A STUDY ON THE WIRELESS MONITORING SYSTEM FOR THE RAILROAD VEHICIE MAINTENANCE USING THE ENERGY HARVESTING TECHNOLOGY

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1 A STUDY ON THE WIRELESS MONITORING SYSTEM FOR THE RAILROAD VEHICIE MAINTENANCE USING THE ENERGY HARVESTING TECHNOLOGY Jaehoon Kim 1), Jae-Yun Lee 2), Keun-Young Kim 3) 1) Korea Railroad Research Institute, Phone: , 2) The Graduate School of Mechanical Engineering, Sogang Univ., 3) Korea Railroad Research Institute, Phone: , Abstract: Advanced high speed railroad system requires absolute improvement of the reliability and safety of both the train and passengers and increase in cost for system maintenance has been emerged as another challenge. Thus it s necessary to develop the technologies that will satisfy the needs in two different aspects, dubbed as reliability & safety and maintenance cost. To that end, development of intelligent railroad system including rolling stock is more than important. Intellectualization of railroad system is based on development of constant real-time detection technology which requires Information Technology-integrated intelligent monitoring system. In general, monitoring system is needed for constant monitoring which enables to detect abnormal symptom of the system and take preventive measures or counter measures before emergency situation. And to maintain such a constant monitoring, it s necessary to identify the symptom by analyzing the information using the sensor which functions to convert the physical symptom into electrical signal. However, existing railroad monitoring system usually adopts wire sensor and the need for using monitoring system with wireless sensor that enables to monitor the parts of the bogie or driving system or the system inaccessible in the vehicle has been on the rise. Thus, this study was researched the existing railroad monitoring system and, for using monitoring system with wireless sensor, this study also was intended to identify the applicability of energy harvesting technologies which is regarded the new and renewable energy for monitoring the intelligent railroad system. Keywards: Railroad, Maintenance, Monitoring, Energy Harvesting 1. Introduction Due to the global warming and depletion of fossil fuel, all governments and industries are aiming for 'Low Carbon and Green Growth' as the vision and promotion direction by nation in the future, and especially the expectation and need for railroad system as green means of transportation for mass transportation are emerging rapidly. This means that it is necessary that the transport system need to be reorganized with the environment-friendly railroad as a center to be able to solve the huge societal cost problems and usage of coal energy by road traffic. But, the rapid system is an essential condition to accomplish low carbon and green growth project of traffic system, which is a continuous challenge. The rapid railroad system requires the absolute improvement of reliability and safety of passengers and trains, and the increased cost of system maintenance for this is emerging as another problem. Therefore, the effort of new technique development to meet the reliability and safety according to rapid railroad system and maintenance cost, and the intelligent railroad system of trains must be performed in advance for this. And, the basis of intelligent railroad system lies on the development of continuous real-time detection technique, and the establishment of intelligent monitoring system which IT technique is included in is necessary. Generally, the monitoring system is also necessary to find, prevent, and cope with the risk in advance. And, it is available to analyze the phenomenon through the analysis of information using censor which converts the physical transition to electric signal for continuous monitoring. But, the requirement for wire censor monitoring system is increasing which is generally used in monitoring system of railroad until now, and recently the system which uses units which operate on driving device and replacement railroad vehicle and wireless censor which is used despite the limitation 530

2 of installment and place. Especially, the application of wireless censor and IT technique to railroad monitoring system makes it possible to maintain on the basis of real-time monitoring during driving, differentiating itself from previous periodic dismantling and inspection, and this fact can increase reliability and safety when driving railroad vehicle [1]. In this research, we analyzed the requirements of intelligent monitoring system which IT technique is included in through examination of monitoring system applied to current railroad system, performed the research of vibration characteristic which occurs under the precise driving environment of railroad vehicle to implement and design the driving technique of Energy harvesting as the power source of new regeneration energy. 2. Results and Discussion 2.1 The monitoring system for the railroad system The techniques which are applied to railroad system are described in Table 1. As table 1, the monitoring system is distinguished with on-ground and on-train according to the application, and it can be departmentalized as per the applied area and physical data of measurement. On-ground monitoring system detects the condition of axle bearing, wheel, weight, etc of the driving train which is equipped with the censor which non-contact typed infrared temperature sensor, sound wave censor, optical fiber, etc are used in [2-5]. The purpose of On-train monitoring system is to overcome the limitation of real-time measurement which occurs in previous on-ground typed monitoring system commonly, and this system is installed on train for monitoring directly on real-time. Actually in Europe, the monitoring regulation for the condition of train is established for on-train monitoring [5], and the real-time on-train monitoring system which wired censor is embedded in is being developed and tested in the company related to train and part suppliers [7-8]. Also, in case of some railroad management company, on-train real-time monitoring system is being researched to detect the abnormal temperature and heat condition of axle bearing in real-time during driving by installing wireless module which is operated by battery, and the real-time monitoring system by installing battery typed wireless censor is being researched in case of tank car and freight car which is difficult to provide with power source [9-10]. But, the additional work such as battery exchange due to the long-time usage and wiring limitation and maintenance cost will increase in case of wired censor or battery module which is applied to on-train monitoring system. Especially, the increase ratio of battery energy density cannot meet the real amount consumed, and the periodic battery exchange is required in case of long-time or real-time monitoring for railroad system. Therefore, the driving technique of "Energy harvesting" which provides monitoring system with power source by using neighboring energy such as vibration, heat, etc which occur when train is driving to solve these problems recently. As we examine the advanced research related to this, the brake status monitoring system is being developed by using vibration energy which is generated during driving as a measure of piezo-electric energy harvester [11]. Also, the monitoring system by connecting vibration energy electric magnetic typed energy harvester with wireless censor network is being developed [12]. And, through the trend of monitoring technique of railroad system and the investigation of applied technique, the basic requirements for intelligence railroad monitoring is as following. First, it is available to measure the target which needs monitoring in real-time. For this, it must be monitored by installing directly around the target area or on train which is possible to monitor directly. Second, the wireless network technique for remote measuring and monitoring is required. Through this, it is possible to overcome the installation limitation of previous wired censor monitoring system, and also available to integrate monitoring system and multiple censor breaking from previous individual monitoring. Third, the Energy harvesting technique is required to satisfy above two requirements such as semi-permanent lifespan, install limitation and improvement of maintenance task [9, 13]. Energy harvesting technique can overcome the limitation of lifespan according to the supply of external power source or previous battery, and it is expected that the complex problems can be solved such as install limitation of monitoring as per the driving power supply and improvement of maintenance task. 531

3 Table 1. The monitoring system for the railroad system Installation location Monitoring subject Measurement factor Ground type On board type Axle box bearing condition wheel condition Axle alignment Axle box bearing condition TSI bogie hunting detection Traction motor condition Cardan shaft condition Gearbox Wheel Derailment brake shoe, brake beam temperature, sound wave vibration, load temperature, vibration vibration, load load 2.2 Vibration measuring test of driving EMU train As described above, Energy harvesting technique is essential for real-time railroad system monitoring, and we performed a research of vibration characteristics from correct driving environment of train for energy harvesting through measurement in real driving EMU train to implement and design energy harvesting technique, the power source of new regeneration which is made electrically from driving train for real-time railroad monitoring system. We measured the energy source around the train through the real driving test in the back and forth section which many people moves on in commuting time in case of train test. At this time, we considered the vibration energy which is generated from the truck between rail and train as measurement with the "truck" as a center. Therefore, we measured the acceleration value of vibration acceleration censor (dual axis acceleration censor, Model: ADXL278, 5 mm x 5 mm x 2 mm ceramic package, g-ranges of ±50g/±50g), which is generated by the contact between rail and wheel when the train is driving, wirelessly without attenuation by installing in axle bearing as above Figure 1. At this time, we selected and tested the measurable train in morning commuting time when passengers are most crowded in. Fig. 1. The acceleration sensor on the axle box * Location of sensor installation (Axle bearing) 532

4 Fig. 2. The vibration acceleration on the operation (up: one way, down: return way) Fig. 3. The FFT result of vibratory acceleration. 2.2 Measuring testing result of vibration of driving train We measured the vibration acceleration through the Bluetooth communication wireless measuring system (Frequency range: 2.4 GHz ISM Band, Support Bluetooth Profile: GAP, SPP, Input Power: 3.3V, Communication distance: 100m) suitable for train. As described in Figure 2 of the measuring result, the driving characteristic of vibration acceleration from train axle bearing was measured in the whole driving section (= means between stations), and especially the change of vibration acceleration on the weighted section was measured very correctly. And, in the result of analysis, we found that the maximum value of vibration acceleration of axle bearing when train is driving in the whole section is generated over ±30g according to the section. Especially the vibration acceleration result is controlled to maximum limit since the damage from abrasion and desquamation was removed after regular maintenance task. Therefore, as very large vibration acceleration was measured when train is driving in low speed as Figure 2, we decided that the value will increase more than the result of this research in case of high speed train and weighted train according to circumstances. We also performed FFT analysis for vibration acceleration of train's moving between stations as Figure 3. At this time, the up-line section of round-trip section is marked as blue color, and down-line section as red color. The maximum value of vibration acceleration is a very important design element which decides the power generation efficiency of energy harvesting module in Energy harvesting monitoring system using vibration, and generally many researches are being performed for optimized efficiency of energy harvesting [14-17]. First of all, we performed the analysis of frequency and FFT for the section which vibration value is measured maximally of the operation section between the stations as Figure 4~5 in this research. At this result, the rms value of vibration acceleration in this section is analyzed as 0.78g, and the value of vibration acceleration is g at 76.58Hz in case of FFT result. However, as a result of FFT analysis which is performed in the whole operation section, the maximum value of train's acceleration is different according to operation section in case of train, and also the maximum value of vibration acceleration is different as described in Figure 3 as it is difficult to decide another specific maximum value for maximum efficiency of power generation. In this research, it is confirmed that the maximum values of vibration acceleration are distributed from 30 to 100 Hz according to section of whole section which train is being operated. Therefore, in case of train it is thought that the Energy Harvesting Module which is designed to generate optimized power over large bandwidth is more effective than to use specific maximum value which is considered generally. 533

5 Fig. 5. The vibration acc. on the Max. section Fig. 6. The FFT result on the Max. section Generally, the energy harvesting module which uses resonance mode is measured at the fixed frequency. And, the higher the Q factor of material or system, the more advantageous it is to deliver energy well in case of fixed frequency. It is because high power value can be obtained if the frequencies of Exciting Vibration Forces and resonance point are equal. The value of Q factor is decided by the frequency bandwidth which is 3 db lower than maximum peak value. But, the effectiveness will be low in case of energy harvesting module which is designed with specific maximum frequency if the frequency movement is frequent because the frequency bandwidth is small as the value of Q factor is high. Considering Q factor, it is decided that the system which the bandwidth is largely used in is more suitable even if the value of Q factor is low at the aspect of the driving environment of train. And, it is necessary to check performing additional research to develop energy harvesting module for train in the future. 3. Results and Discussion We performed the investigation of monitoring system which is applied to current railroad system and the research of vibration characteristic which occurs under correct driving environment of train which is really driving and characteristic of energy harvesting module, and obtained following results in this research. 1) The basic requirements for intelligent railroad system monitoring are as following. First, it must be possible to check the target which demands monitoring in real-time. Second, it requires wireless network technique for monitoring and remote-measurement. Third, it demands Energy harvesting technique to satisfy above two requirements such as improvement of maintenance task and install limitation, semipermanent lifespan, etc. 2) As a result of FFT analysis which is performed in the whole operation section, the maximum value of train's acceleration is different according to operation section in case of train, and also the maximum value of vibration acceleration is different. In this research, it is confirmed that the maximum values of vibration acceleration are distributed from 30 to 100 Hz according to section of whole section which train is being operated. Therefore, in case of train it is thought that the Energy Harvesting Module which is designed to generate optimized power over large bandwidth is more effective than to use specific maximum value which is considered generally. 4. References [1] International Railway Journal. May 2009 [2] GALLAGHER CORNELIUS (1987) Railroad Hot Box Detector, US (A) [3] Australian Rail Track Corporation (ARTC) [4] WID Inc. [5] Lloyd s Resister [6] European Technical Specification for Interoperability (TSI) Directive 96/48 EC [7] NTN_SNR 534

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