Nonlinear Dynamic Characteristics And Mechanism Investigation Of Rotational Motion Energy Harvesting

With the continue development of Artificial Internet of Things(AIoT),embedded-based Artificial Internet of Things system are used widely to monitor the operation condition of the various rotational machines.However,the limited life of the power supply batteries leads to the high maintenance workload,even the application functions are also limited.Hence,the vibration energy harvesting technology,which can obtain energies from the ambinent environment to supply power for low-power Artificial Internet of Things sensing systems,has become a current research hot topic.To overcome the problems of both poor environmental adaptability and single kinematic characteristics for the traditional vibration energy harvesting systems,the nonlinear dynamic characteristics and mechanism investigation of the rotational motion energy harvesting are in-depthly investigated in this study.The major contents of this study are summared as follows:(1)Aiming to the problem of the narrow operation frequency bandwidth and low energy conversin efficiency of linear rotational energy harvesting system,the combined beam-type energy harvesting structure is designed,and the dynamc design method of magneticed coupling bistable rotational motion energy harvesting is proposed.Based on the energy method of Hamilton’s principle,the electromechanical coupling dynamic model of the bistable rotational motion energy harvesting system is established.The form mechanism of the bistable rotational motion energy harvesting system is revealed under the guidance of the static bifurcation,and the influence of the gravity effect on the static bifurcation characteristics of the bistable rotational energy harvesting system is explored.The research results indicate that the proposed combined energy harvesting structure has more uniform strain distributions,the spanwise strain of the combined beam is larger 64.3%than that of the conventional rectangular beam under the same conditions,the combined beam-type bistabel rotational energy harvesting structure has a more superior electric output performances in the range of from 300 rpm to 550 rpm,and the maximum RMS output voltage is 9.44 V at the rotational speed of 540 rpm that the maximum improvement percentage is 13.8%.(2)Due to the the nonlinear bistable energy harvesting system is difficult to maintain high-energy motion orbit under the low rotational motion excitation level,the nonlinear tristable rotational motion energy harvesting mechanism is proposed to improve the enevironmental robustness of the nonlinear bistable rotational enegy harvesting system.Based on the Hamilton’s principle,the comprehensive electromechanical coupling dynamic model of the tristable rotational energy harvesting system is developed by taking the geometrical nonlinear effect and nonlinear rotational frequency into consideration,and the influence mechanism of the geometrical nonlinear effect and nonlinear rotational frequency on the characteristics of the nonlinear tristable rotational motion energy harvesting system are explored.The nonlinear tristable rotational energy harvesting is conducive to generate inter-well snap-through motion and output large-amplitude voltage under low rotational motion excitation lever.The tristable rotational energy harvesting system has more superior wide-band energy harvesting characteristics than the bistable system.This study.provides a theoretical framework for the design of.highperformance rotational motion energy harvesting system.(3)The nonlinear rotational energy harvesting system is difficult to achieve high-energy periodic orbit motion in the range of multiple solution regions and the lower accuracy of nonlinear magnetic force calculation model,the dynamic synergistic regulation mechanism of the multistable rotational motion energy harvesting system is proposed,and the modified accurate magnetic force model is derived by taking the relative displacement and rotational angle into consideration.The synergistic transition mechanism of different oscillation states for the multistable rotational motion energy harvesting system is revealed under the guidance of the static bifurcation,potential energy analysis,and dynamic behaviors.Numerical and experimental results show that the developed theoretical model can accurately characterize multistable rotational energy harvesting system with richer dynamics,and the rotational motion energy harvesting efficiency is dramatically improved.This study provides a new method for improving comprehensive characteristics of rotational motion energy harvester.(4)To solve the problems of the lower energy harvesting efficiency under the condition of the ultra-low-frequency rotational motion,the dynamic regulation method of the stiffness softness is proposed.Based on the Euler-Bernoulli beam theory,assumed boundary conditions,and extended Hamilton’s principle,the comprehensive electromechanical coupling dynamic model is established,the frequency response functions of the output displacement and voltage are obtained,the linear asymptote models of the output voltage are developed and the closedform analytical models of the optimum electrical load resistance corresponding to the maximum power output are extracted for the extreme conditions of short-circuit and open-circuit.The influence of the position of electrode,mass of mass block,and position of mass block on the output electric performances of the ultra-lowfrequency rotational energy harvestering system are investigated.Meanwhile,a simple identification method of optimal electrical load resistance is proposed in the absence case of experimental testing devices,and the predicted accuracy of the proposed method is verified using experiments.