Discretised link travel time models based on cumulative flows: Formulations and properties

In the research area of dynamic traffic assignment, link travel times can be derived from link cumulative inflow and outflow curves which are generated by dynamic network loading. In this paper, the profiles of cumulative flows are piecewise linearized. Both the step function (SF) and linear interpolation (LI) are used to approximate cumulative flows over time. New formulations of the SF-type and LI-type link travel time models are developed. We prove that these two types of link travel time models ensure first-in-first-out (FIFO) and continuity of travel times with respect to flows, and have other desirable properties. Since the LI-type link travel time model does not satisfy the causality property, a modified LI-type (MLI-type) link travel time model is proposed in this paper. We prove that the MLI-type link travel time model ensures causality, strong FIFO and travel time continuity, and that the MLI-type link travel time function is strictly monotone under the condition that the travel time of each vehicle on a link is greater than the free flow travel time on that link. Numerical examples are set up to illustrate the properties and accuracy of the three models.     

基于遗忘递推最小二乘与自适应无迹卡尔曼滤波的锂电池SOC估计

针对无迹卡尔曼滤波(UKF)在噪声不确定及工况复杂情况下锂电池荷电状态(SoC)估计精度低的问题,提出基于自适应无迹卡尔曼滤波(AUKF)的估计方法.建立了基于二阶RC等效电路模型的锂电池状态方程,采用遗忘递推最小二乘(FFRLS)参数辨识方法,将Sage-Husa自适应滤波算法与UKF相结合对系统噪声协方差进行实时更...     

Equivalent linear pseudostatic and dynamic modelling of vertically vibrating monopile

To optimize offshore wind turbine (OWT) design, an engineering tool has been developed allowing for a detailed investigation of the effects of nonlinear soil stiffness and damping on foundation dynamics. We have studied the response of a vertically oscillating offshore wind monopile foundation in a realistic soil profile subjected to loads between 1 and 200 MN in the frequency range 0–10 Hz with pseudo-static and equivalent linear dynamic model. The non-linear soil behaviour is modelled with an equivalent linear method with shear modulus reduction and damping curves as input. The tool is verified and validated by comparison with elasto-dynamic model and experiments. With increasing load amplitudes foundation stiffness increases and damping decreases. For large load amplitudes the lower part of the pile foundation contributes more to foundation damping. The results indicate the nonlinear foundation stiffness and damping can be modelled rationally by combining stiffness and hysteretic damping from nonlinear static tools with apparent mass and radiation damping from elasto-dynamic analysis. The tool can be used to compute soil springs and dampers based on laboratory-based soil stiffness and damping.     

Control of a hydraulically actuated continuously variable transmission

Vehicular drivelines with hierarchical powertrain control require good component controller tracking, enabling the main controller to reach the desired goals. This paper focuses on the development of a transmission ratio controller for a hydraulically actuated metal push-belt continuously variable transmission (CVT), using models for the mechanical and the hydraulic part of the CVT. The controller consists of an anti-windup PID feedback part with linearizing weighting and a setpoint feedforward. Physical constraints on the system, especially with respect to the hydraulic pressures, are accounted for using a feedforward part to eliminate their undesired effects on the ratio. The total ratio controller guarantees that one clamping pressure setpoint is minimal, avoiding belt slip, while the other is raised above the minimum level to enable shifting. This approach has potential for improving the efficiency of the CVT, compared to non-model based ratio controllers. Vehicle experiments show that adequate tracking is obtained together with good robustness against actuator saturation. The largest deviations from the ratio setpoint are caused by actuator pressure saturation. It is further revealed that all feedforward and compensator terms in the controller have a beneficial effect on minimizing the tracking error.     

并列双幅桥面斜拉桥支承体系的平面等效模拟

并列双幅桥面斜拉桥属于空间体系结构，理应应用三维空间有限元程序来完成其静力分析。作者采用了等效双悬臂梁的机构进行平面等效模拟以，使塔、墩、梁、索四者处于共平面工作，从而可以应用常用的平面杆系专用程序，使计算大为简化，且具有较满意的精度。     

船舶环形供电网络的短路电流计算

船用环形供电网络短路电流的研究目前处于初级阶段，本文使用等效发电机法和状态方程迭代求解法对环形网络的短路电流进行了研究。等效发电机法可通过发电机与阻抗串联等效和不同型号发电机并联等效将网络简化，从而求得短路电流。迭代求解法中，供电网络模型由状态方程表示，离散后求解，仿真中利用了MATLAB的强大数值计算功能，方便地分析各支路电流。最终给出了两种方法得出的计算结果及仿真曲线，为研究更复杂的环形及网型网络短路电流打下了基础。     

最佳逼近线性化与常规线性化方法的比较

本文给出了最佳逼近线性化方法与台劳级数线性化方法的比较,说明了两种方法适用的范围,并进行了误差分析。     

基于自适应迭代学习控制的工作艇收放装置主动减摆策略研究

工作艇收放装置主要用于完成快速、安全地将舰船上的小艇及人员移至水面,或安全回收工作艇至舰船上等海上任务。针对这一典型的欠驱动机械系统,采用拉格朗日方程的方法建立其动力学模型。根据舰船在海上的实际运动情况,对系统的二维动力学模型进行描述,分析小艇摇摆的二维平面摆角,研究其在船体运动影响下的变化情况。然后在上述非线性动力学模型的基础上,针对系统的摆动部分,为其设计自适应迭代控制闭环控制器,达到消摆的目的。最后,仿真结果证明了此控制方法的有效性。     

短波功率放大器非线性失真的改进策略

分析短波功率放大器非线性失真的产生原因和影响,总结功率放大器中常用的线性化方法,比较其中的功率回退法和预失真法的优缺点.对数字基带预失真法的工作原理进行重点分析,并对其作为短波功率放大器线性化方案的可行性进行了探讨.     

EMS型磁浮列车模块的运动耦合研究

EMS型低速磁浮列车通常采用模块化的转向架结构,模块是集悬浮、导向和牵引功能于一身的基本功能单元.模块内部的2个悬浮端通过刚体连接,导致两端的运动状态互相耦合.常用的处理方法是将这种耦合作为系统的外部干扰,通过提高系统的鲁棒性加以抑制.本文从机械运动的角度,研究了EMS型低速磁浮列车模块的耦合问题,提出通过解耦算法实现2个悬浮端之间的运动解耦.首先在对物理模型进行合理简化和假设的基础上,建立了模块悬浮系统的数学模型,并以此为基础分析了模块运动耦合的本质,然后提出了通过反馈线性化方法实现模块运动电气解耦的方案.仿真结果表明,模块的运动耦合对悬浮系统动态特性具有显著的影响,本文提出的解耦方案可有效地解决耦合问题,简化悬浮控制器的设计,提高悬浮系统的性能.