Integration of shock absorption and energy harvesting using a hydraulic rectifier

Hydraulic shock absorbers have been widely used to dissipate kinetic energy of the shocks into surrounding environment. By employing oscillatory motion to drive power generator, the shock energy can be converted into electricity for harvesting. However, the frequent bidirectional oscillation of the generator can cause a large impact force. This further leads to deteriorated energy harvesting performance, moving parts fatigue, and even system failure. As such, this study introduces four check values to form a hydraulic rectifier to integrate the shock absorption and energy harvesting functionalities. The bidirectional oscillation of the shock and the vibration is converted into unidirectional rotation to drive the generator. Following the proposed concept, a prototype energy-harvesting shock absorber has been designed and fabricated. An electromechanical model has also been developed to examine the response behavior of the prototype device. The prototype performance has been characterized based on the experimental results from three test setups. Both mechanical and electrical parameters of the electromechanical model have been identified based on our cyclic loading experiments. The results have shown that the developed energy-harvesting shock absorber is capable of harvesting the energy and absorbing the shock simultaneously. In our experiments, a maximum of 248.8 W instantaneous power (a maximum of 114.1 W on average) has been captured and a maximum of 38.81% energy harvesting efficiency has been achieved via harmonic excitation with an amplitude of 8 mm and a frequency of 2 Hz, when the load resistance is tuned to 7.5 Ω.