Vehicle rollover avoidance by application of gain-scheduled LQR controllers using state observers

Many researches have been conducted in the area of control applied to vehicle dynamics, aiming at reducing the possibility of the occurrence of the type of accident known as rollover. In this research, based on a common nonlinear model and its linearisation, a method for properly selecting matrices for solving the Riccati equation considering different speeds was proposed. The method showed in which ways speed really influences the choice of controller gains. By developing the dynamic equations for the yaw- and roll-coupled motions and modelling of controllers and state observers, it is possible to compare the efficacy of this control strategy using both linear and nonlinear simulations using Matlab. Significant results were obtained regarding the reduction of the rollover coefficient for a double-lane change manoeuvre at different speeds, thus indicating advantages of using this controller in practical cases.     

Design of tyre force excitation for tyre–road friction estimation

Knowledge of the current tyre–road friction coefficient is essential for future autonomous vehicles. The environmental conditions, and the tyre–road friction in particular, determine both the braking distance and the maximum cornering velocity and thus set the boundaries for the vehicle. Tyre–road friction is difficult to estimate during normal driving due to low levels of tyre force excitation. This problem can be solved by using active tyre force excitation. A torque is added to one or several wheels in the purpose of estimating the tyre–road friction coefficient. Active tyre force excitation provides the opportunity to design the tyre force excitation freely. This study investigates how the tyre force should be applied to minimise the error of the tyre–road friction estimate. The performance of different excitation strategies was found to be dependent on both tyre model choice and noise level. Furthermore, the advantage with using tyre models with more parameters decreased when noise was added to the force and slip ratio.     

Robust control and actuator dynamics compensation for railway vehicles

A robust controller is designed for active steering of a high speed train bogie with solid axle wheel sets to reduce track irregularity effects on the vehicle’s dynamics and improve stability and curving performance. A half-car railway vehicle model with seven degrees of freedom equipped with practical accelerometers and angular velocity sensors is considered for the H_∞ control design. The controller is robust against the wheel/rail contact parameter variations. Field measurement data are used as the track irregularities in simulations. The control force is applied to the vehicle model via ball-screw electromechanical actuators. To compensate the actuator dynamics, the time delay is identified online and is used in a second-order polynomial extrapolation carried out to predict and modify the control command to the actuator. The performance of the proposed controller and actuator dynamics compensation technique are examined on a one-car railway vehicle model with realistic structural parameters and nonlinear wheel and rail profiles. The results showed that for the case of nonlinear wheel and rail profiles significant improvements in the active control performance can be achieved using the proposed compensation technique.     

FLAC3D流固耦合渗流模型探讨

FLAC3D有限元软件内置4种渗流模型,直接决定计算结果正确与否。渗流场在三维空间中分布复杂,难以根据计算公式定量选用何种模型,不同文献渗流模型选择标准也不相同。为了找到简单、快速、合理的选择方法,有必要对4种渗流模型进行受力分析。以一100 m×100 m×10 m各项同性弹性立方体为例,基于4种渗流模型设计4种工况。通过对比和分析各工况下总应力和孔隙水压分布情况,主要结论如下： 1）模型A、模型C外荷载均由土颗粒骨架承担,其余2种模型流体也参与受力; 2）流体分担外荷载的比例与刚度系数和时间有关; 3）FLAC3D流固耦合过程正是通过调整刚度比、打开和关闭力学-流体进程来实现的。目前我国流固耦合计算基本基于FLAC3D有限元软件,文中结论适用于基础、隧道、基坑等工程,可供相关从业人士借鉴参考。     

液罐车液体侧向晃动多质量椭圆规摆模型

为深入研究液罐车整车侧向动力学行为, 探讨了椭圆形(圆形) 截面罐体等效机械液体侧向晃动模型; 基于计算流体动力学(CFD) 软件FLUENT, 评价了椭圆规摆(TP) 模型的预测精度, 分析了充液比、罐体截面椭圆率和激励频率对模型预测精度的影响; 提出了广义多质量TP模型, 通过合理分配液摆各部分质量及其间距来适应罐体截面椭圆率和充液比的变化; 基于Lagrange方法推导了广义多质量TP模型动力学方程, 给出了双质量TP (DMTP) 模型的质量比和质量间距参数的获取方法和拟合表达式, 并采用CFD方法评价了DMTP模型的预测精度。分析结果表明: 由TP模型得到的晃动力矩总体较CFD方法的小, 随着充液比和激励频率的增加, 预测误差变大, 充液比由30%增加到80%时, 峰值晃动力矩预测误差由15%增加到65%左右, 这主要是由于TP模型是在液体小初始倾斜角自由晃动条件下拟合所得, 当充液比和晃动频率较高时, 液摆的摆臂长度和参与晃动的液体质量都小于实际情况; DMTP模型在大部分充液比、罐体截面椭圆率和激励频率条件下都有相对稳定且较高的预测精度, 激励频率分别为0.2、0.3Hz时, DMTP模型的最大晃动力矩预测均方根误差均值和标准差分别比TP模型小54.2%、43.9%和45.1%、31.2%, 预测精度较TP模型有明显提高, 特别是能够较好地弥补TP模型在高充液比时预测误差较大的不足。     

集装箱码头作业系统层次化、并行、异构与可重构计算模型

基于计算思维和计算透镜, 分析了集装箱码头的装卸作业与调度决策, 基于“并行计算”、“异构计算”和“可重构计算”提出了计算物流视角下的集装箱码头作业层次化、并行、异构与可重构计算模型; 将计算机科学领域中多种典型计算体系结构的设计思想和运作机制, 泛化、迁移、修正、融合和定制到集装箱码头作业系统中, 设计了面向此计算模型的混合调度策略, 提出了集装箱码头调度新的抽象计算模型与工程解决路径; 以某大型集装箱码头为实例, 基于集装箱码头作业层次化、并行、异构与可重构计算模型, 进行了物流广义计算自动化的设计与性能评估。研究结果表明: 采用计算模型能确定码头的集装箱吞吐量上限, 实例中约为码头年设计能力的2.75倍; 在满负荷情况下, 基于等待作业集装箱队列的负载均衡调度策略和基于等待作业船型的负载均衡调度策略均能将大型集装箱干线船舶物流广义计算任务延迟缩短约17 h; 在明显作业过载时, 前者能将物流广义计算任务延迟减少100~110 h, 后者能减少约120 h; 在满负荷和作业过载情况下, 2种策略均能缩短大型集装箱干线船舶物流广义计算访问存储时间1~2 h, 后者在作业过载情况下表现更佳; 2种策略都能很好地优先服务重点班轮集合, 且有各自对应的适用状况和调度重点, 码头管理者可根据具体情况选择适用。     

内燃机曲轴的弯扭耦合非线性振动分析

以内燃机曲轴单位曲柄为研究对象,着重考虑刚度不对称和质量偏心的影响,建立了系统的非线性运动微分方程,利用数值方法对曲轴的非线性动力学特性进行了仿真.结果表明:随着质量偏心的增加,弯扭耦合区的范围增大,系统运动由周期运动变为概周期运动;随着刚度不对称系数的增加,系统出现环面倍化分岔,并转变为混沌运动;随着扭转刚度的增加,系统的运动趋于稳定.     

反应堆吊篮流致随机响应理论分析

讨论了吊篮结构流致振动的均方根响应。通过将流体力划分为简谐振动流体力和脉动流体两部分,结合结构有限元离散技术,建立了吊篮结构的流致随机响应不依赖于流体压力实验数据的纯理论分析方法。着重考查了平均流速、湍流强度及湍流尺度等几个主要参数对结构均方根值的影响。     

高速磁浮列车对轨道的动力作用及其与轮轨高速铁路的比较

研究了现有文献关于高速列车动力学方面的论述, 就高速磁浮列车对轨道的动力作用及其与轮轨高速铁路的比较展开讨论。得到的主要结论是: 地面高速轨道交通应以300 km/h左右的轮轨高速铁路为主体; 在需要400~ 600 km/h超高速的特定条件下, 也可以采用磁浮高速列车, 作为一种补充。因此, 一方面要积极修建上海浦东机场高速磁浮试验线, 一方面要尽早启动京沪轮轨高速铁路的建设。     

提速货车转向架试验研究

系统地介绍了中国提速货车在滚动振动试验台所进行的动力学性能试验情况,特别是通过滚动振动试验台试验所进行的参数和结构优化过程,分析了这些货车转向架设计中的得失。对货车转向架性能进行了必要的理论研究,分析了主要参数对转向架动力学性能的影响规律,并提出了转向架设计和定型的意见。