A Laser Terminal Transfer Function Testing System and Method Based on Beam Servo

Abstract

The present invention belongs to the field of space laser communication, and particularly relates to a laser terminal transfer function test system and method based on beam servo. The fiber laser is used to emit tracking light; the optical frequency sweeping module is used to simulate dynamic tracking spots and provide dynamic tracking light for the communication terminal; the sub-optical path module is used to realize the change of the optical path; the monitoring and acquisition module is used to monitor the spot position in real time and display it dynamically; the control and analysis module is used to process the data read by the control board. The present invention is used to solve the problem of the influence of random interference in the optical signal transmission process and the vibration of the installation platform on the tracking accuracy of the laser terminal in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of space laser communication, and particularly relates to a laser terminal transfer function testing system and method based on beam servo. Background Art

[0002] Laser communication usually uses optical fibers or free space to transmit signals, and can achieve high-speed, high-bandwidth, and long-distance communication. Compared with microwave communication, laser communication has a faster transmission rate, a larger communication capacity, smaller terminal volume and power consumption, and stronger anti-interference ability and security. Based on the above characteristics, laser terminals are gradually widely carried on satellite, aircraft, and airship platforms.

[0003] Currently, laser terminals are developing towards miniaturization and light weight, which puts higher requirements on their tracking accuracy. Random interference during the transmission of optical signals and vibrations of the laser terminal installation platform pose challenges to the establishment and stability of the laser terminal communication link. Summary of the Invention

[0004] The present invention provides a laser terminal transfer function testing system and method based on beam servo to solve the problem of the influence of random interference during signal transmission and vibrations of the laser terminal installation platform on tracking accuracy in the prior art.

[0005] The present invention is achieved through the following technical solutions:

[0006] A laser terminal transfer function testing system based on beam servo, the laser terminal transfer function testing system includes a fiber laser, an optical frequency sweeping module, a sub-optical path module, a monitoring and acquisition module, and a control and analysis module. The control and analysis module is connected to the monitoring and acquisition module, and the monitoring and acquisition module is respectively connected to the optical frequency sweeping module and the sub-optical path module;

[0007] The fiber laser is used to emit tracking light;

[0008] The optical frequency sweeping module is used to realize dynamic tracking spot simulation and provide dynamic tracking light for the communication terminal;

[0009] The sub-optical path module is used to realize the change of the optical path;

[0010] The monitoring and acquisition module is used to monitor the spot position in real time and display it dynamically;

[0011] The control and analysis module is used to realize the processing of the data read by the control board.

[0012] Further, the tracking light emitted by the fiber laser 1 is reflected by the fast steering mirror FSM2 installed at 45°, and then the light transmitted through the beam splitter 3 is reflected by the mirror 4 and sequentially passes through the secondary mirror 7-1, the primary mirror 7-2, and the off-axis collimator 7-3 to the laser terminal 10 to be measured, providing a moving target for it.

[0013] The light reflected by the beam splitter 3 is reflected by the retroreflector 8 and then converges to the camera 9 to characterize the tracking light.

[0014] The light emitted by the laser terminal 10 to be measured passes through the off-axis collimator 7-3, sequentially passes through the primary mirror 7-2 and the secondary mirror 7-1, and then is reflected by the mirror 4. After being processed by the optical tube beam reduction, it is reflected by the beam splitter 3 and focused on the camera 9 to characterize the light emitted by the terminal.

[0015] Further, the fast steering mirror FSM2 installed at 45° of the optical frequency sweeping module and the driver of the optical frequency sweeping module transmit signals bidirectionally through a serial port. The camera 9 of the monitoring and acquisition module communicates with the image tracking board of the monitoring and acquisition module through a Cameralink interface to transmit signals.

[0016] The driver of the optical frequency sweeping module and the image tracking board of the monitoring and acquisition module both transmit signals bidirectionally through a serial port with the control board of the control and analysis module. The control board of the control and analysis module transmits signals bidirectionally through a serial port with the upper computer of the control and analysis module. The upper computer of the control and analysis module transmits signals bidirectionally through a serial port with the display screen of the industrial computer of the control and analysis module.

[0017] The industrial computer of the control and analysis module completes control and analysis through the analysis software of the upper computer.

[0018] A method for testing the transfer function of a laser terminal based on beam servo, the method for testing the transfer function of the laser terminal specifically includes the following steps:

[0019] Step 1: Assemble and debug the testing system for the transfer function of the laser terminal based on beam servo.

[0020] Step 2: The control and analysis module uses the off-target amount of the tracking spot and the emission spot to identify the mathematical model of the laser terminal to be measured and analyzes it.

[0021] Step 3: Based on the analysis in Step 2, obtain the control system parameters of the laser terminal to be measured.

[0022] Further, the analysis method in Step 2 includes the following steps:

[0023] Step 2.1: The tracking spot is used as the input u(k) of the laser terminal to be measured, and the emitting spot is used as the output y(k) of the laser terminal to be measured. When performing spectral analysis on the signal, according to the information set by the user for frequency sweeping, a model of the DFT function is constructed;

[0024] Step 2.2: The tracking accuracy is statistically analyzed based on the positions of the tracking spot and the emitting spot. The tracking error is defined as: e(k) = u(k) - y(k). Calculate and statistically analyze the RMS for all the stored data, which is the tracking accuracy of the laser terminal to be measured.

[0025] Furthermore, the specific construction of the DFT function model in Step 2.1 is as follows,

[0026] (1)

[0027] where N is the number of points of the time-domain discrete signal, n is the number of the time-domain discrete signal, k is the number of the frequency-domain signal, and the number of points of the frequency-domain signal is also N. According to Euler's formula:

[0028] (2)

[0029] The discrete Fourier transform is written in the following form:

[0030]

[0031] (3)

[0032] The system discretely samples the signal based on the frequency fs, obtaining a discrete input signal with N sampling points. Subsequently, during the calculation of the DFT, the sampling point N in the sine / cosine expression is used as the independent variable. According to the DFT calculation formula, the complex-domain representation form of the frequency-domain signal with the highest correlation with the sample is obtained. Through the real and imaginary part information, the amplitude and phase information of the input signal can be obtained. Similarly, by processing the input u(k) of the laser terminal to be measured and the output y(k) of the laser terminal to be measured respectively, the amplitude-frequency and phase-frequency characteristic curves of the closed-loop system, that is, the closed-loop Bode plot, can be obtained.

[0033] Furthermore, Step 3 is specifically as follows: Based on Step 2, the closed-loop mathematical model of the laser terminal can be measured, and the control bandwidth, error suppression bandwidth, and tracking accuracy parameters of the system can be obtained, thereby obtaining the open-loop frequency response of the laser terminal and the open-loop cut-off frequency and stability margin parameters.

[0034] Further, assuming that the laser terminal to be measured is a unit negative feedback system, when analyzing the open-loop transfer function of the system, with the input being e(k) and the output being y(k), the amplitude-frequency and phase-frequency characteristic curves of the open-loop system, i.e., the open-loop Bode plot, can be obtained by processing the data using the method in Step 2.1; in the open-loop Bode plot, the frequency at which the amplitude is 0 dB is the open-loop cut-off frequency, and the phase difference between the corresponding phase at this time and the -180° phase is the phase margin.

[0035] The tracking spot is used as the input u(k) of the laser terminal to be measured, and the position of the tracking error spot is used as the output e(k), or the real-time difference between the tracking spot and the emission spot positions in Step 2.1 is used as the tracking error output. By using the DFT method in Step 2.1 for analysis, the error transfer frequency characteristic curve of the laser terminal to be measured, i.e., the Bode plot of the error transfer function, can be obtained.

[0036] In the Bode plot of the error transfer function, the frequency point corresponding to an amplitude of -3 dB is the error suppression bandwidth of the system.

[0037] A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the above-described method is implemented.

[0038] The beneficial effects of the present invention are as follows:

[0039] The present invention can image the tracking spot and the emission spot in a partitioned manner in the same camera, eliminating the need for additional time synchronization and other requirements, and also excluding the differences in the performance of the camera itself. It is used to solve the problem that if two spots are each collected by a separate camera, in order to ensure that the spots are imaged at the same moment, an additional time synchronization signal needs to be sent, and the unequal delays of the hardware and the differences in the performance of different cameras increase the complexity of subsequent analysis.

[0040] The present invention uses the method of beam measurement to modularly analyze the transfer function test system, and conducts research and analysis on key technologies such as dynamic optical frequency sweeping, dual-spot centroid extraction, and high-efficiency multi-mode model identification algorithms. It simulates the alignment and tracking process of the laser terminal, providing a test method and system for analyzing the servo performance of the laser terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the present invention.

[0042] Figure 2 is the system optical path diagram of the present invention.

[0043] Figure 3 is the flowchart of the optical signal and electrical signal of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] In the following description, specific details such as specific system architectures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0045] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0046] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification of the present application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0047] The following combines the appended Figures 1-3 to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0048] Many specific details are set forth in the following description in order to provide a thorough understanding of the present application, but the present application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0049] Embodiment 1

[0050] This embodiment provides a laser terminal transfer function testing system based on beam servo. The laser terminal transfer function testing system includes a laser, an optical frequency sweeping module, a sub-optical path module, a monitoring and acquisition module, and a control and analysis module. The control and analysis module is connected to the monitoring and acquisition module, and the monitoring and acquisition module is respectively connected to the optical frequency sweeping module and the sub-optical path module;

[0051] The fiber laser is used to emit tracking light;

[0052] The optical frequency sweeping module is used to implement dynamic tracking spot simulation and provide dynamic tracking light for the communication terminal;

[0053] The sub-optical path module is used to realize the change of the optical path;

[0054] The monitoring and acquisition module is used to monitor the light spot position in real time and display it dynamically;

[0055] The control analysis module is used to process the data read from the control panel.

[0056] Furthermore, the tracking light emitted by the fiber laser 1 is reflected by the fast reflector FSM2 installed at 45 degrees, and the light transmitted by the beam splitter 3 is then reflected by the reflector 4 and sequentially passes through the secondary mirror 7-1, the primary mirror 7-2 and the off-axis parallel light pipe 7-3 to the laser terminal 10 to be measured, providing a moving target for it;

[0057] The light reflected by the beam splitter 3 is reflected by the return reflector 8 and converges to the camera 9, representing the tracking light;

[0058] The light emitted by the laser terminal 10 to be tested passes through the off-axis collimator 7-3, then passes through the primary mirror 7-2 and the secondary mirror 7-1, and then is reflected by the reflector 4, and then is beam-contracted by the light pipe, and then reflected by the beam splitter 3 and focused to the camera 9, representing the terminal emitted light.

[0059] The tracking light emitted by the fiber laser 1 is transmitted to the off-axis parallel light pipe 7-3 of the sub-optical path module and the camera 9 of the monitoring and acquisition module respectively through the fast reflection mirror FSM2 installed at 45 degrees of the optical scanning system and the beam splitter 3 of the sub-optical path module;

[0060] The tracking light is sent to the laser terminal 10 to be measured through the off-axis collimator 7-3 to track the moving target;

[0061] The terminal emission light emitted by the laser terminal 10 to be tested passes through the off-axis parallel light pipe 7-3 to the beam splitter 3 of the sub-optical path module, and the beam splitter 3 of the sub-optical path module transmits the terminal emission light to the camera 9 of the monitoring and acquisition module. This beam of light does not reach the fast mirror, and the wavelength characteristics of the beam splitter cause the terminal emission light to be unable to pass through and reach the fast mirror.

[0062] Furthermore, the 45° mounted fast reflection mirror FSM2 of the optical scanning module and the driver of the optical scanning module transmit signals bidirectionally via the serial port, and the camera 9 of the monitoring and acquisition module communicates with the image tracking board of the monitoring and acquisition module via the Cameralink interface to transmit signals;

[0063] The driver of the optical frequency scanning module and the image tracking board of the monitoring and acquisition module transmit signals to the control board of the control and analysis module via the serial port in both directions. The control board of the control and analysis module transmits signals to the host computer of the control and analysis module via the serial port in both directions. The host computer of the control and analysis module transmits signals to the display screen of the industrial computer of the control and analysis module via the serial port in both directions.

[0064] The industrial computer of the control analysis module completes control analysis through the analysis software of the host computer.

[0065] Specifically, the sub-optical path module cooperates with the optical frequency sweeping module. The optical frequency sweeping module sets the vibration simulator parameters according to the user interaction information, and simulates the target equivalent motion information, common random interference factors in the optical signal transmission process, and the vibration characteristics of the terminal platform.

[0066] The tracking light emitted by the laser in the transfer function test system is reflected by the fast steering mirror installed at 45°. Part of the light passes through the energy beam splitter and is reflected by the mirror and then passes through the off-axis collimator to the laser terminal to provide a moving target. Part of the light is first reflected by the energy beam splitter and then reflected by the retroreflector and converges to the camera and enters the monitoring and acquisition module; the laser terminal also emits a beam of light. This light is reflected by the mirror through the off-axis collimator, then undergoes beam shrinking processing by the light pipe, and is reflected by the beam splitter and focused on the camera and enters the monitoring and acquisition module.

[0067] The motion information simulated by the optical frequency sweeping module is achieved through the fast steering mirror (i.e., the vibration simulator). Since the vibration information that the system can simulate has a frequency up to 1 kHz, the fast steering mirror requires a very high drive control bandwidth to simulate the motion information: sine wave, white noise, PSD vibration spectrum (up to 1 kHz).

[0068] The monitoring and acquisition module provides analysis data for the control analysis module by simultaneously collecting the spot positions of the tracking light and the emitted light. The camera in the monitoring and acquisition module can image the tracking spot and the emitted spot in different areas, reducing the complexity of the software and hardware design caused by the asynchrony of imaging between different cameras. The image tracking board in the monitoring and acquisition module processes the received spots using three algorithms: image segmentation, centroid extraction, and position calculation.

[0069] In the image tracking board, the camera simultaneously detects 2 spots, so the number of targets in the image is 2. By default, the vertical direction in the middle of the image is used as the dividing line (configurable). The dividing line divides the image into a left image and a right image, with 1 target in the left image and 1 target in the right image. When an external device sends the position of the image dividing line to the image tracking board, the priority of this dividing line position is higher than the default dividing line position.

[0070] The image tracking board first calculates the thresholds of the left image and the right image. When the image gray value is less than the threshold, it is considered background or noise. The centroid algorithm is used to calculate the abscissa and ordinate of the target in the left image for the pixel points with gray values greater than the threshold in the left image. The centroid algorithm is used to calculate the abscissa and ordinate of the target in the right image for the pixel points with gray values greater than the threshold in the right image.

[0071] In the control and analysis module, the control system analysis software is the core, which mainly includes functions such as signal output, data processing and analysis, and information interaction. It can configure camera parameters and vibration simulator parameters, output a variety of different sweep signal types, parse and analyze the read tracking spot and emission spot position data, and display the results.

[0072] The laser terminal transmission test system based on beam servo tests the closed-loop and open-loop mathematical models of the laser terminal based on the dynamic optical closed-loop frequency sweep method to evaluate the servo performance of the laser terminal. At the same time, the beam measurement method is used to more directly simulate the actual working state of the laser terminal, which helps to improve the servo performance of the laser terminal. It can provide ground testing for on-board laser terminals, further improve the tracking performance of laser terminals, and provide guarantee for the stability of laser communication links.

[0073] Implementation Method 2

[0074] A laser terminal transmission function test method based on beam servo, the laser terminal transmission function test method specifically comprises the following steps:

[0075] Step 1: Assemble and debug the laser terminal transmission test system based on beam servo;

[0076] Specifically, the fiber laser is used to emit tracking light;

[0077] The optical frequency scanning module is used to realize dynamic tracking light spot simulation and provide dynamic tracking light for the communication terminal;

[0078] The sub-optical path module is used to realize the change of the optical path;

[0079] The monitoring and acquisition module is used to monitor the light spot position in real time and display it dynamically;

[0080] The control analysis module is used to process the data read from the control panel.

[0081] Furthermore, the tracking light emitted by the fiber laser 1 is reflected by the fast reflector FSM2 installed at 45 degrees, and the light transmitted by the beam splitter 3 is then reflected by the reflector 4 and sequentially passes through the secondary mirror 7-1, the primary mirror 7-2 and the off-axis parallel light pipe 7-3 to the laser terminal 10 to be measured, providing a moving target for it;

[0082] The light reflected by the beam splitter 3 is reflected by the return reflector 8 and converges to the camera 9, representing the tracking light;

[0083] The light emitted by the laser terminal 10 to be tested passes through the off-axis collimator 7-3, then passes through the primary mirror 7-2 and the secondary mirror 7-1, and then is reflected by the reflector 4, and then is beam-contracted by the light pipe, and then reflected by the beam splitter 3 and focused to the camera 9, representing the terminal emitted light.

[0084] Step 2: The control analysis system uses the off - target amount of the tracking light spot and the emission light spot to identify the mathematical model of the laser terminal to be measured and analyzes it.

[0085] Step 3: Based on the analysis in Step 2, the control system parameters of the laser terminal to be measured are obtained.

[0086] Furthermore, the analysis method in Step 2 includes the following steps.

[0087] Step 2.1: Regarding the tracking light spot as the input u(k) of the laser terminal to be measured and the emission light spot as the output y(k) of the laser terminal to be measured, when performing spectral analysis on the signal, according to the information set by the user for frequency sweeping, a model of the DFT function is constructed.

[0088] Step 2.2: According to the positions of the tracking light spot and the emission light spot, the tracking accuracy is statistically analyzed. The tracking error is defined as: e(k)=u(k) - y(k). Calculate and statistically analyze the RMS for all the stored data, which is the tracking accuracy of the laser terminal to be measured.

[0089] Furthermore, the specific construction of the DFT function model in Step 2.1 is as follows.

[0090] (1)

[0091] Among them, N is the number of points of the time - domain discrete signal, n is the number of the time - domain discrete signal, with the value range from 0 to N - 1, k is the number of the frequency - domain signal, with the value range from 0 to N - 1, and the number of points of the frequency - domain signal is also N. According to Euler's formula:

[0092] (2)

[0093] The discrete Fourier transform is written in the following form:

[0094]

[0095] (3)

[0096] The system discretely samples the signal based on the frequency fs, obtaining a discrete input signal with the number of sampling points N. Subsequently, during the calculation of the DFT, taking the sampling point N in the sine / cosine expression as the independent variable, according to the DFT calculation formula, the complex - domain representation form of the frequency - domain signal with the highest correlation with the sample is obtained. Through the real - part and imaginary - part information, the amplitude and phase information of the input signal can be obtained. Similarly, by processing the system input u(k) and the system output y(k) respectively, the amplitude - frequency and phase - frequency characteristic curves of the closed - loop system, that is, the closed - loop Bode plot, can be obtained. In the closed - loop Bode plot, the frequency point corresponding to an amplitude attenuation of 3 dB or a phase lag of 90° is the closed - loop control bandwidth.

[0097] Further, the specific content of step 3 is as follows: based on the closed-loop mathematical model of the laser terminal measured in step 2, parameters such as the control bandwidth, error suppression bandwidth, and tracking accuracy of the system are obtained, thereby obtaining the open-loop frequency response of the laser terminal and parameters such as the open-loop cut-off frequency and stability margin.

[0098] Further, assuming that the laser terminal to be measured is a unit negative feedback system, when analyzing the open-loop transfer function of the system, the input is e(k) and the output is y(k). By using the method in step 2.1 to process the data, the amplitude-frequency and phase-frequency characteristic curves of the open-loop system, that is, the open-loop Bode plot, can be obtained. In the open-loop Bode plot, the frequency at which the amplitude is 0 dB is the open-loop cut-off frequency, and the phase difference between the corresponding phase at this time and the -180° phase is the phase margin.

[0099] The tracking spot is used as the input u(k) of the laser terminal to be measured, and the position of the tracking error spot is used as the output e(k). Or, the real-time difference between the tracking spot and the emission spot position in step 2.1 is used as the tracking error output. By using the DFT method in step 2.1 for analysis, the error transfer frequency characteristic curve of the laser terminal to be measured, that is, the error transfer function Bode plot, can be obtained.

[0100] In the error transfer function Bode plot, the frequency point corresponding to the amplitude of -3 dB is the error suppression bandwidth of the system.

[0101] It can also be described as follows: according to the miss distance between the tracking spot emitted by the transfer function test system and the emission spot emitted by the laser terminal to be measured, the discrete Fourier analysis method is used for analysis to identify the mathematical model of the laser terminal to be measured. The tracking spot is used as the input u(k) of the laser terminal to be measured, and the emission spot is used as the output y(k) of the laser terminal to be measured for spectral analysis of the signal. The system discretely samples the system input u(k) and the system output y(k) signals based on the frequency fs (i.e., the image frame rate), obtaining a discrete input signal with the number of sampling points N. According to the DFT calculation formula, the complex domain representation form of the frequency domain signal with the highest correlation with the sample is obtained. Through the real and imaginary part information, the amplitude-frequency and phase-frequency characteristic curves of the closed-loop system, that is, the closed-loop Bode plot, can be obtained. In the closed-loop Bode plot, the frequency point corresponding to the amplitude attenuation of 3 dB or the phase lag of 90° is the closed-loop control bandwidth; according to the positions of the tracking spot and the emission spot, the tracking accuracy is statistically analyzed. The tracking error is defined as: e(k) = u(k) - y(k). Calculating and statistically analyzing the RMS for all stored data is the tracking accuracy of the laser terminal to be measured; assuming that the laser terminal to be measured is a unit negative feedback system, when analyzing the open-loop transfer function of the system, the input is e(k) and the output is y(k). By using the discrete Fourier analysis method to process the data, the amplitude-frequency and phase-frequency characteristic curves of the open-loop system, that is, the open-loop Bode plot, can be obtained. In the open-loop Bode plot, the frequency at which the amplitude is 0 dB is the open-loop cut-off frequency, and the phase difference between the corresponding phase at this time and the -180° phase is the phase margin.

[0102] Embodiment 3

[0103] An embodiment of the present invention provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. Among them, the memory is used to store software programs and modules. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory. The memory and the processor are connected through a bus. Specifically, when the processor runs the computer program stored in the memory, any step in the first embodiment is implemented.

[0104] It should be understood that in the embodiment of the present invention, the so-called processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0105] The memory may include a read-only memory, a flash memory, and a random access memory, and provide instructions and data to the processor. A part or all of the memory may also include a non-volatile random access memory.

[0106] As can be seen from the above, the electronic device provided by the embodiment of the present invention can implement the laser terminal transfer function test method based on beam servo as described in Embodiment 2 by running a computer program. Based on the system of Embodiment 1, the discrete Fourier analysis method is used to analyze the tracking spot and the emission spot, and the amplitude-frequency and phase-frequency characteristic curves of the closed-loop system of the laser terminal to be measured can be obtained, that is, the closed-loop Bode plot. The amplitude-frequency and phase-frequency characteristic curves of the open-loop system, that is, the open-loop Bode plot, can also be obtained. At the same time, the difference between the positions of the tracking spot and the emission spot is used as the tracking error output in real time, and the discrete Fourier analysis method is used for analysis, and the error transfer frequency characteristic curve of the laser terminal to be measured, that is, the error transfer function Bode plot, can be obtained.

[0107] It should be understood that if the above integrated modules / units are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-described implementation manners of the present invention can also be completed by a computer program instructing relevant hardware. The above computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-described various method embodiments can be implemented. Among them, the above computer program includes computer program code, and the above computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The above computer-readable medium can include: any entity or device capable of carrying the above computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the above computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0108] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0109] Those skilled in the art can clearly understand that for the convenience and brevity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the above device can be divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiments can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of the functional units and modules are only for the convenience of mutual distinction and do not limit the protection scope of the present invention. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0110] It should be noted that the methods and their detailed examples provided in the above embodiments can be combined into the devices and equipment provided in the embodiments, and reference can be made to each other, and will not be elaborated here.

[0111] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0112] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminal devices and methods can be implemented in other ways. For example, the device / equipment embodiments described above are merely illustrative. For example, the above division of modules or units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0113] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A laser terminal transfer function testing system based on beam servo, characterized in that, The laser terminal transfer function test system includes a fiber laser, an optical frequency sweeping module, a sub-optical path module, a monitoring and acquisition module, and a control and analysis module. The control and analysis module is connected to the monitoring and acquisition module, and the monitoring and acquisition module is respectively connected to the optical frequency sweeping module and the sub-optical path module; The fiber laser is used to emit tracking light; The optical frequency sweeping module is used to simulate a dynamic tracking spot and provide dynamic tracking light for the laser terminal to be tested; The sub-optical path module is used to realize the change of the optical path; The monitoring and acquisition module is used to monitor the spot position in real time and display it dynamically; The control and analysis module is used to process the data read by the control board; The optical frequency sweeping module includes a fast steering mirror FSM (2) installed at 45°, the monitoring and acquisition module includes a camera (9), and the sub-optical path module includes a beam splitter (3) and an off-axis collimator (7-3); The tracking light emitted by the fiber laser (1) is reflected by the fast steering mirror FSM (2) installed at 45°, and then the light transmitted through the beam splitter (3) is reflected by the reflecting mirror (4) and sequentially passes through the secondary mirror (7-1), the primary mirror (7-2), and the off-axis collimator (7-3) to the laser terminal to be tested (10) to provide a moving target for it; The light reflected by the beam splitter (3) is reflected by the retroreflector (8) and then converges to the camera (9) to characterize the tracking light; The light emitted by the laser terminal to be tested (10) passes through the off-axis collimator (7-3), then passes through the primary mirror (7-2) and the secondary mirror (7-1) in sequence, and then is reflected by the reflecting mirror (4), and after being processed by the optical tube beam shrinking, it is reflected by the beam splitter (3) and focused on the camera (9) to characterize the light emitted by the terminal; 2. The laser terminal transfer function testing system according to claim 1, wherein, The fast steering mirror FSM (2) installed at 45° of the optical frequency sweeping module transmits signals bidirectionally with the driver of the optical frequency sweeping module through a serial port. The camera (9) of the monitoring and acquisition module communicates with the image tracking board of the monitoring and acquisition module through a Cameralink interface to transmit signals; The driver of the optical frequency sweeping module and the image tracking board of the monitoring and acquisition module both transmit signals bidirectionally with the control board of the control and analysis module through a serial port. The control board of the control and analysis module transmits signals bidirectionally with the upper computer of the control and analysis module through a serial port. The upper computer of the control and analysis module transmits signals bidirectionally with the display screen of the industrial computer of the control and analysis module through a serial port; The industrial computer of the control and analysis module completes control and analysis through the analysis software of the upper computer.

3. A method for testing the transfer function of a laser terminal based on beam servo, characterized in that, The laser terminal transfer function test method specifically includes the following steps, Step 1: Assemble and debug the laser terminal transfer function test system based on beam servo as described in claim 1; Step 2: The control and analysis module uses the miss distance of the tracking spot and the emission spot to identify the mathematical model of the laser terminal to be tested and analyze it; Step 3: Based on the analysis in Step 2, obtain the control system parameters of the laser terminal to be tested; The analysis method in Step 2 includes the following steps, Step 2.1: The tracking spot is used as the input u(k) of the laser terminal to be measured, and the emission spot is used as the output y(k) of the laser terminal to be measured. When performing spectral analysis on the signal, a model of the DFT function is constructed according to the information set by the user for frequency sweeping; Step 2.2: The tracking accuracy is statistically analyzed based on the positions of the tracking spot and the emission spot. The tracking error is defined as: e(k) = u(k) - y(k). Calculate and statistically analyze the RMS for all the stored data, which is the tracking accuracy of the laser terminal to be measured.

4. The laser terminal transfer function testing method according to claim 3, wherein The specific construction of the DFT function model in Step 2.1 is as follows: (1) Among them, N is the number of points of the time-domain discrete signal, n is the number of the time-domain discrete signal, k is the number of the frequency-domain signal, and the number of points of the frequency-domain signal is also N. According to Euler's formula: (2) The discrete Fourier transform is written in the following form: (3) The system discretely samples the signal based on the frequency fs, obtaining a discrete input signal with N sampling points. Subsequently, during the calculation of the DFT, the sampling point N in the sine / cosine expression is used as the independent variable. According to the DFT calculation formula, the complex-domain representation form of the frequency-domain signal with the highest correlation with the sample is obtained. The amplitude and phase information of the input signal can be obtained through the real and imaginary part information; similarly, by processing the input u(k) of the laser terminal to be measured and the output y(k) of the laser terminal to be measured respectively, the amplitude-frequency and phase-frequency characteristic curves of the closed-loop system, that is, the closed-loop Bode plot, can be obtained.

5. The laser terminal transfer function testing method according to claim 3, wherein The specific content of Step 3 is as follows: Based on Step 2, the closed-loop mathematical model of the laser terminal to be measured can be measured, and the control bandwidth, error suppression bandwidth, and tracking accuracy parameters of the system can be obtained, thereby obtaining the open-loop frequency response of the laser terminal to be measured and obtaining the open-loop cut-off frequency and stability margin parameters.

6. The laser terminal transfer function testing method according to claim 5, wherein Assume that the laser terminal to be measured is a unit negative feedback system. When analyzing the open-loop transfer function of the system, the input is e(k) and the output is y(k). By using the method in Step 2.1 to process the data, the amplitude-frequency and phase-frequency characteristic curves of the open-loop system, that is, the open-loop Bode plot, can be obtained; in the open-loop Bode plot, the frequency at which the amplitude is 0 dB is the open-loop cut-off frequency, and the phase difference between the corresponding phase at this time and the phase of -180° is the phase margin; The tracking spot is used as the input u(k) of the laser terminal to be measured, and the position of the tracking error spot is used as the output e(k), or the difference between the positions of the tracking spot and the emission spot in real time in Step 2.1 is used as the tracking error output. By using the DFT method in Step 2.1 for analysis, the error transfer frequency characteristic curve of the laser terminal to be measured, that is, the error transfer function Bode plot, can be obtained; In the error transfer function Bode plot, the frequency point corresponding to the amplitude of -3 dB is the error suppression bandwidth of the system.

7. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method described in any one of claims 3-6 is implemented.

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