Real-time Moving Horizon Estimation of Wheel Slip Angles and Lateral Tire Forces

Knowing the dynamic state of a vehicle is crucial for active safety systems such as electronic stability control (ESC) or torque vectoring. In addition, this knowledge is mandatory for fully automated vehicles such as autonomous cars. The main signals related to vehicle stability are the slip angles of the wheels, the longitudinal slips and the tire forces. In this contribution, a tracking approach for the vehicle's lateral tire forces per axle as well as the slip angle is presented, using Moving Horizon Estimation (MHE). This class of methods is based on the online solution of an optimal control problem (OCP), which is known to be challenging in real-time applications. This problem is tackled by using a recently published real-time capable and memory efficient optimization algorithm. The method only needs sensor information available in standard production vehicles. Furthermore, a model for the tire-ground contact is not required. The results are demonstrated in simulations with the software CarMaker.