GPS Estimation Algorithms for Precise Velocity, Slip and Race-Track Position Measurements

This paper investigates the use of carrier-phase differential GPS (CDGPS) for race car applications. In particular, experimental results are presented to demonstrate the use of CDGPS to accurately measure several key parameters of a test vehicle, including the inertial velocity, side-slip, and its precise location. This data is useful as a driver's coaching tool because it can be used to determine what the driver is doing and when, and also show precisely where these actions are being performed on the track. While CDGPS offers the potential of very precise position estimation, even a temporary blockage to the NAVSTAR constellation (e.g., by trees/bridges) means that the measurement biases must be re-acquired before a good solution can be obtained. Various solutions to this problem have been investigated, but each presents new difficulties and/or requires more expensive equipment. However, this paper demonstrates that tracking the GPS Doppler frequency information provides a precise measure of the vehicle velocity that can be integrated to obtain very precise position estimates without having to solve for the CDGPS biases. The approach does, however, require additional external infrastructure to initialize the velocity integration.