Laser radar target speed measuring method based on galvanometer circular ring light scanning

Abstract

The invention discloses a laser radar target speed measuring method based on galvanometer circular ring light scanning. The method comprises the steps that a pulse laser emits pulse light; the synchronous generator performs frequency reduction on the pulse laser; the scanning galvanometer scans the circular ring light; the servo turntable feeds back the angles of the optical axis local coordinate system and the global coordinate system; and the circular ring light detects a target and inverts target azimuth information. According to the invention, through a method of combining pulse laser emission and galvanometer scanning of circular light, target coordinate information is inverted by using distance information of target echoes at different moments and time information of a pulse interval where a target is located, so that the detection accuracy is greatly improved; meanwhile, the target speed is measured through the time information difference between the echo signals and the azimuth information of the target on the circular ring at different moments, so that the problem of large feedback angle error caused by the influence of installation and adjustment error, galvanometer gravity and the like when a traditional galvanometer feeds back the scanning angle is effectively solved; the method has significant significance in improving the inversion target positioning precision and speed precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar target detection, in particular to a laser radar target speed measurement method based on galvanometer circular ring light scanning. BACKGROUND

[0002] Laser radar is a radar system that uses laser beams to detect the position and speed of targets. Its working principle is to emit a detection signal to the target, and then process the received signal reflected from the target and the transmitted signal to obtain information about the target.

[0003] A method for detecting the distance and speed of a target and a laser radar are disclosed in Chinese patent document CN117111078A, and a speed detection method and device based on TOF technology and a laser radar are disclosed in Chinese patent document CN117607887A.

[0004] Currently, laser radar speed measurement mainly relies on two technical means: Doppler effect-based speed measurement laser radar, which uses the frequency shift information of reflected light when a light beam is incident on a moving object to extract the distance and speed of the target. However, this technology only measures the radial velocity and requires multi-angle data fusion to obtain the complete velocity vector. The speed measurement based on time difference and displacement calculation uses pulsed laser to continuously measure the displacement of the target object and calculates the speed. However, this technology needs to obtain the scanning angle of the scanning device in real time, and it is inevitable that the feedback error of the target position angle information will be caused by system installation and adjustment errors and gravity factors, and the sensitivity to fast acceleration targets is low.

[0005] The laser radar based on galvanometer circular ring light scanning uses a galvanometer to scan the laser spot into a circular ring shape in space, which can greatly improve the target detection probability of the laser radar. However, in this scanning mode, if the traditional method is used to measure the speed of a low-altitude small target with random motion, there will often be problems of untimely response and inaccurate measurement.

[0006] In summary, the laser radar with galvanometer scanning circular ring light needs a fast and effective measurement method to measure the speed vector of the target when measuring the speed of a low-altitude small target. SUMMARY

[0007] The present application provides a laser radar target speed measurement method based on galvanometer circular ring light scanning, which can solve the problem of inaccurate galvanometer feedback azimuth information and limited measurement distance by the existing laser radar.

[0008] A laser radar target speed measurement method based on galvanometer circular ring light scanning, comprising the following steps: (1) the laser radar transmitting end adopts a pulse laser, the pulse laser and a scanning galvanometer are linked through a synchronous trigger device, the pulse frequency of the pulse laser is reduced to , and then sent to the scanning galvanometer, so that the scanning galvanometer is externally triggered to operate; (2) the rising edge time of the pulse laser externally triggering the scanning galvanometer is set as time , in a scanning galvanometer rotation period, the target moving distance in the time of the th laser pulse is calculated ; (3) the target is placed in a local coordinate system, when the echo signal is measured in the time of the th laser pulse, the radian between the pulse laser spot and the spot corresponding to the rising edge of the scanning galvanometer is rad, and the three-dimensional coordinates of the target in the local coordinate system and the three-dimensional coordinates of the target in the global coordinate system are further determined; (4) when the target quickly moves to the annular light at the next moment, the target moving distance in the time of the th laser pulse is calculated ; (5) when the echo signal is measured in the time of the th laser pulse, the radian between the pulse laser spot and the spot corresponding to the rising edge of the scanning galvanometer is rad, and the three-dimensional coordinates of the target in the global coordinate system and the three-dimensional coordinates of the target in the global coordinate system are further determined; (6) according to the coordinates and of the target detected twice, the target speed information is further calculated.

[0009] In step (2), the rising edge time of the th laser pulse is ; in the time of the th pulse, the target echo signal time is ; the target moving distance in the time of the th laser pulse is calculated according to and , and the formula is: ; In the formula, represents the speed of light.

[0010] ​Set the position of the laser radar as the origin of the local coordinate system and the global coordinate system. The local coordinate system refers to the position of the laser radar on the servo turntable. , the pitch angle is When the center of the ring light is The global coordinate system refers to the coordinate system defined by the axis; the global coordinate system refers to the coordinate system with the center of the ring light as the center when the pitch and azimuth angles of the laser radar are 0 as the servo turntable rotates. The coordinate system defined by the axes.

[0011] In step (3), the three-dimensional coordinates of the target in the local coordinate system are , calculated as follows: ; ; ; Where, represents the radius of the ring light, Indicates the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger.

[0012] In step (3), the three-dimensional coordinates of the target in the global coordinate system are , calculated as follows: ; Where, For the The azimuth difference between the local coordinate system and the global coordinate system within the sub-pulse time, For the The difference in pitch angle between the local coordinate system and the global coordinate system within the sub-pulse time.

[0013] In step (4), The rising edge time of the laser pulse is ; in the Within the pulse time, the target echo signal time is ;according to and Calculate the The target's moving distance within the laser pulse time , the formula is: ; Where, Represents the speed of light.

[0014] In step (5), the three-dimensional coordinates of the target in the global coordinate system are , calculated as follows: ; ; ; In the formula, represents the radius of the circular ring light, represents the initial scanning angle corresponding to the rising edge of the scanning mirror trigger.

[0015] In step (5), the three-dimensional coordinates of the target in the global coordinate system are calculated as follows: ; In the formula, is the azimuth angle difference between the local coordinate system and the global coordinate system in the nth pulse time, is the pitch angle difference between the local coordinate system and the global coordinate system in the nth pulse time. In the formula,

[0016] In step (6), the formula for calculating the target speed information is as follows: ; In the formula, represents the speed of the target.

[0017] Compared with the prior art, the present application has the following beneficial effects: 1. The present application uses the distance information of the target echo at different times and the time information of the target in the pulse interval to invert the target coordinate information by combining the method of emitting pulsed laser and the scanning circular ring light of the galvanometer, thereby solving the problem of limited detection distance when measuring the target coordinate information by the traditional CCD area camera, and greatly improving the detection distance; 2. The present application measures the target speed by the time information difference between the echo signals and the azimuth information of the target on the circular ring at different times, thereby effectively solving the problem of large feedback angle error caused by installation and adjustment errors, galvanometer gravity and other factors when the traditional galvanometer feedback scanning angle, which has significant significance for improving the inversion accuracy of target positioning and speed. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 It is a flow chart of a laser radar target speed measurement method based on galvanometer circular ring light scanning according to an embodiment of the present application.

[0020] Figure 2 ​This is a schematic diagram of the corresponding time, pulse number, galvanometer frequency, and laser pulse frequency when the target is scanned and detected twice by the pulsed laser on the ring light.

[0021] Figure 3 Schematic diagram of the local coordinate system coordinates corresponding to different times when the target object is detected by pulsed laser scanning on the ring light.

[0022] Figure 4 Schematic diagram of the galvanometer scanning angle in the initial state, the angle between the local coordinate system and the global coordinate system, and the detection distance. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0024] The laser radar transmitter uses a pulsed laser, and the scanning galvanometer can be externally triggered. Figure 1 As shown, a laser radar target speed measurement method based on galvanometer ring light scanning includes: The laser and the scanning galvanometer are linked through a synchronous trigger device to adjust the laser pulse frequency. Frequency reduction, the pulse frequency after frequency reduction Sent to the scanning galvanometer, so that the scanning galvanometer is externally triggered to run, and the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger It can be read by the galvanometer itself. Assuming that the pulse frequency of a laser is 1000Hz and the pulse signal after frequency reduction is 20Hz, the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger is The laser radar includes a servo turntable that provides feedback on the initial rotation angle, allowing the target's position and velocity to be inverted.

[0025] The following describes how to match the laser pulse frequency with the galvanometer frequency, as well as how to set the arc size of the circular light occupied by adjacent pulses. The laser pulse frequency is , 1000Hz, the time of a single pulse laser is , 0.0001 seconds; the frequency after the synchronization generator is reduced is , 20Hz, then the frequency of the galvanometer is , 20Hz, the time taken by the galvanometer to scan the ring light is , 0.05 seconds. At this time, the number of laser pulses contained in each circle of ring light is , which is 50 pulses. The arc between two adjacent pulses on the ring occupies the arc of the entire ring. rad, 2π / 50≈0.126rad.

[0026] Set the rising edge of the pulse laser to trigger the galvanometer as the time , in one galvanometer rotation cycle, the number of The rising edge time of the laser pulse is In the Within the pulse time, the echo signal time of the small target is ,like Figure 2 As shown in . According to the laser ranging formula: ; in, represents the speed of light, 3×10 8 m / s, the target distance information of the pulse on the ring can be calculated. Assuming that the echo signal is measured under the third laser pulse, The time between the small target echo signal and the rising edge of the laser during the second pulse The target distance at this pulse is 10μs. =3×10 8 (m / s) × 10 (μs) / 2 = 1500m. Set the position of the lidar as the origin of the local coordinate system and the global coordinate system.

[0027] like Figure 3 As shown in the figure, the local coordinate system refers to the laser radar rotating on the servo turntable with an azimuth angle of , the pitch angle is When the center of the ring light is Axis, the coordinate system defined by the axis; the global coordinate system refers to the laser radar when the pitch and azimuth angles are 0 as the servo turntable rotates, with the center of the ring light as the In order to conveniently calculate the position information of the target echo, the target is first placed in the local coordinate system.

[0028] It is known that the arc between two adjacent pulse lasers on the ring is rad, is 0.126rad, then when the When the echo signal is measured for the third pulse, the arc between the pulse laser spot and the spot corresponding to the rising edge of the galvanometer is rad, 3×0.126=0.378rad, such as Figure 4 As shown, in the local coordinate system, the three-dimensional coordinate information of the target can be expressed as ; ; ; Will 、 、 、 、 Substitute the above three formulas, the target local coordinate system can be calculated = (0.554, 1.394, 1500).

[0029] At this time, the azimuth angle difference between the local coordinate system and the global coordinate system is = 0.5 rad, the pitch angle difference is = 0.3 rad. In order to facilitate the measurement of target speed, and then the target three-dimensional coordinate information is placed in the global coordinate system to represent: ; Substitute 、 、 The above formula, the target three-dimensional global coordinate expression can be calculated = (-686.730, -441.948, 1258.206).

[0030] When the small target quickly moves to the next moment to the ring light, the rising time of the first Laser pulse is , the small target echo signal time in the Pulse time is , as shown in Figure 2 According to the laser ranging formula: ; The distance information of the small target at this moment can be calculated. Assuming that the 9th laser pulse is measured, the time of the small target echo signal distance from the laser rising edge is 10.1 μs, and the target distance measured at this pulse = 3 × 10 8 (m / s) × 10.1 (μs) / 2 = 1515 m.

[0031] When the 9th (9th) pulse measures the echo signal, the arc between the pulse laser spot and the spot corresponding to the rising edge of the galvanometer at this time is rad, which is 1.134 rad, as shown in . Then in the local coordinate system, the three-dimensional coordinate information of the target can be represented as: Figure 4 ; ; ; ; Substitute 、 、 、 , Substituting the above three formulas, the local coordinate system of the target can be calculated = (1.373, 0.641, 1514.999). At this time, the azimuth angle difference between the local coordinate system and the global coordinate system is = 0.52 rad, the pitch angle difference is rad, as shown in Figure 3 . The three-dimensional coordinate information of the target at this moment is placed in the global coordinate system, as shown in ; Substituting , , into the above formula, the three-dimensional global coordinate expression of the target can be calculated = (-713.467, -475.959, 1248.859).

[0032] According to the coordinate information corresponding to the target being detected twice, the target speed information is obtained: ; Suppose the time difference when the target is detected twice is = 2 s, substituting , into the above formula, the target speed 0.7094 m / s can be calculated.

[0033] The above embodiments have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the present application. Any modification, supplement and equivalent replacement made within the principle range of the present application should be included in the protection range of the present application.

Claims

1. A laser radar target speed measurement method based on galvanometer ring light scanning, characterized in that: The following steps are involved: (1) The laser radar transmitter uses a pulse laser, which is connected to the scanning galvanometer through a synchronous trigger device, and the pulse frequency of the pulse laser is Frequency reduction Then it is sent to the scanning galvanometer, so that the scanning galvanometer is externally triggered to run; (2) Set the rising edge of the pulse laser to trigger the scanning galvanometer externally as the time , in one scanning galvanometer rotation cycle, calculate the The target's moving distance within the laser pulse time ; (3) Place the target in the local coordinate system. When the laser pulse measures the echo signal, the arc between the pulse laser spot and the spot corresponding to the rising edge of the scanning galvanometer for rad, further determine the three-dimensional coordinates of the target in the local coordinate system And the three-dimensional coordinates of the target in the global coordinate system ; (4) When the target quickly moves to the ring light at the next moment, calculate the The target's moving distance within the laser pulse time ; (5) When When the laser pulse measures the echo signal, the arc between the pulse laser spot and the spot corresponding to the rising edge of the scanning galvanometer for rad, further determine the three-dimensional coordinates of the target in the global coordinate system And the three-dimensional coordinates of the target in the global coordinate system ; (6) Based on the coordinates of the target when it was detected twice and , further calculate the target speed information.

2. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1 is characterized in that: In step (2), The rising edge time of the laser pulse is ; in the Within the pulse time, the target echo signal time is ;according to and Calculate the The target's moving distance within the laser pulse time , the formula is: ； Where, Represents the speed of light.

3. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1 is characterized in that: The local coordinate system and the global coordinate system take the position of the laser radar as the origin. The local coordinate system refers to the position of the laser radar on the servo turntable. , the pitch angle is When the center of the ring light is The global coordinate system refers to the coordinate system defined by the axis; the global coordinate system refers to the coordinate system with the center of the ring light as the center when the pitch and azimuth angles of the laser radar are 0 as the servo turntable rotates. The coordinate system defined by the axes.

4. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (3), the three-dimensional coordinates of the target in the local coordinate system are , calculated as follows: ； ； ； Where, represents the radius of the ring light, Indicates the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger.

5. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (3), the three-dimensional coordinates of the target in the global coordinate system are , calculated as follows: ； Where, For the The azimuth difference between the local coordinate system and the global coordinate system within the sub-pulse time, For the The difference in pitch angle between the local coordinate system and the global coordinate system within the sub-pulse time.

6. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (4), The rising edge time of the laser pulse is ; in the Within the pulse time, the target echo signal time is ;according to and Calculate the The target's moving distance within the laser pulse time , the formula is: ； Where, Represents the speed of light.

7. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (5), the three-dimensional coordinates of the target in the global coordinate system are , calculated as follows: ； ； ； Where, represents the radius of the ring light, Indicates the initial scanning angle corresponding to the rising edge of the scanning galvanometer trigger.

8. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (5), the three-dimensional coordinates of the target in the global coordinate system are , calculated as follows: ； Where, For the The azimuth difference between the local coordinate system and the global coordinate system within the sub-pulse time, For the The difference in pitch angle between the local coordinate system and the global coordinate system within the sub-pulse time.

9. The laser radar target speed measurement method based on galvanometer circular light scanning according to claim 1, characterized in that: In step (6), the formula for calculating the target speed information is as follows: ； Where, Indicates the speed of the target.

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