【作者】 胡涛；

【导师】 邓亚东；

【作者基本信息】 武汉理工大学 ， 车辆工程， 2018， 硕士

【摘要】 轮毂电机电动汽车的四个车轮直接由轮毂电机驱动,运动状态相互独立,传动效率高,是电动汽车的理想驱动形式之一。本文以轮毂电机四轮驱动电动汽车的转向控制为着眼点,对转向过程中的车辆运动学和动力学进行分析,设计了一套转速、转矩协同控制的转向控制策略,并通过仿真计算验证了它的合理性与有效性。首先,对轮毂电机电动汽车的总体布置和电机进行了选型,确定了前轮采用齿轮齿条式的电动助力转向系统,后轮采用主动驱动力分配与转速协调的辅助差速系统。在对车辆的运动学和动力学进行分析的基础上,建立起稳态质心侧偏角下四轮转速的运动学约束关系以及车辆横摆、侧倾和侧向三自由度模型,对车辆的轮胎受力情况进行了分析,建立起Uni-Tire非线性轮胎模型。其次,在对比分析了永磁同步电机的结构与类型的基础上,对电机的数学模型和控制原理进行了分析,建立起了轮毂电机及其直接转矩控制模型,实现对电机的转速和转矩的双闭环控制,保证控制的精度和速度。然后,在综合比较现有转向控制方式的优缺点后,提出了转速、转矩协同控制的转向控制策略。其中,转速采用神经网络算法对车轮的目标转速进行实时的计算;转矩采用滑模算法对目标横摆角速度和目标滑移率进行跟踪,即转向稳定性控制和基于滑移率的转矩分配控制,分别用于调整车辆运动状态和消除轮速的波动,并界定了两者的工作范围。转向控制系统将确定的目标转速和转矩值输入电机模型,通过轮毂电机的输出使轮胎与地面相互作用来实现对车辆转向行驶的控制。最后,基于上述理论分析,建立起了轮毂电机电动汽车转向控制的Simulink模型,通过对三种不同工况的仿真计算,表明了控制系统能准确地根据车辆的输入对轮毂电机的转速和转矩进行实时的调整,保证了车辆转向行驶的侧向稳定性,证实了本文提出的转向控制系统的有效性,为今后的轮毂电机电动汽车转向控制的发展提供了一种可行的方案,有助于我国轮毂电机电动汽车的商业化发展和我国新能源汽车产业的进步。更多还原

【Abstract】 The four wheels of electric vehicle with in-wheel motors are directly driven by the four in-wheel motors respectively,of which the motion states are mutually independent.Therefore,it’s one of the most promising driving types for its high efficiency,and attracts wide concern of major countries,companies and institutes.Given that,this thesis is focused on the steering control of four in-wheel-motor driving vehicle,and the kinematics and dynamics of the designed vehicle during the steering are analyzed.The steering control strategy of coordination with speed and torque is proposed,and its effectiveness is validated through simulation test in Simulink platform.Firstly,the configuration of the four in-wheel-motor driving vehicle is determined by comparison of different driving types.The electric power steering based on rack and pinion is applied in the front steering operating mechanism,and the auxiliary differential system with coordination of speed and driving torque is adopted for the rear axle.Based on the designed vehicle,its kinematics and dynamics analysis are carried out.The constraint relations of the four wheels and in-wheel motors in kinematics with steady-state side-slip angle of the vehicle are derived,as well as the vehicle model with three degrees of freedom which includes yaw,roll and lateral vehicle motion.Given the fact that tire is the only mechanism that interact with the ground,the analysis of the four tires’ forces during the vehicle’s motion are carried out,and the non-linear mechanical model of tire is established with the Uni-Tire theory.Next,the permanent magnet synchrony motor is preferable motor type for the inwheel motor.Its mathematical model and control principle are described in order to establish the models of in-wheel motor and its Direct Torque Control method.As for the control algorithm of rotational speed and torque,PI controller is adopted to regulate the motor’s speed and hysteresis comparator is adopted to regulate the motor’s torque.Thus,the promptness and accuracy of speed’s and torque’s regulation can be assured.The influence of the motor’s dynamic characteristics may have on the vehicle during its steering can be simulated with certain accuracy.Then,based on comprehensive comparison of the existing steering control methods,a steering control strategy of coordination with speed and torque for four inwheel-motor driving vehicle is proposed.As for the motor and wheel’s rotational speed control,artificial neural network algorithm is adopted to obtain the target speed values of four wheels.As for the torque control,sliding mode control algorithm is adopted to regulate each motor’s output torques based on the vehicle’s target steady-state yaw velocity and wheel’s target slip ratio,between which the former one is enforced to realize the additional yaw-moment to regulate vehicle’s motion state,i.e.stability control,and the latter one is enforced to eliminate the fluctuation of the wheels’ target rotational speed,i.e.torque distribution control based on wheel’s slip ratio.When the stability control intervenes,the torque distribution control will quit to avoid the conflict.The target values of speeds and torques will then be input into the motors to respond and interact with the ground to realize the steering control of the vehicle.Finally,the Simulink models of four in-wheel-motor driving vehicle and its steering control strategy are established based on aforementioned theoretical analysis.The effectiveness of the control strategy is tested in three different driving conditions,and the results show that the rotational speeds and torques of in-wheel motors can be regulated quickly by the steering control systems to ensure the lateral stability of vehicle,which is beneficial to the handling stability.Therefore,the effectiveness of the presented steering control system is validated,which provides a feasible method for inwheel-motor driving vehicle’s steering control and will help promote the commercializing development of in-wheel-motor vehicles and the improvement of new energy automotive industry in China.更多还原