Disturbance-Observer-Based Hierarchical Control for Vehicle Front Steering: Interval Type-2 Fuzzy System Approach

This article addresses the composite hierarchical antidisturbance control issue for the front steering vehicle system with uncertain parameters. First, the front steering vehicle system is modeled as an interval type-2 Takagi–Sugeno (T–S) system, which contains the unknown disturbance matching the input channel and the norm bounded disturbance. Considering that the embedded membership functions of the interval type-2 fuzzy system are unknown, the definite part and the uncertain part of the interval type-2 T–S fuzzy system are separated to facilitate the subsequent analysis. Next, a novel disturbance observer design structure under the fuzzy framework is introduced. Through the novel design method, the expression of the unknown disturbance can be transformed into a new form containing only the uncertain parameter, and the estimation is realized by estimating the uncertain parameter. Then, a fuzzy integral sliding mode controller is adopted in combination with the disturbance estimation to ensure the stability of the composite system and the reachability of the specified fuzzy integral switching surface. Finally, simulation results of the front steering vehicle model that demonstrate the effectiveness of the proposed control scheme are provided.