Investigation of Train Dynamics in Passing Through Curves Using a Full Model

In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension elements as well as flexibilities of wagon body and bogie frame, and the effect of coupler forces are included in the model. The equations of motion for the train are solved numerically for different train conditions. A neural network was constructed as an element in solution loop for determination of wheel-rail contact geometry. Derailment factor was calculated for each case. The results are presented and show the major role of coupler forces on possible train derailment.

CCS: A Railway Corridor Control System Utilizing Ultra Wideband Radio Technology

Ultra Wide Band (UWB) radio is a unique technology which combines a megabit wireless local area network with a centimeter-resolution radiolocation (RADAR) capability over distances less than 100 meters. A linear chain of UWB nodes can be used to create a hop-by-hop data transmission network, which also forms a RADAR “corridor” along the chain. By co-locating such a chain of nodes along a railroad right-of-way, precise information on the location and velocity of trains could be distributed throughout the corridor. In addition, the radar corridor would detect the introduction of track obstacles such as rocks, people, and automobiles, as well as shifted loads and other high-wide train defects. Finally, the network of nodes would enable off-train communications with payload sensors, locomotive computers, and could also provide wireless connectivity for passenger service.

Suspension Dynamics and Design Optimization of a High Speed Railway Vehicle

The design of suspension systems for high speed railway vehicles involves the simultaneous consideration of those requirements as suspension packaging, ride quality, stability, and cost. A design strategy is presented in this paper that enables an optimal design with respect to these competing requirements. The design strategy consists of four steps including the development of a lumped parameter vehicle model, the determination of vehicle parameters, the formulation of a design objective, and the minimization of the objective to optimize key suspension parameters. The design objective captures vehicle requirements including ride quality, suspension packaging, and wheel/rail holding. Power spectral densities (PSDs) are computed for the vertical vehicle body acceleration, suspension travel and dynamic wheel/rail interaction. The design objective function is calculated based on these PSDs and minimized to yield an optimum. An example suspension design is proposed that improves vehicle ride quality and wheel/rail holding without sacrificing other requirements.

A Dynamic Stiffness and Damping Model for Rail Car Center Plate Polymer Liners

The center plate interface is made up of the body plate attached to the car body bolster, the polymer liner, and the bolster bowl, which is a part of the truck bolster. Roll motion of the rail car leads to the car body bolster rolling over the polymer liner on the truck bolster, which may result in partial loss of contact of the body plate with the polymer liner. This nonlinear phenomenon has a deleterious impact on the rail car dynamics. A technique for creating a center plate dynamic model accounting for the polymer liner and the loss of contact condition is presented here. Material tests were performed to model the stress-relaxation of the liner. A stiffness/damping model of the center plate accounting for the nonlinear effects of the lift-off was developed based on a nonlinear Winkler foundation model and was tested for a one-degree-of-freedom dynamic model. This continuous model was adapted into a 16 stiffness-damping element model to enable its usage in a NUCARS™ rail-car dynamic model.

Determination of Traction Power Distribution System Impedances and Susceptances for AC Railroad Electrification Systems

Electrical characteristics of the traction electrification system, together with the train power demand, headway, and operating scenario, are the key factors in determining the overall system performance. A mathematical procedure for calculation of traction power distribution system line impedances and capacitances is developed using the Alternative Transient Program (ATP). The technique is applied to Direct Feed and Autotransformer Feed traction electrification systems and typical results for one-, two-, three-, and four-track railroads are presented. All self-and mutual impedance and capacitance components are included in the calculations.

Linear Synchronous Motor Propulsion of Small Transit Vehicles

The Linear Synchronous Motor (LSM) has been used for several high speed maglev applications but only recently have developers applied it to urban transit. MagneMotion has worked with the Federal Transit Administration (FTA), as part of their Urban Maglev Project, to develop an LSM propelled maglev transit system called M3. The top speed is only half that of the Transrapid maglev trains now operational in China but by using small vehicles with short headway and rapid acceleration it is possible to achieve outstanding performance at much lower cost. The combination of LSM technology and small vehicles is a cost effective replacement for rotary motor and Linear Induction Motor (LIM) powered trains for all transit applications, including conventional rail and monorail. LSM is the enabling technology that makes it economically and technically feasible to achieve high capacity with short vehicles and, conversely, the use of small vehicles makes LSM propulsion economically attractive. Small vehicles operating with short headway and organized in clusters can achieve high capacity without offline loading. Very precise position sensing and guideway based propulsion and control make short headways safe and affordable. This paper describes the objectives of the MagneMotion LSM development, discusses some of the design features, and presents 3 examples. The examples are based on operational speeds up to 60 m/s (134 mph), accelerations up to 0.16 g, vehicle headways down to 4 seconds, and capacities up to 12,000 passengers per hour per direction (pphpd). Examples include a 1 mile high capacity shuttle, a 4 km unidirectional loop with several stations, and a 30 km high-speed airport connector. Calculations show that an LSM propelled transit system has lower capital cost than conventional transit systems using vehicle-based electric propulsion with either rotary motors or LIMs. Vehicles are simplified, the cost of energy and maintenance is reduced and, most important, users of the transit system experience major reductions in trip times.

Hardware-Software Structure for On-Line Power Quality Assessment: Part I

The main objective of the proposed work is to introduce a new concept of advanced power quality assessment. The introduced system is implemented using applications of a set of powerful software algorithms and a digital signal processor based hardware data acquisition system. The suggested scheme is mainly to construct a system for real time detection and identification of different types of power quality disturbances that produce a sudden change in the power quality levels. Moreover, a new mitigation technique through generating feedback correction signals for disturbance compensation is addressed. The performance of the suggested system is tested and verified through real test examples. The obtained results reveal that, the introduced system detects fast and accurately most of the power quality disturbance events and introduces new indicative factors estimating the performance of any supply system subjected to a set number of disturbance events.

An Overview of Interface Management

Major factors affecting the reliability of railroad or transit systems are assigned at the design stage of a project. After the design of the system has been finalized changes that can be implemented to improve the reliability are generally of the second order level and subsequently have a lesser effect. An area that has traditionally been a source of unreliable operation for railroad and transit systems has been the interfaces between the various systems. The system-to-system interfaces cover the whole of the range of areas in a railroad or transit system and are often visible to the passengers using the railroad or transit system. The interfaces to be controlled have a wide variety of characteristics and features. These interfaces can consist of mechanical issues like for the platform and vehicle interface. The interfaces can also be mainly electrical in nature as with the control of conducted interference currents at the vehicle power supply interface to achieve compatibility. Interfaces may also be a mixture of mechanical and electrical characteristics. Railroad and transit systems are becoming more sophisticated, it is now common for a rail vehicle to have multiple microprocessors on board to control the various systems needed for a modern rail vehicle. Similar technologies are also being applied to different systems of a railroad or transit system. For example the technology required to control a vehicle propulsion system is very similar to that required by the modern regenerative substation. Modern integrated systems are also spreading across the traditional system boundaries. For example an integrated passenger information system for an LRT or Metro system would span vehicles, stations, train control and communication systems. A key factor to improving the reliability of a railroad or transit system is early and effective control of the system interfaces and having the appropriate organization(s) responsible for the interface. This paper will explore the factors that would need to be considered for appropriate management of the interfaces. It will relate the management of the interfaces to the types of contract mechanisms that can be used for procurement of equipment and consider the associated advantages and risks.

Nonlinear Investigation of the Effect of Primary Suspension on the Hunting Stability of a Rail Wheelset

The mathematical model of a single railway wheelset moving with constant speed on a smooth, level, and tangential track is used to numerically investigate the nonlinear dynamics of the wheelset. Nonlinearities in the wheelset model include the nonlinear wheel-rail profile and the friction-creep characteristics of the wheel-rail contact geometry. Wheelset numerical simulations consider single-point and two-point wheel-rail contact scenarios. Sensitivity of the critical hunting velocity to primary stiffness and damping parameters is examined. Results of the lateral stability study indicate that the critical hunting velocity of the wheelset is most sensitive to the primary longitudinal and lateral stiffness. Methods involving semi-active and active control of the primary longitudinal stiffness are developed to raise the critical velocity of hunting. These approaches are seen to considerably increase the wheelset critical hunting velocity.

Computation and Validation of Rail-to-Earth Potential for Diode-Grounded DC Traction System at Taipei Rapid Transit System

In this paper we present a case study of frequent surges of unusually high rail-to-earth potential values at Taipei Rapid Transit System. The rail potential values observed and the resulting stray current flow associated with the diode-ground DC traction system during operation are contradictory to the moderate values on which the grounding of the DC traction system design was based. Thus we conducted both theoretical study and field measurements to obtain better understanding of the phenomenon, and to develop a more accurate algorithm for computing the rail-to-earth potential of the diode-ground DC traction systems.