the scanning galvanometer, triggering its operation externally. The initial scanning angle corresponds to the rising edge of the scanning galvanometer trigger. This information can be read from the galvanometer itself. Assuming a laser's pulse frequency is 1000Hz, and the down-frequency pulse signal is 20Hz, the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger is... The value is 1 mrad. Furthermore, the lidar includes a servo turntable that can provide feedback on the initial rotation angle. This allows for the inversion of target position and velocity information.

[0052] The following describes the matching of the laser pulse frequency and the galvanometer frequency, as well as the setting of the arc size of the ring light occupied by adjacent pulses. The laser pulse frequency is... 1000Hz, the duration of a single laser pulse is 0.0001 seconds; the frequency after downsampling via the sync generator is If the frequency is 20Hz, then the frequency of the galvanometer is 20Hz, the time taken for each revolution of the galvanometer scanning ring light is 0.05 seconds. At this time, the number of laser pulses contained in each ring of light is For 50 pulses, the arc between two adjacent pulses on the ring represents the arc of the entire ring. rad, 2π / 50≈0.126rad.

[0053] The rising edge of the pulsed laser for external triggering of the galvanometer is set to time. Within one galvanometer rotation cycle, the number of... The rise time of the next laser pulse is In the first During the second pulse, the echo signal time of the small target is... ,like Figure 2 As shown in the diagram. According to the laser ranging formula:

[0054] ;

[0055] in, Represents the speed of light, 3 × 10 8 m / s, the target distance information on the ring at that pulse can be calculated. Assuming the echo signal is measured under the 3rd laser pulse, at the 1st... During the next pulse, the time between the small target echo signal and the laser rise edge... The duration is 10 μs; the target distance during this pulse is measured. =3×10 8 (m / s) × 10 (μs) / 2 = 1500m. The location of the lidar is set as the origin of both the local and global coordinate systems.

[0056] like Figure 3 As shown, the local coordinate system refers to the coordinate system in which the lidar rotates on the servo turntable at an azimuth angle of 100°. The pitch angle is At that time, the center of the annular light was taken as The axis, the defined coordinate system; the global coordinate system refers to the coordinate system with the center of the circular optical circle as the coordinate system when the pitch and azimuth angles of the lidar are 0 as it rotates with the servo turntable. The axis is the defined coordinate system. To facilitate the calculation of the target's azimuth information when the echo occurs, the target is first placed within the local coordinate system.

[0057] Given that the arc between two consecutive laser pulses on the ring is If the value is 0.126 rad, then when the When the echo signal is measured for the third pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the galvanometer is: rad, 3 × 0.126 = 0.378 rad, such as Figure 4 As shown, in the local coordinate system, the three-dimensional coordinate information of the target can be represented as follows:

[0058] ;

[0059] ;

[0060] ;

[0061] Will , , , , Substituting the above three formulas, the target's local coordinate system can be calculated. = (0.554, 1.394, 1500).

[0062] At this point, the difference in azimuth between the local coordinate system and the global coordinate system is: =0.5rad, pitch angle difference is =0.3 rad. To facilitate the measurement of target velocity, the target's three-dimensional coordinate information is represented in a global coordinate system:

[0063] ;

[0064] Will , , Substituting into the above formula, the three-dimensional global coordinate expression of the target can be calculated. = (-686.730, -441.948, 1258.206).

[0065] When the small target moves rapidly to the ring of light in the next moment, the first... The rise time of the next laser pulse is , No. During the second pulse, the echo signal time of the small target is... ,like Figure 2 As shown in the diagram. According to the laser ranging formula:

[0066] ;

[0067] The distance to the small target at this moment can be calculated. Assuming the echo signal is measured during the 9th laser pulse, the time between the small target echo signal and the laser rise edge is... The pulse duration was 10.1 μs; the target distance was measured during this pulse. =3×10 8 (m / s)×10.1(μs) / 2=1515m.

[0068] When the When the echo signal is measured for the 9th pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the galvanometer is: rad, which is 1.134 rad, such as Figure 4 As shown. Then, in the local coordinate system, the target's three-dimensional coordinate information can be represented as:

[0069] ;

[0070] ;

[0071] ;

[0072] Will , , , , Substituting the above three formulas, the target's local coordinate system can be calculated. = (1.373, 0.641, 1514.999). At this point, the difference in azimuth between the local and global coordinate systems is... =0.52rad, pitch angle difference is rad, such as Figure 3 As shown. The target's three-dimensional coordinates at this moment are represented in the global coordinate system:

[0073] ;

[0074] Will , , Substituting into the above formula, the three-dimensional global coordinate expression of the target can be calculated. = (-713.467, -475.959, 1248.859).

[0075] Based on the coordinate information corresponding to the two times the target was detected, the target velocity information can be obtained:

[0076] ;

[0077] Assuming the time difference between two detections of the target object =2s, will , Substituting into the above formula, the target speed of 0.7094 m / s can be calculated.

[0078] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the velocity of a lidar target based on galvanometer ring light scanning, characterized in that, Includes the following steps: (1) The lidar transmitter uses a pulsed laser. The pulsed laser and the scanning galvanometer are linked through a synchronous triggering device to control the pulse frequency of the pulsed laser. downclocking This is then sent to the scanning galvanometer, causing the external trigger of the scanning galvanometer to run; (2) Set the rising edge of the pulsed laser to externally trigger the scanning galvanometer as the time. Within one scanning galvanometer rotation cycle, calculate the first... Target movement distance within the time of one laser pulse ; (3) Place the target in the local coordinate system, when the first... When the echo signal is measured from the next laser pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the scanning galvanometer is... for rad, further determining the target's three-dimensional coordinates in the local coordinate system. and the target's three-dimensional coordinates in the global coordinate system ; (4) When the target moves rapidly to the ring light in the next moment, calculate the first... Target movement distance within the time of one laser pulse ; (5) When the first When the echo signal is measured from the next laser pulse, the arc between the pulsed laser spot and the spot corresponding to the rising edge of the scanning galvanometer is... for rad, further determining the target's three-dimensional coordinates in the global coordinate system. and the target's three-dimensional coordinates in the global coordinate system ; (6) Based on the coordinates of the target when it was detected twice and Further calculations are performed to determine the target velocity information.

2. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (2), the first The rise time of the next laser pulse is ; in the During the second pulse, the target echo signal time is ;according to and Calculate the first Target movement distance within the time of one laser pulse The formula is: ； In the formula, It represents the speed of light.

3. The method for determining the target velocity of a lidar based on galvanometer ring light scanning according to claim 1, characterized in that, The local coordinate system and the global coordinate system both take the location of the lidar as the origin. The local coordinate system refers to the coordinate system where the lidar rotates on the servo turntable at an azimuth angle of 100°. Pitch angle is At that time, the center of the annular light was taken as The coordinate system defined by the axis; the global coordinate system refers to the coordinate system with the center of the circular optical circle as the coordinate system when the pitch and azimuth angles of the lidar are 0 as it rotates with the servo turntable. The coordinate system defined by the axes.

4. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (3), the target's three-dimensional coordinates in the local coordinate system The calculation is as follows: ； ； ； In the formula, Indicates the radius of the annular light. This indicates the initial scanning angle corresponding to the rising edge triggered by the scanning galvanometer.

5. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (3), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows: ； In the formula, For the first The difference in azimuth angle between the local coordinate system and the global coordinate system during the next pulse time. For the first The difference in pitch angle between the local coordinate system and the global coordinate system during the subpulse time.

6. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (4), the first The rise time of the next laser pulse is ; in the During the second pulse, the target echo signal time is ;according to and Calculate the first Target movement distance within the time of one laser pulse The formula is: ； In the formula, It represents the speed of light.

7. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (5), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows: ； ； ； In the formula, Indicates the radius of the annular light. This indicates the initial scanning angle corresponding to the rising edge triggered by the scanning galvanometer.

8. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (5), the target's three-dimensional coordinates in the global coordinate system The calculation is as follows: ； In the formula, For the first The difference in azimuth angle between the local coordinate system and the global coordinate system during the next pulse time. For the first The difference in pitch angle between the local coordinate system and the global coordinate system during the subpulse time.

9. The method for determining the velocity of a lidar target based on galvanometer ring scanning according to claim 1, characterized in that, In step (6), the formula for calculating the target velocity information is as follows: ； In the formula, Indicates the speed of the target.

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