Research On Adaptive Mechano-electronic Switching Structure Of Piezoelectric Energy Harvesting

With the development of low power electronic technology,wireless sensor networks have been widely promoted.Using energy harvesting technology to supply power to wireless sensor networks is one of the key technologies to accelerate the practical development of wireless sensor networks.Piezoelectric materials possess the advantages of high energy density and easy integration thus they are widely used in the field of energy harvesting.The energy extraction efficiency of the energy extraction circuit is directly related to the output power of the system.Based on the parallel synchronous switching harvesting on inductor(SSHI),an energy extraction circuit with adaptive mechanical synchronous switching is proposed in this paper.The piezoelectric energy harvesting device can be installed on the engine or suspension of the vehicle to harvest the vibration energy during the driving process of the vehicle.The harvested electric energy can supply power to the wireless sensor module,and send the collected signal to the on-board computer to realize the monitoring of the running condition of the engine and suspension.The on-board computer can analyze the working state of the engine and suspension according to the vibration signal,find out the factors that are not conducive to the driving safety in time and feedback,which can effectively improve the safety of the vehicle.The energy harvesting efficiency of this circuit is pretty high,the output is stable and this circuit is self-adaptive in environmental vibration.The main contributions are listed as following:(1)Firstly,the principle of electromechanical energy conversion for piezoelectric energy generation with cantilever beam is introduced.On this basis,the working principles of standard energy harvesting circuit(SEH),synchronous electric charge extraction circuit(SECE),series synchronous switching harvesting on inductor(Series-SSHI)and parallel synchronous switching harvesting on inductor(Parallel-SSHI)are explained.Then,based on the advantages of P-SSHI in piezoelectric energy harvesting of cantilever beam,two kinds of mechanical synchronous switches which are self-adaptive for the amplitude of the piezoelectric cantilever are proposed.These two kinds of mechanical synchronous switches use low frequency cantilever beam and memory sponge with longer relaxation time as moving electrodes of mechanical synchronous switches respectively.They overcome the shortcomings of the former electronic synchronous switches without additional electricity consumption.(2)The mechanical dynamics simulation and electromechanical coupling simulation analysis of the extraction circuit of these two kinds of mechanical synchronous switches were carried out by using MATLAB,and the adaptive performance of the mechanical switches under noise was especially verified.The simulation results confirm the correctness of the adaptive method proposed in this paper.Then two experimental platforms are built according to the design.The load power values of the circuit under the conditions of different displacement amplitude and excitation frequencies are measured and compared along with the simulation results.It shows that the experiment matches well with the simulation,which proves the accuracy of the experimental platform.(3)Based on the experimental platform the experimental results of two mechanical synchronous switch extraction circuits and standard circuit under the conditions of various excitation frequencies,various displacement amplitude and constant acceleration value have been measured.It is found that the maximum power ratio of the cantilever beam adaptive peak detection mechanical synchronous switching circuit and standard circuit can reach 375% under the condition of constant acceleration value,while the maximum power ratio of adaptive memory foam mechanical synchronous switching circuit and standard circuit is 292.3%.Based on the same energy extraction circuit under the condition of constant acceleration value,the load power of the adaptive memory sponge mechanical synchronous switch can increase by 98% higher than the case with electronic synchronous switches.(4)Finally,the parameters of the system are optimized by the dynamic model.It is found that the energy extraction efficiency of the adaptive mechanical synchronous switch circuit can be further improved through the corresponding structural design improvements.