Vehicle velocity and roll angle are important information for active safety control systems of four-wheel independent drive electric\nvehicle. In order to obtain robustness estimation of vehicle velocity and roll angle, a novel method is proposed based on vehicle\ndynamics and the measurement information provided by the sensors equipped in modern cars. The method is robust with respect\nto different road and friction conditions. Firstly, the dynamic characteristics of four-wheel independent drive electric vehicle\nare analyzed, and a four-degree-of-freedom nonlinear dynamic model of vehicle and a tire longitudinal dynamic equation are\nestablished. The relationship between the longitudinal and lateral friction forces is derived based on Dugoff tire model. The\nunknown input reconstruction technique of sliding mode observer is used to achieve longitudinal tire friction force estimation.\nA simple observer is designed for the estimation of the roll angle of the vehicle. And then using the relationship, the estimated\nlongitudinal friction forces and roll angle, a sliding mode observer for vehicle velocity estimation is provided, which does not need\nto know the tire-road friction coefficient and road angles. Finally, the proposed method is evaluated experimentally under a variety\nof maneuvers and road conditions.
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