Sliding mode observers for the estimation of vehicle parameters, forces and states of the center of gravity

In this paper, sliding mode (SM) observers are proposed to replace expensive sensors used for the measurement of tires forces, vehicle side slip angle and vehicle velocity. These estimations are done for two important purposes: The first is for the estimation of the forces and parameters needed for vehicle control, while the second is for the diagnosis preview based on the safety region for each parameter and state. For that purpose, the model of the vehicle is divided in two parts, in the first, the dynamical equations of the wheels are used to estimate their longitudinal forces and angular velocities. The estimations of the longitudinal forces are realized using a second order SM observer based on a super-twisting algorithm. In the second part, the estimated longitudinal forces are injected in the reduced state space equations representing the vehicle, which are the equations of side slip angle, yaw rate and the velocity of the vehicle. Estimations in this part are based on the principles of the classical SM observer. In this part the observability of the model is studied. The model takes as input the yaw rate and estimates the side slip angle and the velocity. Validation with the simulator VE-DYNA, at each step, pointed out the good performance and the robustness of the proposed observers.