scholarly journals Examination of Vehicle Performance at High Speed and High Cant Deficiency

Author(s):  
Brian Marquis ◽  
Jon LeBlanc ◽  
Ali Tajaddini

In the US, increasing passenger speeds to improve trip time usually involves increasing speeds through curves. Increasing speeds through curves will increase the lateral force exerted on track during curving, thus requiring more intensive track maintenance to maintain safety. These issues and other performance requirements including ride quality and vehicle stability, can be addressed through careful truck design. Existing high-speed rail equipment, and in particular their bogies, are better suited to track conditions in Europe or Japan, in which premium tracks with little curvature are dedicated for high-speed service. The Federal Railroad Administration has been conducting parametric simulation studies that examine the performance of rail vehicles at high speeds (greater than 90 mph) and at high cant deficiency (greater than 5 inches). The purpose of these analyses is to evaluate the performance of representative vehicle designs subject to different combinations of track geometry variations, such as short warp and alinement.

Author(s):  
Junghsen Lieh ◽  
Jie Yin

A symmetric wheelset with an elasto-damper coupling between the wheels is used to investigate the effect of coupling and primary stiffness and damping on the vehicle critical speed. Different suspension parameters are considered. Stability boundaries for various conditions are presented. The dynamic model of the elasto-damper–coupled wheelset is validated using published results. Both coupler and primary suspensions can dramatically affect the vehicle stability, and optimal parameters can be used to improve the vehicle performance over that of the conventional system.


2020 ◽  
Vol 12 (12) ◽  
pp. 168781402098468
Author(s):  
Xianbin Du ◽  
Youqun Zhao ◽  
Yijiang Ma ◽  
Hongxun Fu

The camber and cornering properties of the tire directly affect the handling stability of vehicles, especially in emergencies such as high-speed cornering and obstacle avoidance. The structural and load-bearing mode of non-pneumatic mechanical elastic (ME) wheel determine that the mechanical properties of ME wheel will change when different combinations of hinge length and distribution number are adopted. The camber and cornering properties of ME wheel with different hinge lengths and distributions were studied by combining finite element method (FEM) with neural network theory. A ME wheel back propagation (BP) neural network model was established, and the additional momentum method and adaptive learning rate method were utilized to improve BP algorithm. The learning ability and generalization ability of the network model were verified by comparing the output values with the actual input values. The camber and cornering properties of ME wheel were analyzed when the hinge length and distribution changed. The results showed the variation of lateral force and aligning torque of different wheel structures under the combined conditions, and also provided guidance for the matching of wheel and vehicle performance.


Author(s):  
Zai-Wei Li ◽  
Xiao-Zhou Liu ◽  
Hong-Yao Lu ◽  
Yue-Lei He

The deformation of longitudinally coupled prefabricated slab track (LCPST) due to high temperature may lead to a reduction in ride comfort and safety in high-speed rail (HSR) operation. It is thus critical to understand and track the development of such defects. This study develops an online monitoring system to analyze LCPST deformation at different slab depths under various temperatures. The trackside system, powered by solar energy with STM8L core that is ultra-low in energy consumption, is used to collect data of LCPST deformation and temperature level uninterruptedly. With canonical correlation analysis, it is found that LCPST deformation presents similar periodic variation to yearly temperature fluctuation and large longitudinal force may be generated as heat accumulates in summer, thereby causing track defects. Then the distribution of temperature and deformation data is categorized based on fuzzy c-means clustering. Through the distribution analysis, it is suggested that slab inspection can be shortened to 6 hours, i.e. from 10:00 am to 4:00 pm, reducing 14.3% track inspection workload from the current practice. The price of workload reduction is only a 2% chance of missed detection of slab deformation. The finding of this research can be used to enhance LCPST monitoring efficiency and reduce interruption to HSR operation, which is an essential step in promoting reliable and cost-effective track service.


Author(s):  
Fazilah Hassan ◽  
Argyrios Zolotas

AbstractAdvances in the use of fractional order calculus in control theory increasingly make their way into control applications such as in the process industry, electrical machines, mechatronics/robotics, albeit at a slower rate into control applications in automotive and railway systems. We present work on advances in high-speed rail vehicle tilt control design enabled by use of fractional order methods. Analytical problems in rail tilt control still exist especially on simplified tilt using non-precedent sensor information (rather than use of the more complex precedence (or preview) schemes). Challenges arise due to suspension dynamic interactions (due to strong coupling between roll and lateral dynamic modes) and the sensor measurement. We explore optimized PID-based non-precedent tilt control via both direct fractional-order PID design and via fractional-order based loop shaping that reduces effect of lags in the design model. The impact of fractional order design methods on tilt performance (track curve following vs ride quality) trade off is particularly emphasized. Simulation results illustrate superior benefit by utilizing fractional order-based tilt control design.


Author(s):  
Allan M. Zarembski ◽  
James Blaze ◽  
Pradeep Patel

What are some of the practical obstacles to a “shared interests” between a freight railway business and the proposed new higher speed passenger entity? This paper discusses the real “tension” between the two business interests that fund freight trains versus those that support and fund higher speed passenger trains as they attempt to share the same tracks in a safe manner. There are fundamental laws of physics that have to be addressed as the two different sets of equipment are “accommodated” on a shared corridor. This may not always be an easy accommodation between the two commercial parties. One real tension between the two commercial interests involves the physical problem of accommodating two radically different train sets on areas of curved track. For one example, what will be the passenger train required future higher speeds and how will these speeds be accommodated in existing main line tracks with curves varying from 1% to 6% in degrees? How much super elevation will need to be put back into the heretofore freight train tracks? How will the resulting super elevation affect the operation of so called drag or high tonnage slow speed bulk cargo trains? Accommodating such differences in train set types, axle loadings, freight versus passenger train set speeds, requires making detailed choices at the engineering level. These may be shared interests, but they are also variables with far different outcomes by design for the two different business types. The freight railways have spent the last few decades “taking the super elevation out” because it is not needed for the modern and highly efficient freight trains. Now the requirements of the passenger trains may need for it to be replaced. What are the dynamics and fundamental engineering principles at work here? Grade crossings have a safety issue set of interests that likely require such things as “quad” gates and for the highest passenger train speeds even complete grade separation. Track accommodating very high speed passenger trains requires under federal regulations much closer physical property tolerances in gauge width, track alignment, and surface profile. This in turn increases the level of track inspection and track maintenance expenses versus the standard freight operations in a corridor. Fundamentally, how is this all going to be allocated to the two different commercial train users? What will be the equally shared cost and what are examples of the solely allocated costs when a corridor has such different train users? In summary, this paper provides a description of these shared issues and the fundamental trade-offs that the parties must agree upon related to overall track design, track geometry, track curvature, super elevation options, allowed speeds in curves, more robust protection at grade crossings, and the manner in which these changes from the freight only corridors are to be allocated given the resulting much higher track maintenance costs of these to be shared assets.


Author(s):  
Jonathan M. Wnek ◽  
Steven M. Chrismer

One of Amtrak’s high-speed continuous action tampers has been fitted with TGCS (Track Geometry Control System) tamper control software to compare the quality and durability of geometry correction it provides with that of the existing tamper control system, AGGS. Comparison between the two systems is made by reviewing measured track geometry data from before and after maintenance, and by reviewing changes in ride quality accelerations of instrumented passenger cars. Although the testing program is in its early stages and the number of test locations so far is limited, results to date are very much in favor of TGCS.


Author(s):  
Giorgio Diana ◽  
Federico Cheli ◽  
Paolo Belforte ◽  
Ferruccio Resta ◽  
Michele Elia ◽  
...  

During 2005, the Italian railway Network Operator (RFI – Rete Ferroviaria Italiana) realized two ETR500 train sets completely dedicated to diagnostic operation on the new high speed lines being built in Italy. During 2006, these train were equipped with a complete acceleration measuring system for test activities on new Italian high speed line Turin – Novara and Rome – Neaples. A complete accelerometric measurement set up has been installed for track investigation. To this aim, the experimental set up is able to identify vertical profile of track geometry, without the limitation to 25 – 30 m, typical of the traditional measuring methods. On the other hand, a tool for predictive identification of hunting instability has been developed. For each run, it is possible to define a map, highlighting all the irregularity wavelengths involved as a function of the space: for high speed application wavelength over 100 m can become really important both for comfort and safety, because they are able to interest low frequency dynamic (around 0.8 – 1.5 Hz). Moreover, with the aim of identifying the beginning of hunting instability, a tool has been developed in order to identify yaw instability vibration mode and thus its non-dimensional damping, just by bogie yaw acceleration measurement. Both this tools have been developed by means of comparison between numerical multi body simulations and experimental measurements. Numerical simulation have been used to simulate a wide range of operating condition, that was of fundamental importance in tuning of such tools. Full evidence on these method will be given in the paper, together with an example of the obtained results.


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