Research On Yaw Stability Of Multi-axle Direct Wheel Drive Articulated Bus

A multi-axle direct wheel driving articulated bus is a combination of an articulated bus and a wheel-driven system,which could be the solution of the problem of urban transport capacity and completely meet the future development trend of safety,environmental protection and energy conservation.In the field of dynamic research of distributed driving,domestic and foreign scholars have done a lot of work,but there are not many researches based on the four-wheel-driven articulated buses.Compared with the general electric vehicle,there are still many problems about articulation angle in the dynamic model construction,state estimation and yaw moment control.Based on this feature,this paper mainly focus on the yaw stability of multi-axle wheel driving articulated bus,and the main contents are stated as follows.1)Establish a dynamic model of 11 degrees of freedom in Simulink,and constitute a vehicle dynamics simulation platform with the dynamic model,empirical motor model,the hinge plate model,the tire model based on the magic formula,the transmission system model,the driver model and other subsystem models.This platform is designed for the multi-axle direct wheel driving articulated bus,which can be verified by the ASM platform and completely meet the research needs.2)Real-time acquisition of vehicle condition parameters is very important for vehicle stability control.The articulated angular velocity and yaw rate are as important as the side slip angle for multi-axle direct wheel driving articulated bus,but they are difficult to measure by sensors.In order to accurately obtain the vehicle condition parameters,after studying the different Kalman theory,we choose to estimate the important condition parameters such as the articulated angle of the bus based on the UKF,which lays a good foundation for the next dynamic control of front and rear carriages.The comparison between the estimated results and the output parameters of the vehicle model is carried out to verify the effectiveness of the UKF.The simulation results show that the accuracy and response time are within the acceptable range.3)In the research of the yaw stability control strategy of the articulated electric bus,the articulated angle occupies an important position in the driving stability of the articulated bus.In this paper,the control strategy is designed by using the hierarchical control structure.The upper motion tracking layer is based on the sliding mode control algorithm to track the target control variables,reduce the error and approach the expected value,which can be divided into yaw rate sliding mode control,yaw ratearticulated angle control and side slip angle-articulated angle control.The upper motion tracking layer carries out the generalized control quantity calculation,outputs the front and rear carriages additional yaw moment to the torque distribution layer,and the lower torque distribution layer distributes the torque to the drive wheel reasonably.After obtaining the additional driving torque of the four wheels,the bus can maintain the yaw stability.The simulation results verify the effectiveness of the three control algorithms.Through the comparison of the results,the effect of the two kinds of joint control is better than the yaw rate control,According to the proposed performance evaluation index C,the yaw stability is the best performance under yaw rate-articulated angle control.4)Through the verification of dSPACE-ASM simulation platform and HIL simulation,the effectiveness of the joint control is proved.The consistency and accuracy of wheel motor are verified by bench test,which makes the motor model more reliable.