Research On Adjustable Road Feeling For Steering-by-wire System Based On Identification Of Driver Behavior

Steering-By-Wire(SBW)system is one of the core chassis components of intelligent driving,which realizes modular structure and system parameters are adjustable and can freely design vehicle dynamics control system that conforms to the driver's characteristics.However,due to the removal of mechanical connection between steering wheel module and the front wheel module,road feeling couldn't be transmitted to drivers directly,so the driver's steering feeling and vehicle safety will be affected.Therefore,it is necessary to simulate the road feeling.Because of the individual differences and state fluctuations of drivers,it is also difficult to guarantee the needs of the single road feeling feedback mode to different drivers.In view of the above problems,this paper relies on the National Natural Science Fund project "Research on the Control Mechanism and Evaluation Method of New Type SBW System Based on Driver's Characteristics"(No.51575223).The steering gains of different drivers are determined based on the steering behavior characteristics.By adjusting the parameters and steering gains of the feedback torque mode,an adjustable road feeling feedback control strategy is designed to meet the individual needs of the driver which can not only generate the road feeling feedback similar to the traditional steering system,but also realize the adaptability of SBW system to the driver's characteristics,and give full play to the performance advantages of the steering system.The main works are as follows:(1)Modeling SBW system dynamics and designing road feeling control strategyFirstly,the paper analyses the mechanism of road feeling generation,so the dynamic models of steering wheel module and front wheel module are established,and an objective evaluation method of road feeling characteristics is designed.Secondly,the feedback torque model of road feeling of SBW system is divided into two parts: the main torque and theadjusting torque.The adjusting torque is used to compensates and regulates the main torque.(2)Parameter determination and model validation of road feeling control strategyThe adjusting parameters of the feedback torque model are determined and the output torque of the road feeling motor is effectively controlled,so that the actual output torque of the motor can accurately follow the target torque.The simulation results show that by changing the parameters of the model,the feedback torque of road feeling can be adjusted well with good road feeling performance.At the same time,the influence of the adjusting parameters on the road feeling evaluation index is analyzed.(3)Identification of driver's steering behaviorDrivers have different demands for road feelings,so the data reflecting driver characteristics are obtained through the steering test for on-center handing based on driving simulator.The returnability,the on-center steering feeling and the maximum steering wheel torque are extracted as the characteristic parameters of road feeling.Fuzzy C-means algorithm is used for clustering analysis.Identification model of driver's characteristics are established by using BP neural network.It provides the basis for designing feedback torque algorithm of road feeling which accords with the driver's characteristics.(4)Design and validation of the adjustable road feeling feedback control strategyThe steering gain is determined according to the difference of road feeling characteristics between different types of drivers.Then,the adjusting torque can be adjusted based on the steering gain so that an adjustable road feeling feedback strategy is designed to meet the driver's characteristics.The hardware-in-the-loop test was carried out under different steering conditions.The results show that SBW system based on this method can realize the matching of driver steering control process and the road feeling not only conforms to the driver's characteristics,but also meets the different needs of the same driver.