GPS receiver
From CajunBot Wiki
The CNAV 2050 is a gps/starfire receiver from C&C technologies. It is capable of receiving both standard GPS signals, and more accurate subscription-based starfire correction signals, and RTK (Real time Kinematics) correction signals from an RTK base station.
 |  |
Contents |
[edit] CNAV 2050 Configuration for Autonomous Operation
Team cajunbot currently (Mar 10 2008) has 2 2050 receivers capable of receiving the above, as well as a subscription to starfire donated by C&C technologies. The subscription is usually for 6 months at a time, so when it expires a new one must be obtained from C&C.
For autonomous operation, the CNAV 2050 receiver, herein referred to as CNAV, is configured as a dynamic base station. This means that the CNAV uses the starfire signal to generate a position solution, then uses that solution to determine the error in the standard GPS signal. It then generated a signal to correct this error and transmits it using the RTCM protocol to the RT3102 Inertial Navigation System (RT3K). The RT3K then uses this correction signal to correct the error in its standard GPS solution calculations, resulting in a calculation that is roughly as accurate as the original starfire solution the CNAV generated. This indirect method of generating a solution in the RT3K is necessary since the RT3K cannot directly accept the starfire correction signal.
The following are the steps necessary to configure the CNAV to act as a dynamic base and output RTCM correction signals to the RT3K.
- Run the Starutil program. The latest version of this program can be located here under C-nav 2050 GPS Receiver.
- Click the connect icon, then select the com port you are using, the 19200 baud rate, and autobaud. Click OK to connect.
- Click on the "Rover" icon, then make the window that pops up look like this:
- Click the "Base" icon, then make the window that pops up look like this:
- Click the "ports" icon (looks like a DB9 plug with a cable), then make the window that pops up look like this:
The cable with the spiral cord should be connected to the CNAV port labelled COM1. The RT3K should connect to the female end of this cable.
The CNAV should now be configured for autonomous operation of Raginbot (aka CajunBot-II).
For configuration of the CNAV for Real Time Kinematic surveying using a base station, see CNAV 2050 Configuration for RTK Surveying with a Base Station.
[edit] CNAV 2050 Configuration for RTK Surveying with a Base Station
This page describes how to configure the cnav 2050 gps receiver to be used as a base station in an RTK setup. For more information about RTK surveying click here. We now use the CNAV 2050 GPS receiver as the base station, and the RT3K as the rover. The CNAV 2050 receiver is configured using a program called StarUtil. This program can be downloaded from here.
The following is a general outline of how an RTK survey is performed:
- The base station is set up in an area where there is a clear view of the sky. Its antenna is on a tripod, which should be fully extended and firmly placed on the ground.
- Keep cnav out of direct sunlight and in a cool place if possible, otherwise it might not function correctly.
- Connect the cnav to the antenna tripod. Then, connect port COM 1 to the radio using the curly cable. Also, plug a Dell into the COM 2 port using the serial port cable.
- Then plug in power cables from the cnav and the radio into the power outlet.
- Set the modem connection to COM 2 and allow the auto baud rate to run, until it says connected.
- The GPS receiver is powered on and left for 45 minutes to warm up. If this step is skipped, GPS accuracy will be degraded for the entire survey. You must ensure that the base station GPS' "rover" tab looks like this:
Of importance in the above image are the "Navigation Mode" entries. Only the "RTG Input" should be set to "use". The rest should be set to "ignore".
- After the receiver is warmed up, a self survey is performed. This entails:
- Opening the "Base" tab in Starutil
- Changing "Message Format" drop down box to "RTCM 20, 21, 22 (RTK)"
- Selecting the "Self Survey" radio button
- Clicking "Start Self Survey"
- At this point the base station receiver logs data. After one hour you should press "Stop self survey and apply position", at which point it averages all the collected data to get an accurate position of the base station.
NOTE: If the program crashes or somehow the cable unplugs, do not worry. Be sure before you plug in the cable you START the self survey so that it will not make the cnav restart the survey. After you start the survey you can then plug the cable back in and then click the "Stop self survey and apply position" button to apply the data the cnav collected.
- After the self survey position is applied, you must enable the 5B NCT message output. You can do this by clicking the Messages menu item, then clicking NCT output. Right click on an empty message name field and click on 5B. Click OK. This should enable the base station functionality, should cause the base light on the cnav receiver to flash green. If it is still flashing red, ummm...i don't know.
- Add me picture of ports tab.
- Add me information where to connect data radio.
- Now the base station receiver should be transmitting RTCM formatted corrections on its serial port, where a data radio should be connected.
- The corrections are transmitted to a matched radio in the rover (the jeep in this case)
- The rover receives the corrections from the base station, and uses them to correct its GPS solution to within about 2cm.
- The next step is configuring the RT3K to be an RTK rover. For instructions on how to do that see here: Add me
[edit] C-NAV 2050 Notes
- The C-NAV 2050 provides differential corrections to the RT3K INS.
- After taking the Raginbot (aka CajunBot-II) out to a location where it has a clear,
unobstructed view of the sky it may take as many as 15 minutes for the C-NAV to initialize fully.
- During normal operation the C-NAV indicator lights will behave as follows:
first all LEDS will illuminate briefly. The LINK LEDs should progress from a steady progressive blinking of each of the colors in turn, to all of the LEDs being steadily lit. The GPS LEDs should progress from blinking red, to red and yellow, to yellow, to yellow and green, and finally to green. The GPS LEDs will always blink.
- When first powered on all LEDs will illuminate for a period of 3-5 seconds
so that the operator can verify that they are operating properly
- The LINK LEDs indicate the quality of the StarFire signal. Repeating
flashing LEDs from red to amber to green indicate the unit is searching for a StarFire signal
- Eventually the LINK LEDs should come on continuously beginning with the
red. A continuous red LED indicates a weak StarFire signal. A read and yellow LED indicate and medium signal. All three LINK LEDs simultaneously illuminated indicate a strong signal.
- The BASE LEDs are not used on the C-NAV 2050
- The GPS LEDs indicate the status of the GPS satellite reception. These LEDs
will always blink at the rate at which the C-NAV is sending differential corrections to the RT. A red LED indicates no GPS satellites are being tracked. Simultaneous red and yellow LEDs indicate the unit is tracking satellites but a position is not yet available. A solitary yellow LED indicates a non-differential GPS fix has been acquired. Simultaneous green and yellow LEDs indicate code based differential positioning. Finally, a solitary green LED indicates dual frequency phase positioning.
[edit] Miscellaneous
Development of Precise GPS/INS/Wheel Speed Sensor/Yaw Rate Sensor Integrated Vehicular Positioning System
[edit] Raginbot (aka CajunBot-II) hardware links
- AEVIT
- Battery backup
- C-NAV antenna
- C-NAV receiver
- Comtrol box
- Digi Portserver TS8
- Ebox
- EMC console
- EMC control panel
- EMC steering engage lever
- Ibeo Alasca LIDAR
- Iteris LDW
- LabJack
- Logger, Steering, and NTP computers
- Eaton Vorad Radars
- CajunBot-II
- RT3102
- RT3K antenna
- RT3K wheel speed sensor
- Shore power box
- SICK LIDAR
- Torc E-stop
- Vision camera for detecting lanes
- Vision computer
- WiFi radios
