Laser radar signal processing and control device based on embedded system

Abstract

The invention discloses a laser radar signal processing and control device based on an embedded system, which adopts the embedded system, is realized based on a programmable heterogeneous multi-core platform, and comprises a signal detection and acquisition unit, a gain control unit, a component monitoring and isolation unit and a data communication and storage unit. Wherein the signal detection and acquisition unit receives signals of the PMT detection module and sends the signals to the platform for processing; the gain control unit performs gain adjustment on the PMT detection module; the assembly monitoring and isolating unit controls laser emission and carries out monitoring; and the data communication and storage unit is used for locally storing and remotely transmitting platform processing data. The device can realize full-process operation of the laser radar without depending on an industrial personal computer, is suitable for an outdoor unattended atmosphere detection scene, has the advantages of small size, low power consumption, high integration degree, stable operation and the like, and provides an innovative solution for miniaturization and efficient operation of a laser radar system.

Description

Technical Field

[0001] The present invention relates to the technical field of laser radar signal processing and control, and in particular to a laser radar signal processing and control device based on an embedded system. Background Art

[0002] As an active remote sensing technology with high temporal and spatial resolution, LiDAR has been widely used in the field of atmospheric detection, including pollution gas monitoring, atmospheric boundary layer observation, cloud and precipitation monitoring, and extreme weather and climate change research. The LiDAR embedded system is mainly composed of a laser transmitting unit, an optical receiving unit, a signal detection and processing unit, and a control unit.

[0003] According to the laser radar equation, the echo signal strength is inversely proportional to the square of the detection height, so the echo signal at a long distance is very weak. The signal output by the PMT detection module is usually a unipolar current signal, while the high-speed and high-precision ADC (analog-to-digital converter) usually uses a differential signal input with a smaller dynamic range. In order to effectively match the output signal of the PMT detection module with the dynamic range of the ADC, it is necessary to design a low-noise signal processing circuit. Through bias and amplification processing, the signal distortion is minimized to the greatest extent, and the signal-to-noise ratio of the echo signal is improved, thereby increasing the detection distance of the laser radar.

[0004] The echo signal strength is also affected by weather conditions. For example, when the weather is clear, the detection distance is far and the echo signal peak is small. At this time, the detector gain can be appropriately increased to match the input dynamic range of the AD acquisition circuit. In haze weather, aerosol particles enhance the backscattering effect, resulting in a higher peak of the echo signal. At this time, the detector gain needs to be appropriately reduced, otherwise it may cause clipping distortion in the AD acquisition circuit. In addition, the echo signal strength is different during the day and at night. Therefore, a fixed gain detector cannot meet the detection needs of all weather conditions.

[0005] The control unit of the laser radar is usually implemented by an industrial computer. The industrial computer installs and operates the embedded system and the corresponding software, controls the laser, acquisition card and other components through the communication protocol, and ensures that each unit works in a timely manner. However, as a general-purpose computing device, although the industrial computer has powerful computing power and flexible scalability, its design is not optimized for laser radar applications. In outdoor unmanned laser radar embedded systems that require high stability, low power consumption, and light weight, the shortcomings of the industrial computer are particularly prominent: (1) Operation stability issues: The industrial computer runs a general-purpose operating embedded system. In a long-term unmanned environment, data collection may be interrupted due to problems such as embedded system crashes, freezes, or file embedded system damage. (2) Environmental adaptability issues: The industrial computer has poor adaptability to harsh environments such as extreme temperature, humidity, and vibration. Although its adaptability can be improved through optimized design, this will increase the cost and maintenance difficulty of the equipment.

[0006] For example, the invention application with application number 202310241223.6 discloses a lightweight atmospheric monitoring laser radar system. The laser radar system in this application adopts a coaxial co-body optical system, which achieves the purpose of compact system structure, small size and light weight; it can conveniently and effectively realize atmospheric monitoring, and provides ideas for the development of portable laser radar systems. However, it can be understood from its solution that it uses a mini industrial computer 5 for power supply, and still relies on the use of an external industrial computer.

[0007] Therefore, in order to solve these problems, the LiDAR field urgently needs an efficient embedded solution that does not rely on industrial computers. It can realize the control of LiDAR, echo signal processing, data storage and transmission, and meet the requirements of portability, low power consumption, high stability and adaptability to complex environments, especially suitable for unmanned outdoor atmospheric detection scenarios. Summary of the invention

[0008] In view of the above-mentioned problems, the purpose of the present invention is to provide a laser radar signal processing and control device based on an embedded system, which facilitates low-power and lightweight outdoor deployment of the laser radar and improves the stability and environmental adaptability of the laser radar operation.

[0009] The object of the present invention can be achieved by the following technical solution: a laser radar signal processing and control device based on an embedded system, the device is based on a programmable heterogeneous multi-core platform and is implemented using an embedded system, comprising:

[0010] The signal detection and acquisition unit receives the electrical signal converted by the PMT detection module, converts it through the signal conditioning circuit and AD converter, and then sends it to the platform for processing;

[0011] The gain control unit interacts with the platform and outputs an adjustable voltage signal through a digitally controlled potentiometer and a buffer and filter circuit to adjust the gain of the PMT detection module;

[0012] The component monitoring and isolation unit interacts with the platform, controls the laser, pan / tilt and optical adjustment frame through the RS232 serial communication protocol, controls the laser emission and monitors it;

[0013] The data communication and storage unit interacts with the platform to locally store and remotely transmit the data processed by the platform.

[0014] As a further solution of the present invention, the gain control unit uses the built-in ADC module of the platform to monitor the control voltage of the PMT detection module.

[0015] As a further solution of the present invention, the component monitoring and isolation unit collects the external trigger signal output by the laser and synchronized with the laser, and sends it to the platform after being processed by the digital isolator.

[0016] As a further solution of the present invention, the data communication and storage unit stores data in a fixed format and has its own time stamp.

[0017] As a further solution of the present invention, the signal conditioning circuit includes: a current / voltage conversion circuit, a signal isolation circuit, a bias voltage generation circuit, an in-phase adding amplifier circuit, a single-ended to differential circuit and an anti-aliasing filter circuit.

[0018] As a further solution of the present invention, the signal conditioning circuit structure includes:

[0019] Ports 1 and 2 of RF1 are grounded, ports 3 and 4 of RF1 are grounded and connected to one end of R7, and port 5 of RF1 is connected to the other end of R7 and port 3 of U1;

[0020] Port 1 and 2 of U1 are interconnected, port 7 of U1 is connected to +5V and one end of C1, the other end of C1 is grounded, port 4 of U1 is connected to -5V and one end of C5, the other end of C5 is grounded, and port 6 of U1 is connected to one end of R5;

[0021] The other end of R5 is connected to port 3 of U2 and one end of R8. The other end of R8 is connected to ports 1 and 4 of U5. Port 2 of U2 is connected to one end of R3 and one end of R1. The other end of R3 is grounded. The other end of R1 is connected to port 1 of U2. Port 7 of U2 is connected to +5V and one end of C2. The other end of C2 is grounded. Port 4 of U2 is connected to -5V and one end of C6. The other end of C6 is grounded. Port 6 of U2 is connected to one end of R6.

[0022] The other end of R6 is connected to port 2 of U3 and one end of R2. The other end of R2 is connected to port 1 of U3. Port 9 of U3 is connected to the VOCM signal. Port 3 of U3 is connected to one end of R9 and one end of R10. The other end of R9 is grounded. The other end of R10 is connected to port 4 of U3. Port 16 of U3 is connected to +5V and one end of C3. The other end of C3 is grounded. Port 5 of U3 is connected to -5V and one end of C7. The other end of C7 is grounded. Port 11 of U3 is connected to one end of R4. The other end of R4 is connected to one end of C4. Port 10 of U3 is connected to one end of R11. The other end of R11 is connected to the other end of C4.

[0023] Port 5 of U5 is connected to +5V and one end of C8, and the other end of C8 is grounded. Port 2 of U5 is grounded, one end of R13 and port 4 of U4. Port 3 of U5 is connected to the other end of R13 and one end of R12. The other end of R12 is connected to one end of C12, one end of C11 and port 6 of U4. The other end of C12 and the other end of C11 are grounded. Port 2 of U4 is connected to one end of C9, one end of C10 and +3.3V, and the other end of C9 and the other end of C10 are grounded.

[0024] As a further solution of the present invention, the buffer and filter circuit includes a reference voltage generating circuit, a PMT gain adjustment circuit and a buffer and filter circuit.

[0025] As a further solution of the present invention, the buffer and filter circuit structure includes:

[0026] Port 4 of U7 is connected to one end of R16, the other end of R16 is connected to +5V and one end of C16, the other end of C16 is grounded, port 2 of U7 is grounded and one end of R15, port 1 of U7 is connected to one end of C13, the other end of R15 and one end of R14, port 5 of U7 is connected to the other end of C13, the other end of R14 and port 3 of U6;

[0027] Port 2 of U6 is connected to ground, port 5 of U6 is connected to one end of R17, port 6 of U6 is connected to one end of C15 and one end of C14, port 7 of U6 is connected to one end of C19, the other end of R17, the other end of C15, the other end of C14 and the other end of C19 are connected to port 9 of U6, port 8 of U6 is connected to +5V, port 10 of U6 is connected to DIN signal, port 11 of U6 is connected to SCLK signal, port 12 of U6 is connected to SYNC signal, port 13 of U6 is connected to SDO signal, port 4 of U6 is connected to port 3 of U8;

[0028] Port 5 of U8 is connected to one end of C17, the other end of C17 is grounded, port 5 of U8 is connected to port 1 and one end of R18, the other end of R18 is connected to one end of C18, and port 2 of U8 is grounded and the other end of C18.

[0029] As a further solution of the present invention, the system control software is developed using C language and interacts with each unit through an AT instruction set.

[0030] As a further solution of the present invention, the system control software control platform interaction process includes: module initialization, equipment self-check, waiting for server instructions, echo signal acquisition and data storage.

[0031] Beneficial effects of the present invention:

[0032] 1. The laser radar signal processing and control device of the present invention relies on a programmable heterogeneous multi-core platform to form a laser radar embedded control system. The system controls components such as lasers and acquisition cards through communication protocols to ensure that each unit works together in a timely manner. The full process operation of the laser radar can be achieved without relying on an industrial control computer, including the timing control of each unit, detection and acquisition of echo signals, data storage and remote transmission. It is particularly suitable for outdoor unmanned atmospheric detection scenarios. The entire device has the advantages of small size, low power consumption, high integration and stable operation, providing an innovative solution for the miniaturization and efficient operation of the laser radar system.

[0033] 2. The laser radar signal processing and control device of the present invention combines signal processing and gain control functions, wherein the signal processing unit ensures that the signal output by the detector accurately matches the dynamic range of the AD acquisition circuit, thereby significantly improving the detection accuracy and detection distance. The gain control unit dynamically adjusts the gain of the detector according to real-time weather changes, further optimizing the adaptability of the signal processing circuit and ensuring that it can work stably under different weather conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the laser radar signal processing and control device of the present invention;

[0035] Figure 2 It is a structural schematic diagram of the signal conditioning circuit of the present invention;

[0036] Figure 3 It is a structural schematic diagram of the buffer and filter circuit of the present invention;

[0037] Figure 4 This is an interactive flow chart of the embedded system control software control platform of the present invention;

[0038] Figure 5 It is a schematic diagram of the intermittent working time interval of the present invention. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0040] The control embedded system of existing LiDAR usually relies on industrial computers, which are not suitable for low-power, lightweight outdoor unattended LiDAR deployment.

[0041] In response to the above problems, such as Figure 1 As shown, the present invention discloses a laser radar signal processing and control device based on an embedded system. The device adopts an embedded system and is implemented based on a programmable heterogeneous multi-core platform, including: a signal detection and acquisition unit, a gain control unit, a component monitoring and isolation unit, and a data communication and storage unit.

[0042] The programmable heterogeneous multi-core platform can use ZYNQ7020 as the core. ZYNQ7020 includes a processing subsystem (PS) and programmable logic (PL). PS is an embedded system including ARM and peripherals, and PL is a field-programmable gate array (FPGA), which consists of resources such as look-up tables (LUTs), triggers, memories, and DSP modules.

[0043] As the control center, PS is mainly responsible for the management of peripheral devices and task scheduling, including coordinating the operation of various LiDAR components according to the specified timing to achieve precise control. At the same time, PS also undertakes the local storage and remote communication functions of data.

[0044] As a co-processing module of PS, PL is mainly responsible for tasks such as high-speed ADC data acquisition, accumulation and caching, and transmits the processed data to PS through the high-speed AXI (Advanced eXtensible Interface) bus.

[0045] The laser radar embedded control system based on the ZYNQ7020 platform can be customized according to the specific needs of the laser radar, abandoning the redundant modules and functions of traditional industrial computers, thereby greatly improving the reliability and stability of the embedded system. The low-power design and industrial-grade operating temperature range make the embedded system particularly suitable for unmanned outdoor working environments.

[0046] Among them, the detection of the echo signal can adopt the H10721-210 photomultiplier tube (PMT, Photomultiplier Tube) detection module. H10721-210 is a high-performance detector designed for weak light signal detection, and its core component is a high-gain vacuum PMT.

[0047] The PMT detection module uses H10721-210, which has excellent performance of high sensitivity, wide dynamic range and low noise, and is very suitable for laser radar application scenarios with weak echo signals.

[0048] The PMT detection module adopts H10721-210 with compact structure, integrated high-voltage power supply and resistor voltage divider network, and supports 5V single power supply. The high voltage required for the operation of the PMT detection module is set through the gain control port (Vcont), and the input control voltage range is 0.5~1.1V. When the echo signal is incident on the detector target, the module outputs a current signal proportional to the light intensity. Its spectral response range covers the commonly used wavelengths of laser radar such as 532nm and 355nm, and is particularly suitable for the detection of aerosols, clouds and polluted gases in atmospheric laser radar systems.

[0049] The signal detection and acquisition unit is mainly used to receive the electrical signal converted by the PMT detection module, and after conversion by the signal conditioning circuit and AD converter, it is sent to the platform for processing.

[0050] like Figure 3 As shown, the signal conditioning circuit is mainly composed of a current / voltage conversion circuit, a signal isolation circuit, a bias voltage generation circuit, a common-phase addition amplifier circuit, a single-ended to differential circuit and an anti-aliasing filter circuit. The structure of the signal conditioning circuit is:

[0051] Ports 1 and 2 of RF1 are grounded, ports 3 and 4 of RF1 are grounded and connected to one end of R7, and port 5 of RF1 is connected to the other end of R7 and port 3 of U1;

[0052] Port 1 and 2 of U1 are interconnected, port 7 of U1 is connected to +5V and one end of C1, the other end of C1 is grounded, port 4 of U1 is connected to -5V and one end of C5, the other end of C5 is grounded, and port 6 of U1 is connected to one end of R5;

[0053] The other end of R5 is connected to port 3 of U2 and one end of R8. The other end of R8 is connected to ports 1 and 4 of U5. Port 2 of U2 is connected to one end of R3 and one end of R1. The other end of R3 is grounded. The other end of R1 is connected to port 1 of U2. Port 7 of U2 is connected to +5V and one end of C2. The other end of C2 is grounded. Port 4 of U2 is connected to -5V and one end of C6. The other end of C6 is grounded. Port 6 of U2 is connected to one end of R6.

[0054] The other end of R6 is connected to port 2 of U3 and one end of R2. The other end of R2 is connected to port 1 of U3. Port 9 of U3 is connected to the VOCM signal. Port 3 of U3 is connected to one end of R9 and one end of R10. The other end of R9 is grounded. The other end of R10 is connected to port 4 of U3. Port 16 of U3 is connected to +5V and one end of C3. The other end of C3 is grounded. Port 5 of U3 is connected to -5V and one end of C7. The other end of C7 is grounded. Port 11 of U3 is connected to one end of R4. The other end of R4 is connected to one end of C4. Port 10 of U3 is connected to one end of R11. The other end of R11 is connected to the other end of C4.

[0055] Port 5 of U5 is connected to +5V and one end of C8, and the other end of C8 is grounded. Port 2 of U5 is grounded, one end of R13 and port 4 of U4. Port 3 of U5 is connected to the other end of R13 and one end of R12. The other end of R12 is connected to one end of C12, one end of C11 and port 6 of U4. The other end of C12 and the other end of C11 are grounded. Port 2 of U4 is connected to one end of C9, one end of C10 and +3.3V, and the other end of C9 and the other end of C10 are grounded.

[0056] With the above circuit structure and the current / voltage conversion circuit, the current signal output by the PMT detection module is input to RF1 (SMA port) through a coaxial cable with a 50Ω characteristic impedance. R7 uses a 50Ω resistor to convert the current into a voltage signal for easy subsequent processing. At the same time, the 50Ω matching resistor also avoids the distortion caused by signal transmission, and the converted V1 is obtained as a negative voltage signal.

[0057] The signal isolation circuit is mainly composed of a voltage follower constructed by the operational amplifier U1. The voltage follower has the advantages of high input impedance and low output impedance. It effectively isolates the front-end impedance matching circuit from the back-end single-ended to differential circuit, avoids mutual influence between the front-end and back-end circuits, and improves the acquisition accuracy of the analog signal.

[0058] Since the echo signal strength is inversely proportional to the square of the distance, the far-field echo signal of the lidar is extremely weak and can be easily submerged by noise. Therefore, a low-noise operational amplifier U1 is used with sufficient bandwidth and slew rate to accurately restore the echo signal.

[0059] U1 can use the high-speed, low-noise operational amplifier ADA4817-1. This chip has a high slew rate of 870V / μs and a unity gain bandwidth product of 1050MHz. The input voltage noise is as low as 4nV / √Hz, the current noise is 2.5fA / √Hz, and the bias current is 2pA, which meets the bandwidth and signal integrity requirements of the lidar echo signal.

[0060] Furthermore, in order to maximize the dynamic range of the AD conversion chip and improve the signal-to-noise ratio of data acquisition, a common-phase addition amplifier circuit is used to pull up the negative voltage signal output by the signal isolation circuit and amplify it by several times (the multiple n is related to the laser energy, telescope aperture, etc., and is adjusted according to the test value), where R1 is the feedback resistor, R1=n×R3, and R5 and R8 are input resistors.

[0061] The bias voltage generating circuit outputs the bias voltage V4 as the other input terminal of the in-phase adding amplifier circuit. U4 can use the reference voltage chip REF192 to output the required bias voltage through resistors R12 and R13. U5 is a voltage buffer used to eliminate the influence of the load effect generated by the back-end circuit on the bias voltage accuracy.

[0062] After being processed by the in-phase adding amplifier circuit, V5 is an AC voltage signal with an amplitude close to ±1V, which is converted into differential voltage signals V6 and V7 by the single-ended to differential circuit. VOCM is the common-mode voltage input port, which can be provided by the 0.9V output of LTC2191.

[0063] U3 can use the ADA4938-1 chip as an ultra-low distortion ADC driver to achieve single-ended to differential signal conversion. The chip input voltage noise is only 2.6nV / √Hz, and the -3dB bandwidth is 1GHz, which meets the acquisition requirements of the laser radar echo signal. R6 and R9 are the input resistors of the amplifier, and R2 and R10 are feedback resistors, and their resistance values ​​are all 200Ω. Since the resistor will affect the output voltage accuracy, a metal film resistor with a tolerance of 0.1% is selected.

[0064] The low-pass filter circuit uses R4, R11 and capacitor C4 to form a low-pass RC anti-aliasing filter to eliminate the spectrum aliasing caused by input noise. The sampling rate of the ADC chip used is 40MHz. According to the Nyquist sampling theorem, the maximum frequency of the sampled signal should not exceed 20MHz, otherwise the signal may be aliased, causing distortion. Considering a certain margin, the filter cutoff frequency is set to 15MHz.

[0065] The obtained V8 and V9 are connected to the differential analog input terminals of the high-speed AD converter.

[0066] Spatial resolution is one of the key performance indicators of LiDAR. Under the premise of determining the laser parameters, spatial resolution is mainly determined by the sampling rate of the AD converter. Since the far-field echo signal of LiDAR is extremely weak, high requirements are placed on the resolution of the AD converter. Taking all factors into consideration, the AD converter can use the high-performance analog-to-digital converter LTC2191 with a sampling rate of 40MHz and a resolution of 16 bits.

[0067] The LTC2191 supports ±1V differential voltage input, which can effectively suppress common-mode noise interference and transmit the collected data to the PL end of the platform for processing through the LVDS differential interface. The high linearity and low noise characteristics of the LTC2191 ensure high-fidelity sampling of the lidar echo signal, providing reliable protection for subsequent data inversion.

[0068] The gain control unit interacts with the platform and is mainly used to output an adjustable voltage signal through a digitally controlled potentiometer and a buffer and filter circuit to adjust the gain of the PMT detection module.

[0069] like Figure 4 As shown, the buffer and filter circuit includes a reference voltage generating circuit, a PMT gain adjustment circuit, a buffer and filter circuit, etc.

[0070] The buffer and filter circuit structure is implemented as:

[0071] Port 4 of U7 is connected to one end of R16, the other end of R16 is connected to +5V and one end of C16, the other end of C16 is grounded, port 2 of U7 is grounded and one end of R15, port 1 of U7 is connected to one end of C13, the other end of R15 and one end of R14, port 5 of U7 is connected to the other end of C13, the other end of R14 and port 3 of U6;

[0072] Port 2 of U6 is connected to ground, port 5 of U6 is connected to one end of R17, port 6 of U6 is connected to one end of C15 and one end of C14, port 7 of U6 is connected to one end of C19, the other end of R17, the other end of C15, the other end of C14 and the other end of C19 are connected to port 9 of U6, port 8 of U6 is connected to +5V, port 10 of U6 is connected to DIN signal, port 11 of U6 is connected to SCLK signal, port 12 of U6 is connected to SYNC signal, port 13 of U6 is connected to SDO signal, port 4 of U6 is connected to port 3 of U8;

[0073] Port 5 of U8 is connected to one end of C17, the other end of C17 is grounded, port 5 of U8 is connected to port 1 and one end of R18, the other end of R18 is connected to one end of C18, and port 2 of U8 is grounded and the other end of C18.

[0074] Because the gain control voltage range of the H10721-210 PMT detection module is 0.5V to 1.1V. Exceeding this range will cause the detector to not work properly and may even shorten its service life.

[0075] With the above circuit structure, the reference voltage generation circuit is composed of a low-noise reference voltage chip U7 (such as LT6650) and discrete components. The reference voltage generated by U7 is 400mV. The feedback circuit composed of resistors R14 and R15 stabilizes the output voltage V10 at 1.1V. R14 uses a multi-turn potentiometer and R15 uses a 1% tolerance resistor. C16 and C13 are filter capacitors, and R16 is a current limiting resistor.

[0076] The PMT gain adjustment circuit is based on a digital potentiometer U6 (e.g. AD5291), which has a resistance tolerance as low as 1%, ensuring a high gain adjustment accuracy. With non-volatile memory, it can still maintain the output resistance value after power failure, avoiding signal distortion caused by device restart. A and B are the potentiometer terminals, with a resistance value of 20kΩ, and the W terminal is the adjustment terminal. Adjust the multi-turn potentiometer R17 to fix the V12 voltage at 0.5V.

[0077] The ZYNQ7020 platform processor is connected to the SPI communication interface (SDO, SYNC, SCLK and DIN) of U6 to adjust the position of the W terminal to slide between A and B. The voltage V11 is output through the W terminal of the potentiometer, processed by the buffer and filter circuit, and the output is used to adjust the PMT gain voltage V13. The buffer and filter circuit consists of an operational amplifier U8 (such as AD8626) and an RC low-pass filter circuit (composed of a resistor R18 and a capacitor C18).

[0078] Furthermore, the gain control unit uses the built-in ADC module (1 MHz sampling rate, 12-bit resolution) of the platform to monitor the control voltage of the PMT detection module, and the monitoring result is used as one of the input parameters of data inversion.

[0079] The component monitoring and isolation unit interacts with the platform and is mainly used to control the laser, pan / tilt and optical adjustment frame through the RS232 communication interface, control the laser emission and monitor it.

[0080] Monitor the status of lasers, pan / tilts, and optical mounts through the component monitoring and isolation unit.

[0081] Pulsed lasers and other devices inside the LiDAR require large current drives. If they are not electrically isolated, electromagnetic interference may occur, causing adverse effects on the detector or data acquisition circuit. To this end, ZYNQ7020 uses isolated RS232 and RS485 drivers to communicate with the laser, pan / tilt, and optical adjustment frame.

[0082] The RS232 driver can use the ADM3251E chip, which is an RS232 transceiver with electrical isolation function. It is based on iCoupler technology and provides electrical isolation performance of up to 2.5kV.

[0083] The RS485 driver can use the ADM2561E chip, which is a highly integrated isolated RS485 transceiver that supports an isolation voltage of up to 5kVrms.

[0084] At the same time, when the laser is working, the electrical synchronization port outputs a pulse signal synchronized with the emitted laser, which is collected by the component monitoring and isolation unit. After pulse isolation and voltage conversion are achieved through a digital isolator (such as ADuM210N), the signal is input to the PL end of ZYNQ7020 as a synchronization trigger signal for data acquisition, ensuring the stable operation and accurate data acquisition of the lidar embedded system.

[0085] The data communication and storage unit interacts with the platform and is mainly used for local storage and remote transmission of platform processed data. The data communication and storage unit consists of a 4G wireless communication module, a USB PHY (physical layer) chip module, and a large-capacity USB flash drive.

[0086] When a lidar with an embedded system is deployed outdoors for continuous observation, manual on-site operation and maintenance has high costs and low efficiency. A 4G wireless communication module can be used to establish a communication connection with a remote computer server, which can significantly improve management efficiency.

[0087] The 4G wireless communication module can use the EC800M-CN wireless communication module, which supports LTE Cat1 network with a maximum downlink rate of 10Mbps and an uplink rate of 5Mbps. With the EC800M-CN module on the laser radar, the remote computer can monitor the laser radar status in real time, adjust working parameters or complete data reading, etc., without the need for on-site operation by personnel.

[0088] In terms of hardware, the ZYNQ7020 platform is connected to the EC800M-CN through the UART serial port; in terms of software, the ZYNQ7020 platform interacts with the EC800M-CN through the AT instruction set to establish a reliable communication connection based on the TCP protocol to ensure the integrity and reliability of data during transmission. Compared with the UDP protocol, the TCP protocol is more suitable for application scenarios that require high data integrity.

[0089] Furthermore, the data collected by the embedded system can be stored on a local non-volatile storage medium, thereby avoiding frequent interactions with the server, reducing network resource usage, and reducing the risk of data loss due to network failures.

[0090] The ZYNQ7020 platform integrates a USB controller, which is connected to the USB PHY chip through the ULPI interface to realize the USBHOST function. The USB PHY chip can use USB3300, which complies with the USB 2.0 specification and supports a data transfer rate of up to 480Mbps. By transplanting the USB protocol stack and file embedded system on the ARM processor of ZYNQ7020, the embedded system stores the collected and processed data in a storage device such as a USB flash drive or a mobile hard disk in a specified format. The remote computer server can obtain data by reading these storage devices to achieve flexible data transmission and management, further improving the reliability and practicality of the embedded system.

[0091] Furthermore, the data collected by the laser radar has a time attribute, and the present invention adds a timestamp function when storing or transmitting locally. The ZYNQ7020 platform reads the time and date information of the built-in real-time clock (RTC) module through the internal bus, including year, month, day, hour, minute, second and week.

[0092] Furthermore, the embedded system control software is developed in C language, and the compiled target code runs on the PS side of ZYNQ7020, interacting with each unit through the AT instruction set.

[0093] like Figure 4 As shown, the interactive process of the system control software control platform includes: module initialization, equipment self-test, waiting for server instructions, echo signal acquisition and data storage, etc., and is executed in a loop.

[0094] The module initialization includes the initialization of the clock, RTC, serial port, interrupt and watchdog timer (WDT) modules. In addition, it also includes the configuration of the laser, optical adjustment frame, storage device, 4G communication module and PMT detection module gain related parameters.

[0095] The embedded system performs a self-check every 5 seconds, and detects the working status of each component by sending query commands to each laser and other components. If the device feedback information is incorrect or does not respond in time, the embedded system will determine that the device communication is abnormal, record the corresponding error code, and report it to the user in real time via a short message through the 4G wireless communication module.

[0096] Next, the embedded system checks whether it has received a TCP command from the server. If it has received a command, it will enter the corresponding program, such as data reading, mode setting, gain setting, and pan / tilt control. If the mode setting parameter is dimming mode, the PS controls the laser to emit light and sends instructions to the PL at the same time. After PL collects and accumulates 20 times (the laser frequency is 20Hz, and the collection result is output once per second in dimming mode), the data is transmitted back to the PS. The data is sent to the remote server through the 4G wireless communication module, and remote dimming is performed through the server-side software.

[0097] In the acquisition mode, in order to extend the life of the laser and prevent its performance from deteriorating due to continuous operation, the laser and data acquisition unit work intermittently (judged by reading the current time of the RTC module). Figure 5 As shown in the figure, when the number of minutes is 5, the PS sends the "system enable" and "light gate open" commands to the laser to start laser emission. At the same time, the PS sends a command to the PL through the AXI_Lite bus to start AD sampling. After the PL completes 4000 data collection and accumulation (continuous operation for 200s), it transmits the accumulated data back to the PS, and the PS stores the data in the USB flash drive in the specified format to complete the entire data collection and storage process.

[0098] The laser radar signal processing and control device of the present invention realizes an embedded control system based on a programmable heterogeneous multi-core platform ZYNQ-7020, and is composed of a signal detection and acquisition unit, a gain control unit, a component control unit, and a data communication and storage unit.

[0099] The laser radar echo signal is converted into an electrical signal by the PMT module, converted by the signal conditioning circuit and processed by the high-speed AD converter and sent to the platform. At the same time, the gain control unit is used to adjust the gain of the PMT module. The laser, pan / tilt and optical adjustment frame are controlled by the equipment control unit. The data communication and storage unit are used to complete the remote transmission and local storage of data. The device has a high degree of integration and can realize the full process operation of the laser radar without relying on the industrial control computer. It is particularly suitable for outdoor unattended atmospheric detection scenes. It has the advantages of small size, low power consumption, high integration and stable operation, and provides an innovative solution for the miniaturization and efficient operation of the laser radar system.

[0100] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0101] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

Claims

1. A laser radar signal processing and control device based on an embedded system, characterized in that: The device is based on a programmable heterogeneous multi-core platform and adopts an embedded system, including: The signal detection and acquisition unit receives the electrical signal converted by the photomultiplier tube PMT detection module, converts it through the signal conditioning circuit and AD converter, and then sends it to the platform for processing; The gain control unit interacts with the platform and outputs an adjustable voltage signal through a digitally controlled potentiometer and a buffer and filter circuit to adjust the gain of the PMT detection module; The component monitoring and isolation unit interacts with the platform, controls the laser, pan / tilt and optical adjustment frame through the RS232 serial communication protocol, controls the laser emission and monitors it; The data communication and storage unit interacts with the platform to locally store and remotely transmit the data processed by the platform.

2. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The gain control unit uses the built-in ADC module of the platform to monitor the control voltage of the PMT detection module.

3. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The component monitoring and isolation unit collects the external trigger signal output by the laser and synchronized with the laser, and sends it to the platform after being processed by the digital isolator.

4. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The data communication and storage unit stores data in a fixed format and has a time stamp.

5. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The signal conditioning circuit comprises: a current / voltage conversion circuit, a signal isolation circuit, a bias voltage generation circuit, an in-phase addition amplifier circuit, a single-ended to differential circuit and an anti-aliasing filter circuit.

6. The laser radar signal processing and control device based on an embedded system according to claim 5, characterized in that: The signal conditioning circuit structure comprises: Ports 1 and 2 of RF1 are grounded, ports 3 and 4 of RF1 are grounded and connected to one end of R7, and port 5 of RF1 is connected to the other end of R7 and port 3 of U1; Port 1 and 2 of U1 are interconnected, port 7 of U1 is connected to +5V and one end of C1, the other end of C1 is grounded, port 4 of U1 is connected to -5V and one end of C5, the other end of C5 is grounded, and port 6 of U1 is connected to one end of R5; The other end of R5 is connected to port 3 of U2 and one end of R8. The other end of R8 is connected to ports 1 and 4 of U5. Port 2 of U2 is connected to one end of R3 and one end of R1. The other end of R3 is grounded. The other end of R1 is connected to port 1 of U2. Port 7 of U2 is connected to +5V and one end of C2. The other end of C2 is grounded. Port 4 of U2 is connected to -5V and one end of C6. The other end of C6 is grounded. Port 6 of U2 is connected to one end of R6. The other end of R6 is connected to port 2 of U3 and one end of R2. The other end of R2 is connected to port 1 of U3. Port 9 of U3 is connected to the VOCM signal. Port 3 of U3 is connected to one end of R9 and one end of R10. The other end of R9 is grounded. The other end of R10 is connected to port 4 of U3. Port 16 of U3 is connected to +5V and one end of C3. The other end of C3 is grounded. Port 5 of U3 is connected to -5V and one end of C7. The other end of C7 is grounded. Port 11 of U3 is connected to one end of R4. The other end of R4 is connected to one end of C4. Port 10 of U3 is connected to one end of R11. The other end of R11 is connected to the other end of C4. Port 5 of U5 is connected to +5V and one end of C8, and the other end of C8 is grounded. Port 2 of U5 is grounded, one end of R13 and port 4 of U4. Port 3 of U5 is connected to the other end of R13 and one end of R12. The other end of R12 is connected to one end of C12, one end of C11 and port 6 of U4. The other end of C12 and the other end of C11 are grounded. Port 2 of U4 is connected to one end of C9, one end of C10 and +3.3V, and the other end of C9 and the other end of C10 are grounded.

7. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The buffer and filter circuit comprises a reference voltage generating circuit, a PMT gain adjusting circuit and a buffer and filter circuit.

8. The laser radar signal processing and control device based on an embedded system according to claim 7, characterized in that: The buffer and filter circuit structure comprises: Port 4 of U7 is connected to one end of R16, the other end of R16 is connected to +5V and one end of C16, the other end of C16 is grounded, port 2 of U7 is grounded and one end of R15, port 1 of U7 is connected to one end of C13, the other end of R15 and one end of R14, port 5 of U7 is connected to the other end of C13, the other end of R14 and port 3 of U6; Port 2 of U6 is connected to ground, port 5 of U6 is connected to one end of R17, port 6 of U6 is connected to one end of C15 and one end of C14, port 7 of U6 is connected to one end of C19, the other end of R17, the other end of C15, the other end of C14 and the other end of C19 are connected to port 9 of U6, port 8 of U6 is connected to +5V, port 10 of U6 is connected to DIN signal, port 11 of U6 is connected to SCLK signal, port 12 of U6 is connected to SYNC signal, port 13 of U6 is connected to SDO signal, port 4 of U6 is connected to port 3 of U8; Port 5 of U8 is connected to one end of C17, the other end of C17 is grounded, port 5 of U8 is connected to port 1 and one end of R18, the other end of R18 is connected to one end of C18, and port 2 of U8 is grounded and the other end of C18.

9. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The system control software is developed using C language and interacts with each unit through a communication protocol.

10. The laser radar signal processing and control device based on an embedded system according to claim 1, characterized in that: The system control software control platform interaction process includes: module initialization, equipment self-check, waiting for server instructions, echo signal acquisition and data storage.

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