Development of control models for the planning of sustainable transportation systems

Planning of sustainable transportation systems requires integration of multiple systems while considering a holistic approach. A limited amount of research has been conducted that simultaneously considers all the transportation, economic activity, environmental and social effects. The proposed research envisages incorporating considerations related to sustainability and providing solutions to stakeholders in policy making. In this paper, a dynamic model for planning and development of sustainable transportation systems is presented. This is given by a system of three nonlinear differential equations representing the dynamics of the three independent states, namely, transportation, activity, and environmental systems. A policy scenario considering investment in energy efficient technologies and its effects on the states is discussed to assist making investment decisions. Optimal control techniques are used to design the controls. The results show that it is possible to formulate an optimal control to achieve the desired target. Numerical results, based on actual parameters, are presented to illustrate the long-term trends of the states. The methodology discussed in this paper will be helpful to decision makers in making optimal decisions. The contribution of this research work is the introduction of a systems and controls methodology to develop optimal policies for the design of sustainable systems.     

Highway voting system: Embracing a possible paradigm shift in traffic data acquisition

The integration of internet and mobile phones has opened the door to a new wave of utilizing private vehicles as probes not only for performance evaluation but for traffic control as well, gradually replacing the role of traffic surveillance systems as the dominant source of traffic data. To prepare for such a paradigm shift, one needs to overcome some key institutional barriers, in particular, the privacy issue. A Highway Voting System (HVS) is proposed to address this issue in which drivers provide link- and/or path-based vehicle data to the traffic management system in the form of “votes” in order to receive favorable service from traffic control. The proposed HVS offers a platform that links data from individual vehicles directly with traffic control. In the system, traffic control responds to voting vehicles in a way similar to the current system responding to prioritized vehicles and providing the requested services accordingly. We show in the paper that the proposed “voting” system can effectively resolve the privacy issue which often hampers traffic engineers from getting detailed data from drivers. Strategies to entice drivers into “voting” so as to increase the market penetration level under all traffic conditions are discussed. Though the focus of the paper is on addressing the institutional issues associated with data acquisition from individual vehicles, other research topics associated with the proposed system are identified. Two examples are given to demonstrate the impact of the proposed system on algorithm development and traffic control.     

Controller design for gating traffic control in presence of time-delay in urban road networks

Recent studies demonstrated the efficiency of feedback-based gating control in mitigating congestion in urban networks by exploiting the notion of macroscopic or network fundamental diagram (MFD or NFD). The employed feedback regulator of proportional-integral (PI)-type targets an operating NFD point of maximum throughput to enhance the mobility in the urban road network during the peak period, under saturated traffic conditions. In previous studies, gating was applied directly at the border of the protected network (PN), i.e. the network part to be protected from over-saturation. In this work, the recently developed feedback-based gating concept is applied at junctions located further upstream of the PN. This induces a time-delay, which corresponds to the travel time needed for gated vehicles to approach the PN. The resulting extended feedback control problem can be also tackled by use of a PI-type regulator, albeit with different gain values compared to the case without time-delay. Detailed procedures regarding the appropriate design of related feedback regulators are provided. In addition, the developed feedback concept is shown to work properly with very long time-steps as well. A large part of the Chania, Greece, urban network, modelled in a microscopic simulation environment under realistic traffic conditions, is used as test-bed in this study. The reported results demonstrate a stable and efficient behaviour and improved mobility of the overall network in terms of mean speed and travel time.     

Achieving transport modal split targets at intermodal freight hubs using a model predictive approach

The increase of international freight commerce is creating pressure on the existing transport network. Cooperation between the different transport parties (e.g., terminal managers, forwarders and transport providers) is required to increase the network throughput using the same infrastructure. The intermodal hubs are locations where cargo is stored and can switch transport modality while approaching the final destination. Decisions regarding cargo assignment are based on cargo properties. Cargo properties can be fixed (e.g., destination, volume, weight) or time varying (remaining time until due time or goods expiration date). The intermodal hub manager, with access to certain cargo information, can promote cooperation with and among different transport providers that pick up and deliver cargo at the hub. In this paper, cargo evolution at intermodal hubs is modeled based on a mass balance, taking into account hub cargo inflows and outflows, plus an update of the remaining time until cargo due time. Using this model, written in a state-space representation, we propose a model predictive approach to address the Modal Split Aware – Cargo Assignment Problem (MSA–CAP). The MSA–CAP concerns the cargo assignment to the available transport capacity such that the final destination can be reached on time while taking into consideration the transport modality used. The model predictive approach can anticipate cargo peaks at the hub and assigns cargo in advance, following a push of cargo towards the final destination approach. Through the addition of a modal split constraint it is possible to guide the daily cargo assignment to achieve a transport modal split target over a defined period of time. Numerical experiments illustrate the validity of these statements.     

Vegetation cover at right of way locations

This research evaluated the status of vegetation cover at right of way locations. Site factors that contributed to low and high ground cover along roadsides and medians were identified. Twenty-nine roadside and median study sites incorporated variability in soil type, elevation, vegetation establishment and cover, seed mixture, slope, aspect, time since planting, and climate. Vegetation cover was measured, and species distribution was identified. Slopes, aspects of the sloping face, and elevations were recorded. Soil samples were tested for nutrients, minerals, texture, and pH. Approximately 50% of the test sites met the 70% cover criteria. Locations of the worst cover (<50%) had soils with high soluble salt content (0.36–1.54 mmhos/cm) or low organic matter values (<1.7%). Vegetation cover was dominated by tall fescue (Festuca arundinacea) and crownvetch (Coronilla varia L.), two species that were included in the current seeding mixture and are considered invasive. To further promote revegetation success and persistence, both maintenance and site specific seed mixtures are needed.     

Model-based predictive control for bicycling in urban intersections

In this paper, a model predictive control approach for improving the efficiency of bicycling as part of intermodal transportation systems is proposed. Considering a dedicated bicycle lanes infrastructure, the focus in this paper is to optimize the dynamic interaction between bicycles and vehicles at the multimodal urban traffic intersections. In the proposed approach, a dynamic model for the flows, queues, and number of both vehicles and bicycles is explicitly incorporated in the controller. For obtaining a good trade-off between the total time spent by the cyclists and by the drivers, a Pareto analysis is proposed to adjust the objective function of the MPC controller. Simulation results for a two-intersections urban traffic network are presented and the controller is analyzed considering different methods of including in the MPC controller the inflow demands of both vehicles and bicycles.     

VLCC软管吊机绞车故障分析

文章就某VLCC软管吊机在调试过程中,绞车只能一个方向旋转的现象,基于丹弗斯PVG32的多路阀控制回路,对绞车的各个相关控制阀组的工作原理及故障产生的原因进行分析,并提出了修理方案。     

基于PLC楼栋恒压供水装置的设计与实现

针对小区楼栋日常供水水压时常变化的特点,设计了一套恒压供水装置方案。该装置以可编程控制器(PLC)为控制核心,通过液位变送传感器把水槽压力值转换成实时模拟电信号,此信号经过FX2N-4转换模块进行A/D转换后,与设定值进行比较,偏差值在PLC内部通过PID回路指令运算,运算后的结果与脉宽调制(PWM)信号的占空比建立对应关系,并经PLC脉冲输出口输出PWM信号,实现对水泵的动态调速控制,实现恒压供水。     

基于EHPN的A-SMGCS机场滑行道运行控制建模

针对先进机场场面引导与控制系统(A-SMGCS)中滑行道运行控制建模, 提出一种基于扩展层次Petri网(EHPN)的建模方法。将滑行道分为交叉口和直线段模块, 然后对模块内部的航空器行为进行封装, 形成基于扩展Petri网的过程层通用模块, 并进一步采用同步合成技术建立过程层模型。利用面向Agent的着色赋时Petri网建立决策层通用模块, 同时将场面运行控制知识与模块的库所和变迁集成, 增强模型的智能决策能力。采用某机场12 h滑行道运行数据进行了仿真试验。研究结果表明: 基于EHPN模型的仿真, 其直线段和交叉口冲突次数分别为6次和11次, 滑行道系统总延误为346 s, 与SIMMOD仿真模型效果相近, 因此, 该建模方法有效。     

水泥稳定碎石基层平整度的控制

本文结合二连浩特至赛罕塔拉一级公路工程实例,分析了水泥稳定碎石基层平整度的影响因素,介绍本项目如何提高水泥稳定碎石基层平整度的综合控制措施。