| At present,the country attaches great importance to the development of new energy.Ultrasonic vibration energy,as a new energy,widely exists in the natural environment and industrial production in the form of sound wave.However,due to its complex research mechanism,most piezoelectric ultrasonic transducers have a single functional design,which is only suitable for some specific scenes,and it is easy to make the whole electromechanical system collapse due to device failure.Therefore,compared with single-function devices,multifunctional devices have higher stability and broader application background,which can greatly reduce the influence of device failure on the whole MEMS and ensure the continuous operation of MEMS.However,because multifunctional devices contain multiple functions and need a variety of different principles to realize their different functions,the complexity is greater.In this regard,this paper designs a new multifunctional piezoelectric ultrasonic transducer based on the principle of piezoelectric effect,which integrates ultrasonic vibration energy conversion and mechanical transmission,so that the mechanical or electronic equipment equipped with the device has the function of energy consumption reduction and conversion,reducing its own consumption or providing energy for other low-power devices.It greatly improves the life cycle of the whole MEMS system and the ability to adapt to various environments.And on the basis of the principle of piezoelectric effect,the electromagnetic rotary energy acquisition is designed to achieve a variety of energy acquisition integration,increase the power supply for other devices,the main research content of this paper includes:(1)A multifunctional piezoelectric ultrasonic transducer is designed.Firstly,the inverse piezoelectric effect of piezoelectric ceramics is used to convert electric energy into mechanical energy to realize mechanical transmission.Secondly,the positive piezoelectric effect of piezoelectric ceramics is used to convert the energy of ultrasonic vibration into electric energy,which can provide energy for low-power electronic products.Third,the principle of electromagnetic induction is integrated to convert the energy of the rotating motion of the multifunctional piezoelectric ultrasonic transducer into electric energy.The design makes the multifunctional piezoelectric ultrasonic transducer break through the limitation of single function of current piezoelectric ultrasonic transducer.(2)The finite element solid discrete model of the multifunctional piezoelectric ultrasonic transducer was established and analyzed using the finite element software ANSYS,and the structural parameters of the model were changed to study the influence of different structural size changes on its modal characteristics,harmonic response characteristics and transient characteristics;Based on the sensitivity method,the optimal structure size of the device is optimized,which provides a theoretical basis for the practical design of the multifunctional piezoelectric ultrasonic transducer.(3)Based on the inverse piezoelectric effect of piezoelectric ceramics and Hamilton principle,the mechanical dynamics model of multifunctional piezoelectric ultrasonic transducer was established,and the vibration analysis,friction analysis of contact surface and equivalent conversion analysis of piezoelectric characteristics of the model were carried out.Considering the variation of the mechanical output characteristics of the multifunctional piezoelectric ultrasonic transducer under different conditions and combined with the Runge Kutta algorithm,the simulation curve of the variation of the rotational speed with the prepressure is obtained.Finally,the mechanical properties of the multifunctional piezoelectric ultrasonic transducer are tested to verify the theoretical analysis results.The simulation results show that the maximum no-load speed of the device is 112 r/min,the maximum blocking torque is 1.043N·m,and the maximum output power is 3.34 W under the prepressure of 150 N.The prepressure has great influence on the piezoelectric ultrasonic transducer.Increasing the prepressure will reduce the speed of the piezoelectric ultrasonic transducer,and the lock-in torque will increase with the increase of the prepressure.The maximum efficiency of the piezoelectric ultrasonic transducer is about 17% when the prepressure F is between 200 and400 N.Only when the excitation frequency is very close to the resonant frequency of the piezoelectric ultrasonic transducer,the mechanical properties of the piezoelectric ultrasonic transducer can be optimized.The greater the absolute value of the difference between excitation frequency and resonant frequency,the greater the reduction of rotational speed and torque.(4)Based on the principle of positive piezoelectric effect,the ultrasonic vibration energy acquisition mathematical model of the multifunctional piezoelectric ultrasonic transducer was established,and the acquisition voltage,current and electric power characteristics of the piezoelectric ultrasonic transducer under different excitation conditions of standing wave and traveling wave were studied.Combined with the impedance matching method,the optimal output power and load parameters of the piezoelectric ultrasonic transducer are obtained,which provides a theoretical reference for the subsequent topology circuit design.The results show that under the condition of traveling wave excitation with resonant frequency of35.2k Hz and voltage amplitude of 67 V,the output voltage amplitudes of each sector of PZT and solitary PZT sector are 39 V and 34.4V on average,and the maximum output power reaches 113 m W and 82.4m W,respectively.When the load matching resistance R=6kΩ,the average output voltage of the PZT sector is 18.8V,the output current is 3.1m A,and the output power can reach 60 m W;When the device works at the maximum speed,the output voltage of the collected PZT is 28 V.When the external load matching resistance R is 6kΩ,the output voltage is 13.7V.It is also concluded that the output voltage and power of PZT collected under traveling wave excitation without prepressure are the square sum of the output voltage and power of PZT collected under each phase standing wave excitation.(5)Based on the piezoelectric effect design principle of the multifunctional piezoelectric ultrasonic transducer,the ultrasonic rotation-electromagnetic induction compound energy acquisition is designed to convert the rotating motion of the piezoelectric ultrasonic transducer into electric energy. |
