EPS助力特性的改进RBF神经网络方法

针对电动助力转向(EPS)助力特性的非线性问题,提出应用径向基(RBF)神经网络强非线性能力进行电动助力转向(EPS)助力特性曲面拟合方法,并做出改进。应用改进均值聚类方法(k-means)对数据进行聚类,获取基函数参数,再用梯度下降法训练网络权值,并利用最优停止法对网络进行了优化。实验结果表明,该改进方法避免了过拟合现象,提高了网络的泛化能力,并且具有网络训练时间短,拟合的曲面精度高,预测能力强等优点。     

压电式快速控制反射镜的迟滞特性及线性化

针对压电式快速控制反射镜(Fast Steering Mirror,FSM)的迟滞问题,分析了压电式FSM的工作原理和迟滞特性,建立了基于Bouc-Wen算子的压电式FSM的数学模型及其参数辨识方法。通过Bouc-Wen算子模拟压电式FSM输出镜面偏转角度中的迟滞分量,并根据在两个相位相同的输入驱动电压信号下压电式FSM的输出镜面偏转角度曲线辨识Bouc-Wen算子的全部参数。在此基础上,提出了压电式FSM的前馈线性化方法。为了验证提出的数学模型和线性化方法的原理,建立了压电式FSM及其线性化控制器的快速原型系统和Bouc-Wen算子参数辨识实验装置。实验结果表明:本文提出的参数辨识方法能够准确辨识压电式FSM的Bouc-Wen算子参数,提出的前馈线性化方法能够将压电式FSM的输出镜面偏转角度与输入控制电压的线性度提高到2.3%,迟滞误差减小到±0.5%,满足实际应用对精确控制压电式FSM的要求。     

基于刚柔耦合模型的工程车辆转向机构设计研究

应用多体系统动力学方法对SGA3550矿用汽车转向机构进行设计研究。首先,应用有限元软件建立转向横拉杆的柔性体模型,并得到其固有模态和振型;其次,结合ADAMS软件建立车辆的刚柔耦合模型;最后,对比分析多刚体模型和刚柔耦合模型的动力学特征,包括转向过程中的车轮转角、直线行驶时的轮距和车轮反向跳动过程中的车轮摆角。结果表明,刚柔耦合模型更为准确地反映了车辆的动力学特征,为转向机构设计提供了更为准确的依据。     

自适应神经模糊推理的四轮转向车辆转向控制研究

模糊规则的建立和隶属度函数的确定是设计模糊系统的难题.基于神经网络和模糊逻辑的自适应神经模糊推理系统,能够从仿真数据中自动提取出If-Then规则.并在Matlab/Simulink软件中,建立包含侧向运动、横摆运动、侧倾运动三个自由度的四轮转向车辆三自由度动力学模型.将得到的If-Then规则读取到模糊控制器中和三自...     

联合应用MUSIC与FastICA算法实现多个时空混叠源信号的波形重建

联合应用多信号分类与快速独立分量分析算法,分离多个时空混叠源信号,并重建其波形。利用多信号分类的方法,基于二阶统计量辨识观测信号的噪声子空间,并搜索与噪声子空间和方向矢量同时正交的多源位置参数,实现源信号波达方向的估计。利用基于固定点迭代的快速独立分量分析方法,通过最小化互信息这一高阶统计量测度来估计传感器阵列的增益模式,进而估计未知的源信号混叠矩阵。实现多个时空混叠源信号的分离与波形的重建。试验结果表明,基于多信号分类与快速独立分量分析联合的新方法,能有效辨识复值时空混叠矩阵,正确分离并重建来自不同方向的混叠源信号,从而为后续的进一步应用(如弱信号检测、故障诊断等)奠定基础。     

机载刚性支撑式快速控制反射镜设计

设计了一款紧凑型刚性支撑式快速控制反射镜(FSM),以适应机载运动平台的高振动、大冲击和高低温等恶劣工作环境。考虑机载FSM的工作需求,分别对FSM的支撑轴系、驱动元件和测角元件等进行设计与选择。针对刚性支撑轴系设计了轴系间隙调整机构,提高了FSM系统的轴系精度,进一步增大了FSM的承载能力;针对机载FSM研制了专用小尺寸微位移测量传感器,通过将4个传感器非轴线对称布置,并利用二次差分的方式实现反射镜位置的实时监测,进一步减小了FSM系统的体积,提高了它的测量精度。最后,对机载FSM的控制带宽和指向精度进行了实验检测。结果显示:所设计的FSM系统控制带宽约为110Hz,方位指向误差不超过3.4″,俯仰指向误差不超过3.8″,表明所设计的FSM控制系统稳定、响应速度快、指向精度高,满足机载运动平台的应用要求。     

基于FPGA的电动助力转向系统

采用Verilog硬件描述语言自顶向下的设计方法,通过FPGA实现了车辆电动助力转向系统的设计.论述了计数模块、查询模块与电机控制模块的工作原理,通过对车速、转向盘扭矩和转角查表得到对应的助力控制、回正控制和阻尼控制模式与控制值,实现了车辆低速时的转向轻便性和高速时对驾驶员路感的保证.利用Cyclone EP2C8控制板在实验台架上的实验表明,系统能够实现所设计的功能,并具有较高的响应速度.     

Identifying cognitive distraction using steering wheel reversal rates

The influence of driver distraction on driving performance is not yet well understood, but it can have detrimental effects on road safety. In this study, we examined the effects of visual and non-visual distractions during driving, using a high-fidelity driving simulator. The visual task was presented either at an offset angle on an in-vehicle screen, or on the back of a moving lead vehicle. Similar to results from previous studies in this area, non-visual (cognitive) distraction resulted in improved lane keeping performance and increased gaze concentration towards the centre of the road, compared to baseline driving, and further examination of the steering control metrics indicated an increase in steering wheel reversal rates, steering wheel acceleration, and steering entropy. We show, for the first time, that when the visual task is presented centrally, drivers’ lane deviation reduces (similar to non-visual distraction), whilst measures of steering control, overall, indicated more steering activity, compared to baseline. When using a visual task that required the diversion of gaze to an in-vehicle display, but without a manual element, lane keeping performance was similar to baseline driving. Steering wheel reversal rates were found to adequately tease apart the effects of non-visual distraction (increase of 0.5° reversals) and visual distraction with offset gaze direction (increase of 2.5° reversals). These findings are discussed in terms of steering control during different types of in-vehicle distraction, and the possible role of manual interference by distracting secondary tasks.     

Driver behavior following an automatic steering intervention

The study investigated driver behavior toward an automatic steering intervention of a collision mitigation system. Forty participants were tested in a driving simulator and confronted with an inevitable collision. They performed a naïve drive and afterwards a repeated exposure in which they were told to hold the steering wheel loosely. In a third drive they experienced a false alarm situation. Data on driving behavior, i.e. steering and braking behavior as well as subjective data was assessed in the scenarios. Results showed that most participants held on to the steering wheel strongly or counter-steered during the system intervention during the first encounter. Moreover, subjective data collected after the first drive showed that the majority of drivers was not aware of the system intervention. Data from the repeated drive in which participants were instructed to hold the steering wheel loosely, led to significantly more participants holding the steering wheel loosely and thus complying with the instruction. This study seems to imply that without knowledge and information of the system about an upcoming intervention, the most prevalent driving behavior is a strong reaction with the steering wheel similar to an automatic steering reflex which decreases the system's effectiveness. Results of the second drive show some potential for countermeasures, such as informing drivers shortly before a system intervention in order to prevent inhibiting reactions.     

Development of a new capacitive matrix for a steering wheel's pressure distribution measurement

Pressure distribution measurements are becoming increasingly important in the automotive field for ergonomic optimization of components like seats or steering wheel. Nowadays, traditional sensors shows several drawbacks such as response variation in time, low sensitivity and high level of intrusiveness. Moreover the great difficulty of carrying out dynamical analysis in the area of interest highly limits their use. A new type of matrix, now available, promises to overcome such problems, and it has been widely tested in the automotive field. The matrix is based on a series of condensers which vary the capacity depending on the pressure applied on their surface. The high sensitivity and the chance of monitoring pressure distribution with frequency contents up to 200 Hz make this tool particularly suitable for evaluating steering wheel's goodness effectiveness in an on-road test.