1、Product composition
The composition of the product is shown in Figure 1
2、Basic principle
The inertial measurement unit consists of three accelerometers and three gyroscopes, which are responsible for measuring the acceleration and angular velocity of the carrier and sending this information to the information processing circuit. The information processing circuit uses the acceleration and angular velocity measured by the inertial measurement unit for navigation settlement, and also receives the satellite navigation information from the GNSS receiver as a reference for combined navigation, which corrects the navigation error of inertial navigation. The navigation information is output through the information interface circuit.
The basic principle is shown in Figure 2.
Figure 2 Schematic diagram of working principle
INSTRUCTIONS FOR USE
1、Form factor
The inertial measurement unit and GNSS receiver are integrated in the combined navigation system, and the system outline is shown in Figure 3.
The external dimensions of the combined navigation system are: 77.5mm×45 mm×27.2mm (L×W×H).
Figure 3 Combined navigation system
shape structure diagram
2、Electrical interface
2.1、Product interface
The system has three external connectors:
1.a power supply, communication interface (EEG.0T.312.CLN), whose contact sequence is defined as shown in Figure 4;
Figure 4 Combined navigation system power supply, communication interface point number (product socket, welding surface)
2.two RF line interface (SMA outer screw inner hole, where the logo P connects to the master antenna and the logo S connects to the slave antenna).
2.2、 Communication cable
One end of the communication cable is Remer connector (FGG.0T.312.CLAC40), which connects to the system, and the other end is divided into power cable and communication cable (line length is 1m):
1.Power cable: connected to 5~36V DC, working current not more than 0.2A when 24V power supply, external dump line, connected to red and black clips.
2.Communication cable: with 2 serial ports. Among them, COM1 is used to send working mode command and protocol output, which is RS232; COM2 is protocol output interface, which is RS422.
3. RF cables: one end is connected to the antenna and the other end is connected to the product, respectively.
The cable connector (FGG.0T.312.CLAC40) contact sequence is defined as shown in Figure 5, and the cable wiring is defined as shown in Table 2.
Figure 5 Cable connector point number distribution (plug, solder surface）
Table 2 Connector Point Definition
3、Using instructions
3.1、System workflow
The system has two working modes, combined navigation mode and inertial navigation mode. The combined navigation mode is the default working mode after start-up. The default working mode can be changed by command. If the setting is successful, it will return "cmd ok", otherwise it will show "cmd error". After inputting, type "saveconfig" to save this configuration, and the next reboot will automatically call this configuration, if you don't input this command, the next reboot will revert to the last saved configuration.
If you do not enter this command, the configuration will be restored to the last saved configuration after next reboot:
#moddgi
The command to set the inertial navigation mode as the default mode of operation is
#modins
3.1.1、 Combined navigation mode process
After entering the combined navigation process, the system automatically enters the coarse alignment state, and the coarse alignment time is 3s; waiting for the valid satellite navigation information in the coarse alignment state, the combined navigation system is required to be stationary during the coarse alignment; when the satellite navigation information is valid, it enters the combined navigation state, otherwise it keeps the coarse alignment state; when the system is in the combined navigation state, the combined navigation system can move.
3.1.2、Inertial navigation mode process
After entering the inertial navigation process, the system automatically enters the coarse alignment state, the coarse alignment time is 3s, waiting for valid satellite navigation information in the coarse alignment state, and the combined navigation system is required to be stationary during the coarse alignment; when the satellite navigation information is valid, it enters the fine alignment state, otherwise it automatically enters the fine alignment state after waiting for 1.5s; after 1500s of fine alignment, it automatically shifts to the inertial navigation state. When the system is in the fine alignment or inertial navigation state, the combined navigation system can move.
3.1.3 、System Reset
During operation, enter the "#reset" command to soft reset the system and redisplay the startup information.
3.2 、System configuration commands
3.2.1、 Configuration scheme and saving
The combined navigation system provides 2 serial ports to the outside world, and the allocation and related configuration of each serial port are shown in Table 3.
Table 3 Combined navigation system serial port function allocation table
After the system is powered on and the COM1 port displays the start-up prompt message, you can input commands such as COM1~COM2 serial port baud rate configuration, serial protocol and update rate setting, etc. Each command output will return "cmd ok" if successful, otherwise it will display "cmd error ". After inputting, type "saveconfig" to save the current configuration, and the next reboot will automatically call the current configuration, if you don't enter the command, the next reboot will restore the serial port configuration to the last saved configuration.
3.2.2、 Configuration Query
By typing "log loglist" or "log rxstatus" command through COM1 port, all configurations of COM1~COM2 will be listed, including the following aspects
1.Serial port number, serial port baud rate, serial protocol and update rate;
2.Function module open status: including zero speed correction status and smooth processing status, open for enable, close for disable;
3.Initial binding latitude and longitude;
4.Initial binding dual antenna heading and combined navigation system heading angle;
5.Initial binding antenna pole arm value;
6.System number and factory date;
7.Software version number: including pre-processing software version number and navigation software version number;
8.Operating mode: including combined navigation (DGI) and pure inertial navigation (INS).
3.2.3、 Baud Rate Configuration
Enter the following command in this mode to enter the serial port baud rate configuration:
com comX BAUDRATA
where X is 1~2 and BAUDRATA is the baud rate in bps.
For example, to set the baud rate of COM1 port to 115200bps, enter the following command:
com com1 115200
3.2.4. Protocol and update rate configuration
3.2.4.1, Protocol and update rate configuration
The output protocols of COM1~COM2 are configured through COM1 with the following configuration commands:
log comX LOG ontime updataTime
where comX can be com1~com2 configuration number; updataTime represents the update time, which can be 5(0.2Hz), 1(1Hz), 0.2(5Hz), 0.1(10Hz), 0.01(100Hz) and other periods that can be divided by 200Hz, unit s.
LOG indicates the protocol name, can be inspvasa, bdfpd, gpfpd, etc.
For example, to configure the COM2 port to output 10Hz bdfpd data, the following command can be entered through COM1:
log com2 bdfpd ontime 0.1
If you need to output 10Hz inspvasa data at COM2 at the same time, then you can enter the following command via COM1 again:
log com2 inspvasa ontime 0.1
If you want to turn off a protocol, configure the command as follows：
log comX LOG off
To configure the rawdata protocol for COM1~COM2 ports via COM1, the configuration command is as follows：
log comX rawdata onchanged
If you want to turn off the rawdata protocol for this serial port, configure the command as follows:
log comX rawdata off
If you want to disable all protocols on the serial port, configure the command as follows
unlogall comX
Note that increasing the update rate or outputting multiple protocols at the same time will increase the amount of data sent from the serial port. In general, the larger the amount of data, the higher the baud rate required.
3.2.4.2、 Protocol Formats
The output protocols supported by the product are shown in the following table.
Table 4 Description of output data protocols
The ASCII protocols all conform to the NMEA protocol format requirements and include the following fields: statement identifier, several data fields, check and end marks (with carriage return <CR> and line feed <LF>), separated by several commas. Take the bdfpd protocol as an example, the format is as follows:
$BDFPD,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*xx<CR><LF>
The following gives the gpfpd, bdfpd, bdfpdbl, inspvasa, bdfpdb, rawimusb protocol formats, as shown in the table below
Table 5 gpfpd format
Table 6 bdfpd format
Table 8 inspvasa format
3.2.4.3 、32-bit CRC Checksum Calculation Method
The 32-bit CRC checksum calculation method can be obtained by using the following C language functions
3.2.5、 Initial value configuration
The initial latitude and longitude are configured with the following configuration command
initialpos LONGITUDE LATILUDE
where LONGITUDE and LATITUDE are the configured local latitude and longitude values in degrees.
3.2.6、 Function Module Configuration
The function modules with open configuration mainly include zero speed correction and output position smoothing.
3.2.6.1 、"Zero speed correction" configuration
Zero speed correction function mainly refers to the combined navigation system to detect the sensitive information, if the combined navigation system is judged to be zero speed, then make the corresponding correction.
If the satellite information is invalid for a long time in the combined navigation state, and the user wants to get pure inertial navigation information, it is recommended to turn off the zero speed correction mode.
The zero speed correction configuration command is as follows:
inszupt switch
The switch value is disable or enable, where disable means turn off the function and enable means turn on the function.
3.2.6.2、 "Position output smoothing" configuration
In order to get smoother position information, the position output smoothing function is added to the navigation software, and the position noise after smoothing is smaller.
This product in the combination of navigation process "position output smoothing" default is off, in order to facilitate the user to choose, this function can be configured, configuration instructions are as follows:
possmooth switch
The switch value is disable or enable, where disable means turn off the function, enable means turn on the function.
3.2.7、 Carrier type configuration
According to the different carriers installed in the combined navigation system, the carrier type configuration is required. For different carrier types, different algorithms are processed inside the combined navigation system.
The configuration commands are as follows:
carrier vehicle/ship/air
In order, it is vehicle, ship and airborne.
After the configuration is finished, you need to enter the save command "saveconfig" and then hard start or enter the command "#reset", the carrier type configuration will be valid after the start. The combination navigation system does not support the current configuration during use, it must be restarted.
After the carrier type is configured as vehicle type, it is required that the combined navigation system is installed and fixed on the vehicle, and the combined navigation system heading is consistent with the direction of the front end of the carrier vehicle, with an error of not more than 10 degrees.
3.2.8、 GNSS antenna pole arm configuration
According to the relative installation relationship between the antenna and the combined navigation system, the antenna pole arm configuration is required. Configure the value of the pole arm between the combined navigation system to the antenna, the measurement must be accurate to millimeter (mm), especially when performing RTK operation, any pole arm measurement error will directly enter into the position error of the combined navigation system output, when installed and used, the combined navigation system as close as possible to the main antenna, especially in the horizontal position. This instruction is required before or during the static base alignment of the combined navigation system and before the dynamic base alignment. Once the configuration is complete, it needs to be saved via "saveconfig".
The configuration includes master antenna arm configuration and slave antenna arm configuration.
The master antenna configuration command is as follows:
setimutoantoffset armX armY armZ
The slave antenna configuration command is as follows
setimutoantoffset2 armX armY armZ
where armX, armY and armZ are the configured pole arm values in meters, representing the component of the vector from the combined navigation system to the antenna phase center within the combined navigation system carrier coordinate system, which is selected as right front up (XYZ). For the example in Figure 6, armX and armY should have negative values and armZ should have positive values.
Figure 6 Schematic diagram of the antenna pole arm
3.2.9、 Output lever arm settings
The default value of the product output lever arm configuration is [0, 0, 0] (upper right front), which means the position and speed values at the combined navigation system are output. If you need to output the position and speed of the user test point, you need to set the output lever arm according to the relative installation relationship between the test point and the combined navigation system.
The pole arm value between the configured combined navigation system and the test point must be measured to the nearest millimeter (mm), especially when performing RTK operations where any pole arm measurement error will go directly into the position error output from the combined navigation system. This command is required to be done before or during the static base alignment of the combined navigation system and before the dynamic base alignment. Once this configuration is complete, it needs to be saved via "saveconfig".
The output lever arm configuration command is as follows:
setimutosensoroffset armX armY armZ
where armX, armY and armZ are the configured arm values in meters, representing the vector from the combined navigation system to the test point in the combined navigation system vector coordinate system, which is selected as the right front up (XYZ). Figure 7 example, armY, armZ should be positive values.
Figure 7 Schematic diagram of output lever arm
3.2.10 、Mounting angle setting
The attitude and heading information output by the product are the Euler angles of the product coordinate system relative to the geographic coordinate system. The angular installation relationship between the product and the carrier coordinate system is the installation angle, and the configuration default value is [0, 0, 0] (pitch, heading, roll), which means that the product coordinate system is considered to overlap with the installation carrier coordinate system. If there is a mounting angle for the product installed on the carrier, and the product is required to output the Euler angle of the carrier coordinate system relative to the geographic coordinate system, the mounting angle should be set according to the relative mounting relationship between the product and the carrier.
The installation angle configuration command is as follows:
vehiclebodyrotation angleX angleZ angleY
where angleX, angleZ and angleY are the configured installation angle angle values in degrees, representing the angle from the carrier coordinate system to the combined navigation system coordinate system, in the order of pitch, heading and roll.
3.2.11、 Forced-to-inertial navigation
In the combined navigation system in the combined navigation state, it can receive the forced to inertial navigation command and turn into the inertial navigation state, in this state the combined navigation system still receives the satellite navigation information for protocol transmission, but does not use the satellite navigation information to participate in the combined navigation calculation. After receiving a valid forced inertial navigation command, the combined navigation system provides "cmd ok" feedback through COM1 port.
The forced-to-inertial navigation command is as follows:
#moddgitoins
3.3 、System Maintenance
3.3.1、 Firmware Upgrade
When a firmware upgrade is required follow the following operations:
1.Ensure that the COM1 port is the configuration interface before starting;
2.Connect the power cable and communication cable, connect the COM1 port to the computer, and set the COM1 port according to the COM1 port baud rate setting value;
3.Send the command "$GPUPD" to change the COM1 baud rate to 256000bps;
4.The interface of serial port tool shows the start-up prompt message, before the interface shows "100...10 9 8 7 6 5 4 3 2 1" to 1, send ":" (small colon, cancel the option of sending new line) to the serial port. interface displays the updata flash information;
5.Select the firmware to be upgraded (usually *.bin2 file) through the serial port tool and send it;
6.wait until the sending is finished, the program automatically reloads and starts, enters the boot prompt message and starts normally;
7.Firmware upgrade is completed.
3.3.2、 Parameter upload
In general, there is no need for the user to upload the calibration parameters, which are already configured before leaving the factory. In special cases, if the user is required to upload parameters for maintenance, the following steps should be followed:
1.After the system normally completes the start-up prompt message, the corresponding system number can be queried through "log bdlist"/"log rxstatus";
2.Send "#modbd" command to the combined navigation system through COM1 port, and upload "*.txt" calibration parameters through serial port after "cmd ok" is returned. file;
3.After the interface returns the calibration parameter information, send "#saveconfig"/"saveconfig" command to save the parameter, then reset the system softly and hardly, and it can work normally.
PRECAUTIONS
The main precautions are as follows:
1.The time interval between power-on and power-off of the combined navigation system is not less than 30s, otherwise it will easily cause damage to inertial devices;
2.During handling, installation and use, it should be handled gently to avoid bumping, dropping and impact;
3.The output and baud rate configuration of the satellite board card should be in accordance with the appendix description.
APPENDIX
1 、Differential configuration description
The combined navigation system can receive the differential correction information sent by the reference station through the communication link and work in the differential state to achieve the centimeter-level positioning accuracy. The differential configuration mainly includes 3 parts:
1) reference station setting;
2) communication link setting;
3) mobile station setting. The data link is shown in the figure below.
Figure 8 Schematic diagram of data link
1.1 、Reference station setting
Differential reference station is the satellite receiver antenna installed in a fixed position, the satellite receiver in the use of the process, need to ensure that the antenna position is fixed. The differential reference station sends the precise coordinates of the fixed position and the received satellite information to the mobile station (the point to be positioned) through the communication link, which is used for the mobile station to carry out differential positioning solution to realize differential high-precision positioning and achieve centimeter-level positioning accuracy.
The reference station can apply NovAtel-718D satellite receiver board and configure it as the reference station mode. The specific configuration instructions are as follows, and detailed descriptions are provided in the NovAtel-718D user manual.
Table 14 Base Station Configuration Instructions
No. Instruction Description
1 fix position 39.8122 116.1515 60.5 Set known precision coordinates (latitude 39.8122, longitude 116.1515, altitude 60.5) as the base station coordinate value
posave on 0.01 1.5 2.5 Receiver autonomous positioning 0.01h; or when the standard deviation of horizontal positioning <= 1.5m and altitude positioning <= 2.5m, use the average value of positioning as the reference station coordinate value
2 serialconfig com1 9600 Set the output baud rate of the reference station output interface COM1 to 9600bps
3 interfacemode com1 novatel rtcmv3 on Configure COM1 input data type as novatel, output data type as rtcmv3, and enable command feedback
4 log com1 rtcm1075 ontime 1 GPS differential message
5 log com1 rtcm1125 ontime 1 BDS differential message
6 log com1 rtcm1085 ontime 1 GLO differential message
7 log com1 rtcm1033 ontime 10 Receiver and Antenna Description
8 log com1 rtcm1005 ontime 10 RTK base station antenna reference point coordinates
9 saveconfig Save configuration
1.2 、Communication link setting
The communication link can use 4G DTU or digital radio, and the coverage area of 4G DTU is the coverage area of network information; the coverage area of digital radio is about 10km due to the national law, and the setting of 4G DTU and digital radio can refer to the user manual of corresponding products.
1.3、 Mobile station setting
The combined navigation system is a differential mobile station, which receives the differential correction information from the reference station in real time and receives satellite signals for differential positioning solution to achieve differential high-precision positioning. The combined navigation system supports RTCM and RTCMV3 standard data protocols. COM2 of the combined navigation system can be configured as the receiving interface of differential correction information, and the specific configuration commands are as follows.
Table 15 Mobile station configuration commands
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