California Partners for Advanced Transportation Technology

This project is concerned with accurately and reliably determining the state of a vehicle relative to a specified trajectory (e.g., a lane centerline). We are utilizing inertial navigation methods based on inexpensive solid state inertial sensors aided by external sensors such as carrier phase differential GPS, magnetometers, and roadway height. Due to this integration of sensors, reliability is increased relative to a single sensor approach and the changes required to the roadway infrastructure may be significantly decreased. This projects objectives included preparation for and participation in DEMO2002, research into INS aided GPS tracking of satellites, and research into methods to use auxiliary sensors (roadway height or magnetometers) to aid the integer resolution process. This project has been very interesting and successful. Although Demo2002 was ultimately cancelled our preparations for it were fruitful and we did participate in a smaller project demonstration with PATH at Crows Landing. In preparing for participation in Demo2002, we constructed much more robust prototypes of our GPS aided INS hardware. This include significant software re-writing that improved the reliability of the software. Overall, the hardware and software are now much more reliable and easier to use and install on test vehicles. In the area of INS aiding of a GPS receiver, research was performed and a new algorithm was design, but not implemented. We expect that this approach would lead to better satellite tracking during brief interruptions of the satellite signal. Implementation would require extensive interactions with the receiver design team, which is no longer possible due to changes in the GPS industry. In the area of aided integer ambiguity resolution, we have developed new algorithms to use information from non-GPS sensors to facilitate and speed-up the process of integer ambiguity resolution. This algorithm was evaluated in two experiments at UCR with significant improvements in the ability to correctly identify the integer ambiguities in a single epoch with fewer than 6 satellites. This algorithm was also used during the Crows Landing testing. Finally, UCR and PATH worked at PATH and Crows Landing and generated an impressive set of data as shown in Figures 12-25 of Section 4.2. This set of experiments was the culmination of the project. The experiments mounted the GPS/INS hardware on a bus that already was instrumented with the magnetometer hardware. We demonstrated that (1) the INS control state and magnetometer control state matched very well both when only the DCPGPS is aiding the INS and when both the magnetometer and DCPGPS are aiding the INS; (2) seamless transitions between magnetometer control, INS control, and manual control; (3) advanced maneuvers such as lane changes.