【作者】 魏建伟；

【导师】 魏民祥；

【作者基本信息】 南京航空航天大学 ， 车辆工程， 2012， 博士

【摘要】 转向系统作为人－车交互界面，是汽车的关键子系统之一，直接影响汽车的操纵稳定性、舒适性和行驶主动安全性。在现有电动助力转向（Electric Power Steering，EPS）系统的基础上，研究主动转向的实现机构、控制机理和路感，既可以充分发挥电动助力转向的助力性能，又可以通过主动转向控制，改善EPS系统在稳定性控制方面的不足，提高汽车行驶的主动安全性，获得良好的转向特性，具有重要的理论意义和工程应用价值。具体研究内容如下：（1）综述了不同动力转向系统实现主动转向功能的研究现状，然后对主动转向控制关键技术、汽车横摆角速度和质心侧偏角估计，以及EPS系统转向路感的研究现状进行了阐述，提出了现有国内外研究存在的问题及解决思路。（2）提出了一种融合主动转向功能的EPS系统的机电结构，建立了转向系统与整车机电耦合的数学模型。通过双排行星轮系动力学分析，以及转向系统的转向路感、转向灵敏度和稳定性分析，从理论上解决了是否需要改变扭矩传感器的安装位置或增加额外扭矩传感器的问题。并从路面信息反馈的角度，分析了主动转向执行机构的机电参数以及主动转向干预对转向路感的影响，为研究主动转向干预时EPS系统的转向路感问题打下了基础。（3）建立了无主动转向干预时EPS系统的动力学模型，推导出了转向阻力矩到扭矩传感器输出的传递函数，定性分析了助力比对转向路感的影响。根据EPS系统的频率分布，选取了两个加权函数，并针对两种加权函数作用的情况，基于H∞控制算法和线性矩阵不等式（LinearMatrix Inequality，LMI）方法设计了不同的反馈控制器，分析了不同加权策略对转向路感的影响。仿真结果表明，两个加权函数共同作用可以保证驾驶员获得满意的转向路感。（4）采用固定转向增益策略，并鉴于特征车速对汽车行驶稳定性的影响，以及转向盘转角对操纵性的要求，提出了变传动比控制规律的两种控制方案。为验证所提出的变传动比控制规律的控制方案，建立了人－车－路闭环系统，并基于线性矩阵不等式方法，设计了无刷直流电机（Brushless DC Motor，BLDCM）的角位移跟踪鲁棒PID控制器。进行了单移线道路仿真，并从转向盘转角和路径跟踪两方面性能，对增强稳定性变传动比控制规律方案一和方案二进行了对比分析，结果表明变传动比控制规律方案二的整体性能优于方案一。（5）提出了主动转向变传动比控制和横摆角速度控制的协调策略，并在变传动比控制的基础上进行了横摆角速度控制的研究。基于线性二次型调节器（Linear Quadratic Regulator，LQR）最优控制理论，进行了横摆角速度控制器的设计。极限工况下的仿真验证了所提出的主动转向变传动比控制和横摆角速度控制的协调策略，以及横摆角速度控制器的有效性。（6）针对主动转向改变了转向系统角位移传递特性的同时也改变了转向盘转角与汽车行驶状态之间的内在对应关系这一问题，提出了将横摆角速度和质心侧偏角看作是转向小齿轮转角和侧向加速度非线性映射的研究方案。基于自适应模糊神经推理系统（Adaptive Neuro-FuzzyInference System，ANFIS），研究了横摆角速度和质心侧偏角的估计算法。为验证基于ANFIS算法进行横摆角速度和质心侧偏角估计的精度和泛化能力，进行了仿真数据验证和实车试验数据验证，并与基于径向基函数（Radial Basis Function，RBF）神经网络的横摆角速度和质心侧偏角的估计结果进行了对比分析。研究结果表明，所提出的研究方案是有效的，且基于ANFIS算法进行横摆角速度和质心侧偏角的估计具有更好的泛化能力。（7）针对主动转向干预时转向盘力矩发生突变的问题，提出了两种不再受传统EPS系统助力车速范围外常规助力增益取值为零的限制，且能够在主动转向施加附加转角干预时，实现全车速范围内EPS系统助力电机的前馈助力修正控制方案。同时，借鉴阶跃响应瞬态特性的评价方法，提出了助力修正方案的两个评价指标，并对两种前馈助力修正方案进行了量化对比分析。结果表明，基于扭矩传感器输出修正方案的修正控制效果优于基于整车模型修正方案，具有更好的车速适应性。（8）基于虚拟试验技术，利用UG软件的CAD模块，构建了融合主动转向功能的EPS系统的三维模型；利用UG软件的CAE模块进行了转向系统的运动学和动力学分析，验证了所提出的EPS系统的力矩和角位移传递特性，以及助力修正控制方案的有效性；利用CarSim软件进行了极限工况虚拟道路试验，验证了变传动比控制和横摆角速度控制的协调策略，以及所设计的横摆角速度控制器的有效性。更多还原

【Abstract】 As a driver-vehicle interface, steering system is a key subsystem of vehicle, which directlyinfluences vehicle handing stability, comfort and driving active stability. On the base of existingElectric Power Steering (EPS) system, researches on the realization, control mechanism, and steeringfeeling of active steering not only can give full play to assist performance of EPS, but also canimprove the deficiency of stability control of EPS system by active steering control. Then, goodsteering characteristics can be obtained and driving active stability can be improved. Thus, thesestudies have important theoretical significance and engineering value. The detail research works arelisted as follows:(1) At the beginning of the dissertation, a review of different power steering systems integratedwith active steering was presented. Recent developments of key technologies for active steeringcontrol, estimation algorithms of vehicle yaw rate and side slip angle, as well as steering feeling ofEPS system were described. Problems of existing research at home and abroad were found out, andsolutions were put forward to solve these problems.(2) An electro-mechanical structure of EPS system integrated with active steering was proposed,and mathematical model of electro-mechanical coupling for steering system and vehicle was built.According to the dynamic analysis of double planetary gear train, as well as performance analysis ofthe steering system such as steering feeling, steering sensitivity, and stability, the problem whetherneed to change installation position of torque sensor or add an additional torque sensor was solved intheory. From the view of the road information feedback, steering feeling affected by theelectro-mechanical parameters of active steering actuator, and the interference conducted by activesteering were analyzed. A basis for the study of steering feeling for the EPS system with theinterference of active steering was provided.(3) Dynamic model for EPS system with no interference of active steering was built, and transferfunction from steering resistant torque to the output of torque sensor was derived. Furthermore, theeffect of assist ratio on steering feeling was qualitatively analyzed. According to the frequencycharacteristic of EPS system, two weighting functions were chosen. Based on H∞control arithmeticand Linear Matrix Inequality (LMI) approach, different feedback controllers were designed with theeffect of two types of combination for weighting functions, and the effects of different weightingstrategies on steering feeling were analyzed. Simuliation results indicate that perfect steering feelling can be obtained by interaction of the two weighting functions.(4) In view of the effects of character speed on vehicle stability, and demand of steering wheelangle for maneuverability, two control programs of varied steering ratio were proposed to keepsteering gain constant. To investigate the different control programs of varied steering ratio,driver-vehicle-road closed-loop system was built. Based on Linear Matrix Inequality approach, arobust PID controller of angular position tracking was designed for Brushless DC Motor (BLDCM).Then, simulation testes of single lane change maneuver were carried out, comparative analyses of thetwo control programs of varied steering ratio were conducted in two aspects, steering wheel angle andpath tracking. Simulation results show that the second control program has better integralperformance than the first one.(5) Coordination strategy for varied steering ratio control and yaw rate control was presented,and yaw rate control was investigated with the reactive of varied steering ratio control. Based onLinear Quadratic Regulator (LQR) optimal control theory, yaw rate controller was designed.Simulation testes in limiting conditions were conducted to verify the effectiveness of the proposedcoordination strategy and the yaw rate controller.(6) Transfer characteristics of angular displacement transmission is changed with the interferenceof active steering, which gives rise to the problem that internal corresponding relations betweenvehicle state and steering wheel angle are also affected. Then, a research scheme that vehicle yaw rateand side slip angle are considered as nonlinear mapping of time series of pinion angle and lateralacceleration was put forward. An estimation algorithm based on Adaptive Neuro-Fuzzy InferenceSystem (ANFIS) was proposed to estimate vehicle yaw rate and side slip angle. To verify theestimation accuracy and generalization of the proposed estimation algorithm based on ANFIS,simulation and actual vehicle test data were used, as well as comparative analyses were conductedbetween the performance of the estimation algorithms based on ANFIS and Radial Basis Function(RBF) neural network respectively. Results indicate that the proposed research scheme is effective,and the generalization of the estimation algorithm based on ANFIS is better than that based on RBFneural network.(7) To solve mutations of steering wheel torque with the interference of active steering, twofeed-forward assistant torque correction strategies for assist motor were presented, which can be usedto carry out feed-forward assistant torque correction control for assist motor of EPS system in thewhole speed range, and not limited to the assist ratio takes value in zero when vehicle speed exceedsthe assist speed region. Meanwhile, in view of the evaluation methods of transient characteristics for step response, two evaluation indexes were put forward to make quantitative comparison of the twofeed-forward assistant torque correction strategies. Results indicate that the correction controlprogram based on the output of torque sensor can achieve better control performance than that basedon vehicle model, and has better adaptability of vehicle speed.(8) Based on virtual experiment technology, three-dimensional model of the EPS systemintegrated with active steering was built by the CAD module of UG software. To verify the transfercharacteristics of torque and angular displacement for the proposed EPS system, as well as theeffectiveness of the assistant torque correction strategies, analyses on kinematics and dynamics of thesteering system were conducted by using CAE module of UG software. To validate the effectivenessof the proposed coordination strategy and the yaw rate controller, virtual testes in limiting conditionswere conducted based on CarSim software.更多还原