基于GPS载波相位信号确定运动体姿态的关键技术

应用GPS载波相位信号确定运动体姿态,针对二维两天线系统情况,设计了姿态测量系统的硬件结构及算法流程框图,文章介绍了GPS姿态测量的关键技术：GPS姿态观测方程、整周模糊度的解算、误差的消除。从系统设计角度证明了技术的可行性。     

磁测式船舶姿态自动测量装置研究

利用三维磁传感器直接敏感在同状态下两个不同坐标系中的船舶综合磁场三维磁感应强度,研制了出一种新型的船舶姿态实时测量系统,并对该系统的测量原理,误差分析,校正原理与方法等作了较全面的论述。     

Multimodal travel groups and attitudes: A latent class cluster analysis of Dutch travelers

For developing sustainable travel policies, it may be helpful to identify multimodal travelers, that is, travelers who make use of more than one mode of transport within a given period of time. Of special interest is identifying car drivers who also use public transport and/or bicycle, as this group is more likely to respond to policies that stimulate the use of those modes. It is suggested in the literature that this group may have less biased perceptions and different attitudes towards those modes. This supposition is examined in this paper by conducting a latent class cluster analysis, which identifies (multi)modal travel groups based on the self-reported frequency of mode use. Simultaneously, a membership function is estimated to predict the probability of belonging to each of the five identified (multi)modal travel groups, as a function of attitudinal variables in addition to structural variables. The results indicate that the (near) solo car drivers indeed have more negative attitudes towards public transport and bicycle, while frequent car drivers who also use public transport have less negative public transport attitudes. Although the results suggest that in four of the five identified travel groups, attitudes are congruent with travel mode use, this is not the case for the group who uses public transport most often. This group has relatively favorable car attitudes, and given that many young, low-income travelers belong to this group, it may be expected that at least part of this group will start using car more often once they can afford it. Based on the results, challenges for sustainable policies are formulated for each of the identified (multi)modal travel groups.     

A study of carpooling behaviour using a stated preference web survey in selected cities of India

This paper analyses how people perceive the idea of carpooling and evaluate preferences while making a decision to join a carpool. Analysing data from a web-based stated preference survey in India reveals that cognitive attitudes play a significant role in evaluating the perceived advantages and disadvantages of carpooling whereas intentions to carpool are associated with perceived negative evaluations. A factor analysis identifies two latent attitudinal factors: a ‘time–convenience’ factor that discourages carpooling and a ‘private–public cost’ factor that encourages carpooling. The study analyses the influential attributes – extra travel time, walking time to reach meeting point, waiting time at pickup point and cost savings – as explanatory variables for the utility of carpooling. Cost savings prove to be the most significant attribute when combined with other attributes, followed by extra travel time. The study provides the implications to policy-makers of designing promotional tools to improve the propensity of carpooling among single occupant vehicle drivers.     

一种计及姿态变化的船舶阻力预报方法

对于航行于水面的舰船,船体姿态会随着航速的增加在航行中发生明显变化,这种姿态变化后的阻力较通常计算的以约束模型为基准的阻力预报是有明显差别的。采用CFD方法实现了以KCS船为模型进行模型自由状态下的阻力预报,并和相关实验数据进行了比较。结果表明,该方法避免了由于船体运动造成流场网格扭曲与计算发散等问题,具有良好的稳定性。另外,该方法充分考虑了船体姿态的影响,计算结果令人满意。     

Travel mode choices in small cities of China: A case study of Changting

The existing literature on urban transportation planning in China focuses primarily on large cities and neglects small cities. This paper aims to fill part of the knowledge gap by examining travel mode choice in Changting, a small city that has been experiencing fast spatial expansion and growing transportation problems. Using survey data collected from 1470 respondents on weekdays and weekends, the study investigates the relationship between mode choice and individuals’ socio-economic characteristics, trip characteristics, attitudes, and home and workplace built environments. While more than 35 percent of survey respondents are car owners, walk, bicycle, e-bike, and motorcycle still account for over 85 percent of trips made during peak hours. E-bike and motorcycle are the dominant means of travel on weekdays, but many people shift to walking and cycling on weekends, making non-motorized and semi-motorized travel especially important for non-commuting trips. Results of multinomial logistic regression show that: (1) job-housing balance might exert different effects on mode choice in different types of urban areas; (2) negative attitude towards e-bike and motorcycle is associated with more walking and cycling; and (3) land use diversity of workplace is related to commuting mode choice on weekdays, while land use diversities of both residential and activity places do not significantly affect mode choice on weekends. Our findings imply that planning and design for small cities needs to differentiate land use and transportation strategies in various types of areas, and to launch outreach programs to shift people’s mode choice from motorized travel to walking and cycling.     

水翼艇最佳控制研究

本文探讨了最佳控制在水翼艇姿态控制上的应用,使用数字机对全浸式水翼艇的控制进行辅助设计和闭路仿真。初步结果表明:基于现代控制理论设计的自动驾驶仪,可以取得显著优于古典控制的控制效果。对所论最佳控制系统的实现,本文提出并论证了一种切实可行的水翼艇分级-分散微处理机控制方案。     

Level and attitude control of the active suspension system with integral and derivative action

A 7-DOF full-car model with optimal active control suspension is utilized to evaluate the vehicle dynamic performances which are achieved through proposed controllers. The optimal controller, which includes the integral action for the suspension deflection, considerably improves the attitude control of a vehicle because the rolling and pitching motion in cornering and braking maneuvers are reduced, respectively. In the viewpoint of level control, the integral control acting on the suspension deflection results in the zero steady-state deflection in response to static body forces and ramp road input. The dynamic characteristics of the suspension control system are evaluated in terms of time domain and frequency domain. The simulations in the time domain demonstrate the advantages of the active suspension system obtained by penalizing the integral and derivative of suspension deflections and the derivative of roll and pitch angles in the performance index. The frequency characteristic curves obtained by simulations regarding integral action or derivative action show the increase of both ride comfort and road-holding performances by maximizing the use of suspension deflections. The potential of derivative control is shown by the performances of the car traveling over a bump and braking.     

如何做好试验检测工作

主要阐述试验检测工作的重要性,试验检测人员应竭尽全力把工作做到最好。     

基于测姿GPS及电子罗盘组合的姿态估计算法

针对低成本姿态测量应用需求,研究了由测姿GPS与电子罗盘组合的姿态估计算法。以捷联姿态误差模型为基础,利用等效倾角误差表示姿态误差,引入角速率误差作为状态参量,通过四元数微分方程推导等效倾角误差传递模型。从GPS双差载波相位测量方程和电子罗盘地磁矢量方程出发,从观测量的物理意义出发推导了等效倾角误差为状态参量的非线性观测方程。采用扩展卡尔曼滤波对姿态参数进行状态估计。车载实验表明该算法能够有效地提高姿态测量精度和系统的鲁棒性,具有较好的实用性。