【作者】 王强；

【导师】 王耘； 宋小文； 胡树根；

【作者基本信息】 浙江大学 ， 车辆工程， 2011， 硕士

【摘要】 随着能源危机的不断加深和环境污染的日益严重,传统内燃机汽车的发展受到了越来越大的阻力,人们开始纷纷把目光投向新能源汽车——电动汽车的开发。其中,基于轮边驱动的电动汽车由于其结构布置简单,传动效率高,并且各驱动轮都能独立控制,在提高整车操纵稳定性和安全性方面存在较大的潜力而备受关注。然而,轮边驱动电动汽车在具备更多控制自由度的同时,也产生了各驱动轮之间协调控制的问题,即通常所说的电子差速问题。为了解决上述问题,首先建立了包含纵向、侧向、横摆、侧倾及车轮转动的八自由度整车模型,以及基于“魔术公式”适用于纵滑和侧偏联合工况的非线性轮胎模型,作为电子差速控制系统的开发平台。其次,设计了车辆关键状态参数估算及路面特征参数辨识模块,首次了提出基于二次函数拟合法和线性插值法相结合的路面特征参数辨识方法,对提高车辆在各种路面上的适应性起到了很大的作用。然后,针对目前仅仅单纯依靠驱动轮转速或转矩控制实现电子差速所存在的不足,结合当今车辆主动安全控制技术和集成控制技术的发展趋势,开发了基于横摆力矩和变滑转率联合控制的电子差速控制系统,其主要由三大功能模块组成：(1)横摆运动控制模块,该模块通过监测车辆横摆角速度与理想值的偏差,利用鲁棒性较好的滑模变结构控制算法对车辆所要施加的横摆控制力矩进行计算,从而从整车层面上对车辆的行驶姿态进行控制；(2)差动驱动控制模块,该模块根据总的驱动力矩输出及需要对车辆施加的横摆控制力矩,同时考虑驱动轮的物理限制,对左右驱动轮输出力矩进行合理分配,实现差动驱动；(3)变滑转率控制模块,该模块在路面条件无法满足总的驱动力矩输出需求时,通过对驱动轮滑转率的控制来实现对总的驱动力矩输出的控制,保证驱动轮工作在稳定区域,同时,采用变滑转率的控制方式取代传统的将滑转率控制在最佳滑转率处的定滑转率控制方式,从而提高了驱动轮在极限工况下的侧向稳定性,进一步改善了车辆的操纵稳定性。为了验证设计开发的电子差速控制系统的有效性,在Matlab/Simulink软件中建立了包括整车、轮胎、参数估算辨识及电子差速控制系统的仿真模型,设计了包括低附着路面加速起步、对接路面、对开路面及高速操纵稳定性多种试验工况。仿真试验结果表明,与传统机械差速器相比,所开发的电子差速控制系统简单有效,通过对车辆横摆力矩和变滑转率的联合控制,不仅能够很好的实现电子差速功能,而且还可以进一步提高车辆的操纵稳定性和安全性。更多还原

【Abstract】 With the emergence of energy crisis and environmental pollution, the development of the traditional internal combustion engine vehicles face more and more resistance, and the new energy vehicle-electric vehicle (EV) has been paid more and more attention to. Because of the simple structural layout, high efficient transmission, each wheel can be controlled independently, and has large potential in improving vehicle handling and safety, the electric vehicle based on in-wheel motor draw more and more attention. However, while the electric vehicle based on in-wheel motor has more freedoms can be controlled, the problem that harmonizing the drive wheels also occurred, namely electronic differential (ED) problem.In order to solve the problem mentioned above, firstly, established an 8 DOF vehicle model which contains longitudinal, lateral, yaw, roll and wheel rotate motions, and also a non-linear tire model based on "magical formula", as the platform for electronic differential control system design and development. Secondly, design of the key state parameters of the vehicle and road identification parameters estimation module, proposed an new method for road identification parameters estimation based on quadratic function fitting and linear interpolation combined, which plays a significant role in improving the adaptability of vehicle on various roads. Thirdly, in the view of existing situation that relies solely on the driving wheel speed or torque control to realize the electronic differential is shortage, with the development trend of present active safety technology, developed the electronic differential control system based on yaw moment and variable slip rate joint control, which contains three main module:(1) Yaw motion control module, this module calculates the deviation of yaw rate between real model and ideal model, and uses the sliding mode variable structure control to output the yaw moment value that need to be acted on the vehicle, in order to improve the vehicle’s handling; (2) Differential drive control module, this module distributes the driving torque according to the total driving torque and the yaw moment, considering the limitations of the driving wheel; (3) Variable slip rate control module, this module controls the total driving torque by control the driving wheels’ slip rate when the road’s condition can not satisfy the total driving torque output, in order to guarantee the driving wheel working in stable area, meanwhile, uses variable slip rate control method to replace the traditional fix slip rate control method, in order to ameliorate the driving wheels’lateral stability in extreme conditions and improve the vehicle’s handling.In order to verify the effectiveness of the electronic differential control system, the vehicle, the tire, the estimation module and the control system simulation model were built in the Matlab/Simulink software, and the tests combined of acceleration in low adhesion road, butt road, bisectional road and high speed handling were carried out. The simulation results showed that, compared with conventional mechanical differential, the electronic differential control system was simple and effective. Through yaw moment and variable slip rate joint control, the electric vehicle can not only realize the differential function, but also improve the vehicle’s handling and safety.更多还原