【作者】 李雄；

【导师】 喻凡；

【作者基本信息】 上海交通大学 ， 机械工程， 2018， 硕士

【摘要】 自动驾驶技术是目前汽车重要的发展方向之一,其发展进程中,线控(X-by-Wire)技术的发展由于易实现集成控制而日益受到重视。线控转向(Steer-by-Wire,SBW)系统主要特点在于去除了中间转向轴、直接采用电机实现转向控制和力矩反馈控制,因而具有结构紧凑、布置方案灵活且更易于实现集成控制的优点,有助于实现更高级别的自动驾驶,已成为自动驾驶汽车实现避障避险的关键技术之一。本文基于硬件在环试验对汽车线控转向系统进行了研究,主要内容包括以下几个部分。首先,在对相关文献综述分析的基础上,对SBW系统实验台架方案进行了分析和硬件选型。对电机布置方案进行了分类介绍,总结了四种常用的电机布置方案及其优缺点;针对SBW实验台架不能模拟轮胎实际回正力矩的情况,在对各类转向阻力施加方案对比和分析的基础上,选取了结构简单、且与实车匹配度较高的单电机前轮转向方案,同时也选取了可模拟不同工况、可大范围调节负载转矩的磁粉制动器负载模拟方案;针对所选方案,根据对标车型的相关数据进行了SBW系统方案设计和相关硬件选型。然后,针对所研究的SBW系统进行了控制系统设计。搭建了SBW系统动力学模型,同时采用Car Sim软件搭建了整车动力学模型运行环境,并进行了转向执行控制器和车辆稳定控制器设计;考虑到内模控制器稳定性和鲁棒性好的特点,设计了一个转向执行总成内模控制器,在Car Sim和Matlab/Simulink联合仿真环境下进行了正弦波扫频输入和侧翻转向驾驶员开环输入工况测试、以及双移线和避撞工况驾驶员闭环输入工况测试等。测试结果表明,所设计的底层转向系统控制器可很好地跟踪前轮转角;针对线控转向系统上层控制器,基于车辆稳定性的控制目标,进行了变传动比控制策略研究,分析比较了横摆角速度增益不变和侧向加速度增益不变的变传动比特性。考虑到滑模控制可自由设计滑动模态且物理实现简单的特点,设计了一个对车辆横摆角速度进行反馈的滑模控制器,以实现车辆线控主动转向的功能。在建立的Car Sim和Matlab/Simulink联合仿真环境下,对所设计的滑模控制器性能进行了联合仿真实验测试,结果表明,该滑模控制器可以很好地跟踪车辆理想横摆角速度,从而保证车辆行驶中良好的操纵稳定性。最后,基于搭建的d SPACE实时仿真平台进行了硬件在环试验,包括SBW系统各部件间通讯协议调试和转向执行总成硬件在环试验。试验测试结果表明,所搭建的SBW系统硬件在环试验台可正常实现线控转向功能,且SBW执行机构模块可很好的跟踪前轮转向命令。更多还原

【Abstract】 Nowadays,automatic driving has become one of the main development directions of automobile industry.In the further progress of automatic driving development,X-by-wire technology has been paid more and more attention.Steer-by-Wire(SBW)system removes the intermediate steering shaft in traditional steering system,and directly uses the electric motor to realize the “road sense”(i.e.driver feeling)feedback control and steering control,thus can be more beneficial due to its compact structure,flexible arrangement,and also easier to be integrated with other control sub-systems.Hence,SBW can help to achieve a higher level of automatic driving,thus it has become a key technology for path tracking and obstacle avoidance of automatic driving vehicle.The main contents of this dissertation are included as below.First,arrangement scheme for SBW steering motor is introduced and classified,and then the characteristics are compared for four commonlyused layout schemes.Since the SBW test bench cannot simulate the real aligning torque,different steering resistance simulating device schemes are classified and summarized.Accordingly,a single-motor front-wheel steering scheme is selected due to its simple structure and highly close to practical case.A magnetic particle brake(MPB)based scheme is selected to realize the function of simulating the steering aligning torque owing to its linear relationship between input current and output torque.According to selected benchmark vehicle model,a steering motor,a rack-pinion steering gear,a MPB and other related hardware devices are selected correspondingly.Secondly,modeling and analysis of the SBW system are carried out.The vehicle dynamics model and test driving conditions are respectively built and set by using Car Sim software.In this study,an internal mode controller(IMC)is chosen to realize steering control due to its stability and robustness.And for driver open-loop control tests,tests are performed in some typical conditions,including sine wave sweep test and roll-over steer test.Also double lane change test and collision avoidance test are designed and executed to accomplish the driver close-loop control test.The test results show that the designed steering system controller can track desired front wheel steering angle satisfactorily with very small tracking error.For upperlevel controller designed of the SBW system,and aiming to ensure optimal vehicle stability,a variable steering ratio controller is designed.Both cases respecting with constant yaw rate gain and constant lateral acceleration gain are analyzed.Due to the advantage of sliding mode surface being designed freely and convenience for physical implementation,this study designed a slide mode controller(SMC)in order to track desired vehicle yaw rate,by using the established Car Sim and Matlab/Simulink co-simulation platform,co-simulation tests are carried out,the results show that the designed sliding mode controller can track the desired vehicle yaw rate well for ensuring the vehicle handling stability.Finally,based on the d SPACE HIL real-time simulation platform,the communication protocol debugging between different modules of the SBW steering system and the steering actuator HIL tests are carried out.The HIL test results show that the steering motor can track the front wheel steering angle well.更多还原