【作者】 刘伟；

【导师】 杨志华；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2018， 硕士

【摘要】 随着车辆控制技术的进一步发展,整车厂对电动助力转向系统提出了更高的要求。为了提升电动助力转向系统的性能,相应的转向系统供应商采用了性能更高的永磁同步电机作为电动助力转向系统的助力电机,同时也对系统控制算法进行了设计和改进。但是,就国内研究现状来看,基于永磁同步电机的电动助力转向系统仍然存在很多问题,比如系统不稳定、快速转向迟滞、松手后转向盘回不到中位、慢速转向卡顿等问题,需要深入研究对电动助力转向系统的控制算法,以期提高车辆的转向性能和驾驶员的操控体验。针对基于永磁同步电机的电动助力转向系统,本文主要建立了比较接近实际的系统简化模型,通过变PI反馈弱磁控制提升了高速运行工况下永磁同步电机的输出性能,通过系统回正需求分析,优化了系统主动回正控制性能,并采用信号注入方法进行摩擦补偿。具体的转向系统研究工作如下:1.建立了电动助力转向系统全阶模型和简化模型;通过改变电机输入电压辨识出了转向系统上半部分模型中的阻尼参数;通过向系统注入伪随机信号得到系统传递函数增益曲线;通过系统参数辨识发现了轮胎阻尼的两种存在形式;通过传递函数拟合验证了转向系统简化模型。2.建立了电机数学模型,推导出了转矩表达式;解析和优化了电机角度参数,且参数优化效果明显;深入研究了电机SVPWM矢量控制算法;在分析电机弱磁理论和最优电流运行轨迹的基础上,发现了电机弱磁必须采用变PI控制的原因,并提出一种变PI反馈弱磁控制算法;电机台架试验不仅确定了多组PI控制参数,还证明了本文所提出的弱磁控制算法的实用性。3.分析了现有转向系统主动回正遗留问题,尤其是基本助力和主动回正的耦合问题;基于分析,明确了主动回正的功能需求;针对主动回正需求,设计了中低速工况下主动回正状态的控制算法,同时也提出了主动回正力矩控制算法;经过多次实车试验,确定了主动回正算法中参数的最优值,实现了主动回正性能的优化和转向手感的提升。4.基于对比较经典的静摩擦+Coulomb+黏性+Stribeck摩擦模型的分析,对转向系统摩擦特性进行定性研究,并得到了比较切合实际的转向系统摩擦特性曲线;针对转向系统摩擦特性,分析得到了摩擦补偿的对象,采用了一种简单的信号注入摩擦补偿策略,并通过实车验证确定了注入信号的最优参数值;试验结果表明,在中低车速左右轻转向工况下,本文所采用的摩擦补偿策略消除了转向卡顿情况。更多还原

【Abstract】 With the further development of vehicle control technology,vehicle manufacturers have put forward higher requirements for electric power steering systems.In order to improve the performance of the electric power steering system,the corresponding steering system suppliers not only use the permanent magnet synchronous motor with higher performance as the assisting motor of the electric power steering system,but also has designed the system control algorithm.However,as far as the domestic research status is concerned,there are still many problems in the electric power steering system based on permanent magnet synchronous motors,such as system instability,hysteresis problem of rapidly steering,the steering wheel can not return to middle position after driver releases it,caton problem of slowly steering.So depth study of the control algorithm need to be done for the electric power steering system to improve vehicle’s steering performance and driver’s control experience.Focus on the electric power steering system based on permanent magnet synchronous motor,this paper mainly establishes a system simplification model that is relatively close to reality.Under high-speed operating conditions,by using the strategy of variable PI feedback control in flux weakening field,the output performance of the permanent magnet synchronous motor is improved.By analyzing requirement of active return,the performance of active return control is improved.And a signal injection method was used to compensate system friction.The detail steering system research and vehicle test work is as follows:1.Established a full-order model and simplified model of electric power steering system;The damping parameters in the upper part of the steering system are identified by changing the motor input voltage;and the system transfer function gain curve is obtained by injecting a pseudo-random signal into the system;through system parameters identification,two damping forms of tire are discovered;at the same time,the simplified steering system model has also been verified by transfer function fitting.2.In order to improve the operating performance of the motor,the mathematical model of the motor is established and the torque expression is deduced;The motor angle parameter is analyzed and optimized,and the parameter optimization effect is obvious.The SVPWM vector control algorithm of motor is studied in depth;based on the analysis of flux weakening and the optimal current running trajectory,the reason for the variable PI control in the flux weakening field is found,and then a variable PI feedback control algorithm is proposed;the motor bench test not only identifies multiple sets of PI control parameters,but also proves the feasibility of the flux weakening control algorithm proposed in this paper.3.The remaining issues about active return are analyzed,especially the coupling problem of basic assistance function and active return function;based on the analysis of legacy issues,the functional requirements of active return are clearly defined;under medium and low vehicle speed,state control and torque control algorithm of active return are designed based on the active return requirements.After several vehicle tests,the optimal values of the parameters in the active return algorithm are determined,and the optimization of the active return performance and steering fell is realized.4.Based on the analysis of the classic friction model of static friction + Coulomb + viscosity + stribeck,the friction characteristics of the steering system are studied,and a more realistic steering system friction characteristic curve is obtained.According to the friction characteristics of steering system,the friction compensation object is obtained.A simple friction compensation strategy of signal injection is used,and the optimal parameters’ values of the injected signal are determined through vehicle test.The test result shows that the friction compensation method eliminates the steering caton under low and medium vehicle speed.更多还原