| The rapid development of science and technology had increased the requirements for scattered power supply in the industrial Internet such as microelectronic monitoring and wireless sensor systems.This requirement had further promoted the research of vibration energy recovery systems with smart materials such as piezoelectric and giant magnetostriction as the core components.However,the energy recovery systems only had the high energy recovery efficiency near its resonant frequency and the energy recovery efficiency decreased significantly after deviating from the resonant frequency due to the variability and extensiveness of the environmental vibration frequency.In order to solve the problem,this thesis starts with the optimization of the transducer structure,studies the dynamic equation of the transducer under a certain load state.On this basis,the theoretical model of the energy recovery of the transducer is established and the frequency-extension research is carried out.The energy recovery system can be further modulated by introducing time-delay feedback control for the frequency-extension.The main research contents are as follows:(1)The characteristics and performance advantages of the giant magnetostrictive material are introduced in order to optimize the output characteristics of the giant magnetostrictive transducer and improve the electromechanical coupling coefficient of the transducer.The optimization of the transducer structure is carried out in three aspects: the addition of the bias magnetic field,the setting of the prestress and the design of the closed magnetic circuit,which lay the theoretical foundation for the later research on the output characteristics of the transducer and the frequency extension of the energy recovery system.(2)The dynamic model of the transducer under a certain load state is established.The dynamic equation of the transducer under the load is deduced through the strain equation of the transducer,the second domain switch model,the Jiles-Atherton model,the Newton’s second and third laws.The simulation found that the output of the transducer is the hard nonlinear.The influence of the external excitation force,stiffness coefficient and damping coefficient of the transducer on the nonlinear characteristics of the system’s output are further analyzed.(3)The external circuit is added to the transducer on the basis of the nonlinear characteristics of the transducer’s output.The energy recovery theoretical model of the transducer under a certain load is established.The amplitude-frequency characteristic equation of the system is solved.The frequency bandwidth of the induced voltage on the resistor is greater than 0.2 V as the effective bandwidth,the influence of the output nonlinear characteristics on the effective bandwidth and induced voltage peak value of energy recovery is studied by comparing with the transducer with linear output characteristics.At the same time,the effects of the system’s cubic stiffness coefficient,damping coefficient,primary stiffness coefficient and system mass on the output bandwidth and induced voltage of the energy recovery system are analyzed.(4)In order to adjust the frequency range of the energy recovery system of the transducer,time-delay feedback controls are introduced for the transducer.The nonlinear characteristics of the transducer’s output under the time-delay feedback of displacement,velocity and acceleration are studied.The transducer controlled by the time-delay feedback of displacemen and velocity have the positive effect on reducing the output displacement and improving the stability of the system.These transducers can be applied to the vibration isolation systems.The transducer controlled by the time-delay feedback of acceleration can change the system’s resonance frequency without changing the output displacement.Finally,the transducer with acceleration time-delay feedback control is applied to the energy recovery system,the output of the energy recovery system is further studied. |
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