The Design And Optimization Of Nonlinear Circuit Of Piezoelectric Energy Harvesting System For Broadband Vibration

How to power continuously wireless sensor network nodes(WSNs)has been a quite difficult technical problem,which has seriously restrained the development and application of embedded WSNs.Piezoelectric energy harvesting from environmental vibrations has been an extremely potential way to solve this problem.However,Frequency bandwidths of environmental vibrations are broad in many cases.Therefore,it is urgent to design and optimize nonlinear energy harvesting circuits to increase the efficiency.At present,most researches on energy harvesting circuits are independent of piezoelectric generators and coupling effects between them are neglected.However,the coupling effects indeed impact the efficiency of a piezoelectric energy harvesting system.Hence,it is very valuable to design and optimize nonlinear energy harvesting circuits from the perspective of a whole system.The parallel synchronized switch harvesting on inductor(P-SSHI)circuit is a promising way to realize broadband piezoelectric vibration energy harvesting.But its conversion efficiency depends greatly on the voltage across the rectified capacitor.To solve this problem,this paper proposes a modified P-SSHI circuit with controllable optimal voltage(COV-PSSHI).Then two coupled models for piezoelectric energy harvesting system are built.Simulations are done on the coupled models and parameter optimizations are achieved.Finally,experiments are carried out to verify the theoretical and simulation results.The main contents and conclusions are as follows:1.An improved COV-PSSHI circuit is designed to overcome the drawback that the conversion efficiency of conventional P-SSHI circuit depends on the voltage across the rectified capacitor.Then the theoretical model of the COV-PSSHI circuit is built and circuit simulations are conducted.The results demonstrate that the harvested power of a COV-PSSHI circuit is much larger than that of a P-SSHI circuit.2.An equivalent circuit model for piezoelectric generator is built and a solution algorithm for the circuit model parameters is proposed.Based on them,a system-level coupled circuit model of the piezoelectric energy harvesting system is built.Then the equivalent impedance of the COV-PSSHI circuit is derived.Then it is used as the electrical load to build the system-level finite element coupled model of the piezoelectric energy harvesting system.3.The effects of vibration exciting frequency and load on the harvested power of the piezoelectric energy harvesting system are simulated for both system-level coupled models.Moreover,an overall optimization of key parameters in the circuit is conducted based on the coupled circuit model.4.Two experimental rigs are designed and built for vibration and rotating energy harvesting,respectively.Then broadband performance of the COV-PSSHI circuit is tested under broadband vibrations.The results show that the harvested power of the COV-PSSHI circuit is much larger than that of P-SSHI circuit under the same input of broadband vibrations or rotating motions.