Design of coupled piezoelectric-electromagnetic energy harvester and energy collecting tests

A coupled piezoelectric-electromagnetic energy harvester was designed, the expression of output power was derived by the electromechanical couplingstate equations. The output characteristics of piezoelectric, electromagnetic and coupled piezoelectric-electromagnetic energy harvesters were compared through experimental tests.The results show that the 3 dB bandwidth of the coupled piezoelectric-electromagnetic energy harvester was increased by 67% and 25% compared with piezoelectric and electromagnetic energy harvesters, respectively, resulting in an increase of 38% and 118% in maximum output power respectively. The energy collecting circuit of coupled piezoelectric-electromagnetic energy harvester was designed.The electric energy converted from piezoelectric energy-harvesting unit and electromagnetic energy-harvesting unit were collected by LTC3588 and LTC3108 chips separately, and then stored in a super-capacitor. The charge tests of super-capacitor were conducted using three energy harvesters separately. It is indicated that the charge time of coupled piezoelectric-electromagnetic energy harvester was decreased by 29% and 52% compared with piezoelectric and electromagnetic energy harvesters, respectively.