Abstract
Vehicle velocity and roll angle are important information for active safety control systems of four-wheel independent drive electric vehicle. In order to obtain robustness estimation of vehicle velocity and roll angle, a novel method is proposed based on vehicle dynamics and the measurement information provided by the sensors equipped in modern cars. The method is robust with respect to different road and friction conditions. Firstly, the dynamic characteristics of four-wheel independent drive electric vehicle are analyzed, and a four-degree-of-freedom nonlinear dynamic model of vehicle and a tire longitudinal dynamic equation are established. The relationship between the longitudinal and lateral friction forces is derived based on Dugoff tire model. The unknown input reconstruction technique of sliding mode observer is used to achieve longitudinal tire friction force estimation. A simple observer is designed for the estimation of the roll angle of the vehicle. And then using the relationship, the estimated longitudinal friction forces and roll angle, a sliding mode observer for vehicle velocity estimation is provided, which does not need to know the tire-road friction coefficient and road angles. Finally, the proposed method is evaluated experimentally under a variety of maneuvers and road conditions.
Highlights
Vehicle active safety control systems such as yaw stability control system and roll stability control system can significantly reduce the number of road accidents [1,2,3]
Since the wheel torques of four-wheel independent drive electric vehicle can be obtained the higher accuracy of vehicle velocity estimation compared to conventional vehicles can be achieved, which should be used to improve the performance of vehicle active safety control systems
In [13], the estimation of the road grade and bank angles is discussed based on vehicle longitudinal and lateral dynamics and the assumption that the angles vary slowly enough compared to the dynamics of the system; the effect of the roll angle has not been considered in this paper
Summary
Vehicle active safety control systems such as yaw stability control system and roll stability control system can significantly reduce the number of road accidents [1,2,3]. The yaw rate is measurable, but the vehicle velocity and roll angle cannot be measured directly in modern cars due to the cost and reliability issues As a consequence, they must be estimated, and the accurate and reliable vehicle velocity and roll angle information is very important for the vehicle active safety control systems [4, 5]. In this paper, using the measurements from the existing sensors equipped in the four-wheel independent drive electric vehicle, including the wheel angular velocities, longitudinal and lateral accelerations, yaw rate, roll rate, wheel steering angles, and wheel torques, a method for vehicle velocity and roll angle estimation with road and friction adaptation is proposed based on the nonlinear vehicle dynamics and Dugoff tire model. The proposed method is evaluated experimentally under a variety of maneuvers and road conditions
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