Electromagnetic micropower generation - system design and analyses

There has been a huge reduction in size and power consumption of MEMS devices like transducers and sensors. These devices are usually designed to run on batteries. The limited lifespan of batteries may induce costly maintenance, in the case of contaminated areas for instance. That led to a surge of research in the area of energy harvesting. Sustainable power generation may be achieved in converting ambient energy into electrical energy. Since mechanical vibrations exist in most systems, many works focused on vibration-driven generators. In this field, the electromagnetic induction is well suited for the mechanical to electrical energy conversion. The design of the mechanical system that transmits the surrounding vibratory energy to the electromagnetic generator is a critical importance. This thesis presents an optimization of an electromagnetic microgenerator. It describes the theory, design and simulation of an energy converter based on electromagnetic induction. The objectives of this research are designing, improving the performance and operational reliability of electromagnetic microgenerator. These have been achieved by identifying the desirable design features of the electromagnetic microgenerator. Extensive analytical investigation has been conducted to develop an efficient design of an electromagnetic microgenerator. An analytical model is developed. Numerical analyses using Mat Lab software investigate the optimum design parameters to get maximum power output. This thesis deals with the design and simulation of a number of flat springs to be used for supporting the moving magnet of an electromagnetic microgenerator. The flat spring and moving magnet are equivalent to a basic spring-mass system, in which the moving magnet is attached to a platform suspended by four beams. These flat springs were designed by modelling and finite element method simulation using ANSYS 5.7. A series of structural and vibration analyses were carried out using ANSYS to evaluate the flat spring characteristics and to choose the desirable mode of vibration. Finite element method is also used for the analysis, evaluation and optimization of the electromagnetic design of the electromagnetic microgenerator. The objectives behind this analysis are to characterize the permanent magnet and to investigate the optimum position of the coil relative to the magnet. Output power is estimated using the ANSYS simulation results of the magnetic field induced on the coil. It is also found that the magnetic field of the permanent magnet in the vertical direction is higher in magnitude than the magnetic field in the horizontal direction. Estimated power was calculated for different distance between the coil and the permanent magnet. The methodology and findings in this research provided a number of contributing elements to the field of MEMS power generation, and provided an insight into the development of an electromagnetic microgenerator. This thesis is concluded with a discussion on the performance of the proposed electromagnetic microgenerator and suggestions for further research