Integrating INS Sensors With GPS Measurements for Continuous Estimation of Vehicle Sideslip, Roll, and Tire Cornering Stiffness

This paper details a unique method for estimating key vehicle states-body sideslip angle, tire sideslip angle, and vehicle attitude-using Global Positioning System (GPS) measurements in conjunction with other sensors. A method is presented for integrating Inertial Navigation System sensors with GPS measurements to provide higher update rate estimates of the vehicle states. The influence of road side-slope and vehicle roll on estimating vehicle sideslip is investigated. A method using one GPS antenna that estimates accelerometer errors occurring from vehicle roll and sensor drift is first developed. A second method is then presented utilizing a two-antenna GPS system to provide direct measurements of vehicle roll and heading, resulting in improved sideslip estimation. Additionally, it is shown that the tire sideslip estimates can be used to estimate the tire cornering stiffnesses. The experimental results for the GPS-based sideslip angle measurement and cornering stiffness estimates compare favorably to theoretical predictions, suggesting that this technique has merit for future implementation in vehicle safety systems

1. Introduction

MANY VEHICLE control systems, such as antilock braking (ABS), stability control, and vehicle lateral control schemes, require vehicle sideslip as critical component of the control logic [1]–[3]. Unfortunately, this value is not typically available without the presence of expensive speed-over-ground sensors. To compensate for the lack of a direct measurement, the common practice on production systems is to integrate inertial sensors in order to obtain slip angle estimates [2]–[5]. However, this integration is prone to drift and can be corrupted by road bank angle and vehicle roll [6], forcing many production algorithms to intervene based on changes in slip angle rate instead of slip angle. Although in some cases, nonlinear observers can estimate the slip angle from yaw rate measurements [7], the slip angle cannot be observed using yaw rate and steer angle as the vehicle approaches neutral steer characteristics. Other methods for estimating vehicle sideslip angle from dynamic and kinematic models [8] or by switching between model estimation and accelerometer integration based on judgments of vehicle spinout or bank angle [9] require accurate knowledge of uncertain tire parameters. This fundamental lack of a sideslip angle measurement, coupled with uncertainty in the parameters needed for model-based estimation, places severe constraints on stability control algorithms and other potential vehicle dynamics control [3].