ASSIGNMENT HELP ON ENERGY HARVESTING FROM RAIL TRACK FOR TRANSPORTATION SAFETY AND MONITORING

INTRODUCTION

Rail transportation systems, including freight train, commuter rail and subways, play an important role in peoples daily life and also provide substantial supports for the economy. Track-side electric infrastructures are essential for the operation of modern railroad systems. To make informed decisions and provide safe quality service, railroad systems rely on track side electric infrastructures. Warning and signal lights, track switches, grade crossing signals, track-health monitoring systems, wireless communication access points, positive train control systems, and etc. reliable and low maintenance power supplies are essential prerequisites.

Unfortunately, rail road tracks often exist in remote areas or certain underground regions in which there is little electrical infrastructure. In these regions, instalment of equipment such as warning signal lights, wireless sensors for railway track monitoring, bridge monitoring, and train positioning have limited practical deployment due to the lack of a reliable power supply or low-maintenance battery. Some regions still only use rail road crossing signs at grade crossings and do not implement flashing lights, moving gates, or whistles. In response to the growing need for electronically powered track side devices, it is worthwhile to design a cost-effective and reliable power supply solution for track-side devices.In rural areas like Hisar in Harayana there have been deaths due to unmanned railway crossing. According to the records of the Indian Railways, there are 31,846 railway level crossings across the country, of which 13,530 are either unmanned or without barriers.The number of accidents has shown a downward trend since 2000−01 when 473 accidents were reported at unmanned crossings. But the number of deaths has only gone up from 216, including eight railway officials, in 2000−01 to 319, including 17 railway officials, 2011−12. In 2012− 13 (till November 12,2012) total 168 people, including four railway staff, were killed at unmanned railway crossings, revealed the RTI reply.

When a moving train passes over the track, the track deflects vertically responding to the load exerted by the trains boogies. The majority of currently existing railway energy harvesting technologies utilizes the peak valley nature of the motion and focusing on piezoelectric and electromagnetic harvesters. Many of these technologies harvest energy in the milliwatt or sub watt range, largely for wireless sensor applications. The technologies include: tuned vibrational harvesters , coils that induce induction currents through passing wheels , and basic piezoelectric and electromagnetic solutions.

1.1 Literature survey
The conventional direct-motion-driven electromagnetic vibration energy harvesting system is typically composed of: an element for mechanical input motion conversion (rack and pinion, ball screw, or hydraulic piston), a motion magnification element (gears, levers, hydraulics, etc.), an electromagnetic generator, electrical rectifier, power regulator, and energy storage element [2-3]. These designs may be extended for railroad harvesting applications, but simple retrofit of these energy harvesting technologies however will result in low efficiency energy conversion and poor output quality due to the pulse like nature and low amplitude of displacement of the track.The simple rack and pinion harvester Nelson et al created illustrated these issues [3]. When dealing with irregular pulse-like inputs, an electromagnetic generator will be driven at an erratic range of speeds resulting in less efficient operation and power output of low quality. An oscillating input such as from the train track can also introduce large impact forces within the device when the track switches direction of motion, which contributes to component fatigue and wear.

In [4] a motion conversion based energy harvester was developed , consisting of a bidirectional to unidirectional motion conversion mechanism and a flywheel. The flywheel helped address the issue of having a pulse-like input. It allowed the electromagnetic generator to operate over a more consistent range of speeds. This improves generator operating efficiency and also eliminates pulse-like characteristics in the power output. By stabilizing the power output, conversion of electrical output power becomes a more efficient process. Maintenance of generator and component speeds furthermore helps improve harvester component lifetime by reducing the cyclic loading of pulse like forces. In this investigation, a prototype was developed that harvested up to 1.4 W with 10-25% mechanical efficiency. Simulations were conducted using 1Hz frequency at 3mm displacement.

1.2 Objective
(a) Design and development of MMR
(b) Design of suitable circuit for storing energy
(c) Track monitoring

1.3 Outline of the report
Working principle and design methodology of energy harvester is described in chapter 2. Chapter 3 describing components of battery charging circuit and it’s working. Application of energy harvester is described in chapter 4 followed by result and conclusion of the project.

VIBRATION ENERGY

HARVESTER

2.1 Components of energy harvester
The updated MMR harvester system can be described by its two major halves. The first half is input assembly, which acts to convert bi-directional linear motion into single directional rotational motion. The input assembly consists of two rack and pinions, and two roller clutches. The roller clutches are fitted into the two pinions, either of them engage input shaft at a single direction. The next half of the energy harvester consists of the gearhead, power generator, and flywheel. These components are tasked to condition the unidirectional rotational motion and then convert the motion into useful energy.
Input assembly consists of 2 linearly guided gear racks , 2 mounted

Figure 2.1: Block diagram of vibration energy harvester bearings, 2 pinion gears meshed with the racks, 2 unidirectional roller clutches which are fitted into the pinions, and a shafts fitting in between the roller clutches. Mounted bearings support the shaft, a flexible coupling is used, friction reducing washes separate rotating components from static environments. The output assembly consists of an electric generator, a gearhead, flywheel and various mounting brackets. All of the aforementioned components are mounted onto a metal plate. Flexible couplings are used throughout the design. For mounting onto the railroad track, the gear racks are anchored into the ballast material while the rest of the components on the harvester base plate are mounted over the track ties.

2.2 Working of energy harvester
The racks transmit vertical up and down motion to the two pinions. The rack pinion assembly causes the two pinion gears to rotate in opposite directions with respect to one another. The pinions are fitted with unidirectional roller clutches. The roller clutches, engage the shaft only when rotating in a specific direction of rotation. In either direction of rack motion, one of the pinions will engage the input shaft and the other pinion will disengage it. By installing both roller clutches to engage the input shaft in the same direction, the shaft moves in a unidirectional motion.

The unidirectional rotational input motion is then fed to a generator gear head, which amplifies the low speed input of the pinion shaft to optimal generator speed values. The electric generator thus spins in unidirectional
motion at its efficient operating speeds. Electrical power will be produced from the electric generator as it spins. It is important to note that the input shaft may also coast, or spin freely. In this case, both pinions disengage. This is a crucial feature for flywheel implementation. The generator contains an output shaft in which a flywheel is installed. This flywheel stores kinetic energy through spinning. The flywheel is designed to lend its kinetic energy to the generator when there is no input motion from the track. Moments in which there is no input motion to the gear racks occur in between bogies. During these moments, the generator is powered by the flywheel, allowing for generation of consistent continuous voltage output.