Research On An Arbitrary-directional Nonlinear Broadband Piezoelectric Vibration Energy Harvesting Method And System Based On Parallel Mechanism

In recent two decades,with the continuous and rapid development of microelectronics technology and wireless sensor network technology,the power of electronic circuits can be reduced to the microwatt level,making it possible to harvest energy from environmental energy vibration and convert it into electricity for power supply.Vibration energy harvesting has become a hot topic in the research of wireless sensor networks and micro-electromechanical systems.The existing vibration energy harvester can only harvest vibration energy in a narrow frequency band along a single sensitive axial direction,resulting in low energy collection efficiency and difficult to be applied in practice.In this paper,research on an arbitrary-directional nonlinear broadband piezoelectric vibration energy method and system are proposed and studied based on parallel mechanisms,arbitrary-direction vibration energy collection is realized by using 3 degree of freedom parallel mechanism,and broadband vibration energy harvester is realized by introducing nonlinear magnetic force into magnet.Specific carried out the following aspects of work:(1)In order to realize the broadband vibration energy harvesting,the mechanical resonance characteristics of the vibration energy harvester are changed by the interaction between magnets,so that the vibration energy harvester can achieve relatively large amplitude and energy output in a wide frequency band.According to the established mathematical model,The amplitude-frequency response characteristics of single degree of freedom nonlinear piezoelectric vibration energy harvester under different initial gaps,different amplitude excitation and different load conditions are analyzed by simulation;A single degree of freedom nonlinear piezoelectric vibration energy harvester is developed and designed,and and tested experimentally.The experimental test results show that the developed single degree of freedom nonlinear piezoelectric vibration energy harvester has broadband characteristics.(2)In order to achieve arbitrary-direction broadband vibration energy harvesting,the single degree of freedom nonlinear piezoelectric vibration energy harvester is combined with the structure of Delta parallel mechanism to form an arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester.The principle and structure of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester are studied;Based on the kinematics equation,the kinetic energy function,the potential energy function,the piezoelectric residual energy function,the dissipative function and the Lagrange equation,the state matrix equation of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester is derived,and the mathematical model is established by the state matrix equation.According to the established model,the simulation analysis of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester working mode and different initial gaps,the amplitude frequency response characteristics under different excitation amplitude,and the trajectories of the inertial mass under different initial clearance.(3)According to the established mathematical model of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester,the simulation analysis under different structure parameters of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester of the amplitude frequency response characteristics.On this basis,A prototype of arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester is developed and designed.In addition,the three-channel energy harvesting circuit design,and the circuit simulation analyzed.(4)In order to verify the effectiveness and correctness of the proposed arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester.Established experimental device of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester.Using the established experimental device,firstly,the amplitude-frequency response characteristics of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester under the excitation of x _B,y _B,z _B and other directions are tested;Secondly,the amplitude-frequency response and hopping characteristics of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester under different initial gaps are tested;Thirdly,the amplitude-frequency response characteristics of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester under different acceleration sweep excitation are tested;Then,the optimal output power of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester under load is tested;Finally,under strong nonlinearity,the voltage output characteristics of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester moving between potential Wells in any direction under different acceleration excitation are tested.Experimental results show that,the vibration energy harvester can achieve arbitrary-direction broadband,when the nonlinearity is weak,the maximum average power under the sweep excitation of 1.0g is 22.3 m W,which is almost 2.2 times that of the linear system,and the broadband of the large-amplitude periodic vibration can be extended to about 5.5 Hz,and the central frequency is about 11 Hz;When the nonlinearity is strong,the vibration energy harvester will have 8 potential Wells in the three-dimensional space,and under proper excitation,chaotic motion and periodic vibration with large values will be generated.Therefore,in most cases,the nonlinearity of the proposed arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester is moderate.In a certain range,with the increase of nonlinearity,the operating broadband increases and the resonant frequency decreases.However,when the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester is strongly nonlinear,the resonant frequency may increase and the energy harvesting efficiency may decrease under low level excitation.The research results in this paper can provide a design basis and reference for the future design of the arbitrary-directional nonlinear broadband piezoelectric vibration energy harvester.