Timing synchronization control method, system, medium and coordinate calculation method of dual-axis scanning laser radar system

Abstract

The application provides a timing synchronization control method, system, medium and coordinate calculation method of a dual-axis scanning laser radar system, the dual-axis scanning laser radar system comprising a vertical scanning element for performing vertical direction beam scanning and a horizontal scanning element for performing horizontal direction beam scanning; the timing synchronization control method of the dual-axis scanning laser radar system comprising: acquiring a rotation position signal of the horizontal scanning element in real time; determining that the horizontal scanning element is currently in a scanning imaging window or a scanning switching window based on the rotation position signal; controlling a scanning angle jump of the vertical scanning element based on the scanning imaging window or the scanning switching window, so that, after the scanning timing of the vertical scanning element and the horizontal scanning element is synchronized, a laser trigger signal is output to control a laser transceiver module to emit light and receive. The application can realize accurate synchronization of the dual-axis scanning laser radar system and has good portability and expansibility.

Description

Technical Field

[0001] This application belongs to the field of lidar technology, and in particular relates to a timing synchronization control method, system, medium and coordinate calculation method for a dual-axis scanning lidar system. Background Technology

[0002] Scanning lidar uses a mechanical scanning mechanism to drive a laser beam to deflect in an orderly manner in space, expanding the transceiver field of view horizontally and vertically to achieve wide-area, high-resolution detection of the surrounding environment. Its core lies in using mechanical components—such as rotating motors, galvanometers, and rotating mirrors—to change the laser emission direction, constructing a three-dimensional point cloud image through point-by-point scanning. Depending on the scanning scheme, common architectures include mechanical rotation (overall rotation), rotating mirror (mirror rotation), and galvanometer (mirror oscillation). Horizontal scanning is responsible for achieving 360° or a large field of view coverage, while vertical scanning determines the elevation range and line density of the detection.

[0003] Dual-axis scanning LiDAR is a special architecture among scanning LiDAR systems, characterized by separating horizontal and vertical scanning functions onto two independent mechanical axes for coordinated operation. For example, when the horizontal axis is a rotating mirror and the vertical axis is a tilting mirror, the horizontal rotating mirror rotates at a constant speed to achieve a wide circumferential coverage, ensuring scanning uniformity and stability; the vertical tilting mirror precisely controls the pitch angle in the vertical direction, flexibly adjusting the vertical field of view and the number of scan lines. Both are spatially synthesized into a regular point cloud array through precise timing synchronization. This split-axis decoupling design allows for independent optimization of the horizontal rotation speed and vertical frame rate, avoiding the limitation on horizontal scanning speed caused by vertical resolution improvements in traditional coaxial systems. Furthermore, by optimizing the tilting mirror motion mode, higher point cloud density and detection accuracy can be achieved in key field-of-view areas, making it particularly suitable for scenarios with stringent perception quality requirements, such as autonomous driving and high-precision mapping. Therefore, in a dual-axis scanning architecture, the coordinated operation of the vertical and horizontal scanning elements is crucial for achieving high-quality point cloud data. How to precisely control timing synchronization in a dual-axis scanning LiDAR is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] This application provides a timing synchronization control method, system, medium, and coordinate calculation method for a dual-axis scanning lidar system, which solves the problems of low timing synchronization control accuracy or conflicts in existing dual-axis scanning lidar systems.

[0005] In a first aspect, this application provides a timing synchronization control method for the dual-axis scanning lidar system. The dual-axis scanning lidar system includes a vertical scanning element for vertical beam scanning and a horizontal scanning element for horizontal beam scanning; the method includes:

[0006] The rotational position signal of the horizontal scanning element is acquired in real time;

[0007] Based on the rotation position signal, it is determined whether the horizontal scanning element is currently in the scanning imaging window or the scanning switching window;

[0008] Based on the scanning imaging window or the scanning switching window, the scanning angle of the vertical scanning element is controlled to synchronize the scanning timing of the vertical scanning element with that of the horizontal scanning element, and then a laser trigger signal is output to control the laser transceiver module to emit light and receive light.

[0009] In one implementation of the first aspect, controlling the scanning motion of the vertical scanning element based on the scanning imaging window or the scanning switching window includes:

[0010] If the horizontal scanning element is within the scanning imaging window, the vertical scanning element is controlled not to change its scanning angle, so that the vertical scanning element is stabilized at the scanning angle corresponding to the current scanning imaging window.

[0011] If the horizontal scanning element is within the scanning switching window, the vertical scanning element is controlled to jump from the current scanning angle to the target scanning angle, where the target scanning angle is the scanning angle corresponding to the next scanning imaging window adjacent to the current scanning switching window.

[0012] In one implementation of the first aspect, the method further includes:

[0013] Based on a preset jump-to-position threshold, it is determined whether the vertical scanning element has jumped to the target scanning angle; wherein, when the absolute value of the difference between the current scanning angle and the target scanning angle is less than the jump-to-position threshold, it is determined that the vertical scanning element has jumped to the target scanning angle and a position signal is triggered.

[0014] In one implementation of the first aspect, the method further includes:

[0015] When the horizontal scanning element is within the scanning imaging window and the positioning signal is triggered, a laser trigger signal is output to control the laser transceiver module to emit light and receive light.

[0016] In one implementation of the first aspect, the horizontal scanning element has N reflective surfaces, and the horizontal scanning element passes through N reflective surfaces when it rotates one revolution in the horizontal direction; the N reflective surfaces correspond to N scanning imaging windows and N scanning switching windows; the scanning switching windows correspond to the scanning transition region between adjacent reflective surfaces.

[0017] In one implementation of the first aspect, determining whether the horizontal scanning element is currently in a scanning imaging window or a scanning switching window based on the rotation position signal includes:

[0018] Obtain the effective scanning angle range corresponding to the N scanning imaging windows and the scanning transition angle range corresponding to the M scanning switching windows;

[0019] Based on the rotation position signal, the N effective scanning angle ranges and the N scanning transition angle ranges, the current scanning imaging window sequence number or scanning switching window sequence number of the horizontal scanning element is determined.

[0020] In one implementation of the first aspect, the method further includes:

[0021] Multiple scanning angles are set for the vertical scanning element, and each scanning angle corresponds to at least one scanning imaging window.

[0022] Secondly, this application provides a coordinate calculation method, which is applied to a dual-axis scanning lidar system after timing synchronization control is performed using the method described in any of the first aspects; the method includes:

[0023] A laser transceiver module is used for emission and reception to obtain laser ranging values; the laser ranging values ​​correspond to the total optical path of the beam from the laser emission point through the vertical scanning element and the horizontal scanning element to the target point.

[0024] The three-dimensional coordinates of the target point are calculated based on the laser ranging value, the current rotation position of the horizontal scanning element, and the current scanning angle of the vertical scanning element.

[0025] Thirdly, this application provides a timing synchronization control system for a dual-axis scanning lidar system. The dual-axis scanning lidar system includes a vertical scanning element for vertical beam scanning and a horizontal scanning element for horizontal beam scanning; the system includes:

[0026] An angle acquisition module is configured to acquire the rotational position signal of the horizontal scanning element in real time;

[0027] The window module is configured to determine whether the horizontal scanning element is currently in a scanning imaging window or a scanning switching window based on the rotation position signal;

[0028] The synchronization module is configured to control the scanning angle jump of the vertical scanning element based on the scanning imaging window or the scanning switching window, so that the scanning timing of the vertical scanning element and the horizontal scanning element are synchronized, and then output a laser trigger signal to control the laser transceiver module to emit light and receive light.

[0029] Fourthly, this application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program that, when executed by a processor, implements the timing synchronization control method for the dual-axis scanning lidar system described in any one of the first aspects or the coordinate calculation method described in the second aspect.

[0030] In summary, this application provides a timing synchronization control method, system, medium, and coordinate calculation method for a dual-axis scanning lidar system, which has the following beneficial technical effects:

[0031] This application enables precise synchronization of a dual-axis scanning LiDAR system by controlling the scanning angle of the vertical scanning element based on the real-time rotational position signal of the horizontal scanning element. It provides a universal synchronization control method for LiDAR systems with different rotational speeds and numbers of reflective surfaces, exhibiting good portability and scalability. Furthermore, compared to non-repetitive dual-axis simultaneous scanning schemes, the point cloud generated in this application has consistent angular resolution and a stable data structure, directly compatible with mainstream LiDAR sensing algorithms and data processing pipelines, reducing algorithm adaptation costs. Attached Figure Description

[0032] Figure 1 The diagram shows an application scenario of the timing synchronization control method for the dual-axis scanning lidar system described in this application.

[0033] Figure 2 The diagram shown is a flowchart illustrating the timing synchronization control method of the dual-axis scanning lidar system described in this application embodiment.

[0034] Figure 3a and Figure 3b The image shown is a schematic diagram of the dual-axis scanning lidar system provided in the embodiments of this application.

[0035] Figures 4a to 4b The diagram shown is a schematic diagram of the mirror angle allocation of a dual-axis scanning lidar system provided in an embodiment of this application.

[0036] Figure 5 The diagram shows a timing schematic of a scanning imaging window and an adjacent scanning transition window provided in an embodiment of this application.

[0037] Figure 6 The diagram shown is a schematic diagram of the timing synchronization control system of the dual-axis scanning lidar system described in the embodiments of this application.

[0038] Component designation explanation Horizontal mirror rotation 100 Rotating mirror motor 101 Code disk 103 Vertical Mirror 104 galvanometer scanning motor 105 Rotating Mirror MCU 106 MCU 107 System-on-a-Chip 108 Vertical cavity surface-emitting laser 110 111 Single-photon avalanche diode Scanning imaging window 900 Scan switching window 901 Angle acquisition module 31 Window module 32 Synchronization Module 33 Detailed Implementation

[0039] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0040] It should be noted that, in the embodiments of this application, the words "specifically" or "for example" indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "specifically" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "specifically" or "for example" is intended to present the relevant concepts in a specific manner.

[0041] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0042] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0043] In the architecture of a dual-axis scanning lidar system, the coordinated operation of the vertical and horizontal scanning elements is crucial for achieving high-quality point cloud data. They must maintain precise coupling in both spatial trajectory and temporal sequence to synthesize a uniform and stable scanning pattern. However, existing technologies for dual-axis synchronous control mainly suffer from timing conflicts and low synchronization accuracy. On the one hand, the high-frequency reciprocating motion of the vertical mirror and the uniform rotation of the horizontal mirror, due to their large differences in inertia and motion modes, are prone to phase mismatch during acceleration and deceleration, leading to distortion or overlap of the point cloud at the edges. On the other hand, traditional control methods often employ open-loop or low-frequency closed-loop approaches, making it difficult to compensate for dynamic errors caused by mechanical vibration, temperature drift, and encoder feedback delays in real time. This results in a decrease in the joint pointing accuracy of the horizontal and vertical angles, ultimately causing misalignment between point cloud layers and uneven density distribution, thus limiting the performance of the lidar in long-range detection and high-precision mapping scenarios.

[0044] At least to address the above-mentioned problems, this application provides a timing synchronization control method for a dual-axis scanning lidar system. This method can control the scanning angle change of the vertical scanning element based on the real-time rotation position signal of the horizontal scanning element, thereby achieving precise synchronization of the dual-axis scanning lidar system. It provides a universal synchronization control method for lidar systems with different rotation speeds and different numbers of reflective surfaces, and has good portability and scalability.

[0045] Before providing a further detailed description of this application, the nouns and terms used in the embodiments of this application are explained. The nouns and terms used in the embodiments of this application shall be interpreted as follows:

[0046] VCSEL: Vertical-Cavity Surface-Emitting Laser, a type of surface-emitting semiconductor laser, often integrated in arrays as the emission source for lidar, supporting narrow pulse high-power output.

[0047] SPAD: Single-Photon Avalanche Diode, a high-sensitivity photodetector operating in Geiger mode, capable of detecting echo signals at the level of a single photon, and used in conjunction with a time-to-digital converter to achieve picosecond-level time-of-flight measurements.

[0048] SoC: System on Chip, which integrates the processor, memory, digital logic and interface circuits into a single chip, serving as the core computing and control unit of LiDAR.

[0049] MCU: Microcontroller Unit, an embedded control chip that integrates a processor, memory, and programmable input / output peripherals, used to execute control algorithms and system management tasks.

[0050] Trig I / O: Trigger Input / Output, is an interface used to receive external synchronization signals or output internal trigger events, enabling timing coordination between the LiDAR and external systems.

[0051] F sync: Frame Synchronization, a synchronization signal used to identify the start of a frame scan, enabling multiple LiDARs or sensors to maintain frame alignment in time.

[0052] S sync: Scanline Synchronization, a synchronization signal used to identify the start of a single-line scan, ensuring precise phase matching between horizontal and vertical scans on each line.

[0053] Single-line scan: A vertical array of points formed within the horizontal field of view constitutes a row of data in the 3D point cloud as the horizontal mirror rotates by a small angle each time. The starting time is identified by S sync.

[0054] INT: Interrupt, an asynchronous notification signal triggered by a peripheral or internal event, used to inform the master controller of priority events that require timely processing.

[0055] UART: Universal Asynchronous Receiver / Transmitter, a simple serial communication interface used for debugging, configuration, and low-speed data transmission between LiDAR and a host computer.

[0056] MIPI: Mobile Industry Processor Interface, a high-speed serial interface standard commonly used in LiDAR to transmit high-bandwidth point cloud data to an external processor in real time.

[0057] Figure 1 This diagram illustrates an application scenario of the timing synchronization control method for the dual-axis scanning lidar system described in this application. This method can be applied to, for example... Figure 1The dual-axis scanning lidar system shown. (As shown in the image.) Figure 1 As shown, this dual-axis scanning lidar system adopts a scanning architecture with a horizontal rotating mirror and a vertical tilting mirror, which are decoupled along their axes. It includes a tilting mirror for vertical beam scanning and a four-sided rotating mirror for horizontal beam scanning. The horizontal rotating mirror 100 is driven to rotate at a constant speed by a rotating mirror motor 101, achieving a 360° wide field of view scanning in the horizontal direction in conjunction with an encoder disk 103. The vertical tilting mirror 104 is driven by a galvanometer scanning motor 105 to change its scanning angle, achieving vertical field of view coverage. The rotating mirror MCU 106 and the tilting mirror MCU 107 independently control the horizontal rotating mirror 100 and the vertical tilting mirror 104, respectively. The rotating mirror MCU 106 receives feedback signals from the encoder disk 103 and maintains stable rotation speed of the horizontal rotating mirror 100 through closed-loop control; the tilting mirror MCU 107 precisely controls the scanning angle of the vertical tilting mirror 104. The two axes are coupled through an angle synchronization mechanism to synthesize a regular and uniform point cloud array in space.

[0058] The angle signal output from the encoder 103 is sent to the rotating mirror MCU 106 for speed closed-loop control, and the other is used as a synchronization reference to trigger a single-line scan. When the horizontal rotating mirror 100 rotates to a preset angle, the synchronization signal generator generates a line synchronization signal (S sync), starts a single-line scan, and notifies the on-chip system 108 to record the current horizontal angle value.

[0059] Furthermore, the System-on-Chip 108, acting as the central control unit, drives the vertical-cavity surface-emitting laser (VCSEL) array 110 to emit narrow-pulse laser beams based on the emission trigger signal generated by the timing synchronization module. After collimation, the laser beam is reflected sequentially by the horizontal rotating mirror 100 and the vertical tilting mirror 104, and then directed towards the target object. Subsequently, the target echo returns along the same optical path, converging through the vertical tilting mirror 104 and the horizontal rotating mirror 100 to the single-photon avalanche diode (SPD) array 111. The SPDs operate in Geiger mode, capable of detecting weak echoes at the single-photon level and outputting digital pulses. These pulses are shaped by a front-end quenching circuit and sent to a time-to-digital converter (TDC) to measure the time of flight (ToF) between laser emission and echo arrival, and the raw time data is transmitted to the System-on-Chip 108. The System-on-Chip 108 integrates a distance calculation unit, converting the TDC-measured time of flight into laser ranging values, and combining this with the current horizontal rotation angle and vertical tilt angle to generate three-dimensional point cloud coordinates (x, y, z). The solved point cloud data is output to an external processor in real time via a high-speed interface (such as MIPI).

[0060] Furthermore, the INT interrupt signal is used to handle high-priority events, including zero-point synchronization triggering of the code disk 103. When INT triggers the interrupt service routine of the rotating mirror MCU 106, the tilting mirror MCU 107, or the on-chip system 108, the system can perform safety protection actions such as laser shutdown and motor stop within microseconds.

[0061] The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] The following embodiments of this application provide a timing synchronization control method for a dual-axis scanning lidar system, which can be applied to, for example... Figure 1 The dual-axis scanning lidar system shown includes a vertical scanning element for vertical beam scanning and a horizontal scanning element for horizontal beam scanning. Figure 2 The diagram shows a flowchart illustrating the timing synchronization control method of the dual-axis scanning lidar system described in an embodiment of this application. Figure 2 As shown, the timing synchronization control method of the dual-axis scanning lidar system includes steps S1 to S3.

[0063] Step S1: Acquire the rotation position signal of the horizontal scanning element in real time.

[0064] In some embodiments, the rotational position signal of the horizontal scanning element is acquired in real time using a high-resolution angle sensor.

[0065] Step S2: Determine whether the horizontal scanning element is currently in the scanning imaging window or the scanning switching window based on the rotation position signal.

[0066] In some embodiments, the horizontal scanning element has N reflective surfaces, and the horizontal scanning element passes through N reflective surfaces when it rotates one revolution in the horizontal direction; the N reflective surfaces correspond to N scanning imaging windows and N scanning switching windows; the scanning switching windows correspond to the scanning transition region between adjacent reflective surfaces.

[0067] Furthermore, let the effective scanning starting angle corresponding to the i-th reflecting surface be . The effective scanning termination angle is Then the angle interval corresponding to the i-th scanning imaging window is The angle range corresponding to the scanning switching window between adjacent i-th and (i+1)-th reflecting surfaces is... .

[0068] Determining whether the horizontal scanning element is currently in a scanning imaging window or a scanning switching window based on the rotation position signal includes: obtaining the effective scanning angle ranges corresponding to N scanning imaging windows and the scanning transition angle ranges corresponding to M scanning switching windows; and determining the scanning imaging window sequence number or scanning switching window sequence number currently in which the horizontal scanning element is located based on the rotation position signal, the N effective scanning angle ranges, and the N scanning transition angle ranges.

[0069] That is, the rotation position signal φ of the horizontal scanning element is obtained in real time by a high-resolution angle sensor, and the horizontal scanning element can be determined in which scanning imaging window or which scanning switching window it is in based on φ.

[0070] Step S3: Based on the scanning imaging window or the scanning switching window, control the scanning angle jump of the vertical scanning element so that the scanning timing of the vertical scanning element and the horizontal scanning element is synchronized, and then output a laser trigger signal to control the laser transceiver module to emit light and receive light.

[0071] In some embodiments, if the horizontal scanning element is within the scanning imaging window, the vertical scanning element is controlled not to change its scanning angle, so that the vertical scanning element is stabilized at the scanning angle corresponding to the current scanning imaging window. That is, when the horizontal scanning element is within the scanning imaging window, the scanning angle of the vertical scanning element should be stabilized at a preset scanning angle corresponding to the current scanning imaging window.

[0072] In some embodiments, if the horizontal scanning element is within the scan switching window, the vertical scanning element is controlled to jump from the current scan angle to a target scan angle, where the target scan angle is the scan angle corresponding to the next scan imaging window adjacent to the current scan switching window. That is, when the horizontal scanning element is within the scan switching window, the vertical scanning element is controlled to jump from the current scan angle to the target scan angle, thereby ensuring that when the horizontal scanning element rotates to the next scan imaging window, the vertical scanning element remains stable at the scan angle corresponding to the current scan imaging window.

[0073] In some embodiments, multiple scanning angles are set for the vertical scanning element, each scanning angle corresponding to at least one scanning imaging window. For example, let the preset angle sequence of the vertical scanning element be denoted as {α1, α2, ..., α...}. M}, where M is the preset number of angles, then M ≤ N. When the horizontal scanning element is within the i-th scanning imaging window, the vertical scanning element should be stable at , where k(i) is the preset scanning angle index corresponding to the i-th imaging window. When the horizontal scanning element enters the i-th switching window, the vertical scanning element needs to switch from... Jump to ,in This is the preset scanning angle index corresponding to the (i+1)th scanning imaging window.

[0074] It is important to note that since M ≤ N, multiple scanning imaging windows may correspond to the same scanning angle. Therefore, when the horizontal scanning element rotates from the i-th scanning imaging window to the (i+1)-th scanning switching window, and If the scanning angle is the same, then the vertical scanning element does not actually experience a jump in scanning angle.

[0075] Furthermore, let the rotation period of the horizontal scanning element be... Then the time window occupied by each reflective surface = / N. Let the effective mechanical scanning angle range corresponding to a single reflecting surface be... If the total rotation angle between adjacent reflecting surfaces is 360° / N, then the scanning imaging window duration is... It can be determined by equation (1):

[0076]

[0077] The window switching duration T_switch can be determined by equation (2):

[0078]

[0079] That is, when the vertical scanning element changes its scanning angle, the change action should be within... The operation is performed within a specific time period, and the full-amplitude response time of the vertical scanning element is [not specified]. Must meet < The full-amplitude response time of the vertical scanning element refers to the total time required for the vertical scanning element (such as the tilting mirror and its drive mechanism) to deflect from its initial position to its maximum set angle (i.e., full-amplitude value) and stabilize at the target position. It comprehensively reflects the power output capability of the driver, the rotational inertia of the mechanical structure, and the dynamic response performance of the closed-loop control system. In dual-axis scanning lidar, this parameter directly determines the upper limit of the vertical field of view scanning frequency and the real-time performance of the point cloud data—the shorter the response time, the more vertical scanning cycles can be completed per unit time, thereby achieving higher vertical resolution or denser point cloud output while maintaining a constant horizontal rotation speed; conversely, if the full-amplitude response time is too long, it will not only limit the scanning frame rate, but may also cause the vertical tilting mirror to be unable to accurately follow the control waveform during high-speed reciprocating motion, resulting in misalignment between point cloud layers and uneven density distribution.

[0080] Furthermore, in some embodiments, the method provided in this application further includes: determining whether the vertical scanning element has jumped to the target scanning angle based on a preset jump-to-position threshold; wherein, when the absolute value of the difference between the current scanning angle and the target scanning angle is less than the jump-to-position threshold, it is determined that the vertical scanning element has jumped to the target scanning angle and a position signal is triggered.

[0081] In some embodiments, to precisely control the synchronization timing and ensure that when the horizontal scanning element is in the scanning imaging window, the vertical scanning element should be stable at the preset scanning angle corresponding to that scanning imaging window, this application determines whether the vertical scanning element has reached the target scanning angle by jumping to a threshold. Let the target angle of the vertical scanning element be... The current angle is Then e = Then, a drive signal is generated based on 'e' to drive the vertical scanning element to move towards the target angle. Let the jump to the position threshold be ε. When |e| is less than the preset position threshold ε, it is determined that the vertical scanning element has reached the position, and the position signal is triggered.

[0082] Furthermore, when the horizontal scanning element is within the scanning imaging window and the positioning signal is triggered, a laser trigger signal is output to control the laser transceiver module to emit and receive light. That is, in a dual-axis scanning lidar system, when this method is applied, laser beams are only allowed to be emitted when the horizontal scanning element is within the imaging window and the vertical scanning element is stable at the target angle. In other words, the light emission control logic of the laser transceiver module can actually be expressed by equation (3):

[0083] Furthermore, assuming the system requires the vertical point cloud layer misalignment height to not exceed Δh at the maximum laser detection distance R, then the angular stability requirement of the vertical scanning element within the scanning imaging window is... The rotational position feedback accuracy Δβ of the horizontal scanning element must satisfy equation (4).

[0084]

[0085]

[0086] Where L is the angular magnification factor of the optical system.

[0087] Then, after the horizontal scanning element rotates one revolution, that is, within the rotation cycle... Within the frame, the horizontal scanning element completes the scanning of N reflective surfaces, obtaining a total of N sets of point cloud data. If the vertical scanning element traverses all M preset angles, then one frame of data contains scanning information of M vertical partitions; if the vertical scanning element is fixed at a certain preset angle, then one frame of data contains multiple scanning information of only a single vertical partition.

[0088] Figure 3a and Figure 3b The image shown is a schematic diagram of the dual-axis scanning lidar system provided in an embodiment of this application. Figure 3a As shown, the horizontal rotating mirror rotates every time... It can be scanned. The horizontal field of view; the scanning method is linear array, angle-by-angle exposure; such as Figure 3a The black vertical column of dots shown represents the point cloud of the current time slot S-sync exposure; Figure 3a The light gray dots represent point clouds exposed in historical time slots. As the camera rotates and scans the entire horizontal field of view, the point cloud is gradually exposed, accumulating into a complete point cloud. Field of view.

[0089] Furthermore, the angle transition command for the vertical scan element is triggered by the SoC via the falling edge of F Sync. When one... Behind the field of view, when the falling edge of the F Sync signal is detected, the tilting mirror MCU sends a scan angle jump command, and the tilting mirror changes its angle to change the next... The field of view is positioned vertically (e.g., from 1 to 2). By rotating the horizontal mirror one full turn, four images can be stitched together. Complete field of view, such as Figure 3b As shown.

[0090] Figures 4a to 4b The diagram shown illustrates the mirror angle allocation of a dual-axis scanning lidar system provided in an embodiment of this application. Figures 4a to 4b As shown, a horizontal four-sided rotating mirror rotates 360 degrees in one revolution. The mirror has four reflecting surfaces, so each reflecting surface occupies 90 degrees of the rotation angle. Assuming each reflecting surface needs to scan a 120° horizontal field of view (FOV), achieved by rotating the mirror along its axis, then according to the law of reflection (incident angle = exit angle), the mirror's axis rotates 60 degrees when scanning a 120° horizontal FOV. Therefore, within one reflecting surface, 60 degrees constitutes the scanning imaging window 90°, while the remaining rotation angle forms the scanning switching window 901. Within the scanning switching window 901, the vertically tilting mirror completes the angle jump. The final complete field of view after one revolution of the horizontal rotating mirror can be found in [reference needed]. Figure 3b As shown.

[0091] Continue reading Figure 1 As shown, Figure 5 This diagram illustrates the timing of a scanning imaging window and an adjacent scanning transition window, as provided in an embodiment of this application. Figure 5 As shown, when the F Sync signal is triggered, the rotating mirror MUC responds and outputs a signal to the rotating mirror encoder, causing the encoder to control the horizontal rotating mirror angle to rotate uniformly. Within a single frame exposure cycle, multiple Ssync signals trigger a single-line scan to start, completing the angle-by-angle exposure of the linear array within a full horizontal field of view (see [reference]). Figure 3a (Point cloud exposure in the image). After a horizontal field of view scan is completed, the mirror MCU responds to the falling edge of the F Sync signal and enters the scan switching window. At this time, the mirror MCU controls the galvanometer motor signal to adjust the mirror angle from... Switch to Afterwards, a new FSync signal is triggered, initiating the second horizontal field of view scan. The complete field of view after the horizontal rotating mirror has completed one full rotation can be found in [reference needed]. Figure 3b As shown.

[0092] In some embodiments, this application also provides a coordinate calculation method, which is applied to a dual-axis scanning lidar system after timing synchronization control using the method described in any of the above embodiments. The method includes: using a laser transceiver module to emit and receive light to obtain a laser ranging value; the laser ranging value corresponds to the total optical path of the beam from the laser emission point through the vertical scanning element and the horizontal scanning element to the target point; and calculating the three-dimensional coordinates of the target point based on the laser ranging value, the current rotation position of the horizontal scanning element, and the current scanning angle of the vertical scanning element.

[0093] In some embodiments, assuming that the dual-axis scanning lidar system meets ideal reflection conditions and the positional relationship of each optical element has been predetermined through system calibration, the specific calculation process is as follows:

[0094] The system coordinate system is established as follows: the origin O is the intersection of the horizontal projection of the rotating mirror (horizontal) rotation axis and the center of the reflecting surface of the pendulum mirror (vertical). The direction of the rotating mirror rotation axis is the Z-axis (vertically upward is positive). The direction in the horizontal plane that is perpendicular to the rotating mirror rotation axis and points to the target detection area is the X-axis. The direction in the horizontal plane that is perpendicular to the X-axis is the Y-axis, forming a right-hand rectangular coordinate system O-XYZ.

[0095] Assume the light emission point of the laser transceiver module is located at coordinate P. tx = (x tx , y tx , z tx This position is determined by the system's mechanical structure. Let the rotation axis of the pendulum mirror be located at coordinate (x...). v , y v , z v Let θv be the instantaneous mechanical angle of the pendulum mirror. When θv = 0, the normal direction of the pendulum mirror points to the positive Z-axis. Let the rotation axis of the rotating mirror coincide with the Z-axis, and let θh be the instantaneous rotation angle of the rotating mirror. When θh = 0, the normal direction of the first reflecting surface of the rotating mirror points to the positive X-axis.

[0096] When the laser transceiver module emits a laser beam, the propagation path of the laser beam can be divided into the following three segments:

[0097] The first paragraph begins at the laser emission point P. tx Let the coordinates of the projection of the center point Pv of the reflecting surface of the pendulum mirror onto the axis of rotation of the pendulum mirror be (x...). v , y v , z vSince the pendulum mirror rotates around its axis, the position of Pv changes with the angle of the pendulum mirror, but within a small angle range it can be approximated as a fixed point or calculated precisely through geometric relationships. For simplicity, this example assumes that Pv is a fixed point, and its coordinates are obtained from system calibration.

[0098] The second section extends from the center Pv of the pendulum mirror's reflecting surface to the center Ph of the rotating mirror's reflecting surface. The beam's direction changes after reflection by the pendulum mirror; the direction of reflection is determined by the instantaneous normal direction of the pendulum mirror. (See reference...) Figure 4a As shown. Let the unit vector of the normal to the pendulum mirror be nv. When the pendulum mirror swings around the X-axis, we have nv = (0, sinθ_v, cosθ_v). Then let the direction vector of the incident ray be iv = Pv - P. tx After normalization, it becomes ûv. According to the law of reflection, the direction vector rv of the outgoing ray should satisfy: rv = ûv-2(ûv·nv)nv.

[0099] The emitted ray points towards the center Ph of the rotating mirror's reflecting surface. The position of Ph changes as the mirror rotates, and can be expressed as: Ph = (R·cosθh, R·sinθh, zh). Here, R is the horizontal distance from the center of the reflecting surface to the mirror's rotation axis, and zh is the height of the center of the reflecting surface; both are system structural parameters. θh is the instantaneous rotation angle of the mirror.

[0100] The third segment runs from the center Ph of the rotating mirror's reflecting surface to the target point P. target The light beam is reflected by the rotating mirror and then directed toward the target. The direction of reflection is determined by the instantaneous normal direction of the rotating mirror. Let the unit vector of the normal to the reflecting surface of the rotating mirror be nh. For a reflecting surface parallel to the axis of rotation, nh lies in the horizontal plane, and its expression is: nh = (cosθh, sinθh, 0).

[0101] Let the direction vector of the incident ray to the rotating mirror be ih = Ph - Pv (here, the reversibility of the light path needs to be considered, and in actual calculation, it should point from Pv to Ph), which is normalized to ûh. Then, according to the law of reflection, the direction vector rh of the outgoing ray satisfies: rh = ûh - 2(ûh·nh)nh.

[0102] Let the laser ranging value be d, which corresponds to the distance from the laser emission point P. tx After tilting and rotating the mirror, the target point P is reached. target The total optical path. Because P tx The distances from Pv to P and from Pv to Ph can be calculated using coordinates. Let the sum of these two distances be d. fixed Then, from the center Ph of the rotating mirror's reflecting surface to the target point P... target distance d target For: d target = d- d fixed .

[0103] Then the target point P target The coordinates of P can be calculated by the following formula: target = Ph + d target · rh.

[0104] Expanding the above expression, we get P. target Explicit expressions for the instantaneous mechanical angle θv of the pendulum mirror, the instantaneous rotation angle θh of the rotating mirror, and the laser ranging value d. In practical engineering implementation, this calculation process is usually completed in real time in the signal processing unit, and the required system parameters (P) are calculated. tx (Pv, R, zh, etc.) are obtained through factory calibration and stored in the SoC.

[0105] In summary, this application can control the scanning angle change of the vertical scanning element based on the real-time rotational position signal of the horizontal scanning element, achieving precise synchronization of a dual-axis scanning LiDAR system. It provides a universal synchronization control method for LiDAR systems with different rotational speeds and numbers of reflective surfaces, exhibiting good portability and scalability. Furthermore, compared to non-repetitive dual-axis simultaneous scanning schemes, the point cloud generated in this application has consistent angular resolution and a stable data structure, directly compatible with mainstream LiDAR sensing algorithms and data processing pipelines, reducing algorithm adaptation costs.

[0106] The scope of protection for the timing synchronization control method and / or coordinate calculation method of the dual-axis scanning lidar system in this application is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, subtracting, or replacing steps in the prior art based on the principles of this application is included within the scope of protection of this application.

[0107] Figure 6 The diagram shown is a schematic representation of the timing synchronization control system of the dual-axis scanning lidar system described in an embodiment of this application. Figure 6 As shown, the timing synchronization control system of the dual-axis scanning lidar system of this application includes:

[0108] Angle acquisition module 31 is configured to acquire the rotational position signal of the horizontal scanning element in real time;

[0109] Window module 32 is configured to determine, based on the rotation position signal, whether the horizontal scanning element is currently in a scanning imaging window or a scanning switching window;

[0110] The synchronization module 33 is configured to control the scanning motion of the vertical scanning element based on the scanning imaging window or the scanning switching window, so that the scanning timing of the vertical scanning element and the horizontal scanning element are synchronized, and then output a laser trigger signal to control the laser transceiver module to emit light and receive light.

[0111] The structure and principle of the angle acquisition module 31, window module 32 and synchronization module 33 correspond one-to-one with the steps in the above method, so they will not be described again here.

[0112] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, or methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of apparatuses or modules or units may be electrical, mechanical, or other forms.

[0113] The modules / units described as separate components may or may not be physically separate. The components shown as modules / units may or may not be physical modules; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected to achieve the objectives of the embodiments of this application, depending on actual needs. For example, the functional modules / units in the various embodiments of this application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0114] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0115] This application also provides a computer-readable storage medium storing a computer program. When executed by a processor, the program implements the timing synchronization control method or coordinate calculation method of the dual-axis scanning lidar system described in any embodiment of this application. Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing a processor. The program can be stored in a computer-readable storage medium, which is a non-transitory medium, such as random access memory, read-only memory, flash memory, hard disk, solid-state hard disk, magnetic tape, floppy disk, optical disk, and any combination thereof. The storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (DVD)), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0116] As used in this specification, the terms "component," "module," "system," etc., are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated, applications running on computing devices and computing devices can both be components. One or more components may reside in a process and / or an execution thread, and components may be located on a single computer and / or distributed among two or more computers. Furthermore, these components can be executed from various computer-readable media on which various data structures are stored. Components can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from two components interacting with another component between a local system, a distributed system, and / or a network, such as the Internet interacting with other systems via signals).

[0117] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0118] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A timing synchronization control method for a dual-axis scanning lidar system, characterized in that, The dual-axis scanning lidar system includes a vertical scanning element for vertical beam scanning and a horizontal scanning element for horizontal beam scanning; the method includes: The rotational position signal of the horizontal scanning element is acquired in real time; Based on the rotation position signal, it is determined whether the horizontal scanning element is currently in the scanning imaging window or the scanning switching window; Based on the scanning imaging window or the scanning switching window, the scanning angle of the vertical scanning element is controlled to synchronize the scanning timing of the vertical scanning element with that of the horizontal scanning element, and then a laser trigger signal is output to control the laser transceiver module to emit light and receive light.

2. The timing synchronization control method for a dual-axis scanning lidar system according to claim 1, characterized in that, Controlling the scanning motion of the vertical scanning element based on the scanning imaging window or the scanning switching window includes: If the horizontal scanning element is within the scanning imaging window, the scanning angle of the vertical scanning element is controlled to remain unchanged, so that the vertical scanning element is stabilized at the scanning angle corresponding to the current scanning imaging window. If the horizontal scanning element is within the scanning switching window, the vertical scanning element is controlled to jump from the current scanning angle to the target scanning angle, where the target scanning angle is the scanning angle corresponding to the next scanning imaging window adjacent to the current scanning switching window.

3. The timing synchronization control method for a dual-axis scanning lidar system according to claim 2, characterized in that, The method further includes: Based on a preset jump-to-position threshold, it is determined whether the vertical scanning element has jumped to the target scanning angle; wherein, when the absolute value of the difference between the current scanning angle and the target scanning angle is less than the jump-to-position threshold, it is determined that the vertical scanning element has jumped to the target scanning angle and a position signal is triggered.

4. The timing synchronization control method for a dual-axis scanning lidar system according to claim 3, characterized in that, The method further includes: When the horizontal scanning element is within the scanning imaging window and the positioning signal is triggered, a laser trigger signal is output to control the laser transceiver module to emit light and receive light.

5. The timing synchronization control method for a dual-axis scanning lidar system according to claim 1, characterized in that, The horizontal scanning element has N reflective surfaces, and the horizontal scanning element passes through N reflective surfaces when it rotates one revolution in the horizontal direction; the N reflective surfaces correspond to N scanning imaging windows and N scanning switching windows; the scanning switching windows correspond to the scanning transition area between adjacent reflective surfaces.

6. The timing synchronization control method for a dual-axis scanning lidar system according to claim 5, characterized in that, Determining whether the horizontal scanning element is currently in the scanning imaging window or scanning switching window based on the rotation position signal includes: Obtain the effective scanning angle range corresponding to the N scanning imaging windows and the scanning transition angle range corresponding to the M scanning switching windows; Based on the rotation position signal, the N effective scanning angle ranges and the N scanning transition angle ranges, the current scanning imaging window sequence number or scanning switching window sequence number of the horizontal scanning element is determined.

7. The timing synchronization control method for a dual-axis scanning lidar system according to claim 1, characterized in that, The method further includes: Multiple scanning angles are set for the vertical scanning element, and each scanning angle corresponds to at least one scanning imaging window.

8. A coordinate calculation method, characterized in that, The method is applied to a dual-axis scanning lidar system after timing synchronization control is performed using the method described in any one of claims 1 to 7; the method includes: A laser transceiver module is used for emission and reception to obtain laser ranging values; the laser ranging values ​​correspond to the total optical path of the beam from the laser emission point through the vertical scanning element and the horizontal scanning element to the target point. The three-dimensional coordinates of the target point are calculated based on the laser ranging value, the current rotation position of the horizontal scanning element, and the current scanning angle of the vertical scanning element.

9. A timing synchronization control system for a dual-axis scanning lidar system, characterized in that, The dual-axis scanning lidar system includes a vertical scanning element for vertical beam scanning and a horizontal scanning element for horizontal beam scanning; the system includes: An angle acquisition module is configured to acquire the rotational position signal of the horizontal scanning element in real time; The window module is configured to determine whether the horizontal scanning element is currently in a scanning imaging window or a scanning switching window based on the rotation position signal; The synchronization module is configured to control the scanning angle jump of the vertical scanning element based on the scanning imaging window or the scanning switching window, so that the scanning timing of the vertical scanning element and the horizontal scanning element are synchronized, and then output a laser trigger signal to control the laser transceiver module to emit light and receive light.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the timing synchronization control method of the dual-axis scanning lidar system according to any one of claims 1 to 7 or the coordinate calculation method according to claim 8.

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