A self-contained position measurement system would consist, at least, of a lateral accelerometer, a longitudinal accelerometer and a yaw rate gyro. Additional control of the handling of the vehicle would require roll rate and perhaps even pitch rate. The measurement of these rates could be provided by gyros and accelerometers in a single package, using integrated technology - for example micromachine devices from Berkeley Sensor and Actuator (BSAC). We are constantly looking for inexpensive inertial measurement devices with specifications satisfying not only control but also navigational needs. The goal, then, is to specify the characteristics of state-of-the-art integrated devices promising high performance and low cost. The performance of individual and integrated sensors will have to be analyzed and improved. We plan to finish development of mathematical algorithms which will correct for sensor errors such as drift, misalignment and cross-axis sensitivity in a full scale inertial system. Software implementation of these mathematical models will be done in realtime DSP (SPOX) environment. This work will result in more accurate and less expensive control, maneuver, and navigation due to better use of sensor data.
An external position reference is essential to correct for
accumulated drift errors in inertial sensors.
We propose to consider several options:
-Differential GPS (global positioning system)
-Road-side beacons (radio, infra-red, or laser)
-Magnetic markers in the road (nails),
Note that road-side beacons could also serve as a Vehicle-to-
roadway communication system. Navigational information, which does not
exceed a few kilobites could be provided every few minutes, leaving
the remaining bandwidth free for other uses.
Most of the now popular GPS navigational systems are subject to numerous errors such as atmospheric delays, selective availability of satellites, clock differences, ephemeris error, multipath interference, receiver noise, and dilution of precision. It is possible to obtain precise position measurements from a GPS system only using advanced receiver configurations and extensive data processing. A combination of such advanced GPS technology with inertial sensors can offer six degree of freedom data with required precision and update rate. We propose to investigate integration of GPS into the AVCS navigational system.