S.L. Ho

A Fiber Bragg Grating Sensor System for Train Axle Counting

Railway signaling facilitates two main functions, namely, train detection and train control, in order to maintain safe separations among the trains. Track circuits are the most commonly used train detection means with the simple open/close circuit principles; and subsequent adoption of axle counters further allows the detection of trains under adverse track conditions. However, with electrification and power electronics traction drive systems, aggravated by the electromagnetic interference in the vicinity of the signaling system, railway engineers often find unstable or even faulty operations of track circuits and axle counting systems, which inevitably jeopardizes the safe operation of trains. A new means of train detection, which is completely free from electromagnetic interference, is therefore required for the modern railway signaling system. This paper presents a novel optical fiber sensor signaling system. The sensor operation, field setup, axle detection solution set, and test results of an installation in a trial system on a busy suburban railway line are given.

Real-Time Train Wheel Condition Monitoring by Fiber Bragg Grating Sensors

Wheel defects on trains, such as flat wheels and out-of-roundness, inevitably jeopardize the safety of railway operations. Regular visual inspection and checking by experienced workers are the commonly adopted practice to identify wheel defects. However, the defects may not be spotted in time. Therefore, an automatic, remote-sensing, reliable, and accurate monitoring system for wheel condition is always desirable. The paper describes a real-time system to monitor wheel defects based on fiber Bragg grating sensors. Track strain response upon wheel-rail interaction is measured and processed to generate a condition index which directly reflects the wheel condition. This approach is verified by extensive field test, and the preliminary results show that this electromagnetic-immune system provides an effective alternative for wheel defects detection. The system significantly increases the efficiency of maintenance management and reduces the cost for defects detection, and more importantly, avoids derailment timely.

Development of a Fiber-Optic Sensing System for Train Vibration and Train Weight Measurements in Hong Kong

A novel operation system to detect train vibration and train weight using FBG sensing network has been designed and tested in Hong Kong. The purpose of the system is for real time condition monitoring of trains. Because of the fast response of optical systems, the trains can be monitored in real-time during its normal service without any special arrangement. Hence, the condition checking can be realized without any disruption on the operating condition of the railway system.

Development of Level Sensors Based on Fiber Bragg Grating for Railway Track Differential Settlement Measurement

This paper describes the development of a liquid level sensor based on a fiber Bragg grating (FBG) written in 80-μm diameter optical fiber for railway track differential settlement measurement. The FBG embedded in the sensor is affixed to a float installed inside the liquid-filled sensor body, which measures the upthrust force induced by the float in response to the variations of liquid level. The level measurement and the temperature operation range of the sensor are 0-22 mm and -30°C to 80°C, respectively. Experimental results show that the sensitivity of the sensor is 0.107 nm/mm, which matches well with the designed value.

Wireless Condition Monitoring of Train Traction Systems Using Magnetoelectric Passive Current Sensors

Novel power-supply-free, surface-mount-type magnetoelectric passive current sensors were developed and integrated with a four-channel, 2.4-GHz wireless communication (transmitter and receiver) unit to form a new generation of wireless condition monitor for train traction systems. The wireless condition monitor was deployed in a field study on the East Rail Line in Hong Kong. Four pairs of magnetoelectric passive current sensors and single-channel wireless transmitters were installed, respectively, on and near the electric cables of four electric motor drives located underneath the 2nd, 5th, 8th, and 11th cars of a 12-car mainline train. The four-channel wireless receiver was housed in the drivers cab of the train to provide real-time wireless monitoring of the current signatures of the four electric motor drives due to the operation of the train traction system in steady-state and acceleration conditions. The monitored current signatures were post-processed to obtain the distributions of the ratio of harmonic-to-fundamental current, their total harmonic distortions and power factors as well as the frequency spectra. A practical implication and correlation of the post-processed data with the operating conditions of the train traction system was established for application of the proposed wireless condition monitor as train traction system monitor.

A CAN Network for Temperature Monitoring of Car Engine and Train Bogie

Controller Area Network (CAN) technology is adopted by most automation industries, especially in automotive industry nowadays. This paper introduces a built network for data CAN transmission after the data acquisition (DAQ) from the required temperature sensors mounted on a car engine and a train bogie in two respective tests. Lab VIEW is the only applied software throughout this network design based upon the industrial widely use. The network should be able to be applied in various transportation industries due to its flexibility, extensibility and feasibility.

Fiber Bragg Grating Sensors for Railway Systems

Fiber Bragg grating (FBG) sensor technology has been attracting substantial industrial interests for the last decade. FBG sensors have seen increasing acceptance and widespread use for structural sensing and health monitoring applications in composites, civil engineering, aerospace, marine, oil & gas, and smart structures. One transportation system that has been benefitted tremendously from this technology is railways, where it is of the utmost importance to understand the structural and operating conditions of rails as well as that of freight and passenger service cars to ensure safe and reliable operation. Fiberoptic sensors, mostly in the form of FBGs, offer various important characteristics, such as EMI/RFI immunity, multiplexing capability, and very long-range interrogation (up to 230 km between FBGs and measurement unit), over the conventional electrical sensors for the distinctive operational conditions in railways. FBG sensors are unique from other types of fiber-optic sensors as the measured information is wavelength-encoded, which provides self-referencing and renders their signals less susceptible to intensity fluctuations. In addition, FBGs are reflective sensors that can be interrogated from either end, providing redundancy to FBG sensing networks. These two unique features are particularly important for the railway industry where safe and reliable operations are the major concerns. Furthermore, FBGs are very versatile and transducers based on FBGs can be designed to measure a wide range of parameters such as acceleration and inclination. Consequently, a single interrogator can deal with a large number of FBG sensors to measure a multitude of parameters at different locations that spans over a large area.

Monitoring of Mission Critical Components of Railways Using Smart Railway System

Smart Railway System uses smart sensors (FBG, magneto-electric or piezoelectric) to monitor selected parameters of mission critical components of the railway on a real time basis. Through the diagnostic and decision support modules of the system early warning would be issued to the duty controller so that pre-emptive actions could be taken to avoid major incidents when developing faults are detected. Components monitored include running gear of trains (wheel-sets, axle box, primary suspension etc.), turnouts, track irregularities, point machines, TVS fans, etc. The warnings are structured on the 3A principle (Alert, Alarm and Action) so that simple procedures could be followed by the duty controller. Maintenance staff could also download signal analysis results from the diagnostic module to trace and analyze the fault. The system would also facilitate the adoption of a predictive maintenance regime for mission critical components of the railway. doi: 10.12783/SHM2015/260

Application of WPT and FBG techniques for prognostic of escalator abnormality: a case study of degraded step wheel

This study explores the adoption of fibre Bragg grating (FBG) strain sensor for in situ condition monitoring of the interaction between the step wheels and rail of escalator system. Time and frequency domain signal-processing techniques are proposed to extract the useful signatures from the measurements collected by the FBG sensors. It is shown that these signatures can be used accurately to provide crucial information of the escalator condition such as passenger loading of steps as well as abnormal vibration induced by component defects of the escalator system. These information are important as they give real-time information of the dynamic behaviour of an operating escalator and hence the monitoring system can also be used as a tool to enhance the safety and maintainability of escalators. Discussions on the results as well as technical issues to be addressed for the scheme in practice are given.

A Virtual Control System for Automotive and Railway Industries

The paper presents a virtual instrument based control system for research and development of the automotive and railway industries. This creative, low cost, efficient, and practical system contains the applications of data acquisition, controller area network (CAN), harmful engine exhaust emissions reduction, and spot welding. The system should be able to be employed in various automation industries due to its flexibility.