Multi-channel GNSS navigation signal simulation system based on cloud architecture

Abstract

The invention discloses a multi-channel GNSS (Global Navigation Satellite System) navigation signal simulation system based on a cloud architecture, which adopts a distributed system architecture based on the cloud architecture to realize parallel testing of different spacecrafts, simulation of the different spacecrafts at any moment and random access of user tracks. A modular general signal simulation module and unified interface parameters are designed, the frequency point reconfigurable function is achieved, hardware is not changed, and the system is suitable for compatible simulation and testing of any constellation and any frequency point combination of a user terminal. The test equipment configuration number is reduced, the joint test requirements of parallel modular flight, butt joint and the like of multi-model spacecrafts are met, and the development cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of spacecraft system-level testing, and in particular to a multi-channel GNSS navigation signal simulation system based on cloud architecture. Background Art

[0002] Currently, the number of spacecraft launch missions has increased dramatically, and the demand for spacecraft testing has grown exponentially. Various types of navigation terminals are widely used on spacecraft. The GNSS navigation signal simulation system is an important test equipment for verifying the positioning function of satellite navigation terminals. However, the existing satellite navigation signal simulation system cannot meet the needs of multi-user spacecraft parallel testing. The disadvantages of traditional satellite navigation signal simulators are:

[0003] (1) Traditional spacecraft testing uses a single-channel or dual-channel satellite navigation simulation system. Each spacecraft test requires a separate navigation simulation system, and multiple spacecraft tests cannot share the same simulation system.

[0004] (2) Before simulating the signal of the navigation simulation system, it is usually necessary to centrally perform scene configuration and mathematical calculations, distribute the simulation data to the signal generation module, and simulate all users and frequency points of the navigation simulation system at the same time. This makes it impossible to meet the independent testing requirements of different users for different scenes, different simulation times, and random access.

[0005] (3) The signal generation module of the navigation simulation system is usually fixed or solidified during simulation, resulting in low efficiency in hardware resource utilization and poor integration.

[0006] (4) Most traditional satellite navigation simulation systems have fixed navigation system frequencies in hardware, without considering the compatibility and interoperability requirements of multiple systems under a unified platform. They are unable to support the reconfigurable frequency of navigation satellite signals and are unable to adapt to the scalability requirements of new user navigation terminals. Summary of the invention

[0007] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a multi-channel GNSS navigation signal simulation system based on a cloud architecture, and to adopt a distributed system architecture based on a cloud architecture to solve the problems that the prior art cannot realize parallel testing of different spacecraft, simulation of different spacecraft at any time, and random access to user orbits; in view of the problems of poor interoperability and compatibility of multiple systems of the navigation signal simulation system, a modular universal signal generation unit and unified interface parameters are designed to realize the frequency reconfigurable function without changing the hardware, and to adapt to compatible simulation and testing of any constellation and any frequency combination of user terminals.

[0008] The technical solution of the present invention is: a multi-channel GNSS navigation signal simulation system based on cloud architecture, including: a network communication module, a comprehensive management module, several background service modules, and a simulation source module;

[0009] Network communication module, used for network switching, allowing users in different network segments to use the simulation system simultaneously;

[0010] The comprehensive management module is used to allocate user channel resources, build the corresponding relationship between each background service module and the user channel, and cooperate with the network communication module, background service module and simulation source module to complete the online reconstruction of system frequency points, network segment IP configuration, simulation scenario configuration and track injection;

[0011] The backend service module is the information exchange medium between the integrated management module and the simulation source module. Each backend service module receives the output information of the integrated management module and sends it to the simulation source module according to the corresponding relationship between user channels, and forwards the reported information of the simulation source module to the integrated management module;

[0012] The simulation source module takes the universal signal generating unit as the smallest unit. Each universal signal generating unit is combined on demand according to the user's generation frequency requirements. Each combination is controlled by the background service module corresponding to the user channel. The parameters obtained through online reconstruction of the system frequency, simulation scene configuration and track injection in the user channel are used to generate navigation simulation signals of multiple frequencies required by the corresponding user. Each universal signal generating unit is independent of each other, with a unified interface and dynamic parameter configuration.

[0013] Furthermore, the integrated management module is a cloud platform client, which is deployed on multiple local or remote computers in the simulation system and supports simultaneous access by multiple users.

[0014] Furthermore, a correspondence between each backend service module and the user channel is constructed, including: the comprehensive management module configures the backend service module into a corresponding user channel correspondence for a single user, a dual user or a multi-user; in a single-user test site, one backend service module corresponds to one user channel, in a dual-user test site, one backend service module corresponds to two user channels, and in a multi-user test site, one backend service module corresponds to the same number of user channels as the number of users.

[0015] Furthermore, the system frequency is reconstructed online, including: the integrated management module independently and collaboratively controls the corresponding universal signal generation unit for users who need frequency reconstruction through the background service module corresponding to the user channel, and uses the background service module to inject the navigation satellite frequency signal waveform characteristic configuration parameters into the universal signal generation unit in standard format data online, and completes the online reconstruction of the signal frequency level by reconstructing parameters without changing the analog system hardware conditions.

[0016] Furthermore, the navigation satellite frequency signal waveform characteristic configuration parameters include: carrier frequency, code rate, information rate, symbol rate, modulation mode and service type.

[0017] Furthermore, the network segment IP configuration includes: the comprehensive management module configures the network segment of each user channel and the port IP of the background service module, and through the network communication module and the background service module, users with different IPs in the same network segment or different network segments can individually control each user channel.

[0018] Furthermore, the port IP and communication protocol of each background service module are independently configured, and the port IPs are different.

[0019] Furthermore, the simulation scene configuration includes: the integrated management module receives the user control instruction and configures the simulation scene corresponding to the user channel; each user channel can configure and store multiple simulation scene files, and the scene configuration of the corresponding channel is completed directly by calling the simulation scene file.

[0020] Furthermore, orbit injection includes: the integrated management module receives user control instructions and injects the spacecraft orbit required by the user; the injection methods include: local injection and network injection. When local injection is used, the spacecraft orbit is calculated by inputting the six elements of the user's operating orbit and the starting point of the simulation time; when network injection is used, the spacecraft orbit is calculated and generated in real time according to the orbit point file in a fixed format.

[0021] Furthermore, the simulation system also includes:

[0022] The branch control module, for each user channel, synthesizes the navigation analog signals of multiple frequency points input into one navigation analog signal, and then divides it into user signals and self-test signals. The user signal is provided to the user for parallel testing of each user terminal, and the self-test signal is provided to the self-test module for self-testing each user channel;

[0023] A self-check module performs self-check using a self-check signal.

[0024] Furthermore, the user signals obtained by the branch control module include a high-power signal and a low-power signal. The signal power is determined by the user's needs, and according to the attenuation of each user channel signal, the high-power signal or the low-power signal is selected to be transmitted to the user terminal;

[0025] The self-test signal obtained by the branch control module enters the self-test module, and the self-test module includes:

[0026] The closed-loop detection module selects the multi-channel self-test signals output by the branch control module, and supports single-channel, dual-channel or multi-channel self-test signal selection;

[0027] The monitoring module receives the single-channel, two-channel or multi-channel self-test signals output by the closed-loop detection module and performs absolute positioning or differential positioning self-test.

[0028] The advantages of the present invention compared with the prior art are:

[0029] (1) The present invention innovatively combines cloud architecture with GNSS navigation simulation testing, cloudifies simulation resources, realizes the interconnection and interoperability of navigation systems, and aggregates and services resources on demand, thereby improving the utilization rate of device hardware resources.

[0030] (2) The technical solution proposed in the present invention, in the field of GNSS navigation simulation, realizes for the first time that the simulation system can access any network segment and any IP user at any time, and start generating navigation simulation signals at any time, and realizes online reconstruction at the frequency level based on a modular universal signal generation unit. The same unit can complete signal simulation of any orbit and any frequency.

[0031] (3) The present invention innovatively adopts a distributed structure, which is suitable for parallel testing of multiple spacecraft and meets the test and interpretation requirements of various types of user navigation receivers. The software control protocol and parameter reporting protocol can be configured, which has strong versatility and reduces the cost of equipment development.

[0032] (4) The technical solution of the present invention supports independent or joint analog signals between users, which is flexible.

[0033] (5) The navigation simulation system in the present invention provides functions such as equipment self-checking, equipment remote control, simulation parameter reporting, and status monitoring to meet the closed-loop test requirements of the spacecraft navigation terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the system architecture of the present invention. DETAILED DESCRIPTION

[0035] In order to better understand the technical solution of the present invention, the specific implementation mode of the present invention is described in detail below with reference to the accompanying drawings.

[0036] The multi-channel GNSS navigation signal simulation system based on cloud architecture (hereinafter referred to as the simulation system) proposed in the present invention adopts a unified interface to encapsulate and manage software for hardware, and provides a public method that is independent of specific applications to load upper-level application software onto the system for operation. By loading different application software to reconstruct system functions, the system has extremely strong flexibility and good functional scalability.

[0037] The simulation system can be accessed by any network segment and any IP user at any time, and the idle resources of the simulation system can be used to generate navigation simulation signals at any time, and the frequency of the navigation simulation signal can be reconfigured. Specifically, it includes:

[0038] The network communication module is used for network exchange, allowing users in different network segments to use the simulation system at the same time; it realizes independent control of user channels of users in different network segments, and can support external orbit simulators to inject the spacecraft orbit required by users.

[0039] Industrial computer, used to run the comprehensive management module and several background service modules;

[0040] Comprehensive management module: According to user needs, configure the correspondence between each background service module and the analog source module hardware user channel resources, and manage and control the analog system channel resources.

[0041] As the core control center of the entire system, the comprehensive management module controls and manages each back-end service module, realizes collaborative management of simulation scene editing management, simulation process control, simulation status monitoring, etc. of the simulation system, so as to ensure the coordination and synchronization among various components; it has the functions of operating control of other parts of the system, management of test items and processes, test data processing and evaluation, and output and storage of test results.

[0042] The comprehensive management module is a cloud platform client that supports deployment on multiple local or remote computers in the simulation system, supports simultaneous access by multiple users, and any user can use the idle resources of the simulation system. Based on the comprehensive management module, user channel resource configuration is implemented to achieve multi-user access and user channel resource sharing.

[0043] Backstage service module: The backstage service module is the information exchange intermediary between the integrated management module and the simulation source module. It receives the control instructions, simulation parameters, and configuration parameters of the integrated management module and converts them into standard format data and then forwards them to the corresponding general signal generation unit of the simulation source module. It also forwards the data reported by the simulation source module to the integrated management module according to the protocol. The port IP and communication protocol of each backstage service module are independently configured, and the port IPs are different.

[0044] The backend service module can be configured to correspond to the user channel, and the user channels can be grouped as needed. Multiple backend service modules run in the industrial computer, and the backend service module and each user channel have a 1-to-1 or 1-to-many relationship, that is, a backend service module can be configured to correspond to the user channel, and one backend service module can correspond to one channel, or one backend service module can correspond to multiple channels.

[0045] The analog source module takes several universal signal generating units as the smallest unit. The universal signal generating units are mainly composed of a mathematical simulation subsystem and a signal generating subsystem. The mathematical simulation subsystem and the signal generating subsystem of each frequency signal are integrated on the same hardware chip to generate navigation simulation signals of multiple frequencies required for each user channel under a unified time-frequency reference. The universal signal generating units are independent of each other, have unified interfaces, dynamically configured parameters, and are grouped as needed. The comprehensive management module controls the analog source module through the background service module.

[0046] The branch control module, for each user channel, synthesizes the navigation analog signals of multiple frequency points input into one navigation analog signal, and then divides it into user signals and self-test signals. The user signal is provided to the user for parallel testing of each user terminal, and the self-test signal is provided to the self-test module for self-testing each user channel;

[0047] The self-test module uses the self-test signal to perform self-test; it includes: a closed-loop detection module, which selects the multi-channel self-test signals output by the branch control module, and supports single-channel, two-channel or multi-channel self-test signal selection; a monitoring module, which receives the single-channel, two-channel or multi-channel self-test signals output by the closed-loop detection module, and performs absolute positioning or differential positioning self-test.

[0048] In this embodiment, Figure 1 As shown, the simulation system works, including:

[0049] Step 1: Channel resource allocation. The integrated management module implements the initialization configuration of the simulation source system. The user channel resources of the simulation system are allocated to the users of the n test sites on the integrated management module, and the corresponding relationship between each background service module and the user channel resources of the simulation source module is configured. When allocating user channel resources, if the user channel is occupied by other users, the configuration will fail, and the channel resources can only be used after other users have used up and released the resources. Among them, one background service module in a single-user test site corresponds to one user channel, supporting absolute positioning requirements; one background service module in a dual-user test site corresponds to two user channels, supporting absolute positioning and relative positioning requirements; one background service module in a multi-user test site corresponds to the same number of user channels as the number of users. Overall, the number of background service modules m ≤ the number of user channels n.

[0050] Step 2: Online reconstruction of the system frequency. The integrated management module and the background service module perform online frequency reconstruction for users who need frequency reconstruction. The integrated management module independently and collaboratively controls the general signal generation unit through the corresponding background service module. The background service module is used to inject the navigation satellite frequency signal waveform characteristic configuration parameters into the general signal generation unit online according to the standard format data. Without changing the analog system hardware conditions, the online reconstruction of the signal frequency level is completed by reconstructing the parameters. The signal waveform parameters that need to be configured for the reconstruction deployment include: carrier frequency, code rate, information rate, symbol rate, modulation method, service type, etc.

[0051] Step 3: Network segment IP configuration. Configure the network segment of each user channel and the port IP of the background service module on the integrated management module. Through the network communication module and the background service module, users of the test sites in the same network segment or different network segments and with different IP addresses can control each user channel individually.

[0052] Step 4: Simulation scenario configuration. The simulation scenarios corresponding to n test site users are configured through the integrated management module. Multiple simulation scenario files can be configured and stored for each test site user. When in use, the scenario configuration of the corresponding channel can be completed by directly calling in the configuration file. The simulation scenario configuration includes simulation time, satellite constellation model, clock error model, environmental error model, carrier orbit model, and abnormal simulation model. When user i of the test site is testing, the integrated management module receives the remote control command transmitted by the remote management software of the corresponding test site, calls in the scenario file according to the selected simulation scenario number, and completes the simulation scenario initialization of the corresponding channel.

[0053] Step 5: Orbit injection. When testing user i at the test site, the integrated management module receives the remote control command transmitted by the remote management software of the corresponding test site, and configures the spacecraft orbit of each user as either local input or network injection: ① When inputting locally, the initial state is set by inputting the six elements of the user's orbit and the simulation time starting point, and then the orbit is calculated; ② When injecting from the network, the user's orbit is generated in real time according to the orbit point file in a fixed format. Through the network communication module and the background service module, the spacecraft orbit of each user channel is injected into the corresponding background service module.

[0054] Step 6: Navigation simulation signal generation. When user i is tested at the test site, ① the integrated management module deployed locally or remotely sends control instructions and simulation parameters (including scene parameters and orbit parameters) to the background service module i; ② the background service module i receives the control instructions and simulation parameters, and forwards them to the corresponding user channel general signal generation unit of the simulation source module in standard format data, and controls and monitors the current user channel resources; ③ the general signal generation unit receives the simulation instructions and related data (including simulation parameters including scene parameters and orbit parameters, configuration parameters including navigation satellite frequency signal waveform characteristic configuration parameters) to the mathematical simulation subsystem. The mathematical simulation subsystem generates signal simulation data after analyzing the data or related parameters provided by the user according to the internal relevant simulation model operation, including the pseudorange of the satellite relative to the user, Doppler, Doppler change rate and the change rate of the Doppler change rate, and sends them to the signal generation subsystem. The signal generation subsystem accurately generates the user channel frequency RF signal according to the signal simulation data generated by the mathematical simulation subsystem. In this embodiment, each user channel includes four general signal generating units, which generate navigation simulation signals of four frequency points, including but not limited to navigation simulation signals of BDS B1, BDS B2, GPS L1, GPS L2 and other frequency points, and can be expanded to other frequency point signals of the global navigation system as needed; if the system needs to output more frequency points or more user signals, it can be achieved by increasing the number of general signal generating units.

[0055] Step 7: For each user channel, the navigation analog signals of multiple frequencies are synthesized and power controlled by the branch control module, combined into one navigation analog signal, and then branched into three signal outputs for each user, including one high-power signal (generally -30dBm, with adjustable signal power), one low-power signal output (with a fixed phase difference of 80dB from the high-power signal), and one self-test signal (the same as the low-power signal). By enabling and disabling signals, the corresponding navigation analog signal combined output can be provided to each user receiver with any one-frequency signal, any two-frequency signals, any three-frequency signals, any four-frequency signals and above in the configured frequency points.

[0056] Step 8: The high-power signal and low-power signal output by the split control module are selected to be transmitted to the user terminal according to the attenuation of each user link signal, and the speed measurement accuracy, positioning accuracy, sensitivity, and dynamic range of the user navigation terminal are tested to meet the parallel testing requirements of multiple user terminals;

[0057] Step 9: The multi-channel self-test signals output by the branch control module are selected by the closed-loop detection module to form two-channel signal output (any frequency combination), which are respectively input into the self-test receiver in the monitoring module to realize signal self-monitoring.

[0058] Step 10: The self-test receiver of the self-test module supports receiving all the frequency points configured by the analog source, and performs absolute positioning on the respective detection signals output by the closed-loop detection module. The absolute positioning data and related information data are sent out through the interface with the computer, and the relative positioning function is realized through the host computer software, and the relative position and relative speed are solved in real time.

[0059] Step 11: The integrated management module frames the satellite PRN, observation data, navigation message, power parameter, carrier trajectory and other signal simulation parameter information, simulation system status information, and self-test receiver positioning information obtained by simulation calculation of each user channel and reports them to the remote test management software.

[0060] Step 12: The integrated management module supports data storage and comparison with simulated source orbit data. The integrated management module displays and automatically records positioning status information (including the number of available satellites for each frequency point, signal-to-noise ratio, TIC information, positioning / non-positioning, three-dimensional position / speed / time) in real time, and provides positioning / non-positioning status, and the absolute time of each positioning and loss of positioning. The files are archived in ASCII code, and the file name contains the time (year, month, day, hour, minute, second) of the file creation time.

[0061] The present invention adopts a distributed architecture by designing a multi-channel navigation signal simulation system, and realizes user random access based on independent control of channel resources through the cooperation of a network communication module, a plurality of background service modules and a comprehensive management module. Any user can use the idle resources of the simulation system, use the simulated signal at any time and use it for testing. The simulation system adopts a unified hardware architecture, and the relevant functions are realized by the upper-level application software. It has the ability to change the function of the device by installing different application software, using different configurations, and adding or reducing hardware modules. The multi-channel navigation signal simulation system breaks through the integrated design concept of the traditional navigation simulator structure, adopts a distributed architecture, and the minimum unit of the system is a universal signal generation unit. The whole machine is built by the building block combination of the minimum unit. Each signal generation module is independent of each other, and independent control and collaborative control can be realized through the designated background service module. At the same time, the interface of each signal generation module is unified, and the frequency point and parameters can be dynamically configured. When the signal changes, the device can adapt to these changes by loading the application software, complete the processing of the new signal without changing the hardware, and realize the online reconstruction function of the system frequency point level.

[0062] It is to be understood that the present invention is described by way of embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and embodiments that can fall within the scope of the claims of this application all fall within the scope protected by the present invention.

[0063] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A multi-channel GNSS navigation signal simulation system based on cloud architecture, characterized in that: include: Network communication module, integrated management module, several background service modules, simulation source module; Network communication module, used for network switching, allowing users in different network segments to use the simulation system simultaneously; The comprehensive management module is used to allocate user channel resources, build the corresponding relationship between each background service module and the user channel, and cooperate with the network communication module, background service module and simulation source module to complete the online reconstruction of system frequency points, network segment IP configuration, simulation scenario configuration and track injection; The backend service module is the information exchange medium between the integrated management module and the simulation source module. Each backend service module receives the output information of the integrated management module and sends it to the simulation source module according to the corresponding relationship between user channels, and forwards the reported information of the simulation source module to the integrated management module; The simulation source module takes the universal signal generating unit as the smallest unit. Each universal signal generating unit is combined on demand according to the user's generation frequency requirements. Each combination is controlled by the background service module corresponding to the user channel. The parameters obtained through online reconstruction of the system frequency, simulation scene configuration and track injection in the user channel are used to generate navigation simulation signals of multiple frequencies required by the corresponding user. Each universal signal generating unit is independent of each other, with a unified interface and dynamic parameter configuration.

2. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: The integrated management module is a cloud platform client, which is deployed on multiple local or remote computers in the simulation system and supports simultaneous access by multiple users.

3. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: Constructing the correspondence between each backend service module and the user channel, including: the comprehensive management module configures the backend service module into a corresponding user channel correspondence for a single user, a dual user or a multi-user; in a single-user test site, one backend service module corresponds to one user channel, in a dual-user test site, one backend service module corresponds to two user channels, and in a multi-user test site, one backend service module corresponds to the same number of user channels as the number of users.

4. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: The online reconstruction of the system frequency includes: the integrated management module independently and collaboratively controls the corresponding universal signal generation unit for users who need frequency reconstruction through the background service module corresponding to the user channel, and uses the background service module to inject the navigation satellite frequency signal waveform characteristic configuration parameters into the universal signal generation unit in standard format data online, and completes the online reconstruction of the signal frequency level by reconstructing parameters without changing the analog system hardware conditions.

5. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 4, characterized in that: The configuration parameters of the navigation satellite frequency signal waveform characteristics include: carrier frequency, code rate, information rate, symbol rate, modulation method and service type.

6. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: The network segment IP configuration includes: the integrated management module configures the network segment of each user channel and the port IP of the background service module, and through the network communication module and the background service module, users with different IPs in the same network segment or different network segments can individually control each user channel.

7. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 6, characterized in that: The port IP and communication protocol of each background service module are configured independently, and the port IP is different.

8. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: The simulation scene configuration includes: the integrated management module receives the user control instruction and configures the simulation scene corresponding to the user channel; each user channel can configure and store multiple simulation scene files, and the scene configuration of the corresponding channel is completed directly by calling the simulation scene file.

9. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: Orbit injection includes: the integrated management module receives user control instructions and injects the spacecraft orbit required by the user; the injection methods include: local injection and network injection. When local injection is used, the spacecraft orbit is calculated by inputting the six elements of the user's operating orbit and the starting point of the simulation time; when network injection is used, the spacecraft orbit is calculated and generated in real time according to the orbit point file in a fixed format.

10. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 1, characterized in that: Also includes: The branch control module, for each user channel, synthesizes the navigation analog signals of multiple frequency points input into one navigation analog signal, and then divides it into user signals and self-test signals. The user signal is provided to the user for parallel testing of each user terminal, and the self-test signal is provided to the self-test module for self-testing each user channel; The self-check module performs self-check using the self-check signal.

11. The multi-channel GNSS navigation signal simulation system based on cloud architecture according to claim 9, characterized in that: The user signals obtained by the branch control module include one high-power signal and one low-power signal. The signal power is determined by the user's needs. According to the attenuation of each user channel signal, the high-power signal or the low-power signal is selected to be transmitted to the user terminal. The self-test signal obtained by the branch control module enters the self-test module, and the self-test module includes: The closed-loop detection module selects the multi-channel self-test signals output by the branch control module, and supports single-channel, dual-channel or multi-channel self-test signal selection; The monitoring module receives the single-channel, two-channel or multi-channel self-test signals output by the closed-loop detection module and performs absolute positioning or differential positioning self-test.

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