Modeling and simulation of a flat spring for use in an electromagnetic microgenerator

The ability to supply power at the micro level from the ambient energy is an increasingly important area of MEMS. This paper presents a methodology for the design of an electromagnetic micro generator that converts mechanical energy associated with the low amplitude vibration present in structures such us tall buildings and bridges to electrical power. The generator consists of a rigid housing and a moving magnet suspended on a flat spring that induces a voltage on a stationary coil attached to the housing. Finite Element Analysis (FEA) software (ANSYS5.7) has been used to analyse different designs of flat springs and to select one that is capable of large deflection. The effects of the main design parameters: length, width, thickness and material properties on the spring deflection were modelled. Maximum static deflection of 13.43μm is achieved under the gravitational force. Furthermore, Free vibration characteristics of the suspended magnet are also presented. Maximum electric power of 14.5nW is calculated for the spring with natural frequency of 18.56 Hz when the input vibration frequency and its amplitude are assumed to be 3kHz and 5μm. An outline of how the design can proceed in a logical manner is discussed.