Interior-point Method to Optimize Tire Force Allocation in 4-wheeled Vehicles Using High-level Sliding Mode Control with Adaptive Gain

Nonlinear vehicle control allocation is achieved by distributing the control task to tire forces with nonlinear saturation constraints. The overall vehicle control is accomplished by developing a hierarchical scheme. First, a high-level sliding mode control with adaptive gain is considered to obtain the body force/moment for stable vehicle motion. The proposed controller only requires online adaptation of control gains without acquiring the knowledge of upper-bounds on system uncertainties. Then, optimal distribution of tire forces (ODF) with nonlinear saturation constraints is considered. The high-level control objectives are mapped to individual tire forces by formulating a nonlinear optimization problem. The interior-point (IP) method is adopted for a nonlinear programming task at each time step. Evaluation of the overall system is accomplished by simulation testing with a nine-degrees-of-freedom vehicle nonlinear model. Comparison with a well-recognized control system shows the effect of saturation constrained ODF (SCODF) on improving vehicle handling and stability.