In recent years, there has been a surge of interest in scavenging the mechanical energy from the ambient vibration induced by environmental disturbance. In the field of civil engineering, the potential of using this harvested power to supply the power demand of small consuming devices, like sensors, gave researchers the motivation to explore this area. Among all harvesting techniques Piezoelectric and Electromagnetic methods are the most popular methods. However, for low frequency vibration sources (e.g. civil engineering structures) Electromagnetic (EM) conversion mechanism is shown to produce a higher harvested power.

On the other hand, in a more common application, EM transducers have been used for the structural vibration control as actuators in active control systems, or a...[ Read more ]

In recent years, there has been a surge of interest in scavenging the mechanical energy from the ambient vibration induced by environmental disturbance. In the field of civil engineering, the potential of using this harvested power to supply the power demand of small consuming devices, like sensors, gave researchers the motivation to explore this area. Among all harvesting techniques Piezoelectric and Electromagnetic methods are the most popular methods. However, for low frequency vibration sources (e.g. civil engineering structures) Electromagnetic (EM) conversion mechanism is shown to produce a higher harvested power.

On the other hand, in a more common application, EM transducers have been used for the structural vibration control as actuators in active control systems, or adjustable dampers in passive and semi-active control schemes. Therefore, the incorporation of adaptive EM damping and energy harvesting makes it possible to develop smart regenerative dampers. In this study, the main focus is the development of such control systems for vibration control of civil engineering structures. In that regard, a new self-powered hybrid electromagnetic damper is proposed that can harvest energy while mitigating the vibration of a structure by switching between two separate modes, namely passive energy harvesting and semi-active modes. The harvested energy stored in the battery during the passive mode is employed to power up the monitoring and electronic components necessary for the semi-active control.

It is shown that in comparison with the other regenerative semi-active dampers, the new design increases the feasible force-velocity region that is available to the damper. This gives more flexibility to the damper to tackle the vibration more effectively. Besides, since the harvested power is random by nature, it is possible that the available energy is less than the operational requirement of the system. In that case, the damper can switch back to the passive mode, thus, energy outage does not negatively affect the control performance of the system.

In the first part, the device mechanism and the circuitry that can drive this self-powered electromagnetic damper are described. The parameters that determine the constitutive force-velocity relation of the damper are identified and discussed. Next, a prototype of the damper is designed and tested under different harmonic excitations. The mechanical and electrical characteristics of both passive and semi-active modes were investigated and verified. The average harvested power and current were measured, and the efficiency of different parts of the damper is determined.

Afterward, the effectiveness of the hybrid damper is evaluated through numerical simulation study on vibration mitigation of a bridge stay cable under wind excitation. It is demonstrated that the proposed hybrid design outperforms the conventional passive damper without external power supply. It is also shown that a broader force range, facilitated by decoupled passive and semi-active modes, can improve the vibration performance of the cable.

In the last part, the control algorithm that is used to realize the semi-active control is considered. As it was observed in the experiments, the total force exerted by the EM damper comprises a parasitic nonlinear force in addition to the electromagnetic force. Tuning the semi-active mode, without considering the nonlinear effect could compromise the performance of the damper. To address this issue, a sliding mode based controller is developed that aims to track the response of a closed-loop optimal system.

The potential of this algorithm for control of a single degree of freedom structure under base excitation is investigated. It is demonstrated, through both numerical simulation and experimental tests, that by knowing the bound of the nonlinear parasitic force in advance, the semi-active mode is able to track the response of an optimal structure, and it outperforms the conventional clipped-optimal control. This algorithm gives the damper a better performance in practical applications.