Adaptive acquisition and storage delay control method for echo signals of water depth sounding laser radar

Abstract

The application discloses a water depth detection laser radar echo signal adaptive acquisition and storage delay control method design, which comprises the following steps: 1, the ground end sends a laser radar initialization command to the laser radar main control module through a 4G module; 2, when the laser radar reaches a specified position, the ground end opens the laser radar through the 4G module, the laser radar POS system sends height data to the laser radar high-speed acquisition and storage module, the high-speed acquisition and storage module pre-processes according to the height data, and performs rough delay adjustment; 3, the adaptive delay module detects the position of the maximum value of the data, and performs corresponding delay adjustment to complete fine adjustment and high-speed acquisition and storage operation; 4, the high-speed acquisition and storage system judges the height data sent by the POS system module, and when the height data exceeds a certain range, the third step operation is automatically performed to ensure the integrity of the water surface and water bottom echo.

Description

Technical Field

[0001] This invention relates to the field of lidar, and in particular to the design of an adaptive acquisition and storage delay control method for water depth detection lidar echo signals. Background Technology

[0002] Currently, a crucial component in the development of depth-sensing lidar is the high-speed echo signal acquisition and data storage system. A major challenge of this system is determining the acquisition and storage time. Theoretically, with a sufficiently high sampling frequency and large enough storage space, it is possible to completely acquire and store all echo and noise data from the laser's on-time to off-time. However, in practice, due to storage space limitations, it is impossible to store all data. Therefore, how to store complete and valid echo data is extremely critical.

[0003] Patent CN 113608195A discloses a method for decomposing and measuring depth using full-waveform data from a lidar system, but it does not explain how to acquire the full-waveform data of the detected water area. Patent CN 103197321A discloses a full-waveform lidar system, but it requires a direct connection to a host computer, and the overall equipment is relatively large. Patent US 11467269B2 discloses a design for a laser detection and ranging device for detecting objects underwater, but the time delay between emitting the laser beam and detecting the reflected laser beam is uncertain, making it impossible to mount the device on other variable-height platforms.

[0004] As revealed by the publicly published patents listed above, no patent, domestic or international, describes how a depth-sensing lidar determines the effective echo signal acquisition and data storage time. Therefore, this invention proposes a method for adaptive acquisition and storage delay control of echo signals from a depth-sensing lidar. When the lidar's height above the water surface changes, the acquisition and storage channel delay time is automatically adjusted, ensuring the integrity of both surface and bottom echo data. This allows the lidar to store complete and effective echo data within a limited solid-state drive. Because it can address the impact of lidar height, the lidar can be mounted on different platforms, saving the complex manual adjustments required. Summary of the Invention

[0005] This invention discloses an adaptive acquisition and storage delay control method for water depth sounding lidar echo signals, which mainly includes the following steps:

[0006] First, the ground terminal sends a lidar initialization command to the lidar main control module via a 4G module.

[0007] Second, once the lidar reaches the designated location, the ground terminal activates the lidar via a 4G module. The lidar POS system then sends altitude data to the lidar high-speed acquisition and storage module. The high-speed acquisition and storage module preprocesses this altitude data and performs a coarse delay adjustment.

[0008] Third, the adaptive delay module detects the location of the maximum data value and makes corresponding delay adjustments to complete fine-tuning, and performs high-speed acquisition and storage operations.

[0009] Fourth, the high-speed acquisition and storage system judges the height data sent by the POS system module. When this height data exceeds a certain range, it will automatically perform the third step to ensure the integrity of the water surface and bottom echoes.

[0010] The ground-based terminal includes host computer software on mobile phones and computers, capable of communicating with the lidar. This includes remotely controlling the lidar's initialization and startup, and sending and receiving the operating status and related parameters of the PMT (photomultiplier tube) detection module, laser module, high-speed acquisition and storage module, and POS (position and orientation system) module controlled by the lidar master controller.

[0011] The aforementioned lidar main control module integrates the PMT control module, laser control module, high-speed acquisition and storage control module, and POS system control module into one unit, and can send control commands to each module in real time.

[0012] The high-speed acquisition and storage module can convert the analog signals detected by the PMT detection module into digital signals, and can change the acquisition pulse width and delay time, and finally store them in the solid-state drive at high speed. It can also store the POS data required for lidar echo data processing.

[0013] The POS system module described above is capable of obtaining the required GPS and IMU data, and can acquire and transmit altitude data.

[0014] The beneficial effects of this invention are: (1) This invention achieves coarse and fine adjustment of channel delay through an adaptive delay module, overcoming the problem of uncertain echo signal return time caused by continuous changes in altitude, and realizing complete storage of surface and bottom echo data and water body data. (2) This invention considers the different altitudes of the lidar platform, enabling this lidar to be mounted on platforms such as UAVs, manned aircraft, and unmanned ships. (3) This invention uses a POS system to automatically acquire altitude data, which can overcome the problem of inaccurate manual altitude measurement, save the complex operation of repeated manual adjustments, and make the lidar easier to use. (4) This invention ensures that each set of stored data contains complete echo data, solving the problem of excessive data volume in traditional methods, reducing storage space, and thus reducing the size of the device. Attached Figure Description

[0015] Figure 1 These are the steps of the adaptive acquisition and storage delay control method for water depth detection lidar echo signals of the present invention;

[0016] Figure 2 This is a framework diagram of the adaptive acquisition and storage delay control system for water depth detection lidar echo signals of the present invention.

[0017] Figure 3 It is an adaptive delay module for water depth detection lidar.

[0018] Figure 4 This is a timing diagram of adaptive delay adjustment for a water depth detection lidar.

[0019] Figure 5 This is a waveform diagram of echo data collected and stored by a water depth detection lidar. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, preferred embodiments are described below, and the specific implementation of the present invention is further described in detail with reference to the accompanying drawings.

[0021] Example:

[0022] Combination Figure 1 and Figure 2 The following describes the steps of the adaptive acquisition and storage delay control method for water depth detection lidar echo signals of the present invention:

[0023] First, the ground-based system sends a lidar initialization command to the lidar main control module via a 4G module. The POS system and the high-speed acquisition and storage system complete initialization. Ground-based users communicate with the lidar 4G module via a mobile phone or computer. The 4G module in the lidar then connects to the main control module via an RS232 interface.

[0024] Second, once the lidar reaches the designated location, the user activates it via a 4G module. The lidar POS system sends altitude data to the lidar high-speed acquisition and storage module. This module preprocesses the data and performs a coarse delay adjustment. After adjustment, the module sends the completed delay and the coarse delay time back to the main control module. The main control module then controls the laser module to emit light. The nanosecond-level laser light is emitted by the laser module, received by the optical system, and finally converted into an analog signal by the PMT detection module. This analog signal is then converted into a digital signal by the acquisition and storage module and cached in the FPGA.

[0025] Third, the adaptive latency module detects the location of the maximum data value and makes corresponding latency adjustments to complete fine-tuning, and finally stores the data in the solid-state drive.

[0026] Fourth, the high-speed acquisition and storage system judges the height data sent by the POS system module. When this height data exceeds a certain range, it will automatically perform the third step to ensure the integrity of the water surface and bottom echoes.

[0027] Combination Figure 3 and Figure 4 This invention describes the adaptive delay module for a water depth detection lidar:

[0028] When the LiDAR is initialized, the POS system module will perform initialization operations, setting the height to 0, activating the high-speed data acquisition and storage system, and resetting the adaptive delay module, setting the delay time... Adjust to 0ns;

[0029] Once the lidar reaches the designated location, the user activates it via a 4G module. The lidar POS system module then sends the current altitude data to the high-speed data acquisition and storage system for preprocessing. The adaptive delay module will then roughly adjust the delay time based on this altitude data. ns. Based on the speed of laser propagation in air:

[0030]

[0031] in, , The vertical height at which the laser radar reaches the water surface.

[0032] The delay time is obtained at this time. ns, according to the formula, the roughly adjusted delay time is

[0033]

[0034] in This provides a fixed delay between the PMT detection module detecting the echo signal and the solid-state drive storing the data.

[0035] After the high-speed acquisition and storage system roughly adjusts the delay time, it sends a feedback signal to the main control. The main control then turns on the laser. The high-speed data acquisition and storage system buffers 10 sets of data into the FPGA cache module. The echo data maximum value detection module analyzes these data to detect if there is a valid maximum value. If a valid maximum value is found, this value is derived from the noise of the high-speed data acquisition and storage system. This module calculates the average value of the maximum value positions of these 10 sets of data. The calculated average value is... The sampling signal pulse width in a high-speed acquisition and storage system like Figure 4 As shown, the final goal is to shift the maximum value of the waveform data to... At this point, it is more important to compare. and Size,

[0036] if So, this makes the delay time ;

[0037] if So, this makes the delay time ;

[0038] if So, this makes the delay time

[0039] At this point, the waveform data will be adjusted to the middle position in the acquisition and storage data packet, which can effectively cope with the impact of certain height changes and ensure the integrity of the waveform data.

[0040] The high-speed data acquisition and storage system determines whether a change in height has reached a critical value using the following method:

[0041] if or At that time, among them With sampling pulse width This is related to the maximum water depth that the lidar can measure. As the lidar's altitude changes, the echoes from the water surface and bottom may exceed the pulse width range of the high-speed acquisition and storage of the sampling signal. In this case, it will be necessary to readjust the delay time and perform the fine-tuning operation again based on the position of the peak value at this time.

[0042] Combination Figure 5 This is a waveform diagram of the echo data collected and stored after using the adaptive delay module of the water depth sounding lidar.

[0043] Before using the adaptive delay module for depth-sensing lidar, there was a possibility of data loss due to surface and bottom echoes approaching the critical pulse width for acquisition, and the system could not handle the effects of changes in lidar altitude. With adaptive delay adjustment, this can be addressed. The change in altitude over time, this altitude is m,

[0044]

[0045]

[0046] It was clearly observed that by adopting the adaptive module, at a certain altitude, the integrity of the echo data could be guaranteed while reducing the application of FPGA resources. When the altitude change exceeds a certain range, it can adaptively adjust in a timely manner, placing the echo data back in the middle position of the acquisition and storage data packets, effectively ensuring the timeliness and integrity of data acquisition. At the same time, it also reduces the storage of invalid data by the LiDAR, saving on the size and number of solid-state drives, thereby reducing the size of the device.

[0047] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also fall within the scope of this invention, and the patent protection scope of this invention should be defined by the claims.

[0048] All technical contents not described in detail in this invention are publicly known technologies.

Claims

1. A method for adaptive acquisition and storage delay control of water depth sounding lidar echo signals, characterized in that... The following steps are required: First, the ground-based system sends a lidar initialization command to the lidar main control module via a 4G module; the POS system completes initialization and sets the altitude to 0; the high-speed data acquisition and storage system is activated, and the adaptive delay module performs a reset operation, adjusting the delay time. Adjust to 0ns; Second, once the lidar reaches the designated location, the user activates the lidar via a 4G module. The lidar POS system sends altitude data to the lidar's high-speed acquisition and storage module. The high-speed acquisition and storage module preprocesses this altitude data and performs a coarse delay adjustment. The adaptive delay module then roughly adjusts the delay time based on this altitude data. ns; based on the speed of laser propagation in air: ； in, , The vertical height at which the laser radar reaches the water surface; The delay time is obtained at this time. ns, according to the formula, the roughly adjusted delay time is ； in The fixed delay between the PMT detection module detecting the echo signal and the solid-state drive storing the data; After the adjustment is completed, the delay adjustment completion and rough adjustment delay time are fed back to the main control module. The main control module will control the laser module to emit light. The nanosecond laser is emitted by the laser module, received by the optical system, and finally the PMT detection module is responsible for converting the optical signal into an analog signal. Then, this analog signal is converted into a digital signal by the acquisition and storage module and the data is cached in the FPGA. Third, the adaptive delay module detects the location of the maximum data value to determine if a valid maximum value exists. If a valid maximum value is found, this value is determined based on the noise of the high-speed data acquisition and storage system. This module then calculates the average value of the maximum value locations of these 10 sets of data. The calculated average value is... The sampling signal pulse width in the high-speed acquisition and storage system is So, the final goal is to shift the maximum value of the waveform data to... At this point, it is more important to compare. and Size, if So, this makes the delay time ; if So, this makes the delay time ; if So, this makes the delay time ; At this point, fine-tuning will be completed, and finally, the data will be stored on a solid-state drive. Fourth, the high-speed acquisition and storage system determines whether the height change has reached a critical value based on the height data sent by the POS system module. The determination method is as follows: if or At that time, among them With sampling pulse width It is related to the maximum water depth measured by the lidar. As the lidar height changes, the echoes from the water surface and bottom may exceed the pulse width range of the sampling signal collected and stored at high speed. At this time, it is necessary to readjust the delay time and perform the fine adjustment operation based on the position of the peak value.

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