In this paper, a sliding mode observer for estimating vehicle slip angle and tire forces is developed.
Firstly, the sliding mode observer design approach is presented. A system damping is included in the sliding mode observer to speed the observer convergence and to decrease the observer chattering.
Secondly, the sliding mode observer for vehicle states is developed based on a 7 DOF embedded vehicle model with a nonlinear tire model ‘UniTire’. In addition, since the tire lateral stiffness is sensitive to the vertical load, the load transfers are considered in the embedded model with a set of algebraic equations.
Finally, a simulation evaluation of the proposed sliding mode observer is conducted on a validated 14 DOF vehicle model. The simulation results show the model outputs closely match the estimations by the proposed sliding mode observer.