Steering Dynamics Simulation And Stability Control Strategy Of Articulated Bus

As an important bus model of BRT system,articulated bus has attracted a mass of attention for its advantages such as large capacity and low operating costs.The articulated bus consists of main bus,sub-bus and articulated devices.Due to the complex structure,the speed of articulated bus has been very limited.In order to solve the problem of stability of articulated bus when driving at high speed,the stability control strategy of the articulated bus has been studyed with the direct yaw moment control method being used in this paper.In this paper,the potential lock-up problem of articulated bus when turning in steady-state was analyzed initially.Optimization model was designed based on this,with the angle between main bus and sub-bus as the objective function.The constraint equations of the optimization model included the geometric parameters of the main and auxiliary vehicle body and based on national standard of the limits of the width of the articulated bus turning channel.After optimization,the angle between main bus and vice bus was significantly reduced,and the turning ability of articulated bus had been improved.To obtain the transient response characteristics of articulated bus during high-speed turning,a 15-DOF vehicle model of articulated bus including the main vehicle model,deputy vehicle model and dumpling device model was established in this paper,and then simulated the motion response of the main and sub vehicles under the different speed of the articulated bus when the three steering wheel angles are input.Simulation results show that when the steering wheel angle is small,articulated bus has good steering performance at different speeds,while the steering wheel angle is large and the speed is high,articulated bus has potential of instability.In order to improve the steering capacity of articulated passenger bus when driving at high speed,the direct yaw moment control was applied,and the direct yaw moment is generated by the brake differential of the main and sub bus.Through theoretical analysis,the control target of the direct yaw moment is determined as the yaw velocity of main bus,side slip angle of main bus and sub-bus,and the ideal model was deduced based on it.Meanwhile,the PID controller was designed,which targets the side slip angle of the sub vehicle was zero,and PID controller and fuzzy controller are designed to make the yaw angular velocity and side slip angle of the main bus follow the ideal model.The control results show that when the sub-bus was controlled by PID control and the main bus was controlled by PID fuzzy joint control,the motion response quality of the articulated bus is the best.