GNSS module with integrated communication and navigation and GNSS channel expansion method

Abstract

The embodiment of the present invention discloses a communication and navigation integrated GNSS module and a GNSS channel expansion method, wherein the module includes an ARM main control, a power divider, an antenna and a plurality of GNSS chips, wherein the plurality of GNSS chips are connected to the antenna through the power divider, the ARM main control is connected to the plurality of GNSS chips, and each GNSS chip sends a PPS pulse signal to the ARM main control; the ARM main control controls each GNSS chip to search for satellite data of different galaxies respectively; one of the GNSS chips is selected as a PPS reference, and the PPS of the GNSS chip used as the reference is synchronized to the remaining GNSS chips to complete the time synchronization of the plurality of GNSS chips; the ARM main control fuses the collected plurality of original observation data into one original observation, and outputs standard NMEA data. The present invention uses a plurality of GNSS chips with a low number of channels to simultaneously capture different satellite systems, realizes observation value synchronization through the time synchronization of the plurality of GNSS chips, and then realizes the expansion of the number of channels, while greatly reducing the cost.

Description

Technical Field

[0001] The present invention relates to the field of satellite positioning technology, and in particular to a communication and navigation integrated GNSS module and a GNSS channel expansion method. Background Art

[0002] The integration of communication and navigation positioning technology is an important national space-time infrastructure and a major demand for strategic development. With the development of communication networks and the popularization of smart terminals, more and more location services have entered the lives of the public. Due to the increasing demand for refined management, the requirements for positioning accuracy are also getting higher and higher. The previous positioning accuracy of about 10 meters is difficult to meet the current usage scenarios. Sub-meter, centimeter, and millimeter-level high-precision positioning products are increasingly used. This requires us to improve the stability of chips or modules and increase the number of search satellites and signal quality.

[0003] Currently, there are no chips or module products on the market that support mobile cellular networks, inertial navigation, dual-frequency, and more than 100 channels at the same time. Moreover, GNSS modules with more than 100 channels are expensive and have few options, which greatly limits the terminal products. Products that support mobile cellular communications and dual-frequency Beidou high-precision positioning require at least two modules to implement, which has a complex structure and increases the communication cost and development difficulty of development. Due to the complexity of the high-precision positioning technology algorithm, it will consume most of the development energy and time, and the positioning accuracy in different scenarios varies greatly, which prolongs the project development cycle. Summary of the invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a communication and navigation integrated GNSS module and a GNSS channel expansion method to achieve channel expansion while reducing costs.

[0005] In order to solve the above technical problems, an embodiment of the present invention proposes a communication and navigation integrated GNSS module, including an ARM main control, a power divider, an antenna and multiple GNSS chips, wherein the multiple GNSS chips are connected to the antenna via the power divider, the ARM main control is connected to the multiple GNSS chips, and each GNSS chip sends a PPS pulse signal to the ARM main control;

[0006] The ARM master controls each GNSS chip to search for satellite data from different galaxies respectively; selects one of the GNSS chips as the PPS benchmark, synchronizes the PPS of the benchmark GNSS chip to the remaining GNSS chips, and completes the time synchronization of multiple GNSS chips; the ARM master collects the original observations of each GNSS chip at the same time, merges the collected multiple original observation data into one original observation, and calculates and outputs standard NMEA data based on the merged original observation.

[0007] Furthermore, after the PPS benchmark is selected, if the GNSS chip serving as the PPS benchmark is positioned normally or all GNSS chips fail to be positioned, the ARM master control keeps the PPS benchmark unchanged; if the GNSS chip serving as the PPS benchmark is not positioned, and there is a GNSS chip that is positioned normally among the remaining GNSS chips, the ARM master control selects the GNSS chip with the best positioning condition as the new PPS benchmark.

[0008] Furthermore, the ARM master ensures the synchronization of the observation values ​​of each GNSS chip according to the following steps:

[0009] 1. When a GNSS chip that is not used as the PPS reference receives a new PPS signal, the preset PPS interrupt service function is triggered;

[0010] 2. The PPS interrupt service function is started, assuming that this is the i+1th PPS interrupt;

[0011] 3. Calculate the GNSS time corresponding to the current PPS, recorded as The calculation formula is:

[0012]

[0013] Among them, n is the time interval between two PPSs. GNSS time corresponding to the last PPS;

[0014] The ARM master updates after parsing the new reference time information

[0015] 4. Read the current GNSS chip time and record it as Calculate the deviation d between the current time and the reference time of the GNSS chip t i+1 :

[0016]

[0017] Among them, t delav It is the preset data delay estimation, the delay includes PPS inherent deviation and data transmission delay;

[0018] 5. Compensate for the time deviation of the GNSS chip and update the GNSS time of the GNSS chip itself. The ARM master controller extracts the observation value according to the updated GNSS time to ensure the synchronization of the observation values ​​of each GNSS chip.

[0019] Accordingly, an embodiment of the present invention further provides a GNSS channel expansion method, comprising:

[0020] Step 1: Set the firmware of each GNSS chip to control each GNSS chip to search for satellite data of different galaxies respectively;

[0021] Step 2: Select one of the GNSS chips as the PPS reference;

[0022] Step 3: Synchronize the PPS of the benchmark GNSS chip to the remaining GNSS chips to complete the time synchronization of multiple GNSS chips;

[0023] Step 4: Collect the raw observations of each GNSS chip at the same time, fuse the collected multiple raw observation data into one raw observation, and calculate and output standard NMEA data based on the fused raw observations.

[0024] Furthermore, after the PPS benchmark is selected, if the GNSS chip serving as the PPS benchmark is positioned normally or all GNSS chips fail to be positioned, the PPS benchmark remains unchanged; if the GNSS chip serving as the PPS benchmark is not positioned, and there are GNSS chips that are positioned normally among the remaining GNSS chips, the GNSS chip with the best positioning condition is used as the new PPS benchmark.

[0025] Further, step 3 includes:

[0026] Sub-step 3.1: When a GNSS chip in the GNSS chip that is not used as the PPS reference receives a new PPS signal, a preset PPS interrupt service function is triggered;

[0027] Sub-step 3.2, the PPS interrupt service function is started, assuming that this is the i+1th PPS interrupt;

[0028] Sub-step 3.3: Calculate the GNSS time corresponding to the current PPS, recorded as The calculation formula is:

[0029]

[0030] Among them, n is the time interval between two PPSs. GNSS time corresponding to the last PPS;

[0031] The ARM master updates after parsing the new reference time information

[0032] Sub-step 3.4: Read the current GNSS chip time, recorded as Calculate the deviation d between the current time and the reference time of the GNSS chip t i+1 :

[0033]

[0034] Among them, t delav It is the preset data delay estimation, the delay includes PPS inherent deviation and data transmission delay;

[0035] Sub-step 3.5: Compensate for the GNSS chip time deviation and update the GNSS time of the GNSS chip itself. The ARM main control extracts the observation value according to the updated GNSS time, thereby ensuring the synchronization of the observation values ​​of each GNSS chip.

[0036] The beneficial effects of the present invention are as follows: the present invention uses multiple GNSS chips with a low number of channels to simultaneously capture different satellite systems, and achieves observation value synchronization through time synchronization of the multiple GNSS chips, thereby achieving expansion of the number of channels, while greatly reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the structure of a communication and navigation integrated GNSS module according to an embodiment of the present invention.

[0038] Figure 2 2 is a schematic diagram of time synchronization according to an embodiment of the present invention.

[0039] Figure 3 It is a flowchart of a GNSS channel expansion method according to an embodiment of the present invention.

[0040] Figure 4 It is a schematic diagram of the test effect of Example 1 of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention is further described in detail below in conjunction with the drawings and specific embodiments.

[0042] Please refer to Figure 1 The communication and navigation integrated GNSS module of the embodiment of the present invention includes an ARM main control, a power divider, an antenna and multiple GNSS chips.

[0043] Multiple GNSS chips are connected to antennas through power dividers. The ARM main control is connected to multiple GNSS chips through SPI and / or UART interfaces. Each GNSS chip sends a PPS pulse signal to the ARM main control. After generating a PPS pulse signal, the GNSS chip sends the time information corresponding to the pulse signal to the ARM main control through the data interface. Multiple GNSS chips use different firmware algorithms to expand the number of communication channels, and achieve full galaxy search at a lower cost.

[0044] The ARM master controls each GNSS chip to search for satellite data of different galaxies. One of the GNSS chips is selected as the PPS benchmark. After receiving the latest positioning results of multiple GNSS chips, if the PPS benchmark is selected for the first time, the master selects the GNSS chip with the best positioning status as the PPS benchmark. After receiving the latest positioning results of multiple GNSS chips, if the PPS benchmark has been selected and the GNSS chip of the original PPS benchmark is positioned normally or all GNSS chips fail to be positioned, the PPS benchmark remains unchanged; if the GNSS chip used as the PPS benchmark is not positioned, and there are chips with normal positioning among the remaining GNSS chips, the GNSS chip with the best positioning status is selected as the new PPS benchmark. The PPS of the GNSS chip used as the benchmark is synchronized to the remaining GNSS chips to complete the time synchronization of multiple GNSS chips; the ARM master collects the original observations of each GNSS chip at the same time, merges the collected multiple original observation data into one original observation, and calculates and outputs standard NMEA data based on the merged original observation. The ARM master synchronizes the PPS of the benchmark GNSS chip to the remaining three GNSS chips. The GNSS chip can read the current time at any time.

[0045] As an implementation method, please refer to Figure 2 After the PPS benchmark is selected, if the GNSS chip used as the PPS benchmark is positioned normally or all GNSS chips fail to be positioned, the ARM master control will keep the PPS benchmark unchanged; if the GNSS chip used as the PPS benchmark is not positioned, and there is a GNSS chip that is positioned normally among the remaining GNSS chips, the ARM master control will select the GNSS chip with the best positioning status as the new PPS benchmark.

[0046] As an implementation method, the ARM master ensures the synchronization of observation values ​​of each GNSS chip according to the following steps:

[0047] i. When a GNSS chip that is not used as the PPS reference receives a new PPS signal, a preset PPS interrupt service function is triggered.

[0048] 2. The PPS interrupt service function is started, assuming that this is the i+1th PPS interrupt.

[0049] 3. Calculate the GNSS time corresponding to the current PPS, recorded as Because the PPS signal is earlier than the GNSS reference time data corresponding to the PPS signal sent by the master, it can only be calculated based on the time of the previous PPS. The calculation formula is:

[0050]

[0051] Among them, n is the time interval between the two PPSs (PPS is the GNSS chip connected to ARM through a hardware interface, usually sending out a pulse signal in 1 second. The time corresponding to PPS is the time when the chip sends out the pulse signal. The pulse signal is transmitted to the ARM main control, and the ARM main control triggers an interrupt, which then calls the software's PPS interrupt service function for processing. There is a delay from the moment the GNSS chip sends out the pulse signal to the moment the ARM main control processes the PPS interrupt service function. PPS itself may also have a delay, that is, the moment when the GNSS chip marker chip sends out the pulse signal is usually inaccurate, and there will be an inherent delay.) GNSS time corresponding to the last PPS.

[0052] The ARM master updates after parsing the new reference time information (After the GNSS chip generates the PPS pulse signal, it will send the time information corresponding to the pulse signal to the ARM through the data interface, which will be slower than the PPS. Therefore, when the ARM processes the PPS interrupt, there is no time information yet, only the PPS time information of the previous moment.) When the ARM master processes the PPS interrupt, because the current PPS time information has not arrived yet, it can only estimate the current PPS time based on the PPS time information of the previous moment.

[0053] 4. Read the current GNSS chip time and record it as Calculate the deviation dt between the current time and the reference time of the GNSS chip i+1 :

[0054]

[0055] Among them, t delav It is the preset data delay estimation, and the delay includes PPS inherent deviation and data transmission delay.

[0056] 5. Compensate for the time deviation of the GNSS chip and update the GNSS time of the GNSS chip itself. The ARM master controller extracts the observation value according to the updated GNSS time to ensure the synchronization of the observation values ​​of each GNSS chip.

[0057] As an implementation mode, the integrated GNSS module of an embodiment of the present invention preferably includes an IMU, and the IMU is connected to one of the GNSS chips. The GNSS chip completes the data synchronization of the IMU and outputs it to the ARM main control to complete the INS solution, thereby realizing the function of inertial navigation and still being able to output position information in the absence of a GNSS signal. The main data acquisition of the ARM main control is realized by multiple GNSS chips. Through the power divider, each GNSS chip can obtain the same satellite signal data at the same time. Through the firmware algorithm (the firmware of each GNSS chip is different, and the searched galaxies and frequencies are locked; for example, chip 1 is fixed to search Beidou, chip 2 searches GPS, chip 3 searches GLONASS / GALILEO, chip 4 searches Beidou / QZSS, etc., and fine-tuning will be done according to the area used), each GNSS chip can search for satellite data of different galaxies. Each GNSS chip only outputs the original observation quantity to the ARM main control (algorithm SDK). The SDK is integrated in the ARM chip of CAT1. According to the algorithm, it merges multiple original observation quantities into one, and outputs the fused original observation quantity and NMEA data, which can be expanded to 160 satellite channels, which can basically meet the search for satellite data of the entire galaxy and full frequency band, ensuring the positioning accuracy of the original data.

[0058] INS (Inertial Navigation System) assists GNSS positioning technology. In some environments, such as tunnels, viaducts, underground garages, etc., the module cannot receive GNSS signals and cannot achieve GNSS positioning. However, if GNSS positioning has been done before, INS can use IMU data to complete positioning. When the GNSS signal is received again, the positioning result of INS can be used to eliminate satellites with large pseudorange errors and improve the positioning accuracy of GNSS initial positioning.

[0059] As an implementation method, the ARM main control adopts a CAT1 chip with 4G function, which is highly integrated with GNSS technology. It can realize 4G CAT1 network transmission, support AT commands, and implement some GNSS algorithms on the CAT1 chip, so that secondary developers can develop projects in the same way as other CAT1 modules. They do not need to worry too much about the implementation process of high-precision GNSS. High-precision positioning data can be obtained through AT commands, which reduces costs and facilitates project development.

[0060] SDK is implanted in the CAT1 chip part. After the NTRIP algorithm, differential data can be injected into the SDK to achieve RTK. In open areas, the dual-frequency RTK algorithm can achieve centimeter-level positioning. At the same time, the CAT1 network part is responsible for providing an AT interface to the outside world. AT commands can be used for network communication and hardware operations, and the OPENCPU mode can also be realized.

[0061] The integrated communication and navigation GNSS module of the embodiment of the present invention supports the reception of dual-frequency GNSS signals and supports the RTK algorithm. Through the NTRIP service built into the module, the user can implement the RTK service through one instruction; and the GNSS chip performs the time synchronization work of the IMU and supports the inertial navigation algorithm, and can be applied to products related to vehicle-mounted projects.

[0062] The integrated GNSS module of the embodiment of the present invention supports the output of high-quality raw observation quantities, and can achieve millimeter-level positioning in combination with post-processing algorithms. It can be applied to deformation monitoring, slope monitoring, bridge monitoring and other projects to effectively prevent natural disasters.

[0063] Please refer to Figure 3 , the GNSS channel expansion method of an embodiment of the present invention includes:

[0064] Step 1: Set the firmware of each GNSS chip to control each GNSS chip to search for satellite data of different galaxies respectively;

[0065] Step 2: Select one of the GNSS chips as the PPS reference;

[0066] Step 3: Synchronize the PPS of the benchmark GNSS chip to the remaining GNSS chips to complete the time synchronization of multiple GNSS chips;

[0067] Step 4: Collect the raw observations of each GNSS chip at the same time, fuse the collected multiple raw observation data into one raw observation, and calculate and output standard NMEA data based on the fused raw observations.

[0068] As an implementation method, please refer to Figure 2 After the PPS benchmark is selected, if the GNSS chip used as the PPS benchmark is positioned normally or all GNSS chips fail to be positioned, the PPS benchmark remains unchanged; if the GNSS chip used as the PPS benchmark is not positioned, and there are GNSS chips that are positioned normally among the remaining GNSS chips, the GNSS chip with the best positioning condition will be used as the new PPS benchmark.

[0069] As an implementation method, step 3 includes:

[0070] Sub-step 3.1: When a GNSS chip in the GNSS chip that is not used as the PPS reference receives a new PPS signal, a preset PPS interrupt service function is triggered;

[0071] Sub-step 3.2, the PPS interrupt service function is started, assuming that this is the i+1th PPS interrupt;

[0072] Sub-step 3.3: Calculate the GNSS time corresponding to the current PPS, recorded as The calculation formula is:

[0073]

[0074] Among them, n is the time interval between two PPSs. GNSS time corresponding to the last PPS;

[0075] The ARM master updates after parsing the new reference time information

[0076] Sub-step 3.4: Read the current GNSS chip time, recorded as Calculate the deviation dt between the current time and the reference time of the GNSS chip i+1 :

[0077]

[0078] Among them, t delav It is the preset data delay estimation, the delay includes PPS inherent deviation and data transmission delay;

[0079] Sub-step 3.5: Compensate for the GNSS chip time deviation and update the GNSS time of the GNSS chip itself. The ARM main control extracts the observation value according to the updated GNSS time, thereby ensuring the synchronization of the observation values ​​of each GNSS chip.

[0080] Example 1: The following is an example of 4 GNSS chips. For example, the GNSS chip can use the dual-frequency GNSS chip independently developed by the company. Due to cost reasons, it only supports 40 channels, that is, it can only support the simultaneous search of 40 satellite information; on the basis of compatibility with 4G network use, using low-cost 40-channel chips, through the GNSS channel expansion method of the embodiment of the present invention, the 4 chips are expanded into a module with 160 channels, and its positioning accuracy is comparable to the high-precision products of the same level on the market, but the cost is greatly reduced.

[0081] The PPS (Pulse Per Second, used for time synchronization) input and output of the four GNSS chips are connected to the ARM master control. The ARM master control selects the PPS input of one of the chips as the master control according to the preset algorithm rules, and synchronizes it to the other three GNSS chips to complete the time synchronization of multiple GNSS chips, thereby ensuring that the observations of each GNSS chip are extracted at the same time.

[0082] The ARM master assists the GNSS chip in capturing satellites. Since the satellite systems and frequencies received by the four GNSS chips are different, the difficulty of capturing different satellite systems and frequencies varies in different environments. In some cases, satellites from some GNSS chips are more difficult to capture, while satellites from other GNSS chips may be easier to capture. The ARM master can use the captured satellites for positioning, and feed back the time and position to the GNSS chip that has not captured the satellite, to assist it in searching and capturing the satellite.

[0083] Under the same signal quality, the more satellite signals found, the higher the positioning accuracy. The GNSS chip used in the present invention is a dual-frequency positioning chip, and its signal quality ranks high in the industry. Due to price reasons, the number of channels is limited. In the present invention, the satellite signal is connected to 4 GNSS chips through a power divider. The firmware of each GNSS chip is different, and the searched galaxies and frequencies are locked. For example, chip 1 is fixed to search Beidou, chip 2 searches GPS, chip 3 searches GLONASS / GALILEO, chip 4 searches Beidou / QZSS, etc., and fine-tuning will be done according to the region used.

[0084] When the SDK receives data from different galaxies and different frequencies from four GNSS chips, after time synchronization, it merges the four original observation data into one original observation data, and outputs standard NMEA sentences through calculation, which can satisfy the expansion of four different 40-channel data into one 160-channel data, and basically can search for the number of visible satellites in the entire galaxy and at all frequencies. The algorithms of PVT, RTK, and INS are extracted from the chip and implemented on the external SDK.

[0085] Test results such as Figure 4 ,from Figure 4 It can be clearly seen that the 160-channel module has better positioning point convergence effect and smaller positioning error.

[0086] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A GNSS module integrating communication and navigation, characterized in that: It includes an ARM main control, a power divider, an antenna and multiple GNSS chips. The multiple GNSS chips are connected to the antenna through the power divider. The ARM main control is connected to the multiple GNSS chips. Each GNSS chip sends a PPS pulse signal to the ARM main control. The ARM master controls each GNSS chip to search for satellite data in different galaxies; Select one of the GNSS chips as the PPS reference, synchronize the PPS of the reference GNSS chip to the remaining GNSS chips, and complete the time synchronization of multiple GNSS chips; The ARM master collects the original observations of each GNSS chip at the same time, fuses the collected multiple original observation data into one original observation, and calculates and outputs standard NMEA data based on the fused original observations; The ARM master ensures the synchronization of observation values ​​of each GNSS chip according to the following steps: (1) When a GNSS chip that is not used as the PPS reference receives a new PPS signal, the preset PPS interrupt service function is triggered; (2) PPS interrupt service function starts, assuming this is the first PPS interruption; (3) Calculate the GNSS time corresponding to the current PPS, recorded as , the calculation formula is: ； Among them, n is the time interval between two PPSs. GNSS time corresponding to the last PPS; The ARM master updates after parsing the new reference time information ; (4) Read the current GNSS chip time, recorded as , calculate the deviation between the current time and the reference time of the GNSS chip : ； in, It is the preset data delay estimation, the delay includes PPS inherent deviation and data transmission delay; (5) Compensate for the time deviation of the GNSS chip and update the GNSS time of the GNSS chip itself. The ARM master controller extracts the observation value according to the updated GNSS time, thereby ensuring the synchronization of the observation values ​​of each GNSS chip.

2. The integrated communication and navigation GNSS module according to claim 1, characterized in that: After the PPS reference is selected, if the GNSS chip used as the PPS reference is positioned normally or all GNSS chips fail to position, the ARM master control keeps the PPS reference unchanged; If the GNSS chip used as the PPS reference is not positioned, and there is a GNSS chip with normal positioning among the remaining GNSS chips, the ARM master controller uses the GNSS chip with the best positioning status as the new PPS reference.

3. A GNSS channel expansion method, characterized in that: include: Step 1: Set the firmware of each GNSS chip to control each GNSS chip to search for satellite data of different galaxies respectively; Step 2: Select one of the GNSS chips as the PPS reference; Step 3: Synchronize the PPS of the benchmark GNSS chip to the remaining GNSS chips to complete the time synchronization of multiple GNSS chips; Step 4: Collect the original observations of each GNSS chip at the same time, fuse the collected multiple original observation data into one original observation, and calculate and output standard NMEA data based on the fused original observations; Step 3 includes: Sub-step 3.1: When a GNSS chip in the GNSS chip that is not used as the PPS reference receives a new PPS signal, a preset PPS interrupt service function is triggered; Sub-step 3.2, PPS interrupt service function starts, assuming this is the first PPS interruption; Sub-step 3.3: Calculate the GNSS time corresponding to the current PPS, recorded as , the calculation formula is: ； Among them, n is the time interval between two PPSs. GNSS time corresponding to the last PPS; The ARM master updates after parsing the new reference time information ; Sub-step 3.4: Read the current GNSS chip time, recorded as , calculate the deviation between the current time and the reference time of the GNSS chip : ； in, It is the preset data delay estimation, the delay includes PPS inherent deviation and data transmission delay; Sub-step 3.5: Compensate for the GNSS chip time deviation and update the GNSS time of the GNSS chip itself. The ARM main control extracts the observation value according to the updated GNSS time, thereby ensuring the synchronization of the observation values ​​of each GNSS chip.

4. The GNSS channel expansion method according to claim 3, characterized in that: In step 2, after the PPS reference is selected, if the GNSS chip used as the PPS reference is positioned normally or all GNSS chips fail to be positioned, the PPS reference remains unchanged; If the GNSS chip used as the PPS reference is not positioned, and there is a GNSS chip that is normally positioned among the remaining GNSS chips, the GNSS chip with the best positioning condition will be used as the new PPS reference.

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