Note: ①Alignment is valid; ②On-board condition, need to be maneuvered; ③Double position alignment, the difference between the two position heading is greater than 90 degrees; ④Single-way output 200Hz; ⑤10s average.
WORKING PRINCIPLE
Product Composition
The composition of the product is as follows Figure 1.
Fundamentals
The inertial measurement unit consists of three accelerometers and three fiber optic 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 satellite navigation information from the satellite receiver as a reference for combined navigation, corrects the navigation error of the inertial guidance, and outputs the navigation information through the information interface unit.
The basic principle is shown in the following figure:
INSTRUCTIONS FOR USE
1 、Form factor
Inertial measurement unit and satellite receiver using integrated design scheme, are integrated within the inertial guidance system, the system shape as shown in the figure below.
System dimensions are: 176.8mm × 188.8mm × 117mm (L × W × H).
Figure 3 Outline structure diagram
2、 electrical interfaces
The system has 4 external connectors:
a) one X1 power supply port, X2 communication interface
b) two RF line interface (TNC outer screw inner hole, which is connected to the upper master antenna, the lower slave antenna)
c) 1 power cable connected to X1 at one end and 13~36V DC at the other end;
d) a communication cable one end to X2, the other end is divided into five serial ports, respectively COM2 ~ COM5, where COM5 for RS232, COM2, COM3, COM4 for RS232, RS422 can be configured. COM2 can be used to send work mode command, COM5 can be configured inertial guide internal GNSS board;
External connector points are defined as shown in Tables 1 and 2:
Table 1 X1 connector point definition
The inertial guidance system consists of two workflows, a combined navigation process and a pure inertial navigation process.
3.1.1、 Start-up prompt message
Connect the cable, power up the system, monitor the COM2 interface information through the serial debugging tool of the test computer, and send workflow instructions to the COM2 interface through the serial debugging tool after the interface displays "Please enter NaviMode within 20s! "#moddgi" is the instruction to enter the combined navigation work; if the instruction is not sent within 20s, the system will automatically enter the internal saved workflow after 20s.
3.1.2、 Combined navigation process
After entering the combined navigation process, the first binding satellite information, if the satellite is not positioned, it is in the state of waiting for satellite information; when the satellite information is valid, it will enter the alignment state, alignment time 1min, alignment period requires the inertial guide stationary, alignment is complete, the inertial guide can move, the system is in the combined navigation state.
3.1.3 、Pure inertial navigation process
After entering the pure inertial navigation process, the first 1min coarse alignment, if the satellite information is valid, the binding satellite information for 1500s fine alignment, if there is no satellite information, the static base must be aligned 1500s; alignment is completed after the transfer to the pure inertial navigation state, the inertial guide can move.
3.2、 System configuration commands
3.2.1 、Configuration scheme and save
Inertial guidance system provides four external serial ports (configuration number: com2~com5), and provides an internal storage channel (configuration number: file), each serial port function assignment and related configuration is as follows.
Table 1 inertial guidance system serial port function allocation table
"saveconfig" to save the configuration, the next reboot will automatically call this configuration, if you do not enter this 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" through COM2 port, all configurations of COM2~COM4 will be listed, including the following aspects
1.Serial port number, serial port baud rate, serial port protocol and update rate.
2.Function module open status: including zero speed correction status and smooth processing status, open for enable, close for disable; carrier type;
3.Internal storage status information: including the file name of the last file, remaining space, etc;
4.Initial binding latitude and longitude;
5.System number and factory date;
6.Software version number: including preprocessing software version number and navigation software version number;
7.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 2~4 and BAUDRATA is the baud rate in bps.
For example, to set the baud rate of COM2 port to 460800bps, enter the following command:
com com2 460800
3.2.4、 Serial RS232 Configuration
When configuring the serial port as RS232 (if configuring the serial port as COM3-COM4, you need to do an adapter cable, see section 4.2 Electrical Interface for wiring definitions), the command is as follows
rs232 COMX
where X is 2~4.
For example, to set COM3 port as RS232, enter the following command:
rs232 com3
3.2.5、 Serial port RS422 configuration
When configuring the serial port as RS422 (if the serial port is configured as COM2, you need to do an adapter cable, see section 4.2 Electrical Interface for wiring definitions), the command is as follows
rs422 COMX
where X is 2~4.
For example, to set the COM2 port to RS422, enter the following command
rs422 com2
3.2.6、 Update Rate Configuration
The configuration of COM2~COM5 and memory file port GPFPD, BDFPD, inspvasa, and inspvasb protocols is performed through COM2 with the following configuration commands:
log comX/file LOG ontime updataTime
where comX can be com2~com4 configuration number, file is the memory interface configuration number; updataTime represents the update time, which can be 5(0.2Hz), 1(1Hz), 0.2(5Hz), 0.1(10Hz), 0.01(20Hz) and other periods that can be 200Hz division, unit s.
LOG indicates the protocol name, can be inspvasa, inspvasb, gpfpd, bdfpd.
For example, to configure the COM2 port to output 10Hz GPFPD data, the following command can be entered via COM1:
log com2 gpfpd ontime 0.1
If you need to output 10Hz bdfpd data at COM2 at the same time, then you can enter the following command via COM1 again:
log com2 bdfpd ontime 0.1
For example, to store 1Hz inspvasa protocol data into the internal memory of the inertial guide, the following command can be entered via COM2 ：
log file inspvasa ontime 1
If you want to turn off a protocol, the configuration command is as follows:
log comX/file LOG off
To configure the rawimusb and rawdata protocols for the COM2~COM4 ports and the memory file port via COM2, the configuration command is as follows
log comX/file rawdata onchange
If you want to turn off the rawdata protocol for this serial port, configure the command as follows
log comX/file rawdata off
If you want to disable all protocols on the serial port, the command is as follows
unlogall comX/file
Note that increasing the update rate or outputting several 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.
3.2.7 、Initial value latitude and longitude 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.
3.2.8、 Function Module Configuration
The function modules with open configuration mainly include zero speed correction and output position smoothing.
3.2.8.1 、"Zero Speed Correction" Configuration
Zero speed correction function mainly refers to the inertial guide to detect the sensitive information, if the inertial guide 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.
3.2.8.2、 "Position output smoothing" configuration
The position information in INSPVASA and GPFPD protocol is inertial navigation position information, in order to get smoother position information, the navigation software has added the position output smoothing function, the position noise after smoothing is smaller.
In this product, "position output smoothing" is turned off by default in the combined navigation process, but for the convenience of the user, this function can be configured with the following commands:
possmooth SWITCH
The switch value is disable, enable, where disable means turn off the function, enable means turn on the function.
3.2.9、 Satellite serial port mapping configuration
If the satellite card does not have a spare serial port to configure or use during use, the satellite card serial port can be mapped to the external interface COM4, which is configured with two commands as follows:
connect gpscard com2
connect gpscard com3
connect gpscard disable
Sending connect gpscard com2 command will map COM2 of the satellite card 718D to the external connection COM4, at this time COM4 port must be configured to 230400 in order to configure the satellite navigation card board, this command will make the inertial guidance work in an abnormal state, after the configuration of the board you need to reboot the inertial guidance, in order to carry out the normal state of the inertial guidance, and the command reboot after the inertial guidance. The command will make the inertial guidance work in an abnormal state, and the inertial guidance will not be saved after the reboot.
Send connect gpscard com3 command to map COM3 of satellite card 718D to COM4 of external connection port, at this time, COM4 port baud rate must be configured to COM3 of 718D for normal communication, if you need to save, send saveconfig command.
Sending the connect gpscard disable command will restore the external COM4 serial port to the internal CPU output port.
3.2.10 、Carrier type configuration
According to the different carriers installed in the inertial guidance, the carrier type configuration is required, for different carrier types, the system internal processing of different algorithms.
The configuration commands are as follows:
carrier vehicle/ship/air
In order for the vehicle, ship and airborne.
After the configuration is complete, you need to enter the save command saveconfig, and then hard start or enter the #reset command, the carrier type configuration will be valid after the start. The inertial guide does not support the current configuration for current use during use, it must be restarted.
After the carrier type is configured as vehicle type, the inertial guide is required to be installed on the vehicle and fixed, and the inertial guide is oriented in the same direction as the front of the carrier vehicle, with an error of not more than 10 degrees.
3.2.11 、Online RTK
When using online RTK processing, com2 needs to input the following command.
possmooth disable
com5, the com1 port of the 718D, is configured as follows
serialconfig com1 9600 (variable baud rate, according to the actual DTU configuration)
interfacemode com1 rtcmv3 novatel on
saveconfig
3.2.12 、GNSS antenna pole arm configuration
According to the relative installation relationship between the antenna and the inertial guide, the antenna pole arm configuration is required. The value of the rod arm between the configured inertial guide to the antenna must be measured to the millimeter (mm), any rod arm measurement error will go directly into the position error of the inertial guide output, when installed and used, the inertial guide is as close as possible to the main antenna, especially in the horizontal position. This command is required before the inertial guide is aligned with the static base or in the middle and before the dynamic base is aligned. Once this configuration is complete, it needs to be saved via "saveconfig".
The configuration includes the master antenna arm configuration and the slave antenna arm configuration.
The master antenna configuration command is as follows:
setimutoantoffset1 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 vector from the inertial guide to the antenna phase center in the inertial guide carrier coordinate system, the inertial guide carrier coordinate system is selected as right front up (XYZ). For the example in Figure 5, armX and armY should have negative values and armZ should have positive values.
Figure 4 Schematic diagram of the antenna pole arm
3.2.13 Output lever arm setting
The default value of the product output lever arm configuration is [0, 0, 0] (right front up), which is the position and velocity value at the output inertial guide. If you need to output the position and velocity 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 inertial guide.
The bar arm value between the configured inertial guide and the test point must be measured to the nearest millimeter (mm) and any bar arm measurement error will go directly into the position error of the inertial guide output. This command is required before the inertial guide's static base is aligned or before the inertial guide's dynamic base is aligned. 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 inertial guide to the test point in the inertial guide vector coordinate system, the inertial guide vector coordinate system is selected as the right front up (XYZ). Figure 6 example, armY, armZ should be positive values.
Figure 5 Schematic diagram of output lever arm
3.2.14 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.
Note: This function will cause the output angular velocity, acceleration, attitude, etc. to change with the settings.
3.3 Protocol format
3.3.1、Example of inertial configuration command:
log com2 sncnavpvtb ontime 1
Table 6 sncnavpvtb format
3.3.2 GPFPD
Example of inertial configuration command:
log com2 gpfpd ontime 1
Example of inertial guidance output
$GPFPD,2083,199022.049,271.356,-2.149,0.767,39.7085178,116.1311212,39.93,-11.422,-0.077,0.050,1.500,27,0,1*59
Table 4 GPFPD format
3.3.3、BDFPD
Example of inertial configuration command:
log com2 gpfpd ontime 1
Example of inertial guidance output
$BDFPD,2105,355160.246,90.96184,-1.14427,1.01899,39.71066564,116.11209956,46.076,-0.0037,-0.0065,0.0147,20,16,0*68
Table 5 BDFPD format
3.3.5 、32-bit CRC checksum
The C code history is as follows
#define CRC32_POLYNOMIAL 0xEDB88320L
/* --------------------------------------------------------------------------
Calculate a CRC value to be used by CRC calculation functions.
-------------------------------------------------------------------------- */
unsigned long CRC32Value(int i)
{
int j;
unsigned long ulCRC;
ulCRC = i;
for ( j = 8 ; j > 0; j-- )
{
if ( ulCRC & 1 )
ulCRC = ( ulCRC >> 1 ) ^ CRC32_POLYNOMIAL;
else
ulCRC >>= 1;
}
return ulCRC;
}
/* --------------------------------------------------------------------------
Calculates the CRC-32 of a block of data all at once
ulCount - Number of bytes in the data block
ucBuffer - Data block
-------------------------------------------------------------------------- */
unsigned long CalculateBlockCRC32( unsigned long ulCount, unsigned char*ucBuffer )
{
unsigned long ulTemp1;
unsigned long ulTemp2;
unsigned long ulCRC = 0;
while ( ulCount-- != 0 )
{
ulTemp1 = ( ulCRC >> 8 ) & 0x00FFFFFFL;
ulTemp2 = CRC32Value( ((int) ulCRC ^ *ucBuffer++ ) & 0xFF );
ulCRC = ulTemp1 ^ ulTemp2;
}
return( ulCRC );
}
3.3.6、 INSPVAS
The command is short message protocol output
Example of inertial configuration command:
log com2 inspvasa ontime 1 (ASCII)
log com2 inspvasb ontime 1 (binary)
ASCII example
%INSPVASA,1264,144059.000;1264,144059.002135700,51.116680071,-114.037929194,515.286704183,277.896368884,84.915188605,-8.488207941. 0.759619515,-2.892414901,6.179554750,INS_ALIGNMENT_COMPLETE*855d6f76
INSPVAS format
log com2 rawimusb onchanged (binary)
RAWIMUS format
Figure 4 SSH software connection diagram
1.Click Connect, the SSH software will automatically pop up the "Enter Password" dialog box, no need to fill in the password, click OK to connect to the system;
2.Type /media/mmcblk0p1 in the address bar on the right side of the above figure and enter, then find the corresponding storage directory in the directory below to download.
3.After the download operation is completed, the system is powered off and the Ethernet interface is unplugged.
3.5、 System Maintenance
3.5.1 Firmware Upgrade
Operation steps are as follows:
1.Connect the inertial guide COM1 and network port to the computer, and set the computer network port IP port to 192.168.1.22;
2.open the host computer software CRT, open the corresponding serial port, serial port settings for baud rate 115200, 8-bit data, 1-bit stop bit, no parity bit;
3.power on the combined navigation system;
4.Observe the CRT display, wait for the Linux boot to complete, enter the command $GPEXT, a command line will appear.
5.Run SSH software (SSH Secure File Transfer Client), click Quick Connect and fill in the content as shown below.
1.Click Connect, the SSH software automatically pops up the "Enter Password" dialog box, no need to fill in the password, click OK, connect to the system;
2.Type /home/root/install in the address bar on the right side of the above figure and enter, delete the files snc300_dgi(linux application), snc300_dgi_dsp.out(DSP program), snc300imu.bin(FPGA program), and copy the new snc300_dgi, snc300_dgi_dsp.out, snc300imu.bin, snc300_dgi.bin and snc300imu.bin, snc300_dgi_dsp.out, snc300imu.bin files, you need to select change the three files in the right-click properties, change the permission to 777, and then enter the sync command in COM1 to synchronize the files.
3.If you need to upgrade the FPGA program, you need to send /home/root/update_fpga.sh from COM1, and wait for COM1 to indicate the successful upgrade.
4.The upgrade is completed when the product is rebooted.
CAUTIONS
The main considerations are as follows:
1.the inertial guidance system power-on and power-off time interval is not less than 30s, otherwise it is easy to cause damage to inertial devices;
2.in the handling, installation and use process, should be lightly held and placed to avoid bumping, dropping and impact;
3.after the inertial guide is turned on, you need to wait for the inertial guide to complete coarse alignment before linear motion, coarse alignment time of about 1min, otherwise affect the measurement accuracy;
4.carrier type configuration for the vehicle type, the inertial guide is required to be installed in the car fixed, and the inertial guide direction and the direction of the front of the carrier car, the error is not more than 10 degrees.
APPENDIX
1 、Combined navigation system satellite receiver COM2, COM3 output configuration
The combined navigation system receives satellite navigation information through the port of the built-in satellite receiver. The COM2 port of the satellite receiver is configured with the following commands:
unlogall com2
serialconfig com2 460800
log com2 headingb onchanged
DUALANTENNAALIGN enable 5 5
log com2 psrdopb ontime 1
log com2 bestposb ontime 0.2
log com2 bestvelb ontime 0.2
log com2 timeb ontime 1
log com2 rangecmpb ontime 1 (note: without raw number card, this command is invalid)
frequencyout enablesync 100000 1000000000
saveconfig
Which if you want to use the COM3 of the satellite card can refer to section 4.3.2.7, but you need to configure the following command to turn the satellite card multiplex pin into serial COM3.
interfacemode usb1 none none
interfacemode usb2 none none
interfacemode usb3 none none
MARKCONTROL MARK1 DISABLE
interfacemode com3 novatel novatel
serialconfig com3 115200 (Note: Baud rate can be set to the baud rate you want to use, but the inertial guide COM4 port needs to be consistent with the baud rate here)
Saveconfig
2、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 7 Schematic diagram of data link
2.1、 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 instructions are provided in the NovAtel-718D user manual.
Table 14 Base station configuration commands
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