Model-based control of an electropneumatic brake system for commercial vehicles

A properly functioning brake system is critical for ensuring the safe operation of any vehicle on roadways. Commercial vehicles such as trucks, tractors-trailers and buses are equipped with an air brake system that uses compressed air as the energy transmitting medium. This paper presents a model-based control scheme for an electropneumatic brake system for use in commercial vehicles. A mathematical model for an electropneumatic brake system was developed and corroborated with experimental data. A control scheme was developed based on this model and was used to regulate the pressure of air inside the brake chamber according to a desired pressure trajectory. This control scheme was implemented on an experimental test bench, and its performance was studied for various values of the controller parameter. The control scheme was tested for various desired pressure trajectories reflecting actual brake operation.     

Robust flight-to-gate assignment using flight presence probabilities

In this paper we present a novel method to improve the robustness of solutions to the Flight-to-Gate Assignment Problem (FGAP), with the aim to reduce the need for gate re-planning due to unpredicted flight schedule disturbances in the daily operations at an airport. We propose an approach in which the deterministic gate constraints are replaced by stochastic gate constraints that incorporate the inherent stochastic flight delays in such a way so as to ensure that the expected gate conflict probability of two flights assigned to the same gate at the same time does not exceed a user-specified value. The novel approach is integrated into an existing multiple time slot FGAP model that relies on a binary integer programming formulation and is tested using real-life data pertaining to Amsterdam Airport Schiphol. The results confirm that the proposed approach holds out great promise to improve the robustness of the FGAP solutions.     

Behavior of taxi customers in hailing vacant taxis: a nested logit model for policy analysis

This study models and examines the taxi customers' preferences for hailing vacant taxis on streets. A stated preference survey was conducted to randomly select and interview 1242 taxi customers at taxi stands and pedestrians on streets, who had experiences of taking taxis recently, about their choices under different given hypothetical scenarios. In total, 4968 observations were collected and used for developing the discrete choice models for the analysis. To account for the potential correlations among alternatives, two nested logit models are developed, calibrated, and compared with a standard multinomial logit model in the investigation. The results of likelihood ratio test demonstrate that one of the developed nested logit models is better than the standard multinomial logit model to describe the search behavior of taxi customers. The model results also show that the walking time to and the waiting time at the location for hailing taxis, the extra travel time to the destination because of local circulation for finding a way from the pickup location heading to a passenger's destination, as well as the taxi customers' perceptions for walking to and waiting at taxi stands were found as significant factors to influence their decisions. In addition, the results of market segmentation analysis illustrate the variations in taxi‐search strategies of taxi customers in different districts and regions. Some policy implications on introducing more taxi stands and improving the utilization rates of taxi stands are also discussed. We believe that the proposed models, findings, and discussion are useful for developing micro‐simulation models to evaluate the performance of road traffic networks with taxi services and developing simulation‐based optimization models to answer policy questions related to taxi services. Copyright © 2015 John Wiley & Sons, Ltd.     

A simulation tool for bicycle sharing systems in multimodal networks

This paper presents a methodology for modelling an urban transport system, integrating public bicycles in a multi-modal network. A bike cost function that reproduces the effect of slopes on cycling speeds is proposed. Also, the effect of traffic levels on the attractiveness of cycling routes is taken into account. The model applies the modal split and network assignment phases in a multimodal network with different classes of users. It has been verified over a test network and then validated by applying it to a real case in the city of Santander in Spain. The results obtained make this model a useful decision-making tool to encourage the use of the public bicycle from a sustainable development point of view.     

Controlling Structural Deformation of Surrounding Rock Passed by a Deep-Buried Tunnel北大核心CSCD

Layered rock masses with rapid and serious initial deformation and anisotropy regarding the spatial dis-tribution of the failure are encountered during the construction of many large and deeply buried tunnels on the Lan-zhou-Chongqing railway. It is difficult to deal with the resulting problems with conventional control measures, and additional support measures are frequently needed, which significantly affects construction. Focusing on this special large non-linear deformation, the failure mechanism of the large structural deformation of layered rock masses is thor-oughly analyzed by geological site surveys, laboratory tests, site tests and 3DEC discrete element numerical simula-tion. The research results show that high geostress induces rapid and strong squeezing deformation after excavation in low-strength rock masses, and anisotropy of the layered rock mass controls the stress redistribution after excava-tion and the asymmetrical distribution of tunnel section deformation. Based on the asymmetric deformation mecha-nism of the rock mass, a directional support measure for the disturbance anisotropy of the layered rock mass is pro-posed as a rock mass control to reinforce it in an active way. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

I can’t believe your attitude: a joint estimation of best worst attitudes and electric vehicle choice

The number of conventionally fuelled motor vehicles in use is increasing worldwide despite warnings about finite fossil fuel and the detrimental impacts of burning such fuels. While electric vehicles, the subject of much research, generate far less emissions and offer the potential for power from renewable sources, they are yet to significantly penetrate the market. Tangible barriers such as price and vehicle range still exist, but consumer attitudes also drive behaviour. This paper examines attributes in a framework relatively new to transportation and energy policy; best–worst scaling. This method is widely considered an improvement over traditional methods of eliciting attitudes and beliefs, where respondents select attitudes they find best or worst from a set of attitudinal statements. To avoid potential endogeneity bias, we jointly model attitudes and choice for the first time with best–worst data. It is found that energy crisis, air quality and climate change concerns influence behaviour with respect to vehicle range and that travel behaviour change and forms of government incentives are needed influences on behaviour with respect to vehicle emissions. It is argued that correctly modelling attitudes reduces the error term of the vehicle choice model and provides policy makers with an improved lens for assessing behaviour. Additionally, the methods described within can easily be adapted to other policy scenarios.     

Symbolic transport choice across national cultures: theoretical considerations for research design

A recently empirically isolated latent variable in transport choice is symbolism, which examines what people believe their transport choices say to others about them and how they are judged in a social context. Whilst it is well established that symbolism differs vertically across different socio-economic groups within a country, very little work has been done on how symbolism in transport may differ between similar individuals across nations as a function of national cultural values, and how this may manifest itself in transport choices. If significant differences were to be found then this could have impacts for transport policy formulation and transfer. This paper explores and discusses these issues and concludes that the initial goal of any research into symbolic transport choices across cultures is theoretical fertility, and this is best achieved by adopting Lakatosian research programmes, using theory-driven thematic analysis to develop theoretical models for testing.     

Controller design for soft-disability remedy of the electric power steering system

The electric power steering (EPS) system is designed to reduce the effort exerted by driver on the steering wheel. One of the most common and critical failures of EPS is the soft-disability of the torque sensor or the loss of its signal, which leads to the instant shutdown of the EPS system while turning and causes serious traffic accidents. In this paper, a novel controller based on the self-alignment torque (SAT) estimation was designed to remedy the soft-disability of EPS system. After the SAT estimation method was verified by the empirical Magic Formula (MF) tire model, the remedy control strategy based on the SAT estimation was developed and evaluated by simulations under step and sinusoidal inputs. To further evaluate the performance of the controller on a real vehicle, experiments on a real EPS system were implemented under step and sinusoidal inputs. The results of simulation and experiment using the controller based on estimated SAT showed this controller to be feasible and capable of eliminating the abrupt reaction torque increment caused by shutdown of EPS and of remedying the soft-disability of EPS system under common input signals.     

Interior sound field refinement of a passenger car using modified panel acoustic contribution analysis

Panel acoustic contribution analysis (PACA) is a practical engineering tool for the reduction of interior structure-borne noise in passenger cars. In this study, the current PACA method has been improved for sound field refinement of the entire interior. Two new parameters, the “acoustic contribution sum” and the “total sound field contribution”, are introduced to analyze the interior sound field characterized with multiple field points and sound pressure peaks, and to evaluate the integrated acoustic contributions of auto body panels. In addition, a systematic methodology for automotive interior sound field refinement is also proposed on the basis of the modified PACA method. An example of a passenger car model demonstrates the application of the sound-field-refinement methodology and shows the advantage of using damping layers at optimum locations on the auto body. The example also shows that the modified PACA method has practical significance for refining the interior sound field and decreasing added mass in accord with the trend towards lightweight auto bodies.     

The 2008 New Zealand public transport management act: Rationale, key provisions, and parallels with the United Kingdom

In January 2009, following a lengthy industry review and consultation process, the New Zealand Public Transport Management Act (PTMA) came into force. The Act allows Regional Transport Authorities, as the primary procurers of public transport services, to place either a control or a contracting requirement upon services that are registered as commercial requiring no subsidy. The imposition of either the control or the contracting requirement is designed to facilitate greater system integration, improve service continuity and enhance services to the customer, andallow the Authority to invest in key strategic projects, such as integrated fares and ticketing, so as to grow patronage.The PTMA’s other objective is to ensure improved value for public subsidies. Recent years have seen significant subsidy inflation for seemingly little commensurate benefits. The Act will allow the Regional Transport Authority to achieve greater value for money through improved farebox, a shift to longer, larger contracts to increase competition in the market, a more appropriate allocation of risk, and the removal of the ability of operators to ‘game’ the current system by using strategically placed commercial services as barriers to competition.Similar concerns have also stimulated new legislation in the UK and this paper illustrates the parallels in the environment and proposed response.