Mechanical Modeling and Numerical Investigation of Earthquake-Induced Structural Vibration Self-Powered Sensing Device

Earthquake-induced structural vibration is converted into an instant voltage signal via piezoelectric (PZT) material for sensing purposes where it can be detected and read by a self-powered/self-sensing capabilities' sensor located in remote and inaccessible areas. The motivating sensor is expected to wirelessly transmit vital information for monitoring purposes. A typical earthquake's acceleration frequency components' range is as low as 1 to 17 Hz. Therefore, the motivating sensor is designed to resonate at its fundamental mode shapes to generate a readable voltage signal and power enough to meet the minimum power consumption needs of a typical acceleration sensor. The proposed sensor consists of a stack of 17 individual uniform simply supported composite-PZT beams with a proof mass in the mid-span of each beam. The proof mass is utilized to enhance the voltage signal and lower the device's natural frequencies. The genetic algorithm (GA)-based optimization method is employed to optimize the first natural frequency of the {n} th beam of the proposed sensing device to match it with one of a typical earthquake ground excitation frequencies at an increment of 1 Hz. The fundamental mode is the most sensitive mode to the proof mass. Furthermore, the difference between the higher natural frequencies decreases when increasing the size of the proof mass. The analytical and decoupled electromechanical equations are presented by employing the assumptions of Euler-Bernoulli's thin beam hypothesis. The analytical results are then numerically verified by FEM by employing COMSOL multiphysics software to model and numerically simulate the proposed device/sensor.