Monique Stewart

CHALLENGES IN CURRENT WIRELESS SENSOR TECHNOLOGY FOR RAILCAR STATUS MONITORING FOR NORTH AMERICA'S FREIGHT RAILROAD INDUSTRY

Ensuring rail safety is a priority for the Federal Railroad Administration (FRA) and the railroad industry in North America. One such endeavor is to leverage Wireless Sensor Networks (WSN) to monitor and report in real-time the status of mechanical and electrical components for each railcar, and in conjunction with other railroad subsystems, ensure the safety, security and integrity of transported goods.The envisioned solution utilizes sensors installed on each railcar to form a train-based wireless network and collect real-time (or near real-time) information on different elements of a train and transmit aggregated information to the locomotive, dispatch centers or regional offices for early fault detection and accident prevention. The railroads have been interested in using a standards-based low-cost communication protocol for this purpose, such as IEEE 802.15.4, often referred to as ZigBee.Our results show, however, that ZigBee was designed for smaller wireless networks, such as a single railcar. It exhibits several critical problems associated with the unique network topology found on a freight train and the size of such a network. In essence, the network would take the shape of a very long chain of nodes. Some of the problems stemming from this topology are excessively long synchronization delays for establishing the network along the entire train, severe problems with route discovery and maintenance necessary for selecting the next relay node along the chain, aggregation of data errors and a resulting unacceptable packet loss rate, the lack of a traffic prioritization mechanism to protect important packets such as those containing critical alarms of equipment failure, and many more.In this paper, we describe our findings and experiences in our evaluation of ZigBee for railcar monitoring onboard freight trains, a detailed analysis of the identified problems and their impact on the envisioned railcar monitoring as well as discuss potential solutions to these problems.Copyright

Hybrid Technology Networking: A Novel Wireless Networking Approach for Real-Time Railcar Status Monitoring

The North American freight railroad industry continuously strives towards improvements in the safety and security of freight transportation. One key effort focuses on the use of Wireless Sensor Networks (WSN) technologies to monitor and report mechanical and electrical component status for each railcar in real-time, as well as the status of the transported goods themselves. This allows real-time monitoring of railcar components such as air pressure, wheel bearing temperature, brake failure, wiring integrity, refrigeration unit failure, boxcar door opening, the detection of radioactive materials, dangerous substance leaks, and much more. The aggregated sensor data is transmitted to the locomotive, dispatch centers or regional offices for early fault detection and accident prevention.Our previous work [1] has shown that ZigBee technology based on the IEEE 802.15.4 faces numerous obstacles when applied to freight railcar monitoring. To address these problems our team proposed an alternate approach called Hybrid Technology Networking (HTN), which combines the benefits of ZigBee for low-power short-range communication and WiFi for high-performance long-distance communication between HTN sensor clusters.In this paper, we present our simulation results using our HTN protocol. We compare and discuss the performance of the ZigBee-only network environment with the proposed HTN and demonstrate the advantages offered by HTN. We also discuss our prototype sensor hardware platform using the HTN protocol and provide an outlook of the future work planned for HTN.© 2012 ASME

Train Energy and Dynamics Simulator (TEDS): A State-of-the-Art Longitudinal Train Dynamics Simulator

Train safety and operational efficiency are enhanced by the ability to understand the behavior of trains under varying conditions. Under the direction of the Federal Railroad Administration (FRA), a longitudinal train dynamics and operation simulation software — Train Energy and Dynamics Simulator (TEDS) — has been developed. TEDS is capable of modeling modern train operations and equipment, and is an effective tool for studying train operations safety and performance as affected by equipment, train makeup, train handling, track conditions, operating practices and environmental conditions.TEDS simulates the dynamics of longitudinal train action and incorporates the dynamic effects of various different types of draft gears and end-of-car cushioning units including mismatched devices coupled together, the transient response of locomotive tractive and dynamic braking effort, as well as a fluid dynamic representation of the air brake system with the capability to model conventional pneumatic and ECP brake systems.The capabilities of TEDS are described and demonstrated with several examples. The validation effort undertaken is described at both the component and system level. Comparisons of TEDS simulations of impact tests with the test results are shown to verify the draft gear and end-of-car cushioning unit models. The air brake model predictions are verified by comparing brake rack test results to TEDS simulations of braking behavior.Copyright

Performance Evaluation of Hybrid Technology Networking for Real-Time Monitoring in Freight Railroad Operations

Traditional Wireless Sensor Network (WSN) solutions have been deemed insufficient to address the requirements of freight railroad companies to implement real-time monitoring and control of their trains, tracks and wayside equipment. With only ZigBee-based elements, the transmission capabilities of WSN devices are limited in terms of coverage range and throughput. This leads to severe delay and congestion in the network, particularly in railroad scenarios that usually require the nodes to be arranged in linear chain-like topology. In such a multi-hop topology to communicate from one end of a train to the locomotive — and due to ZigBee’s limited communication range — data needs to be transmitted using a very high number of hops and thus generates long delays and congestion problems.To overcome this drawback, we have proposed a heterogeneous multi-hop networking approach called “Hybrid Technology Networking” (HTN). In HTN we combined Wireless Local Area Network (WLAN) technologies like WiFi, which provide improved communication range and higher data rates, with low-power communication technologies like ZigBee. This significantly reduces the number of hops required to deliver data across the network and hence solves the issues of delay and congestion, while also achieving superior enery efficiency and network lifetime. The sensor nodes are logically divided into clusters and each cluster has a WiFi “gateway”. All intra-cluster communication is achieved via IEEE 802.15.4 and ZigBee protocols, while all inter-cluster communication utilizes WiFi protocol standards.To implement our proposed technology in railroad networks, we are designing hardware prototypes and simulation models to evaluate the functionality and performance of our HTN solution, which is designed around a dual network stack design governed by the HTN protocol. This ensures full compliance with IEEE and industry communication protocols for interoperability. Since no simulation tools that seamlessly combine both WSN and WLAN technologies in a single module exist, we wrote our own simulation environment using OPNET. In this paper, we have provided information of implementing the HTN protocol in OPNET and the simulation results for different scenarios relevant to railroad operations. These results will demonstrate the efficacy of our proposed system as well as provide the baseline data for testing the hardware devices in live networks. Under simulated traffic and channel conditions and device configurations, we observed a decrease of 77.27% in end-to-end delay and an increase of 69.70% in received data volume when using HTN compared to ZigBee-only multi-hop networks, simulated over 14 railcars in railroad-relevant scenarios.Copyright

Performance modeling of a multi-tier multi-hop hybrid sensor network protocol

The North American railroad industry, with the objective of improving safety and security of their operations, have been exploring the possibilities of real-time monitoring and control of trains and wayside equipment. Wireless Sensor Networks (WSNs) have emerged as the de-facto solution for most measurement and monitoring operations. However, widely used commercial WSN solutions, like ZigBee, exhibit significant delay and traffic congestion problems due to their limited range, throughput and overall capabilities. To overcome this problem we proposed a multi-tier multi-hop heterogeneous network technology, called Hybrid Technology Networking (HTN). HTN is comprised of sensors equipped with multiple complementary radio technologies in which the sensors form a cluster and communicate within their own cluster using low-power communication. Each clusters gateway then utilizes WiFi or similar longer range technologies for inter-cluster communication. In this paper, we present the design of our HTN node representation in OPNET. Furthermore, we present a theoretical framework that accurately models the delay in the network and verify the model with simulation results. We also present relevant results that demonstrate its full functionality, and also explore the efficacy of such hybrid multi-tier multi-hop implementations.

Energy Analysis in Deploying Wireless Sensor Networks for On-Board Real-Time Railcar Status Monitoring

Wireless Sensor Networks have been a focus of research in the North American freight railroad industry to enable on-board real-time sensing of critical railcar parameters. Important railcar aspects like wheel bearing temperature, air pressure, brake failure, and the integrity of transported goods can then be monitored closely and reliably. This enables immediate preventive actions in case of impending failures and also enables trend analysis that can be used to fine-tune maintenance efforts on railcars. These measures increase the safety, efficiency, and dependability of freight railroad operations.In our previous work [1–3] we have presented our Hybrid Technology Networking (HTN) protocol. This protocol provides optimal network performance for railcar monitoring applications. We have also presented HTNMote, a hardware prototyping platform that implements HTN. A deployment of HTNMotes was conducted and evaluated at the TTCI facility in Pueblo, Colorado in the US. The results from our field tests confirm that this approach is an order of magnitude better in performance compared to solutions based on ZigBee alone.In such an application, energy considerations represent a key challenge. These sensors have no readily available continuous energy source, but are expected to operate for years in harsh conditions. Energy harvesting — from vibrations, temperature differences, or solar radiation — may provide a potential solution to the energy scarcity. This also mandates that the HTNMote hardware and HTN protocol both be as energy efficient as possible.In this paper we present detailed measurements of the energy consumed by the HTNMote in various operational situations that are encountered during their operation onboard freight railcars. We introduce an energy consumption model based on our analysis of the measurements. This model demonstrates the energy-efficiency of the HTNMote implementation.© 2015 ASME

HTNMote: A Hardware Platform for Wireless Real-Time Railcar Monitoring and its Performance Analysis

Real-time monitoring of various components of a railcar such as wheel bearing temperature, brake line status, integrity of transported goods and many more has become a key focus area of research for the North American freight railroad industry. The ability for timely detection of abnormalities and impending failures prevents costly accidents, the potential loss of life and damage to the environment. Monitoring also increases overall operational efficiency, reliability and safety of freight railroads.Wireless Sensor Networks (WSN) are an obvious choice for implementing such a monitoring scheme. The accumulated data from various sensors distributed throughout each railcar along the length of the train is transmitted wirelessly using multi-hop transmissions to the locomotive for alerting and monitoring. From there, this information is also transmitted to dispatch centers for further analysis and recording. ZigBee technology based on the IEEE 802.15.4 standard is a popular choice among WSN communication protocols, owing to its low cost and low power requirements. ZigBee performance degrades severely in the long chain-like topology characteristic of the railroad application environment. This effectively disqualifies ZigBee as a candidate technology for such railcar monitoring deployments.To overcome these issues with ZigBee deployments for freight train monitoring we developed our Hybrid Technology Networking (HTN) approach [5–7]. HTN leverages both ZigBee and Wi-Fi communication to achieve reliable communication along an entire freight train. Railcar monitoring nodes are grouped into smaller clusters, within which we utilize ZigBee for its low-power operation and report to each cluster’s gateway node. The gateway nodes of all the clusters on a train communicate using Wi-Fi, to benefit from the high throughput and long communication range. This tiered architecture also results in a drastic reduction in overall hop count for end-to-end communication.In this paper we present HTNMote, a hardware platform that we are developing and employing for real-world evaluation of the HTN protocol. We also present results from our field tests of the HTNMotes at the Transportation Technology Center (TTCI) facility in Pueblo, Colorado, operated by the US Association of American Railroads (AAR). The results show that the use of HTN improves performance of the network by at least an order of magnitude compared to a ZigBee-only network. This paper details the design of our HTNMote platform, present the test setup and results, as well as conduct an in-depth analysis of the obtained results as they relate to railroad operations.© 2014 ASME

Performance of an on-board monitoring system in a revenue service demonstration

The Office of Research and Development of the Federal Railroad Administration (FRA) is sponsoring a revenue service demonstration of an on-board condition monitoring system for freight trains. The objective of the system is to improve railroad safety and efficiency through continuous monitoring of mechanical components to detect defects before they cause breakdowns and accidents. The project, which commenced in June 1999, is part of the Rolling Stock Program Element in FRAs Five-Year Strategic Plan for Railroad Research, Development and Demonstrations (March 2002). Science Applications International Corporation (SAIC) and Wilcoxon Research (WR) developed the prototype system in 2000. It was installed on a test vehicle provided by the Research and Tests Department at Norfolk Southern Corporation and was tested during the period Nov. 2000-Nov. 2001. In fall 2003 the monitoring system was installed on five hopper cars provided by Southern Company Services and is currently being tested in revenue service operation on a coal train operating on a Norfolk Southern route in Alabama between a coalmine northwest of Birmingham and Gaston Steam Plant in Wilsonville, AL. In this paper we discuss the performance of the monitoring system during the revenue service demonstration. The potential benefits of the technology are also addressed.

Revenue Service Demonstration of On-Board Condition Monitoring System

The Office of Research and Development of the Federal Railroad Administration (FRA) is sponsoring a project to develop and demonstrate an on-board condition monitoring system for freight trains. The objective of the system is to improve railroad safety and efficiency through continuous monitoring of mechanical components in order to detect defects before they cause breakdowns and accidents. The project, which commenced in June 1999, is part of the Rolling Stock Program Element in FRA’s Five-Year Strategic Plan for Railroad Research, Development and Demonstrations [1]. Science Applications International Corporation (SAIC) and Wilcoxon Research (WR) designed and developed a prototype system in 2000. The prototype system was tested during the period Nov. 2000–Nov. 2001 on a vehicle provided by the Research and Tests Department at Norfolk Southern Corporation. A Revenue Service Demonstration is scheduled to commence in October 2003. The monitoring system will be installed on five coal hopper cars and tested in revenue service. Southern Company Service is providing the test cars. The train will operate on a Norfolk Southern line between a coalmine near Berry, AL and an electric power plant, located 35 miles southeast of Birmingham. The demonstration is scheduled to run for six months. The demonstration will showcase some of the latest technologies in wireless communications and railroad bearings. A tri-mode cell telephone will be used for data telemetry between the on-board monitoring system and a web-accessible database. The Timken Company has developed two innovative systems that will be deployed in the demonstration — a permanent magnet generator mounted inside a Class F railroad bearing and bearing health monitoring system featuring temperature and vibration sensors, a tachometer, a micro-controller and an RF transmitter mounted inside a Class F bearing.Copyright

Wheel Temperature Reduction During Freight Car Braking

Since the adoption of 286,000 lb gross rail load (286K GRL) car service, an increase in wheel thermal damage and shelling has been observed. This is attributed to the increased braking horsepower in 286K GRL service as compared to the 263K GRL service environment. This study investigated possible designs and methods of braking that could lead to reduced heat input to the tread of freight car wheels in order to mitigate this damage and reduce its occurrence to a level closer to that seen with 263K GRL car service.Fifteen potential concepts to lower the thermal input to wheels and/or accelerate heat removal from the tread were identified and evaluated using the following engineering categories: simplicity of design, maintenance requirements, weight considerations, material and manufacturing costs, controllability of braking effort, and market acceptability. Five final concepts — axle-mounted disc, cheek disc, wheel rim, axle-mounted drum, and high convection coating — were developed through preliminary design and thermal analysis to confirm their effectiveness in meeting the objectives.Four concepts for alternative braking methods — axle-mounted disc brakes, cheek disc brakes, wheel rim clasp brakes, and axle-mounted drum brakes — were analyzed in considerable detail. Of the four concepts presented, the first three appear to be feasible and would be potential candidates for further detailed investigations/evaluation.It is shown that as the demand on railway wheels to withstand increased mechanical and thermal loads grows, there are viable braking enhancements that can help manage the stress state in freight car wheels.Copyright