چكيده به لاتين
Energy is a key factor in the modern smart world. Energy harvesters can provide electrical power for Health Monitoring (HM) sensors, Automatic train operation (ATO), switches, and safety equipment. Therefore, Energy Harvesting from ambient vibration due to the increasing demand for alternative energy sources has attracted very much concentration in the railway industry. Because of the limitation in electric power in freight wagons and high-cost batteries, building an energy harvesting system is a priority.
In this thesis, first, the basics of energy harvesting from the vibration energy by use of piezoelectric transducers, electromagnetic, and triboelectric are discussed. Then, a conceptual design for piezoelectric transducers is presented which works based on the vibrational energy caused by track irregularities. The model of the energy harvester is a cantilever beam resonator that is mounted to the axle box of freight wagons. In this regard, the fright wagon with 18-100 bogie is simulated in Universal Mechanism (UM) software. The vibration of the axel box is measured by an accelerometer element under different track irregularities, and speeds. Track irregularity is one of the most common defects in the railway industry, which is created by wheel-rail friction, wheel flat, Environmental factors, etc. The track irregularities are generated and considered in the simulation according to UIC standards. Power Spectral Density (PSD) of acceleration is calculated and applied to the cantilever beam as the input excitation. The model of energy harvester is simulated by use of COMSOL software and a random analysis is executed for the model. Then, the performance of the Energy Harvesting system under different track irregularities, load conditions, and speeds is investigated. Finally, several harvesting samples are fabricated and tested under random excitation to verify numerical results.
The novel idea of using Auxetic structures is employed to increase the rate of power conversion by simply changing the structure of the beam and without the need to change the geometry of the piezoelectric element or change the material. Auxetic structures with a Negative Poisson ratio are among the metamaterials that have attracted considerable interest in recent decades. The introduction of new auxetic structures and using them in the present energy harvesting system has shown a 2.4-time enhancement in power compared to a simple structure.
