This brief describes an observer-based state feedback tracking controller for vehicle dynamics with a four-wheel active steering system as well as an active suspension system. The objective of the proposed controller is to improve the vehicle behavior by forcing the lateral dynamics and the load transfer ratio to achieve the desired vehicle behavior in critical situations. A Takagi-Sugeno (TS) representation of the lateral forces has been used in order to take the nonlinearities into account. Based on the obtained fuzzy model, a TS observer has been designed with estimated membership functions in order to consider the unavailability of the sideslip and the roll angles for measurement. Based on the Lyapunov function and the H ∞ approach, the observer and controller design has been formulated in terms of Linear Matrix Inequality constraints. The proposed techniques have been evaluated through a fishhook test conducted in the CarSim professional software package.
This paper describes a methodology for estimating both vehicle dynamics and road geometry using a Fuzzy unknown input observer. Vehicle sideslip and roll parameters are estimated in presence of the road bank angle and the road curvature as unknown inputs. The unknown inputs are then estimated using the observer results. The used nonlinear model deduced from the vehicle lateral and roll dynamics with a vision system is represented by a Takagi-Sugeno (TS) fuzzy model in order to take into account the nonlinearities of the cornering forces. Taking into account the unmeasured variables, an unknown inputs (TS) observer is then designed on the basis of the measure of the roll rate, the steering angle and the lateral offset given by the distance between the road centerline and the vehicle axe at a look-ahead distance. Synthesis conditions of the proposed fuzzy observer are formulated in terms of Linear Matrix Inequalities (LMI) using Lyapunov method. Simulation results show good efficiency of the proposed method to estimate both vehicle dynamics and road geometry.
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