Feasibility study of multifunctional electromagnetic damper for vibration control of cable and energy harvesting

Abstract

External loads, such as wind loads and vehicle loads, that continuously act on bridge cables cause fatigue loads on the cables. In addition, momentary loads, such as typhoons and earthquakes, cause excessive vibration on the cable. In order to prevent excessive vibration of the cable and maintain the cable, proper vibration control and monitoring measures are necessary. Currently, various types of vibration control devices are used for vibration control of cable, and wireless sensors are used for monitoring the cable. However, most of the devices are operated as a separate system, and it is very inefficient to install a vibration control device for an external load, such as a typhoon or an earthquake, which occurs extremely rare. In this study, an electromagnetic damper with functions of vibration control and energy harvesting was proposed for an efficient maintenance method of cable structure. The electromagnetic damper based on the electromagnetic induction principle can utilize the electric energy and the damping force generated in the damper as the vibration control of the cable and the power of the wireless sensor. In this study, the electromagnetic damper with optimum volume efficiency was designed by using an experimental design method. Based on the designed electromagnetic damper, the electromagnetic damper with optimal volume density was fabricated and the characteristic test was conducted. As a result of the characteristic test, the electromagnetic damper showed a linear change with respect to the external amplitude and showed a nonlinear change with respect to the frequency change. As the external resistance increased, the maximum control force of the damper gradually decreased. Hybrid simulation and laboratory scale experiments were performed to evaluate the feasibility of the electromagnetic damper. The vibration control performance and the energy harvesting performance of the electromagnetic damper were evaluated through hybrid simulation for virtual cable structure. For the 20 m length cable, the hybrid test results showed that the vibration reduction performance was about 50% and energy harvesting performance was enough to operate the wireless sensor. The vibration control performance of the damper was verified for the footbridge cable. As a result of the free vibration and forced vibration test, the electromagnetic damper effectively increased the vibration attenuation performance. Based on the test results, the operational plan of the electromagnetic damper by using the meteorological data measured near the 2nd Jindo bridge was proposed. Based on the measured wind speed data in 2016, the operational plan of the electromagnetic was presented for each wind speed and the operational possibility of the wireless senor was evaluated by using the energy harvesting performance.