Intra-exo frame synchronization signal irregular collaborative following method of laser radar

Abstract

The application aims to provide an irregular cooperative following method for inner and outer frame synchronization signals of a laser radar, which comprises the following steps: system initialization, setting of a frame rate, setting of a master-slave mode, setting of an inner and outer frame synchronization delay, setting of a flow starting, and following light emission and image output, so as to ensure consistent image output timing of the whole vehicle laser radar, facilitate heterogeneous data fusion of a cooperative camera and other sensors, and enhance the reliability and practicability of the laser radar.

Description

Technical Field

[0001] This invention relates to the fields of intelligent sensors and lidar technology, specifically to a method for irregular cooperative following of inner and outer frame synchronization signals in lidar. Background Technology

[0002] With the implementation of intelligent assisted driving, the vehicle's electronic and electrical architecture is evolving from a distributed model to a "domain control + centralized" model. The domain controller (ADCU / MDC) needs to process data from various heterogeneous sensors such as cameras, millimeter-wave radar, and lidar simultaneously on the same time base in order to complete fusion positioning, dynamic target tracking, and high-precision map matching.

[0003] OEMs typically mandate in vehicle-level timing specifications that the phase error between the "start time" of each sensor output frame and the vehicle synchronization pulse is less than a certain range; within the same synchronization domain, there must be no offset of more than a certain time between the LiDAR's internal scanning frame (intra-frame) and the external synchronization pulse (inter-frame), otherwise it will lead to "ghost images" or "target loss" during multi-sensor fusion, as well as high-precision map matching failure, resulting in a lateral positioning error of >10 cm.

[0004] Existing technologies typically employ a "fixed frequency division + static delay" scheme: the LiDAR internally divides the external synchronization pulse once via an FPGA / MCU, then releases the point cloud frame after a fixed delay. This scheme can meet ±1 ms error under steady-state laboratory conditions, but it has the following drawbacks in real-world vehicle scenarios:

[0005] 1. Unable to compensate for accumulated phase drift; error > ±2 ms after long-term operation.

[0006] 2. When the vehicle experiences momentary jitter due to link switching or clock discipline, the fixed delay logic cannot keep up quickly, causing one or more frames of data to be judged as "timeout invalid" by the domain controller, triggering the fusion module to downgrade the frame and degrading the vehicle's functions.

[0007] 3. When the vehicle frame synchronization fails or disappears, the lidar cannot continue to follow, and the vehicle's external sensing fails.

[0008] To address the aforementioned challenges, this invention provides a method for irregular cooperative following of inner and outer frame synchronization signals in lidar. Summary of the Invention

[0009] The purpose of this invention is to provide a method for irregular collaborative following of inner and outer frame synchronization signals of a LiDAR, which ensures the consistency of the LiDAR image output timing of the entire vehicle while facilitating the fusion of heterogeneous data from sensors such as cameras. To achieve the above objective, the technical solution of this invention specifically includes the following steps:

[0010] S101: System initialization;

[0011] S102: Set the frame rate;

[0012] S103: Set master-slave mode;

[0013] S104: Set the synchronization delay between internal and external frames;

[0014] S105: Configure start-up flow;

[0015] S106: Follow the lighting to produce the image.

[0016] In step S101, the system is initialized. Timer 0 is set to PWM pulse output mode, the frequency setting is retained, the timing accuracy is set to 1ms, and it is disabled by default. Timer 1 is set as a delay control register, the timing accuracy is set to microsecond level, and it is used for delay control of internal and external synchronization signals. It is disabled by default.

[0017] In S102, the frame rate is set and associated with the delay range of timer 1. Specifically, the association is as follows: multiple scale detection points are set according to the frame rate. At the single frame monitoring point, a period of 1.5 times is used for monitoring to trigger instantaneous frame loss. At the multi-frame monitoring point, a period of (n+0.5) times is used for monitoring, where n>1, to trigger continuous frame loss.

[0018] In S103, a master-slave mode is set. When the lidar is working in master mode, the lidar will take the first external synchronization signal after the current start signal as the starting point and will not follow it again. When the lidar is working in slave mode, when the external synchronization signal is an irregular periodic signal, the lidar will output a PWM wave after the internal and external frame synchronization delay based on the external synchronization signal after the current start signal, thus completing the slave mode following.

[0019] In S104, the internal and external frame synchronization delay is set and takes effect in slave mode. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal.

[0020] In S105, the current is started, the timers 0 and 1 in S101 are enabled, and the laser of the lidar is turned on to enter the lighting preparation state.

[0021] In S106, during the follow-up lighting and image output process, when the LiDAR is in master mode, it will listen to the first external frame synchronization signal and will not listen to subsequent signals. The LiDAR will autonomously output light based on the first external frame synchronization signal. When the LiDAR is in slave mode, it will listen to each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode. After the delay set in S104, the internal frame synchronization signal will be triggered, and the PWM will be set to normal mode. When the external frame synchronization signal disappears, the LiDAR will continue to output light and image based on the last external frame synchronization signal. When the external frame synchronization signal is restored, the LiDAR will repeat the above-mentioned follow-up process.

[0022] Furthermore, in the above S101, the output mode of the PWM can be configured according to the triggering method of the laser. When the laser is edge-triggered, the PWM no longer focuses on the duty cycle configuration. When the laser is level-triggered, the duration of the PWM level needs to meet the triggering pulse width of the laser.

[0023] Furthermore, in the above S106, the periodicity of the external frame synchronization signal is not considered in the mode, thus enabling the tracking of irregular external frame synchronization signals. Attached Figure Description

[0024] Figure 1 This is the overall flowchart of the present invention;

[0025] Figure 2 This is a timing diagram for synchronizing internal and external frames; Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] As attached Figure 1 As shown, the purpose of this invention is to provide a method for irregular collaborative following of inner and outer frame synchronization signals of a LiDAR, which ensures the consistency of the LiDAR image output timing of the entire vehicle while facilitating the heterogeneous data fusion of sensors such as cameras. To achieve the above objective, the technical solution of this invention specifically includes the following steps:

[0028] S101: System initialization;

[0029] S102: Set the frame rate;

[0030] S103: Set master-slave mode;

[0031] S104: Set the synchronization delay between internal and external frames;

[0032] S105: Configure start-up flow;

[0033] S106: Follow the lighting to produce the image.

[0034] In step S101, the system is initialized. Timer 0 is set to PWM pulse output mode, the frequency setting is retained, the timing accuracy is set to 1ms, and it is disabled by default. Timer 1 is set as a delay control timer, the timing accuracy is set to microsecond level, and it is used for delay control of internal and external synchronization signals. It is disabled by default.

[0035] In S102, the frame rate is set and associated with the delay range of timer 1. Specifically, the association is as follows: multiple scale detection points are set according to the frame rate. At the single frame monitoring point, a period of 1.5 times is used for monitoring to trigger instantaneous frame loss. At the multi-frame monitoring point, a period of (n+0.5) times is used for monitoring, where n>1, to trigger continuous frame loss.

[0036] In S103, a master-slave mode is set. When the lidar is working in master mode, the lidar will take the first external synchronization signal after the current start signal as the starting point and will not follow it again. When the lidar is working in slave mode, when the external synchronization signal is an irregular periodic signal, the lidar will output a PWM wave after the internal and external frame synchronization delay based on the external synchronization signal after the current start signal, thus completing the slave mode following.

[0037] In S104, according to the appendix Figure 2 Set the internal and external frame synchronization delay, which takes effect in slave mode. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal.

[0038] In S105, the current is started, the timers 0 and 1 in S101 are enabled, and the laser of the lidar is turned on to enter the lighting preparation state.

[0039] In S106, during the follow-up lighting and image output process, when the LiDAR is in master mode, it will listen to the first external frame synchronization signal and will not listen to subsequent signals. The LiDAR will autonomously output light based on the first external frame synchronization signal. When the LiDAR is in slave mode, it will listen to each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode. After the delay set in S104, the internal frame synchronization signal will be triggered, and the PWM will be set to normal mode. When the external frame synchronization signal disappears, the LiDAR will continue to output light and image based on the last external frame synchronization signal. When the external frame synchronization signal is restored, the LiDAR will repeat the above-mentioned follow-up process.

[0040] Furthermore, in the above S101, the output mode of the PWM can be configured according to the triggering method of the laser. When the laser is edge-triggered, the PWM no longer focuses on the duty cycle configuration. When the laser is level-triggered, the duration of the PWM level needs to meet the triggering pulse width of the laser.

[0041] Furthermore, in the above S106, the periodicity of the external frame synchronization signal is not considered in the mode, thus enabling the tracking of irregular external frame synchronization signals.

[0042] Specific Implementation Example 1: When the external frame synchronization signal is a periodic signal, the internal frame synchronization signal is triggered after the lidar receives the external frame synchronization signal and then after a fixed delay, so as to achieve periodic delay triggering.

[0043] The specific execution process is as follows:

[0044] In step S101, the system is initialized. Timer 0 is set to PWM pulse output mode, the frequency setting is retained, the timing accuracy is set to 1ms, and it is disabled by default. Timer 1 is set as a delay control timer, the timing accuracy is set to microsecond level, and it is used for delay control of internal and external synchronization signals. It is disabled by default.

[0045] In S102, the frame rate is set and associated with the delay range of timer 1. Specifically, the association is as follows: multiple scale detection points are set according to the frame rate. At the single frame monitoring point, a period of 1.5 times is used for monitoring to trigger instantaneous frame loss. At the multi-frame monitoring point, a period of (n+0.5) times is used for monitoring, where n>1, to trigger continuous frame loss.

[0046] In S103, the lidar is set to slave mode. When the lidar is working in slave mode, and the external synchronization signal is an irregular periodic signal, the lidar will output a PWM wave according to the external synchronization signal after the start-up, after the internal and external frame synchronization delay, to complete the follow-up in slave mode.

[0047] In S104, according to the appendix Figure 2 Set the internal and external frame synchronization delay. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal.

[0048] In S105, the current is started, the timers 0 and 1 in S101 are enabled, and the laser of the lidar is turned on to enter the lighting preparation state.

[0049] In S106, during the follow-up illumination and image output process, when the lidar is in slave mode, it will monitor each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode. After the delay set in S104, the internal frame synchronization signal is triggered, and the PWM is set to normal mode. When the external frame synchronization signal disappears, the lidar continues to illuminate and output the image based on the last external frame synchronization signal. When the external frame synchronization signal is restored, the lidar repeats the above-mentioned follow-up process.

[0050] Specific Implementation Example 2: When the external frame synchronization signal is a non-periodic signal, the internal frame synchronization signal is triggered after the lidar receives the external frame synchronization signal and then after a fixed delay, so as to achieve non-periodic delay triggering.

[0051] The specific execution process is as follows:

[0052] In step S101, the system is initialized. Timer 0 is set to PWM pulse output mode, the frequency setting is retained, the timing accuracy is set to 1ms, and it is disabled by default. Timer 1 is set as a delay control timer, the timing accuracy is set to microsecond level, and it is used for delay control of internal and external synchronization signals. It is disabled by default.

[0053] In S102, the frame rate is set and associated with the delay range of timer 1. Specifically, the association is as follows: multiple scale detection points are set according to the frame rate. At the single frame monitoring point, a period of 1.5 times is used for monitoring to trigger instantaneous frame loss. At the multi-frame monitoring point, a period of (n+0.5) times is used for monitoring, where n>1, to trigger continuous frame loss.

[0054] In S103, the lidar is set to slave mode. When the lidar is working in slave mode, and the external synchronization signal is an irregular periodic signal, the lidar will output a PWM wave according to the external synchronization signal after the start-up, after the internal and external frame synchronization delay, to complete the follow-up in slave mode.

[0055] In S104, according to the appendix Figure 2 Set the internal and external frame synchronization delay. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal.

[0056] In S105, the current is started, the timers 0 and 1 in S101 are enabled, and the laser of the lidar is turned on to enter the lighting preparation state.

[0057] In S106, during the follow-up illumination and image output process, when the lidar is in slave mode, it will monitor each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode. After the delay set in S104, the internal frame synchronization signal is triggered, and the PWM is set to normal mode. When the external frame synchronization signal disappears, the lidar continues to illuminate and output the image based on the last external frame synchronization signal. When the external frame synchronization signal is restored, the lidar repeats the above-mentioned follow-up process.

[0058] Specific Implementation Example 3: When the external synchronization signal is a periodic signal but has errors, the lidar is required to fill the errors in the frame synchronization signal after receiving the external frame synchronization signal, adaptively set the time delay, and trigger the internal frame synchronization signal to achieve periodic delay triggering.

[0059] The specific execution process is as follows:

[0060] In S101, the system is initialized. Timer 0 is set to PWM pulse output mode, the frequency setting is retained, the timing accuracy is set to 1ms, and the default state is disabled. Timer 1 is set as a delay control timer, the timing accuracy is set to microsecond level, and it is used for delay control of internal and external synchronization signals. The default state is disabled. At the same time, the external frame synchronization signal period detection function is added.

[0061] In S102, the frame rate is set and associated with the delay range of Timer 1. Specifically, the association is as follows: multiple scale detection points are set according to the frame rate. At the single frame monitoring point, a period of 1.5 times is used for monitoring to trigger instantaneous frame loss. At the multi-frame monitoring point, a period of (n+0.5) times is used for monitoring, where n>1, to trigger continuous frame loss. The period of the external frame synchronization signal is obtained for the adaptive delay setting in S106.

[0062] In S103, the lidar is set to slave mode. When the lidar is working in slave mode, and the external synchronization signal is an irregular periodic signal, the lidar will output a PWM wave according to the external synchronization signal after the start-up, after the internal and external frame synchronization delay, to complete the follow-up in slave mode.

[0063] In S104, according to the appendix Figure 2 Set the internal and external frame synchronization delay. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal.

[0064] In S105, the current is started, the timers 0 and 1 in S101 are enabled, and the laser of the lidar is turned on to enter the lighting preparation state.

[0065] In S106, during the follow-up illumination and image output process, when the LiDAR is in slave mode, it will monitor each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode, and the trigger point of the external signal will be recorded. Based on the acquired external frame synchronization signal period, the external frame synchronization signal will be calibrated, and the delay set in S104 will be increased or decreased to achieve adaptive delay setting. After the delay ends, the internal frame synchronization signal is triggered, and the PWM is set to normal mode. When the external frame synchronization signal disappears, the LiDAR will continue to illuminate and output the image based on the last external frame synchronization signal. When the external frame synchronization signal recovers, the LiDAR will repeat the above-mentioned follow-up process.

[0066] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for irregular cooperative following of inner and outer frame synchronization signals in a lidar system, characterized in that, Includes the following steps: S101: System initialization; S102: Set the frame rate; S103: Set master-slave mode; S104: Set the synchronization delay between internal and external frames; S105: Configure start-up flow; S106: Follow the lighting to produce an image; In S102, the frame rate is set and correlated with the timer's delay range. Specifically, multiple scale detection points are set based on the frame rate. At a single-frame monitoring point, a 1.5x period is used for monitoring to trigger instantaneous frame loss. At multiple-frame monitoring points, a (n+0.5)x period is used for monitoring, where n>1, to trigger continuous frame loss. In S104, the internal and external frame synchronization delay is set and takes effect in slave mode. This delay is configured according to timing constraints and has a precision of microseconds. When the external frame synchronization signal is triggered, the above delay needs to be added according to the actual timing requirements to control the triggering timing of the internal frame synchronization signal. In S106, the image is generated following the lighting. When the LiDAR is in master mode, it will listen to the first external frame synchronization signal and will not listen to subsequent signals. The LiDAR will autonomously illuminate based on the first external frame synchronization signal. When the LiDAR is in slave mode, it will listen to each external frame synchronization signal. When the external frame synchronization signal is triggered, the PWM will be set to forced output mode. After the delay set in S104 above, the internal frame synchronization signal will be triggered, and the PWM will be set to normal mode. When the external frame synchronization signal disappears, the LiDAR will continue to illuminate and produce an image based on the last external frame synchronization signal. When the external frame synchronization signal is restored, the LiDAR will repeat the above following process.

Images